Field of the Invention
The present invention relates to a power distribution
system which includes a commercial power source as a power
supply connected to a power line and distributed power
source, and supplies a power to a load from a power system.
Background of the Invention
In recent years, a DC power distribution system, in
which a DC power is supplied to a load from a DC power
distribution device including a solar cell and fuel cell in
terms of power distribution efficiency or the like, is
becoming more common. Conventionally, as the DC power
distribution system, e.g., a configuration disclosed in
Patent Document 1 may be employed. The DC power
distribution system includes, as shown in FIG. 15, a solar
cell 1101 which converts solar light energy into electrical
energy (DC power), a converter 1103 which converts a DC
power generated by the solar cell 1101 into an appropriate
output voltage Vout to supply power to the load, a fuel cell
1102 which generates a power by chemical reaction of
substances, a converter 1104 which converts a DC power
generated by the fuel cell 1102 into an appropriate output
voltage Vout to supply power to the load, and a DC load 1105
which is operated by the DC power from the solar cell 1101
and the fuel cell 1102.
The DC power distribution system is linked to an AC
power system, which is configured as a DC/AC power
distribution system. The AC power system includes a bi-
directional converter 1110 which converts a DC power
outputted from the converters 1103 and 1104 into an AC power,
and converts an AC power supplied from a commercial power
source 1109 into a DC power.
The solar cell 1101 has output characteristics as
shown in FIG. 14, and an output power of the solar cell 1101
changes greatly according to its operating voltage. If the
converter 1103 can control such that the solar cell 1101
operates at an operating voltage Vmp, the solar cell 1101
can output a maximum output power Pmax and the solar cell
1101 can be used efficiently. Control for maximizing the
use of the solar cell 1101 by setting the output power of
the solar cell 1101 to the maximum output power Pmax is
called maximum power point tracking control (hereinafter,
referred to as MPPT control).
Further, there is provided power generation rules for
the fuel cell 1102. For example, the power generation rules
prescribe the maximum output power, or regulate a steep
change in power generation. According to the power
generation rules, since the power generation is performed in
a manner appropriate for the fuel cell 1102, it is possible
to extend the life of the fuel cell 1102 while efficiently
generating power from the fuel cell 1102. As described
above, in a DC power generation device such as the solar
cell 1101 and the fuel cell 1102, it is profitable to
generate power according to their circumstances of the power
generation rules, the MPPT control or the like.
In the above power distribution system, if the power
consumption of the DC load 1105 is smaller than the power
generation of the solar cell 1101 and the like, the surplus
power can flow reversely to the commercial power source 1109,
i.e., can be sold to a power company.
Also, as disclosed in Patent Document 2, there is a DC
power distribution system including a storage battery. In
this power distribution system, the storage battery is used
mainly for backup, as being discharged when an amount of the
power generated by the DC power generation device is small.
[Patent Document 1] Japanese Patent Application
Publication No. 2009-232674
[Patent Document 2] Japanese Patent Application
Publication No. 2009-159730
However, the reverse flow of power is not allowed
indefinitely all the time. For example, the reverse flow of
power is prohibited every predetermined period, or the
allowable amount of the reverse flow power is limited. In
the above power distribution system, in a case where the
reverse flow of power is not allowed as such, the power
generation of the solar cell 1101 and the like may be larger
than the power consumption to generate the surplus power.
In this case, in order to suppress an increase in voltage of
a DC power line, it is forced to generate power with low
power generation efficiency without following the MPPT
control or the like.
As described above, in the case where the reverse flow
of power is not allowed, it is concerned that the DC power
generation device cannot generate power in accordance with
the MPPT control and the power generation rules.
On the other hand, in a case where a plurality of
power distribution systems are connected to a power line
connected to a commercial power source, a power is supplied
to the power line from a distributed power source provided
in each power distribution system, and further a power can
be supplied from a distributed power source of a specific
power distribution system to load devices of another power
distribution system.
Specifically, e.g., in a multiple dwelling house,
plural power distribution systems corresponding to dwelling
units are connected to one power line connected to a
commercial power source. Each of the power distribution
systems generally corresponds to each of the dwelling units
included in the multiple dwelling house.
Further, if a distributed power source (e.g., solar
cell) provided in a certain dwelling unit can generate the
surplus power beyond the power required to be supplied to
load devices provided in the dwelling unit, it is possible
to supply the surplus power from the dwelling unit to
another dwelling unit via the power line. Therefore, the
transfer of power can be achieved between the plural power
distribution systems corresponding to the multiple dwelling
units.
However, in the case where the transfer of power can
be achieved via the power line as described above, since the
power line is connected to the commercial power source, the
power may flow to the commercial power source from the
distributed power source which has generated the surplus
power. In this way, when the power flows to the commercial
power source from the distributed power source, reverse
power flow may occur such that power flows to the power
company. The reverse power flow may cause a disadvantage of
reducing the electrical stability of the power line.
Summary of the Invention
In view of the above, the present invention provides a
power distribution system capable of suppressing reverse
power flow while enabling the transfer of power through a
power line connected to a commercial power source between
power distribution apparatuses connected to the power line.
Further, the present invention also provides a power
distribution system in which a DC power generation device
can perform properly power generation regardless of
regulation of reverse power flow.
In accordance with a first aspect of the present
invention, there is provided a power distribution system
including: a DC power system in which a DC power generated
by a DC power generation device is supplied to a DC load via
a DC supply line; an AC power system which is linked to the
DC power system, for supplying an AC power from an AC power
source via an AC supply line; a battery which is connected
to the DC supply line; and a control unit which adjusts
reverse power flowing to the AC power source by
charging/discharging the battery.
Further, the power distribution system includes: a bi-
directional converter which converts the AC power from the
AC supply line into a DC power, and converts the DC power
from the DC supply line into an AC power; a DC/DC converter
connected to the DC supply line, which converts the DC power
inputted from the DC power generation device into a desired
DC power in accordance with predetermined control rules
stored in the DC/DC converter, and supplies the converted DC
power to the DC load; a charging/discharging circuit
provided between the DC supply line and the battery, which
charges the battery with a power from the DC supply line and
discharges the power from the battery to the DC supply line;
and a reverse power detection circuit which is connected to
the AC supply line and detects the reverse power flowing to
the AC power source, wherein the control unit adjusts the
reverse power flow by using the charging/discharging circuit
to charge/discharge the battery based on detection results
of the reverse power flow detection circuit.
For example, if the power generation is greater than
the power demand, the DC power is supplied to the AC supply
line through the bi-directional converter. At this point,
the power may reversely flow to the AC power source for sale.
In this case, the reverse flow of power is not allowed
indefinitely all the time. For example, the reverse flow of
power is prohibited or the allowable amount of reverse flow
power is limited, at an interval of a predetermined time
period. With the above configuration, the reverse power
flow is adjusted by charging/discharging the battery.
Accordingly, the reverse power flow can be adjusted without
adjusting the power generated by the DC power generation
device. Thus, the DC power generation device can properly
generate a power regardless of the reverse power flow.
Preferably, the control unit prevents a reverse flow
of the power by charging the battery with a power from the
DC supply line by the charging/discharging circuit, the
power being equivalent to the reverse flowing power detected
by the reverse flowing power detection circuit.
By this configuration, the power 'equivalent to the
reverse flowing power is charged in the battery from the DC
power line by the charging/discharging circuit. Thus, it is
possible to prevent the power from reversely flowing without
adjusting the power generated by the DC power generation
device.
The power distribution system may further include a
voltage detection unit for detecting a voltage of the DC
supply line, wherein the control unit may control the bi-
directional converter such that the voltage of the DC supply
line maintains a reference value.
With this configuration, the power is transferred
between the AC and DC power systems such that the voltage of
the DC supply line is equal to the reference value.
Accordingly, the power supplied to the DC load and the power
demanded by the DC load can be made in balance. In other
words, when the voltage of the DC supply line is equal to
the reference value, the power supply and demand are in
balance. Specifically, if the voltage of the DC supply line
exceeds the reference value, the power is supplied to the AC
supply line from the DC supply line through the bi-
directional converter.
On the other hand, if the voltage of the DC supply
line is less than the reference value, the power is supplied
to the DC supply line from the AC supply line through the
bi-directional converter. Therefore, even if there is an
imbalance between the power generation of the DC power
generation device and the power demand of the DC load, there
is no need to adjust the power generated by the DC power
generation device. Thus, regardless of the power demand of
the DC load, the DC power generation device can properly
generate the power.
When the voltage of the DC supply line detected by the
voltage detection unit becomes an upper limit or more, the
upper limit being greater than the reference value, the
control unit may control the DC/DC converter to suppress the
power generated by the DC power generation device such that
the voltage of the DC supply line becomes less than the
upper limit.
For example, if the power required to be supplied from
the DC supply line to the AC supply line in order to
maintain a power equilibrium state exceeds the maximum
output power of the bi-directional converter, or the reverse
flow of the power is limited, the power of the DC supply
line cannot be sufficiently supplied to the AC supply line.
Accordingly, the voltage of the DC supply line increases.
In the present invention, when the voltage of the DC
supply line becomes equal to or greater than the upper limit,
it is controlled such that the voltage becomes less than the
upper limit. That is, the power generated by the DC power
generation device is suppressed through the DC/DC converter
by the controller, and an increase in the voltage of the DC
supply line is suppressed. Accordingly, overpower is
prevented from occurring in the power distribution system,
thereby enhancing the safety of the system.
Further, when the voltage of the DC supply line
detected by the voltage detection unit becomes equal to or
less than a lower limit, the lower limit being smaller than
the reference value, the control unit may discharge the
power from the battery to the DC supply line by the
charging/discharging circuit.
By doing so, if the voltage of the DC supply line
becomes equal to or less than the lower limit, the power of
the battery is discharged to the DC supply line. Here, the
lower limit is set based on the voltage of the DC supply
line when the power supply is insufficient for the power
demand of the DC load. As a case where the voltage of the
DC supply line is equal to or less than the lower limit, for
example, there may be a case where the power cannot be
supplied from the AC supply line to the DC supply line due
to a power failure or the like.
When the voltage of the DC supply line is equal to or
less than the lower limit, the power of the battery is
discharged to the DC supply line through the
charging/discharging circuit such that the voltage of the DC
supply line becomes greater than the lower limit. Thus,
while performing the power generation appropriate for the DC
power generation device, the power can be more stably
supplied to the DC load.
Further, when the voltage of the DC supply line
detected by the voltage detection unit is equal to or less
than a threshold value between the reference value and the
lower limit, the control unit may start the
charging/discharging circuit.
Then, when the voltage of the DC supply line becomes
equal to or less than the threshold value, the
charging/discharging circuit is started. In this way, since
the charging/discharging circuit can be stopped until the
voltage of the DC supply line becomes equal to or less than
the second threshold value, it is possible to reduce the
operating power of the charging/discharging circuit.
Further, since the charging/discharging circuit is
started before the voltage becomes equal to or less than the
lower limit, the charging/discharging circuit can convert
the AC power from the AC power system into a DC power and
supply the DC power to the DC supply line immediately when
the voltage becomes equal to or less than the lower limit.
Thus, it is possible to more quickly compensate for the lack
of power supply to the DC load. As described above, at the
AC side converter, it is possible to achieve follow-up
control for voltage drop and also reduce the power
consumption.
In accordance with a second aspect of the present
invention, there is provided a power distribution system
including: a DC power system in which a DC power generated
by a DC power generation device is supplied to a DC load via
a DC supply line; an AC power system which is linked to the
DC power system and in which an AC power from an AC power
source is supplied via an AC supply line; a bi-directional
converter which converts an AC power from the AC supply line
into a DC power, and converts a DC power from the DC supply
line into an AC power; a DC/DC converter which is connected
to the DC supply line, converts the DC power inputted from
the DC power generation device into a desired DC power
according to predetermined control rules stored in the DC/DC
converter, and supplies the converted DC power to the DC
load; a battery which is connected to the DC supply line;
and a charging/discharging circuit which is provided between
the DC supply line and the battery, for charging the battery
with a power from the DC supply line and discharging a power
from the battery to the DC supply line.
In the power distribution system, the bi-directional
converter stores a reference value, and,, when a voltage of
the DC supply line deviates from the reference value,
controls a power outputted to the DC supply line and the AC
supply line such that the voltage of the DC supply line is
equal to the reference value; the DC/DC converter stores an
upper limit greater than the reference value, and, when the
voltage of the DC supply line becomes equal to or greater
than the upper limit, controls a power outputted to the DC
supply line such that the voltage of the DC supply line
becomes less than the upper limit; and the
charging/discharging circuit stores a lower limit smaller
than the reference value, and, when the voltage of the DC
supply line becomes less than the lower limit, controls
charging and discharging of the battery such that the
voltage of the DC supply line is equal to the lower limit.
