Field of the Invention
The present invention relates to an electric power
supply system which distributes a power to buildings in a
specific area.
Background of the Invention
Conventionally, there has been proposed a technology in
which houses are grouped and power supplied to the houses is
cooperatively adjusted therebetween within the group.
Patent Document 1 discloses a technology for distributing
power supplied from an electric company, wherein a power
supply control device is provided between the entire houses
included in a group and a power system through which the
electric company supplies power. Further, the power supply
control device monitors an amount of electric power demand
in the houses to adjust the power supply-demand balance.
In the technology disclosed in Patent Document 1, it
is assumed that a distributed power source such as a micro
gas turbine power generation device, a photovoltaic power
generation device, a wind power generation device and a fuel
cell is provided in at least some of the houses in the
group. Thus, the power supply control device has a function
of collectively selling surplus power generated by the
distributed power source to the electric company, and a
function of collectively purchasing insufficient power of
the houses from the electric company. Further, if the power
to be supplied to the entire houses of the group is
insufficient, the power supply control device collectively
receives power from the electric company and distributes the
power to each of the power demand houses.
That is, since the power supply control device has a
function of distributing the power of the distributed power
source provided in a group to the houses of the group, it is
possible to reduce the amount of power supplied from the
electric company.
On the other hand, in Patent Document 2, there has
been proposed a photovoltaic power generating and supplying
system for grid connection including a plurality of power
generation load units each having a solar cell, a DC to AC
conversion unit and an AC load, and a single control center
including a common storage cell and a storage control unit,
the power generation load units connecting the single
control center. Further, the control center is connected to
a power system provided by an electric company. The DC to
AC conversion unit has a function of converting a DC power
generated by the solar cell into an AC power and supplying
the AC power to the AC load and the storage control unit.
In the technology disclosed in Patent Document 2, the
control center monitors the excess or deficiency of power in
each of the power generation load units, stores power in the
common storage cell when there is surplus power, and feeds
power to the power generation load units from the common
storage cell when the power is insufficient. Further, the
control center detects the amount of the power stored in the
common storage cell, receives power from the power system
when the power stored is insufficient, and causes a reverse
power flow to the power system from the common storage cell
when there is a surplus in the power stored.
In the technology disclosed in Patent Document 2, the
solar cell corresponds to the distributed power source, and
the power generation load units can be regarded as the
houses on the power demand side. Further, the houses
connected to the control center can be regarded as a group.
In other words, in the configuration described in Patent
Document 2, the distributed power source is provided in the
group including the power demand houses, and the power
supply from the power system provided by the electric
company and the reverse power flow to the power system are
collectively controlled by the center device, in the same
way as the configuration described in Patent Document 1.
[Patent Document 1] Japanese Patent Application
Publication No. 2002-10499
[Patent Document 1] Japanese Patent Application
Publication No. 2002-233077
As mentioned above, by using the technologies
described in Patent Documents 1 and 2, the power generated
by the distributed power source can be used in the power
demand houses of the group, and there is a connection point
for grid connection of the power system provided by the
electric company and the power generated by the distributed
power source.
Further, in the configurations described in Patent
Documents 1 and 2, since the electric company cannot notice
the amount of the power generated by the distributed power
source or the amount of the power consumed in each house, it
cannot determine an electricity charge of each house. In
other words, the amount of the power supplied from the power
system and the amount of the power reversely flowing to the
power system are perceived only by the power supply control
device or the control center relaying between the power
system provided by the electric company and the power demand
houses.
In the technologies described in Patent Documents 1
and 2, however, it is possible to perceive the amount of the
power supplied to the power supply control device or the
control center and the amount of the power reversely flowing
from the power supply control device or the control center.
Accordingly, the electric company can collect electricity
charges based thereon without providing a power meter in
each house.
On the other hand, in the power demand houses, the
more the amount of the power used, the larger the amount of
the power accommodated by other house. Therefore, if each
house individually makes a contract with the electric
company, it is impossible to employ the technologies of
Patent Documents 1 and 2.
Summary of the Invention
In view of the above, the present invention provides
an electric power supply system capable of measuring an
amount of a power received by each house on the power demand
side from a commercial power source while reducing an amount
of a power received from the commercial power source.
