Distributed power supply system and charging / discharging device

Abstract

To provide a distributed power supply system capable of switching between a state of accelerating a reverse power flow and a state of suppressing a reverse power flow of generated power of a solar cell device.SOLUTION: In the distributed power supply system, a power generation device 8 adjusts supply power P6 to be supplied to a second connection point 5 so as to follow the sum of load power P4 to be received by a power load device 3 from a third connection point 6 and received power P7 to be received by a charging / discharging device 9 from the third connection point 6. When a charging / discharging unit 9a has a greater tendency to charge, the charging / discharging device 9 operates by switching to a first operation mode to adjust the received power P7 between the maximum received power and the minimum received power so that a reverse power flow of supply power P5 of a solar cell device 7 is promoted. When the charging / discharging unit 9a has a greater tendency to discharge, the charging / discharging device 9 operates by switching to a second operation mode to adjust the received power P7 so that the reverse power flow of the supply power P5 of the solar cell device 7 is suppressed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a distributed power system including a power line connected to a power grid, a solar cell device, a power generation device, and a charge / discharge device, and to the charge / discharge device. [Background technology]

[0002] Patent Document 1 (JP Patent Publication No. 5731241) describes a distributed power system including a power receiving line connected to a commercial power source, a solar cell, a fuel cell, and a power storage unit. In this distributed power system, a power storage controller controls the operation of a power storage-side inverter to selectively execute a charging operation for charging the power storage unit and a discharging operation for discharging the power storage unit. When charging the power storage unit, the power storage controller sets the target charging power in a state where the total load power, which is the sum of the load power and the target charging power for charging the power storage unit, is fixed to the maximum output power of the fuel cell. For example, when the maximum output power of the fuel cell is 700 W and the load power is 300 W, the target charging power is set to 400 W. The power generation controller of the fuel cell adjusts the output power according to the total load power, which is the sum of the load power and the target charging power for charging the charge / discharge unit, under conditions that do not cause a reverse power flow from the fuel cell to the commercial power source. In other words, the fuel cell outputs the maximum generated power under conditions that do not cause a reverse power flow from the fuel cell to the commercial power source. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5731241 Summary of the Invention [Problem to be solved by the invention]

[0004] FIG. 9 is a diagram showing the configuration of a distributed power system having the same configuration as that of Patent Document 1. Specifically, FIG. 9 describes a distributed power system including a power line 2 connected to a power grid 1, a solar cell device 7, a fuel cell device 8 as a power generation device, and a charge / discharge device 9. In this distributed power system, the charge / discharge device 9 charges and discharges with reference to the measurement result of a power measurement unit 12 that measures the power flowing from the second connection point 5 to the third connection point 6 so that the power becomes the maximum power generation power (e.g., 700 W) of the fuel cell device 8. Further, the fuel cell device 8 controls the supply power with reference to the measurement result of a power measurement unit 11 that measures the power flowing from the first connection point 4 to the second connection point 5 so that the power becomes a predetermined power (e.g., 0 W). The values of the respective powers shown in FIG. 9 are the same as those in the above example of Patent Document 1, and this is a case where the output power of the fuel cell device 8 is 700 W, the load power of the power load device 3 is 300 W, and the charging power of the charge / discharge device 9 is 400 W. That is, in the distributed power system described in Patent Document 1, the goal is to reverse all of the generated power of the solar cell device 7 to the power grid 1.

[0005] When the generated power of the solar cell device 7 is purchased under the feed-in tariff system, economic benefits will increase if control is performed so that all of the generated power of the solar cell device 7 is reverse-fed to the power grid 1 as described above. However, when it becomes impossible to apply the feed-in tariff system, it may be preferable not to reverse-feed the generated power of the solar cell device 7. In that case, if the fuel cell device 8 and the charge / discharge device 9 have been performing the same control as before, the generated power of the solar cell device 7 cannot be actively charged by the charge / discharge device 9 or actively consumed by the power load device 3.

[0006] Note that it is also possible to change the connection so that the fuel cell device 8 is connected to the downstream side of the third connection point 6 (that is, between the third connection point 6 and the power load device 3) and the generated power of the solar cell device 7 is charged by the charge / discharge device 9, but there is a problem that wiring changes are required and the system connection application needs to be redone.

