FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
Power Management System;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND
EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

DESCRIPTION
TECHNICAL 5 FIELD
[0001] The present invention relates to a power management system, and more
particularly to an autonomous operation at the time of a power failure in a microgrid in
which a plurality of distributed power supplies cooperate with one another with an
alternating current, which include an energy creating device (hereinafter also referred to
as an "energy creation device") such as a solar cell that harnesses renewable energy.

BACKGROUND ART
[0002] In recent years, for reducing environmental burdens, a power generation system
that harnesses natural energy, such as a solar cell not emitting carbon dioxide, has come
into widespread use in houses. Furthermore, in order to address power shortage and
the like since the Great East Japan Earthquake, product commercialization has been
underway for a system including an energy storing device (hereinafter also referred to
as an "energy storage device") such as a storage battery, a system utilizing an electric
vehicle as a storage battery, a system formed of a combination of a solar cell (an energy
creation device) and a storage battery (an energy storage device), and the like.
Furthermore, in order to significantly reduce emission of carbon dioxide, the Japanese
government has promoted widespread use of a zero-emission house (hereinafter also
referred to as a "ZEH house" or simply as "ZEH") as a house that is improved in heat
insulation performance, equipped with an energy creation device such as a solar cell
that harnesses renewable energy, and allows zero balance of power generation and
consumption in one year.
[0003] In recent years, a large-scale town development called vacant lot development
has been underway, which utilizes the sites of factories and schools (e.g., vacant lot
development in the Sustainable Smart Town in Fujisawa City, Kanagawa Prefecture,
Kyushu University, etc.). Such developments include the case where a solar cell is
installed in each house. Also, according to the above-mentioned guidelines of the
Japanese government, the future town development is expected to proceed on the
precondition that ZEH houses (each equipped with an energy creation device (a solar
cell and the like) of several kW) are built. Moreover, in Sustainable Smart Town in
Fujisawa City, Kanagawa Prefecture, at occurrence of a power failure, 5 solar cells and
storage batteries installed in a house are used to supply electric power to essential loads (for example, a refrigerator) in the house for 72 hours, so that the life continuity
performance (LCP) can be ensured. However, ensuring the LCP for 72 hours requires
a storage battery of 6 kWh or more that is installed in each consumer house, for
example, when the amount of electric power supplied to each essential load is 2
kWh/day. This increases the cost of storage batteries, which causes a concern that the
cost borne by each consumer (house purchase cost) may increase.
[0004] Moreover, in the case of a large-scale vacant lot development, installation of a
solar cell of 4 kW for each house in a town scale of approximately 300 houses leads to
formation of a mega-solar system. Thus, for stabilization of the distribution system
voltage, distribution system stabilization facilities such as a storage battery and SVC
may be installed in a town as countermeasures. In this case, consumers may also need
to bear part of the costs for introduction of these facilities. Conventionally, when a
power failure occurs, as in Sustainable Smart Town in Fujisawa City, Kanagawa
Prefecture, each consumer is separated at a system interconnection point from a
distribution system, and electric power is supplied to an essential load (for example, a
refrigerator) from the distributed power supply in each consumer house. In this case,
when the storage batteries in each consumer house are used for peak-cut etc., during
daytime and almost no storage power remains, there occur problems that: electric
power cannot be supplied to an essential load though a storage battery is installed; an
expensive storage battery of 6 kWh or more needs to be purchased for ensuring the
LCP for 72 hours as described above; or the like.
[0005] Japanese Patent Laying-Open 2015-126554 (PTL 1) discloses a power
management system configured such that, during an interconnection operation, a
plurality of consumer facilities (hereinafter also referred to as a "town") including a
consumer facility equipped with: a power generation facility harnessing renewable
energy: and a storage battery are connected to a common system power supply. The
power management system in PTL 1 includes: a common power storage device (a town
storage battery) connected to a system power supply; a consumer 5 facility-capable
power management unit that performs a prescribed power management in the power
management system; and a differential power calculation unit. The differential power
calculation unit calculates differential power corresponding to: an excess of charge
power for each storage battery in the power management system; or a shortage of
electric power to be supplied from each storage battery to a load, in the state where the
consumer facility-capable power management unit manages electric power. Then,
charging or discharging of the common power storage device is controlled based on the
calculated differential power, thereby facilitating effective use of the electric power
generated by a power generation device in each of the consumer facilities.

CITATION LIST
PATENT LITERATURE
[0006] PTL 1: Japanese Patent Laying-Open No. 2015-126554
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0007] It has been contemplated that, in a microgrid in which the above-mentioned
distribution system stabilization facilities (a town storage battery, SVC, and the like)
are installed in a town, the distribution system voltage stabilization facility including a
town storage battery and the consumer-side distributed power supply are cooperated
and coordinated with each other so as to stabilize the system voltage during an
interconnection operation and so as to utilize a town storage battery to supply electric
power to each consumer during a power failure, thereby allowing reduction of the
installation capacity of the distribution system stabilization facility and reduction of the
battery capacity in each consumer house.
[0008] Accordingly, the power management system in PTL 1 may also allow an
autonomous operation during a power failure to be performed utilizing the energy
stored in the town storage battery. In the power management system disclosed in PTL
1, an excess or a shortage of electric power in the entire town is calculated based on the result of predicting the electric power generated by an energy creation device such as a solar cell and the result of predicting the electric power consumed 5 by a load in each consumer house. Then, based on the calculation results and the efficiency
characteristics of the storage battery disposed in the town, a storage battery as a target
to be charged and discharged is selected to thereby create an operation plan for
performing efficient charging and discharging.
[0009] However, when the control disclosed in PTL 1 is applied to an autonomous
operation during a power failure, there is a problem that an error occurs in the abovementioned
prediction about the generated electric power or prediction about the
consumed electric power by the load. For example, when the prediction of the electric
power generated by a solar cell is incorrect and excessive electric power exceeding the
prediction is generated, the amount of electric power generated by the solar cell may be
suppressed despite that the storage battery still has a chargeable capacity, or the town
storage battery and the consumer's storage battery may be unnecessarily discharged
despite that excessive electric power still remains.
[0010] Also, the autonomous operation during a power failure requires absorption of an
excess or a shortage of the electric power (power amount) (i.e., "averaging of the total
power generation amount") resulting from an incorrect prediction about the power
generation amount or the power consumption amount in a microgrid. In general, an
excess or a shortage can be absorbed using a town storage battery. However, when
the prediction error exceeds the capacity of the town storage battery, the distribution
system may not be able to be maintained. For example, when the electric power
consumed by a load at nighttime increases significantly exceeding the prediction,
balancing of electric power cannot be ensured, so that the distribution system may not
be able to be maintained.
[0011] Thus, for example, it is conceivable to increase the capacity for the autonomous
operation at occurrence of a power failure by cooperative and coordinative control of a
town storage battery and a consumer-side distributed power supply (a solar cell and the
like) for the purpose of ensuring the above-mentioned LCP for 72 hours.
[0012] Specifically, a community energy management system (CEMS) that manages
the entire town (microgrid) predicts the amount of electric power generated 5 by a solar
cell installed in each consumer and the amount of electric power consumed by a load.
Furthermore, based on these prediction results and the amount of electric power stored
in a storage battery (a town storage battery and a storage battery installed in a
consumer), an operation plan for the town storage battery, the consumer's storage
battery, and the load is created, and CEMS notifies a home energy management system(HEMS) in each consumer about the created operation plan, with the result that the above-mentioned cooperative and coordinative control can be implemented.
[0013] In this case, the cycle of revising the operation plan is shortened to increase the
frequency of prediction correction, thereby suppressing errors in the prediction result,
so that the continuity of the autonomous operation can be improved. On the other
hand, since the CEMS manages 300 consumers, the operation plan is generally created
and transmitted in the cycle of about 30 minutes. It is difficult to shorten this cycle
from the viewpoint of calculation load. Thus, the operation plan is revised only in a
30-minute cycle, which causes a problem, for example, that the electric power
generated by a solar cell is incorrectly predicted, thereby suppressing power generation
despite that excessive electric power actually remains, with the result that unnecessary
electric power is discharged from the town storage battery.
[0014] The present invention has been made to solve the above-described problems.
An object of the present invention is to ensure balancing of electric power in an
autonomous operation during a power failure in a management section (for example, a
microgrid including factories, commercial facilities, leisure facilities or the like)
equipped with a plurality of distributed power supplies including an energy creation
device, without excessively increasing computation load for creating an operation plan
for the plurality of distributed power supplies, and without unnecessarily suppressing
an output from the energy creation device even if an error occurs in the operation plan.
SOLUTION TO PROBLEM
[0015] In an aspect of the present invention, a power management system for a
management section equipped with: a main distributed power supply to supply an
alternating-current (AC) voltage to a first distribution system during 5 a power failure;
and a plurality of distributed power supplies including an energy creation device. The
power management system includes a measuring instrument, a communication unit, an
information collection unit, a power generation prediction unit, a power consumption
prediction unit, an operation plan creation unit, and a transmission management unit.
The measuring instrument measures electric power consumed by a load electrically
connected to each of the distributed power supplies through a second distribution
system that is connected through a transformer to the first distribution system. The
communication unit communicates with the main distributed power supply, each of the
distributed power supplies, and the measuring instrument. The information collection
unit collects, through the communication unit, the consumed electric power that is
measured by the measuring instrument and status information about each of the main
distributed power supply and the distributed power supplies. The power generation
prediction unit predicts electric power generated by the energy creation device in the
distributed power supplies. The power consumption prediction unit predicts the
electric power consumed by the load during a power failure. The operation plan
creation unit creates a first operation plan for controlling the main distributed power
supply and a second operation plan for controlling the distributed power supplies.
The first operation plan and the second operation plan are applied in an autonomous
operation for addressing a power failure, and created based on a power generation
prediction result by the power generation prediction unit, a power consumption
prediction result by the power consumption prediction unit, the status information, and
a power consumption actual result by the measuring instrument that are collected by the
information collection unit. The transmission management unit transmits the first
operation plan to the main distributed power supply through the communication unit in
the autonomous operation, and transmits the second operation plan to each of the
distributed power supplies through the communication unit in the autonomous
operation. In the autonomous operation, the first operation plan is updated in each a
first cycle set to be equal to or greater than an information collection cycle by the
information collection unit, and transmitted to the main distributed 5 power supply, and
the second operation plan is updated in each a second cycle longer than the first cycle
and transmitted to each of the distributed power supplies. The main distributed power
supply includes a first controller. The first controller changes an AC voltage
frequency output from the main distributed power supply to the first distribution system
in accordance with an excess or a shortage of electric power with respect to a power
trade balance that follows the first operation plan in the main distributed power supply.
Each of the distributed power supplies includes a second controller. The second
controller controls an output from each of the distributed power supplies in accordance
with a control target value obtained by adding, to the second operation plan, a
modification value according to an AC voltage frequency of the second distribution
system.
[0016] In another aspect of the present invention, a power management system for a
management section equipped with: a main distributed power supply to supply an AC
voltage to a first distribution system during a power failure; and a plurality of
distributed power supplies including an energy creation device. The power
management system includes an information collection unit, a power generation
prediction unit, a power consumption prediction unit, and an operation plan creation
unit. The information collection unit collects electric power consumed by a load
electrically connected to each of the distributed power supplies through a second
distribution system that is connected to the first distribution system, and status
information about each of the main distributed power supply and the distributed power
supplies. The power generation prediction unit predicts electric power generated by
the energy creation device in the distributed power supplies. The power consumption
prediction unit predicts the electric power consumed by the load during a power failure.
The operation plan creation unit creates a first operation plan for controlling the main
distributed power supply and a second operation plan for controlling the distributed
power supplies. The first operation plan and the second operation plan are applied in
an autonomous operation for addressing a power failure, and created based on a power
generation prediction result by the power generation prediction 5 unit, a power
consumption prediction result by the power consumption prediction unit, the status
information, and a power consumption actual result of the load that are collected by the
information collection unit. In the autonomous operation, the first operation plan is
updated in each a first cycle set to be equal to or greater than an information collection
cycle by the information collection unit, and transmitted to the main distributed power
supply, and the second operation plan is updated in each a second cycle longer than the first cycle and transmitted to each of the distributed power supplies. The main
distributed power supply includes a first controller. The first controller changes an
AC voltage frequency output from the main distributed power supply to the first
distribution system in accordance with an excess or a shortage of electric power with
respect to a power trade balance that follows the first operation plan in the main
distributed power supply. Each of the distributed power supplies includes a second
controller. The second controller controls an output from each of the distributed
power supplies in accordance with a control target value obtained by adding, to the
second operation plan, a modification value according to an AC voltage frequency of
the second distribution system.

ADVANTAGEOUS EFFECTS OF INVENTION
[0017] According to the present invention, in a management section (a microgrid) in
which a plurality of distributed power supplies including an energy creation device are
installed, when electric power generated by the energy creation device changes to
deviate from the second operation plan to thereby disturb a power trade balance in the
management section, the AC voltage frequency (system frequency) shared among a
main distributed power supply and a plurality of distributed power supplies through
first and second distribution systems is changed in accordance with an error (an excess
or a shortage of electric power) from the first operation plan that is created in a shorter
cycle than that of the second operation plan, and thereby, a control target value for each
distributed power supply can be modified without re-creating the second operation plan.
