Power system

Disclosed is an electric power system including a first unit (for example, a unit 201) equipped with a first power source (for example, a solar panel (201b)), a first rechargeable battery (for example, a unit storage battery (201c)) to which an output of the first power source is input, and a first power consuming portion (not shown) to which an output of the first rechargeable battery is input; a second rechargeable battery (for example, a shared storage battery (202)); and an electric power line (for example, a shared electric power line (203)) for sharing electric power between the first rechargeable battery and the second rechargeable battery.

TECHNICAL FIELD

The present invention relates to an electric power system.

BACKGROUND ART

Regarding electric power supply, various proposals are presented from a viewpoint of environmental load reduction. For instance, Patent Document 1 discloses a photovoltaic power generation system constituted of solar cells, a storage battery, and an interconnection inverter having a self sustaining function, which is operated as an interconnection photovoltaic power generation system when the system power supply is normal, and in a disaster situation the inverter is operated in a self sustaining mode using the solar cells and the storage battery as power sources so as to supply electric power to a specific load. In this photovoltaic power generation system, the inverter has a bidirectional function, and supplemental charging of the storage battery is performed with the system side electric power by operating the inverter in a converter mode when the system power supply is normal. It is also proposed that the supplemental charging of the storage battery should be performed after the interconnection photovoltaic power generation operation is stopped, and further that the supplemental charging of the storage battery should be performed during a time slot to which a midnight power rate is applied. In addition, Patent Document 2 proposes an electric power selling system by the photovoltaic power generation.

PRIOR ART DOCUMENTS

Patent Documents

DISCLOSURE OF THE INVENTION

Problem to be Solved by the Invention

However, regarding the electric power system, there are still various problems to be studied from a viewpoint of environmental load reduction.

In view of the above-mentioned problem, it is an object of the present invention to provide an electric power system that can contribute to environmental load reduction.

Means for Solving the Problem

In order to solve the above-mentioned problem, an electric power system of the present invention includes a first unit equipped with a first power source, a first rechargeable battery to which an output of the first power source is input, and a first power consuming portion to which an output of the first rechargeable battery is input; a second rechargeable battery; and an electric power line for sharing electric power between the first rechargeable battery and the second rechargeable battery (first structure).

Note that it is preferred that the electric power system according to the first structure should include a second unit equipped with a second power source, the second rechargeable battery to which an output of the second power source is input, and a second power consuming portion to which an output of the second rechargeable battery is input (second structure).

In addition, in the electric power system having the second structure, it is preferred that the first and second power sources should be solar panels (third structure).

In addition, in the electric power system having the second structure, it is preferred that the first and second power sources should be commercial electric power (fourth structure).

In addition, it is preferred that the electric power system having the third structure should further include a first electric power converting portion that converts an output from the commercial electric power into DC power and outputs the DC power to the first rechargeable battery (fifth structure).

In addition, in the electric power system having the second structure, it is preferred that the first power consuming portion should include a DC power consuming portion (sixth structure).

In addition, in the electric power system having the sixth structure, it is preferred that the DC power consuming portion should be an LED lighting fixture (seventh structure).

In addition, in the electric power system having the second structure, it is preferred that the first power consuming portion should have an AC power consuming portion (eighth structure).

In addition, it is preferred that the electric power system having the eighth structure should further include a second electric power converting portion that converts an output from the first rechargeable battery into AC power and outputs the AC power to the AC power consuming portion (ninth structure).

In addition, it is preferred that the electric power system having any one of the second to ninth structures should further include a third rechargeable battery that is connected to the electric power line and can interchange electric power with the first and second rechargeable batteries (tenth structure).

Effects of the Invention

As described above, according to the present invention, it is possible to provide the electric power system that can contribute to environmental load reduction by interchanging electric power among a plurality of storage batteries.

BEST MODE FOR CARRYING OUT THE INVENTION

First Example

FIG. 1is a block diagram of an electric power supply system according to an embodiment of the present invention. A first example is constituted as a multiple dwelling house such as a condominium2. InFIG. 1, a first home4and a second home6are illustrated as representatives of dwelling homes for simple illustration, but in reality many similar homes are dwelling in the condominium2. On the rooftop of the condominium2, there are disposed a photovoltaic power generation panel8, which is divided and sold as a first home panel10, a second home panel12, and so on. In addition, in the condominium2, AC power lines are drawn in the dwelling homes from a single-phase three-wire commercial electric power14.

Next, a detailed structure of the electric power supply system of the first example is described with reference to the first home4as an example. The first home panel10of the solar cell panel8is connected to a power conditioner18for the first home via a connection box16reserved for the first home. The power conditioner18includes a DC/DC converter20that converts DC electric power from the connection box16into the most effective voltage, and a DC/AC converter22that converts the same into AC electric power whose voltage is set a little higher than the highest voltage of the commercial AC power level. A photovoltaic power generation AC electric power output from the DC/AC converter22is connected to a sell power meter24and is sold to the single-phase three-wire commercial electric power14side via the sell power meter24and a time-slot buy power meter26. A price of the selling power is two times the usual buying power price. Note that the single-phase three-wire commercial electric power14can be usually supplied to the first home4via the time-slot buy power meter26and the sell power meter24as buying power when the photovoltaic power generation panel8cannot generate electric power or as buying power at the midnight power rate.

A control portion28controls various switches disposed in the system. Then, power generating state information of the power conditioner18and state information of the time-slot buy power meter26, which are necessary for the control, are input via connections denoted by P and Q inFIG. 1. The control portion28first controls an A-switch34disposed in a charging path connected from a DC/DC converter20of the power conditioner18to a storage battery32via a step-down portion30. Further, during daytime, if stored electricity in the storage battery32is short, the A-switch34is closed so that supplemental charging is performed by electric power generated by the photovoltaic power generation panel8. The storage battery32is provided basically for the purpose of storing electric power bought at the midnight power rate from the single-phase three-wire commercial electric power14and using the stored electric power in the first home4during time other than the time slot of the midnight power rate. For this purpose, the control portion28controls a B-switch36connected to the sell power meter24to be closed in the midnight power rate time slot so that the storage battery32is charged via an AC/DC converter and a step-down portion38. Note that the midnight power rate is set to ⅓ of the normal rate.

The electric power stored in the storage battery32is supplied to DC electrical appliances42via a DC distribution switchboard40. The DC electrical appliances42include an LED lighting fixture43and the like. The electric power stored in the storage battery32is further supplied to AC electrical appliances48from AC distribution switchboard46via a DC/AC converter and a step-up portion44. The AC electrical appliances48are general home appliances supplied with power from a normal home outlet. Note that in order to drive the AC electrical appliances48directly by the single-phase three-wire commercial electric power14during midnight power rate time slot or when electric power in the storage battery32is short during time other than the midnight power rate time slot, the control portion28controls to close a C-switch50connected between the sell power meter24and the AC distribution switchboard46.

The second home6has the same structure as the first home4, but for simple illustration, only typical elements are illustrated while other elements are omitted. As apparent fromFIG. 1, the second home6is equipped with a storage battery52similar to the storage battery32of the first home4, and interchange of charged electric power can be performed between the storage batteries. A price for the interchange is approximately the midnight power rate from the single-phase three-wire commercial electric power14plus loss costs in the conversion between AC and DC, and in charging and discharging the storage batteries32and52, which is largely lower than the normal electric power rate. For this purpose, a D-switch54for selling DC power and an E-switch56for buying DC power are connected to the DC distribution switchboard40, and are connected to the second home6via a DC sell/buy meter58. The sell power meter24, the time-slot buy power meter26, and the DC sell/buy meter58are connected to a profit-and-loss display portion60, which displays profit and loss in selling and buying power.

A switch62in the second home6for DC electric power interchange with the first home4has the same structure as the D-switch54and the E-switch56for buying DC power in the first home4, which are integrated for illustration. Note that the DC sell/buy meter of the second home6is not illustrated. The selling and buying of DC power is not actually a bilateral trade between the first home4and the second home6but a one-to-many trade among all dwelling homes in the condominium2. Therefore, individual homes are connected to a common DC line. As described above, the second home6and other homes (not shown) have the same structure as the first home4. Main structure of the second home6is as follows. The second home panel12of the photovoltaic power generation panel8is connected to a power conditioner66via a connection box64. A sell/buy power meter68is the same as the sell power meter24and the time-slot buy power meter26in the first home4, which are integrated for illustration. Then, the AC electric power bought via the sell/buy power meter68charges the storage battery52via a switch70. The AC/DC converter and the step-down portion are not illustrated. The photovoltaic power generation electric power from the power conditioner66is sold via the sell/buy power meter68and charges the storage battery52via a switch72. The step-down portion is not illustrated. Other detailed description and illustration are omitted, but the second home6has the same structure as the first home4.

FIG. 2shows states of the switches controlled by the control portion28.FIG. 2(A)is concerning the A-switch34, the B-switch36, and the C-switch50.FIG. 2(B)is concerning the D-switch54and the E-switch56. As apparent fromFIG. 2(A), the A-switch34for charging the storage battery32with the photovoltaic power generation electric power is closed if there is the photovoltaic power generation electric power and the electric power stored in the storage battery32is short, and is opened in other cases. Note that inFIG. 2(A), the parenthesized ON like “(ON)” means a case where the switch is supplementally closed. In other words, as described above, charging of the storage battery32is usually performed from the single-phase three-wire commercial electric power14at the midnight power rate, and the charging via the A-switch34is performed only supplementally in a case where electric power in the storage battery32is short during time other than the midnight power rate time slot.

The B-switch36is closed for charging the storage battery32from the single-phase three-wire commercial electric power14during the midnight power rate time slot, and is supplementally closed when electric power in the storage battery32is short during time after sunset without photovoltaic power generation before the midnight power rate time slot. The B-switch36is opened in other situations. On the other hand, the C-switch50is closed for driving the AC electrical appliances48by directly consuming electric power from the single-phase three-wire commercial electric power14during the midnight power rate time slot. This is because during the midnight power rate time slot, it is more efficient without power loss to drive directly than the drive via the B-switch36and the storage battery32. The C-switch50is further closed supplementally when electric power stored in the storage battery32is short regardless of presence or absence of the photovoltaic power generation.

In addition, as apparent fromFIG. 2(B), the D-switch54for selling DC electric power from the storage battery32to other home and the E-switch56for buying DC electric power from other home to charge the storage battery32are closed first during the midnight power rate time slot. This is because during the midnight power rate time slot, the storage batteries of individual homes are considered as one virtual large storage battery beyond fences among homes so that low-cost electric power storage can be performed together as much as possible and electric power interchange can be performed to a home having a free capacity. Note that the storage battery32may be charged not only from electric power of the midnight power rate but also from electric power of the photovoltaic power generation at high cost and electric power bought during the normal time slot. If such electric power charged at high cost is used for interchange with other home at a rate similarly to the midnight power rate, confusion may occur in accounting of the electric power interchange. Therefore, in this example, among electric power stored in the storage battery32, electric power charged at high cost is excluded, and only the electric power charged by buying power at the midnight power rate is interchanged with other home only if there is a surplus thereof.

InFIG. 2(B), according to the concept described above, switch control during time other than the midnight power rate time slot is performed. First, the D-switch54for buying DC electric power from the storage battery32to other home is closed only in a case where electric power charged in the storage battery32is sufficient and there is a margin of electric power bought at the midnight power rate, and is opened in other cases. On the other hand, the E-switch56for buying DC electric power from other home to charge the storage battery32is closed in a case where electric power charged in the storage battery32is short, and is opened in other cases.

FIG. 3is a schematic diagram of stored electric power illustrating sufficiency or shortage of electric power in the storage battery32, and the above-mentioned surplus of bought DC electric power.FIGS. 3(A) and 3(B)illustrate examples where the stored electricity in a capacity102of the storage battery32is constituted of only electric power104bought at the midnight power rate. Here, inFIG. 3(A), the electric power104bought at the midnight power rate includes the surplus exceeding a line106of electric power that can be consumed until the next midnight power rate time slot. In this case, it is not necessary to charge the storage battery32during time other than the midnight power rate time slot, and the surplus electric power can be sold to other home. In contrast, inFIG. 3(B), the stored electricity by the electric power104bought at the midnight power rate is below the line106of electric power that can be consumed until the next midnight power rate time slot. In this case, it is necessary to charge the storage battery32by the next midnight power rate time slot. Further, as a matter of course, there is no surplus that can be sold to other home.

In contrast,FIGS. 3(C) to 3(E)illustrate examples in which the stored electricity in the capacity102of the storage battery32is constituted of the electric power104bought at the midnight power rate and electric power108of high cost generation plus normal rate buy. Here, inFIG. 3(C), only the electric power104bought at the midnight power rate exceeds the line106of electric power that can be consumed until the next midnight power rate time slot, and the total stored electricity also exceeds the line106as a matter of course. Therefore, it is not necessary to charge the storage battery32during time other than the midnight power rate time slot. It should be noted that the surplus electric power that can be sold to other home is not all the electric power part exceeding the line106but a part after subtracting the electric power108of high cost generation plus normal rate buy from the same.