[0007] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a distributed power generation system and a charge / discharge device that can switch between a state that promotes reverse flow of power generated by a solar cell device and a state that suppresses reverse flow. [Means for solving the problem]

[0008] A characteristic configuration of a distributed power system according to the present invention for achieving the above object is a system including a power line connected to a power grid, a solar cell device, a power generation device, and a charge / discharge device having a charge / discharge unit, a connection point to the power grid is provided on the upstream side of the power line, and a first connection point, a second connection point, and a third connection point are provided in that order on the power line from the connection point to the power grid toward the downstream side; a power load device is connected to the third connection point, the solar cell device is connected to the first connection point, the power generation device is connected to the second connection point, and the charging / discharging device is connected to the third connection point; When the charging power from the third connection point by the charging / discharging device is regarded as positive received power, and the discharging power to the third connection point by the charging / discharging device is regarded as negative received power, the power generation device adjusts the supply power supplied to the second connection point within a range between maximum supply power and minimum supply power so as to follow the sum of the load power received by the power load device from the third connection point and the received power received by the charging / discharging device from the third connection point; The charging / discharging device switches to a first operating mode in which the received power is adjusted in a range between maximum received power and minimum received power so as to promote reverse flow of the generated power of the solar cell device when the charging / discharging history of the charging / discharging unit indicates that there was a strong tendency to charge, and switches to a second operating mode in which the received power is adjusted in a range between maximum received power and minimum received power so as to suppress reverse flow of the generated power of the solar cell device when the charging / discharging history of the charging / discharging unit indicates that there was a strong tendency to discharge.

[0009] Here, the charging / discharging device may switch to the second operating mode and operate when the maximum value of the remaining storage capacity of the charging / discharging unit during a first predetermined period in the past when it was operating in the first operating mode is equal to or less than a first remaining storage capacity, and may switch to the first operating mode and operate when the minimum value of the remaining storage capacity of the charging / discharging unit during a second predetermined period in the past when it was operating in the second operating mode is equal to or greater than a second remaining storage capacity that is greater than the first remaining storage capacity. Alternatively, the charging / discharging device may switch to the second operating mode and operate when a total amount of discharged power from the charging / discharging unit during a first predetermined period in the past when it was operating in the first operating mode is equal to or greater than a first discharging power amount or a total amount of charged power to the charging / discharging unit is equal to or less than a first charging power amount, and may switch to the first operating mode and operate when a total amount of discharged power from the charging / discharging unit during a second predetermined period in the past when it was operating in the second operating mode is equal to or less than a second discharging power amount or a total amount of charged power to the charging / discharging unit is equal to or greater than the second charging power amount.

[0010] According to the above characteristic configuration, the power generation device adjusts the supply power so as to follow the sum of the load power received by the power load device from the third connection point and the received power received by the charging / discharging device from the third connection point. In other words, when the sum of the load power of the power load device and the received power of the charging / discharging device is large, the supply power of the power generation device increases accordingly, and when the sum of the load power of the power load device and the received power of the charging / discharging device is small, the supply power of the power generation device decreases accordingly. In addition, when the charging / discharging device adjusts to increase the received power, the sum of the load power of the power load device and the received power of the charging / discharging device increases. As a result, when the supply power of the power generation device cannot cover the sum of the load power of the power load device and the received power of the charging / discharging device, the generated power of the solar cell device is used to cover that power. In other words, it can be said that the reverse flow of the generated power of the solar cell device is suppressed by the charging / discharging device adjusting to increase the received power. On the other hand, when the charging / discharging device adjusts to reduce the received power, the sum of the load power of the power load device and the received power of the charging / discharging device decreases. As a result, if the sum of the load power of the power load device and the received power of the charging / discharging device can be covered by the power supplied by the power generation device, the generated power of the solar cell device is not used to cover that power. In other words, it can be said that the reverse flow of the generated power of the solar cell device is promoted by the charging / discharging device adjusting the received power to be smaller.