In this configuration, without performing central
control through a central controller, each converter and
charging/discharging circuit performs control. That is,
each converter and charging/discharging circuit controls the
voltage of the DC supply line by comparing the voltage of
the DC supply line with a command value or threshold value
stored therein. In this way, each converter can make the
power supply and demand in balance without communicating
with another converter.
In accordance with a third aspect of the present
invention, there is provided a power distribution system
including: a plurality of power distribution apparatuses,
each having a distributed power source provided in a power
line connected to a commercial power source; and a storage
device connected to the power line for storing a power
flowing to the commercial power source from the distributed
power source. Further, each of the power distribution
apparatuses includes at least one load device to which the
power is supplied, and a power can be supplied to the load
device of another one of the power distribution apparatuses
from the distributed power source of at least one of the
power distribution apparatuses.
With the above configuration, the power line is
provided with the storage device storing the power flowing
to the commercial power source from the distributed power
source. Accordingly, the transfer of power between the
power distribution apparatuses connected to the power line
can be achieved through the power line connected to the
commercial power source. By storing a power in the storage
device, it is possible to suppress the reverse flow of the
power to the commercial power source from the distributed
power source of the power distribution apparatus.
Further, the power distribution system may include a
sensor connected to the power line between the commercial
power source and the power distribution apparatuses, for
detecting a current flowing in the power line, wherein the
storage device is controlled based on detection results of
the sensor.
According to this configuration, the storage device is
controlled based on the detection results (i.e., the current
intensity flowing in the power line) of the sensor provided
between the commercial power source and the power
distribution apparatuses. Thus, the reverse power flow can
be suppressed automatically based on the current flowing in
the power line (i.e., the current value of the power line).
Preferably, the storage device is controlled based on
a command signal outputted from power management facilities
for managing power of the commercial power source.
By doing this, the storage device is controlled based
on the command signal outputted from the power management
facilities managing the power of the commercial power source.
Accordingly, in a state where the command signal for
suppressing the reverse power flow is not outputted from the
power management facilities, the power is not stored in the
storage device, and the reverse power flow is allowed to
enable the sale of electric power from the power
distribution apparatuses.
Further, the storage device may be discharged to
supply a power to the at least one load device.
According to the above configuration, by discharging
the power from the storage device, the power is supplied to
at least one load device. Accordingly, since the storage
device can also supply the power to the load device of the
power distribution apparatuses, it is possible to reduce the
power (i.e., purchased power) supplied from the commercial
power source.
A power supply to the load device of a specific power
distribution apparatus among the power distribution
apparatuses may be limited based on the power discharged
from the storage device.
According to the above configuration, on the basis of
the power being discharged from the storage device, the
power supply to the load device of the specific power
distribution apparatus among the power distribution
apparatuses can be limited. Accordingly, it is possible to
reduce the power (i.e., purchased power) supplied from the
commercial power source. Specifically, if the discharge
capacity of the storage device is low, by limiting the power
supply to the load device of the specific power distribution
apparatus, the distributed power source or the storage
device can feed the power required for the other load
devices, thereby reducing the power supply from the
commercial power source.
Further, a power supply to the load device of a
specific power distribution apparatus among the plurality of
power distribution apparatuses may be cut off based on the
power being discharged from the storage device.
According to the above configuration, on the basis of
the power being discharged from the storage device, the
power supply to the load device of the specific power
distribution apparatus among the power distribution
apparatuses can be cut off. Accordingly, it is possible to
surely reduce the power supply from the commercial power
source.
Power generation of the distributed power source may
be limited based on a charging state of the storage device.
According to the above configuration, based on the
charging state of the storage device, the power generation
of the distributed power source is limited. Accordingly, if
the storage device is fully charged, the power generation of
the distributed power source is limited. Thus, it is
possible to suppress the reverse power flow while preventing
the storage device from being overcharged.
Power generations of a plurality of the distributed
power sources may be limited sequentially based on
priorities that are set in advance.
According to the above configuration, based on the
priorities that are set in advance, the power generations of
a plurality of the distributed power sources are limited
sequentially. Accordingly, it is possible to control the
power generations of a plurality of the distributed power
sources in the order desired.
Preferably, each of the power distribution apparatuses
is provided in each dwelling unit of a multiple dwelling
house.
Accordingly, the transfer of power can be achieved
between dwelling units of the multiple dwelling house.
Further, it is possible to suppress the reverse power flow
from the multiple dwelling house.
Further, the power distribution system may include a
power measuring sensor for measuring an amount of a power
being supplied to each of the power distribution apparatuses
from the power line, wherein transfer of the power between
the power distribution apparatuses is controlled based on
measurement results of the power measuring sensor.
According to the above configuration, on the basis of
the measurement results (the amount of the power supplied to
each of the power distribution apparatuses from the power
line) of the power measuring sensor, the transfer of the
power between the power distribution apparatuses is managed.
Accordingly, the transfer of the power can be managed
between the power distribution apparatuses and the sale of
an electric power can be achieved between the power
distribution apparatuses.
The transfer of the power between the power
distribution apparatuses may be controlled based on
information relating to a power consumed in the load device
and a power supplied from the distributed power source of
each of the power distribution apparatuses.
In this case, based on the information relating to the
power consumed in the load device and the power supplied
from the distributed power source in the power distribution
apparatus, the transfer of the power between the power
distribution apparatuses is managed. Accordingly, the
transfer of the power can be finely and minutely managed
between the power distribution apparatuses and the sale of
the electric power can be achieved between the power
distribution apparatuses.
Further, the power distribution apparatus may include
a power supply control unit for controlling transfer of a
power through the power line, and the power distribution
system may further include a controller connected to
communicate with the power supply control units, for
controlling the power supply control units to manage the
transfer of the power between the power distribution
apparatuses based on the measurement results of the power
measuring sensor.
According to the above configuration, the power
distribution system includes the controller that is
communicatively connected to the power supply control units
respectively provided in the power distribution apparatuses.
Then, based on the measurement results of the power
measuring sensor, the controller controls the plural power
supply control units to manage the transfer of the power
between the power distribution apparatuses. Thus, the
plural power supply control units are controlled by the
controller, thereby collectively managing the transfer of
the power between the power distribution apparatuses.
When a power is supplied to the power distribution
apparatus, the power distribution apparatus may be billed
based on an amount of the. power supplied to the power
distribution system, and there may be set a difference
between billing for an amount of a power supplied to the
power distribution apparatus from the commercial power
source and billing for the amount of the power supplied to
the power distribution apparatus from the distributed power
source.
According to the above configuration, for example, by-
setting the billing amount for the power supplied from the
commercial power source to the power distribution apparatus
to be greater than the billing amount for the power supplied
from the distributed power source to the power distribution
apparatus, the user to be billed can be encouraged to
purchase the power from the distributed power source.
Preferably, the power distribution system further
includes a display device for displaying billing-related
information.
In this case, the user to be billed can determine
whether to purchase a power from which power source of the
commercial power source and the distributed power source by
referring to the billing-related information displayed on
the display device.
The distributed power source may include multiple
types of power sources. In this case, the power
distribution apparatus having the distributed power source
which has supplied a power outputs information for
distinguishing the type of the power source which has
supplied the power as data.
According to the above configuration, it is possible
to obtain the information for distinguishing the distributed
power source which has supplied the power, from the power
distribution apparatus having the distributed power source
which has supplied the power and utilize the information in
various controls.
Further, when the power distribution apparatus to
which the power has been supplied is billed based on the
power supplied to the power distribution apparatus, the
amount of power supplied to the power distribution apparatus
may be billed differently according to the type of the
distributed power source used to supply the power to the
power distribution apparatus.
By doing this, the amount of the power is billed
differently according to the type of the distributed power
source used to supply the power to the power distribution
apparatus. Accordingly, for example, by setting the billing
amount for the power supplied from the distributed power
source to the power distribution apparatus using a specific
power source (e.g. solar cell) to be smaller than the
billing amount for the power supplied from the distributed
power source to the power distribution apparatus using
another power source, the user to be billed can be
encouraged to purchase power from the specific power source.
Brief Description of the Drawings
The objects and features of the present invention will
become apparent from the following description of
embodiments, given in conjunction with the accompanying
drawings, in which:
FIG. 1 is a configuration diagram of a power
distribution system in accordance with a first embodiment of
the present invention;
FIG. 2 is a configuration diagram schematically
showing a configuration of a power supply system including
the power distribution system in accordance with the first
embodiment of the present invention;
FIG. 3 is a flowchart for explaining an operation of a
control device provided in a power distribution apparatus
selling an electric power in the power distribution system
in accordance with the first embodiment of the present
invention;
FIG. 4 is a flowchart for explaining a billing-related
operation of the control device for the power purchased and
sold in the power distribution system in accordance with the
first embodiment of the present invention;
FIG. 5 is a flowchart for explaining an operation of
the control device to suppress a reverse power flow in the
power distribution system in accordance with the first
embodiment of the present invention;
FIG. 6 is a configuration diagram of a power
distribution system in accordance with a second embodiment
of the present invention;
FIG. 7 is a flowchart for explaining an operation of
the control device to suppress a reverse power flow in the
power distribution system in accordance with the second
embodiment of the present invention;
FIG. 8 is a block diagram showing a configuration of a
power distribution system in accordance with a third
embodiment of the present invention;
FIG. 9 is a block diagram specifically showing a
control unit in the power distribution system in accordance
with the third embodiment of the present invention;
FIG. 10 is a block diagram showing a configuration of
converters 155 to 159 in the power distribution system in
accordance with the third embodiment of the present
invention;
FIGS. 11A and 11B illustrate a graph showing
transition of first and second threshold values and first
and second command values, and a graph showing transition of
the first command value and voltage V in the power
distribution system in accordance with the third embodiment
of the present invention, respectively;
FIGS. 12A and 12B illustrate a flowchart showing a
processing procedure of a power feeding program, and a
flowchart showing a processing procedure of a reverse power
flow regulation program in accordance with the third
embodiment of the present invention, respectively;
FIG. 13 is a block diagram more specifically showing a
control unit in the power distribution system in accordance
with a fourth embodiment of the present invention;
FIG. 14 illustrates a graph showing voltage-power
characteristics of a solar cell; and
FIG. 15 is a block diagram showing a configuration of
a conventional power distribution system.
Detailed Description of the Embodiments
Hereinafter, embodiments of the present invention will
be described in detail with reference to the accompanying
drawings. Further, each figure is a schematic diagram
illustrating only a configuration required to explain a
power distribution system, and an illustration and
description of the other configuration will be omitted.
(First Embodiment}
As shown in FIG. 1, a power distribution system 50
includes a plurality of power distribution apparatuses 52
which are connected to one power line 51 connected to a
commercial AC power source 2 serving as a commercial power
source. In the embodiment, the power line 51 is a DC power
line serving as a trunk line of a power supply path provided
in a multiple dwelling house such as an apartment house, and
each of the power distribution apparatuses 52 is provided in
each dwelling unit of the multiple dwelling house. Thus, a
power distribution part 53 constituted by a plurality of the
power distribution apparatuses 52 is configured to
distribute power to the entire multiple dwelling house.
k
Each of the power distribution apparatuses 52 has a
distributed power source 54, load devices 55 to which power
is supplied, and a control unit 7 which controls the power
being supplied to the load devices 55 from the commercial AC
power source 2 and the distributed power source 54. The
control unit 7 is connected to the power line 51 through an
AC distribution board 11.
In this embodiment, the distributed power source 54
includes a solar cell 3, a fuel cell 4 and a storage battery
16. The solar cell 3 is a power generation source which
generates power by converting solar light energy into power.
Further, the fuel cell 4 is a power generation source which
generates power through a chemical reaction between a fuel
and an oxidizer. In addition, the storage battery 16 is a
chargeable/dischargeable power supply, which stores the
power supplied from the commercial AC power source 2, the
solar cell 3 and the fuel cell 4, and discharges the stored
power if necessary. The power from the power sources (i.e.,
the solar cell 3, the fuel cell 4 and the storage battery
16) constituting the distributed power source 54 is supplied
to the load devices 55 through the control unit 7.