On the other hand, inFIG. 3(D), the electric power104bought at the midnight power rate is below the line106of electric power that can be consumed until the next midnight power rate time slot, and the total electric power after adding the electric power108of high cost generation plus normal rate buy to the same exceeds the line106. In this state, it is not necessary to charge the storage battery32during time other than the midnight power rate time slot, but there is no surplus electric power that can be sold to other home. InFIG. 3(E), the electric power104bought at the midnight power rate is below the line106of electric power that can be consumed until the next midnight power rate time slot, and the total electric power after adding the electric power108of high cost generation plus normal rate buy to the same is also below the line106. In this state, it is necessary to further charge the storage battery32with the high-cost power source during time other than the midnight power rate time slot. As a matter of course, there is no surplus electric power that can be sold to other home.

FIG. 4is a schematic diagram of charged electric power illustrating interchange of electric power bought at midnight power rate, in which a part having the same meaning as inFIG. 3is denoted by the same numeral. In addition,FIG. 4(A1) illustrates a structure of electric power charged in the storage battery32of the first home4, andFIG. 4(A2) illustrates a structure of electric power charged in the storage battery52of the second home6. Further,FIGS. 4(A1) and4(A2) illustrate a case without the interchange of the stored electric power. As apparent fromFIG. 4(A1), in the first home4, the stored electricity in the capacity102of the storage battery32is constituted of only the electric power104bought at the midnight power rate. Further, because the stored electricity exceeds the line106of electric power that can be consumed until the next midnight power rate time slot, it is not necessary to charge the storage battery32during time other than the midnight power rate time slot. On the other hand, the stored electricity in the storage battery52of the second home6is constituted of the electric power104bought at the midnight power rate and the electric power108of high cost generation plus normal rate buy. Further, the electric power104bought at the midnight power rate is below the line106of electric power that can be consumed until the next midnight power rate time slot, but the total electric power after adding the electric power108of high cost generation plus normal rate buy to the same exceeds the line106. Therefore, similarly to the first home4, it is not necessary to charge the storage battery32during time other than the midnight power rate time slot. However, the electric power that will be consumed by the next midnight power rate time slot in the second home6contains high-cost electric power so that the cost is increased.

In contrast,FIG. 4(B1) illustrates the structure of electric power charged in the storage battery32of the first home4, andFIG. 4(B2) illustrates the structure of electric power charged in the storage battery52of the second home6, in which the electric power interchange is performed. As apparent fromFIG. 4(B1), a sold electric power112out of the surplus electric power of the first home4is bought by the second home6as illustrated by an arrow114, so as to charge the storage battery52as a bought electric power116as illustrated inFIG. 4(B2). Thus, the structure of electric power in the storage battery52of the second home6inFIG. 4(B2) is constituted of the electric power104bought at the midnight power rate plus the bought electric power116from the first home4. Thus, each of them has a low-cost structure at substantially the midnight power rate. In this way, by interchanging electric power bought at the midnight power rate among a plurality of homes, low-cost electric power procurement can be realized as a whole.

FIG. 5is a basic flowchart illustrating switch control function of the control portion28ofFIG. 1according to the first example of the present invention. The flow starts when the system is installed. First in Step S2, the stored electricity that can be consumed in the own home by the next midnight power rate time slot and the surplus stored electricity that can be interchanged to other home by the next midnight power rate time slot are set. Details of the process will be described later. Next in Step S4, it is checked whether or not the present time is in the midnight power rate time slot. If it is not the midnight power rate time slot, the process goes to Step S6, and it is checked whether or not the stored electricity in the storage battery32is equal or larger than the electricity that can be consumed in the own home by the next midnight power rate time slot.

If it is decided in Step S6that there is the stored electricity that can be consumed by the next midnight power rate time slot, the process goes to Step S8in which the A-switch34for charging by the photovoltaic power generation is opened. Then, the process goes to Step S10, and the B-switch36for charging with the AC electric power from the single-phase three-wire commercial electric power14is opened. Further in Step S12, the C-switch50for directly consuming the AC electric power from the single-phase three-wire commercial electric power14is opened, and the process goes to Step S14. In this way, if the stored electricity in the storage battery32is equal or larger than the electricity that can be consumed in the own home by the next midnight power rate time slot, the electric power is consumed entirely from the electric power of the storage battery. This is applied not only to the DC electrical appliances42but also to the AC electrical appliances48. Therefore, if there is the photovoltaic power generation electric power, by opening the switch for buying power, all the generated power is sold so as to make twice profit.

On the other hand, if it is decided in Step S6that there is shortage of the stored electricity that can be consumed by the next midnight power rate time slot, the process goes to Step S16in which it is checked whether or not the photovoltaic power is being generated. Then, if the photovoltaic power is being generated, the process goes to Step S18in which the A-switch34for charging by photovoltaic power generation is closed. Further in Step S20, the B-switch36for charging with the AC electric power from the single-phase three-wire commercial electric power14is opened. Thus, the charging of the shortage is performed only by the photovoltaic power generation electric power during the photovoltaic power generation. Further in Step S22, the C-switch50for directly consuming the AC electric power from the single-phase three-wire commercial electric power14is closed, and the process goes to Step S14. The C-switch50is closed because it is economical for direct consuming to consume the AC electric power bought at the normal rate than consuming the electric power of the photovoltaic power generation that can be sold for twice price.

In addition, if it is checked in Step S4that the present time is in the midnight power rate time slot, the process goes to Step S24in which the A-switch34for charging with the photovoltaic power generation that is not currently performed is opened. Further in Step S26, the B-switch36for charging with the AC electric power from the single-phase three-wire commercial electric power14is closed to buy the AC electric power from the single-phase three-wire commercial electric power14at the midnight power rate so that the storage battery32can be charged. Then, the process goes to Step S22in which the C-switch50is closed so that the AC electric power from the single-phase three-wire commercial electric power14can be directly consumed at the midnight power rate, and the process goes to Step S14.

In Step S14, DC sell/buy process of the storage battery32with other home is performed, and the process goes to Step S28. Details of Step S14will be described later. In Step S28, presence or absence of maintenance operation of the system due to coming of the regular maintenance time or manual operation is checked. If there is no detection of either operation, the process goes back to Step S2. After that, as long as there is no maintenance detection is performed in Step S28, Steps S2to S28are repeated so that the switches are controlled in accordance with various situations.

FIG. 6is a flowchart illustrating details of the DC sell/buy process in Step S14ofFIG. 5. When the flow starts, it is checked in Step S32whether or not the present time is in the midnight power rate time slot. If it is not in the midnight power rate time slot, the process goes to Step S34, and it is checked whether or not the stored electricity in the storage battery32is equal or larger than the electricity that can be consumed in the own home by the next midnight power rate time slot. If the result is true, the process goes to Step S36because it is not necessary to buy power. Then, the E-switch56for buying DC power is opened, and the process goes to Step S38. In Step S38, it is checked whether or not there is surplus stored electricity by electric power bought at the midnight power rate that can be interchanged to other home by the next midnight power rate time slot. If there is no surplus, the process goes to Step S40in which the D-switch54for selling DC power is opened, and the flow is finished.

On the other hand, if it is checked in Step S34that the stored electricity in the storage battery32is smaller than the electricity that can be consumed in the own home by the next midnight power rate time slot, the process goes to Step S42in which the E-switch56for buying DC power is closed so that DC power can be bought from other home. Then, because there is no surplus power for selling as a matter of course, the process goes to Step S40in which the D-switch54for selling DC power is opened, and the flow is finished. Further, if it is checked in Step S32that the present time is in the midnight power rate time slot, the process goes to Step S44, in which the E-switch56for buying DC power is closed so that electric power can be bought from other home. In addition, in Step S46, the D-switch54for selling DC power is closed so that electric power can be sold to other home. In this way, during the midnight power rate time slot, DC electric power can be sold and bought freely. Note that if it is checked in Step S38that there is surplus stored electricity by power bought at the midnight power rate that can be interchanged to other home by the next midnight power rate time slot, the process goes to Step S46in which the D-switch54for selling DC power is closed, and the flow is finished. In this way, during time other than the midnight power rate time slot, electric power can be sold only if there is surplus charge electric power bought at the midnight power rate. Even if there is charge electric power that can be consumed by the next midnight power rate time slot, if there is no surplus after subtracting power charged by high-cost power, interchange to other home is not performed.

FIG. 7is a flowchart illustrating details of the process of setting the stored electricity that can be consumed in the own home by the next midnight power rate time slot and the surplus stored electricity that can be interchanged to other home by the next midnight power rate time slot in Step S2ofFIG. 5. When the flow starts, it is checked in Step S52whether or not the present time has reached 7:00 a.m. when the midnight power rate time slot is finished. The checking of Step S52is performed only for a short time period corresponding to a few periods of repetition of the flow ofFIG. 5after 7:00 a.m., and after the short time period it is not decided that the present time has reached 7:00 a.m. If it is detected in Step S52that the present time has reached 7:00 a.m., the process goes to Step S54in which electric power consumption/storage data of one day is reset, and storage is restarted. Then, the process goes to Step S56. On the other hand, if it is not detected in Step S52that the present time has reached 7:00 a.m., the process goes directly to Step S56.

In Step S56, it is checked whether or not the present time is in the midnight power rate time slot. If it is not in the midnight power rate time slot, it is checked Step S58whether or not the storage battery32is being discharged. This means to check whether or not the electric power stored in the storage battery32is being consumed. If it is not being discharged, the process goes to Step S60in which it is checked whether or not an instruction to close the C-switch50is valid. This means to check whether or not the AC electrical appliances48are being driven by directly consuming the electric power from the single-phase three-wire commercial electric power14. If the result is true, the process goes to Step S62in which total power consumption data is accumulated, and the process goes to Step S64. In addition, the process goes to Step S62also when discharge of the storage battery32is detected in Step S58.

In this way, when discharge of the storage battery32or direct power consumption of the single-phase three-wire commercial electric power14occurs, the power consumption data is accumulated in Step S62. Note that if either one causes transition to Step S62, the total power consumption data is accumulated in Step S62. Therefore, if both the discharge of the storage battery32and the direct power consumption of the single-phase three-wire commercial electric power14occur, power consumption data as a sum of them is accumulated. On the other hand, if it is detected in Step S56that the present time is in the midnight power rate time slot, or if it is not detected in Step S60that the instruction to close the C-switch50is valid, the process goes directly to Step S64because it is not necessary to accumulate the power consumption data.

In Step S64, it is checked whether or not the present time has reached 11:00 p.m. when the midnight power rate time slot starts. The checking in Step S64is also performed only for a short time period corresponding to a few periods of repetition of the flow ofFIG. 5after 11:00 p.m. similarly to Step S52, and after the short time period it is not decided that the present time has reached 11:00 p.m. If it is detected in Step S64that the present time has reached 11:00 p.m., the process goes to Step S66, in which accumulation of the electric power consumption/storage data of one day is finished. Then, the power consumption data from 7:00 a.m. to 11:00 p.m. as a record of the day is settled. In the next Step S68, stored electricity data that can be consumed by the midnight power rate time slot set at the present time is retrieved. Then, in Step S70, a weighted average of data at the present time retrieved in Step S68and the latest one day data settled in Step S68is calculated, and data of the electric power that can be consumed by the midnight power rate time slot is updated. Then, the process goes to Step S72. On the other hand, if it is not detected in Step S64that the present time has reached 11:00 p.m., the process goes directly to Step S72. In this way, the data of electric power that can be consumed by the midnight power rate time slot as an estimated value is corrected every day based on the record so that a separation from reality does not occur.

In Step S72, high-cost electric power in the storage battery32that cannot be interchanged between homes is calculated. The details of the calculation process will be described later. Next, in Step S74, the data of stored electricity that can be consumed by the next midnight power rate time slot is retrieved. This data is the latest data that is updated when Steps S66to S70are performed. Then, in Step S76, data of electricity that cannot be interchanged obtained in Step S72is subtracted from the data retrieved in Step S74. In the next Step S78, a result of subtraction in Step S76is updated as data of the surplus stored electricity that can be interchanged by the next midnight power rate time slot, and the flow is finished.

