Grid interconnection device, grid interconnection system, and power control system

A grid interconnection device 100 for interconnecting a power storage device to a power distribution system to which alternating current power is distributed, the grid interconnection device comprises a receiver 101 and a controller 104. The receiver 101 receives a second adjustment instruction transmitted before a first adjustment instruction. The controller 104 controls the power storage amount on the basis of the second adjustment instruction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2009-044447, filed on Feb. 26, 2009 and Japanese Patent Application No. 2010-013104, filed on Jan. 25, 2010; the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a grid interconnection device and a power control system configured to control a backward flow power toward a power distribution system.

2. Description of the Related Art

Nowadays, there have been increasing cases where a power supply device and a power storage device are provided in a customer (for example, a house and a factory) supplied with alternating current power from a substation. Specifically, plural power distribution systems are provided under the management of the substation, and the power supply device and the power storage device are connected to one of the power distribution systems through a grid interconnection device. Electric power supplied from the power supply device is not only supplied to power consumption devices such as a household electric appliance provided in its own customer, but also may be provided to the power distribution system as a backward flow through the grid interconnection device.

Here, if consumed power of the power consumption devices installed in each of customers reaches a peak as in the case of the afternoon in summer, for example, the consumed power in each customer may exceed the electric power supplied from the substation.

To address this problem, there has been proposed a technique for providing, within an acceptable range, the backward flow of the electric power supply from the power supply device in each customer in accordance with an instruction from the substation (see Japanese Patent Application Publication No. Hei 10-248180).

SUMMARY OF THE INVENTION

However, the technique disclosed in Japanese Patent Application Publication No. Hei 10-248180 does not consider the backward flow of the electric power stored in the power storage device. Thus, when the amount of backward flow needs to be increased, the amount of backward flow cannot be increased up to a desired amount if the power storage device has a small remaining volume of power.

In contrast, when the amount of backward flow needs to be reduced, the amount of backward flow cannot be reduced down to a desired amount if the power storage device has a large remaining volume of power.

The present invention has been made to solve the aforementioned problem, and an object of the present invention is to provide a grid interconnection device, a grid interconnection system, and a power control system capable of controlling the amount of backward flow from each customer.

A grid interconnection device according to the characteristic of the present invention is a grid interconnection device for interconnecting a power storage device to a power distribution system to which alternating current power is distributed. The grid interconnection device comprises: a controller configured to control input/output power indicating forward flow power that flows from the power distribution system to the power storage device and/or backward flow power that flows reversely from the power storage device to the power distribution system; and a receiver configured to receive a first adjustment instruction to adjust or set the input/output power, and a second adjustment instruction to adjust a power storage amount in the power storage device, the first adjustment instruction transmitted through a predetermined transmission path, the second adjustment instruction transmitted through the predetermined transmission path before the first adjustment instruction, wherein the controller controls the input/output power on the basis of the first adjustment instruction, and controls the power storage amount on the basis of the second adjustment instruction.

In the grid interconnection device according to the characteristic of the present invention, the second adjustment instruction may indicate an increase of the power storage amount, and the first adjustment instruction may indicate an increase of the backward flow power.

In the grid interconnection device according to the characteristic of the present invention, the second adjustment instruction may indicate a decrease of the power storage amount, and the first adjustment instruction may indicate a decrease of the backward flow power or an increase of the forward flow power.

A grid interconnection system according to the characteristic of the present invention comprises: a grid interconnection device for interconnecting a power storage device to a power distribution system to which alternating current power is distributed, wherein the grid interconnection device comprises: a controller configured to control input/output power indicating forward flow power that flows from the power distribution system to the power storage device and/or backward flow power that flows reversely from the power storage device to the power distribution system; and a receiver configured to receive a first adjustment instruction to adjust or set the input/output power, and a second adjustment instruction to adjust a power storage amount in the power storage device, the first adjustment instruction transmitted through a predetermined transmission path, the second adjustment instruction transmitted through the predetermined transmission path before the first adjustment instruction, wherein the controller controls the input/output power on the basis of the first adjustment instruction and controls the power storage amount on the basis of the second adjustment instruction.

A power control system according to the characteristic of the present invention comprises: a power distribution facility configured to distribute alternating current power to a power distribution system; and a plurality of customers each including a grid interconnection device configured to interconnect a power storage device to the power distribution system, wherein the plurality of customers are grouped into a plurality of groups, the grid interconnection device comprises: a controller configured to control input/output power indicating forward flow power that flows from the power distribution system to the power storage device and/or backward flow power that flows reversely from the power storage device to the power distribution system; a receiver configured to receive a first adjustment instruction to adjust or set the input/output power, and a second adjustment instruction to adjust a power storage amount in the power storage device, the first adjustment instruction transmitted through a predetermined transmission path, the second adjustment instruction transmitted through the predetermined transmission path before the first adjustment instruction; and a determination unit configured to determine whether or not an own group to which the grid interconnection device belongs to is an application group, on the basis of group information being included in each of the first adjustment instruction and the second adjustment instruction and indicating the application group to which each of the first adjustment instruction and the second adjustment instruction is applied among the plurality of groups, wherein the controller controls the input/output power on the basis of the first adjustment instruction and controls the power storage amount on the basis of the second adjustment instruction if the determination unit determines that the own group is the application group.

In the power control system according to the characteristic of the present invention, the power distribution facility may comprise: a calculator configured to calculate an adjustment amount or a set amount of the input/output power on the basis of a history of a voltage value of the power distribution system or a history of a power usage amount in the customer, and an instruction generator configured to generate the first adjustment instruction including information that indicates the adjustment amount or the set amount calculated by the calculator.

In the power control system according to the characteristic of the present invention, the power distribution facility may comprise: a calculator configured to calculate an adjustment amount or a set amount of the input/output power on the basis of a weather condition; and an instruction generator configured to generate the first adjustment instruction including information that indicates the adjustment amount or the set amount calculated by the calculator.

In the power control system according to the characteristic of the present invention, the power distribution facility may comprise: a calculator configured to calculate an adjustment amount or a set amount of the input/output power on the basis of information on an event that influences power consumption in a customer; and an instruction generator configured to generate the first adjustment instruction including information that indicates the adjustment amount or the set amount calculated by the calculator.

According to the present invention, a grid interconnection device, a grid interconnection system, and a power control system capable of controlling the amount of backward flow from each customer can be provided.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a power control system according to embodiments of the present invention will be described with reference to the drawings. Note that, in the descriptions of the drawings below, the same or similar portions are denoted by the same or similar reference numerals.

It should be noted, however, that the drawings are schematic, and that the dimensional proportions and the like are different from their actual values. Accordingly, specific dimensions and the like should be inferred based on the description given below. Moreover, obviously, dimensional relationships and proportions may differ from one drawing to another in some parts.

Generally, a flow of electric power from a power distribution system toward a customer is called a “forward flow,” and electric power that flows, namely, electric power inputted from a power distribution system to a customer is called “forward flow power.” In addition, a flow of electric power from a customer toward a power distribution system is called a “backward flow,” and electric power that reversely flows, namely, electric power outputted from a customer to a power distribution system is called “backward flow.” Note that the “forward flow power” and “backward flow power” are also referred to as “input/output power.”

Hereinafter, a first embodiment of the present invention will be described. In the first embodiment, descriptions will be given for the case where consumed power reaches a peak in the daytime as in the case of the day of an event in the neighborhood, or a summer day. For this reason, the first embodiment aims to resolve a shortage of power in the daytime by increasing backward flow power.