In accordance with an aspect of the present invention,
there is provided an electric power supply system including:
a common power source which includes a storage cell, and
supplies a power to the storage cell from buildings and from
the storage cell to the buildings via a local power grid
installed in a specific area including the buildings; a
distributed power source which is provided in at least some
of the buildings in the area, for supplying a power to the
buildings and supplying a surplus power to the common power
source; a first power meter which is provided in each of the
buildings, for measuring an amount of a power supplied from
a commercial power source; a second power meter which is
provided in each of the buildings, for measuring amounts of
power supplied from and to the common power source via the
local power grid; and a distribution control device which
distributes a power from the common power source to the area
on the basis of the amounts of power measured by the first
power meter and the second power meter.
Herein, the local power grid serves as a grid
connection of a power system of the commercial power source
and the respective buildings; and the common power source
has a function of storing a power in the storage cell which
is received via the local power grid from the buildings and
supplying a power to the buildings from the storage cell via
the local power grid. Further, the distribution control
device performs a management so that the amount of the power
supplied to the common power source is coincide with the
amount of the power supplied from the common power source in
each of the buildings, the management including supplying a
power from the common power source when the amount of the
power measured in a unit period by the first power meter is
equal to or greater than a prescribed value and returning a
power to the common power source when the amount of the
power measured in a unit period by the first power meter is
less than a return value, in each of the buildings, the
return value being a value lower than the prescribed value.
With the above configuration, since the common power
source shared by the buildings in a specific area is
provided an a power is supplied from the common power source
to the building in which an amount of a power purchased from
the commercial power source has increased, it is possible to
suppress the amount of the power supplied from the
commercial power source. For example, if the contract power
is set in each of the buildings, by equalizing the power
demand by the common power source, it is possible to prevent
the power demand in each of the buildings from exceeding the
contract power.
In addition, since some of the buildings in the area
include the distributed power source, the power generated by
the distributed power source is used in the buildings and a
surplus power is stored in the storage cell provided in the
common power source. Accordingly, the power stored in the
common power source can be commonly used in the buildings in
the area. Moreover, an amount of power corresponding to the
amount of the power supplied from the common power source is
returned using the distributed power source or the
commercial power source, so that the amount of the power
supplied to the common power source becomes coincide with
the amount of the power received from the common power
source in each of the buildings. Therefore, the amount of
the power purchased from the commercial power source in each
of the buildings is approximately equal to that when the
common power source is not provided.
Further, a unit price of the power supplied from the
commercial power source may be set in multiple stages, and
the distribution control device may control charging and
discharging of the storage cell based on the unit price.
Brief Description of the Drawings
The objects and features of the present invention will
become apparent from the following description of
embodiments, given in conj unction with the accompanying
drawings, in which:
FIG. 1 is a block diagram showing an electric power
supply system in accordance with an embodiment of the
present invention; and
FIG. 2 is a block diagram illustrating a case where
the building is a multiple dwelling house in the embodiment
of the present invention.
Detailed Description of the Embodiments
Hereinafter, embodiments of the present invention will
be described in detail with reference to the accompanying
drawings which form a part hereof. Throughout the
specification and drawings, like reference numerals will be
given to like parts having substantially the same function
and configuration, and a redundant description thereof will
be omitted.
In the embodiment to be described below, it is assumed
that there are multiple buildings in an area such as a town.
Each building may be a detached house, multiple dwelling
house or the like. As shown in FIG. 1, at least some of
buildings Bl to B3 in the area (hereinafter also referred to
as buildings B if it is not necessary to individually
identify buildings Bl to B3) include a distributed power
source such as a photovoltaic power generation device PV.
In the illustrated example, although some of the buildings B
include the photovoltaic power generation device PV, the
photovoltaic power generation device PV may be provided in
each of the buildings B.
The building Bl including the photovoltaic power
generation device PV is provided with a power conditioner 11
which converts an output of the photovoltaic power
generation device PV into an AC power, and allows to make a
grid connection with a power system Pn of a commercial power
source. Each of the buildings Bl to B3 is provided with a
distribution board 12 to supply a power to each load, and
the grid connection of the power system Pn and the power
conditioner 11 is carried out in the distribution board 12.
In the present embodiment, the photovoltaic power
generation device PV has been mentioned as an example of the
distributed power source, but a power generation device
using natural energy such as wind power, a micro gas turbine
power generation device, a cogeneration device such as a
fuel cell to generate power and heat, as long as it can be
used as a power generation device, may be used as the
distributed power source in any form.