FIG. 8is a flowchart illustrating details of the calculation process of the electricity that cannot be interchanged in Step S72ofFIG. 7. When the flow starts, the data of electric power that cannot be interchanged in the storage battery32at the present time is retrieved in Step S82. Then, in Step S84, it is checked whether or not the present time is in the midnight power rate time slot. If it is not in the midnight power rate time slot, there is possibility that high-cost charging is performed. Therefore, the process goes to Step S86in which it is checked whether or not an instruction to close the B-switch36is valid. If the result is true, the process goes to Step S88in which the stored electricity in the storage battery32from the single-phase three-wire commercial electric power14via the B-switch36is added to data retrieved in Step S82as electricity that cannot be interchanged, and the process goes to Step S90. On the other hand, if the instruction to close the B-switch36is not valid in Step S86, the process goes directly to Step S90.

In Step S90, it is checked whether or not an instruction to close the A-switch34is valid. If the result is true, the process goes to Step S92in which the stored electricity in the storage battery32from the photovoltaic power generation electric power via the A-switch34is added to data retrieved in Step S82as electricity that cannot be interchanged, and the process goes to Step S94. On the other hand, if the instruction to close the A-switch34is not valid in Step S90, the process goes directly to Step S94. In addition, if the present time is not in the midnight power rate time slot in Step S84, the process also goes directly to Step S94.

In Step S94, it is checked whether or not the storage battery32is being discharged. If the result is true, the process goes to Step S96in which it is checked whether or not an instruction to close the D-switch54is valid. If the result is true, the process goes to Step S98in which data of discharged electricity for interchanging electric power to other home via the D-switch54is excluded from the interchange calculation, and the process goes to Step S100. It is because the interchange to other home is not consumption in the own home. On the other hand, if the instruction to close the D-switch54is not valid in Step S96, all the discharge of the storage battery32means consumption in the own home. Therefore, the process goes directly to Step S100. In Step S100, the discharged electricity, namely the power consumption in the own home is subtracted from data retrieved as electricity that cannot be interchanged in Step S82. This means that high-cost electric power that cannot be interchanged is consumed in the own home, and as a result the electric power that cannot be interchanged is reduced.

Next in Step S102, it is checked whether or not electricity that cannot be interchanged has become negative as a result of the subtraction in Step S100. If the electricity that cannot be interchanged has become negative, the process goes to Step S104in which data of the electricity that cannot be interchanged is set to zero, and the process goes to Step S106. It is because the electricity that cannot be interchanged is eliminated, and hence it is not reasonable to take further consumption of electric power into account of the electricity that cannot be interchanged. On the other hand, the electricity that cannot be interchanged has not become negative in Step S102, the process goes directly to Step S106so as to adopt the electricity that cannot be interchanged as it is, which is the result of the subtraction. Note that if it is not detected that the storage battery32is being discharged in Step S94, the electricity that cannot be interchanged is not reduced. Therefore, the process goes directly to Step106. In Step S106, the above-mentioned result is stored as updated data of the electricity that cannot be interchanged in the storage battery, and the flow is finished.

In the above-mentioned first example, there is described the example where two homes are dwelling in the condominium2. However, various features of the present invention described above are not limited to applications of a multiple dwelling house such as a condominium, but can be embodied similarly in a residential section where houses are arranged. In this case, the photovoltaic power generation panel for each home is installed on a roof of each house.

As described above, according to the first example, there is provided an electric power system including a first unit equipped with a first power source, a first rechargeable battery to which an output of the first power source is input, and a first power consuming portion to which an output of the first rechargeable battery is input; a second rechargeable battery; and an electric power line for sharing electric power between the first rechargeable battery and the second rechargeable battery. Further, in the case of the first example, the first power source (and a second power source) is the commercial electric power.

Here, the first example is based on a precondition that the selling power price of the photovoltaic power generation electric power is set higher and is based on a concept of not consuming the photovoltaic power generation electric power that can be sold at high price, and consuming electric power bought at low price from the commercial electric power as the midnight power rate electric power, so as to make a profit of the difference between them (there is a profit even if losses in AC/DC conversion is taken into account). Therefore, the first example adopts the concept of using the photovoltaic power generation electric power for selling as much as possible by DC/AC conversion while restricting interchanging the electric power or even consuming the same (interchange of electric power is performed using the midnight power rate electric power).

Second Example

Hereinafter, construction of a DC electric power network (storage battery distributed system) in a second example is described in detail.

FIG. 9is a schematic diagram illustrating an electric power supply system of a common multiple dwelling house.

Conventionally, when the photovoltaic power generation system is installed in a the multiple dwelling house100such as a condominium, the solar panel102and a power conditioner103are owned by each person (owned by each resident of a residential room101).

Therefore, in the second example described below, it is supposed that the solar panel and the power conditioner are owned by each person, and there is proposed a DC electric power network that can make a unique merit of being the multiple dwelling house. However, the above-mentioned “multiple dwelling house” is not limited to a condominium or an apartment, but can be an aggregate of houses, for example.

FIG. 10is a schematic diagram illustrating an embodiment of a DC electric power network (storage battery distributed system).

A plurality of units201included in the DC electric power network in this embodiment correspond to homes of individual persons (for example, residential rooms of a condominium or houses), each of which includes a unit control portion201a, a solar panel201b, and a unit storage battery201c. Note that if a small capacity of storage battery (like a car battery, for example) is used as the unit storage battery201c, it is easy to increase or decrease the DC electric power networks.

In addition, in the DC electric power network of this embodiment, a first class group205is formed to include the plurality of units201, a shared storage battery202, a first class shared electric power line203, and a first class group control portion204. Note that the plurality of units201share the shared storage battery202via the shared electric power line203under integral control by the group control portion204.

In addition, in the DC electric power network of this embodiment, a second class group209is formed to include the plurality of groups205, a first class shared storage battery206, a second class shared electric power line207, and a second class group control portion208. Note that the plurality of groups205share the shared storage battery206via the shared electric power line207under integral control by the group control portion208.

In addition, in the DC electric power network of this embodiment, a third class group213is formed to include the plurality of groups209, a second class shared storage battery210, a third class shared electric power line211, and a third class group control portion212. Note that the plurality of groups209share the shared storage battery210via the shared electric power line211under integral control by the group control portion212.

In addition, in the DC electric power network of this embodiment, the group formation similar to the above description is repeated, and an N-th class (class number N is arbitrary) group214is formed as a highest class group. Then, finally, a route220is formed to include the plurality of groups214, an N-th class shared storage battery215, a route class shared electric power line216, a route control portion217, an AC/DC converter218, and a DC/AC converter219. Note that the plurality of groups214share the shared storage battery215via the shared electric power line216under integral control by the route control portion217.

In addition, in the DC electric power network of this embodiment, buying and selling of AC electric power is performed between the route220and an electric power company221. Therefore, it is basically not allowed to directly perform the buying and selling of AC electric power between the electric power company221and the unit201or the group205,209,213, . . . , or214. However, even if stored electric power of the entire DC electric power network is absolutely short, electric power supply to electrical appliances owned by the unit201must be continued. Therefore, the DC electric power network of this embodiment has a structure in which a path for the unit201to directly buy AC electric power from the electric power company221is provided.

In this way, the DC electric power network of this embodiment is constructed based on the precondition that the solar panel201band the power conditioner (not shown) are owned by person, and hence a large-scale of infrastructure is not necessary.

In addition, the DC electric power network of this embodiment has a structure in which electrical storage capacities are interchanged between a unit and a group (between the unit storage battery201cand the shared storage battery202), or between groups (between the shared storage battery202and the shared storage battery206, between the shared storage battery206and the shared storage battery210, and the like), or between a group and the route (between a shared storage battery (not shown) belonging to the N-th class group214and the shared storage battery215), so that electrical storage capacity of the entire DC electric power network is regarded as large. In addition, the DC electric power network of this embodiment has a structure in which in order to avoid a state where any one of the storage batteries is fully charged as much as possible, the above-mentioned interchange of the electrical storage capacity between a unit and a group, or between groups, or between a group and the route (charge/discharge between storage batteries) is performed frequently. With this structure, the DC electric power obtained from the solar panel201bof the unit201can be used as the DC electric power as much as possible, and hence it is possible to reduce electric power losses due to the DC/AC conversion and the AC/DC conversion.

FIG. 11is a schematic diagram illustrating a structural example of the unit. A unit300of this structural example includes a unit control portion301, a unit storage battery302, an electric power monitoring portion303, a charge control portion304, an AC/DC converter305, a DC/AC converter306, an AC plug307, DC plugs308to310, a lighting fixture311, a personal computer312, a flat television set313, switches a1and a2for buying/charging electricity, and switches b1to b5for selling/discharging/consuming electricity. In addition, the group to which the unit300belongs includes a group control portion314, a shared storage battery315, and a shared electric power line316. In addition, on a path for the unit300to directly buy AC electric power from the electric power company317, there is disposed an electric power monitoring portion318. Note thatFIG. 11is a diagram in which components of the unit300are noted, and components outside the unit (components of the group to which the unit300belongs) are illustrated only partially.

The unit control portion301performs on/off control of the switches a1and a2(buying/charging electricity control) and on/off control of the switches b1to b5(selling/discharging/consuming electricity control). Note that when charge/discharge of the DC electric power is performed between the unit storage battery302and the shared storage battery315, the unit control portion301outputs a request to buy electricity or a request to sell electricity to the group control portion314, and checks an instruction to buy electricity or an instruction to sell electricity replied from the group control portion314.

As described above, the unit storage battery302is a small capacity storage battery (like a car battery, for example). Note that the unit storage battery302is charged by “DC power supplying from the power conditioner (not shown)” and “DC power buying from the shared storage battery315”. In addition, the unit storage battery302is discharged by “electric power consumption in the unit300” and “DC power selling to the shared storage battery315”.

The electric power monitoring portion303compares the generated electric power of DC power supplying from the solar panel (not shown) via the power conditioner (not shown) with the power consumption in the unit300(discharging electric power of the unit storage battery302), so as to perform electric power monitoring of the unit storage battery302. Specifically, if the generated electric power is larger than the power consumption, it is decided that the unit storage battery302is in a power surplus state (in which an electric power balance of the unit storage battery302is positive (surplus)). On the contrary, if the generated electric power is smaller than the power consumption, it is decided that the unit storage battery302is in a power shortage state (in which the electric power balance of the unit storage battery302is negative (short)).

The charge control portion304converts the DC electric power supplied from the power conditioner (not shown) or the shared electric power line316into a level suitable for charging the unit storage battery302. Note that the power conditioner (not shown) owned by the unit300needs not to perform the interconnection with the commercial AC electric power from the electric power company317. Therefore, it is possible to adopt a structure in which the DC electric power obtained by the solar panel (not shown) is not converted into AC electric power but is directly supplied to the charge control portion304. With this structure, when charging from the power conditioner (not shown) to the unit storage battery302, there occurs no electric power loss due to the DC/AC conversion process or the AC/DC conversion process.

The AC/DC converter305converts the AC electric power supplied from the electric power company317into the DC electric power, and supplies the DC electric power to the DC plugs308to310.

The DC/AC converter306converts the DC electric power discharged from the unit storage battery302into the AC electric power, and supplies the AC electric power to the AC plug307.

The AC plug307is a plug for drawing out the AC electric power into the residential room.

The DC plugs308to310are plugs for drawing out the DC electric power into the residential room.

As the lighting fixture311, there can be used a halogen lamp (AC load), a fluorescent lamp (AC load), an LED lighting fixture (DC load), and the like. Note thatFIG. 11illustrates a power supplying path for the AC electric power drawn out from the AC plug307to be supplied directly to the halogen lamp. In addition,FIG. 11illustrates a power supplying path for the DC electric power from the DC plug308to be supplied to the fluorescent lamp via the DC/AC converter and a power supplying path for the same to be supplied to the LED lighting fixture via the DC/DC converter. In this way, the halogen lamp and the fluorescent lamp as AC loads can be supplied with the AC electric power bought from the electric power company317or with the AC electric power generated by DC/AC conversion of the DC electric power discharged from the unit storage battery302. In addition, the LED lighting fixture as a DC load can be supplied with the DC electric power discharged from the unit storage battery302or the DC electric power generated by AC/DC conversion of the AC electric power bought from the electric power company317.

The personal computer312includes a CPU and an HDD (which are DC loads). Note thatFIG. 11illustrates a power supplying path for the DC electric power from the DC plug309to be led into the personal computer312and to be supplied to the CPU and the HDD via a DC/DC converter. With this structure, it is not necessary to dispose an AC/DC converter in the personal computer312, so that the device can be downsized, and cost thereof can be reduced. In addition, an electric power loss due to the AC/DC conversion process can be eliminated.

The flat television set313includes a liquid crystal panel and a backlight (which are DC loads). Note thatFIG. 11illustrates a power supplying path for the DC electric power from the DC plug310to be led into the flat television set313and to be supplied to the liquid crystal panel and the backlight via a DC/DC converter. With this structure, it is not necessary to dispose an AC/DC converter in the flat television set313, so that the device can be downsized, and cost thereof can be reduced. In addition, an electric power loss due to the AC/DC conversion process can be eliminated.