(Configuration of Power Control System)

Hereinafter, a configuration of the power control system according to the first embodiment will be described with reference toFIG. 1.FIG. 1is a schematic diagram showing a configuration of a power control system1according to the first embodiment.

As shown inFIG. 1, the power control system1includes a high-voltage power source10, a substation20, and plural customers30(customers30A to30I).

The high-voltage power source10transmits high-voltage power to the substation20through a high-voltage power line40. The high-voltage power source10is a power plant, for example.

The substation20distributes alternating current power generated by stepping down the high-voltage power, to the customers30through a power distribution system50. The power distribution system50is a unit in which the substation20manages the customers30. Note that the substation20may include plural power distribution systems50under its management, although not illustrated. A configuration of the substation20will be described later.

Each of the customers30is electrically connected to the substation20through the power distribution system50to which the alternating current power is distributed. The customer30receives and outputs electric power from and to the power distribution system50according to needs.

Here, the plural customers30are grouped into plural groups G (groups G1to G3). Specifically, the plural customers30are grouped so that the total amounts of backward flow power from the respective groups G to the power distribution system50can be almost equal to each other. Therefore, the maximum amount of backward flow power that a group of the customers30A to30C is allowed to provide is substantially equal to the maximum backward flow power that each group of the customers30D to30F and the customers30G to30I is allowed to provide.

Note that the maximum backward flow power from each of the customers30can be identified in advance on the basis of a contract capacity to be described later, rated output power of the power supply device32to be described later, and a power storage capacity of a power storage device33to be described later.

Hereinafter, a configuration of the substation according to the first embodiment will be described with reference toFIG. 2.FIG. 2is a block diagram showing a configuration of the substation20according to the first embodiment.

As shown inFIG. 2, the substation20includes a power distribution controller21, an instruction generator22, and a transmitter23.

The power distribution controller21includes a relay21A. The relay21A switches whether or not to distribute alternating current power, which a transformer (not shown) generates by stepping down the high-voltage power, to the power distribution system50.

The instruction generator22generates a first adjustment instruction that is an instruction to adjust the backward flow power from each customer30. Note that, in this embodiment, the “first adjustment instruction” is a collective term for “backward flow provide request” requesting the customer30to increase the backward flow power, “backward flow approval” allowing the customer30to increase and decrease the backward flow power at its own discretion, and “backward flow disapproval” instructing the customer30to stop the backward flow power. As described above, the first embodiment is intended to resolve a shortage of power by increasing the backward flow power on the basis of the backward flow provide request.

Moreover, the instruction generator22generates a second adjustment instruction that is an instruction to adjust a power storage amount in the power storage device33provided to each customer30, before the first adjustment instruction. Note that, in this embodiment, the “second adjustment instruction” includes a “charge request” for an increase of the power storage amount (charge) and a “discharge request” for a decrease of the power storage amount (discharge).

In addition, the instruction generator22incorporates group information into each of the first and second adjustment instructions, the group information indicating an application group Gp to which the first and second adjustment instructions are applied. This enables the first and second adjustment instructions to be applied only to the customers30included in the application group Gp. Therefore, in this embodiment, the instruction generator22can generate the first and second adjustment instructions having different contents for the groups G1to G3, respectively. A cycle of generating (transmitting) the first and second adjustment instructions for the groups G will be described later.

Moreover, the instruction generator22incorporates time information into each of the first and second adjustment instructions, the time information indicating a time period in which the adjustment instruction is applied. Instead of using the time information, the instruction generator22may generate new first and second adjustment instructions periodically (every hour, for example).

Further, the instruction generator22incorporates backward flow power information, which indicates the backward flow power and the power storage amount, into each of the first and second adjustment instructions. Accordingly, the shortage of power in the daytime can be efficiently resolved. Here, the backward flow power information can be determined on the basis of the following four methods.

(1) First Method

A first method is a method of calculating how much amount of backward flow power from each customer30should be obtained to resolve a shortage of power, on the basis of a voltage drop tendency (voltage drop range Δv/time duration Δt) in the power distribution system50as shown inFIG. 3, the contract capacity, the rated output power of the power supply device32, and the power storage capacity of the power storage device33.

When the customer30introduces a power consumption device31, the power supply device32, and the power storage device33(at the time of power-receiving contract), the contract capacity is determined and companies which provide and manage the power distribution system50such as a power company (an owner and operator of the power grid, and an operation manager of the power transmission and distribution system) are notified of the rated output power of the power supply device32, the power storage capacity of the power storage device33, and the like. Note that, therefore, the substation20can obtain the information presented to the power company. The voltage V may be measured at each grid interconnection point at which a grid interconnection device of a customer30is connected to the power distribution system50. In this case, an average value, a largest value, or a smallest value of measured voltage values at the grid interconnection point may be determined as the voltage V.

(2) Second Method

A second method is a method of calculating how much amount of backward flow power from the customer30should be obtained to resolve the shortage of power in consideration of weather conditions on the day (real-time data, forecast data, and the like), a season, time, calendar information, and the presence or absence of: an event such as a sportscast (an increase in power consumption by using power consumption devices such as an air conditioner and a television set in the customer30for watching of, a live broadcast of a soccer or basket ball game, a high school baseball game in midsummer and the like, an Olympic games broadcast, and the like); or an event in the power distribution system50(an increase in power consumption at a venue for a concert or the like and neighboring facilities).

(3) Third Method

A third method is a method of calculating how much amount of backward flow power from the customer30should be obtained to resolve the shortage of power, on the basis of the amount of forward flow/backward flow calculated from, for example, the type and the rated output power of the power supply device32provided to each customer30, in addition to the weather conditions on the day mentioned in the second method.

Here, the power supply device32is classified into several types. Examples of those types are: a type having rated output power with a certain value or higher, a public use type, an environment-friendly clean energy type such as a photovoltaic power generator and a wind turbine generator, and a reliable supply type such as a gas engine generator and a fuel cell power generator having no power output fluctuation caused by weather conditions and the like.

(4) Fourth Method

A fourth method is a method of calculating how much backward flow power from the customer30should be obtained to resolve the shortage of power, on the basis of prediction information derived from a history of past power consumption and the like and the amount of forward flow/backward flow calculated from the type and the rated output power of the power supply device32provided to the customer30, and the like.

The transmitter23transmits the first and second adjustment instructions generated by the instruction generator22to each customer30. Specifically, the transmitter23broadcasts the first and second adjustment instructions to all the customers30through the power distribution system50(a power line communication and the like).

Instead, the transmitter23transmits the first and second adjustment instructions to the customers30through a transmission path different from that of the power distribution system50. For example, the transmitter23transmits the first and second adjustment instructions to all the customers30by using a data distribution segment provided separately from a content distribution segment in the terrestrial digital broadcasting.

Hereinafter, a configuration of the customer according to the first embodiment will be described with reference toFIG. 4.FIG. 4is a block diagram showing a configuration of the customer30according to the first embodiment. Note that the arrows inFIG. 4indicate directions of inputs and outputs of electric power.

As shown inFIG. 4, the customer30includes plural power consumption devices31(power consumption devices31A to31C), the power supply device32, the power storage device33, and a grid interconnection device100. The power supply device32, the power storage device33, and the grid interconnection device100form a grid interconnection system.

The power consumption devices31operate by consuming forward flow power transmitted from the power distribution system50and output power outputted by the power supply device32. The power consumption devices31are household electric appliances, for example.