As a result, balancing of electric power can be ensured without excessively increasing
computation load for creating an operation plan for the plurality of 5 distributed power
supplies, and without unnecessarily suppressing an output from the energy creation
device even if an error occurs in the operation plan.

BRIEF DESCRIPTION OF DRAWINGS
[0018] Fig. 1 is a block diagram showing a configuration of a distributed power supply
system disposed in a smart town as an example of a microgrid to which a power
management system according to the present embodiment is applied.
Fig. 2 is a block diagram for further illustrating configurations of various
devices in a consumer house shown in Fig. 1.
Fig. 3 is a block diagram illustrating an operation plan creation function by a
CEMS in the present embodiment.
Fig. 4 is a block diagram illustrating a configuration of an operation plan
creation circuit shown in Fig. 3.
Fig. 5 is a block diagram illustrating a configuration of a first operation plan
creation circuit shown in Fig. 4.
Fig. 6 is a block diagram illustrating a configuration of a consumer operation
plan creation circuit shown in Fig. 4.
Fig. 7 is a block diagram illustrating a configuration of a consumer operation
plan creation unit shown in Fig. 6.
Fig. 8 is a block diagram illustrating a configuration of a second operation plan
creation circuit shown in Fig. 7.
Fig. 9 is a block diagram illustrating configurations of a solar cell power
conversion device and a storage battery power conversion device shown in Fig. 1.
Fig. 10 is a block diagram illustrating a configuration of a first control circuit
that controls a first direct-current (DC)/DC conversion circuit in the solar cell power
conversion device shown in Fig. 9.
Fig. 11 is a block diagram illustrating a configuration of a second control circuit
that controls a first DC/AC conversion circuit in the solar cell power conversion device
shown in Fig. 9.
Fig. 12 is a block diagram illustrating a configuration of a third 5 control circuit
that controls a second DC/DC conversion circuit in the storage battery power
conversion device shown in Fig. 9.
Fig. 13 is a block diagram illustrating a configuration of a fourth control circuit
that controls a second DC/AC conversion circuit in the storage battery power
conversion device shown in Fig. 9.
Fig. 14 is a block diagram illustrating a configuration of a town storage battery
power conversion device shown in Fig. 1.
Fig. 15 is a block diagram illustrating a configuration of a ninth control circuit
that controls a third DC/DC conversion circuit in the town storage battery power
conversion device shown in Fig. 14.
Fig. 16 is a block diagram illustrating a configuration of a tenth control circuit
that controls a third DC/AC conversion circuit in the town storage battery power
conversion device shown in Fig. 14.
Fig. 17 is a conceptual diagram illustrating the operation principle of balancing
control utilizing a drooping characteristic in the power management system according
to the present embodiment.
Fig. 18 is a conceptual diagram for illustrating the drooping characteristic for
calculating differential power in the solar cell power conversion device.
Fig. 19 is a conceptual diagram for illustrating the drooping characteristic for
calculating the differential power in the storage battery power conversion device.
Fig. 20 is a conceptual diagram for illustrating the drooping characteristic for
setting an output frequency of the town storage battery power conversion device.
Fig. 21 is a conceptual graph showing an example of an operation plan created
in a 30-minute cycle.
Fig. 22 is a bar graph showing an example of an actual measurement result in
the first 5 minutes in an operation performed based on the operation plan created in a
-minute cycle.
Fig. 23 is a conceptual diagram illustrating an operation image for 30 minutes
according to the operation plan 5 by the CEMS.
Fig. 24 is the first flowchart illustrating a series of processes performed by the
CEMS at occurrence of a power failure.
Fig. 25 is the second flowchart illustrating a series of processes performed by
the CEMS at occurrence of a power failure.
Fig. 26 is a diagram of an operation sequence among various devices during a
power failure in a power system according to the present embodiment.
Fig. 27 is a flowchart illustrating details of a process in a step of creating the
operation plan in Fig. 26.
Fig. 28 is a conceptual diagram for illustrating a target SOC for a length of 24
hours for a town storage battery in the power system according to the present
embodiment.
Fig. 29 is a graph showing an example of a prediction result of an excessive
power amount at each time that occurs in a smart town.
Fig. 30 is a graph showing an example of a plan for charge/discharge power of
the town storage battery.
Fig. 31 is a graph showing an example of SOC transition in accordance with the
operation plan for the town storage battery.
Fig. 32 is a graph showing an example of a plan for charge/discharge power of a
storage battery in a consumer.
Fig. 33 is a graph showing an example of a calculation result about SOC
transition in accordance with the operation plan for the storage battery in the consumer.
Fig. 34 is a flowchart illustrating details of a process in a step of creating an
operation plan for the town storage battery in Fig. 27.
Fig. 35 is a flowchart illustrating details of a process in a step of estimating a
power generation suppression amount for a solar cell in Fig. 34.
Fig. 36 is a flowchart illustrating details of a process in a step of changing the
operation plan for the town storage battery in Fig. 34.

DESCRIPTION OF EMBODIMENTS
[0019] The embodiments of the present invention will be hereinafter described 5 in detail with reference to the accompanying drawings. In the following description, the same or corresponding portions will be designated by the same reference characters, and description thereof will not be basically repeated.
[0020] (System Configuration)
Fig. 1 is a block diagram showing a configuration of a distributed power supply
system disposed in a smart town as an example of a microgrid to which a power
management system according to an embodiment of the present invention is applied.
Specifically, the smart town corresponds to one example of a "management section".
[0021] Referring to Fig. 1, the distributed power supply system is disposed in a smart
town formed of a collection of a plurality of sections (for example, about 30 sections).
Each of the sections forming such a smart town is constituted of a plurality of (for
example, about ten) consumers connected to a common pole-mounted transformer 9.
Fig. 1 shows sections 19Q, 19R and 19Z, and pole-mounted transformers 9Q, 9R and
9Z that correspond to sections 19Q, 19R and 19Z, respectively, but any number of
sections may be provided. Furthermore, a consumer a and a consumer b are shown in
section 19Q, but any number of consumers may exist in one section.
[0022] Each consumer house 18 includes a solar cell 1, a solar cell power conversion
device 2, a storage battery 3, a storage battery power conversion device 4, a load 5 in a
consumer house, a power switchboard 6, a HEMS 7, a smart meter 8, a consumer
premises distribution system 10, a consumer premises communication network 11, and
a signal line 12. Consumer premises communication network 11 connects HEMS 7 to
devices installed in each house. Through signal line 12, consumed power and the like
of each device measured by power switchboard 6 are transmitted to HEMS 7.
[0023] Fig. 1 shows the configurations of consumer houses 18a and 18b of respective
consumers "a" and "b" in section 19Q with suffixes a and b added to reference
numerals of the respective elements, whereas the elements are denoted by reference
numerals without suffixes a and b when the description is common to the consumers
since the configurations of the systems in the consumer houses are the same.
Similarly, the pole-mounted transformers will be denoted simply 5 as a pole-mounted
transformer 9 without suffixes Q, R and Z when the description is common to the
sections.
[0024] Furthermore, a smart town shared among the consumers and the sections has a
configuration including: a distribution system 17 connected to a substation 24; a
distribution system 16 connected to the pole-mounted transformer's primary side
between pole-mounted transformers 9; a distribution system 14 on the pole-mounted
transformer's secondary side between pole-mounted transformer 9 and each consumer;
an outside premises communication network 13; a CEMS 15; a town storage battery
15 [0025] CEMS 15 manages demand and supply of electric power in a city section
constituted of sections 19Q to 19Z. Outside premises communication network 13
connects communication between HEMS 7 of each consumer and CEMS 15. Cloud
23 distributes weather forecast information and the like. Through outside premises
communication network 13, CEMS 15 can acquire the information distributed from
cloud 23. Town storage battery power conversion device 21 performs DC/AC power
conversion between town storage battery 20 and distribution system 16. Switch 22 is
provided between distribution system 16 and distribution system 17 that is connected to
substation 24. Switch 22 can provide electrical disconnection between substation 24
and distribution systems 14, 16 in a smart town.
[0026] The following is an explanation about the present embodiment in the case
where each consumer house 18 is configured as a ZEH house equipped with solar cell 1 (having a capacity of about 4 to 6 (kW)), and a mega-solar system is formed in the
entire smart town. In other words, in the present embodiment, an explanation will be
hereinafter given with regard to the configuration in which solar cell 1 and storage
battery 3 are installed as "distributed power supplies" in each of consumer houses 18.
Solar cell 1 corresponds to one example of an "energy creation device". Storage
battery 3 corresponds to one example of an "energy storage device".
[0027] Moreover, storage battery 3 is illustrated to have a configuration employing one
fixed-type battery, but an "energy storage device" can also be formed 5 in cooperation
with two or more storage batteries or other distributed power supply devices. In
particular, an on-vehicle storage battery in an electric vehicle (EV), a plug-in hybrid
electric vehicle (PHEV), or a fuel cell vehicle (FCV) can also be used. Furthermore,
storage battery 3 can also be formed by combining a fixed-type storage battery with an
on-vehicle storage battery.
[0028] Similarly, other energy creation devices (for example, a fuel cell, and a wind
power generation facility) may be disposed in place of solar cell 1. Alternatively, in
addition to solar cell 1, other energy creation devices may further be disposed.
Moreover, the present embodiment is described with regard to an example of a
configuration in which both solar cell 1 (an energy creation device) and a storage
battery (an energy storage device) are disposed in each consumer house 18, but some of consumer houses 18 may include only one of solar cell 1 and storage battery 3.
[0029] Fig. 2 shows a block diagram for further illustrating configurations of various
devices in consumer house 18 shown in Fig. 1.
[0030] Referring to Fig. 2, solar cell 1 and solar cell power conversion device 2
constitute a distributed power supply by an energy creation device while storage battery
3 and storage battery power conversion device 4 constitute a distributed power supply
by an energy storage device. As described above, the power supply system in each
consumer house may be provided with only one of a distributed power supply by an
energy creation device and a distributed power supply by an energy storage device.
[0031] Load 5 includes a heat storage device 51 such as Eco Cute (registered
trademark), an air conditioner 52, a refrigerator 53, a lighting device 54, and an IH
cooking heater 55, for example. Load 5 operates with electric power supplied from
consumer premises distribution system 10. Power switchboard 6 is equipped inside
with a power measurement circuit 61 for measuring consumed electric power per
breaker. The measured value by power measurement circuit 61 is transmitted to
HEMS 7 through signal line 12. HEMS 7 is capable of transmitting and receiving
data to and from each device of load 5 and smart meter 8 through consumer premises
communication 5 network 11.
[0032] For each consumer house 18, electric power is supplied from pole-mounted
transformer 9 through smart meter 8 to consumer premises distribution system 10.
Furthermore, CEMS 15 is connected to HEMS 7 through outside premises
communication network 13. HEMS 7 is capable of transmitting and receiving data to
and from CEMS 15 through outside premises communication network 13.
[0033] CEMS 15 periodically creates an operation plan for the distributed power
supply system described with reference to Figs. 1 and 2. It should be noted that
creation of the operation plan in the present embodiment means both: newly creating an
operation plan at a certain time; and re-creating an operation plan by modifying or
correcting the operation plan at the time when it has already been created.
[0034] Fig. 3 is a block diagram illustrating an operation plan creation function by
CEMS 15 in the present embodiment.
[0035] Referring to Fig. 3, CEMS 15 includes a communication circuit 151, an
information collection circuit 152, a data transmission management circuit 153, a data
reception management circuit 154, a distributed power supply status management
circuit 155, a power generation actual result management circuit 156, a power
generation prediction circuit 157, a power consumption prediction circuit 158, a power
consumption actual result management circuit 159, an operation plan creation circuit
160, and an operation plan creation management circuit 161.
[0036] Via outside premises communication network 13, communication circuit 151
transmits and receives information through communication among HEMS 7 installed in
each consumer house 18, town storage battery power conversion device 21, and cloud .
[0037] Information collection circuit 152 collects and manages the power consumption amount of each consumer house 18, the status information about solar cell 1 and
storage battery 3, the status information about town storage battery 20, and the weather
forecast information obtained through cloud 23, each of which has been obtained
through communication circuit 151.
[0038] Through communication circuit 151, data transmission management 5 circuit 153
manages transmission of the operation plan created by CEMS 15, transmission of a
request for transmission of a power consumption amount and the like measured in each
consumer house 18, or the like. Data reception management circuit 154 manages the
data received through communication circuit 151.
[0039] Distributed power supply status management circuit 155 manages the status
information about the distributed power supply that is output from information
collection circuit 152 (the amount of electric power generated by solar cell 1 that has
been received from solar cell power conversion device 2 in consumer house 18, and the
control mode of solar cell 1 (which will be described later in detail)). Furthermore,
= distributed power supply status management circuit 155 manages the charge/discharge
power amount, the state of charge (SOC) and the state of health (SOH) of storage
battery 3, which are output from storage battery power conversion device 4.
Distributed power supply status management circuit 155 also manages the
charge/discharge power amount, the SOC and the SOH of town storage battery 20,
which are output from town storage battery power conversion device 21.
[0040] Power generation actual result management circuit 156 manages the amount of
electric power generated by solar cell 1 in each consumer house 18, which is output
from information collection circuit 152. Based on the power generation amount actual
result value of which each consumer house 18 notifies power generation actual result
management circuit 156, this power generation actual result management circuit 156
constructs a database at each date, at each time (for example, in each 30 minutes), and
for each actual result of weathers.