The load devices 55 include DC devices 5 (see FIG. 2)
such as an air conditioner and an illumination apparatus.
The load devices 55 are connected to the control unit 7 via
a DC distribution board 8. Accordingly, the power supply
path is allowed to branch by the DC distribution board 8
such that the power can be supplied to a plurality of the
load devices 55 (i.e., the DC devices 5) in one dwelling
unit. Further, AC devices 6 (see FIG. 2) are connected to
the control unit 7 via the AC distribution board 11.
Accordingly, the power supply path is allowed to branch by
the AC distribution board 11 such that the power can be
supplied to a plurality of the load AC devices 6 in one
dwelling unit.
The control unit 7 serving as a power supply control
unit converts a power supplied to the control unit 7 from
the commercial AC power source 2 into a power corresponding
to the load devices 6 and 55 in the dwelling unit, and
supplies the power to the load devices 6 and 55. In
addition, the control unit 7 converts a power supplied from
the distributed power source 54 into a power corresponding
to the load devices 6 and 55 in the dwelling unit, and
supplies the power to the load devices 6 and 55. That is,
if the solar cell 3 or the fuel cell 4 generates power, or
if the storage battery 16 can discharge power, the power is
supplied to the load devices 6 and 55 from the distributed
power source 54 as well as the commercial AC power source 2.
Further, if the distributed power source 54 can
sufficiently supply power to load devices 6 and 55, the
commercial AC power source 2 may not supply power to the
load devices 6 and 55. In other words, the power may be
supplied from either of the commercial AC power source 2 and
the distributed power source 54 as long as sufficient power
is supplied to the load devices 6 and 55.
Further, the control unit 7 functions as not only a
converter which converts an AC power supplied from the
commercial AC power source 2 into a DC power to be supplied
to the load devices 55, but also an inverter which converts
a DC power supplied from the distributed power source 54
into an AC power to be supplied to the AC devices 6 and the
power line 51.
In other words, under certain conditions, the control
unit 7 converts a DC power supplied to the control unit 7
from the distributed power source 54 into an AC power, and
supplies the AC power to the power line 51. Accordingly, in
the power distribution system 50, since the multiple power
distribution apparatuses 52 are connected to the common
power line 51, it is possible to supply a power from the
distributed power source 54 of a specific power distribution
apparatus 52 to the load devices 6 and 55 of another power
distribution apparatus 52 via the power line 51. In this
embodiment, the power can be transferred between dwelling
units.
Next, a power supply system 1 including the power
distribution apparatus 52 of each dwelling unit, the power
distribution apparatus 52 serving as a constituent part of
the power distribution system 50 will be described in detail
with reference to FIG. 2. Further, the power distribution
apparatus 52 of each dwelling unit has the same
configuration.
As shown in FIG. 2, the dwelling unit is provided with
the power supply system 1 to supply power to various devices
(illumination apparatus, air conditioner, home appliance,
audio and video apparatus, etc.) installed in the home. The
power supply system 1 is configured to not only supply power
from the household commercial power source (AC power source)
2 to various devices, but also supply power from the solar
cell 3 generating power by using sunlight or the fuel cell 4
to various devices. The power supply system 1 supplies
power to the AC devices 6 being operated by an alternating
current (AC) power source (AC power source) in addition to
DC devices 5 being operated by a direct current (DC) power
source (DC power source).
The power supply system 1 includes the control unit 7
and the DC distribution board (having a DC breaker therein)
8. Further, the power supply system 1 includes a controller
9 and a relay unit 10 to control the operation of the DC
devices 5 in the home.
Connected to the control unit 7 is the AC distribution
board 11 to distribute AC power via an AC power line 12.
Further, connected to the AC distribution board 11 are the
AC power source 2 and the AC devices 6 via an AC power line
12a. The control unit 7 is connected to the commercial AC
power source 2 via the AC distribution board 11. Also, the
control unit 7 is connected to the solar cell 3 via a DC
power line 13a and connected to the fuel cell 4 via a DC
power line 13b. The control unit 7 functioning as a
converter receives an AC power from the AC distribution
board 11, and converts the AC power into a specific DC power.
Also, the control unit 7 receives a DC power from the
solar cell 3 or the fuel cell 4, and converts the DC power
into a specific DC power. Further, the control unit 7
outputs the converted DC power to the DC distribution board
8 via a DC power line 14, or outputs the converted DC power
to the storage battery 16 via a DC power line 15 to store
the power. Besides, the control unit 7 receives the DC
power stored in the storage battery 16, converts the DC
power into a specific DC power, and outputs the converted DC
power to the DC distribution board 8 via the DC power line
14.
Further, the control unit 7 may not only receive an AC
power from the AC distribution board 11, but also convert a
DC power of the solar cell 3 or the storage battery 16 into
an AC power to be supplied to the AC distribution board 11.
In other words, the control unit 7 also functioning as an
inverter receives a DC power from the solar cell 3, the fuel
cell 4 and the storage battery 16, and converts the DC power
into a specific AC power. Then, the control unit 7 outputs
(discharges) the converted AC power to the power, line 51 via
the AC power line 12 and the AC distribution board 11.
Further, the control unit 7 communicates data with the DC
distribution board 8 via a signal line 17.
The DC distribution board 8 is a kind of breaker for
DC power. The DC distribution board 8 distributes the DC
power inputted from the control unit 7, and outputs the
distributed DC power to the controller 9 via a DC power line
18, or outputs the distributed DC power to the relay unit 10
via a DC power line 19. Further, the DC distribution board
8 exchanges data with the controller 9 via a signal line 20,
or exchanges data with the relay unit 10 via a signal line
21.
The controller 9 is connected to a plurality of the DC
devices 5. The DC devices 5 are connected to the controller
9 via DC supply lines 22, each capable of carrying both DC
power and data. Each of the DC supply lines 22 transports
both power and data to each of the DC devices 5 via a pair
of wires by so-called power line carrier communications in
which a communications signal for transferring data using
high-frequency carrier waves is superimposed on a DC voltage
for operating the DC devices 5.
The controller 9 obtains the DC power for the DC
devices 5 via the DC power line 18, and , understands how to
control which of the DC devices 5 based on an operation
command obtained from the DC distribution board 8 via the
signal line 20. Then, the controller 9 outputs the DC
voltage and the operation command to target DC devices 5 via
the DC supply lines 22 to control the operation of the DC
devices 5.
The controller 9 is connected via the DC supply line
22 to switches 23 used when switching the operations of the
DC devices 5 in the home. In addition, the controller 9 is
connected via the DC supply line 22 to a sensor 24 for
detecting radio waves originating from, e.g., an infrared
remote controller. Thus, by the operation of the switches
23 or the detection of the sensor 24 in addition to the
operation commands from the DC distribution board 8, the
operations of the DC devices 5 are controlled through the
communications signal flowing through the DC supply lines 22
on the basis of the detection results.
Connected to the relay unit 10 is a plurality of the
DC devices 5 via individual DC power lines 25. The relay
unit 10 obtains the DC power for the DC devices 5 via the DC
power line 19, and understands which of the DC devices 5
will be operated based on an operation command obtained from
the DC distribution board 8 via the signal line 21. Then,
the relay unit 10 relays on and off the power supply to
target DC devices 5 via the DC power lines 25 to control the
operation of the DC devices 5. Further, the relay unit 10
is connected to a plurality of switches 2 6 for manually
operating the DC devices 5. By turning on and off the power
supply through the DC power lines 25 in the relay unit 10
according to the operation of the switches 2 6, the DC
devices 5 are controlled.
The DC distribution board 8 is connected to a DC
outlet 27 installed in the house in the form of, e.g., a
wall outlet or floor outlet via a DC power line 28. If a
plug of a DC device (not shown) is inserted into the DC
outlet 27, it is possible to directly supply a DC power to
the device.
Further, a power meter 2 9 is provided between the
commercial power source 2 and the AC distribution board 11,
and capable of remotely reading the usage of the commercial
power source 2 in the dwelling unit in which the AC
distribution board 11 is installed. The power meter 29 has,
e.g., a power line carrier communications or wireless
communications function in addition to the function of
remotely reading the usage of the commercial power source.
The power meter 29 transmits the reading results to a power
company or the like through the power line carrier
communication or wireless communication.
The power supply system 1 is provided with a network
system 30 to allow various devices in the home to be
controlled by the network communications. The network
system 30 includes a home server 31 serving as a control
unit of the network system 30. The home server 31 is
connected to a management server 32 on the outside of the
house through a network N such as the Internet, and also
connected to a household device 34 via a signal line 33.
Further, the home server 31 is operated by the DC power
obtained from the DC distribution board 8 via a DC power
line 35.
The home server 31 is connected to a control box 36
via a signal line 37, the control box 36 managing the
operation control of various devices in the home through the
network communications. The control box 36 is connected to
the control unit 7 and the DC distribution board 8 via the
signal line 17, and also configured to directly control the
DC device 5 via a DC supply line 38.
The control box 36 is connected to, e.g., a gas/water
meter 39 capable of remotely reading the amount of gas or
water used, and an operation panel 40 of the network system
30. The operation panel 40 is connected to a monitoring
device 41 consisting of, e.g., an intercom, sensor or camera.
Further, in this embodiment, the operation panel 40 is a
display device with a monitor, and various pieces of
information are displayed on the monitor of the operation
panel 40.
If operation commands related to various devices in
the home are inputted through the network N, the home server
31 notifies instructions to the control box 36, and controls
the control box 36 such that various devices are operated in
accordance with the operation commands. Further, the home
server 31 is configured to provide various pieces of
information obtained from the gas/water meter 39 to the
management server 32 through the network N. Furthermore,
when receiving from the operation panel 40 that there is an
error detected by the monitoring device 41, the home server
31 provides the received information to the management
server 32 through the network N.
Further, as shown in FIG. 1, the multiple dwelling
house is provided with a control apparatus 56 for
controlling the control unit 7 and the like of each dwelling
unit, and the control apparatus 56 is connected to
communicate with a plurality of the control units 7. That
is, with respect to the power management, the control
apparatus 56 serves as a master device for collectively
managing the power control in the plural control units 7,
and the control unit 7 serves as a slave device.
Next, a configuration of enabling the sale of electric
power in the power distribution system 50 of the present
invention in which the power can be transferred between
dwelling units of the multiple dwelling house will be
described in detail.
As described above, under certain conditions, the
control unit 7 converts a DC power supplied from the
distributed power source 54 into an AC power, and supplies
the AC power to the power line 51. In this case, the
certain conditions in which the power is supplied from the
control unit 7 to the power line 51 are that the distributed
power source 54 can generate surplus power.
That is, if the distributed power source 54 provided
in each dwelling unit can supply, to the control unit 7,
power more than the power required to be supplied to the
load devices 6 and 55 in the dwelling unit in which the
distributed power source 54 is installed, the surplus power
is supplied from the distributed power source 54 to the
control unit 7.
Therefore, the surplus power from one dwelling unit is
supplied to another dwelling unit via the power line 51.
Hereinafter, a flow of the operation of the control unit 7
when selling and purchasing the surplus power between the
dwelling units will be described assuming that the power
distribution apparatus 52 of a dwelling unit supplying (i.e.,
selling) surplus power is a power selling system A, and the
power distribution apparatus 52 of a dwelling unit receiving
{i.e., purchasing) surplus power is a power purchasing
system B. Further, the surplus power may be supplied to one
power purchasing system B from a plurality of power selling
systems A, and the surplus power may be supplied to a
plurality of power purchasing systems B from one power
selling system A.
FIG. 3 is a flowchart showing the flow of the
operation of the control unit 7 of the power selling system
A when selling the surplus power between the dwelling units.
A series of operations shown in FIG. 3, for example, may be
started manually, or may be started automatically based on a
command signal from the control apparatus 56.
Referring to FIG. 3, firstly, the control unit 7
obtains information on an amount of the power demanded by
the AC devices 6 through the AC distribution board 11 (step
SI) . Subsequently, the control unit 7 obtains information
on an amount of the power demanded by the load devices 55
(step S2) . For example, the information on the amount of
the power demanded by the load devices 55 can be obtained
based on the power detection results of the controller 9 and
the relay unit 10 connected to the DC devices 5. That is,
the information on the amount of the demanded power includes
information relating to the power consumed in the load
devices 6 and 55.