Examples of the power supply device32are a photovoltaic power generator, a wind turbine generator, a fuel cell power generator, and a gas engine generator. The power supply device32may be a secondary battery, an electric double-layer capacitor, or the like.

The power storage device33stores the output power outputted by the power supply device32and the forward flow power from the power distribution system50. The power storage device33may be a secondary battery such as a lithium ion battery and a nickel hydride battery, an electric double-layer capacitor, or the like.

The grid interconnection device100controls interconnections among the power distribution system50, the plural power consumption devices31, the power supply device32, and the power storage device33. For example, when the grid interconnection device100controls the interconnection between the power distribution system50and the power storage device33, the grid interconnection device100controls the backward flow power from the power storage device33to the power distribution system50. A configuration of the grid interconnection device100will be described below.

(Configuration of Grid Interconnection Device)

Hereinafter, a configuration of the grid interconnection device according to the first embodiment will be described with reference toFIG. 5.FIG. 5is a block diagram showing a configuration of the grid interconnection device100according to the first embodiment.

As shown inFIG. 5, the grid interconnection device100includes a receiver101, a storage102, a determination unit103, and a controller104. The receiver101receives the aforementioned first and second adjustment instructions through the power distribution system50(a power line communication and the like) or the terrestrial digital broadcasting.

The storage102stores own group information that specifies an own group to which its customer30belongs. In addition, the storage102stores the contract capacity, the rated output power and the type of the power supply device32, the power storage capacity of the power storage device33, and the like.

The determination unit103determines whether or not the own group is the application group Gp on the basis of the group information included in the first adjustment instruction received by the receiver101.

If the determination unit103determines that the own group is the application group Gp, the controller104controls the backward flow power and the power storage amount on the basis of the first and second adjustment instructions.

Now, a control of the controller104will be described by taking an example of the first and second adjustment instructions transmitted from the substation20to each group G. The table below shows an example of what are instructed by the first and second adjustment instructions. In the table below, the first adjustment instruction includes a backward flow provide request A, a backward flow approval B, and a backward flow disapproval C, and the second adjustment instruction includes a charge request P and a discharge request Q.

As shown in the table above, the backward flow provide request A is transmitted to the groups G1to G3in the daytime (from 12 to 15 o'clock) when the consumed power reaches a peak. In preparation for this, during the nighttime (0 to 7 o'clock), the charge request P is transmitted to the groups G1to G3. In the morning (8 to 12 o'clock), the backward flow approval B and the backward flow disapproval C are transmitted in combination with each other so that the groups G1to G3can provide the backward flow equally. From the early evening (16 to 24 o'clock), the discharge request Q is transmitted to the groups G1to G3in order to facilitate efficient charging during the nighttime (0 to 7 o'clock).

Upon receipt of the charge request P, the controller104stops the backward flow power, and causes the power storage device33to store the output power of the power supply device32. Upon receipt of the discharge request Q, the controller104uses the electric power stored in the power storage device33as power supplied to the power consumption devices31, or reversely provides the stored electric power as the backward flow power to the power distribution system50.

In addition, upon receipt of the backward flow provide request A, the controller104provide the backward flow of the output power of the power supply device32and the electric power stored in the power storage device33within the range of target power indicated by electric power information.

Moreover, upon receipt of the backward flow approval B, the controller104can provide the backward flow of the output power of the power supply device32if the output power is larger than the consumed power of the power consumption devices31. For example, when the controller104receives the backward flow approval B after receiving the backward flow provide request A, or when the price of power purchased from a customer is higher than the price of power sold to the customer, the output power of the power supply device32is preferably provided as the backward flow. Meanwhile, when the controller104receives the backward flow approval B before receiving the backward flow provide request A, the output power of the power supply device32is preferably stored in the power storage device33unless the power storage device33is fully charged.

In addition, upon receipt of the backward flow disapproval C, the controller104stores the output power of the power supply device32in the power storage device33even if the output power of the power supply device32is larger in amount than the consumed power of the power consumption devices31. In other words, in this case, the controller104stops the backward flow power. Note that, on the other hand, the controller104can supply the forward flow power without any inhibition to the power consumption device31and the power storage device33. Particularly, when the adjustment instruction includes the backward flow disapproval B and a forward flow receive request (not shown in Table 1) to increase the amount of forward flow, the controller104increases the forward flow power from the power distribution system50to the power consumption devices31and the power storage device33.

In addition, the controller104controls the output power of the power supply device32so that the output power can synchronize with the alternating current power of the power distribution system50. Specifically, when the power supply device32is a direct current power supply (a photovoltaic power generator, for example), the controller104steps up direct current power outputted by the power supply device32by using a boost circuit and then converts the resultant direct current power into predetermined alternating current power for the purpose of synchronization with the alternating current power of the power distribution system50. Here,FIGS. 6A to 6Dare diagrams for illustrating schemes for connecting the power storage device33to a photovoltaic module S and a power conditioner C that are already present in the customer30. Note that, inFIGS. 6A to 6D, the power storage devices33have input and output sources different from each other in terms of direct current and alternating current.FIG. 7is a diagram for illustrating a scheme for newly installing the photovoltaic module S, the power conditioner C, and the power storage device33. In the scheme shown inFIG. 7, the grid interconnection device100is used which has a bidirectional DC/DC converting unit and a bidirectional DC/AC converting unit in place of the power conditioner C and the converters shown inFIGS. 6A to 6D.

In contrast, when the power supply device32is an alternating current power supply (a wind turbine generator, for example), the controller104converts the alternating current power outputted by the power supply device32into direct current power by using a rectifier circuit and then converts the resultant direct current power into predetermined alternating current power by using an inverter circuit for the purpose of synchronization with the alternating current power of the power distribution system50. Alternately, the controller104converts the alternating current power outputted by the power supply device32into predetermined alternating current power by using a matrix converter circuit, a cycloconverter circuit, or the like.

(Operation of Grid Interconnection Device)

Hereinafter, an operation of the grid interconnection device according to the first embodiment will be described with reference toFIG. 8.FIG. 8is a flowchart showing determination processing of the grid interconnection device100according to this embodiment.

As shown inFIG. 8, in step S10, the grid interconnection device100receives the first and second adjustment instructions (hereinafter, simply called “the instructions”) through a predetermined path.

In step S11, the grid interconnection device100determines whether or not the entire instruction is received through the predetermined path. If the entire instruction is received, the processing moves to step S12. If the entire instruction is not received, the processing moves to step S14.

In step S12, the grid interconnection device100determines whether or not the own group is designated as the application group indicated by the group information. If the own group is designated as the application group, the processing moves to step S13. If the own group is not designated as the application group, the processing terminates.

In step S13, the grid interconnection device100controls the backward flow power and the power storage amount on the basis of the instruction.

In step S14, the grid interconnection device100determines whether or not a predetermined reception wait time has passed or not. If the reception wait time has passed, the processing moves to step S15. If the reception wait time has not passed, the processing returns to step S10

In step S15, the grid interconnection device100issues a reception error indicating a failure to receive the instruction through the predetermined path. A user may be notified of the reception error by a warning sign or an alarm, for example.

FIG. 9is a flowchart showing processing of controlling the backward flow power by the grid interconnection device100according to the first embodiment.

As shown inFIG. 9, in step S20, the grid interconnection device100determines if the backward flow request amount is larger than zero, by referring to the electric power information included in the first adjustment instruction. If the backward flow request amount is larger than zero, the processing moves to step S21. If the backward flow request amount is zero or less, the backward flow power is stopped in step S25and the processing terminates.