[0041] Power generation prediction circuit 157 predicts the electric power generated by
solar cell 1 in each consumer house 18 based on the weather forecast information
output from information collection circuit 152 and the power generation amount actual
result database constructed by power generation actual result management circuit 156.
[0042] Power consumption actual result management circuit 159 manages the power
consumption actual result value of load 5 in each consumer house 18 that is output
from information collection circuit 152. In an interconnection operation, 5 based on the
power consumption actual result value of which each consumer house 18 notifies
power consumption actual result management circuit 159, this power consumption
actual result management circuit 159 constructs a database in each month, on the same day each week, at each time (for example, in each 30 minutes), and for each actual result of weathers (including the actual result of outside temperatures).
[0043] Power consumption prediction circuit 158 predicts the electric power consumed
by load 5 in each consumer house 18 based on the weather forecast information output
from information collection circuit 152 (including the prediction information about
outside temperatures), and the power consumption actual result database constructed by power consumption actual result management circuit 159.
[0044] Based on the data output from distributed power supply status management
circuit 155, power generation actual result management circuit 156, power generation
prediction circuit 157, power consumption prediction circuit 158, and power
consumption actual result management circuit 159, operation plan creation circuit 160
generates a charge/discharge plan for town storage battery 20 (a 5-minute cycle and a
30-minute cycle), a drooping characteristic of town storage battery power conversion
device 21, trading electric power at a system interconnection point in each consumer
house 18, a drooping characteristic for solar cell power conversion device 2, and a
drooping characteristic for storage battery power conversion device 4. Operation plan
creation management circuit 161 manages the operation of the entire operation plan
creation function of CEMS 15.
[0045] In this case, the drooping characteristics used in town storage battery power
conversion device 21 and also used in solar cell power conversion device 2 and storage
battery power conversion device 4 in each consumer house 18 mean the characteristics
by which the system frequency increases (when electric power is excessive) or
decreases (when electric power is in shortage) in accordance with an excess or a
shortage of the electric power consumed by the load with respect to the electric power
generated by a power generator, which is a phenomenon generally occurring in a power
system. In the present embodiment, the entire power balance within 5 a microgrid is
shared among the conversion devices by the drooping characteristics, as will be
apparent in the description below.
[0046] Fig. 4 is a block diagram illustrating a configuration of operation plan creation
circuit 160 shown in Fig. 3.
Referring to Fig. 4, operation plan creation circuit 160 includes a consumer
operation plan creation circuit 1651 and a first operation plan creation circuit 1601.
[0047] Consumer operation plan creation circuit 1651 generates trading electric power
at the system interconnection point in each consumer house 18, a drooping
characteristic for solar cell power conversion device 2, and a drooping characteristic for
storage battery power conversion device 4. First operation plan creation circuit 1601
generates a charge/discharge plan for town storage battery 20 (in a 5-minute cycle and a 30-minute cycle), and a drooping characteristic of town storage battery power
conversion device 21.
[0048] Fig. 5 is a block diagram illustrating a configuration of first operation plan
creation circuit 1601 shown in Fig. 4.
[0049] Referring to Fig. 5, first operation plan creation circuit 1601 includes an
excessive power prediction summation circuit 1605, an output suppression power
summation circuit 1606, a town storage battery charge/discharge power decision circuit
1607, a town storage battery drooping characteristic generation circuit 1608, a town
storage battery operation plan creation circuit 1609, and a consumer system
interconnection point power generation circuit 1610.
[0050] Excessive power prediction summation circuit 1605 sums the prediction results
about the excessive electric power in each consumer house 18 that is output from an
excessive power prediction circuit 1655 (described later) in consumer operation plan
creation circuit 1651. Output suppression power summation circuit 1606 sums the
output suppression power estimation values for solar cells 1 in respective consumer
houses 18 that are output from a solar cell output suppression determination circuit
1656 (described later) in consumer operation plan creation circuit 1651. Town storage
battery charge/discharge power decision circuit 1607 decides the 5 charge/discharge
power from town storage battery 20 based on the outputs from excessive power
prediction summation circuit 1605 and output suppression power summation circuit
1606. Town storage battery drooping characteristic generation circuit 1608 generates
a drooping characteristic of town storage battery 20 based on the outputs from
excessive power prediction summation circuit 1605, output suppression power
summation circuit 1606, and town storage battery charge/discharge power decision
circuit 1607.
[0051] According to a timing signal output from operation plan creation management
circuit 161, town storage battery operation plan creation circuit 1609 creates an
operation plan for town storage battery 20 based on the information from: town storage
battery charge/discharge power decision circuit 1607 and a second operation plan
creation circuit 1657 (described later) in consumer operation plan creation circuit 1651.
In the present embodiment, operation plan creation management circuit 161 outputs
two types of timing signals including a timing signal in a 5-minute cycle, and a timing
signal in a 30-minute cycle.
[0052] Consumer system interconnection point power generation circuit 1610
generates a trading power target value at the system interconnection point in each
consumer house 18 (consumer premises distribution system 10 in Figs. 1 and 2) based
on the outputs from excessive power prediction circuit 1655, solar cell output
suppression determination circuit 1656, and town storage battery operation plan
creation circuit 1609. A positive value of the trading power target value shows the
power selling direction in which electric power is output from a distributed power
supply to consumer premises distribution system 10. A negative value of the trading
power target value shows the power buying direction opposite to the power selling
direction.
[0053] Fig. 6 is a block diagram illustrating a configuration of consumer operation plan
creation circuit 1651 shown in Fig. 4.
[0054] Referring to Fig. 6, consumer operation plan creation circuit 1651 includes a
consumer operation plan creation unit 1652 provided in each consumer 5 house 18. Fig.
6 illustrates consumer operation plan creation units 1652a and 1652b for creating
operation plans for consumer houses 18a and 18b, respectively, in Fig. 1. In fact, the
same number of consumer operation plan creation units 1652 as consumers managed
by CEMS 15 are mounted in consumer operation plan creation circuit 1651.
[0055] Fig. 7 is a block diagram illustrating each configuration of consumer operation
plan creation unit 1652 shown in Fig. 6. Consumer operation plan creation unit 1652
shown in Fig. 6 is assumed to create an operation plan for a consumer house 18x
among a plurality of consumer houses 18.
[0056] Referring to Fig. 7, consumer operation plan creation unit 1652 includes
excessive power prediction circuit 1655, solar cell output suppression determination
circuit 1656, and second operation plan creation circuit 1657.
[0057] Excessive power prediction circuit 1655 predicts excessive electric power in
consumer house 18x from power generation prediction circuit 157 and power
consumption prediction circuit 158. Solar cell output suppression determination
circuit 1656 determines whether solar cell 1 suppresses output or not, based on the
power generation amount prediction result about solar cell 1 installed in consumer
house 18x, the power consumption prediction result, the power generation amount
actual result, the power consumption actual result, and the status information from solar
cell power conversion device 2 and storage battery power conversion device 4 in
consumer house 18x. When solar cell output suppression determination circuit 1656
determines that output is suppressed, it further predicts a power value obtained as a
result of output suppression.
[0058] In response to reception of the timing signal output from operation plan creation
management circuit 161 (assuming that the timing signal is output in a 30-minute
cycle), second operation plan creation circuit 1657 generates a trading power target
value and a drooping characteristic at a system interconnection point in consumer
house 18x, based on the outputs from excessive power prediction circuit 1655, solar
cell output suppression determination circuit 1656, and consumer system
interconnection point power generation circuit 1610, and the status 5 information from
storage battery power conversion device 4. As a result, by consumer operation plan
creation circuit 1651 in Fig. 6, the trading power target value and the drooping
characteristic at a system interconnection point are generated separately for each
consumer house 18.
[0059] Fig. 8 is a block diagram illustrating a configuration of second operation plan
creation circuit 1657 shown in Fig. 7. Consumer operation plan creation unit 1652
shown in Fig. 7 is also intended to create an operation plan for consumer house 18x
among the plurality of consumer houses 18.
[0060] Referring to Fig. 8, second operation plan creation circuit 1657 includes a
consumer distributed power supply drooping characteristic generation circuit 1661, and
an operation plan correction circuit 1662.
[0061] In response to reception of the timing signal output from operation plan creation
management circuit 161 (assuming that the timing signal is output in a 30-minute
cycle), operation plan correction circuit 1662 corrects the operation plan based on the
outputs from distributed power supply status management circuit 155, consumer system
interconnection point power generation circuit 1610, and excessive power prediction
circuit 1655. In response to reception of the timing signal output from operation plan
creation management circuit 161 (assuming that the timing signal is output in a 30-
minute cycle), consumer distributed power supply drooping characteristic generation
circuit 1661 generates a drooping characteristic in consumer house 18x based on the
outputs from excessive power prediction circuit 1655, distributed power supply status
management circuit 155, and operation plan correction circuit 1662.
[0062] Then, referring to Figs. 9 to 16, the configurations of solar cell power
conversion device 2, storage battery power conversion device 4, and town storage
battery power conversion device 21 in Fig. 1 will be described in detail.
[0063] Fig. 9 is a block diagram illustrating configurations of solar cell power
conversion device 2 and storage battery power conversion device 4.
[0064] Referring to Fig. 9, solar cell power conversion device 2 includes a voltmeter
201, an ammeter 202, a first DC/DC conversion circuit 203, a first control 5 circuit 204, a
DC bus 205, a voltmeter 206, an ammeter 207, a first DC/AC conversion circuit 208, a
second control circuit 209, a voltmeter 210, an ammeter 211, and a communication
interface circuit 212.
[0065] Voltmeter 201 measures the voltage (DC) output from solar cell 1. Ammeter
202 measures the current (DC) output from solar cell 1. A first DC/DC conversion
circuit 203 converts the DC power of the first DC voltage output from solar cell 1 into
DC power of the second DC voltage. First control circuit 204 controls first DC/DC
conversion circuit 203. Through DC bus 205, the second DC voltage output from first
DC/DC conversion circuit 203 is supplied to first DC/AC conversion circuit 208.
Voltmeter 206 measures the voltage on DC bus 205. Ammeter 207 measures the
current (DC) output from first DC/DC conversion circuit 203.
[0066] First DC/AC conversion circuit 208 converts the DC power output from first
DC/DC conversion circuit 203 into AC power. Second control circuit 209 controls
first DC/AC conversion circuit 208. Voltmeter 210 measures the voltage (AC) output
from first DC/AC conversion circuit 208. Ammeter 211 measures the current (AC)
output from first DC/AC conversion circuit 208. Communication interface circuit 212
establishes communication between solar cell power conversion device 2 (second
control circuit 209) and HEMS 7.
[0067] Storage battery power conversion device 4 includes a voltmeter 401, an
ammeter 402, a second DC/DC conversion circuit 403, a third control circuit 404, a DC
bus 405, a voltmeter 406, an ammeter 407, a second DC/AC conversion circuit 408, a
fourth control circuit 409, a voltmeter 410, an ammeter 411, and a communication
interface circuit 412.
[0068] Voltmeter 401 measures the voltage (DC) output from storage battery 3.
Ammeter 402 measures the current (DC) output from storage battery 3. Second
DC/DC conversion circuit converts the DC power of the third DC voltage output from
storage battery 3 into DC power of the fourth DC voltage. Third control circuit 404
controls second DC/DC conversion circuit 403. Through DC bus 405, the fourth DC
voltage output from second DC/DC conversion circuit 403 is 5 supplied to second
DC/AC conversion circuit 408.
[0069] Voltmeter 406 measures the voltage on DC bus 405. Ammeter 407 measures
the direct current output from second DC/DC conversion circuit 403. Second DC/AC
conversion circuit 408 converts the DC power output from second DC/DC conversion
circuit 403 into AC power. Fourth control circuit 409 controls second DC/AC
conversion circuit 408. Voltmeter 410 measures the voltage (AC) output from second
DC/AC conversion circuit 408. Ammeter 411 measures the current (AC) output from
second DC/AC conversion circuit 408. Communication interface circuit 412
establishes communication between storage battery power conversion device 4 (fourth
control circuit 409) and HEMS 7.
[0070] First DC/DC conversion circuit 203, second DC/DC conversion circuit 403,
first DC/AC conversion circuit 208, and second DC/AC conversion circuit 408 can be
formed in the configuration of a known DC/DC converter and inverter as appropriate.
Moreover, when a lithium-ion battery is used as storage battery 3, a battery
management unit (BMU) incorporated on the battery side generally manages the power
storage amount, the possibility of charge and discharge, the maximum charge current
during charging, and the like, and notifies third control circuit 404 about the
management results. However, for simplifying the description, the present
embodiment will be described assuming that third control circuit 404 and ninth control
25 circuit 604 collectively manage the power storage amount, the possibility of charge and
discharge, the maximum charge current during charging, and the like.
[0071] Fig. 10 is a block diagram illustrating the configuration of first control circuit
204 (Fig. 9) that controls first DC/DC conversion circuit 203 (Fig. 9) in solar cell
power conversion device 2.
- 25 -
[0072] Referring to Fig. 10, first control circuit 204 includes a maximum power point
tracking (MPPT) control circuit 2041, a voltage control circuit 2042, a switching circuit
2043, and a fifth control circuit 2044. Based on the measured values by voltmeter 201
and ammeter 202, MPPT control circuit 2041 searches for the maximum power point of
solar cell 1 in order to extract, to the extent possible, the electric 5 power generated by
solar cell 1 for the so-called maximum power point tracking control. Specifically,
MPPT control circuit 2041 generates a control command value for the first DC/DC
conversion circuit for controlling the DC voltage measured by voltmeter 201 to be set
at a voltage corresponding to the above-mentioned maximum power point.