The switch a1is controlled to be turned on and off by the unit control portion301so as to make and break a connection between the AC/DC converter305and the DC plugs308to310. The switch a2is controlled to be turned on and off by the unit control portion301so as to make and break a connection of the charging path from the shared electric power line316to the unit storage battery302(DC power buying path).

The switch b1is controlled to be turned on and off by the unit control portion301so as to make and break a connection of the AC power supplying path from the electric power company317to the AC plug307. The switch b2is controlled to be turned on and off by the unit control portion301so as to make and break a connection between the DC/AC converter306and the AC plug307. The switch b3is controlled to be turned on and off by the unit control portion301so as to make and break a connection between the AC/DC converter305and the DC plugs308to310. The switch b4is controlled to be turned on and off by the unit control portion301so as to make and break a connection between the unit storage battery302and the DC plugs308to310. The switch b5is controlled to be turned on and off by the unit control portion301so as to make and break a connection of the discharging path from the unit storage battery302to the shared electric power line316(DC power selling path).

When the group control portion314performs charge/discharge of the DC electric power between the unit storage battery302and the shared storage battery315, it receives the request to buy electricity or the request to sell electricity from the group control portion314, and outputs the instruction to buy electricity or the instruction to sell electricity as a reply to the unit control portion301.

The shared storage battery315is connected to the shared electric power line316and performs charge/discharge of the DC electric power with the unit storage battery302.

The shared electric power line316is a path for performing charge/discharge of the DC electric power between the unit storage battery302and the shared storage battery315.

The electric power company317supplies the AC electric power to the unit300.

The electric power monitoring portion318is an electric power meter that accumulates AC electric power amount supplied from the electric power company317to the unit300for a predetermined period (for example, one month), so as to obtain billing information to the unit300.

FIG. 12is an operation list of the unit control portion301, which shows, in order from the left, numbers assigned to operation states, a result of monitoring electric power by the electric power monitoring portion303, presence or absence of the request to buy electricity or the request to sell electricity output from the unit control portion301, content of the instruction to buy electricity or the instruction to sell electricity of the group control portion314, on/off states of the switches a1and a2for buying/charging electricity, on/off states of the switches b1to b5for selling/discharging/consuming electricity, and features (merits and demerits) of the operation states.

A first operation state is a state in which the electric power balance of the unit storage battery302is positive (surplus), and the shared storage battery315can accept the surplus electric power of the unit300. As a supposed situation, there is a case where power consumption of the unit300is small during daytime (fine weather) and the shared storage battery315has vacant capacity, or a case where the power consumption of the unit300is zero, and the shared storage battery315has vacant capacity.

In the first operation state, the electric power monitoring portion303decides that the unit storage battery302is in the power surplus state. When the unit control portion301receives this decision result, it outputs to the group control portion314the request to sell electricity (request for DC power selling of the surplus electric power of the unit300to the group side). When the group control portion314receives this request to sell electricity, it outputs the instruction to sell electricity to the unit control portion301so as to allow (validate) the DC power selling of the unit300(which is shown by “∘” in the diagram).

Note that in the first operation state, the unit control portion301does not output to the group control portion314the request to buy electricity (request for compensating for short electric power of the unit300by the DC power buying from the group side). Therefore, the group control portion314outputs to the unit control portion301the instruction to buy electricity that means not to allow (invalidate) the DC power buying of the unit300(which is shown by “x” in the diagram).

In this first operation state, the unit control portion301turns off the switches a1and a2as well as the switches b1and b3, and turns on the switches b2, b4, and b5. With this switch control, electric power supply from the unit storage battery302to unit loads311to313is performed, and DC power selling from the unit storage battery302to the shared storage battery315is performed.

Therefore, in the first operation state, only the DC electric power obtained by the photovoltaic power generation is sufficient for all the power consumption of the unit300. In addition, the surplus electric power of the unit300can be sold to the group side by the DC power selling so as to earn the income of the value.

A second operation state is a state in which the electric power balance of the unit storage battery302is positive (surplus), but the shared storage battery315cannot accept the surplus electric power of the unit300. As a supposed situation, there is a case where power consumption of the unit300is small during daytime (fine weather) and the shared storage battery315is fully charged, or a case where power consumption of the unit300is zero, and the shared storage battery315is fully charged.

In the second operation state, the request to sell electricity is output from the unit control portion301to the group control portion314similarly to the first operation state described above. However, in the second operation state, the shared storage battery315cannot accept the surplus electric power of the unit300. Therefore, when the group control portion314receives the above-mentioned request to sell electricity, it outputs to the unit control portion301the instruction to sell electricity that means not to allow (invalidate) the DC power selling of the unit300(which is shown by “x” in the diagram). Note that similarly to the above-mentioned first operation state, the unit control portion301does not output the request to buy electricity to the group control portion314in the second operation state, too. Therefore, the group control portion314outputs to the unit control portion301the instruction to buy electricity that means not to allow (invalidate) the DC power buying of the unit300(which is shown by “x” in the diagram).

In this second operation state, the unit control portion301turns off the switches a1and a2as well as switches b1, b3, and b5, and turns on the switches b2and b4. In other words, in the second operation state, unlike the above-mentioned first operation state, the switch b5is turned off. With this switch control, the electric power supply from the unit storage battery302to the unit loads311to313is performed, but the DC power selling from the unit storage battery302to the shared storage battery315is stopped.

Therefore, in the second operation state, the surplus electric power of the unit300cannot be sold to the group side by the DC power selling, but the DC electric power obtained by the photovoltaic power generation is sufficient for all the power consumption in the unit300.

A third operation state is a state in which the electric power balance of the unit storage battery302is negative (short), but the short electric power of the unit300can be compensated from the shared storage battery315. As a supposed situation, there is a case where it is during daytime (cloudy or rainy) or during night, and the shared storage battery315has surplus electric power, or a case where power consumption of the unit300is large, and the shared storage battery315has surplus electric power.

In the third operation state, the electric power monitoring portion303decides that the unit storage battery302is in the power shortage state. When the unit control portion301receives this decision result, it outputs the request to buy electricity to the group control portion314. When the group control portion314receives this request to buy electricity, it outputs to the unit control portion301the instruction to buy electricity that means to allow (validate) the DC power buying of the unit300(which is shown by “∘” in the diagram).

Note that in the third operation state, the unit control portion301does not output to the group control portion314the request to sell electricity. Therefore, the group control portion314outputs to the unit control portion301the instruction to sell electricity that means not to allow (invalidate) the DC power selling of the unit300(which is shown by “x” in the diagram).

In this third operation state, the unit control portion301turns off the switch a1as well as the switches b1, b3, and b5, and turns on the switch a2as well as the switches b2and b4. With this switch control, electric power supply from the unit storage battery302to the unit loads311to313is performed, and DC power buying from the shared storage battery315to the unit storage battery302is performed.

Therefore, in the third operation state, the short electric power of the unit storage battery302can be compensated not by the AC power buying from the electric power company317but by the DC power buying from the shared storage battery315at lower cost. Therefore, the shared DC electric power in the group can be effectively used. However, unlike the above-mentioned first and second operation states, it should be noted that there is an expense for the DC power buying from the shared storage battery315in the third operation state.

A fourth operation state is a state in which the electric power balance of the unit storage battery302is negative (short), and the short electric power of the unit300cannot be compensated from the shared storage battery315. As a supposed situation, there is a case where it is during daytime (cloudy or rainy) or during night, and the shared storage battery315has no surplus electric power, or a case where the power consumption of the unit300is large, and the shared storage battery315has no surplus electric power.

In the fourth operation state, the request to sell electricity is output from the unit control portion301to the group control portion314similarly to the above-mentioned third operation state. However, in the fourth operation state, the short electric power of the unit300cannot be compensated from the shared storage battery315. Therefore, when receiving the request to buy electricity, the group control portion314outputs to the unit control portion301the instruction to buy electricity that means not to allow (invalidate) the DC power buying of the unit300(which is shown by “x” in the diagram). Note that similarly to the above-mentioned third operation state, the unit control portion301does not output the request to buy electricity to the group control portion314in the fourth operation state, too. Therefore, the group control portion314outputs to the unit control portion301the instruction to sell electricity that means not to allow (invalidate) the DC power selling of the unit300(which is shown by “x” in the diagram).

In this fourth operation state, the unit control portion301turns off the switch a2as well as switches b2, b4, and b5, switch a1, and turns on the switches b1and b3. With this switch control, the electric power supply to the unit loads311to313is performed by the AC power buying from the electric power company317.

Therefore, in the fourth operation state, even if both the unit storage battery302and the shared storage battery315become the power shortage state, a minimum electric power necessary for operating the unit loads311to313can be secured by performing the AC power buying from the electric power company317. However, in the fourth operation state, it should be noted that there is an expense for AC power buying from the electric power company317, and there is an electric power loss due to the AC/DC conversion process.

FIG. 13is an operation flowchart of the unit control portion301.

In Step S201, it is checked whether or not the power consumption of the unit300is equal or smaller than the generated electric power. Here, if it is decided that the power consumption is equal or smaller than the generated electric power, the flow goes to Step S202regarding that the unit storage battery302is in the power surplus state. On the other hand, if it is decided that the power consumption is not equal or smaller than the generated electric power, the flow goes to Step S206regarding that the unit storage battery302is in the power shortage state.

If it is decided in Step S201that the power consumption is equal or smaller than the generated electric power, the switches a1and a2as well as the switches b1to b5are appropriately controlled to be turned on and off in Step S202so that the electric power supply to the unit loads311to313is performed from the unit storage battery302. In addition, a flag of the request to sell electricity that means to sell the surplus electric power of the unit300to the group side by the DC power selling is output to the group control portion314.

After that, in Step S203, the instruction to sell electricity replied from the group control portion314is checked. Here, if the instruction to sell electricity that means to allow the DC power selling of the unit300is confirmed, the flow goes to Step S204. On the other hand, if the instruction to sell electricity that means not to allow the DC power selling of the unit300is confirmed, the flow goes to Step S205.

If the instruction to sell electricity that means to allow the DC power selling of the unit300is confirmed in Step S203, the switch b5is turned on in Step S204so as to perform the DC power selling to the shared storage battery315. This state corresponds to the above-mentioned first operation state. After that, the flow goes back to Step S201.

On the other hand, if the instruction to sell electricity that means not to allow the DC power selling of the unit300is confirmed in Step S203, the switch b5is turned off in Step S205so as to stop the DC power selling to the shared storage battery315. This state corresponds to the above-mentioned second operation state. After that, the flow goes back to Step S201.

In addition, if it is decided in Step S201that the power consumption is not equal or smaller than the generated electric power, a flag of the request to buy electricity that means to compensate for the short electric power of the unit300by the DC power buying from the group side is output to the group control portion314in Step S206.

After that, in Step S207, the instruction to buy electricity replied from the group control portion314is checked. Here, if the instruction to buy electricity that means to allow the DC power buying of the unit300is confirmed, the flow goes to Step S208. On the other hand, if the instruction to buy electricity that means not to allow the DC power buying of the unit300is confirmed, the flow goes to Step S209.

In Step S207, if the instruction to buy electricity that means to allow the DC power buying of the unit300is confirmed, the switch a2is turned on so as to perform the DC power buying from the shared storage battery315in Step S208. This state corresponds to the above-mentioned third operation state. Note that the electric power supply to the unit loads311to313is performed from the shared storage battery315via the unit storage battery302in the third operation state. After that, the flow goes back to Step S201.

On the other hand, in Step S207, if the instruction to buy electricity that means not to allow the DC power buying of the unit300is confirmed, the switches a1and b3are turned on so as to perform the AC power buying from the electric power company317in Step S209. This state corresponds to the above-mentioned fourth operation state. Note that the electric power supply to the unit loads311to313is performed from the electric power company317in the fourth operation state. After that, the flow goes back to Step S201.

FIG. 14is a schematic diagram illustrating a structural example of a group. A group400of this structural example is a lowest class (first class) group to which the plurality of units300belong. The group400includes a group control portion401, a shared storage battery402, an electric power monitoring portion403, a charge control portion404, a discharge control portion405, a shared electric power line406, an electric power monitoring portion407, a discharge control portion408, switches c1and c2for charging, and switches d1and d2for discharging. In addition, the upper class (second class) group to which the group400belongs includes a group control portion409, a shared storage battery410, a discharge control portion411, and a shared electric power line412. Note thatFIG. 14is a diagram in which components of the group400are noted, and components outside the group (the unit300and components of the higher group) are illustrated only partially. In addition, inFIG. 14, the lowest class group is exemplified for description, but the upper class group has the same basic structure.