In step S21, the grid interconnection device100determines if the power storage amount in the power storage device33is equal to or larger than the backward flow request amount. If the power storage amount of the power storage device33is equal to or larger than the backward flow request amount, the processing moves to step S23. If the power storage amount of the power storage device33is smaller than the backward flow request amount, the processing moves to step S24.

In step S23, the grid interconnection device100causes the power storage device33to output electric power in accordance with the backward flow request amount.

In step S24, the grid interconnection device100causes the power supply device32to output electric power in accordance with the backward flow request amount.

In step S25, the grid interconnection device100reversely provides the backward flow power to the power distribution system50.

FIG. 10is a flowchart showing another type of processing of controlling the backward flow power by the grid interconnection device100. A different point from the aforementioned processing inFIG. 9is that the processing inFIG. 10includes step S30, in place of S24, of reducing the power supply from the power supply device32to the power consumption device31. With this step, by reducing power supply to the power consumption device31, more output power of the power supply device32can be used as backward flow power.

In the grid interconnection device100according to the first embodiment, the receiver101receives the second adjustment instruction transmitted before the first adjustment instruction. The controller104controls the power storage amount on the basis of the second adjustment instruction.

Specifically, in the first embodiment, the first adjustment instruction is the backward flow provide request, and the second adjustment instruction is the charge request. For this reason, electric power can be stored in advance for the case where the consumed power reaches a peak in a particular time period. Therefore, by using the electric power stored in the power storage device33, the backward flow power can be increased up to a desired amount in the particular time period.

Moreover, the plural customers30are grouped into plural groups G, and the first and second adjustment instructions specify the application groups Gp to which the first and second adjustment instructions are applied. The controller104controls the backward flow power and the power storage amount when the determination unit determines the own group as the application group.

Accordingly, one group G and another group G are controlled by different instructions. Therefore, the amounts of backward flow can be controlled equally among the groups G. Specifically, as shown in Table 1, the amounts of backward flow among the groups G can be equalized by rotating the backward flow approval B and the backward flow disapproval C among the groups G.

[Modification of First Embodiment]

A modification of the first embodiment will be described below with reference toFIG. 11. Hereinafter, the description will be given mainly for the difference between this modification and the first embodiment.

Specifically, in the first embodiment, the plural customers30are grouped so that the total amounts of backward flow power from the respective groups G can be almost equal to each other. In contrast, in this modification, plural customers30are grouped so that the backward flow power from each of the groups G to the power distribution system50can be stable.

(Configuration of Power Control System)

Hereinafter, a configuration of a power control system according to the modification of the first embodiment will be described in reference toFIG. 11.FIG. 11is a schematic diagram showing a configuration of a power control system1according to this modification.

As shown inFIG. 11, plural customers30includes a variation-type customer30aprovided with a power supply device32having high possibility of power output fluctuation due to changes of the weather and the like and a stable-type customer30bprovided with a power supply device32having low possibility of power output fluctuation due to changes of the weather and the like. The groups G1to G3each include the stable-type customer30b.

The power supply device32having high possibility of power output fluctuation is, for example, a power supply device of an environment-friendly clean energy type such as a photovoltaic power generator and a wind turbine generator. The power supply device32having low possibility of power output fluctuation is, for example, a power supply device of a reliable supply type of power supply device such as a gas engine generator and a fuel cell power generator having no power output fluctuation caused by weather conditions and the like.

Here, a total rated output power (approximately 10 kW, for example) of the power supply devices32of the respective customers30included in the group G2is substantially equal to a sum of a total rated output power (approximately 4 kW, for example) of the power supply devices32of the respective customers30included in the group G1and a total rated output power (approximately 6 kW, for example) of the power supply devices32of the respective customers30included in the group G3.

Next, an example of what are instructed by the first and second adjustment instructions transmitted from the substation20to the groups G will be described using the table below.

As shown in the table above, the backward flow provide request A is transmitted to the groups G1to G3in the daytime (from 12 to 15 o'clock) when the consumed power reaches a peak. In preparation for this, during the nighttime (0 to 7 o'clock), the charge request P is transmitted to the groups G1to G3. In the morning (8 to 12 o'clock) and in the afternoon (15 to 17 o'clock), the backward flow approval B and the backward flow disapproval C are rotated so that the groups G1and G3can have a different rotation from the group G2.

According to the modification of the first embodiment, each group G includes the variation-type customer30aand the stable-type customer30b. Therefore, even if a weather change occurs, each group G can stably provide the backward flow power to the power distribution system50from the stable-type customer30b.

In addition, the customers30are grouped so that the total rated output power of the two groups G1and G3may be substantially equal to the total rated output power of the group G2. The backward flow approval B and the backward flow disapproval C are rotated so that the groups G1and G3can have a different rotation from the group G2. Therefore, the amounts of backward flow are fairly distributed among the groups G.

Next, a second embodiment of the present invention will be described. In the second embodiment, descriptions will be given for the case where the output power of a power supply device32provided to each customer30reaches a peak in the daytime. In such a case, the voltage of a power distribution system50might rise excessively, and hence reducing the backward flow power and increasing the forward flow power in the daytime are desired.

Hereinafter, descriptions are given mainly on the different points from the aforementioned first embodiment. Specifically, what are instructed by the first and second adjustment instructions is rotated differently in the second embodiment. An example of what are instructed by the first and second adjustment instructions transmitted from a substation20to the groups G will be described using the table below.

In the table below, the first adjustment instruction includes the backward flow approval B, the backward flow disapproval C, and the forward flow receive request D, and the second adjustment instruction includes only the discharge request Q. The forward flow receive request D requests an increase of the amount of forward flow, and is included in the first adjustment instruction along with the backward flow disapproval C. Note that forward flow power information indicating the forward flow power may be included in the first adjustment instruction.

As shown in the table above, from the morning until the early evening (8 to 16 o'clock), the backward flow approval B and the backward flow disapproval C are transmitted while being rotated among the groups G1to G3so that the groups G1to G3can provide the backward flow equally.

In the daytime when the output power reaches a peak (10 to 14 o'clock), the backward flow disapproval C is transmitted to two or more groups G out of the three groups G in order to suppress a voltage rise of the power distribution system50. Moreover, the forward flow receive request D is transmitted along with the backward flow disapproval C in order to suppress the voltage rise more effectively by storing the forward flow power in a power storage device33.

From the early evening until the morning (16 to 7 o'clock), the discharge request Q is transmitted to the groups G1to G3in order to increase an available storage capacity of the power storage device33in preparation for power storage from the morning until the early evening (8 to 16 o'clock).

Upon receipt of the backward flow approval B in the next time period after receiving the backward flow disapproval C and the forward flow receive request D, a grid interconnection device100may preferentially provide the backward flow from the power storage device33in order to increase the available storage capacity of the power storage device33in preparation for the case of receiving “C+D” in the subsequent next time period. Alternatively, the substation20may transmit the backward flow approval B and the discharge request Q in the next time period after transmitting the backward flow disapproval C and the forward flow receive request D. In this case, the grid interconnection device100provides the backward flow from the power storage device33in accordance with the discharge request Q.

(Operation of Grid Interconnection Device)

Hereinafter, the operation of the grid interconnection device according to the second embodiment will be described in reference toFIG. 12.FIG. 12is a flowchart showing processing of controlling the backward flow power by the grid interconnection device100according to the second embodiment.