Then, the control unit 7 determines whether the
distributed power source 54 can supply the surplus power
(step S3). Specifically, the control unit 7 obtains
information on an amount of the power that can be supplied
from the distributed power source 54, and determines whether
the distributed power source 54 can sufficiently supply the
power required for the load devices 6 and 55 in the power
selling system A on the basis of the information obtained in
steps SI and S2. In other words, if the amount of the power
that can be supplied from the distributed power source 54 is
greater than the total amount of the demanded power, the
control unit 7 determines that the distributed power source
54 of the power selling system A can supply the surplus
surplus power.
If it is determined in step S3 that the distributed
power source 54 can supply the surplus power, the
determination result is notified to the control apparatus 56,
and the power is sold from the distributed power source 54
of the power selling system 7A according to the instructions
of the control apparatus 56 (step S4). That is, the surplus
power from the power selling system A is supplied to the
power line 51.
In this embodiment, when the surplus power is supplied
from the power selling system A, the control unit 7 outputs,
to the control apparatus 56, information on the power source
which has supplied the power (step S5). In other words, the
information on the surplus power supply source, i.e., which
of the solar cell 3, the fuel cell 4 and the storage battery
16 has supplied the surplus power, is outputted as data from
the control unit 7 to the control apparatus 56.
In this way, after the operations of steps S4 and S5 have
been performed, or if it is determined in step S3 that the
distributed power source 54 cannot supply the surplus power,
the series of operations shown in Fig. 3 is ended.
Next, a flow of the operation of the control apparatus
5 6 when the surplus power is sold between' the dwelling units
will be described.
FIG. 4 is a flowchart showing a flow of a billing-
related operation of the control apparatus 56 when the
surplus power is sold between the dwelling units.
Referring to FIG. 4, firstly, the control apparatus 56
measures an amount of the power traded (transferred) between
the dwelling units (i.e., between the power selling system A
and the power purchasing system B) {step Sll) . The amount
of power traded between the dwelling units can be measured
by using the power meter 29 capable of measuring the power
supplied to each of the power distribution apparatuses 52
from the power line 51.
Subsequently, in this embodiment, the control
apparatus 5 6 obtains information on the power source which
has supplied the surplus power from the power selling system
A (step S12) . That is, the output data in step S5 of FIG. 3
is inputted to the control apparatus 56, and, accordingly,
the control apparatus 56 obtains information on which of the
solar cell 3, the fuel cell 4 and the storage battery 16 has
supplied the surplus power.
Then, the control apparatus 56 bills the power
distribution apparatus 52 which has purchased the power
(i.e., the power purchasing system B) (step S13) . In this
embodiment, a billing amount charged to the power purchasing
system is calculated by multiplying the amount of the traded
power by a coefficient depending on the surplus power supply
source. In other words, the billing amount is different
according to whether the surplus power supply source is the
solar cell 3, the fuel cell 4, or the storage battery 16.
Accordingly, the amount of the power supplied to the power
purchasing system B from the distributed power source 54 of
the power selling system A is billed differently according
to the type of the power source used to supply the surplus
power to the power purchasing system B.
As described above, in this embodiment, it is
configured to manage billing or the like associated with the
transfer of power between the power distribution apparatuses
52 on the basis of the measurement results of the power
meter 2 9 which measures the amount of the power supplied to
each of the power distribution apparatuses 52 from the power
line 51. Further, in this embodiment, in step S3 of FIG. 3
described above, it is determined whether the distributed
power source 54 can supply the surplus power on the basis of
the information relating to the power supplied by the
distributed power source 54 and the power consumption of the
load devices 6 and 55, thereby managing the transfer of
power between the power distribution apparatuses.
Further, in this embodiment, it is configured such
that the control apparatus 56 controls a plurality of the
control units 7 to manage the transfer of power between the
power distribution apparatuses 52 (i.e., the power selling
system A and the power purchasing system B) . Specifically,
for example, the control apparatus 56 bills each of the
power distribution apparatuses 52 by setting a difference
between billing for the amount of the power supplied from
the commercial AC power source 2 to the power distribution
apparatus 52 and billing for the amount of the power
supplied from the distributed power source 54 of the power
selling system A to the power distribution apparatus 52.
Furthermore, in this embodiment, it is configured such
that the billing-related information is displayed on the
operation panel 40 with the monitor. For example, the
control apparatus 56 is configured to receive the
information on whether the surplus power can be supplied, an
amount of the surplus power that can be supplied, the
surplus power supply source and the like from the power
selling system A, and, in the power purchasing system B,
display the information on the operation panel 40 through
the control unit 7 and the control box 3 6.:
Further, it is configured to allow a resident of the
dwelling unit, in which the power purchasing system B is
provided, to select whether to purchase the power from which
power source of the power selling system A using the
operation panel 40 of the power purchasing system B.
Besides, it is configured such that the power can be
purchased from the power selling system A by operating the
operation panel 4 0 on which the billing information is
displayed. In addition, the operation panel 4 0 may display
the information on the power being sold from a plurality of
power selling systems A.
Further, the present embodiment, as shown in FIG. 1,
is characterized in that a storage device 57 for storing the
power flowing to the commercial AC power source 2 from the
distributed power source 54 is connected to and provided in
the power line 51 such that the surplus power does not flow
toward the commercial AC power source 2 on the outside of
the multiple dwelling house, and a sensor 60 is connected to
the power line 51 serving as a lead-in wire to the multiple
dwelling house from the commercial AC power source 2. The
characteristic configuration of the present embodiment will
be described below in more detail.
The storage device 57 that can be charged and
discharged includes an AC/DC converter 58 serving as a
converter and inverter, and a storage battery 59 connected
to the power line 51 through the AC/DC converter 58 . The
AC/DC converter 58 serving as a converter is connected to
the power line 51. In case of storing power in the storage
device 57 (charging the storage device 57), the AC/DC
converter 58 acquires an AC power from the power line 51,
converts the acquired AC power into a specific DC power, and
supplies the converted DC power to the storage battery 59.
The storage battery 59 connected to the AC/DC converter 58
stores the DC power supplied from the AC/DC converter 58.
Further, in case of discharging power from the storage
device 57, the storage battery 59 supplies the stored DC
power to the AC/DC converter 58. In this case, the AC/DC
converter 58 also serves as an inverter to convert the DC
power discharged from the storage battery 59 into a specific
AC power, and supplies the converted AC power to the power
line 51. The charging and discharging of the storage device
57 are controlled by the control apparatus 56 serving as a
maser power management device.
In this embodiment, the charging and discharging of
the storage device 57 are controlled on the basis of the
current detected by the sensor 60 connected to the power
line 51. The sensor 60 is provided in the lead-in wire to
the multiple dwelling house, and particularly provided
between the commercial AC power source 2 and the power
distribution part 53 including a plurality of the power
distribution apparatuses 52. That is, the sensor 60 serves
as a current meter for detecting a reverse power flow.
The sensor 60 may detect the reverse power flow of
surplus power by detecting the current (i.e., current value)
flowing in the power line 51. The sensor 60 is connected to
the control apparatus 56, and information on the detection
results is outputted from the sensor 60 to the control
apparatus 56. The storage device 57 is controlled by the
control apparatus 56 on the basis of the detection results
of the sensor 60. Hereinafter, a flow of the operation of
the control apparatus 56 when the reverse power flow is
suppressed using the storage device 57 will be described
with reference to FIG. 5.
As shown in FIG. 5, first, the control apparatus 56
determines whether the reverse power flow has been detected
based on the detection results of the sensor 60 (step S21).
A series of operations subsequent to step S21 shown in FIG.
5 is not performed until it is determined in step S21 that
the reverse power flow has been detected.
If it is determined that the reverse power flow has
been detected in step S21, the control apparatus 56 outputs
a signal for initiating the storage of power to the storage
device 57, and the storage device 57 is operated to initiate
the charging (storage of power) (step S22). That is, if the
reverse power flow occurs due to the supply of surplus power
from the power selling system A to the power line 51, the
surplus power is stored in the storage battery 59 of the
storage device 57. In the manner as described above, the
surplus power is stored in the storage device 57 and, thus,
it is possible to suppress the reverse power flow from the
distributed power source 54 of the power selling system A to
the commercial AC power source 2.
Subsequently, the control apparatus 56 determines
whether to terminate the charging of the storage device 57
(step S23) . Preferably, the determination on whether to
terminate the charging of the storage device 57 in step S23
is made based on whether the reverse power flow will not
occur even when the charging of the storage device 57 is
terminated.
In other words, it is preferred to terminate the
charging of the storage device 57 if it is determined that
the reverse power flow does not occur even after the
termination of the charging of the storage device 57, based
on the amount of power that can be supplied from the
distributed power source 54 of the power distribution
apparatus 52, the current (i.e., current value) flowing in
the power line 51 or the like. In addition, the
determination on whether to terminate the charging of the
storage device 57 may be made based on whether the storage
device 57 is fully charged.
If it is determined to terminate the charging of the
storage device 57 in step S23, the control apparatus 56
outputs a signal for initiating the discharging of the
storage device 57, and the storage device 57 is operated to
initiate the discharging (step S24) . Thus, the surplus
power stored in the storage device 57 is supplied to the
power line 51, and the discharged power is supplied to at
least one of the load devices 6 and 55. In other words, it
is configured to minimize the power supplied from the
commercial AC power source 2 to the power distribution
apparatuses 52. Further, a series of operations subsequent
to step S23 shown in FIG. 5 is not performed until it is
determined to terminate the charging of the storage device
57 in step S23.
Then, in this embodiment, the control apparatus 56
determines whether the discharged power of the storage
device 57 is insufficient or not (step S25). Specifically,
it is determined in step S25 that the discharged power of
the storage device 57 is insufficient if the discharged
power of the storage device 57 is equal to or less than a
predetermined power.
If it is determined in step S25 that the discharged
power of the storage device 57 is insufficient, the control
apparatus 56 limits the power supply to the load devices 6
and 55 of specific power distribution apparatuses 52 among
the plurality of power distribution apparatuses 52 (step
S26) . In this embodiment, it is configured to cut off the
power supply to the load devices 6 and 55 of the specific
power distribution apparatuses 52. In this way, it is
configured to minimize the power supplied from the
commercial AC power source 2 to the power distribution
apparatuses 52. Preferably, the load devices 6 and 55 to
which the power supply is cut off in step S2 6 may be
designated preferentially by a user
According to the present embodiment, it is possible to
obtain the following effects:
(1) The power line 51 connected to the commercial AC
power source 2 is connected to a plurality of the power
distribution apparatuses 52, and each of the power
distribution apparatuses 52 has the load devices 6 and 55 to
which the power is supplied and the distributed power source
54 which can supply the power to the load devices 6 and 55.
Further, in the power distribution system 50 in which the
power can be supplied from the distributed power source 54
of at least one of the power distribution apparatuses 52 to
the load devices 6 and 55 of another power distribution
apparatus 52, the power line 51 is connected and provided
with the storage device 57 storing the power flowing to the
commercial AC power source 2 from the distributed power
source 54. Accordingly, the power can be transferred
between the power distribution apparatuses 52 connected to
the power line 51, the power line 51 also being connected to
the commercial AC power source 2. By storing the power in
the storage device 57, it is possible to suppress the
reverse power flow to the commercial AC power source 2 from
the distributed power source 54 of the power distribution
apparatus 52.
(2) Between the commercial AC power source 2 and the
power distribution part 53 constituted by a plurality of the
power distribution apparatuses 52, there is provided the
sensor 60 connected to the power line 51 to detect the
current. Accordingly, based on the detection results (i.e.,
the current flowing in the power line 51) of the sensor 60,
the storage device 57 is controlled. Thus, the reverse
power flow can be suppressed automatically based on the
current flowing in the power line 51 (i.e., the current
value of the power line 51).
(3) By discharging power from the' storage device 57,
the discharged power is supplied to at least one of the load
devices 6 and 55. Accordingly, since the storage device 57
can also supply the power to the load devices 6 and 55 of
the power distribution apparatus 52, it is possible to
reduce the power (i.e., purchased power) supplied from the
commercial AC power source 2. In addition, by discharging
power from the storage device 57, the storage capacity (i.e.,
available storage capacity which is variable with respect to
the maximum storage capacity) of the storage device 57 can
be recovered.