10 [0073] Based on the measured value by voltmeter 206, voltage control circuit 2042
generates a control command value for first DC/DC conversion circuit 203 for
maintaining the DC voltage (the second DC voltage) on DC bus 205 at a predetermined
target voltage (for example, 350V).
[0074] Fifth control circuit 2044 outputs a control parameter, a control target value and
15 the like to MPPT control circuit 2041 and voltage control circuit 2042, and also
manages the power generation state of solar cell 1, and the like. Fifth control circuit
2044 further outputs a control signal for switching circuit 2043.
[0075] According to the control signal from fifth control circuit 2044, switching circuit
2043 selectively outputs one of the outputs from MPPT control circuit 2041 and
20 voltage control circuit 2042 as a control command value for first DC/DC conversion
circuit 203.
[0076] As described below, first DC/DC conversion circuit 203 is controlled in an
MPPT mode or a voltage control mode. In the MPPT mode, switching circuit 2043 is
controlled to output the control command value generated by MPPT control circuit
25 2041. In the voltage control mode, switching circuit 2043 is controlled to output the
control command value generated by voltage control circuit 2042.
[0077] Fig. 11 is a block diagram illustrating the configuration of second control circuit
209 (Fig. 9) that controls the first DC/AC conversion circuit (Fig. 9) in solar cell power
conversion device 2.
- 26 -
[0078] Referring to Fig. 11, second control circuit 209 includes a phase detection
circuit 2091, a frequency detection circuit 2092, a drooping characteristic table
generation circuit 2093, and a sixth control circuit 2094.
[0079] Phase detection circuit 2091 detects the voltage phase in consumer premises
distribution system 10 from the AC voltage waveform measured 5 by voltmeter 210.
Frequency detection circuit 2092 detects the frequency of the AC voltage in consumer
premises distribution system 10 from the cycle at a zero cross point of the AC voltage
waveform detected in phase detection circuit 2091.
[0080] Drooping characteristic table generation circuit 2093 develops the drooping
10 characteristic information received through communication interface circuit 212 into
table data. Furthermore, according to the developed drooping characteristic table,
drooping characteristic table generation circuit 2093 can detect an excess or a shortage
of electric power in distribution system 14 (i.e., the power balance in a microgrid)
based on the AC voltage frequency information detected in frequency detection circuit
15 2092. Based on the detection results, drooping characteristic table generation circuit
2093 notifies sixth control circuit 2094 about the excess or the shortage of the electric
power generated by solar cell 1.
[0081] Based on the information about the excess/shortage of the electric power
generated by solar cell 1 obtained from drooping characteristic table generation circuit
20 2093, sixth control circuit 2094 notifies fifth control circuit 2044 about the control
target for the electric power generated by solar cell 1. Furthermore, sixth control
circuit 2094 generates a control command value for controlling first DC/AC conversion
circuit 208.
[0082] Fig. 12 is a block diagram illustrating a configuration of third control circuit
25 404 (Fig. 9) that controls second DC/DC conversion circuit 403 (Fig. 9) in storage
battery power conversion device 4.
[0083] Referring to Fig. 12, third control circuit 404 includes a charge control circuit
4041, a discharge control circuit 4042, a switching circuit 4043, and a seventh control
circuit 4044.
- 27 -
[0084] Charge control circuit 4041 generates a control command value for second
DC/DC conversion circuit 403 that is used when charging of storage battery 3 is
controlled. Discharge control circuit 4042 generates a control command value for
second DC/DC conversion circuit 403 that is used when discharging of storage battery
3 is controlled. Seventh control circuit 4044 outputs a control parameter, 5 a control
target value and the like to charge control circuit 4041 and discharge control circuit
4042, and also, manages the charge amount, the charge current, the discharge power
amount and the like of storage battery 3. Seventh control circuit 4044 further outputs
a control signal of switching circuit 4043.
10 [0085] According to the control signal from seventh control circuit 4044, switching
circuit 4043 selectively outputs one of the outputs from charge control circuit 4041 and
discharge control circuit 4042 as a control command value for second DC/DC
conversion circuit 403.
[0086] Switching circuit 4043 is controlled to output the control command value
15 generated by charge control circuit 4041 when receiving an instruction to charge
storage battery 3, and to output the control command value generated by discharge
control circuit 4042 when receiving an instruction to discharge storage battery 3.
[0087] Fig. 13 is a block diagram illustrating the configuration of fourth control circuit
409 (Fig. 9) that controls second DC/AC conversion circuit 403 (Fig. 9) in storage
20 battery power conversion device 4.
[0088] Referring to Fig. 13, fourth control circuit 409 includes a phase detection circuit
4091, a frequency detection circuit 4092, a drooping characteristic table generation
circuit 4093, and an eighth control circuit 4094.
[0089] Phase detection circuit 4091 detects the voltage phase in distribution system 10
25 from the AC voltage waveform measured by voltmeter 410. Frequency detection
circuit 4092 detects the frequency of the AC voltage in distribution system 10 from the
cycle at a zero cross point of the AC voltage waveform detected in phase detection
circuit 4091.
[0090] Drooping characteristic table generation circuit 4093 develops the drooping
- 28 -
characteristic information received through communication interface circuit 412 into
table data. Furthermore, according to the developed drooping characteristic table,
drooping characteristic table generation circuit 4093 detects an excess or a shortage of
electric power in distribution system 14 (i.e., the power balance in a microgrid) based
on the AC voltage frequency information detected in frequency detection 5 circuit 4092.
Based on the detection results, drooping characteristic table generation circuit 4093
notifies eighth control circuit 4094 about the excess or the shortage of the
charge/discharge power of storage battery 3.
[0091] Based on the information about the excess/shortage of the charge/discharge
10 power of storage battery 3 obtained from drooping characteristic table generation
circuit 4093, eighth control circuit 4094 notifies seventh control circuit 4044 about the
control target for the charge/discharge power of storage battery 3. Furthermore,
eighth control circuit 4094 generates a control command value for controlling second
DC/AC conversion circuit 408.
15 [0092] Fig. 14 is a block diagram illustrating the configuration of town storage battery
power conversion device 21 shown in Fig. 1.
[0093] Referring to Fig. 14, town storage battery power conversion device 21 includes
a voltmeter 601, an ammeter 602, a third DC/DC conversion circuit 603, a ninth control
circuit 604, a DC bus 605, a voltmeter 606, an ammeter 607, a third DC/AC conversion
20 circuit 608, a tenth control circuit 609, a voltmeter 610, an ammeter 611, and a
communication interface circuit 612.
[0094] Voltmeter 601 measures the voltage (DC) output from town storage battery 20.
Ammeter 602 measures the current (DC) output from town storage battery 20. The
current value by ammeter 602 is positive during discharging of town storage battery 20
25 and is negative during charging of town storage battery 20. Third DC/DC conversion
circuit 603 converts the fifth DC voltage output from town storage battery 20 into a
sixth DC voltage and outputs the converted sixth DC voltage to DC bus 605. Ninth
control circuit 604 controls third DC/DC conversion circuit 603. Through DC bus
605, the sixth DC voltage output from third DC/DC conversion circuit 603 is supplied
- 29 -
to third DC/AC conversion circuit 608.
[0095] Voltmeter 606 measures the voltage on DC bus 605. Ammeter 607 measures
the direct current output from third DC/DC conversion circuit 603. Third DC/AC
conversion circuit 608 converts the DC power output from third DC/DC conversion
circuit 603 into AC power. Tenth control circuit 609 controls 5 third DC/AC
conversion circuit 608.
[0096] Voltmeter 610 measures the voltage (AC) output from third DC/AC conversion
circuit 608. Ammeter 611 measures the current (AC) output from third DC/AC
conversion circuit 608. Communication interface circuit 612 establishes
communication between town storage battery power conversion device 21 (tenth
control circuit 609) and CEMS 15. In addition, third DC/DC conversion circuit 603
and third DC/AC conversion circuit 603 can also be formed in the configuration of a
known DC/DC converter and inverter as appropriate.
[0097] Fig. 15 is a block diagram illustrating the configuration of ninth control circuit
604 (Fig. 14) that controls third DC/DC conversion circuit 603 (Fig. 14) in town
storage battery power conversion device 21.
[0098] Referring to Fig. 15, ninth control circuit 604 includes a charge control circuit
6041, a discharge control circuit 6042, a switching circuit 6043, and an eleventh control
circuit 6044.
[0099] Charge control circuit 6041 calculates a command value for third DC/DC
conversion circuit 603 that is used for controlling charging of town storage battery 20.
Discharge control circuit 6042 calculates a command value for third DC/DC conversion
circuit 603 that is used for controlling discharging from town storage battery 20.
[0100] Eleventh control circuit 6044 outputs the control parameter, the control target
value and the like to charge control circuit 6041 and discharge control circuit 6042, and
also manages the charge amount, the charge current, the discharge power amount and
the like of town storage battery 20. Eleventh control circuit 6044 further outputs a
control signal for switching circuit 6043.
[0101] According to the control signal from eleventh control circuit 6044, switching
circuit 6043 selectively outputs one of the outputs from charge control circuit 6041 and
discharge control circuit 6042 as a control command value for third DC/DC conversion
circuit 603. Switching circuit 6043 is controlled to output the control command value
generated by charge control circuit 6041 when receiving an instruction to charge town
storage battery 20, and controlled to output the control command 5 value generated by
discharge control circuit 6042 when receiving an instruction to discharge town storage
battery 20.
[0102] Fig. 16 is a block diagram illustrating the configuration of tenth control circuit
609 (Fig. 14) that controls third DC/AC conversion circuit 608 (Fig. 14) in town
10 storage battery power conversion device 21.
[0103] Referring to Fig. 16, tenth control circuit 609 includes a sinusoidal wave
generation circuit 6091, a drooping characteristic table generation circuit 6092, and a
twelfth control circuit 6094.
[0104] Drooping characteristic table generation circuit 6092 develops the drooping
characteristic information received through communication interface circuit 612 into
table data. Furthermore, according to the developed drooping characteristic table,
drooping characteristic table generation circuit 6092 calculates a voltage frequency to
be output to distribution system 16, based on the information about the excess/shortage
of the electric power in distribution system 16 that is output from twelfth control circuit
6094. The calculated voltage frequency is output to sinusoidal wave generation
circuit 6091.
[0105] Sinusoidal wave generation circuit 6091 generates a sinusoidal wave as a target
value of the AC voltage that is to be output from town storage battery power
conversion device 21 to distribution system 16. The sinusoidal wave is generated so
as to have a voltage frequency that is transmitted from drooping characteristic table
generation circuit 6092. The voltage frequency is set to fall within a range of f
(Hz) with respect to a predetermined center frequency fc. For example, fc = 60 (Hz)
and the voltage frequency is set to be variable within a range of 59.8 to 60.2 (Hz).
[0106] Twelfth control circuit 6094 generates information about the excess/shortage of
the electric power in distribution system 16 in accordance with comparison between:
the actual charge/discharge power of town storage battery 20 based on the detection
values of voltmeter 610 and ammeter 611; and the charge/discharge power target value
for town storage battery 20. The generated information about the excess/shortage of
electric power is transmitted to drooping characteristic table generation 5 circuit 6092.
Furthermore, twelfth control circuit 6094 generates a control command value used for
controlling third DC/AC conversion circuit 608 in accordance with the sinusoidal wave
output from sinusoidal wave generation circuit 6091. For example, third DC/AC
conversion circuit 608 is controlled by pulse width modulation (PWM) control at a
switching frequency of about 20 kHz so as to output an AC voltage corresponding to
the above-mentioned voltage frequency.
[0107] (Autonomous Operation during Power Failure)
The following is an explanation about the autonomous operation during a power
failure in a smart town shown in Figs. 1 to 16.
[0108] Again referring to Fig. 1, at occurrence of a power failure, CEMS 15 outputs an interruption command to switch 22 to thereby electrically disconnect distribution
system 16 from substation 24. When the entire smart town is thereby disconnected
from substation 24, an autonomous operation for continuing supply of electric power in
the smart town is performed using town storage battery power conversion device 21 as
an AC voltage source. In the present embodiment, the autonomous operation is
assumed to be performed for the purpose of ensuring the LCP for 72 hours.
[0109] In the autonomous operation, in order to implement the LCP for 72 hours,
CEMS 15 creates an operation plan basically for the purpose of ensuring the electric
power (for example, about 2 [kWh]) for a length of 72 hours supplied to an "essential
load" such as a refrigerator 53 and a night lighting device 54. The operation plan
includes a plan for trading electric power at a system interconnection point in each
consumer house 18, and a plan for charging/discharging of town storage battery 20.
[0110] When HEMS 7 detects occurrence of a power failure in each consumer house
18, HEMS 7 instructs load 5 in each house to turn off all of the power supplies. For
example, HEMS 7 instructs power switchboard 6 to automatically shut down all of the
breakers so as to disconnect consumer premises distribution system 10 from
distribution system 14.