As shown inFIG. 12, in step S30, the grid interconnection device100determines if the backward flow power is zero or smaller, by referring to the backward flow power information or forward flow power information included in the first adjustment instruction. If the backward flow power is zero (backward flow disapproval) or smaller than zero (forward flow receive request), the processing moves to step S31. If the backward flow power is larger than zero, the backward flow power is transmitted in step S35and the processing terminates.

In step S31, the grid interconnection device100reduces the output power of the power supply device32in order to prevent the available storage capacity of the power storage device33from being zero. However, if the customer30does not include the power supply device32, the processing in step S32is not executed.

In step S32, the grid interconnection device100determines if the backward flow power is zero. If the backward flow power is zero, the processing moves to step S33. If the backward flow power is not zero, in other words, if the forward flow power is larger than zero, the processing moves to step S34.

In step S33, the grid interconnection device100stores the output power of the power supply device32in the power storage device33. Accordingly, the backward flow power is reduced.

In step S34, the grid interconnection device100stores the output power of the power supply device32and the forward flow power from the power distribution system50in the power storage device33.

In the grid interconnection device100according to the second embodiment, the receiver101receives the second adjustment instruction transmitted before the first adjustment instruction. The controller104controls the power storage amount on the basis of the second adjustment instruction.

Specifically, in the second embodiment, the first adjustment instruction includes the backward flow disapproval C, and the second adjustment instruction is the discharge request Q. Accordingly, the power storage device33of each customer30can be discharged in advance in preparation for the case where the backward flow power reaches a peak in a particular time period. Therefore, the backward flow power can be reduced down to the desired amount in the particular time period by storing the output power of the power supply device32in the power storage device33in the particular time period.

In addition, the backward flow approval B and the backward flow disapproval C are rotated among the groups G as shown in Table 3, and thereby the amount of backward flow among the groups G can be equalized.

Moreover, the first adjustment instruction includes the backward flow disapproval C and the forward flow receive request D. Therefore, the voltage rise of the power distribution system50is effectively suppressed by storing the forward flow power in the power storage device33.

Hereinafter, a third embodiment of the present invention will be described. In the third embodiment, a customer30includes a display unit configured to display information on a power control system1.

FIG. 13is a block diagram showing a configuration of the customer30according to the third embodiment. As shown inFIG. 13, the customer30includes a display unit34. The display unit34is connected to a grid interconnection device100. Incidentally, the display unit34may be provided in the grid interconnection device100.

Display items of the display unit34are, for example, (1) the content of the present adjustment instruction, (2) the content of the next adjustment instruction, (3) information on backward flow power and forward flow power, (4) a remaining time until the next adjustment instruction, (5) statuses of electricity trading, (6) operation statuses of the power distribution system.

A user can check on the operating conditions of his/her own customer by observing the display items (1) to (5) of the display unit34.

In addition, a user can check if the groups G are given equal opportunity for the backward flow by observing the display item (6) of the display unit34. In the example ofFIG. 14B, the user can check that the group G4is under the backward flow disapproval whereas the group G3is under the backward flow approval in the current time period; and that the groups G4is under the backward flow approval whereas the group G3is under the backward flow disapproval in the previous time period. Accordingly, the users of the group G3and the group G4can observe that the backward flows are equally provided, and thereby can be made more convinced of the fairness in electricity trading.

Hereinafter, a fourth embodiment of the present invention will be described. In the fourth embodiment, the details of the first method explained in the first embodiment will be described.

As described above, the first method is the method of calculating how much amount of backward flow power from each customer30should be obtained to resolve a shortage of power, on the basis of a voltage drop tendency (voltage drop range Δv/time duration Δt) in a power distribution system50, the contract capacity, the rated output power of a power supply device32, and the power storage capacity of a power storage device33.

FIG. 15is a block diagram showing a configuration of a substation20according to the fourth embodiment. As shown inFIG. 15, the substation20includes a detector24, a receiver25, a storage26, and a calculator27in addition to a power distribution controller21, an instruction generator22, and a transmitter23described in the first embodiment.

The detector24detects the voltage value of the power distribution system50in the substation20. The voltage value detected by the detector24is stored in the storage26.

The receiver25receives measured voltage values at a step voltage regulator (SVR), a pole transformer, and the like that are provided in the power distribution system50between the substation20and the customers30. Alternatively, the receiver25receives measured voltage values at grid interconnection points at each of which a grid interconnection device100of one customer30is connected to the power distribution system50. The voltage values (measured voltage values) received by the receiver25are stored in the storage26.

The storage26stores the contact capacity, the rated output power of the power supply device32, and the power storage capacity of the power storage device33. For example, at the time of power-receiving contract with each customer30, or at the time of contract of installing the power supply device32and the power storage device33, the storage26can store the contact capacity, the rated output power of the power supply device32, and the power storage capacity of the power storage device33on the basis of information which each customer30provides to companies which provide and manage the power distribution system50(an owner or an operator of a power network, an operation manager of a power transmission and distribution system).

The calculator27calculates how much amount of backward flow power should be obtained to resolve the shortage of power on the basis of a history of the voltage values of the power distribution system50that is stored in the storage26, as well as the contact capacity, the contract capacity, the rated output power of the power supply device32, and the power storage capacity of the power storage device33that are stored in the storage26. The details of the method of calculating the amount of backward flow power capable of resolving the shortage of power (hereinafter, referred to as a desired amount of backward flow power) will be described later.

The calculator27determines an estimated obtainable power amount Wgetfor each customer30by use of the desired amount of backward flow power thus calculated.

The instruction generator22incorporates the estimated obtainable power amount Wgetfor each customer30in the first adjustment instruction as the aforementioned backward flow power information.

The configuration of this embodiment except the point above is the same as the aforementioned first embodiment.

The calculator27calculates the desired amount of backward flow power in accordance with the following calculation method 1 and/or calculation method 2. First, the calculation method 1 will be described.

The calculator27obtains the history of the voltage values of the power distribution system50, and then calculates a voltage drop tendency (voltage drop range Δv/time duration Δt) in the power distribution system50. The calculator27calculates a total estimated consumable power amount ΣWconsuntil a predetermined time, which is an estimated amount of power that may be consumed by all the customers30, on the basis of the calculated voltage drop tendency.

In addition, the calculator27calculates a total estimated obtainable power amount ΣWget, which is an estimated amount of total backward flow power that may be provided from all the customers30, on the basis of the contract capacity, the rated output power of the power supply device32, and the power storage capacity of the power storage device33which are stored in the storage26.

The calculator27determines, as the desired amount of backward flow power, the total estimated obtainable power amount ΣWgetwhose difference from the calculated total estimated consumable power amount ΣWconsfalls within a desired range, and then determines the estimated obtainable power amount Wgetfor each customer30by use of the desired amount of backward flow power.

Next, a calculation method 2 will be described.

The calculator27obtains the history of the voltage values of the power distribution system50from the storage26, and then calculates the voltage drop tendency (voltage drop range Δv/time duration Δt) in the power distribution system50. The calculator27calculates time tdownrequired for a voltage value drop to the voltage drop limit value, on the basis of the calculated voltage drop tendency. Here, the voltage drop limit value is a voltage value of the lower limit of a proper voltage range (seeFIG. 3) +α.

Moreover, the calculator27calculates time tgetrequired for a voltage value rise from the voltage drop limit value to the present voltage value when each customer30outputs the maximum backward flow power.