(4) On the basis of the discharged power being
supplied from the storage device 57, the power supply to the
load devices 6 and 55 of specific power distribution
apparatuses 52 among the power distribution apparatuses 52
may be limited. Accordingly, it is possible to reduce the
power (i.e., purchased power) supplied from the commercial
AC power source 2. Specifically, if the amount of the power
discharged from the storage device 57 is low, the power
supply to the load devices 6 and 55 of the specific power
distribution apparatuses 52 is limited. Therefore, it
becomes easier for the distributed power source 54 or the
storage device 57 to feed the power required for the load
devices 6 and 55 other than those in which the power supply
is not limited, thereby reducing the power supply from the
commercial AC power source 2.
(5) On the basis of the discharged power being
supplied from the storage device 57, the power supply to the
load devices 6 and 55 of specific power distribution
apparatuses 52 among the power distribution apparatuses 52
may be cut off. Accordingly, in addition to the effect
described in (4), it is possible to surely reduce the power
supply from the commercial AC power source 2.
(6) Each of the power distribution apparatuses 52 is
provided in each dwelling unit of the multiple dwelling
house. Accordingly, the power can be transferred between
the dwelling units of the multiple dwelling house. In
addition, as described in (1), it is possible to suppress
the reverse power flow from the multiple dwelling house.
(7) The power distribution system 50 is provided with
the power meter 29 serving as a power measuring sensor to
measure the amount of the power being supplied to each of
the power distribution apparatuses 52 from the power line 51.
On the basis of the measurement results (the amount of the
power being supplied to each of the power distribution
apparatuses 52 from the power line 51) of the power meter 29,
the transfer of the power between the power distribution
apparatuses 52 is managed. Accordingly, the transfer of the
power can be managed between the power distribution
apparatuses 52 and the sale of electric power can be
achieved between the power distribution apparatuses 52.
(8} In addition, based on the information relating to
the power consumption of the load devices 6 and 55 and the
power supplied by the distributed power source 54 in the
power distribution apparatus 52, the transfer of the power
between the power distribution apparatuses 52 is managed.
Accordingly, the transfer of the power can be finely and
minutely managed between the power distribution apparatuses
52 and the sale of electric power can be achieved between
the power distribution apparatuses 52.
(9) The control unit 7 for controlling the transfer of ¦
the power through the power line 51 is provided in each of
the power distribution apparatuses 52, and the power
distribution system 50 includes the control apparatus 56
that is connected to communicate with the plural control
units 7. Further, based on the measurement results of the
power meters 29, the transfer of the power is managed
between the power distribution apparatuses 52. In this case,
the plural control units 7 are controlled by the control
apparatus 56, thereby collectively managing the transfer of
power between the power distribution apparatuses 52.
(10) The power distribution apparatus 52 to which the
power has been supplied (i.e., the power purchasing system
B) is billed based on the supplied power. A difference is
set between billing for the amount of the power supplied
from the commercial AC power source 2 to the power
purchasing system B and billing for the amount of the power
supplied from the distributed power source 54 to the power
purchasing system B. Therefore, by setting the billing
amount for the power supplied from the commercial AC power
source 2 to the power purchasing system B to be greater than
the billing amount for the power supplied from the
distributed power source 54 to the power purchasing system B,
the user to be billed can be encouraged to purchase power
from the distributed power source 54.
(11) The power distribution system 50 includes the
operation panel 40 with the monitor serving as a display
device for displaying the billing-related information. Thus,
the user to be billed can determine whether to purchase
power from which power source of the commercial AC power
source 2 and the distributed power source 5 4 of the power
selling system A by referring to the billing-related
information displayed on the operation panel 40.
(12} The distributed power source 54 may include
multiple types of power sources. The information for
distinguishing the power source which has supplied the power
among the multiple types of power sources is outputted as
data to the control apparatus 56 from the power distribution
apparatus 52 (i.e., the power selling system A) having the
distributed power source 54 which has supplied the power.
Accordingly, the control apparatus 56 can obtain the data
and utilize the information for distinguishing the multiple
types of power sources in various controls.
(13) The power distribution system to which the power
has been supplied (i.e., the power purchasing system B) is
billed based on the power supplied from the distributed
power source 54. The amount of the power supplied to the
power purchasing system B from the distributed power source
54 of the power selling system A is billed differently
according to the type of the power source used to supply the
power to the power purchasing system B. Accordingly, for
example, by setting the billing amount for the power
supplied from the distributed power source 54 using the
solar cell 3 to be smaller than the billing amount for the
power supplied from the distributed power source 54 using
the storage battery 16, the user to be billed can be
encouraged to purchase power from the distributed power
source 54 using the solar cell 3.
(Second Embodiment)
Next, a second embodiment in which the control of the
storage device 57 of the first embodiment is modified will
be described. Further, the same reference numerals are
assigned to the same components as those of the first
embodiment, and a description thereof will be omitted or
simplified.
As shown in FIG. 6, in this embodiment, no sensor 60
is provided in the multiple dwelling house, and the control
apparatus 56 controls the storage device 57 based on a
command signal inputted from the outside of the multiple
dwelling house. In other words, the control apparatus 56 is
connected to power management facilities 61 of a power
company or the like, the control apparatus 56 capable of
communicating with the power management facilities 61, and
suppressing the reverse power flow according to a command
signal from the power management facilities 61. Hereinafter,
a flow of the operation of the control apparatus 56 when the
reverse power flow is suppressed by the storage device 57 in
this embodiment will be described with reference to FIG. 7.
As shown in FIG. 7, first, the control apparatus 56
determines whether the command signal for instructing to
suppress the reverse power flow has been received from the
power management facilities 61 (step S31) . A series of
operations subsequent to step S31 shown in FIG. 7 is not
performed until it is determined in step S31 that the
command signal for instructing to suppress the reverse power
flow has been received.
If it is determined in step S31 that the command
signal for instructing to suppress the reverse power flow
has been received, similarly to step S22, the control
apparatus 56 outputs a signal for initiating the storage of
power to the storage device 57, and the storage device 57 is
operated to initiate the charging (storage of power) (step
S32). In the manner as described above, the surplus power
is stored in the storage device 57 and, thus, it is possible
to suppress the reverse power flow from the distributed
power source 54 of the power selling system A to the
commercial AC power source 2 .
Subsequently, the control apparatus 56 determines
whether the storage device 57 is fully charged (step S33) .
If it is determined in step S33 that the storage device 57
is fully charged, in this embodiment, the control apparatus
56 controls power generation of a specific power generation
source (e.g., the solar cell 3 and the fuel cell 4 in the
power selling system A) (step S34) . Specifically, in step
S34, the power generation of the power source which has
supplied the surplus power in the power selling system A is
limited.
In this way, the overcharging of the storage device 57
is suppressed. In this embodiment, in step S34, the power
generations of a plurality of the distributed power sources
54 are limited sequentially based on priorities that are set
in advance. Preferably, the priorities may be changed
appropriately based on contracts between users of the power
distribution apparatuses 52 (i.e., residents of the multiple
dwelling house) and a manager of the power distribution
apparatuses 52 (i.e., a manager of the multiple dwelling
house) or the like.
Subsequently, similarly to step S23, the control
apparatus 56 determines whether to terminate the charging of
the storage device 57 (step S35) . Preferably, the
determination on whether to terminate the charging of the
storage device 57 in step S23 is made based on whether the
reverse power flow will not occur despite the termination of
the charging of the storage device 57. If it is determined
to terminate the charging of the storage device 57 in step
S35, similarly to step S24, the control apparatus 56
controls the storage device 57 to initiate the discharging
thereof (step S36).
Further, if it is determined not to terminate the
charging of the storage device 57 in step S35, the
operations of steps S33 to S35 are repeated. In addition,
after performing the operation of step S36, the control
apparatus 56 may perform the operations of steps S25 and S26
as described in the first embodiment.
According to the present embodiment, in addition to
the effects described in (1) and (6) to (13), the following
effects can be obtained.
(14) The storage device 57 is controlled based on the
command signal outputted from the power management
facilities 61 managing the power of the commercial AC power
source 2. Accordingly, in a state where the command signal
for instructing to suppress the reverse power flow is not
outputted from the power management facilities 61, a power
is not charged in the storage device 57, and can be
reversely flowed from the power distribution apparatuses 52
to the outside of the multiple dwelling house. This makes
the sale of electric power possible.
(15) Based on the charging state of the storage device
57, the power generation of the distributed power source 54
of the power selling system A is limited. Accordingly, if
the storage device 57 is fully charged, the power generation
of the distributed power source 54 is limited. Thus, it is
possible to suppress the reverse power flow while preventing
the storage device 57 from being overcharged.
(16) Based on the priorities that are set in advance,
the power generations of a plurality of the distributed
power sources 54 are limited sequentially. Accordingly, it
is possible to control the power generations of a plurality
of the distributed power sources 54 in the order desired.
With respect to the present invention as described in
the above embodiments, various design changes can be made
without deviating from the scope of the present invention.
For example, the first and second embodiments described
above may be modified as follows, and the following
modifications may be carried out in combination with each of
the above embodiments.
• In the above-described embodiments, the distributed
power source 54 is constituted by the solar cell 3, the fuel
cell 4 and the storage battery 16. However, the distributed
power source 54 may not include all of them, and may include
any power sources other than them.
• In the above-described embodiments, each of the power
distribution apparatuses 52 is provided in the dwelling unit
of the multiple dwelling house. However, the present
invention may be applied to infrastructures other than the
multiple dwelling house. Specifically, for example, each of
the power distribution apparatuses 52 may be provided in an
office, shop or the like.
• In the above-described embodiments, the operation
panel 40 equipped with the monitor is a display device for
displaying the billing-related information. However, a
monitor (not shown) may be provided as a display device
separately from the operation panel 40.
• In the above-described embodiments, the power meter
2 9 is a power measuring meter for measuring the amount of
the power being supplied to each of the power distribution
apparatuses 52 from the power line 51. However, a power
measuring meter may be provided separately from the power
meter 29.
• In the above-described embodiments, the control
apparatus 56 controls the plural control units 7 to manage
the transfer of power between the power distribution
apparatuses 52. However, the transfer of power between the
power distribution apparatuses 52 may be managed without
using the control apparatus 56 as a master management device.
That is, any one of the control units 7 may perform the same
operation as the control apparatus 56.
¦ In the above-described embodiments, the control unit
7 is a power supply control device for controlling the
transfer of power through the power line 51. However, a
device other than the control unit 7 may serve as a power
supply control device.
Hereinafter, a third embodiment of the present invention
will be described with reference to FIGS. 8 to 12. In a
power distribution systems in accordance with the third
embodiment of the present invention, as shown in FIG. 8,
unlike the power distribution system shown FIG. 2 in
accordance with the first and second embodiments of the
present invention, the control apparatus 56 and the storage
battery 16 serving as a distributed power source are not
provided, and the control unit 7 has characteristic
configuration and function as will be described below. In
FIG. 8, the same reference numerals are assigned to the same
or similar components as those of FIG. 2, a description
thereof will be omitted, and different parts will be mainly
described.
In a power distribution system 1 in accordance with
the present embodiment, for example, information about the
sale of electric power (reverse power flow) is transmitted
from the management server 32 to the home server 31 through
the network N. The home server 31 outputs the information
about the sale of electric power (reverse power flow) to the
control unit 7 through the control box 36.
Next, a specific configuration of a control unit 7' in
accordance with this embodiment will be described.
As shown in FIG. 9, the control unit 7' includes, a
controller 151, a first DC/DC converter {hereinafter,
referred to as "first converter") 155, a second DC/DC
converter (hereinafter referred to as "second converter")
156, a battery converter 157, a bi-directional converter 160,
a battery 154, and a reverse flow power detection circuit
150.
The first converter 155 converts a DC power (solar
power Ppv) inputted from the solar cell 3 into a desired DC
power, and outputs the converted DC power to the DC
distribution board 8. Specifically, the first converter 155
includes, as shown in FIG. 10, an input voltage detection
circuit 161 detecting a voltage at a side of the solar cell
3, an output voltage detection circuit 162 detecting a
voltage at a side of the DC distribution board 8, an input
current detection circuit 163 detecting a current value at
the side of the solar cell 3, a power circuit 164 for power
conversion, a CPU 165 controlling the power circuit 164, and
a non-volatile memory 165a being accessed by the CPU 165.
The CPU 165 appropriately controls the power circuit
164 in accordance with a program stored in the memory 165a.
Specifically, according to the program, MPPT control
described in the above-mentioned background is executed. In
terms of power generation efficiency of the solar cell 3, it
is preferable that MPPT control is executed all the time.