When the group control portion401performs charge/discharge of the DC electric power between the shared storage battery402of its own group and the shared storage battery410of the higher group, it outputs a request to charge or a request to discharge to the upper class group control portion409, and checks an instruction to charge or an instruction to discharge replied from the group control portion409.

In addition, when the group control portion401performs charge/discharge of the DC electric power between the shared storage battery402of its own group and the unit storage battery302of the unit300, it receives the request to buy electricity or the request to sell electricity from the unit control portion301, and outputs the instruction to buy electricity or the instruction to sell electricity as reply to the unit control portion301.

Note that the group control portion401includes a higher group interface portion401a, a charge/discharge control portion401b, a lower unit/group electric power monitoring portion401c, and a lower unit/group controller401d. The higher group interface portion401aperforms intercommunication with the upper class group control portion409. The charge/discharge control portion401bperforms on/off control of the switches c1and c2and on/off control of the switches d1and d2. The lower unit/group electric power monitoring portion401cintegrally manages billing information of each of the plurality of units300(balance of buying and selling the DC electric power). The lower unit/group controller401dperforms intercommunication with the unit control portion301.

The shared storage battery402is connected to the shared electric power lines406and412, so as to perform charge/discharge of the DC electric power with the unit storage battery302or with the shared storage battery410of the higher group. In other words, the shared storage battery402of the group400is charged by “DC power charging from the unit storage battery302(or the shared storage battery of the lower group)” and “DC power charging from the shared storage battery410of the higher group”. In addition, the shared storage battery402of the group400is discharged by “DC power discharging to the unit storage battery302(or the shared storage battery of the lower group)” and “DC power discharging to the shared storage battery410of the higher group”.

The electric power monitoring portion403compares charging electric power with the discharging electric power of the shared storage battery402so as to perform the electric power monitoring of the shared storage battery402. Specifically, if the charging electric power is larger than the discharging electric power, it is decided that the shared storage battery402is in the power surplus state (in which the electric power balance of the shared storage battery402is positive (surplus)). On the contrary, if the charging electric power is smaller than the discharging electric power, it is decided that the shared storage battery402is in the power shortage state (in which the electric power balance of the shared storage battery402is negative (short)). In addition, the electric power monitoring portion403also performs full charge decision of the shared storage battery402.

The charge control portion404converts a DC electric power supplied from the shared electric power line406or412into a level suitable for charging the shared storage battery402.

The discharge control portion405converts a DC electric power discharged from the shared storage battery402into a level suitable for supplying to the shared electric power line406.

The shared electric power line406is a path for charging and discharging the DC electric power between the unit storage battery302and the shared storage battery402.

The electric power monitoring portion407is an electric power meter that accumulates DC electric power amount traded between the unit300and the shared electric power line406for a predetermined period (for example, one month), so as to obtain billing information (trade balance of the DC electric power) with respect to the unit300.

The discharge control portion408converts the DC electric power discharged from the unit storage battery302into a level suitable for supplying to the shared electric power line406.

The switch c1is controlled to be turned on and off by the group control portion401so as to make and break a connection of the charging path from the shared electric power line412to the shared storage battery402. The switch c2is controlled to be turned on and off by the group control portion401so as to make and break a connection of the charging path from the shared electric power line406to the shared storage battery402.

The switch d1is controlled to be turned on and off by the group control portion401so as to make and break a connection of the discharging path from the shared storage battery402to the shared electric power line412. The switch d2is controlled to be turned on and off by the group control portion401so as to make and break a connection of the discharging path from the shared storage battery402to the shared electric power line406.

When the group control portion409performs charge/discharge of the DC electric power between the shared storage battery402and the shared storage battery410, it receives the request to charge or the request to discharge from the group control portion401, and outputs the instruction to charge or the instruction to discharge as reply to the group control portion401.

The shared storage battery410is connected to the shared electric power line412and performs charge/discharge of the DC electric power with the shared storage battery402.

The discharge control portion411converts the DC electric power discharged from the shared storage battery402into a level suitable for supplying the shared electric power line412.

The shared electric power line412is a path for charging and discharging the DC electric power between the shared storage battery402and the shared storage battery410.

FIG. 15is an operation list of the group control portion401with respect to the higher group, which shows, in order from the left, numbers assigned to operation states, a result of monitoring electric power by the electric power monitoring portion403, presence or absence of the request to charge or the request to discharge output from the group control portion401, a content of the instruction to charge or the instruction to discharge output from the group control portion409, on/off states of the switches c1and c2for charging, and on/off states of the switches d1and d2for discharging.

The first operation state is a state in which the electric power balance of the shared storage battery402of its own group is positive (surplus), and the shared storage battery410of the higher group can accept the surplus electric power of its own group400.

In the first operation state, the electric power monitoring portion403decides that the shared storage battery402is in the power surplus state. When receiving this decision result, the group control portion401outputs to the upper group control portion409the request to discharge (request for the DC power discharging of the surplus electric power of the group400to the higher group side). When receiving this request to discharge, the upper group control portion409outputs to the group control portion401the instruction to discharge that means to allow (validate) the DC power discharging of the group400(which is shown by “∘” in the diagram).

Note that in the first operation state, the group control portion401does not output to the upper group control portion409the request to charge (request for compensating for short electric power of the group400by the DC power charging from the higher group side). Therefore, the upper group control portion409outputs to the group control portion401the instruction to charge that means not to allow (invalidate) the DC power charging of the group400(which is shown by “x” in the diagram).

In this first operation state, the group control portion401turns off the switch c1and turns on the switch d1. With this switch control, the DC power discharging from the shared storage battery402of its own group to the shared storage battery410of the higher group is performed.

The second operation state is a state in which the electric power balance of the shared storage battery402of its own group is positive (surplus), and the shared storage battery410of the higher group cannot accept the surplus electric power of its own group400.

In the second operation state, the request to discharge is output from the group control portion401to the upper group control portion409similarly to the above-mentioned first operation state. However, in the second operation state, the shared storage battery410of the higher group cannot accept the surplus electric power of its own group400. Therefore, when receiving the above-mentioned request to discharge, the upper group control portion409outputs to the group control portion401the instruction to discharge meaning not to allow (invalidate) the DC power discharging of its own group400(which is shown by “x” in the diagram). Note that similarly to the above-mentioned first operation state, in the second operation state too, the group control portion401never outputs the request to charge to the upper group control portion409. Therefore, the upper group control portion409outputs to the group control portion401the instruction to charge that means not to allow (invalidate) the DC power charging of the group400(which is shown by “x” in the diagram).

In this second operation state, the group control portion401turns off the switches c1and d1. In other words, in the second operation state, unlike the above-mentioned first operation state, the switch d1is turned off. With this switch control, the DC power discharging from the shared storage battery402of its own group to the shared storage battery410of the higher group is stopped.

The third operation state is a state in which the electric power balance of the shared storage battery402of its own group is negative (short), the short electric power of its own group400can be compensated from the shared storage battery410of the higher group.

In the third operation state, the electric power monitoring portion403decides that the shared storage battery402is in the power shortage state. Receiving this decision result, the group control portion401outputs to the upper group control portion409the request to charge. Receiving this request to charge, the upper group control portion409outputs to the group control portion401the instruction to charge that means to allow (validate) the DC power charging of the group400(which is shown by “∘” in the diagram).

Note that in the third operation state, the group control portion401never outputs to the upper group control portion409the request to discharge. Therefore, the upper group control portion409outputs to the group control portion401the instruction to discharge that means not to allow (invalidate) the DC power discharging of the group400(which is shown by “x” in the diagram).

In this third operation state, the group control portion401turns on the switch c1and turns off the switch d1. With this switch control, the DC power charging from the shared storage battery410of the higher group to the shared storage battery402of its own group400is performed.

The fourth operation state is a state in which the electric power balance of the shared storage battery402of its own group is negative (short), and the shared storage battery410of the higher group cannot compensate for the short electric power of its own group400.

In the fourth operation state, the group control portion401outputs to the upper group control portion409the request to charge, similarly to the above-mentioned third operation state. However, in the fourth operation state, the shared storage battery410of the higher group cannot compensate for the short electric power of its own group400. Therefore, when receiving the above-mentioned request to charge, the upper group control portion409outputs to the group control portion401the instruction to charge that means not to allow (invalidate) the DC power charging of the group400(which is shown by “x” in the diagram). Note that similarly to the above-mentioned third operation state, in the fourth operation state too, the group control portion401never outputs to the upper group control portion409the request to discharge. Therefore, the upper group control portion409outputs to the group control portion401the instruction to discharge that means not to allow (invalidate) the DC power discharging of the group400(which is shown by “x” in the diagram).

In this fourth operation state, the group control portion401turns off the switches c1and c2. In other words, in the fourth operation state, unlike the above-mentioned third operation state, the switch c1is turned off. With this switch control, the DC power charging from the shared storage battery410of the higher group to the shared storage battery402of its own group is stopped.

FIG. 16is an operation flowchart of the group control portion401with respect to the higher group.

In Step S301, it is checked whether or not the discharging electric power is equal or lower than the charging electric power in the shared storage battery402. Here, if it is decided that the discharging electric power is equal or lower than the charging electric power, it is regarded that the shared storage battery402is in the power surplus state, and the flow goes to Step S302. On the other hand, if it is decided that the discharging electric power is not equal or lower than charging electric power, it is regarded that the shared storage battery402is in the power shortage state, and the flow goes to Step S306.

If it is decided in Step S301that the discharging electric power is equal or lower than the charging electric power, in Step S302, the request to discharge flag that means to perform the DC power discharging of the surplus electric power of its own group400to the higher group side is output to the upper group control portion409.

After that, in Step S303, a content of the instruction to discharge replied from the upper group control portion409is checked. Here, if the instruction to discharge that means to allow the DC power discharging of its own group400is confirmed, the flow goes to Step S304. On the other hand, if the instruction to discharge that means not to allow the DC power discharging of its own group400is confirmed, the flow goes to Step S305.

In Step S303, if the instruction to discharge that means to allow the DC power discharging of its own group400is confirmed, the switch d1is turned on in Step S304so that the DC power discharging to the shared storage battery410of the higher group is performed. This state corresponds to the above-mentioned first operation state. After that, the flow goes back to Step S301.

On the other hand, if the instruction to discharge that means not to allow the DC power discharging of its own group400is confirmed in Step S303, the switch d1is turned off in Step S305in order to stop the DC power discharging of the shared storage battery410of the higher group. This state corresponds to the above-mentioned second operation state. After that, the flow goes back to Step S301.

In addition, if it is decided in Step S301that the discharging electric power is not equal or lower than the charging electric power, the request to charge flag that means to compensate for the short electric power of its own group400with the DC power charging from the higher group side is output to the upper group control portion409in Step S306.

After that, in Step S307, a content of the instruction to charge replied from the upper group control portion409is checked. Here, if the instruction to charge that means to allow the DC power charging of its own group400is confirmed, the flow goes to Step S308. On the other hand, if the instruction to charge that means not to allow the DC power charging of its own group400is confirmed, the flow goes to Step S309.

In Step S307, if the instruction to charge that means to allow the DC power charging of its own group400is confirmed, the switch c1is turned on in Step S308so as to perform the DC power charging from the shared storage battery410of the higher group. This state corresponds to the above-mentioned third operation state. After that, the flow goes back to Step S301.

On the other hand, in Step S307, if the instruction to charge that means not to allow the DC power charging of its own group400is confirmed, the switch c1is turned off in Step S309so as to stop the DC power charging from the shared storage battery410of the higher group. This state corresponds to the above-mentioned fourth operation state. After that, the flow goes back to Step S301.

FIG. 17is an operation list of the group control portion401with respect to the lower group (lower unit300), which shows, in order from the left, numbers assigned to operation states, a result of monitoring electric power by the electric power monitoring portion403, presence or absence of the request to charge or the request to discharge (the request to buy electricity or the request to sell electricity) output from the lower group control portion (unit control portion300), a content of the instruction to charge or the instruction to discharge (the instruction to buy electricity or the instruction to sell electricity) output from the group control portion401, on/off states of the switches c1and c2for charging, and on/off states of the switches d1and d2for discharging.

The first operation state is a state in which the electric power balance of the shared storage battery402is positive (surplus) but is not fully charged, and the requests to discharge are output from the plurality of units control portions301connected to the lower group. In this case, the group control portion401outputs to all the unit control portions301the instruction to discharge that means to allow (validate) the DC power discharging of the unit300(which is shown by “∘” in the diagram).

Note that in the first operation state, no unit control portion301outputs the request to charge. Therefore, the group control portion401outputs to all the unit control portions301the instruction to charge that means not to allow (invalidate) the DC power discharging of the unit300(which is shown by “x” in the diagram).

In this first operation state, the group control portion401turns on the switch c2and turns off the switch d2. With this switch control, the shared storage battery402is charged by the DC electric power discharged from the unit storage battery302.