Then, the calculator27determines time ttunethat is necessary to make a difference between the time tdownrequired for a voltage value drop to the voltage drop limit value, and the time tgetrequired for a voltage value rise from the voltage drop limit value to the present voltage value fall within a predetermined range. The calculator27regards the amount of backward flow power from each customer30during time ttuneas a desired amount of backward flow power. The calculator27calculates the estimated obtainable power amount Wgetfor each customer30from the desired amount of backward flow power.

In the substation according to the fourth embodiment, the calculator27calculates the desired amount of backward flow power on the basis of the history of the voltage values of the power distribution system50, and then calculates the estimated obtainable power amount Wgetfor each customer30from the desired amount of backward flow power. The instruction generator22generates the first adjustment instruction including the backward flow power information indicating the estimated obtainable power amount Wgetcalculated by the calculator27. This allows an appropriate calculation of the desired amount of backward flow power, and thus the shortage of power is resolved during a time period when the consumed power reaches a peak.

Hereinafter, a fifth embodiment of the present invention will be described. In the fifth embodiment, descriptions will be given for a case1of the second method described in the first embodiment.

The case1of the second embodiment is a method of calculating a desired amount of backward flow power in consideration of weather conditions on the day (real-time data, forecast data, and the like), and season, time and calendar information.

A configuration of the substation20according to the fifth embodiment will be described with reference toFIG. 15.

The receiver25or the detector24in the substation20obtains any one of the following data as weather observation data:pinpoint weather forecast data in an area where the substation20is located;weather observation data at the substation20;weather observation data at a step voltage regulator (SVR), a pole transformer, and the like arranged in the power distribution system50between the substation20and the customers30; andweather observation data at each grid interconnection point where the grid interconnection device100and each power distribution system50area connected.

Note that the “area where the substation20is located,” which is targeted for the pinpoint weather forecast data may include an area where the power distribution system50under the management of the substation20and/or each customer30are located

Moreover, the receiver25of the substation20receives the season, time and calendar information through data broadcasting (digital broadcasting, BS broadcasting, CS broadcasting, CATV, and the like), a radio clock, or the Internet. Alternatively, the receiver25may obtain the season, time and calendar information by use of a built-in timer (not shown) of the substation20.

The storage26cumulatively stores weather observation data having the time and calendar information added thereto as shown inFIG. 16. In the example ofFIG. 16, the weather observation data includes items of temperature, humidity, weather, wind direction, and wind velocity.

The storage26stores the contract capacity, the rated output power of the power supply device32, and the power storage capacity of the power storage device33. For example, at the time of power-receiving contract with each customer30, or at the time of contract of installing the power supply device32and the power storage device33, the storage26can store the contact capacity, the rated output power of the power supply device32, and the power storage capacity of the power storage device33on the basis of information which each customer30provides to companies (a power company and the like) which provide and manage the power distribution system50(an owner or an operator of a power network, an operation manager of a power transmission and distribution system).

The calculator27calculates the desired amount of backward flow power on the basis of the history of the weather observation data, the contact capacity, the rated output power of the power supply device32, and the power storage capacity of the power storage device33, which are stored in the storage26. The details of methods of calculating the desired amount of backward flow power will be described later.

FIG. 17is a flowchart showing an operation of calculating the desired amount of backward flow in the substation20according to the fifth embodiment.

In step S110, the calculator27calculates the total estimated consumable power amount ΣWcons.

In step S120, the calculator27calculates the total estimated obtainable power amount ΣWget.

In step S130, the calculator27calculates the difference ΔW between the calculated total estimated consumable power amount ΣWconsand the calculated total estimated obtainable power amount ΣWget.

If the difference ΔW is out of a predetermined range (step S140: NO) and is larger than zero (step S150: YES), the calculator27performs processing for increasing the estimated obtainable power amount Wgetin step S160in order to resolve the shortage of the amount of backward flow power. Specifically, the calculator27increases the estimated obtainable power amount Wgetby changing the type of the power supply device32to a type “having the rated output power larger than a predetermined value” or “a reliable supply type,” or by increasing the output of the power storage device33.

If the difference ΔW is out of the predetermined range (step S140: NO) and is zero or smaller (step S150: NO), the calculator27performs processing for reducing the estimated obtainable power amount Wgetin step S170in order to resolve excess of the amount of backward flow power. Specifically, the calculator27reduces the estimated obtainable power amount Wgetfor any one of the customers30.

When step S160or step S170is completed, the processing returns to step S120.

On the other hand, if the difference ΔW is within the predetermined range (step S140: YES), the calculator27determines the total estimated obtainable power amount ΣWgetcalculated in step S120as the desired amount of backward flow power in step S180.

In step S190, the calculator27determines the estimated obtainable power amount Wgetfor each customer30by use of the desired amount of backward flow power determined in step S180.

In step S200, the instruction generator22generates the first adjustment instruction on the basis of the estimated obtainable power amount Wgetfor each customer30determined in step S190, and the transmitter23transmits the generated first adjustment instruction.

Next, details of the processing of calculating the total estimated consumable power amount ΣWcons(step S110inFIG. 17) will be described.FIG. 18is a flowchart showing the details of step S110inFIG. 17. The flow inFIG. 18is performed for each customer30.

In step S111, the calculator27determines a predetermined time period targeted for calculating the desired amount of backward flow power.

In step S112or step S113, the calculator27generates the weather forecast data for the predetermined time period by referring to the history of the weather observation data stored in the storage26.

As for the way of generating the weather observation data, the calculator27can read out from the storage26the weather observation data for several hours before the predetermined time period, and generate the weather forecast data by deriving a tendency of weather changes. Alternatively, the calculator27can read out from the storage26the weather observation data for the predetermined time period in the past several years and generate the weather forecast data by use of the read-out weather observation data in the past several years.

Note that, if the weather forecast data are transmitted through TV broadcasting, data broadcasting, CS broadcasting, the internet, dedicated lines, or the like, the receiver25may obtain the weather forecast data for the predetermined time period by receiving the transmitted weather forecast data.

In steps S114to S117, the calculator27calculates an estimated consumable power amount Wconsof the customer30on the basis of the weather forecast data for the predetermined time period and the contract capacity of the customer30stored in the storage26.

For example, if the season is summer (June to September), in step S115the calculator27calculates consumed power of an air conditioner at cooling mode, a cooler, and ice machine and so on as the estimated consumable power amount Wcons, from the difference between the weather forecast data (temperature and humidity) for the predetermined time period and a set temperature and a set humidity.

If the season is winter (December to February), in step S116the calculator27calculates consumed power of an air conditioner at heating mode, an electric heater, an electric boiler and so on as the estimated consumable power amount Wcons, from the difference between the weather forecast data (temperature and humidity) for the predetermined time period and a set temperature and a set humidity.

If the season is an intermediate term (March to May, October, and November), in step S117the calculator27calculates consumed power of such as an air conditioner at auto mode or at dry mode as the estimated consumable power amount Wcons, from the difference between the weather forecast data (temperature and humidity) for the predetermined time period and a set temperature and a set humidity.

The calculator27calculates the total estimated consumable power amount ΣWconsby adding up the estimated consumable power amounts ΣWconsfor all the customers30.

Next, the processing of calculating the total estimated obtainable power amount ΣWget(details of step S120inFIG. 17) will be described.FIG. 19is a flowchart showing the details of step S120inFIG. 17. A flow inFIG. 19is performed for each customer30.

In step S121, the calculator27refers to the weather forecast data for the predetermined time period, which is generated in step S113inFIG. 18.

In step S122, the calculator27refers to the rated output power of the power supply device32, which is stored in the storage26.