[0111] When distribution systems 14 and 16 in the entire smart town are separated
from substation 24, and each consumer house 18 is disconnected 5 from distribution
system 14, CEMS 15 instructs town storage battery power conversion device 21 to
operate as a voltage source. Upon reception of the instruction from CEMS 15, town
storage battery power conversion device 21 converts the DC power of town storage
battery 20 into AC power and thereby starts to operate as an AC voltage source.
[0112] The following is an explanation about the reason why each consumer house
is disconnected from the distribution system immediately after occurrence of a power
failure. Immediately after occurrence of a power failure, switch 22 disconnects the
entire smart town from substation 24, and thereafter, town storage battery power
conversion device 21 is started as an AC voltage source without disconnecting load 5 in
consumer house 18, which results in simultaneous start-up of the loads that are not
switched off (for example, loads such as a lighting device and a drier that are powered
on if they are not switched off). This may possibly cause an excessively high current
to prevent start-up of town storage battery power conversion device 21. Thus, in the
present embodiment, after load 5, solar cell power conversion device 2 and storage
battery power conversion device 4 in consumer house 18 are disconnected from
distribution system 14, town storage battery power conversion device 21 is started as an AC voltage source.
[0113] After the autonomous operation is started by start-up of town storage battery
power conversion device 21, HEMS 7 checks with a user to see whether each load 5 is
switched off or not at a point of time when the AC voltage in distribution system 14 in
each consumer house 18 is stabilized, and thereafter, permits the breaker to be turned
on so as to supply electric power to an essential load. In this case, the information can
be transmitted to and received from the user through the operation by the user's input
into a user interface circuit (not shown) of HEMS 7. Thereby, in each consumer
house 18, the operation of an essential load can be ensured in the autonomous operation
by the manual operation to turn on a breaker and the manual operation to again turn on
a power supply of an essential load.
[0114] When supply of electric power to an essential load is started, HEMS 7 collects
the status information about solar cell 1 and storage battery 3 to the possible 5 extent, and notifies CEMS 15 about the collection result. After completion of this notification,
HEMS 7 automatically brings, into a connected state, the breaker to which solar cell
power conversion device 2 and storage battery power conversion device 4 are
connected. After supply of electric power to an essential load is started, solar cell
power conversion device 2 and storage battery power conversion device 4 in consumer
house 18 are started using the AC voltage output from town storage battery power
conversion device 21.
[0115] HEMS 7 controls solar cell power conversion device 2 and storage battery
power conversion device 4 based on the trading power target value at the system
interconnection point (consumer premises distribution system 10) that is transmitted
from CEMS 15. In the autonomous operation, the trading power target value at the
system interconnection point (consumer premises distribution system 10) in each
consumer house 18 is set according to the plan for trading electric power at the system
interconnection point in each consumer house 18 that constitutes the above-mentioned
operation plan, and transmitted from CEMS 15 to HEMS 7 separately for each
consumer house 18.
[0116] In the power management system according to the present embodiment, in the
autonomous operation, power balancing control using the drooping characteristic
shown in Fig. 17 is performed by solar cell power conversion device 2, storage battery
power conversion device 4, and town storage battery power conversion device 21. In
the autonomous operation, as described above, town storage battery power conversion
device 21 is controlled to operate as an AC voltage source while solar cell power
conversion device 2 and storage battery power conversion device 4 in each consumer
house 18 are controlled to operate as AC current sources in the same manner as in the
interconnection operation (in the normal operation). In the above-mentioned rolesharing
situation, town storage battery power conversion device 21 operating as an AC
voltage source can detect an excess or a shortage of the electric power (power amount)
in the entire smart town operating as an autonomous system, based on the electric
power output from town storage battery 20 to distribution 5 system 14.
[0117] On the other hand, second control circuit 209 in solar cell power conversion
device 2 inside consumer house 18 that operates as an AC current source converts the
electric power, which is generated by solar cell 1 and supplied from first DC/DC
conversion circuit 203, into an AC current, and then, supplies the converted AC current
to consumer premises distribution system 10. In this case, second control circuit 209
can detect the power generation amount of solar cell 1 using the voltage on DC bus 205.
Similarly, fourth control circuit 409 in storage battery power conversion device 4 can
detect the charge/discharge power of storage battery 3 using the voltage on DC bus 405.
On the other hand, second control circuit 209 and fourth control circuit 409 cannot
directly detect the excess/shortage of the electric power in the distribution system in a
smart town directly from the AC voltage in consumer premises distribution system 10.
[0118] Accordingly, in the present embodiment, the distributed power supply installed
in each consumer house 18 is notified, using a drooping characteristic, about the
excess/shortage of the electric power detected by town storage battery power
conversion device 21. In the following, power balancing control utilizing a drooping
characteristic will be described.
[0119] Fig. 17 is a conceptual diagram illustrating the operation principle of balancing
control utilizing a drooping characteristic in the power management system according
to the present embodiment.
[0120] Referring to Fig. 17, the horizontal axis shows the power balance in the entire
smart town while the vertical axis shows the system frequency during an autonomous
operation.
[0121] The state where power balance is "0" corresponds to the state where the total
supplied electric power and the total consumed electric power in the entire smart town
are equal. The total supplied electric power in a smart town is equivalent to the total
sum of: the discharge power of town storage battery 20; the total value of the electric
power generated by solar cells 1 in respective consumer houses 18; and the total value
of the discharge power (during discharging) of storage batteries 3 in respective
consumer houses 18. On the other hand, in the autonomous operation, 5 town storage
battery 20 is normally operated only for discharging. Thus, the total consumed
electric power in a smart town is equivalent to the total value of the electric power
consumed by loads 5 in respective consumer houses 18.
[0122] As shown in Fig. 17, when the total consumed electric power is greater than the
total supplied electric power (power balance is positive), the system frequency is
gradually decreased from predetermined center frequency fc (for example, 60 Hz) as
the consumed electric power increases. The AC voltage frequency output to
distribution system 16 can be decreased from fc, for example, by town storage battery
power conversion device 21 that converts the discharge power of town storage battery
20 into AC power. The AC voltage frequency of distribution system 16 is transmitted
by pole-mounted transformer 9 also to distribution system 14 (on the pole-mounted
transformer's secondary side) and consumer premises distribution system 10 in each
consumer house 18.
[0123] As described with reference to Figs. 11 and 13, the AC voltage frequency in
consumer premises distribution system 10 can be detected by solar cell power
conversion device 2 (sixth control circuit 2094) and storage battery power conversion
device 4 (eighth control circuit 4094), that is, on the distributed power supply side in
each consumer house 18. Thus, when a decrease in system frequency is detected in a
distributed power supply in each consumer house 18, the control target value
(distributed power supply) is modified to increase the electric power output from the
distributed power supply in order to maintain the power balance. In other words, the
electric power generated by solar cell 1 is increased and/or the discharge power of
storage battery 3 is increased (or charging is switched to discharging).
[0124] In contrast, when the total supplied electric power is greater than the total
consumed electric power (power balance is negative), the system frequency is
gradually increased from center frequency fc as the supplied electric power increases.
When an increase in system frequency is detected in the distributed power supply in
each consumer house 18, the control target value (distributed power supply) is modified
to decrease the electric power output from the distributed power 5 supply in order to
return the power balance to "0". In other words, the electric power generated by solar
cell 1 is suppressed and/or the discharge power of storage battery 3 is decreased (or
discharging is switched to charging).
[0125] Thus, in the power management system according to the present embodiment,
in the autonomous operation, the information related to the power balance in a smart
town is shared through the frequencies of the AC voltages in distribution systems 10,
14, and 16 (i.e., system frequencies), thereby performing power balancing control for
balancing the total supplied electric power and the total consumed electric power in a
smart town.
15 [0126] In the following, the control operation in the autonomous operation will be
described. First, the operation of solar cell power conversion device 2 will be
described again with reference to Figs. 9 to 11.
[0127] In the present embodiment, solar cell power conversion device 2 is started when
the DC voltage output from solar cell 1 becomes equal to or greater than a
predetermined reference value. At start-up of solar cell power conversion device 2,
fifth control circuit 2044 (Fig. 10) in first control circuit 204 instructs MPPT control
circuit 2041 (Fig. 10) to start MPPT control so as to maximize the electric power output
from solar cell 1. Furthermore, fifth control circuit 2044 outputs a control signal to
switching circuit 2043 to select the control command value from MPPT control circuit
2041.
[0128] On the other hand, sixth control circuit 2094 (Fig. 11) in second control circuit
209 calculates the amplitude (the current command value) of the AC current output
from DC/AC conversion circuit 208 such that the DC voltage on DC bus 205 detected
by voltmeter 206 becomes constant. A specific method of generating a current
command value will be described below.
[0129] As described above, in the power management system according to the present
embodiment, in the autonomous operation during a power failure, town storage battery
power conversion device 21 operates as an AC voltage source of the AC distribution
system in a smart town while the distributed power supply installed 5 in consumer house
18 operates as a current source based on the AC voltage at a system interconnection
point (consumer premises distribution system 10) in each consumer house 18.
[0130] In this case, since town storage battery power conversion device 21 manages the
AC voltage in distribution system 16, this town storage battery power conversion
device 21 can detect an excess/shortage of the electric power in the entire smart town
based on the excess/shortage of the electric power in distribution system 16. On the
other hand, since the distributed power supply operating as a current source in
consumer house 18 operates in such a manner as to control the electric power output to
consumer premises distribution system 10 in accordance with a target value, it cannot
directly detect an excess or a shortage of the electric power in consumer premises
distribution system 10.
[0131] As described above, when town storage battery power conversion device 21
detects an excess or a shortage of electric power, it first controls the charge/discharge
power from town storage battery 20 to thereby ensure the power balance in a smart
town. Furthermore, when electric power is in shortage, the system frequency, i.e., the
output frequency from town storage battery power conversion device 21 to distribution
system 16, is decreased in accordance with the drooping characteristic that is described
with reference to Fig. 17. In contrast, when electric power is excessive, the frequency
of the AC system voltage, i.e., the output frequency of town storage battery power
conversion device 21, is raised in accordance with the drooping characteristic. In fact,
the output frequency of town storage battery power conversion device 21 is set in
accordance with the drooping characteristic of which CEMS 15 notifies.
[0132] The distributed power supply installed in consumer house 18 detects the
frequency of the AC voltage at a system interconnection point (consumer premises
distribution system 10), and based on the drooping characteristic of which CEMS 15
notifies, determines whether the power supply amount in the entire smart town is
excessive or is in shortage. The operation plan (including a drooping characteristic)
from CEMS 15 is received by HEMS 7, and thereafter, this HEMS 7 notifies second
control circuit 209 about this operation plan through communication 5 interface circuit
212. The details of the method of generating a drooping characteristic will be
described later in detail.
[0133] Referring back to Figs. 9 and 11, the description of the operation of solar cell
power conversion device 2 will be continued. Phase detection circuit 2091 (Fig. 11)
in second control circuit 209 (Fig. 9) detects a zero cross point of the AC voltage output
from voltmeter 210. The zero cross point information detected by phase detection
circuit 2091 (Fig. 11) is input into frequency detection circuit 2092 and sixth control
circuit 2094 that are shown in Fig. 11.
[0134] Frequency detection circuit 2092 measures the cycle of the received zero cross
15 point detection information to thereby calculate the AC voltage frequency in consumer
premises distribution system 10, i.e., the system frequency. The frequency
information calculated by frequency detection circuit 2092 is output to drooping
characteristic table generation circuit 2093 and sixth control circuit 2094. Upon
reception of the system frequency, drooping characteristic table generation circuit 2093
calculates the differential power used for modifying the trading power target value
from solar cell power conversion device 2 to consumer premises distribution system 10
in accordance with the drooping characteristic of which CEMS 15 notifies, and then,
outputs the calculated differential power to sixth control circuit 2094. Sixth control
circuit 2094 calculates a trading power target value for solar cell power conversion
device 2 based on the above-mentioned differential power and the trading power target
value that is based on the notification from CEMS 15.
[0135] Fig. 18 is a conceptual diagram for illustrating the drooping characteristic for
calculating differential power in solar cell power conversion device 2.
[0136] Referring to Fig. 18, the drooping information for solar cell power conversion
device 2 based on the notification from CEMS 15 is set to obtain a drooping
characteristic table for defining drooping characteristic lines FC1 to FC3 in the figure
for calculating differential power Psb1 with respect to the system frequency. In the
same manner as with the trading power target value, a positive value of differential
power Psb1 shows the power selling direction in which electric power 5 is output from
a distributed power supply to consumer premises distribution system 10. A negative
value of differential power Psb1 shows the power buying direction opposite to the
power selling direction.
[0137] In this case, drooping characteristic lines FC1 to FC3 represent that the
drooping characteristic can be variably set in accordance with the status of the power
management system (for example, the SOC of town storage battery 20). In the
following description, drooping characteristic lines FC1 to FC3 will also be collectively
referred to as a drooping characteristic line FC.
[0138] According to drooping characteristic line FC, when the system frequency is
between a break frequency fa on the high frequency side and a break frequency fb on
the low frequency side, the result shows that Psb1 = 0. In a region where the system
frequency is higher than fa, Psb1 is decreased at an inclination ka in proportion to the
frequency (Psb1 < 0). In a region where the system frequency is lower than fb,
Psb1 is increased at an inclination kb in proportion to the frequency (Psb1 > 0).