The second operation state is a state in which the electric power balance of the shared storage battery402is positive (surplus) but is not fully charged, and the requests to charge are output from the plurality of units control portions301connected to the lower group. In this case, the group control portion401outputs to all the unit control portions301the instruction to charge that means to allow (validate) the DC power discharging of the unit300(which is shown by “∘” in the diagram).

Note that in the second operation state, no unit control portion301outputs the request to discharge. Therefore, the group control portion401outputs to all the unit control portions301the instruction to discharge that means not to allow (invalidate) the DC power discharging of the unit300(which is shown by “x” in the diagram).

In this second operation state, the group control portion401turns off the switch c2and turns on the switch d2. With this switch control, the unit storage battery302is charged by the DC electric power discharged from the shared storage battery402.

The third operation state is a state in which the electric power balance of the shared storage battery402is positive (surplus) but is not fully charged, and a part of the plurality of units control portions301connected to the lower group output the requests to discharge while the other part of the same output the requests to charge. In this case, the group control portion401outputs to the unit control portions301that have output the requests to discharge the instruction to discharge that means to allow (validate) the DC power discharging of the unit300(which is shown by “∘” in the diagram). In addition, the group control portion401outputs to the unit control portions301that have output the requests to charge the instruction to charge that means to allow (validate) the DC power discharging of the unit300(which is shown by “∘” in the diagram).

In this third operation state, the group control portion401turns on the switches c2and d2. With this switch control, between the shared storage battery402and the unit storage battery302in the power surplus state, the shared storage battery402is charged by the DC electric power discharged from the unit storage battery302. In addition, between the shared storage battery402and the unit storage battery302in the power shortage state, the unit storage battery302is charged by the DC electric power discharged from the shared storage battery402.

The fourth operation state is a state in which the shared storage battery402is fully charged, and all the plurality of units control portions301connected to the lower group output the requests to discharge. In this case, the group control portion401outputs to all the unit control portions301the instruction to discharge that means not to allow (invalidate) the DC power discharging of the unit300(which is shown by “x” in the diagram).

Note that in the fourth operation state, no unit control portion301outputs the request to charge. Therefore, the group control portion401outputs to all the unit control portions301the instruction to charge that means not to allow (invalidate) the DC power discharging of the unit300(which is shown by “x” in the diagram).

In this fourth operation state, the group control portion401turns off the switches c2and d2. With this switch control, the DC power discharging of the unit storage battery302is stopped.

A fifth operation state is a state in which the shared storage battery402is fully charged, and all the plurality of units control portions301connected to the lower group output the requests to charge. In this case, the group control portion401outputs to all the unit control portions301the instruction to charge that means to allow (validate) the DC power discharging of the unit300(which is shown by “∘” in the diagram).

Note that in the fifth operation state, no unit control portion301outputs the request to discharge. Therefore, the group control portion401outputs to all the unit control portions301the instruction to discharge that means not to allow (invalidate) the DC power discharging of the unit300(which is shown by “x” in the diagram).

In this fifth operation state, the group control portion401turns off the switch c2and turns on the switch d2. With this switch control, the unit storage battery302is charged by the DC electric power discharged from the shared storage battery402.

A sixth operation state is a state in which the shared storage battery402is fully charged, and a part of the plurality of units control portions301connected to the lower group output the requests to discharge, and the other part of the same output the requests to charge. In this case, the group control portion401outputs to the unit control portions301that have output the requests to discharge the instruction to discharge that means not to allow (invalidate) the DC power discharging of the unit300(which is shown by “x” in the diagram). In addition, the group control portion401outputs to the unit control portions301that have output the requests to charge the instruction to charge that means to allow (validate) the DC power discharging of the unit300(which is shown by “∘” in the diagram).

In this sixth operation state, the group control portion401turns off the switch c2and turns on the switch d2. With this switch control, between the shared storage battery402and the unit storage battery302in the power surplus state, the DC power discharging of the unit storage battery302is stopped. In addition, between the shared storage battery402and the unit storage battery302in the power shortage state, the unit storage battery302is charged by the DC electric power discharged from the shared storage battery402.

A seventh operation state is a state in which the electric power balance of the shared storage battery402is negative (short) and is not fully charged, and all the plurality of units control portions301connected to the lower group output the request to discharge. In this case, the group control portion401outputs to all the unit control portions301the instruction to discharge that means to allow (validate) the DC power discharging of the unit300(which is shown by “∘” in the diagram).

Note that in the seventh operation state, no unit control portion301outputs the request to charge. Therefore, the group control portion401outputs to all the unit control portions301the instruction to charge that means not to allow (invalidate) the DC power discharging of the unit300(which is shown by “x” in the diagram).

In this seventh operation state, the group control portion401turns on the switch c2and turns off the switch d2. With this switch control, the shared storage battery402is charged by the DC electric power discharged from the unit storage battery302.

An eighth operation state is a state in which the electric power balance of the shared storage battery402is negative (short) and is not fully charged, and all the plurality of units control portions301connected to the lower group output the requests to charge. In this case, the group control portion401outputs to all the unit control portions301the instruction to charge that means not to allow (invalidate) the DC power discharging of the unit300(which is shown by “x” in the diagram).

Note that in the eighth operation state, no unit control portion301outputs the request to discharge. Therefore, the group control portion401outputs to all the unit control portions301the instruction to discharge that means not to allow (invalidate) the DC power discharging of the unit300(which is shown by “x” in the diagram).

In this eighth operation state, the group control portion401turns off the switches c2and d2. With this switch control, the DC power charging of the unit storage battery302is stopped.

A ninth operation state is a state in which the electric power balance of the shared storage battery402is negative (surplus) and is not fully charged, and a part of the plurality of units control portions301connected to the lower group output requests to discharge while the other part of the same output the requests to charge. In this case, the group control portion401outputs to the unit control portions301that have output the requests to discharge the instruction to discharge that means to allow (validate) the DC power discharging of the unit300(which is shown by “∘” in the diagram). In addition, the group control portion401outputs to the unit control portions301that have output the requests to charge the instruction to charge that means not to allow (invalidate) the DC power discharging of the unit300(which is shown by “x” in the diagram).

In this ninth operation state, the group control portion401turns on the switch c2and turns off the switch d2. With this switch control, between the shared storage battery402and the unit storage battery302in the power surplus state, the shared storage battery402is charged by the DC electric power discharged from the unit storage battery302. In addition, between the shared storage battery402and the unit storage battery302in the power shortage state, the DC power charging of the unit storage battery302is stopped.

FIG. 18is an operation flowchart of the group control portion401with respect to the lower group (lower unit).

In Step S401, it is checked whether or not the discharging electric power is equal or lower than the charging electric power in the shared storage battery402. Here, if it is decided that the discharging electric power is equal or lower than the charging electric power, it is regarded that the shared storage battery402is in the power surplus state, and the flow goes to Step S402. On the other hand, if it is decided that the discharging electric power is not equal or lower than the charging electric power, it is regarded that the shared storage battery402is in the power shortage state, and the flow goes to Step S410.

If it is decided in Step S401that the discharging electric power is equal or lower than the charging electric power, it is checked in Step S402whether or not the shared storage battery402is fully charged. Here, if it is decided that the shared storage battery402is not fully charged, it is regarded that the shared storage battery402has a vacant capacity, and the flow goes to Step S403. On the other hand, if it is decided that the shared storage battery402is fully charged, it is regarded that the shared storage battery402has no vacant capacity, and the flow goes to Step S409.

If it is decided in Step S402that the shared storage battery402is not fully charged, it is checked in Step S403whether or not the unit control portion301has output the request to discharge (request to sell electricity) that means to discharge (sell) the surplus electric power of the unit300to the group400. Here, if it is decided that the unit control portion301has output the request to discharge, the flow goes to Step S404. On the other hand, if it is decided that the unit control portion301has not output the request to discharge, the flow goes to Step S407.

If it is decided in Step S403that the unit control portion301has output the request to discharge, as a content of the instruction to discharge to be replied to the unit control portion301, a flag that means to allow the DC power discharging of the unit300is output in Step S404. This state corresponds to the above-mentioned first operation state or the third operation state.

On the other hand, if it is decided in Step S403that the unit control portion301has not output the request to discharge, as a content of the instruction to discharge to be replied to the unit control portion301, the flag that means to allow the DC power discharging of the unit300is stopped in Step S407. In other words, as a content of the instruction to discharge to be replied to the unit control portion301, a flag that means not to allow the DC power discharging of the unit300is output. This state corresponds to the above-mentioned second operation state.

In addition, if it is decided in Step S402that the shared storage battery402is fully charged, in Step S409, as a content of the instruction to discharge to be replied to the unit control portion301, the flag that means to allow the DC power discharging of the unit300is stopped. In other words, as a content of the instruction to discharge to be replied to the unit control portion301, the flag that means not to allow the DC power discharging of the unit300is output. This state corresponds to the above-mentioned fourth operation state, the fifth operation state, or the sixth operation state.

After performing one of Steps S404, S407, and S409, it is checked in Step S405whether or not the unit control portion301has output a request to charge that means to compensate for the short electric power of the unit300by charging (buying) electricity from the group400(request to buy electricity). Here, if it is decided that the unit control portion301has output the request to charge, the flow goes to Step S406. On the other hand, if it is decided that the unit control portion301has not output the request to charge, the flow goes to Step S408.

If it is decided in Step S405that the unit control portion301has output the request to charge, as a content of the instruction to charge to be replied to the unit control portion301, the flag that means to allow the DC power discharging of the unit300is output in Step S406. This state corresponds to the above-mentioned second operation state, the third operation state, the fifth operation state, or the sixth operation state. After that, the flow goes back to Step S401.

On the other hand, if it is decided in Step S405that the unit control portion301has not output the request to charge, as a content of the instruction to charge to be replied to the unit control portion301, the flag that means to allow the DC power discharging of the unit300is stopped in Step S408. In other words, as a content of the instruction to charge to be replied to the unit control portion301, the flag that means not to allow the DC power discharging of the unit300is output. This state corresponds to the above-mentioned first operation state, or the fourth operation state. After that, the flow goes back to Step S401.

In addition, if it is decided in Step S401that the discharging electric power is not equal or lower than the charging electric power, it is checked in Step S410whether or not the unit control portion301has output the request to discharge that means to discharge (sell) the surplus electric power of the unit300to the group400(request to sell electricity). Here, if it is decided that the unit control portion301has output the request to discharge, the flow goes to Step S411. On the other hand, if it is decided that the unit control portion301has not output the request to discharge, the flow goes to Step S413.

If it is decided in Step S410that the unit control portion301has output the request to discharge, as a content of the instruction to discharge to be replied to the unit control portion301, the flag that means to allow the DC power discharging of the unit300is output in Step S411. This state corresponds to the above-mentioned seventh operation state or the ninth operation state.

On the other hand, if it is decided in Step S410that the unit control portion301has not output the request to discharge, as a content of the instruction to discharge to be replied to the unit control portion301, the flag that means to allow the DC power discharging of the unit300is stopped in Step S413. In other words, as a content of the instruction to discharge to be replied to the unit control portion301, the flag that means not to allow the DC power discharging of the unit300is output. This state corresponds to the above-mentioned eighth operation state.

In Step S412after performing one of Steps S411and S413, regardless whether or not the unit control portion301has output the request to charge that means to compensate the short electric power of the unit300by charging (buying) electricity from the group400(request to buy electricity), as a content of the instruction to charge to be replied to the unit control portion301, the flag that means to allow the DC power discharging of the unit300is stopped. In other words, as a content of the instruction to charge to be replied to the unit control portion301, the flag that means not to allow the DC power discharging of the unit300is output. This state corresponds to the above-mentioned seventh operation state, the eighth operation state, or the ninth operation state. After that, the flow goes back to Step S401.

FIG. 19is a schematic diagram illustrating charge/discharge control of the shared electric power line. On charging paths from a shared electric power line500to shared storage batteries501and502, there are disposed charge control portions505and506, respectively. On discharging path from the shared storage batteries501and502to the shared electric power line500, there are disposed discharge control portions507and508, respectively. Between the shared electric power line500and the charge control portion505or506, there is disposed a switch509or510for charging control. Between the shared storage battery501or502and the discharge control portion507or508, there is disposed a switch511or512for discharging control.

The charge control portion505includes a step-up/down DC/DC converter505a, and a constant current driver505b. When charging the shared storage battery501from the shared electric power line500, the charge control portion505converts the DC electric power supplied from the shared electric power line500into a level suitable for charging the shared storage battery501. For instance, if an optimal charging voltage of the shared storage battery501is 30 V, a target output voltage of the step-up/down DC/DC converter505ashould be set to approximately 31 V (an optimal charging voltage of 30 V of the shared storage battery501plus a drive voltage of 1 V of the constant current driver505b). With this setting, for example, if an input voltage Vin from the shared electric power line500is 100 V, the step-up/down DC/DC converter505asteps down the input voltage Vin of 100 V to generate an output voltage Vout of 31 V, and outputs this output voltage Vout to the shared storage battery501. Note that thanks to the constant current driver505b, charging current Ic into the shared storage battery501can be maintained to be a predetermined value.