The power circuit 164 converts a power supplied from
the solar cell 3 into a desired power, and outputs the
converted power to the DC distribution board 8, based on a
control signal from the CPU 165. According to the MPPT
control, as described with reference to FIG. 14 in the above
background, the CPU 165 controls an output power Pout (solar
power Ppv) of the solar cell to a maximum output power Pmax
thereof through the power circuit 164.
An input voltage and input current of the power
circuit 164 are detected by the input voltage detection
circuit 161 and the input current detection circuit 163, and
an output voltage of the power circuit 164 is detected by
the output voltage detection circuit 162. These detection
results are outputted to the CPU 165. Thus, the CPU 165
determines whether an input power has been properly
converted into an output power. Further, the power circuit
164 includes a plurality of switch elements and the like.
Further, a command signal regarding the output power Pout of
the power circuit 164 is inputted to the CPU 165 from the
controller 151.
The second converter 156 converts a DC power inputted
from the fuel cell 4 into a desired DC power, and outputs
the converted DC power to the DC distribution board 8. A
specific configuration of the second converter 156 is almost
the same as the first converter 155 shown in FIG. 10. The
second converter 156 is different from the first converter
155 in that, as shown in FIG. 10, power generation rules of
the fuel cell 4 are stored in the memory 165a of the second
converter 156. The power generation rules prescribe a
maximum output power, or prohibit a steep change in power
generation. By carrying out the power generation according
to the power generation rules, it is possible to extend the
life of the fuel cell 4 while increasing the power
generation efficiency of the fuel cell 4.
The battery converter 157 and the battery 154 are
connected to the DC power line 14 via a battery connection
line 153. The battery converter 157 converts a power of the
DC power line 14 into a desired power and stores in the
battery 154, or converts the power charged in the battery
154 into a desired power and discharges it to the DC power
line 14. The battery converter 157 is a bi-directional
DC/DC converter.
A specific configuration of the battery converter 157
is almost the same as the first converter 155 shown in FIG.
10, except that the battery converter 157 can output a power
in both directions toward the battery 154 and the DC power
line 14. Further, the battery converter 157 outputs the
detection result of the input voltage detection circuit 161
to the controller 151. The controller 151 recognizes a
battery voltage Vb of the battery 154 based on the detection
result.
The bi-directional converter 160 is provided in a
DC/AC connection line 12. The bi-directional converter 160
includes an AC/DC converter 158 and a DC/AC converter 159.
The DC/AC converter 159 converts a DC power from the DC
power line 14 into an AC power (output current iout) , and
supplies the converted AC power to the AC power line 12a.
Further, the AC/DC converter 158 converts an AC power from
the AC power line 12a into a DC power (output current lout},
and supplies the converted DC power to the DC power line 14.
The AC/DC converter 158 and the DC/AC converter 159 may
convert an input power into a desired output power. A
specific configuration of each of the AC/DC converter 158
and the DC/AC converter 159 is almost the same as the first
converter 155 shown in FIG. 10 excluding that the power
circuit 164 converts power between DC and AC power.
The AC/DC converter 158 is controlled by the
controller 151 and also outputs the detection result of the
output voltage detection circuit 162 (see FIG. 10) to the
controller 151. The controller 151 recognizes a voltage V
of the DC power line 14 based on the detection result. In
this way, by providing the bi-directional converter 160 in
the DC/AC connection line 12, an AC power can be converted
into a DC power to be transmitted to the DC power line 14,
or a DC power can be converted into an AC power to be
transmitted to the AC power line 12a.
In this case, a DC power generated by the solar cell 3
may be supplied to the DC devices 5. Thus, for example,
compared to a system in which the power generated by the
solar cell 3 needs to be converted into an AC power, power
loss in power conversion can be reduced, and transmission
efficiency is good. However, since the power generation by
the solar cell 3 is influenced by the weather and time, it
is difficult to supply stable power to the DC devices 5. On
the other hand, since an AC power is generated by, e.g., a
power company, stable power transmission from the AC power
source 2 can be expected.
Therefore, if the power generated by the solar cell 3
is insufficient, the AC power from the AC power source 2 can
be converted into a DC power to be supplied to the DC
devices 5, thereby stably supplying the DC power to the DC
devices 5. Also, on the contrary, if it is determined that
the amount of the power generated by the solar cell 3
exceeds the amount of the power consumed in the DC devices 5,
a DC power of the solar cell 3 may be converted into an AC
power to be supplied to the AC devices 6. Alternatively,
the sale of electric power may be achieved by causing the
reverse power flow toward the AC power source 2, i.e., the
power company.
The reverse flow power detection circuit 150 detects a
power supplied to the AC power line 12a between the AC power
source 2 and the AC distribution board 11, particularly, a
power reversely flowing to the AC power source 2 from the AC
distribution board 11. The detection results are outputted
to the controller 151.
The controller 151 recognizes the reverse flow power
based on the detection results from the reverse flow power
detection circuit 150, and also calculates the amount of the
power Wh by time integrating the reverse flow power. In
this case, as shown in FIG. 8, the information on the
reverse flow power is periodically transmitted from the
management server 32 to the control unit 7' through the
network N, the home server 31 and the control box 36. The
controller 151 receives the information about the reverse
flow power through the signal line 17.
The reverse flow of the power is not allowed
indefinitely all the time. For example, the reverse flow of
the power is prohibited every predetermined period, or the
allowable amount of reverse flow power is limited. If the
reverse flow of the power is prohibited, it is necessary to
prevent the power from reversely flowing. In this case, the
allowable amount of the reverse flow power is set as a
threshold value Whl. The information about the reverse flow
power includes information such as the threshold value Whl.
The controller 151 updates (stores in a memory 151a) the
information such as the threshold value Whl whenever
receiving the information about the reverse flow power, and
performs control based on the latest information afterwards.
The controller 151 prohibits the reverse flow of power
or limits the allowable amount of reverse flow power Wh
according to the above information. In case of prohibiting
the reverse flow of the power, the controller 151 charges
the power equivalent to the power detected by the reverse
flow power detection circuit 150 in the battery 154 through
the battery converter 157 from the DC power line 14.
Accordingly, it is possible to prohibit the reverse flow of
the power without affecting the voltage V of the DC power
line 14.
In case of limiting the amount of reverse flow power
Wh, the controller 151 calculates the amount of the power Wh
by time integrating the power for a predetermined period of
time. Then, when the calculated amount of the power Wh
reaches the threshold value Whl, the controller 151 charges
the reverse flow power in the battery 154 through the
battery converter 157 in the same manner as described above,
thereby limiting the reverse flow of the power. That is,
the configuration required to prohibit or limit the reverse
flow of the power is the reverse flow power detection
circuit 150, the controller 151, the battery converter 157
and the battery 154.
In this case, when the reverse flow power is detected
by the reverse flow power detection circuit 150, i.e.,
during a period from when the amount of the power Wh reaches
the threshold value Whl until the battery 154 starts
charging, the power flows in a reverse direction, but it is
negligible in terms of time. Thus, the amount of the power
Wh being a function of time also is negligibly small.
Further, in order to suppress the reverse flow power due to
this time difference, the threshold value Whl may be set to
be smaller than the allowable amount of reverse flow power.
The controller 151 constantly monitors the voltage V
of the DC power line 14 through the AC/DC converter 158.
Specifically, as shown in FIG. 11A, the controller 151
compares the voltage V with first and second threshold
values VI and V2 and first and second command values Al and
A2 which are stored in its own memory 151a.
For example, if the generated power is greater than
the demanded power, the voltage V of the DC power line 14
becomes higher. On the other hand, if the generated power
is smaller than the demanded power, the voltage V of the DC
power line 14 becomes lower. Based on such characteristics,
a balance between supply and demand of the power can be
recognized by observing the voltage V of the DC power line
14. When the voltage V of the DC power line 14 is equal to
the first command value Al (reference value), the power
supply and demand are in balance. Here, the supplied power
is a value obtained by adding/subtracting the power
transferred between the AC and DC power systems to/from the
power generation.
If the voltage V exceeds the first command value Al,
the controller 151 determines that the power supply is
greater than the power demand. If the voltage V is less
than the first command value Al, the controller 151
determines that the power supply is smaller than the power
demand. Further, as shown in FIG. 11B, in a period during
which the voltage V exceeds the first command value Al, the
controller 151 increases the output current iout through the
DC/AC converter 159, or decreases the output current lout
through the AC/DC converter 158.
Specifically, as shown in FIG. 11B, in a period Tl
during which the voltage V exceeds the first command value
Al, the output current lout is reduced through the AC/DC
converter 158. In this case, since the output current lout
does not reach zero, the DC/AC converter 159 does not output
the output current iout. Further, in a period T2 during
which the voltage V exceeds the first command value Al, the
output current lout outputted from the AC/DC converter 158
is reduced, and the output current lout reaches zero.
In this case, if the voltage V still exceeds the first
command value Al, the output current iout starts to be
outputted from the DC/AC converter 159, and the output
current iout increases until the voltage V becomes equal to
the first command value Al. When the voltage V is equal to
the first command value Al, the output current iout becomes
constant. By this control, the voltage V is maintained at
the first command value Al.
In a period during which the voltage V is less than
the first command value Al, the output current lout from the
AC/DC converter 158 increases, or the output current iout
from the DC/AC converter 159 decreases. Specifically, in a
period T3 during which the voltage V is less than the first
command value Al, the output current iout outputted from the
DC/AC converter 159 is reduced.
Accordingly, when the output current iout reaches zero,
the output current lout starts to be outputted from the
AC/DC converter 158. The output current lout from the AC/DC
converter 158 increases until the voltage V becomes equal to
the first command value Al. When the voltage V is equal to
the first command value Al, the output current lout becomes
constant. Through such control, the voltage V is maintained
at the first command value Al.
Thus, the solar cell 3 and the fuel cell 4 may
generate power appropriately according to their
circumstances regardless of the demanded power.
Specifically, the solar cell 3 and the fuel cell 4 can
always generate power in accordance with the power
generation rules. For example, the power generation rules
of the solar cell 3 may be the MPPT control. Further, the
The first threshold value VI (upper limit) is set to a value
greater than the first command value Al. The first
threshold value VI is set based on the maximum voltage [ [V] ]
allowable by the DC power line 14. In a case where the
power generation is greater than the power demand, when the
surplus power cannot be sufficiently supplied to the AC
power line 12a, the voltage V reaches the first
thresholdpower line 12a, the voltage V reaches the first
threshold value VI. As a case where the power cannot be
sufficiently supplied to the AC power line 12a, there may be
a case where the power to be transmitted through the AC
power line 12a exceeds the maximum output power of the DC/AC
converter 159, or a case where the reverse flow of the power
is limited. In this case, the voltage V of the DC power
line 14 increases.
As shown in FIG. 11A, when the voltage V of the DC
power line 14 increases and reaches the first threshold
value VI (time tl), the controller 151 suppresses the output
power Pout in the order of the second converter 156 and the
first converter 155. Accordingly, the voltage V of the DC
power line 14 becomes less than the first threshold value VI,
and an excessive rise of the voltage V is suppressed.
Further, by firstly suppressing the output power of the
second converter 156, it is possible to maintain the power
generation efficiency of the solar cell 3 while reducing the
fuel consumption of the fuel cell 4.
The second command value A2 (lower limit) is set to be
smaller than the first command value Al. Further, the
second threshold value V2 is set to a value between the
first command value Al and the second command value A2. The
second command value A2 is set based on the voltage V of the
DC power line 14 when the power supply does not fulfill the
power demand of the DC devices 5. For example, there may be
a case where an AC power cannot be supplied to the DC power
line 14 from the AC power source 2 through the AC/DC
converter 158 due to a power failure or the like. In this
case, the voltage V of the DC power line 14 is less than the
second command value A2. Further, when the power demand of
the DC devices 5 increases rapidly, and it is impossible to
immediately respond to this increase due to limitation on
the maximum output power of the AC/DC converter 158, the
voltage V is less than the second command value A2.
In a state where the voltage V is less than the second
command value A2, the power is not sufficiently supplied to
the DC devices 5, and the DC devices 5 might not operate
normally. The controller 151 controls such that the voltage
V becomes equal to the first command value Al. Specifically,
the controller 151 controls such that the power is
discharged from the battery 154 to the DC power line 14
through the battery converter 157 when the voltage V of the
DC power line 14 is reduced and reaches the second command
value A2 (time t3 in FIG. 11A) . In this case, the battery
converter 157 is stopped until the voltage V reaches the
second threshold value V2 greater than the second command
value A2.