[0139] As drooping characteristic information, four pieces of data including break
frequencies fa, fb and inclinations ka, kb are transmitted, and thereby, a drooping
characteristic table can be created in drooping characteristic table generation circuit
2093 (Fig. 11) in second control circuit 209 (Fig. 9). As these four pieces of data are
transmitted as drooping characteristic information from CEMS 15 to HEMS 7,
25 communication traffic can be reduced.
[0140] When fa1, fb1, ka1, and kb1 are transmitted as drooping characteristic
information from CEMS 15, a drooping characteristic table that defines drooping
characteristic line FC1 for solar cell power conversion device 2 is created by drooping
characteristic table generation circuit 2093 (Fig. 11) in second control circuit 209 (Fig.
9). Similarly, when fa2, fb2, ka2, and kb2 are transmitted as drooping characteristic
information, a drooping characteristic table that defines drooping characteristic line
FC1 is created. Also, when fa3, fb3, ka3, and kb3 are transmitted as drooping
characteristic information, a drooping characteristic table that defines drooping
characteristic line 5 FC3 is created.
[0141] Referring to Fig. 11, drooping characteristic table generation circuit 2093
outputs, as differential power information, differential power Psb1 calculated in
accordance with the drooping characteristic in Fig. 18. Upon reception of the
differential power information from drooping characteristic table generation circuit
2093 and the system frequency information from frequency detection circuit 2092,
sixth control circuit 2094 uses the differential power information output from drooping
characteristic table generation circuit 2093 to modify the trading power target value at
the system interconnection point (consumer premises distribution system 10) in
consumer house 18 based on the notification from CEMS 15, to thereby calculate a
final trading power target value (hereinafter also referred to as a PV control target
value) for solar cell power conversion device 2.
[0142] In the power management system according to the present embodiment, HEMS
7 processes the trading power target value, of which CEMS 15 notifies, at the system
interconnection point in consumer house 18, to thereby generate a trading power target
value for solar cell power conversion device 2 and a trading power target value for
storage battery power conversion device 4. For example, the trading power target
value for solar cell power conversion device 2 is set so as to preferentially use the
electric power generated by solar cell 1. Also, the trading power target value for
storage battery power conversion device 4 is set so as to satisfy the trading power target
value (set by CEMS 15) at the system interconnection point (consumer premises
distribution system 10) in consumer house 18.
[0143] Furthermore, differential power Psb1 corresponding to the detection value of
the system frequency in accordance with the drooping characteristic is added to the
trading power target value for solar cell power conversion device 2, to thereby set the
PV control target value for solar cell power conversion device 2. As will be described
later, also for storage battery power conversion device 4, a final trading power target
value (PV control target value) is set by modifying the trading power target value set by
HEMS 7 based on the differential power that follows the drooping characteristic.
[0144] Then, sixth control circuit 2094 (Fig. 11) notifies fifth control 5 circuit 2044 in
first control circuit 204 (Fig. 10) about this PV control target value in which differential
power Psb1 is reflected. Furthermore, in the power management system according
to the present embodiment, the trading electric power at the system interconnection
point (consumer premises distribution system 10) in consumer house 18 that is
measured by power measurement circuit 61 (Fig. 2) in power switchboard 6 is output
onto signal line 12. Then, through sixth control circuit 2094 (Fig. 11), fifth control
circuit 2044 (Fig. 10) can be notified of this trading electric power.
[0145] Fifth control circuit 2044 subtracts the measured trading electric power at the
system interconnection point (consumer premises distribution system 10) from the
received PV control target value. When the subtraction result shows that electric
power is excessively supplied to consumer premises distribution system 10, the electric
power generated by solar cell 1 is suppressed.
[0146] Specifically, when the output from MPPT control circuit 2041 is selected
(hereinafter referred to as an "MPPT control mode"), the control mode of solar cell 1 is
shifted to a voltage control mode. While shifting to a voltage control mode, fifth
control circuit 2044 reads: the command value supplied from MPPT control circuit
2041 to the present first DC/DC conversion circuit 203; and the integral value
information and the like of a proportional integral (PI) controller (not shown), and
thereafter, outputs a stop instruction to MPPT control circuit 2041. The MPPT control
mode corresponds to one example of the "first control mode of the energy creation
device".
[0147] On the other hand, for voltage control circuit 2042, fifth control circuit 2044
sets the control command value read from MPPT control circuit 2041 and the
information obtained by processing the above-mentioned integral value information
and the like, as initial values, in a PI controller (not shown) in voltage control circuit
2042, and then, outputs an instruction to start the voltage control.
[0148] In the voltage control mode, fifth control circuit 2044 controls the voltage
output from solar cell 1 (the detection value of voltmeter 201) such that the PV control
target value (the trading power target value) received from sixth control 5 circuit 2094
becomes equal to the electric power generated by solar cell 1. In the voltage control
mode, fifth control circuit 2044 generates a control signal of switching circuit 2043 so
as to output the control command value from voltage control circuit 2042. Thus, by
control of the output voltage from solar cell 1, the electric power generated by solar cell
1 is controlled in accordance with the PV control target value. The voltage control
mode corresponds to one example of the "second control mode of the energy creation
device".
[0149] In contrast, when the electric power supplied to consumer premises distribution
system 10 is in shortage based on the result of subtraction of the measured trading
electric power from the received PV control target value, the electric power generated
by solar cell 1 is controlled to be increased. Specifically, when the MPPT control
mode is selected, the MPPT control mode is maintained in order to maintain power
generation with maximum power. On the other hand, when the voltage control mode
is selected, the output voltage from solar cell 1 is controlled so as to increase the
electric power generated by solar cell 1. Furthermore, when the output voltage from
solar cell 1 becomes equal to or less than a reference value, fifth control circuit 2044
switches the control mode of solar cell 1 from the voltage control mode to the MPPT
control mode.
[0150] While shifting to the MPPT control mode, fifth control circuit 2044 reads the
present control command value from voltage control circuit 2042 and the integral value
information and the like of the PI controller (not shown) circuit, and thereafter, outputs
a stop instruction to voltage control circuit 2042.
[0151] On the other hand, for MPPT control circuit 2041, fifth control circuit 2044 sets
the present control command value read from MPPT control circuit 2041 and the
information obtained by processing the above-mentioned integral value information
and the like, as initial values, in the PI controller (not shown) in MPPT control circuit
2041, and then, outputs an instruction to start MPPT control. In the MPPT control
mode, the output voltage from solar cell 1 is adjusted so as to maximize the electric
power generated 5 by solar cell 1.
[0152] MPPT control circuit 2041 generates a control command value for first DC/DC
conversion circuit 203 so as to maximize the electric power generated by solar cell 1.
Furthermore, in the MPPT control mode, fifth control circuit 2044 generates a control
signal for switching circuit 2043 so as to output the control command value from
MPPT control circuit 2041.
[0153] In each of the MPPT control mode and the voltage control mode, the output
from first DC/DC conversion circuit 203 is converted into AC power by first DC/AC
conversion circuit 208 and supplied to consumer premises distribution system 10.
[0154] Then, the operation of storage battery power conversion device 4 will be
described again with reference to Figs. 9, 12, 13, and 19.
[0155] In the present embodiment, HEMS 7 instructs start-up of storage battery power
conversion device 4. When storage battery 3 is not used, storage battery power
conversion device 4 is configured to wait in a sleep mode (the operation mode
requiring about several minutes for start-up time but consuming electric power of about
several tens of w). As in solar cell power conversion device 2, after HEMS 7
receives the operation plan (including a drooping characteristic) from CEMS 15, this
HEMS 7 notifies fourth control circuit 409 about the received operation plan through
communication interface circuit 412. The drooping characteristic information of
which CEMS 15 notifies can be set in the same format as that of the drooping
characteristic information of which solar cell power conversion device 2 is notified, as
described with reference to Fig. 18.
[0156] Fig. 19 is a conceptual diagram for illustrating the drooping characteristic for
calculating the differential power in storage battery power conversion device 4.
[0157] Referring to Fig. 19, a drooping characteristic table is developed according to
the drooping characteristic information from CEMS 15, so as to define drooping
characteristic lines FC1 to FC3 in the figure for calculating differential power Psb2
with respect to the system frequency in storage battery power conversion device 4. In
the same manner as with differential power Psb1, a positive value of differential
power Psb2 shows the power selling direction in which electric power 5 is output from
a distributed power supply to consumer premises distribution system 10. A negative
value of differential power Psb2 shows the power buying direction opposite to the
power selling direction.
[0158] Since the details of the drooping characteristic information and creation of the
drooping characteristic table by drooping characteristic table generation circuit 4093
(Fig. 11) are the same as those in the case of the drooping characteristic for solar cell
power conversion device 2 described with reference to Fig. 18, the description thereof
will not be repeated.
[0159] As a result, also for storage battery power conversion device 4, drooping
characteristic line FC similar to that in Fig. 18 can be set. Drooping characteristic line
FC is set, for example, in accordance with the above-mentioned break frequencies fa,
fb, and inclinations ka, kb that are transmitted as drooping characteristic information.
As in Fig. 17, the drooping characteristic can be set variably in accordance with the
status of the power management system (for example, the SOC of town storage battery
20). In other words, three types of drooping characteristic lines FC1 to FC3 can be
created in accordance with the drooping characteristic information.
[0160] In particular, as to the drooping characteristic of storage battery power
conversion device 4, it is preferable to change break frequencies fa and fb in
accordance with the SOC of storage battery 3 in each consumer house 18.
Specifically, for storage battery 3 with low SOC, it is preferable to create a drooping
characteristic such that differential power Psb2 (Psb2 < 0) for increasing charge
power is generated with a smaller amount of frequency change from the center
frequency (fc  fa) than that in the case of storage battery 3 with high SOC. In the
example in Fig. 19, for storage battery 3 with low SOC, break frequency fa can be set
- 45 -
lower (closer to center frequency fc) than that in the case of storage battery 3 with high
SOC.
[0161] In contrast, for storage battery 3 with high SOC, it is preferable to create a
drooping characteristic such that differential power Psb2 (Psb2 > 0) for increasing
the discharge power is generated with a smaller amount of frequency 5 change from
center frequency fc (fc  fb) than that in the case of storage battery 3 with low SOC.
In the example in Fig. 19, for storage battery 3 with high SOC, break frequency fb can
be set higher (closer to center frequency fc) than that in the case of storage battery 3
with low SOC. In this way, storage battery 3 in each consumer house 18 can be
appropriately charged and discharged (so as to avoid overcharge and overdischarge)
such that storage battery 3 with low SOC is preferentially charged and such that storage
battery 3 with high SOC is preferentially discharged.
[0162] In addition, the drooping characteristic information about solar cell power
conversion device 2 and the drooping information about storage battery power
conversion device 4 are set separately. In other words, as two sets (for example, four
pieces/one set) of drooping characteristic information are set in HEMS 7 from CEMS
, the drooping characteristic for calculating differential power Psb1 in solar cell
power conversion device 2 (Fig. 18) and the drooping characteristic for calculating
differential power Psb2 in storage battery power conversion device 4 (Fig. 19) are
20 separately created.
[0163] Again referring to Fig. 13, phase detection circuit 4091 in fourth control circuit
409 detects a zero cross point of the AC system voltage output from voltmeter 410.
The zero cross point detected by phase detection circuit 4091 is input into frequency
detection circuit 4092 and eighth control circuit 4094.
[0164] Frequency detection circuit 4092 measures the cycle of the input zero cross
point detection information to thereby calculate the AC voltage frequency in consumer
premises distribution system 10, i.e., the system frequency. The frequency
information detected by frequency detection circuit 4092 is input into drooping
characteristic table generation circuit 4093 and eighth control circuit 4094. Upon
reception of the frequency of the AC system voltage, according to the drooping
characteristic shown in Fig. 19, drooping characteristic table generation circuit 4093
calculates differential power Psb2 for modifying the trading power target value from
storage battery power conversion device 4 to consumer premises distribution system
and then, outputs the calculated differential power Psb2 to eighth control 5 circuit 4094.
[0165] Drooping characteristic table generation circuit 2093 outputs differential power
Psb2 as differential power information. Upon reception of the differential power
information from drooping characteristic table generation circuit 4093 and the system
frequency information from frequency detection circuit 4092, eighth control circuit
10 4094 uses the differential power information output from drooping characteristic table
generation circuit 2093 to modify the trading power target value at the system
interconnection point (consumer premises distribution system 10) in consumer house
18 that is based on the notification from CEMS 15, thereby calculating a final trading
power target value for storage battery power conversion device 4 (hereinafter also
referred to as a BAT control target value).
[0166] Eighth control circuit 4094 adds differential power Psb2 corresponding to the
detection value of the system frequency to the trading power target value for storage
battery power conversion device 4 that is generated by HEMS 7 based on the trading
power target value at the system interconnection point in consumer house 18, of which
CEMS 15 notifies. Thereby, eighth control circuit 4094 sets the BAT control target
value for storage battery power conversion device 4. As described above, in HEMS 7,
the trading power target value for storage battery power conversion device 4 is set in
consideration that electric power generated by solar cell 1 is preferentially used.
[0167] Eighth control circuit 4094 (Fig. 13) notifies seventh control circuit 4044 (Fig.
12) in third control circuit 404 about the BAT control target value in which differential
power Psb2 is reflected. Furthermore, as in the case of solar cell power conversion
device 2, through signal line 12 and eighth control circuit 4094 (Fig. 13), seventh
control circuit 4044 (Fig. 12) is notified about the trading electric power at the system
interconnection point (consumer premises distribution system 10) in consumer house
18 that is measured by power measurement circuit 61 (Fig. 2) in power switchboard 6.