In a case where the building is a multiple dwelling
house, as shown in FIG. 2, it is preferable that a storage
cell SCI is provided in addition to the photovoltaic power
generation device PV serving as a distributed power source,
and the photovoltaic power generation device PV and the
storage cell SCI are shared by dwelling units H of a
building B4 that is a multiple dwelling house. The storage
cell SCI is provided to store a surplus power when a power
is supplied to the dwelling units H from the photovoltaic
power generation device PV. Further, the power stored in
the storage cell SCI may be supplied to the dwelling units
H. To that end, a charge/discharge circuit 13 is provided
to perform charging and discharging of the storage cell SCI.
In the building B4 of multiple dwelling house, the
photovoltaic power generation device PV is provided and,
accordingly, the power conditioner 11 is also provided. The
power conditioner 11 converts not only a DC power from the
photovoltaic power generation device PV but also a DC power
from the storage cell SCI. Further, there is provided a
distribution board 14 to distribute a power to the dwelling
units H in the building B4.
In the building B4 including multiple dwelling units,
the contract power for power demand may be set by a
collective agreement of the dwelling units of the building
B4. In this case, the power conditioner 11 feeds a power to
the dwelling units H from the photovoltaic power generation
device PV and the storage cell SCI such that the power
demand in the whole building B4 does not exceed the contract
power. In other words, while the photovoltaic power
generation device PV generates a power, the power
conditioner 11 supplies the power of the photovoltaic power
generation device PV to the dwelling units H, and stores a
power in the storage cell SCI if there is a surplus power.
Further, the power conditioner 11 monitors the power demand
in the whole building B4, and feeds the power of the storage
cell SCI to the dwelling units H when the power demand
reaches a prescribed value that is set on the basis of the
contract power.
Meanwhile, a common power source 2 that is commonly
used in the area is provided, e.g., in the building B3. The
common power source 2 includes a storage cell SC and a
charge/discharge circuit 21 to perform charging and
discharging of the storage cell SC. Receiving a power in
the common power source 2 and feeding a power from the
common power source 2 are performed by a distribution
control device 22. In the illustrated example, although the
common power source 2 is provided in the building B3 such as
a municipal hall or a meeting place of the area is assumed
as the building B3, the common power source 2 is not
installed necessarily in such building, and the common power
source 2 may be provided separately.
A local power grid Pd is connected to each of the
buildings Bl to B4 in the area, separately from the power
system Pn of the commercial power source. The local power
grid Pd is installed between the distribution control device
22 and the buildings Bl to B4. Accordingly, the
distribution control device 22 has a function of
individually performing the distribution of power between
the common power source 2 and each of the buildings Bl to
B4. Additionally, in the building B3, a power line
equivalent to the local power grid Pd is provided between
the distribution control device 22 and a power meter M2
within the building B3.
In each of the buildings Bl to B4, two types of power
meters Ml and M2 are provided. One power meter, i.e., the
power meter Ml, measures an amount of a power that has been
received from the power system Pn of the commercial power
source. The other power meter, i.e., the power meter M2,
measures an amount of a power that has been supplied from/to
the common power source 2 through the local power grid Pd.
In each of the buildings B1 to B4, the power meter M2 has a function of
measuring an amount of a power supplied to the common power source 2 as well
as an amount of a power received from the common power source 2. ? That is,
the power meter M2 of each of the buildings B1 to B4 has a function of
measuring a power in bi-directionally.
The amounts of the power measured by the power meters
Ml and M2 are forwarded to the distribution control device
22. That is, the distribution control device 22 obtains the
amounts of the power by communicating with the power meters
Ml and M2. As a communications channel, in addition to a
dedicated wired communications channel, the local power grid
Pd to which the power line carrier communication technology
can be employed may be used, and a wireless communications
channel may also be used.
In this embodiment, a reverse power flow to the power
system Pn of the commercial power source is not considered.
Further, when a power outage occurs in the commercial power
source, the power system Pn is removed and an autonomous
operation may be performed within the local power grid Pd.
With the above-described configuration, even when
there are multiple buildings Bl including the photovoltaic
power generation device PV, a storage cell need not to be
provided in each of the buildings Bl. That is, the storage
cell SC can be shared by the buildings Bl each including the
photovoltaic power generation device PV. Therefore, in a
system in which a power is stored when there is a surplus in
the power generated by the photovoltaic power generation
device PV and the stored power is fed when the amount of the
power generation is reduced, there is no need to provide the
storage cell in each of the buildings Bl, and it is possible
to reduce the locations where the storage cell is provided.
Further, by commonly using the storage cell, it is possible
to reduce the costs compared to a case where an individual
resident purchases a storage cell.