Further, the controller 151 starts the battery
converter 157 when the voltage V is reduced and reaches the.
second threshold value V2. In this case, the battery
converter 157 is stopped until the voltage V reaches the
second threshold value V2 except a case where the power is
charged in the battery 154 in order to prohibit the reverse
flow of the power. Further, the battery converter 157
requires a predetermined period of time from initiation of
the start-up to completion of the start-up which allows
actual supply of the power. The second threshold value V2
is set taking this into account.
That is, the second threshold value V2 is set such
that even if the voltage V drops rapidly, the start-up of
the battery converter 157 is completed when the voltage V
reaches the second command value A2. Accordingly, by
starting the battery converter 157 when the voltage V
reaches the second threshold value V2, the controller 151
can supply the power to the DC power line 14 through the
battery converter 157 when the voltage V reaches the second
command value A2 {time t3 of FIG. 11A) . Thus, it is
possible to more quickly compensate for the insufficient
power. Further, since the battery converter 157 is stopped
until the voltage V reaches the second threshold value V2,
it is possible to eliminate standby power consumption of the
battery converter 157 until then.
Moreover, in the case where the voltage V of the DC
power line 14 is less than the second command value A2, the
power of the battery 154 is supplied to the DC power line 14
to supplement the power supply from the AC power line 12a to
the DC power line 14 through the AC/DC converter 158 .
Accordingly, it is controlled such that the voltage V of the
DC power line 14 becomes equal to the second command value
A2 . Thus, without affecting the power generation of the
solar cell 3 and the fuel cell 4 according to the power
generation rules, it is possible to compensate for the
insufficient power.
Further, the battery converter 157 which has been
started when the voltage V reaches the second threshold
value V2 is stopped again when the voltage V becomes equal
to or greater than the first command value Al. Furthermore,
the battery converter 157 may be stopped again when the
voltage V becomes equal to or greater than the second
threshold value V2.
Further, as shown in FIG. 9, the DC distribution board
8 includes, e.g., a DC breaker 70 and a pair of DC/DC
converters 71. The DC breaker 70 is provided on the DC
power line 14, and cuts off an abnormal current when the
abnormal current flows in the DC power line 14. Accordingly,
the abnormal current is prevented from flowing into the DC
devices 5. The DC/DC converters 71 step down the voltage of
the DC power line 14 to proper voltages to be supplied to
the DC devices 5. In this case, the DC breaker 70 can
supply a high-voltage power to the DC devices 5 because it
does not step down the voltage of the DC power line 14. In
this way, by supplying the high-voltage power, it is
possible to suppress power loss in transmission.
Next, a power-feeding control processing procedure
performed by the controller 151 will be described with
reference to a flowchart shown in FIG. 12A. This procedure
is performed in accordance with a power-feeding program
stored in the memory 151a. Further, the power-feeding
program is prepared to maintain a balance between power
supply and demand.
Control is executed such that the voltage V is
maintained at the first command value Al (step S101) . This
control is carried out, as described above, through the
control of the bi-directional converter 160. Then, it is
determined whether the voltage V is equal to or greater than
the first threshold value VI (step S102) . If it is
determined that the voltage V is less than the first
threshold value VI (NO in step S102), the power generation
is carried out in accordance with the power generation rules
of the solar cell 3 and the fuel cell 4 through both the
converters 155 and 156 {step S103).
In this case, the power generation rules of the solar
cell 3 are executed through the MPPT control and the process
proceeds to step S105. On the other hand, if it is
determined that the voltage V is equal to or greater than
the first threshold value VI (YES in step S102), the output
power Pout form the converters 155 and' 156 is suppressed
(step S104) . Then, the process proceeds to step S105.
Then, it is determined whether or not the voltage V is
equal to or less than the second threshold value V2 (step
5105) . If it is determined that the voltage V is equal to
or less than the second threshold value V2 (YES in step
S105} and the voltage V is less than the second threshold
value V2, the voltage V is controlled to become the second
command value A2 through the battery converter 157 (step
5106) . Then, the power-feeding program is ended. On the
other hand, if it is determined that the voltage V exceeds
the second threshold value V2 (NO in step S105), the process
of the power-feeding program is terminated while the battery-
converter 157 maintains a stopped state.
Further, in this flowchart, step S101 is performed
through the control of the bi-directional converter 160,
steps S103 and S104 are performed through the control of the
first and second converters 155 and 156, and steps S106 and
S107 are performed through the control of the battery
converter 157.
Next, a reverse-flowing power regulation processing
procedure performed by the controller 151 will be described
with reference to a flowchart shown in FIG. 12B. This
procedure is performed in accordance with a reverse-flowing
power regulation program stored in the memory 151a. This
program is executed separately from the power-feeding
program.
First, an amount of a reverse-flowing power Wh is
calculated based on the reverse-flowing power detected by
the reverse flow power detection circuit 150 (step S151) .
Then, it is determined whether the calculated amount of the
power Wh is equal to or greater than the threshold value Whl
(step S152) .
If the amount of the power Wh is less than the
threshold value Whl (NO in step S152), the reverse-flowing
power regulation program is terminated. It is monitored
whether the amount of the power Wh reaches the threshold
value Whl by repeating the program every predetermined
control period.
If the amount of the power Wh is equal to or greater
than the threshold value Whl (YES in step S152), i.e., if it
reaches the maximum allowable amount of the reverse-flowing
power, a power is charged to the battery 154 from the DC
power line 14 through the battery converter 157 (step S153) .
At this time, the power equivalent to the reverse-flowing
power detected by the reverse flow power detection circuit
150 is charged in the battery 154 from the DC power line 14
through the battery converter 157. Accordingly, it is
possible to prevent the reverse power flow after it reaches
the maximum allowable amount of the reverse flow power.
In addition, if the reverse power flow is prohibited,
it can be assumed that the threshold value Whl is set to
zero, which leads to YES in step S152, and step S153 is
performed.
According to the third embodiment described above, the
following effects can be achieved.
(1) The power reversely flowing to the AC power source
2 is adjusted by charging and discharging of the battery 154.
Accordingly, the reverse flow power can be adjusted without
adjusting the power generated by the solar cell 3 and the
fuel cell 4. Thus, the solar cell 3 and the fuel cell 4 can
properly generate power regardless of the reverse power flow.
(2) Only the power equivalent to the power reversely
flowing to the AC power source 2 is charged to the battery
154 from the DC power line 14 through the battery converter
157. Accordingly, it is possible to prohibit the reverse
power flow without adjusting the power generated by the
solar cell 3 and the fuel cell 4.
(3) By controlling the bi-directional converter 160
such that the voltage V of the DC power line 14 is equal to
the first command value Al, it is possible to make the power
supply and demand in balance. In other words, when the
voltage V of the DC power line 14 is equal to the first
command value Al, the power supply and demand are in balance.
Specifically, if the voltage V of the DC power line 14
exceeds the first command value Al,- the output current iout
from the DC/AC converter 159 is increased or the output
current lout from the AC/DC converter 158 is decreased.
Further, if the voltage V of the DC power line 14 is less
than the first command value Al, the output current iout
from the DC/AC converter 159 is decreased or the output
current lout from the AC/DC converter 158 is increased.
Therefore, even if there is an imbalance between power
generation and power demand, there is no need to adjust the
power generated by the solar cell 3 and the fuel cell 4.
Thus, regardless of the power demand of the DC devices 5,
the solar cell 3 and the fuel cell 4 can properly generate
power.
(4) When the voltage V of the DC power line 14 becomes
equal to or greater than the first threshold value VI, it is
controlled such that the voltage V is less than the first
threshold value VI. That is, the power generated by the
solar cell 3 and the fuel cell 4 is suppressed through both
the converters 155 and 156 by the controller 151, and an
increase in the voltage V of the DC power line 14 is
suppressed. Accordingly, overpower is prevented from
occurring in the power distribution system 1, thereby
enhancing the safety of the system 1.
(5) When the voltage V of the DC power line 14 becomes
equal to or less than the second command value A2, the power
is discharged to the DC power line 14 from the battery 154.
Here, the second command value A2 is set based on the
voltage V of the DC power line 14 when the power supply does
not fulfill the power demand. As a case where the voltage V
of the DC power line 14 is equal to or less than the second
command value A2, for example, there may be a case where the
power cannot be supplied from the AC power line 12a to the
DC power line 14 through the AC/DC converter 158 due to a
power failure or the like. Even in this case, the power is
discharged to the DC power line 14 from the battery 154
through the battery converter 157. Thus, while maintaining
the power generation of the solar cell 3 and the fuel cell 4
in accordance with the power generation rules, the power can
be more stably supplied to the DC devices 5.
(6) When the voltage V of the DC power line 14 becomes
less than the second threshold value V2, the battery
converter 157 is started. In this way, since the battery
converter 157 can be stopped until the voltage V of the DC
power line 14 becomes less than the second threshold value
V2, it is possible to reduce the operating power of the
battery converter 157. Further, by starting the battery
converter 157 before the voltage V becomes equal to or less
than the second command value A2, the battery converter 157
can immediately discharge the power of the battery 154 to
the DC power line 14 when the voltage V becomes equal to or
less than the second command value A2. Thus, it is possible
to more quickly compensate for the lack of power supply.
(7) It is possible to determine whether the power
supply and demand are in balance based on the voltage V of
the DC power line 14 detected through the-AC/DC converter 58.
Further, the charging and discharging of the battery 154 are
controlled such that the voltage V of the DC power line 14
is equal to the first command value Al, thereby making the
power supply and demand in balance. In this way, the
controller 151 can easily make the power supply and demand
in balance by controlling the charging and discharging of
the battery 154.
Here,' for example, a configuration in which the
controller respectively receives the power to be consumed in
the load devices and the power generated by the power
generation device, and controls charging and discharging of
the battery based on the received power according to a
predetermined algorithm stored therein may be considered.
However, compared to this configuration, in the present
embodiment, it is not necessary to communicate with the load
devices or the power generation device. Also, since only
feedback control is performed by observing the voltage V of
the DC power line 14, it is possible to omit complicated
control associated with the communications. Thus, for
example, it is possible to instantaneously respond to power
imbalance due to steep variation in solar radiation of the
solar cell 3, or sudden change in load caused by turning
ON/OFF of the DC devices 5.
Hereinafter, a fourth embodiment of the present
invention will be described with reference to FIG. 13. A
power distribution system of the present embodiment is
different from the system of the third embodiment in that
the controller 151 is omitted and the functions of the
controller 151 are distributed to the converters 155 to 159
controller 151 are distributed to the converters 155 to 159
(accurately, the CPUs 165 thereof) . A description will be
given below focusing on the differences between the third
and fourth embodiments.
Each of the converters 155 to 158 recognizes the
voltage V of the DC power line 14 through its own output
voltage detection circuit 162 (see FIG. 10) . Further, the
DC/AC converter 159 recognizes the voltage V of the DC power
line 14 through the input voltage detection circuit 161.
Further, each of the first converter 155 and the second
converter 156 stores the first threshold value VI in its own
memory 165a. Then, both the converters 155 and 156 suppress
the output thereof when the voltage V reaches the first
threshold value VI.
Further, each of the AC/DC converter 158 and the DC/AC
converter 159 constituting the bi-directional converter 160
stores the first command value Al in its own memory 165a.
Further, the AC/DC converter 158 decreases the output
current iout through the DC/AC converter 159, or increases
the output current lout through the AC/DC converter 158 when
the voltage V is less than the first -command value Al.
Further, the DC/AC converter 159 increases the output
current iout through the DC/AC converter 159, or decreases
the output current lout through the AC/DC converter 158 when
the voltage V exceeds the first command value Al. Thus, it
is controlled such that the voltage V is equal to the first
command value Al as in the above-described embodiment.
In addition, the battery converter 157 stores the
second threshold value V2 and the second command value A2 in
its own memory 165a. The battery converter 157 is started
when the voltage V reaches the second threshold value V2,
and performs control such that a power is discharged to the
DC power line 14 from the battery 154 and the voltage V
becomes equal to the second command value A2 when the
voltage V is less than the second command value A2.
Further, the battery converter 157 recognizes the
threshold value Whl included in the information about the
reverse-flowing power which is obtained through the signal
line 17. Further, the battery converter 157 calculates the
amount of the reverse-flowing power Wh based on the reverse-
flowing power outputted from the reverse flow power
detection circuit 150. Further, as in the first embodiment,
when the amount of the power Wh reaches the threshold value
Whl, the battery converter 157 charges the battery 154 by
only the power equivalent to the reverse-flowing power,
thereby prohibiting the reverse flow of the power.