In step S123, the calculator27refers to the power storage capacity of the power storage device33, which is stored in the storage26.

In steps S124to5127, the calculator27calculates the estimated consumable power amount Wconsof the customer30on the basis of the weather forecast data for the predetermined time period, the rated output power of the power supply device32, and the power storage capacity of the power storage device33.

For example, if the power supply device32is a photovoltaic power generator and the amount of insolation shown by the weather forecast data is large (namely, “sunny”), the calculator27sets output power Wget1of the power supply device32of the customer30to the rated output power in step S125. If the customer30includes the power storage device33, the calculator27sets output power Wget2of the power storage device33of the customer30to the power storage capacity.

If the power supply device32is the photovoltaic power generator and the amount of insolation shown by the weather forecast data is approximately half of the maximum amount (namely, “cloudy”), the calculator27sets the output power Wget1of the power supply device32of the customer30to half of the rated output power in step S126. If the customer30includes the power storage device33, the calculator27sets the output power Wget2of the power storage device33of the customer30to half of the power storage capacity. This is because the charge request is already made by the second adjustment instruction, and the amount of insolation shown by the weather forecast data is approximately half of the maximum amount (“cloudy”).

If the power supply device32is the photovoltaic power generator and the amount of insolation shown by the weather forecast data is small (namely, “rainy or snowy”), the calculator27sets the output power Wget1of the power supply device32of the customer30to one tenth of the rated output power in step S127. If the customer30includes the power storage device33, the calculator27sets the output power Wget2of the power storage device33of the customer30to one tenth of the power storage capacity.

Then, the estimated obtainable power amount Wgetof the customer30is equal to Wget1+Wget2obtained in the above way.

The calculator27calculates the total estimated consumable power amount ΣWconsby adding up the estimated obtainable power amounts Wgetfor all the customers30.

In this operation flow, the power storage capacity of the power storage device33is considered. However, the estimated obtainable power amount Wgetmay be calculated based on the rated output power of the power supply device32without considering the power storage capacity of the power storage device33.

In this example, the amount of insolation in the cloudy weather is assumed as half of the maximum amount, and the amount of insolation in the rainy or snowy weather is assumed as one tenth of the maximum amount. However, these amounts of insolation are merely examples, and may be set to different values.

In the substation20according to the fifth embodiment, the calculator27calculates the desired amount of backward flow power on the basis of weather conditions, and calculates the estimated obtainable power amount Wgetfor each customer30, from the desired amount of backward flow power. The instruction generator22generates the first adjustment instruction including the backward flow power information that indicates the estimated obtainable power amount Wgetcalculated by the calculator27. Accordingly, the desired amount of backward flow power can be properly calculated, and the shortage of power can be resolved in the time period when the consumed power reaches a peak.

Hereinafter, a modification of the fifth embodiment of the present invention will be described. In the modification of the fifth embodiment, descriptions will be given for a case2of the second method described in the first embodiment.

The case2of the second method is a method of calculating a desired amount of backward flow power in consideration of the presence or absence of: an event such as a sportscast (an increase in power consumption by using power consumption devices such as an air conditioner and a television set in the customer for watching of a live high school baseball broadcast in midsummer, an Olympic games broadcast, and the like); or an event in a power distribution system50(an increase in power consumption at a venue for a concert or the like and neighboring facilities).

A configuration of the substation20according to the modification of the fifth embodiment will be described with reference toFIG. 15. Here, descriptions will be given for different points from the fifth embodiment.

The receiver25of the substation20receives, as event information of a sportscast or the like, program listings for digital broadcasting, program listings for the internet, the internet information on event facilities within a coverage area of the power distribution system50, or data broadcasting through CATV, for example.

In this modification, the method of calculating the total estimated consumable power amount ΣWconsis different from that in the fifth embodiment.FIG. 20is a flowchart showing a method of calculating the total estimated consumable power amount ΣWconsaccording to the modification of the fifth embodiment. The flow inFIG. 20is performed for each customer30.

In step S301, the receiver25receives, as the event information of a sportscast or the like, program listings for digital broadcasting, program listings for the internet, the internet information on event facilities within a coverage area of the power distribution system50, or data broadcasting through CATV, for example.

In step S302, the calculator27checks whether or not there a target event in the event information received by the receiver25. Here, the target event is an event that influences the total estimated consumable power amount ΣWcons, and that is represented by Olympic games broadcast in the summer, and the like. Information for specifying the target event may be stored in advance in the storage26, for example.

If there is a target event (step S302: YES), the processing moves to step S111. If there is no target event (step S302: NO), the processing is held in a wait condition for a certain time period in step S303, and then returns to step S301.

The processing after this is the same as the processing in steps S111to S117inFIG. 18.

In the substation20according to the modification of the fifth embodiment, the calculator27calculates the desired amount of backward flow power on the basis of a predetermined event, and calculates the estimated obtainable power amount Wgetfor each customer30, from the desired amount of backward flow power. The instruction generator22generates the first adjustment instruction including the backward flow power information indicating the estimated obtainable power amount Wgetcalculated by the calculator27. Accordingly, the desired amount of backward flow power can be properly calculated, and the shortage of power can be resolved in the time period when the consumed power reaches a peak.

Hereinafter, a sixth embodiment of the present invention will be described. In the sixth embodiment, descriptions will be given for details of the third method described in the first embodiment.

The third method is a method of calculating how much amount of backward flow power from the customer30should be obtained to resolve the shortage of power, on the basis of the amount of forward flow/backward flow calculated from, for example, the type and the rated output power of the power supply device32provided to each customer30, in addition to the weather conditions on the day mentioned in the second method.

A configuration of the substation20according to the sixth embodiment will be described with reference to theFIG. 15.

The receiver25or the detector24obtains the weather observation data as described above.

The receiver25of the substation20receives season, time and calendar information through data broadcasting (digital broadcasting, BS broadcasting, CS broadcasting, CATV, and the like), a radio clock, or the internet. Alternatively, the receiver25may obtain the season, time and calendar information by use of a built-in timer (not shown) of the substation20.

The storage26cumulatively stores weather observation data having time and calendar information added thereto as shown inFIG. 16. In the example ofFIG. 16, the weather observation data includes items of temperature, humidity, weather, wind direction, and wind velocity.

The storage26stores the type and the rated output power of the power supply device32of each customer30. For example, at the time of power-receiving contract, or at the time of contract of installing the power supply device32and the power storage device33, the storage26can store the type and the rated output power of the power supply device32of each customer30on the basis of information which each customer30provides to companies (a power company and the like) which provide and manage the power distribution system50.

The calculator27calculates the estimated consumable power amount Wconsfor each customer30from a history of the weather observation data stored in the storage26, and then calculates the total estimated consumable power amount ΣWcons. The calculator27calculates the estimated obtainable power amount Wgetfrom the type and the rated output power of the power supply device32of each customer30, which are stored in the storage26, and then calculates the total estimated obtainable power amount ΣWgetfor each customer30.

Then, the calculator27calculates, as the desired amount of backward flow power, the total estimated obtainable power amount ΣWgetwhose difference from the total estimated consumable power amount ΣWconsfalls within the desired range and then calculates the estimated obtainable power amount Wgetfor each customer30.

Hereinafter, a seventh embodiment of the present invention will be described. In the seventh embodiment, descriptions will be given for details of the fourth method described in the first embodiment.

The fourth method is a method of calculating how much amount of backward flow power from the customer30should be obtained to resolve the shortage of power, on the basis of the amount of forward flow/backward flow calculated from, for example, the forecast information derived from the past power usage history or the like and the type and the rated output power of the power supply device32provided to each customer30, as described above.