[0011] In this way, by adjusting the received power of the charging / discharging device, it is possible to promote the reverse flow of the generated power of the solar cell device and suppress the reverse flow of the generated power of the solar cell device. In this characteristic configuration, when the charge / discharge history of the charging / discharging unit indicates that there was a strong tendency to charge, the charging / discharging device operates in a first operation mode in which the received power is adjusted so that the reverse flow of the generated power of the solar cell device is promoted, and when the charge / discharge history of the charging / discharging unit indicates that there was a strong tendency to discharge, the charging / discharging device operates in a second operation mode in which the received power is adjusted so that the reverse flow of the generated power of the solar cell device is suppressed. In other words, when the charge / discharge history of the charging / discharging unit indicates that there was a strong tendency to charge, the reverse flow of the generated power of the solar cell device is promoted, that is, the generated power of the solar cell device is less likely to be used for the load power of the power load device and the charging of the charging / discharging device, so that the remaining amount of stored power in the charging / discharging unit can be prevented from becoming too large. In addition, if the charge / discharge history of the charge / discharge unit indicates a strong tendency to discharge, the reverse flow of the generated power of the solar cell device is suppressed, i.e., the generated power of the solar cell device is more easily utilized for the load power of the power load device and for charging the charge / discharge device, thereby preventing the remaining storage capacity of the charge / discharge unit from becoming too small. Therefore, it is possible to provide a distributed power supply system that can switch between a state in which the reverse flow of power generated by the solar cell device is promoted and a state in which the reverse flow is suppressed.

[0012] Another characteristic configuration of the distributed power supply system of the present invention is that, in the first operating mode, the charging / discharging device adjusts the received power so that the power flowing from the second connection point to the third connection point on the power line becomes a predetermined second target power, and in the second operating mode, derives a first provisional received power that the charging / discharging device needs to receive from the third connection point when the power flowing from the second connection point to the third connection point on the power line becomes the second target power, and a second provisional received power that the charging / discharging device needs to receive from the third connection point when the power flowing from the power system to the first connection point becomes the predetermined third target power, and determines the larger of the first provisional received power and the second provisional received power to be the received power.

[0013] According to the above characteristic configuration, the received power of the charging / discharging device when operating in the first operation mode is adjusted so that the power flowing from the second connection point to the third connection point on the power line becomes the second target power. Also, the received power of the charging / discharging device when operating in the second operation mode becomes the larger of the first provisional received power that the charging / discharging device needs to receive from the third connection point when the power flowing from the second connection point to the third connection point on the power line is set to the second target power, and the second provisional received power that the charging / discharging device needs to receive from the third connection point when the power flowing from the power grid to the first connection point is set to the predetermined third target power. That is, the received power of the charging / discharging device when operating in the second operation mode is equal to or greater than the received power of the charging / discharging device when operating in the first operation mode. Therefore, while the charging / discharging device is operating in the second operation mode, the generated power of the solar cell device is more easily utilized for the load power of the power load device and for charging the charging / discharging device than while the charging / discharging device is operating in the first operation mode, and as a result, the reverse flow of the generated power of the solar cell device is suppressed. In contrast, while the charging / discharging device is operating in the first operating mode, the generated power of the solar cell device is less likely to be used for the load power of the power load device and for charging the charging / discharging device than while the charging / discharging device is operating in the second operating mode, and as a result, reverse flow of the generated power of the solar cell device is promoted.

[0014] Another characteristic configuration of the distributed power supply system of the present invention is that, in the first operating mode, the charging / discharging device adjusts the received power so that the power flowing from the second connection point to the third connection point on the power line is greater than the generated power of the power generation device by a set power, and in the second operating mode, the charging / discharging device adjusts the received power so that the power flowing from the second connection point to the third connection point on the power line is greater than the generated power of the power generation device by the set power plus the power supplied by the solar cell device to the first connection point.

[0015] According to the above characteristic configuration, the power received by the charging / discharging device when operating in the first operation mode is adjusted so that the power flowing from the second connection point to the third connection point on the power line is greater than the power generated by the power generation device by a set power. Also, the power received by the charging / discharging device when operating in the second operation mode is adjusted so that the power flowing from the second connection point to the third connection point on the power line is greater than the power generated by the power generation device by a set power plus the power supplied by the solar cell device to the first connection point. In other words, the power received by the charging / discharging device when operating in the second operation mode is greater than or equal to the power received by the charging / discharging device when operating in the first operation mode. Therefore, while the charging / discharging device is operating in the second operation mode, the power generated by the solar cell device is more easily used for the load power of the power load device and for charging the charging / discharging device than while the charging / discharging device is operating in the first operation mode, and as a result, the reverse flow of the power generated by the solar cell device is suppressed. In contrast, while the charging / discharging device is operating in the first operating mode, the generated power of the solar cell device is less likely to be used for the load power of the power load device and for charging the charging / discharging device than while the charging / discharging device is operating in the second operating mode, and as a result, reverse flow of the generated power of the solar cell device is promoted.