Herein, since the storage cell SC is commonly used in
the buildings Bl to B4, it is necessary to make the amount
of the power used in each of the buildings Bl to B4
equivalent to that when the storage cell SC is not commonly
used. Accordingly, the amount of the power stored to the
storage cell SC and the amount of the power used from the
storage cell SC are measured by the power meter M2, and the
measured amount of power is notified from the power meter M2
to the distribution control device 22.
The distribution control device 2 2 manages the use of
the storage cell SC by using the amount of the power
measured by the power meter M2 of each of the buildings Bl
to B4. Further, the distribution control device 22 is
provided with a local power meter M3 which measures an
amount of a power stored in the storage cell SC from each of
the buildings Bl to B4 using the common power source 2 and
an amount of a power supplied to each of the buildings Bl to
B4 from the storage cell SC. The amount of the power
measured by the local power meter M3 is used in order to
obtain an amount of a power that has been lost in the power
conversion and transmission.
In other words, ideally, the total amount of the power
measured by the power meters M2 of the buildings Bl to B4 is
equal to the amount of the power measured by the local power
meter M3, but actually, there occurs a difference
corresponding to a loss in the amount of the power. By
calculating the difference/ the power loss in the use of the
common power source 2 can be taken into consideration. This
makes it possible to equally distribute the power of the
common power source 2 to the buildings Bl to B4.
Generally, a unit price on electricity charges of the
commercial power source is determined based on the contract
power, which has been set on the basis of a maximum value of
the power demand in one month, the power demand being an
average value of the amount of power used every 30 minutes.
For that reason, in each of the buildings Bl to B4, it is
desirable to suppress the maximum value of the power demand
measured by the power meter Ml.
Then, the distribution control device 2 2 calculates
the power demand in each of the buildings Bl to B4 by
obtaining the amount of power consumed in each of the
buildings Bl to B4 being measured by the power meter Ml (the
amount of power used can be used as a value proportional to
the power demand in case of obtaining the amount of power
used every 30 minutes) . If the power demand in one of the
buildings Bl to B4 reaches a prescribed value (an
appropriate power value set to be lower than the contract
power), the distribution control device 22 supplies the
corresponding one of the buildings Bl to B4 with a power
from the common power source 2 to prevent the power demand
from exceeding the contract power.
The power from the common power source 2 can be also
supplied to the buildings B2 and B3 not including the
photovoltaic power generation device PV as well as the
buildings Bl and B4 including the photovoltaic power
generation device PV.
If the building Bl or B4 including the photovoltaic
power generation device PV has stored a power in the storage
cell SC and the stored power remains, it can be used freely.
Further, even if there is no amount of power remaining in
the storage cell, it is possible to receive a power from the
common power source 2 if there is a surplus power in the
storage cell SC. On the other hand, even in the buildings
B2 and B3 not including the photovoltaic power generation
device PV, it is possible to receive a power from the common
power source 2 if there is a surplus power in the storage
cell SC. Thus, in any one of the buildings Bl to B4, it is
possible to receive a power from the common power source 2
when the power demand reaches the prescribed value, thereby
preventing the power demand from exceeding the contract
power.
If a power is stored in the storage cell SC by the
buildings Bl and B4 including the photovoltaic power
generation device PV and the buildings Bl and B4 uses a
larger amount of the power than an amount of the stored
power, it is possible to perform charging of the storage
cell SC when there is a surplus in the power generated by
the photovoltaic power generation device PV provided in the
buildings Bl and B4. That is, the amount of the power
received from the common power source 2 can be returned to
the common power source 2 when there is a surplus power.
Herein, it is desirable to set a deadline such that
the amount of the received power and the amount of the
returned power are offset within an appropriate period. The
deadline can be set in units such as one day, one week, one
month and one year. If it is impossible to offset the
received power within the deadline, it is preferable that
the power purchased from the power system Pn is used for
charging of the storage cell SC to offset the received
power.
On the other hand, if the common power source 2 has
been used by the buildings B2 and B3 not including the
photovoltaic power generation device PV, charging of the
storage cell SC is performed by the power purchased from the
power system Pn when the power demand is lowered to a return
value set to be lower than the prescribed value. In other
words, in the buildings B2 and B3, it is possible to prevent
the power demand from exceeding the contract power by using
the common power source 2, and charging of the storage cell
SC is performed by the power purchased from the commercial
power source when the power demand is lowered. In this
case, the amount of power measured by the power meter Ml is
equal to that when the common power source 2 is not used.