[0168] Seventh control circuit 4044 subtracts the measured trading electric power at the
system interconnection point (consumer premises distribution system 10) from the
BAT control target value of which this seventh control circuit 4044 is notified. When
the subtraction result shows that electric power is excessively supplied 5 to consumer
premises distribution system 10, excessive electric power is supplied to storage battery
for charging.
[0169] Specifically, when the output from charge control circuit 4041 is selected
(hereinafter referred to as a "charge mode"), seventh control circuit 4044 increases the
target charge power by charge control circuit 4041. On the other hand, when the
output from discharge control circuit 4042 is selected (hereinafter also referred to as a
"discharge mode"), seventh control circuit 4044 decreases the target discharge power
by discharge control circuit 4042.
[0170] In the discharge mode, in the case where electric power is excessively supplied
to consumer premises distribution system 10 even when the target discharge power is set at "0" , seventh control circuit 4044 switches the control mode of storage battery 3
from the discharge mode to the charge mode. Specifically, seventh control circuit
4044 outputs an instruction to stop discharge control circuit 4042 and outputs an
instruction to start charge control circuit 4041. In the charge mode, a control signal
20 for switching circuit 4043 is generated such that the output from charge control circuit
4041 is selected.
[0171] When the control mode is switched between the charge mode and the discharge
mode, the command value and the integral value information about a PI controller (not
shown) are initialized to "0". Thus, there is no inheritance of the initial value between
the charge mode and the discharge mode, unlike in the case of switching the control
mode in solar cell power conversion device 2.
[0172] In contrast, when the supply power to consumer premises distribution system 10
is in shortage based on the result of subtraction of the measured trading electric power
from the received BAT control target value, the discharge power from storage battery 3
is increased.
[0173] Specifically, when the discharge mode is selected, seventh control circuit 4044
increases the target discharge power in discharge control circuit 4042. On the other
hand, when the charge mode is selected, the target charge power for charge control
circuit 4041 is decreased. In the case where the supply power to 5 consumer premises
distribution system 10 is in shortage even when the target charge power is set at "0" in
the charge mode, the control mode of storage battery 3 is switched from the charge
mode to the discharge mode. Specifically, seventh control circuit 4044 outputs an
instruction to stop charge control circuit 4041 and outputs an instruction to start
discharge control circuit 4042. Furthermore, a control signal for switching circuit
4043 is generated so as to select the output from discharge control circuit 4042.
[0174] Then, again referring to Figs. 14 to 16, the operation of town storage battery
power conversion device 21 will be described .
[0175] As described above, in the autonomous operation during a power failure, town
storage battery power conversion device 21 operates as an AC voltage source to
support the distribution system in a smart town. After occurrence of a power failure,
town storage battery power conversion device 21 started as an AC voltage source in the
above-mentioned procedure controls town storage battery 20 to be charged and
discharged based on the operation plan of which CEMS 15 notifies.
[0176] Specifically, in the autonomous operation, based on the voltage on DC bus 605
that is output from voltmeter 606, eleventh control circuit 6044 in ninth control circuit
604 (Fig. 15) determines whether the electric power in a smart town is excessive or is
in shortage.
[0177] For example, in the case where town storage battery 20 operates in the charge
mode, it is determined that the electric power supplied in the smart town is excessive
when the voltage on DC bus 605 is higher than a target voltage. In this case, charge
control circuit 6041 generates a control command value for third DC/DC conversion
circuit 603 (Fig. 14) so as to increase the charge power. On the other hand, when
town storage battery 20 operates in the discharge mode, discharge control circuit 6042
generates a control command value for third DC/DC conversion circuit 603 (Fig. 14) so
as to decrease the discharge power of town storage battery 20.
[0178] Furthermore, in the case where the voltage on DC bus 605 is higher than the
target voltage even when the discharge power is decreased to "0" in the discharge mode, eleventh control circuit 6044 switches the control mode of town storage 5 battery from the discharge mode to the charge mode. In this case, eleventh control circuit 6044
outputs a stop instruction to discharge control circuit 6042 and outputs a start
instruction to charge control circuit 6041. Furthermore, a control signal for switching
circuit 6043 is generated so as to select the output from charge control circuit 6041.
[0179] As in the case of control of storage battery power conversion device 4, there is no inheritance of the initial value for switching between the charge mode and the
discharge mode, unlike in the case of switching the control mode in solar cell power
conversion device 2.
[0180] In contrast, when the voltage on DC bus 605 is lower than the above-mentioned
target voltage, it is determined that the electric power supplied in the smart town is in
shortage. In this case, when town storage battery 20 operates in the discharge mode,
eleventh control circuit 6044 (Fig. 15) in ninth control circuit 604 causes discharge
control circuit 6042 to generate a control command value for third DC/DC conversion
circuit 603 (Fig. 14) so as to increase the discharge power of town storage battery 20.
On the other hand, when town storage battery 20 operates in the charge mode, charge
control circuit 6041 generates a control command value for third DC/DC conversion
circuit 603 (Fig. 14) so as to decrease the charge power amount of town storage battery.
[0181] Furthermore, in the case where the voltage on DC bus 605 is lower than the target voltage even when the charge power is decreased to "0" in the charge mode,
eleventh control circuit 6044 switches the control mode of town storage battery 20 from
the charge mode to the discharge mode. In this case, eleventh control circuit 6044
outputs a stop instruction to charge control circuit 6041 and outputs a start instruction
to discharge control circuit 6042. Furthermore, a control signal for switching circuit
6043 is generated so as to select the output from discharge control circuit 6042. Thus,
the electric power supplied from town storage battery 20 to a smart town is controlled
by ninth control circuit 604.
[0182] Then, the operation of tenth control circuit 609 (Fig. 14) will be described.
Tenth control circuit 609 subtracts the charge/discharge 5 power target value
(operation plan), of which CEMS 15 notifies, from the charge/discharge power of town
storage battery 20 output from third DC/DC conversion circuit 603 (a positive value
shows discharging while charging shows a negative value) to thereby calculate a
difference from the operation plan of which CEMS 15 notifies. For example, the charge/discharge power of town storage battery 20 can be calculate by multiplying the
voltage on DC bus 605 detected by voltmeter 606 and the current on DC bus 605
detected by ammeter 607. The above-mentioned subtraction result showing a positive
value means that the discharge power of town storage battery 20 is greater than that of
the operation plan or the charge power of town storage battery 20 is less than that of the operation plan (hereinafter also referred to as a discharge-side operation, or simply
referred to as a discharge side). In contrast, the subtraction result showing a negative
value means that the charge power of town storage battery 20 is greater than that of the
operation plan or the discharge power of town storage battery 20 is less than that of the
operation plan (hereinafter also referred to as a charge-side operation, or simply
referred to as a charge side).
[0183] The following is an explanation about the control of third DC/AC conversion
circuit 608 that reflects the difference between the actual charge/discharge of town
storage battery 20 and the operation plan of which CEMS 15 notifies.
[0184] Upon reception of the drooping characteristic information about town storage
battery power conversion device 21 from CEMS 15 through communication interface
circuit 612 (Fig. 14), twelfth control circuit 6094 (Fig. 16) outputs the drooping
characteristic information to drooping characteristic table generation circuit 6092.
[0185] Fig. 20 shows a conceptual diagram for illustrating the drooping characteristic
of town storage battery power conversion device 21.
[0186] Referring to Fig. 20, the horizontal axis shows excess/shortage power Pvl for
quantitatively showing the excess/shortage amount of the electric power supplied from
the consumer side in a system town. Excess/shortage power Pvl is calculated from the
above-mentioned difference (an excess or a shortage) between the actual charge and
discharge of town storage battery 20 and the operation plan of which 5 CEMS 15 notifies.
Excess/shortage power Pvl is calculated by subtracting the actual charge/discharge
power of town storage battery 20 from the charge/discharge power target value
(operation plan) of which CEMS 15 notifies, in contrast to the above-mentioned
difference, such that the shortage amount of the supply power becomes a positive value.
Also, the vertical axis shows the output frequency of town storage battery power
conversion device 21, i.e., the frequency of the AC voltage output from third DC/AC
conversion circuit (Fig. 14) to distribution system 16 (the system frequency).
[0187] Excess/shortage power Pvl on the horizontal axis is set at a positive value (Pvl >
0) when the supply power is excessive, that is, when town storage battery 20 operates
on the charge side with respect to the operation plan. On the other hand, shortage
power Pvl is a negative value (Pvl < 0) when the supply power is in shortage, that is,
when town storage battery 20 operates on the discharge side with respect to the
operation plan.
[0188] The drooping characteristic information about town storage battery power
conversion device 21 is set such that the drooping characteristic table for defining
drooping characteristic line FCt shown in Fig. 20 is acquired. For example, drooping
characteristic line FCt is defined to set the system frequency at center frequency fc (for
example, 60 Hz) between breakpoint power Pa on the positive side (excessive power
side) and breakpoint power Pb on the negative side (shortage power side). Further,
according to drooping characteristic line FCt, in a region where Pvl > Pa (excessive
supply), the system frequency is increased at an inclination kat in proportion to Pvl in
order to decrease the electric power that is reversed in flow from each consumer house
18.
[0189] On the other hand, in a region where Pvl < Pb (shortage of supply), the system
frequency is decreased at an inclination kbt in proportion to Pvl in order to increase the
electric power that is reversed in flow from each consumer house 18. It should be
noted that the range in which the system frequency changes is limited to fall within the
range between a predetermined lower limit frequency (for example, 59.8 Hz) and a
predetermined upper limit frequency (for example, 5 60.2 Hz).
[0190] The above-mentioned four pieces of data including breakpoint power Pa, Pb
and inclinations kat, kbt are transmitted also as the drooping characteristic information
about town storage battery power conversion device 21 from CEMS 15, and thereby,
communication traffic can be reduced.
[0191] Again referring to Fig. 16, twelfth control circuit 6094 calculates
excess/shortage power Pvl in Fig. 20, and outputs the calculated power as
excess/shortage power information. Based on the drooping characteristic information
from CEMS 15, drooping characteristic table generation circuit 6092 creates a drooping
characteristic table for town storage battery power conversion device 21 that defines
drooping characteristic line FCt in Fig. 20. Furthermore, drooping characteristic table
generation circuit 6092 determines a system frequency based on the excess/shortage
power information from twelfth control circuit 6094 and the above-mentioned drooping
characteristic table information. The system frequency set by drooping characteristic
table generation circuit 6092 is input into sinusoidal wave generation circuit 6091.
[0192] Based on the measurement result of the AC voltage in distribution system 16
that is output from voltmeter 610 and the frequency information (system frequency)
from drooping characteristic table generation circuit 6092, sinusoidal wave generation
circuit 6091 generates a sinusoidal wave used as a reference of the AC voltage output
from third DC/AC conversion circuit 608, and outputs the generated sinusoidal wave to
twelfth control circuit 6094.
[0193] On the other hand, twelfth control circuit 6094 outputs the control target value
for third DC/AC conversion circuit 608 based on the sinusoidal wave from sinusoidal
wave generation circuit 6091 as a target value. Third DC/AC conversion circuit 608
operates according to the control command value from twelfth control circuit 6094 to
thereby output the AC voltage having the set system frequency to distribution system
[0194] Then, the method of creating a drooping characteristic of each distributed power
supply will be further described.
Again referring to Fig. 18, the drooping characteristic of which 5 solar cell power
conversion device 2 is notified is defined such that differential power Psb1 (on the
vertical axis) with respect to the system frequency (on the horizontal axis) is calculated,
as described above. In this case, since solar cell 1 is an energy creation device, it can
only control the generated electric power (control the output power).
[0195] In the present embodiment, when the system frequency rises according to the
drooping characteristic as described with reference to Fig. 20, differential power Psb1
is set such that Psb1 < 0. This leads to a decrease in the PV control target value for
solar cell power conversion device 2 to which differential power Psb1 is added. In
contrast, when the system frequency decreases due to a shortage of electric power
supplied in a smart town according to the drooping characteristic described with
reference to Fig. 20, differential power Psb1 is set such that Psb1 > 0. This leads to
an increase in the PV control target value for solar cell power conversion device 2 to
which differential power Psb1 is added.
[0196] CEMS 15 generates drooping characteristics of solar cell power conversion
device 2 and storage battery power conversion device 4 based on the elapsed time
period from the start of the autonomous operation, the stored energy (SOC) of town
storage battery 20, the stored energy (SOC) of storage battery 3 in consumer house 18,
and the SOC total value in a smart town.
[0197] Specifically, CEMS 15 calculates the stored energy of storage battery 3 and the
stored energy of town storage battery 20 that are required for ensuring the LCP for
hours, and generates a drooping characteristic based on the calculation result. For
example, the drooping characteristic is generated such that drooping characteristic lines
FC1 (a solid line), FC2 (a dotted line), and FC3 (a dashed-dotted line) are switched
based on the above-mentioned SOC data.
[0198] For example, when the stored energy (SOC) that is required for ensuring the
LCP for 72 hours is ensured, drooping characteristic line FC1 (a solid line) is set as a
basic drooping characteristic.