The charge control portion506includes the step-up/down DC/DC converter506aand the constant current driver506b. When charging the shared storage battery502from the shared electric power line500, the charge control portion506converts the DC electric power supplied from the shared electric power line500into a level suitable for charging the shared storage battery502. For instance, if an optimal charging voltage of the shared storage battery502is 150 V, a target output voltage of the step-up/down DC/DC converter506ashould be set to approximately 151 V (an optimal charging voltage 150 V of the shared storage battery502plus a drive voltage of 1 V of the constant current driver506b). With this setting, for example, if the input voltage Vin from the shared electric power line500is 100 V, the step-up/down DC/DC converter506asteps up the input voltage Vin of 100 V to generate the output voltage Vout of 151 V, and outputs this output voltage Vout to the shared storage battery502. Note that thanks to the constant current driver506b, charging current Ic into the shared storage battery502can be maintained to be a predetermined value.

The discharge control portion507includes a step-up/down DC/DC converter507a, a resistor507bfor detecting discharge current Id, and a diode for preventing a reverse current507c. When discharging the shared storage battery501to the shared electric power line500, the discharge control portion507converts the DC electric power discharged from the shared storage battery501into a level suitable for supplying to the shared electric power line500. For instance, if an applied voltage to the shared electric power line500is 100 V, a target output voltage of the step-up/down DC/DC converter507ashould be set to approximately 101 V (a minimum voltage level necessary for discharging to the shared electric power line500by the discharge current Id). With this setting, for example, if the input voltage Vin from the shared storage battery501is 30 V, the step-up/down DC/DC converter507asteps up the input voltage Vin of 30 V to generate the output voltage Vout of 101 V, and outputs this output voltage Vout to the shared electric power line500.

The discharge control portion508includes a step-up/down DC/DC converter508a, a resistor508bfor detecting discharge current Id, and a diode for preventing a reverse current508c. When discharging the shared storage battery502to the shared electric power line500, the discharge control portion508converts the DC electric power discharged from the shared storage battery502into a level suitable for supplying to the shared electric power line500. For instance, if the applied voltage to the shared electric power line500is 100 V, a target output voltage of the step-up/down DC/DC converter508ashould be set to approximately 101 V (a minimum voltage level necessary for discharging to the shared electric power line500by the discharge current Id). With this setting, for example, if the input voltage Vin from the shared storage battery502is 150 V, the step-up/down DC/DC converter508asteps down the input voltage Vin of 150 V to generate the output voltage Vout of 101 V, and outputs this output voltage Vout to the shared electric power line500.

Note that the charge control portions505and506, and the discharge control portions507and508may always work, but it is desirable to control on and off of operation states of the charge control portions505and506, and the discharge control portions507and508in accordance with on and off of the switches509and510for charging control and the switches511and512for discharging control, in order to reduce unnecessary power consumption.

In this case, as an enable signal for turning on and off the operation states of the charge control portions505and506, it is possible to use the on/off control signals of the switches509and510. Alternatively, it is possible to use the instruction to charge or the instruction to buy electricity communicated between the upper class group control portion (including the route control portion) and the lower class group control portion (including the unit control portion).

In addition, as an enable signal for turning on and off operation states of the discharge control portions507and508, it is possible to use the on/off control signals of the switches511and512. Alternatively, it is possible to use the instruction to discharge or the instruction to sell electricity communicated between the upper class group control portion (including the route control portion) and the lower class group control portion (including the unit control portion).

FIG. 20is a schematic diagram illustrating a structural example of the route. A plurality of groups400of the uppermost class (N-th class inFIG. 10) belong to a route600in this structural example. The route600includes a route control portion601, a shared storage battery602, an electric power monitoring portion603, a charge control portion604, a discharge control portion605, a shared electric power line606, an electric power monitoring portion607, a discharge control portion608, an AC/DC converter609, a DC/AC converter610, an electric power monitoring portion611, switches e1and e2for charging, and switches f1and f2for discharge. Note thatFIG. 20is a diagram in which components of the route600are noted, and components outside the route (components of the group400) are illustrated only partially.

When the route control portion601performs charge/discharge of the DC electric power between the shared storage battery602of the route600and the shared storage battery402of the group400, it receives the request to charge or the request to discharge from the group control portion401, and as reply to the same, outputs the instruction to charge or the instruction to discharge to the group control portion401.

Note that the route control portion601includes an electric power company interface portion601a, a charge/discharge control portion601b, a lower group electric power monitoring portion601c, and a lower group controller601d. The electric power company interface portion601areceives a monitor result of the electric power monitoring portion611. The charge/discharge control portion601bperforms on/off control of the switches e1and e2and on/off control of the switches f1and f2. The lower group electric power monitoring portion601cintegrally manages billing information of each of the plurality of groups400(trade balance of the DC electric power). The lower group controller601dperforms intercommunication with the group control portion401.

The shared storage battery602is connected to the shared electric power line606, and performs charge/discharge of the DC electric power with the shared storage battery402of the lower group400. In addition, the shared storage battery602performs buying/selling electricity with an electric power company612via the AC/DC converter609or the DC/AC converter610. In other words, the shared storage battery602of the route600is charged by “DC power charging from the shared storage battery402of the lower group400” and “AC power buying from the electric power company612”. In addition, the shared storage battery602of the route600is discharged by “DC power discharging to the shared storage battery402of the lower group400” and “AC power selling to the electric power company612”.

The electric power monitoring portion603monitors the stored electricity of the shared storage battery602. For instance, if the stored electricity of the shared storage battery602is 90% or higher of its maximum value, the electric power monitoring portion603decides that the shared storage battery602is substantially fully charged state. If the stored electricity is 30% or higher and lower than 90%, it is decided to be a stable state. If the stored electricity is lower than 30%, it is decided to be in the power shortage state.

The charge control portion604converts the DC electric power supplied from the shared electric power line606or the AC/DC converter609into a level suitable for charging the shared storage battery602.

The discharge control portion605converts the DC electric power discharged from the shared storage battery602into a level suitable for supplying to the shared electric power line606or the DC/AC converter610.

The shared electric power line606is a path for charging and discharging the DC electric power between the shared storage battery602of the lower group400and the shared storage battery602of the route600.

The electric power monitoring portion607is an electric power meter that accumulates the DC electric power amount traded between the group400and the shared electric power line606for a predetermined period (for example, one month), so as to obtain billing information (trade balance of the DC electric power) with respect to the group400.

The discharge control portion608converts the DC electric power discharged from the shared storage battery402of the group400into a level suitable for supplying to the shared electric power line606.

The AC/DC converter609converts the AC electric power supplied from the electric power company612into the DC electric power and outputs the DC electric power to the shared storage battery602.

The DC/AC converter610converts the DC electric power discharged from the shared storage battery602into AC electric power and outputs the AC electric power to the electric power company612.

The electric power monitoring portion611is an electric power meter that accumulates AC electric power amount traded between the route600and the electric power company612for a predetermined period (for example, one month), so as to obtain billing information (trade balance of the AC electric power) with respect to the route600.

The electric power company612performs buying and selling of the AC electric power with the route600.

The switch e1is controlled to be turned on and off by the route control portion601so as to make and break a connection of the charging path from the AC/DC converter609to the shared storage battery602. The switch e2is controlled to be turned on and off by the route control portion601so as to make and break a connection of the charging path from the shared electric power line606to the shared storage battery602.

The switch f1is controlled to be turned on and off by the route control portion601so as to make and break a connection of the discharging path from the shared storage battery602to the DC/AC converter610. The switch f2is controlled to be turned on and off by the route control portion601so as to make and break a connection of the discharging path from the shared storage battery602to the shared electric power line606.

FIG. 21is an operation list of the route control portion601, which shows, in order from the left, numbers assigned to operation states, a result of monitoring electric power of the electric power monitoring portion603, presence or absence of the request to charge or the request to discharge output from the lower group control portion401, a content of the instruction to charge or the instruction to discharge output from the route control portion601, on/off states of the switches e1and e2for charging, on/off states of the switches f1and f2for discharging, and a buying/selling electricity state with the electric power company612.

The first operation state is a state in which the shared storage battery602is substantially fully charged (90% or higher), and all the plurality of group control portions401connected to the lower group output the requests to discharge. In this case, the route control portion601outputs to all the group control portions401the instruction to discharge that means to allow (validate) the DC power discharging of the group400(which is shown by “∘” in the diagram).

Note that in the first operation state, no group control portion401has output the request to charge. Therefore, the route control portion601outputs to all the group control portions401the instruction to charge that means not to allow (invalidate) the DC power charging of the group400(which is shown by “x” in the diagram).

In this first operation state, the route control portion601turns on the switches e2and f1and turns off the switches e1and f2. With this switch control, between the shared storage battery602and the shared storage battery402, the shared storage battery602is charged by the DC electric power discharged from the shared storage battery402. In addition, between the shared storage battery602and the electric power company612, the DC electric power discharged from the shared storage battery602is converted into the AC electric power and is sold to the electric power company.

The second operation state is a state in which the shared storage battery602is substantially fully charged (90% or higher), and all the plurality of group control portions401connected to the lower group output the requests to charge. In this case, the route control portion601outputs to all the group control portions401the instruction to charge that means to allow (validate) the DC power charging of the group400(which is shown by “∘” in the diagram).

Note that in the second operation state, no group control portion401outputs the request to discharge. Therefore, the route control portion601outputs to all the group control portions401the instruction to discharge that means not to allow (invalidate) the DC power discharging of the group400(which is shown by “x” in the diagram).

In this second operation state, the route control portion601turns off the switches e1, e2, and f1, and turns on the switch f2. With this switch control, the shared storage battery402is charged by the DC electric power discharged from the shared storage battery602. Note that the buying/selling electricity with the electric power company612is stopped.

The third operation state is a state in which the shared storage battery602is substantially fully charged (90% or higher), and a part of the plurality of group control portions401connected to the lower group output the requests to discharge while the other part of the same output the requests to charge. In this case, the route control portion601outputs to the group control portions401that have output the request to discharge the instruction to discharge that means to allow (validate) the DC power discharging of the group400(which is shown by “∘” in the diagram), and outputs to the group control portions401that have output the request to charge the instruction to charge that means to allow (validate) the DC power charging of the group400(which is shown by “∘” in the diagram).

In this third operation state, the route control portion601turns off the switch e1and turns on the switches c2, d1, and d2. With this switch control, between the shared storage battery602and the shared storage battery402in the power surplus state, the shared storage battery602is charged by the DC electric power discharged from the shared storage battery402. In addition, between the shared storage battery602and the shared storage battery402in the power shortage state, the shared storage battery402is charged by the DC electric power discharged from the shared storage battery602. Further, between the shared storage battery602and the electric power company612, the DC electric power discharged from the shared storage battery602is converted into the AC electric power and is sold to the electric power company612.

The fourth operation state is a state in which the stored electricity of the shared storage battery602is in the stable state (30% or higher and lower than 90%), and all the plurality of group control portions401connected to the lower group output the requests to discharge. In this case, the route control portion601outputs to all the group control portions401the instruction to discharge that means to allow (validate) the DC power discharging of the group400(which is shown by “∘” in the diagram).

Note that in the fourth operation state, no group control portion401outputs the request to charge. Therefore, the route control portion601outputs to all the group control portions401the instruction to charge that means not to allow (invalidate) the DC power charging of the group400(which is shown by “x” in the diagram).

In this fourth operation state, the route control portion601turns on the switch e2and turns off the switches e1, f1, and f2. With this switch control, between the shared storage battery602and the shared storage battery402, the shared storage battery602is charged by the DC electric power discharged from the shared storage battery402. Note that buying/selling electricity with the electric power company612is stopped.

The fifth operation state is a state in which the stored electricity of the shared storage battery602is in the stable state (30% or higher and lower than 90%), and all the plurality of group control portions401connected to the lower group output the requests to charge. In this case, the route control portion601outputs to all the group control portions401the instruction to charge that means to allow (validate) the DC power charging of the group400(which is shown by “∘” in the diagram).

Note that in the fifth operation state, no group control portion401outputs the request to discharge. Therefore, the route control portion601outputs to all the group control portions401the instruction to discharge that means not to allow (invalidate) the DC power discharging of the group400(which is shown by “x” in the diagram).

In this fifth operation state, the route control portion601turns off the switches e1, e2, and f1, and turns on the switch f2. With this switch control, the shared storage battery402is charged by the DC electric power discharged from the shared storage battery602. Note that buying/selling electricity with electric power company612is stopped.