A configuration of the substation20according to the seventh embodiment will be described with reference toFIG. 15.

The receiver25receives data on power usage amount of each customer30. For example, the receiver25receives power data of an electricity meter (a smart meter, and the like) of each customer30. The detector24detects the power usage amount of each customer30from a power state of the power distribution system50.

The storage26cumulatively stores the data of the power usage amount obtained by the receiver25and/or the detector24.

In addition, the storage26stores the type and the rated output power of the power supply device32of each customer30. For example, at the time of power-receiving contract, or at the time of contract of installing the power supply device32and the power storage device33, the storage26can store the type and the rated output power of the power supply device32of each customer30on the basis of information which each customer30provides to companies (a power company and the like) which provide and manage the power distribution system50.

The calculator27predicts data transitions from a history of the power usage amounts stored in the storage26, thereby calculates the estimated consumable power amount Wconsfor each customer30, and then calculates and the total estimated consumable power amount ΣWcons. The calculator27calculates the estimated obtainable power amount Wgetfor each customer30from the type and the rated output power of the power supply device32of the customer30stored in the storage26, and then calculates the total estimated obtainable power amount ΣWget.

Then, the calculator27calculates, as the desired amount of backward flow power, the total estimated obtainable power amount ΣWgetwhose difference from the total estimated consumable power amount ΣWconsfalls within the predetermined range, and then calculates the estimated obtainable power amount Wgetfor each customer30.

In the seventh embodiment, the overall flow of the method of calculating the desired amount of backward flow power is the same as that of the fifth embodiment (FIG. 17). However, the methods of calculating the total estimated consumable power amount ΣWconsand the total estimated obtainable power amount ΣWgetare different from those of the fifth embodiment.

FIG. 21is a flowchart showing a method of calculating the total estimated consumable power amount ΣWconsaccording to the seventh embodiment. The flow inFIG. 21is performed for each customer30.

In step S411, the calculator27determines a predetermined time period targeted for calculation of a desired amount of backward flow power.

In steps S412and S413, the calculator27refers to the history of the power usage amount stored in the storage26, and calculates the estimated consumable power amount Wconsfor the predetermined time period.

The calculator27calculates the total estimated consumable power amount ΣWconsby adding up the estimated consumable power amount Wconsfor all the customers30.

FIG. 22is a flowchart showing a method of calculating the total estimated obtainable power amount ΣWgetaccording to the seventh embodiment. The flow inFIG. 22is performed for each customer30.

In step S421, the calculator27refers to the type and the rated output power of the power supply device32, which are stored in the storage26.

In step S422, the calculator27refers to the power storage capacity of the power storage device33, which is stored in the storage26.

In steps S423to S426, the calculator27calculates the estimated obtainable power amount Wgetof the customer30on the basis of the type and the rated output power of the power supply device32and the power storage capacity of the power storage device33.

For example, if the power supply device32is a type “having the rated output power larger than a predetermined value,” the calculator27sets the output power Wget1of the power supply device32of the customer30to the rated output power in step S424. If the customer30includes the power storage device33, the calculator27sets the output power Wget2of the power storage device33of the customer30to the power storage capacity.

If the power supply device32is a “clean energy type,” the calculator27sets the output power Wget1of the power supply device32of the customer30to half of the rated output power in step S425. If the customer30includes the power storage device33, the calculator27sets the output power Wget2of the power storage device33of the customer30to half of the power storage capacity.

If the power supply device32is a “reliable supply type,” the calculator27sets the output power Wget1of the power supply device32of the customer30to the rated output power in step S426. If the customer30includes the power storage device33, the calculator27sets the output power Wget2of the power storage device33of the customer30to the power storage capacity. Here, the output power Wget1and the output power Wget2in the case of the power supply device32of the “clean energy type” is set to half of the rated output power and half of the power storage capacity, respectively; however, these values are merely examples, and different values may be used.

The estimated obtainable power amount Wgetof the customer30is equal to Wget1+Wget2obtained in the above methods.

The calculator27calculates the total estimated consumable power amount ΣWconsby adding up the estimated obtainable power amount Wgetfor all the customers30.

In this flow, the power storage capacity of the power storage device33is considered. However, the estimated obtainable power amount Wgetmay be calculated on the basis of the rated output power of the power supply device32without considering the power storage capacity of the power storage device33.

In the substation20according to the seventh embodiment, the calculator27calculates the desired amount of backward flow power on the basis of the history of the power usage amount of each customer30, and calculates the estimated obtainable power amount Wgetfor each customer30, from the desired amount of backward flow power. The instruction generator22generates the first adjustment instruction including the backward flow power information that indicates the estimated obtainable power amount Wgetcalculated by the calculator27. Accordingly, the desired amount of backward flow power can be properly calculated, and the shortage of power can be resolved in the time period when the consumed power reaches a peak.

The present invention has been described above using the embodiments of the present invention. It should be understood, however, that the descriptions and the drawings that constitute part of the disclosure do not limit the present invention. This disclosure will make various alternative embodiments, examples, and operation techniques apparent to those skilled in the art.

For example, the instruction is transmitted to each customer30through the two transmission paths in the above-described embodiments; however, the invention is not limited to this configuration. Specifically, the instruction may be transmitted through only one transmission path or through three or more transmission paths.

In addition, the data distribution segment in the terrestrial digital broadcasting is described as an example of the predetermined path for transmitting the instruction in the above-described embodiments; however, the invention is not limited to this configuration. For example, the instruction may be transmitted through BS broadcasting, CS broadcasting, CATV, analog TV broadcasting, radio broadcasting, cable broadcasting, a paging system, a mobile telephone network, wireless communications conforming to 802.11x (wireless LAN), the internet, and the like. Moreover, the instruction may be transmitted by being added to information used for setting the time of a radio clock, or may be transmitted to the customers30through a network. If the network is used, the instruction may be updated on a server at fixed intervals.

Moreover, the instruction is transmitted from the substation20in the above-described embodiments; however, the invention is not limited to this configuration. Specifically, the instruction may be transmitted from another apparatus (a power company, a broadcasting station, or the like).

In addition, in the aforementioned embodiments, the description has been given for the case where each customer30is provided with the power supply device32. However, each customer30may not be provided with the power supply device32. In this case, the processing of controlling the backward flow power in the grid interconnection device100may not include step S24inFIG. 9and step S32inFIG. 12.

Furthermore, although not particularly mentioned in the third embodiment, the grid interconnection device100may display on a display device the instruction received, conditions of the devices (the output power, the available storage capacity, the forward flow power (purchased electricity), the backward flow power (sold electricity), the transition graphs of these, or the like) in addition to the display items of the display unit34. A TV monitor, a PC monitor, and a mobile phone monitor are used as the display device. In addition, the grid interconnection device100may remove the code for hiding the instruction from the instruction added to network information received through TV reception waves, the Internet, and the like. Moreover, the grid interconnection device100may have a function of receiving information from a television, a personal computer, and a mobile phone. In this case, an instruction to reduce power supplied to the power consumption devices31and the like can be sent from the television, the personal computer, and the mobile phone.

In addition, although not particularly mentioned in the second embodiment, the plural customers30may be grouped into several groups G so that the backward flow power from the groups G to the power distribution system50can be stabilized as in the modification of the first embodiment.

The methods described in the fourth to seventh embodiments can be applied to the second embodiment as well.