Therefore, in the buildings B2 and B3, the increase in
electricity charges is suppressed by preventing the power
demand from exceeding the contract power, and the
electricity charges commensurate with the amount of power
used are paid to an electric company.
The unit price of electricity charges on the power
supplied from the commercial power source may be set in
multiple stages according to time zones of using the
electricity. In this case, when a power is used from the
common power source 2 and then returned thereto by using the
power purchased from the commercial power source, it is
possible to use the power purchased in the time zone when
the unit price of electricity charges is low. As a result,
it is possible to prevent an increase in electricity charges
in each of the buildings Bl to B4 by using the power
purchased in the time zone when the unit price of
electricity charges is low. Also, in general, the power
demand is low in the time zone when the unit price of
electricity charges is low, and it is possible to equalize
the power supply by increasing the amount of the power used
during this time zone.
As described above, according to the embodiment of the
present invention, since the common power source 2 is shared
by the multiple buildings Bl to B4 in the area, each of the
buildings Bl to B4 can use the power stored in the common
power source 2 if necessary. In particular, since the
buildings B2 and B3 not including the photovoltaic power
generation device PV can use the power stored in the storage
cell SC, it is possible to prevent the power demand from
exceeding the contract power. Accordingly, it is possible
to suppress the total electricity charges in the area using
the common power source 2.
Besides, since the amount of power stored to the
common power source 2 and the amount of power used from the
common power source 2 are measured by the power meter M2 in
each of the buildings Bl to B4, and collectively managed by
the distribution control device 22, the common power source
2 can be used as if the storage cell SC is installed in each
of the buildings Bl to B4.
Moreover, in the buildings B2 and B3 not including the
photovoltaic power generation device PV, the amount of the
power corresponding to the amount of the power supplied from
the common power source 2 is purchased from the commercial
power source and returned to the common power source 2.
Accordingly, the total amount of the power purchased from
the commercial power source and measured by the power meters
Ml is approximately equal to that when the common power
source 2 is not used.
While the invention has been shown and described with
respect to the embodiment, 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. An electric power supply system comprising:
a common power source which includes a storage cell,
and supplies a power to the storage cell from buildings and
from the storage cell to the buildings via a local power
grid installed in a specific area including the buildings;
a distributed power source which is provided in at
least some of the buildings in the area, for supplying a
power to the buildings and supplying a surplus power to the
common power source;
a first power meter which is provided in each of the
buildings, for measuring an amount of a power supplied from
a commercial power source;
a second power meter which is provided in each of the
buildings, for measuring amounts of power supplied from and
to the common power source via the local power grid; and
a distribution control device which distributes a
power from the common power source to the area on the basis
of the amounts of power measured by the first power meter
and the second power meter,
wherein the local power grid serves as a grid
connection of a power system of the commercial power source
and the respective buildings; and the common power source
has a function of storing a power in the storage cell which
is received via the local power grid from the buildings and
supplying a power to the buildings from the storage cell via
the local power grid, and
wherein the distribution control device performs a
management so that the amount of the power supplied to the
common power source is coincide with the amount of the power
supplied from the common power source in each of the
buildings, the management including supplying a power from
the common power source when the amount of the power
measured in a unit period by the first power meter is equal
to or greater than a prescribed value and returning a power
to the common power source when the amount of the power
measured in a unit period by the first power meter is less
than a return value, in each of the buildings, the return
value being a value lower than the prescribed value.
2. The electric power supply system of claim 1, wherein when
a unit price of the power supplied from the commercial power
source is set in multiple stages, the distribution control
device controls charging and discharging of the storage cell
based on the unit price.
3. The electric power supply system of claim 1, wherein the
distribution control device includes a local power meter to
measure amounts of a power supplied to the storage cell from
each of the buildings in the area and a power from the
storage cell to each of the buildings in the area, and
calculates a difference between the amount of the power
measured by the second power meter provided in each of the
buildings and the amount of the power measured by the
local power meter.

ABSTRACT

Disclosed is an electric power supply system which
has: a common power source which stores and supplies a power
via a local power grid; and a distributed power source which
supplies a power to buildings and a surplus to the common
power source. The electric power supply system further
includes a first power meter measuring the amount of power
supplied from a commercial power source, a second power
meter measuring the amount of power received from and
supplied to the common power source via the local power
grid, and a distribution control device which distributes a
power from the common power source to the area based on the
amounts of power as measured by the first power meter and
the second power meter.