According to the embodiment as described above, in
addition to the effects (1) to (7) of the third embodiment,
the following effects can be achieved.
(8) The controller 151 of the first third embodiment
can be omitted. Accordingly, it is possible to achieve a
simpler configuration of the control unit 7, and also
suppress the costs associated with the controller 151.
Further, the costs associated with the controller 151.
Further, the converters 155 to 158 can perform power
generation based on the threshold and command values in
accordance with their own power generation rules without
communicating with each other, and, as in the first
embodiment, a balance between the power supply and demand
can be achieved. Further, since the communications between
the converters 155 to 158 is unnecessary, communications-
related processing is unnecessary. Consequently, it is
possible to more quickly achieve equilibrium of power supply
and demand. Further, since each of the converters 155 to
158 is configured independently, it is possible to easily
update and expand the system. Specifically, if needed, for
example, the system can be updated by exchanging each of the
converters 155 to 158.
Further, the battery converter 157 may prohibit the
reverse power flow, or limit the amount of a reversely-
flowing power Wh as in the third embodiment.
Further, the above-described embodiment may be
modified appropriately as follows.
* In the third embodiment, the controller 151 performs
the control of the voltage V through each of the converters
155 to 159 by executing the power feeding program in
accordance with the flowchart shown in FIG. 12A. However,
the controller 151 may execute different programs through
the converters 155 to 159. In this case, in the flowchart
of FIG. 12A, step S101, steps S102 to S104, and steps S105
to S107 are performed in accordance with processing
procedures of programs independently of each other.
Specifically, the controller 151 constantly performs
the processing of step S101 through the bi-directional
converter 160. At the same time, every predetermined period,
the controller 151 performs the processing of steps S102 to
S104 through both the converters 155 and 156, and also
performs the processing of steps S105 to S107 through the
battery converter 157. In the fourth embodiment, the bi-
directional converter 160, the converters 155 and 156, and
the battery converter 157 execute different programs as
described above.
• In the third and fourth embodiments, in case of
prohibiting the reverse flow of the power, the power
equivalent to the reverse-flowing power detected by the
reverse flow power detection circuit 150 is charged in the
battery 154 from the DC power line 14 through the battery
converter 157. However, part of the reverse-flowing power
detected by the reverse power detection circuit 150 may be
charged in the battery 154. In this case, the reverse flow
power can be adjusted arbitrarily.
• In the third embodiment, the controller 151
calculates the amount of the reverse-flowing power Wh based
power Wh. In this case, the reverse flow power detection
circuit 150 directly calculates the amount of reverse flow
power based on the detected power. Also in the fourth
embodiment, similarly, the reverse flow power detection
circuit 150 may calculate the amount of the reverse flow
power Wh. Also in the second embodiment, similarly, the
reverse flow power detection circuit 150 may calculate the
amount of the reverse flow power Wh.
• In the third and fourth embodiments, the reverse
power flow is allowed in a predetermined period of time.
However, the power distribution system 1 may be configured
such that the reverse power flow is not allowed at all. In
this case, the controller 151 or the battery converter 157
always prohibits the reverse power flow.
• In the third embodiment, the controller 151
recognizes the voltage V through the AC/DC converter 158.
However, the controller 151 may recognize the voltage V
through any other converter, e.g., the battery converter 157.
Further, a voltage detection circuit may be provided
separately from the converter.
• In the third and fourth embodiments, the fuel cell 4
and the solar cell 3 are provided as a DC power generation
device, but another DC power generation device is provided
as long as they can generate DC power. For example, the DC
power generation device may be a storage battery, wind power
generation device and the like. The storage battery and the
wind power generation device also have power generation
rules appropriate for themselves in terms of power
generation efficiency or life. In addition, the DC power
generation device may be configured using only the solar
cell 3 or only the fuel cell 4.
• In the third and fourth embodiments, the first and
second threshold values VI and V2 and the first and second
command values Al and A2 are set, but these may be omitted.
Even in this case, the reverse flow of the power can be
regulated while maintaining power generation in accordance
with the power generation rules of the fuel cell 4 and the
solar cell 3 by the battery 154, the battery converter 157
and the reverse power detection circuit 150.
While the invention has been shown and described with
respect to the embodiments, it will be understood by those
skilled in the art that various changes and modification may
be made without departing from the scope of the invention as
defined in the following claims.
We claim:
1. A power distribution system comprising:
a DC power system in which a DC power generated by a
DC power generation device is supplied to a DC load via a DC
supply line;
an AC power system which is linked to the DC power
system, for supplying an AC power from an AC power source
via an AC supply line;
a battery which is connected to the DC supply line;
and
a control unit which adjusts reverse power flowing to
the AC power source by charging/discharging the battery.
2. The power distribution system of claim 1, further
comprising:
a bi-directional converter which converts the AC power
from the AC supply line into a DC power, and converts the DC
power from the DC supply line into an AC power;
a DC/DC converter connected to the DC supply line,
which converts the DC power inputted from the DC power
generation device into a desired DC power in accordance with
predetermined control rules stored in the DC/DC converter,
and supplies the converted DC power to the DC load;
a charging/discharging circuit provided between the DC
supply line and the battery, which charges the battery with
a power from the DC supply line and discharges the power
from the battery to the DC supply line; and
a reverse flowing power detection circuit which is
connected to the AC supply line and detects the power
reversely flowing to the AC power source,
wherein the control unit adjusts the reverse flowing
power by controlling the charging/discharging circuit to
charge/discharge the battery based on detection results of
the reverse flowing power detection circuit.
3. The power distribution system of claim 2, wherein the
control unit prevents a reverse flow of the power by
charging the battery with a power from the DC supply line by
the charging/discharging circuit, the power being equivalent
to the reverse flowing power detected by the reverse flowing
power detection circuit.
4. The power distribution system of claim 2 or 3, further
comprising a voltage detection unit for detecting a voltage
of the DC supply line, wherein the control unit controls the
bi-directional converter such that the voltage of the DC
supply line maintains a reference value.
5. The power distribution system of claim 4, wherein,
when the voltage of the DC supply line detected by the
voltage detection unit becomes an upper limit or more, the
upper limit being greater than the reference value, the
control unit controls the DC/DC converter to suppress the
power generated by the DC power generation device such that
the voltage of the DC supply line becomes less than the
upper limit.
6. The power distribution system of claim 4 or 5, wherein
when the voltage of the DC supply line detected by the
voltage detection unit becomes equal to or less than a lower
limit, the lower limit being smaller than the reference
value, the control unit discharges the power from the
battery to the DC supply line by the charging/discharging
circuit.
7. The power distribution system of claim 6, wherein,
when the voltage of the DC supply line detected by the
voltage detection unit is equal to or less than a threshold
value between the reference value and the lower limit, the
control unit starts the charging/discharging circuit.
8. A power distribution system comprising:
a DC power system in which a DC power generated by a
DC power generation device is supplied to a DC load via a DC
supply line;
an AC power system which is linked to the DC power
system and in which an AC power from an AC power source is
supplied via an AC supply line;
a bi-directional converter which converts an AC power
from the AC supply line into a DC power, and converts a DC
power from the DC supply line into an AC power;
a DC/DC converter which is connected to the DC supply
line, converts the DC power inputted from the DC power
generation device into a desired DC power according to
predetermined control rules stored in the DC/DC converter,
and supplies the converted DC power to the DC load;
a battery which is connected to the DC supply line;
and
a charging/discharging circuit which is provided
between the DC supply line and the battery, for charging the
battery with a power from the DC supply line and discharging
a power from the battery to the DC supply line,
wherein the bi-directional converter stores a
reference value, and, when a voltage of the DC supply line
deviates from the reference value, controls a power
outputted to the DC supply line and the AC supply line such
that the voltage of the DC supply line is equal to the
reference value,
wherein the DC/DC converter stores an upper limit
greater than the reference value, and, when the voltage of
the DC supply line becomes equal to or greater than the
upper limit, controls a power outputted to the DC supply
line such that the voltage of the DC supply line becomes
less than the upper limit, and
wherein the charging/discharging circuit stores a
lower limit smaller than the reference value, and, when the
voltage of the DC supply line becomes less than the lower
limit, controls charging and discharging of the battery such
that the voltage of the DC supply line is equal to the lower
limit.
9. A power distribution system comprising: a plurality of
power distribution apparatuses, each having a distributed
power source provided in a power line connected to a
commercial power source; and a storage device connected to
the power line for storing a power flowing to the commercial
power source from the distributed power source.
10. The power distribution system of claim 9, wherein each
of the power distribution apparatuses includes at least one
load device to which the power is supplied, and a power can
be supplied to the load devices of the remaining power
distribution apparatuses from the distributed power source
of at least one of the power distribution apparatuses.
11. The power distribution system of claim 10, further
comprising: a sensor connected to the power line between the
commercial power source and the power distribution
apparatuses, for detecting a current flowing in the power
line, wherein the storage device is controlled based on
detection results of the sensor.
12. The power distribution system of claim 10 or 11,
wherein the storage device is controlled based on a command
signal outputted from power management facilities for
managing power of the commercial power source.
13. The power distribution system of any one of claims 10
to 12, wherein the storage device is discharged to supply a
power to the at least one load device.
14. The power distribution system of claim 13, wherein a
power supply to the load device of a specific power
distribution apparatus among the power distribution
apparatuses is limited based on the power discharged from
the storage device.
15. The power distribution system of claim 14, wherein a
power supply to the load device of a specific power
distribution apparatus among the plurality of power
distribution apparatuses is cut off based on the power being
discharged from the storage device.
16. The power distribution system of any one of claims 10
to 15, wherein power generation of the distributed power
source is limited based on a charging state of the storage
device.
17. The power distribution system of claim 16, wherein
power generations of a plurality of the distributed power
sources are limited sequentially based on priorities that
are set in advance.
18. The power distribution system of any one of claims 10
to 17, wherein each of the power distribution apparatuses is
provided in each dwelling unit of a multiple dwelling house.
19. The power distribution system of any one of claims 10
to 18, further comprising a power measuring sensor for
measuring an amount of a power being supplied to each of the
power distribution apparatuses from the power line, wherein
transfer of the power between the power distribution
apparatuses is controlled based on measurement results of
the power measuring sensor.
20. The power distribution system of claim 19, wherein the
transfer of the power between the power distribution
apparatuses is controlled based on information relating to a
power consumed in the load device and a power supplied from
the distributed power source of each of the power
distribution apparatuses.
21. The power distribution system of claim 19 or 20,
wherein the power distribution apparatus further
includes a power supply control unit for controlling
transfer of a power through the power line,
further comprising a controller connected to
communicate with the power supply control units, for
controlling the power supply control units to manage the
transfer of the power between the power distribution
apparatuses based on the measurement results of the power
measuring sensor.
22. The power distribution system of any one of claims 19
to 21, wherein, when a power is supplied to the power
distribution apparatus, the power distribution apparatus is
billed based on an amount of the power supplied to the power
distribution system, and a difference is set between billing
for an amount of a power supplied to the power distribution
apparatus from the commercial power source and billing for
the amount of the power supplied to the power distribution
apparatus from the distributed power source.
23. The power distribution system of claim 22, further
comprising a display device for displaying billing-related
information.
24. The power distribution system of any one of claims 19
to 24,
wherein the distributed power source includes multiple
types of power sources, and
wherein the power distribution apparatus having the
distributed power source which has supplied a power outputs
information for distinguishing the type of the power source
which has supplied the power as data.
25. The power distribution system of claim 24, wherein,
when the power distribution apparatus to which the power has
been supplied is billed based on the power supplied to the
power distribution apparatus from the distributed power
source, the amount of the power supplied to the power
distribution apparatus from the distributed power source is
billed differently according to the type of the power source
used to supply the power to the power distribution apparatus.

ABSTRACT

Disclosed is a power distribution system equipped with: a DC electric power system for supplying a DC electric power to a DC load via a DC supply line; an AC power system for supplying an AC electric power from an AC power supply; and a battery which is connected to the DC supply line. The power distribution system is further equipped with: a charging/discharging circuit which charges the battery with
electric power from the DC supply line and discharges the electric power from the battery to the DC supply line; a reverse power flow electric power detection circuit which detects the electric power in the reverse power flow to the AC power supply; and a control unit which adjusts the electric power in the reverse power flow to the AC power supply by charging/discharging the battery on the basis of the detection results of the reverse power flow electric power detection circuit.