The sixth operation state is a state in which the stored electricity of the shared storage battery602is in the stable state (30% or higher and lower than 90%), and a part of the plurality of group control portions401connected to the lower group output the requests to discharge while the other part of the same output the requests to charge. In this case, the route control portion601output to the group control portions401that have output the requests to discharge the instruction to discharge that means to allow (validate) the DC power discharging of the group400(which is shown by “∘” in the diagram), and outputs to the group control portions401that have output the requests to charge the instruction to charge that means to allow (validate) the DC power charging of the group400(which is shown by “∘” in the diagram).

In this sixth operation state, the route control portion601turns off the switches e1and f1, and turns on the switches e2and f2. With this switch control, between the shared storage battery602and the shared storage battery402in the power surplus state, the shared storage battery602is charged by the DC electric power discharged from the shared storage battery402. In addition, between the shared storage battery602and the shared storage battery602in the power shortage state, the shared storage battery402is charged by the DC electric power discharged from the shared storage battery602. Note that buying/selling electricity with the electric power company612is stopped.

The seventh operation state is a state in which the shared storage battery602is in the power shortage state (lower than 30%), and all the plurality of group control portions401connected to the lower group output the requests to discharge. In this case, the route control portion601outputs to all the group control portions401the instruction to discharge that means to allow (validate) the DC power discharging of the group400(which is shown by “∘” in the diagram).

Note that in the seventh operation state, no group control portion401outputs the request to charge. Therefore, the route control portion601outputs to all the group control portions401the instruction to charge that means not to allow (invalidate) the DC power charging of the group400(which is shown by “x” in the diagram).

In this seventh operation state, the route control portion601turns off the switches e1, f1, and f2, and turns on the switch e2. With this switch control, the shared storage battery602is charged by the DC electric power discharged from the shared storage battery402. Note that buying/selling electricity with the electric power company612is stopped.

The eighth operation state is a state in which the shared storage battery602is in the power shortage state (lower than 30%), and all the plurality of group control portions401connected to the lower group output the requests to charge. In this case, the route control portion601outputs to all the group control portions401the instruction to charge that means not to allow (invalidate) the DC power charging of the group400(which is shown by “x” in the diagram).

Note that in the eighth operation state, no group control portion401outputs the request to discharge. Therefore, the route control portion601outputs to all the group control portions401the instruction to discharge that means not to allow (invalidate) the DC power discharging of the group400(which is shown by “x” in the diagram).

In this eighth operation state, the route control portion601turns on the switch e1, and turns off the switches e2, f1, and f2. With this switch control, between the shared storage battery602and the electric power company612, the AC electric power bought from the electric power company612is converted into the DC electric power, and the shared storage battery602is charged by this DC electric power. Note that charge/discharge with the shared storage battery402is stopped.

The ninth operation state is a state in which the shared storage battery602is in the power shortage state (lower than 30%), and a part of the plurality of group control portions401connected to the lower group output the requests to discharge while the other part of the same output the requests to charge. In this case, the route control portion601outputs to the group control portions401that have output the requests to discharge the instruction to discharge that means to allow (validate) the DC power discharging of the group400(which is shown by “∘” in the diagram), and outputs to the group control portions401that have output the requests to charge the instruction to charge that means not to allow (invalidate) the DC power charging of the group400(which is shown by “x” in the diagram).

In this ninth operation state, the route control portion601turns on the switches e1and e2, and turns off the switches d1and d2. With this switch control, between the shared storage battery602and the shared storage battery402in the power surplus state, the shared storage battery602is charged by the DC electric power discharged from the shared storage battery402. In addition, between the shared storage battery602and the shared storage battery402in the power shortage state, the DC power charging of the shared storage battery402is stopped. In addition, between the shared storage battery602and the electric power company612, the AC electric power bought from the electric power company612is converted into the DC electric power, and the shared storage battery602is charged by this DC electric power.

FIG. 22is an operation flowchart of the route control portion601.

It is checked in Step S501whether or not the stored electricity of the shared storage battery602is 90% or higher of the maximum value. Here, if it is decided that the stored electricity of the shared storage battery602is 90% or higher of the maximum value, it is regarded that the shared storage battery602is substantially fully charged, and the flow goes to Step S502. On the other hand, if it is decided that the stored electricity of the shared storage battery602is not the 90% or higher of the maximum value, it is regarded that the shared storage battery602can be charged, and the flow goes to Step S508.

If it is decided in Step S501that the stored electricity of the shared storage battery602is 90% or higher of the maximum value, it is checked in Step S502whether or not the group control portion401has output the request to discharge that means to discharge the surplus electric power of the group400to the route600. Here, if it is decided that the group control portion401has output the request to discharge, the flow goes to Step S503. On the other hand, if it is decided that the group control portion401has not output the request to discharge, the flow goes to Step S506.

If it is decided in Step S502that the group control portion401has output the request to discharge, the AC power selling from the shared storage battery602to the electric power company612is performed in Step S503, and as a content of the instruction to discharge replied to the group control portion401, the flag that means to allow the DC power discharging of the group400is output. This state corresponds to the above-mentioned first operation state or the third operation state.

On the other hand, if it is decided in Step S502that the group control portion401has not output the request to discharge, the AC power selling from the shared storage battery602to the electric power company612is stopped in Step S506, and as a content of the instruction to discharge replied to the group control portion401, the flag that means to allow the DC power discharging of the group400is stopped. In other words, as a content of the instruction to discharge replied to the group control portion401, a flag that means not to allow the DC power discharging of the group400is output. This state corresponds to the above-mentioned second operation state.

In addition, if it is decided in Step S501that the stored electricity of the shared storage battery602is not 90% or higher of the maximum value, it is checked in Step S508whether or not the stored electricity of the shared storage battery602is 30% or higher of the maximum value. Here, if it is decided that the stored electricity of the shared storage battery602is 30% or higher of the maximum value, it is regarded that the stored electricity of the shared storage battery602is in the stable state, and the flow goes to Step S509. On the other hand, if it is decided that the stored electricity of the shared storage battery602is not 30% or higher of the maximum value, it is regarded that the shared storage battery602is in the power shortage state, and the flow goes to Step S512.

In Step S508, if it is decided that the stored electricity of the shared storage battery602is 30% or higher of the maximum value, it is checked in Step S509whether or not the group control portion401has output the request to discharge that means to discharge the surplus electric power of the group400to the route600. Here, if it is decided that the group control portion401has output the request to discharge, the flow goes to Step S510. On the other hand, if it is decided that the group control portion401has not output the request to discharge, the flow goes to Step S511.

If it is decided in Step S509that the group control portion401has output the request to discharge, as a content of the instruction to discharge replied to the group control portion401, the flag that means to allow the DC power discharging of the group400is output in Step S510. This state corresponds to the above-mentioned fourth operation state, or the sixth operation state.

On the other hand, if it is decided in Step S509that the group control portion401has not output the request to discharge, as a content of the instruction to discharge replied to the group control portion401, the flag that means to allow the DC power discharging of the group400is stopped in Step S511. In other words, as a content of the instruction to discharge replied to the group control portion401, the flag that means not to allow the DC power discharging of the group400is output. This state corresponds to the above-mentioned fifth operation state.

After any one of Steps S503, S506, S510, and S511, it is checked in Step S504whether or not the group control portion401has output the request to charge that means to compensate for the short electric power of the group400by charging from the route600. Here, if it is decided that the group control portion401has output the request to charge, the flow goes to Step S505. On the other hand, if it is decided that the group control portion401has not output the request to charge, the flow goes to Step S507.

If it is decided in Step S504that the group control portion401has output the request to charge, as a content of the instruction to charge replied to the group control portion401, a flag that means to allow the DC power charging of the group400is output in Step S505. This state corresponds to the above-mentioned second operation state, the third operation state, the fifth operation state, or the sixth operation state. After that, the flow goes back to Step S501.

On the other hand, if it is decided in Step S504that the group control portion401has not output the request to charge, in Step S507, as a content of the instruction to charge replied to the group control portion401, the flag that means to allow the DC power charging of the group400is stopped. In other words, as a content of the instruction to charge replied to the group control portion401, a flag that means not to allow the DC power charging of the group400is output. This state corresponds to the above-mentioned first operation state, or the fourth operation state. After that, the flow goes back to Step S501.

In addition, if it is decided in Step S508that the stored electricity of the shared storage battery602is not 30% or higher of the maximum value, it is checked in Step S512whether or not the group control portion401has output the request to discharge that means to discharge the surplus electric power of the group400to the route600. Here, if it is decided that the group control portion401has output the request to discharge, the flow goes to Step S513. On the other hand, if it is decided that the group control portion401has not output the request to discharge, the flow goes to Step S515.

If it is decided in Step S512that the group control portion401has output the request to discharge, in Step S513, as a content of the instruction to discharge replied to the group control portion401, the flag that means to allow the DC power discharging of the group400is output. This state corresponds to the above-mentioned seventh operation state or the ninth operation state.

On the other hand, if it is decided in Step S512that the group control portion401has not output the request to discharge, as a content of the instruction to discharge replied to the group control portion401, the flag that means to allow the DC power discharging of the group400is stopped in Step S515. In other words, as a content of the instruction to discharge replied to the group control portion401, the flag that means not to allow the DC power discharging of the group400is output. This state corresponds to the above-mentioned eighth operation state.

After one of Steps S513and S515, in Step S514, regardless that the group control portion401has output the request to charge that means to compensate for the short electric power of the group400by charging from the route600, as a content of the instruction to charge replied to the group control portion401, the flag that means to allow the DC power charging of the group400is stopped. In other words, as a content of the instruction to charge replied to the group control portion401, the flag that means not to allow the DC power charging of the group400is output. This state corresponds to the above-mentioned seventh operation state, the eighth operation state, or the ninth operation state. After that, the flow goes back to Step S501.

FIG. 23is a conceptual diagram of the DC electric power network described above. Note that in this diagram, a private house is exemplified as the unit. In addition, as an example of the group to which the private house belongs, there are shown a floor of a multiple dwelling house, a building of the multiple dwelling house, a whole (or a company) of the multiple dwelling house, a municipality, and a prefecture. Further as a final route, there is shown a state or a country.

As illustrated in this diagram, by increasing hierarchical groups forming the DC electric power network, the DC electric power network can be expanded from a small group to a worldwide area. In particular, by establishing a large DC electric power network, the stored electricity of the whole DC electric power network can be maintained even if one district is in bad weather if another district is in fine weather. Therefore, the problem of the photovoltaic power generation system that the generated electric power is easily affected by weather can be solved.

FIG. 24is an interconnection diagram between the DC electric power network and the AC electric power network. As illustrated in this diagram, in a developing stage of expanding the DC electric power network, it is possible to achieve electric power sharing between distant DC electric power networks by interconnection with the AC electric power network as an existing infrastructure.

As described above, according to the second example too, it is possible to provide the electric power system including a first unit equipped with a first power source, a first rechargeable battery to which an output of the first power source is input, an a first power consuming portion to which an output of the first rechargeable battery is input; a second rechargeable battery; and an electric power line for sharing electric power between the first rechargeable battery and the second rechargeable battery. Further, in the case of the second example, the first power source (and the second power source) is a solar panel.

Here, the second example is based on a concept that emphasizes self-sufficiency by the photovoltaic power generation and DC electric power distribution avoiding a conversion loss between AC and DC. Therefore, the second example adopts the concept in which self-consuming and interchange of the photovoltaic power generation electric power is given high priority first, and selling electricity is performed if there is surplus.

In addition, the structure of the present invention can be modified variously from the above-mentioned embodiment without deviating from the spirit of the present invention. In other words, the above-mentioned embodiment is merely an example and should not be interpreted as a restriction. The technical scope of the present invention is defined not by the above description of the embodiment but by the claims, which should be interpreted to include all modifications belonging to the meaning and the scope equivalent to the claims.

For instance, as for the above-mentioned second example,FIG. 11illustrates the structure without a charging path from the electric power company317to the unit storage battery302as an example for description, but the structure of the present invention is not limited to this. As illustrated inFIG. 25, it is possible to adopt a structure equipped with the charging path from the electric power company317to the unit storage battery302. In this case, the unit storage battery302can be charged by “DC power supplying from the power conditioner (not shown)” and “DC power buying from the shared storage battery315”, as well as by “AC power buying from the electric power company317”. Note that when the DC electric power stored in the unit storage battery302is shared, the DC electric power stored by buying electricity from the electric power company317may be excluded from the sharing target, or on the contrary, it may be included in the sharing target.

INDUSTRIAL APPLICABILITY

The present invention provides an electric power supply system for a house having an electricity storing function.

EXPLANATION OF NUMERALS