[0199] In contrast, when the stored energy (SOC) that can implement the LCP for 72
hours is not ensured, drooping characteristic line FC2 (a dotted 5 line) is set. On
drooping characteristic line FC2, in order to extract the electric power, to the extent
possible, generated from solar cell 1 in a frequency band in which the system frequency
is lower than 60 Hz, break frequency fb2 on the low frequency side is set closer to
center frequency fc (60 Hz) as compared with the above-mentioned drooping
characteristic line FC1 (solid line).
[0200] In this case, on drooping characteristic line FC2 (a dotted line) of storage
battery power conversion device 4 shown in Fig. 19, break frequency fb2 on the low
frequency side is set lower than break frequency fb2 on drooping characteristic line
FC2 (Fig. 18) of solar cell power conversion device 2. Thereby, CEMS 15 can be
urged to increase electric power generated by solar cell power conversion device 2 in an earlier stage in the situation where town storage battery 20 is on the discharge side
with respect to the operation plan.
[0201] Similarly, in the frequency band in which the frequency of the system voltage is
higher than 60 Hz, break frequency fa2 on drooping characteristic line FC2 (Fig. 19) of
solar cell power conversion device 22 is set higher than break frequency fa2 on
drooping characteristic line FC2 (Fig. 19) of storage battery power conversion device 4.
Thereby, charging of storage battery 3 with excessive electric power can be prioritized
over suppression of electric power generated by solar cell 1. Specifically, when
storage battery 3 is discharged, suppression of the discharge power from storage battery
3 is prioritized over suppression of the electric power generated by solar cell 1. On
the other hand, when storage battery 3 is charged, electric power supplied to storage
battery for charging is prioritized over suppression of the electric power generated by
solar cell 1.
[0202] As a result, in the situation where the stored energy (SOC) that can implement
the LCP for 72 hours is not ensured, the drooping characteristic can be set so as to
ensure the power balance in a smart town while prioritizing ensuring of the electric
power generated by solar cell 1.
[0203] On the other hand, in the state where each of town storage battery 20 and
storage battery 3 in consumer house 18 is almost in a fully-charged 5 state, drooping
characteristic line FC3 (a dashed-dotted line) is set in order to prioritize discharging
from storage battery 3. On drooping characteristic line FC3, relatively small
inclinations ka3 and kb3 are set so as to maintain the trading power target value (solar
cell power conversion device 2) that follows the operation plan.
[0204] Again referring to Fig. 19, the drooping characteristic of which storage battery
power conversion device 4 is notified is defined such that differential power Psb2 (on
the vertical axis) with respect to the system frequency (on the horizontal axis) is
calculated, as described above. In this case, storage battery 3 as an energy storage
device mainly performs averaging of the trading electric power based on the operation
plan at the system interconnection point (consumer premises distribution system 10) in
consumer house 18 (absorption of the trading electric power fluctuations resulting from
the prediction errors of the power generation amount and the load power consumption
amount, and the like).
[0205] Also in storage battery power conversion device 4, according to the drooping
20 characteristic described with reference to Fig. 20, when town storage battery 20
operates on the charge side with respect to the operation plan and the system frequency
rises, differential power Psb2 is set such that Psb2 < 0. This leads to a decrease in
the BAT control target value for storage battery power conversion device 4, to which
differential power Psb2 is added. In contrast, according to the drooping
characteristic described with reference to Fig. 20, when town storage battery 20
operates on the discharge side with respect to the operation plan and the system
frequency decreases, differential power Psb2 is set such that Psb2 > 0. This leads
to an increase in the BAT control target value for storage battery power conversion
device 4, to which differential power Psb2 is added.
- 56 -
[0206] The drooping characteristic of storage battery power conversion device 4 is also
generated by CEMS 15 based on the elapsed time period from the start of the
autonomous operation, the stored energy (SOC) of town storage battery 20, the stored
energy (SOC) of storage battery 3 in consumer house 18, and the SOC total value in a
smart town, as 5 described above.
[0207] For example, when the stored energy (SOC) required for ensuring the LCP for
72 hours is ensured, drooping characteristic line FC1 (a solid line) is set as a basic
drooping characteristic.
[0208] In contrast, when the stored energy (SOC) that can implement the LCP for 72
hours is not ensured, drooping characteristic line FC2 (a dotted line) is set. On
drooping characteristic line FC2, in order to increase the discharge power from storage
battery 3 or decrease the charge power of storage battery 3, in a frequency band in
which the system frequency is lower than 60 Hz, break frequency fb2 (dotted line) on
the low frequency side is set closer to center frequency fc (60 Hz) than break frequency
fb1 on the above-mentioned drooping characteristic line FC1 (a solid line).
[0209] Moreover, as described above, in a frequency band in which the frequency of
the system voltage is lower than center frequency fc (60 Hz), in order to extract the
electric power generated by solar cell 1 to the possible extent, break frequency fb2 on
drooping characteristic line FC2 (a dotted line) of storage battery power conversion
device 4 is set lower than break frequency fb2 on drooping characteristic line FC2 (a
dotted line in Fig. 19) of solar cell power conversion device 2.
[0210] On the other hand, in a frequency band in which the frequency of the system
voltage is higher than center frequency fc (60 Hz), break frequency fa2 on drooping
characteristic line FC2 (a dotted line) of storage battery power conversion device 4 is
set lower than break frequency fa2 on drooping characteristic line FC2 (a dotted line in
Fig. 19) of solar cell power conversion device 2. Thereby, before the electric power
generated by solar cell 1 is suppressed, the discharge power from storage battery power conversion device 4 can be suppressed or the charge power of storage battery power conversion device 4 can be increased.
[0211] Furthermore, as in Fig. 18, in the state where each of town storage battery 20
and storage battery 3 in consumer house 18 is almost in a fully-charged state, drooping
characteristic line FC3 (a dashed-dotted line) is set in order to prioritize discharging
from storage battery 3.
[0212] In the present embodiment, two distributed power supplies including 5 solar cell
power conversion device 2 and storage battery power conversion device 4 are installed
in consumer house 18. Thus, as described above, CEMS 15 creates an operation plan
for an autonomous operation so as to prioritize the output from solar cell 1 as an energy
creation device while suppressing discharging from storage battery 3 as much as
possible.

We Claim :
1. A power management system for a management section equipped with
a main distributed power supply to supply an AC voltage to a first
distribution system during a power 5 failure, and
a plurality of distributed power supplies including an energy creation
device, the power management system comprising:
a measuring instrument to measure electric power consumed by a load
electrically connected to each of the distributed power supplies through a second
distribution system that is connected through a transformer to the first distribution
system; a communication unit to communicate with the main distributed power supply,
each of the distributed power supplies, and the measuring instrument;
an information collection unit to collect, through the communication unit, the
consumed electric power that is measured by the measuring instrument and status
information about each of the main distributed power supply and the distributed power
supplies; a power generation prediction unit to predict electric power generated by the
energy creation device in the distributed power supplies;
a power consumption prediction unit to predict the electric power consumed by
the load during a power failure;
an operation plan creation unit to create a first operation plan for controlling the
main distributed power supply and a second operation plan for controlling the
distributed power supplies, the first operation plan and the second operation plan being
applied in an autonomous operation for addressing a power failure, and being created
based on a power generation prediction result by the power generation prediction unit,
a power consumption prediction result by the power consumption prediction unit, the
status information, and a power consumption actual result by the measuring instrument
that are collected by the information collection unit; and
a transmission management unit to
transmit the first operation plan to the main distributed power supply
through the communication unit in the autonomous operation, and
transmit the second operation plan to each of the distributed power
supplies through the communication unit in the autonomous operation, 5 wherein
in the autonomous operation, the first operation plan is updated in each a first cycle set to be equal to or greater than an information collection cycle by the information collection unit and transmitted to the main distributed power supply, and
the second operation plan is updated in each a second cycle longer than
the first cycle and transmitted to each of the distributed power supplies,
the main distributed power supply includes
a first controller to change an AC voltage frequency output from the
main distributed power supply to the first distribution system in accordance with an
excess or a shortage of electric power with respect to a power trade balance that follows the first operation plan in the main distributed power supply, and
each of the distributed power supplies includes
a second controller to control an output from each of the distributed
power supplies in accordance with a control target value obtained by adding, to the
second operation plan, a modification value according to an AC voltage frequency of
the second distribution system.
2. A power management system for a management section equipped with
a main distributed power supply to supply an AC voltage to a first distribution
system during a power failure, and
a plurality of distributed power supplies including an energy creation device,
the power management system comprising:
an information collection unit to collect
electric power consumed by a load electrically connected to each of the
distributed power supplies through a second distribution system that is connected to the
first distribution system, and
status information about each of the main distributed power supply and
the distributed power supplies;
a power generation prediction unit to predict electric power 5 generated by the
energy creation device in the distributed power supplies;
a power consumption prediction unit to predict the electric power consumed by
the load during a power failure; and an operation plan creation unit to create a first operation plan for controlling the main distributed power supply and a second operation plan for controlling the distributed power supplies, the first operation plan and the second operation plan being applied in an autonomous operation for addressing a power failure, and being created based on a power generation prediction result by the power generation prediction unit,
a power consumption prediction result by the power consumption prediction unit, the
status information, and a power consumption actual result of the load that are collected
by the information collection unit, wherein in the autonomous operation, the first operation plan is updated in each a first cycle set to be equal to or greater than an information collection cycle by the information collection unit, and transmitted to the main distributed power supply, and the second operation plan is updated in each a second cycle longer than the first cycle and transmitted to each of the distributed power supplies, the main distributed power supply includes
a first controller to change an AC voltage frequency output from the
main distributed power supply to the first distribution system in accordance with an
excess or a shortage of electric power with respect to a power trade balance that follows the first operation plan in the main distributed power supply, and
each of the distributed power supplies includes
a second controller to control an output from each of the distributed
power supplies in accordance with a control target value obtained by adding, to the
second operation plan, a modification value according to an AC voltage frequency of
the second distribution system.
3. The power management system according to claim 5 1 or 2, wherein
the second cycle is set at an integral multiple of the first cycle,
the power management system further comprises
an output suppression determination unit to determine, based on the status
information and the power consumption actual result that are collected by the
information collection unit, whether the electric power generated by the energy creation
device is suppressed or not, and
the operation plan creation unit
creates the first operation plan in each the second cycle, and
in a time period until the second cycle passes, changes the first operation
plan in each the first cycle to suppress electric power output from the main distributed
power supply or to increase stored energy in an energy storage device included in the
main distributed power supply when the output suppression determination unit
determines that the electric power generated by the energy creation device is
suppressed.
4. The power management system according to claim 3, wherein
when the output suppression determination unit determines that the electric
power generated by the energy creation device is suppressed, the operation plan
creation unit modifies the first operation plan to, according to a suppression amount
estimation value of the electric power generated,
suppress electric power output from the main distributed power supply,
or increase stored energy in the energy storage device included in the main
distributed power supply.
5. The power management system according to claim 3 or 4, wherein
a control mode of the energy creation device includes
a first control mode in which an operation is performed at a maximum
operation point of generated electric 5 power, and
a second control mode in which the generated electric power is
controlled, and
the output suppression determination unit determines whether the electric power
generated by the energy creation device is suppressed or not, using the control mode of
the energy creation device.
6. The power management system according to claim 3 or 4, wherein
the distributed power supplies further include an energy storage device
connected to the energy creation device through the second distribution system, and
the output suppression determination unit determines whether the electric power
generated by the energy creation device is suppressed or not, using charge power of the
energy storage device.
7. The power management system according to claim 1 or 2, wherein
a first drooping characteristic that defines the AC voltage frequency based on
the excess or the shortage of electric power is transmitted from the operation plan
creation unit to the main distributed power supply in each the first cycle, and
a second drooping characteristic that defines the modification value from the
AC voltage frequency in each of the distributed power supplies is transmitted from the
operation plan creation unit to the main distributed power supply in each the second
cycle.
8. The power management system according to claim 7, wherein
the distributed power supplies further include an energy storage device
connected to the energy creation device through the second distribution system, and
the second drooping characteristic is set separately between the energy creation
device and the energy storage device.
9. The power management system according to 5 claim 8, wherein
the second drooping characteristic of the energy storage device is created
such that a frequency change amount for causing the modification value
so as to increase discharge power from the energy storage device is smaller in the
energy storage device with much stored energy than in the energy storage device with
less stored energy, and
such that a frequency change amount for causing the modification value
so as to increase charge power of the stored energy is smaller in the energy storage
device with less stored energy than in the energy storage device with much stored
energy.
10. The power management system according to any one of claims 1 to 9,
Wherein each of the distributed power supplies, the load, and the second distribution
system are disposed in each of consumers in the management section, and
the second operation plan defines trading electric power from each of the
distributed power supplies in each of the consumers to the second distribution system.
11. The power management system according to any one of claims 1, 2, 6, and
7, wherein the distributed power supplies further include an energy storage device
connected to the energy creation device through the second distribution system,
the control target value includes a trading power target value from the energy creation device to the second distribution system, and a trading power target value
second distribution system, and the control target value before the modification value is added is set in the energy creation device at a value on a power selling side with respect to the energy storage device.
12. The power management system according to any one of cl
and 9, wherein the control target value includes
a trading power target value from the energy creation device to the second distribution system, and a trading power target v second distribution system, and
the control target value before the modification value is added is set energy creation device a storage device.
13. The power management system according to any one of claims 1, 2, and 6
to 11, wherein the second cycle is set at an integral multiple of the first cycle.