[0016] A characteristic feature of the charge / discharge device according to the present invention for achieving the above object resides in that it has the functions of the charge / discharge device used in the distributed power supply system.

[0017] According to the above characteristic configuration, a charging / discharging device can be provided that has the functions of a charging / discharging device used in a distributed power generation system, and can switch between a state that promotes reverse flow of power generated by a solar cell device and a state that suppresses reverse flow. [Brief description of the drawings]

[0018] [Figure 1] 1 is a diagram showing a configuration of a distributed power supply system according to a first embodiment. [Diagram 2] 1 is a diagram showing a configuration of a distributed power supply system according to a first embodiment. [Diagram 3] 1 is a diagram showing a configuration of a distributed power supply system according to a first embodiment. [Figure 4] 1 is a diagram showing a configuration of a distributed power supply system according to a first embodiment. [Diagram 5] FIG. 11 is a diagram showing a configuration of a distributed power supply system according to a second embodiment. [Figure 6] FIG. 11 is a diagram showing a configuration of a distributed power supply system according to a second embodiment. [Figure 7] FIG. 11 is a diagram showing a configuration of a distributed power supply system according to a second embodiment. [Figure 8] FIG. 11 is a diagram showing a configuration of a distributed power supply system according to a second embodiment. [Figure 9] FIG. 1 is a diagram showing a configuration of a distributed power supply system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] First Embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A distributed power system according to a first embodiment of the present invention and a charge / discharge device used in the distributed power system will be described below with reference to the drawings. 1 to 4 are diagrams showing the configuration of a distributed power system according to a first embodiment. As shown in the figures, the distributed power system includes a power line 2 connected to a power system 1, a solar cell device 7, a fuel cell device 8 as a power generation device, and a charge / discharge device 9 having a charge / discharge unit 9a. A connection point to the power system 1 is provided on the upstream side of the power line 2, and a first connection point 4, a second connection point 5, and a third connection point 6 are provided on the power line 2 in that order from the connection point to the power system 1 toward the downstream side. A power load device 3 is connected to the third connection point 6, a solar cell device 7 is connected to the first connection point 4, a fuel cell device 8 is connected to the second connection point 5, and a charge / discharge device 9 is connected to the third connection point 6.

[0020] In the figure, the power supplied from the power system 1 to the first connection point 4 is represented as P1. The power supplied from the solar cell device 7 to the first connection point 4 of the power line 2 is represented as P5. The power flowing from the first connection point 4 to the second connection point 5 of the power line 2 is represented as P2. The power flowing from the second connection point 5 to the third connection point 6 of the power line 2 is represented as P3. The power received by the power load device 3 from the third connection point 6 of the power line 2 is represented as P4. The supply power supplied by the fuel cell device 8 to the second connection point 5 of the power line 2 is represented as P6. The charging power from the third connection point 6 by the charging / discharging device 9 is regarded as positive received power, and the discharging power by the charging / discharging device 9 to the third connection point 6 is regarded as negative received power, and the received power is represented as P7.

[0021] The fuel cell device 8 as a power generation device has a fuel cell section 8a as a power generation section, a power conversion section 8b for converting the power generated in the fuel cell section 8a into power of the desired voltage, frequency, and phase and outputting it to the power line 2, and a fuel cell control section 8c as a power generation control section that controls the operation of the fuel cell section 8a and the power conversion section 8b.

[0022] The fuel cell unit 8a can be realized by using, for example, a solid oxide fuel cell (SOFC). Alternatively, the fuel cell unit 8a may be realized by using other types of fuel cells, such as a polymer electrolyte fuel cell (PEFC). Although not shown, the fuel cell device 8 may include a fuel reformer that generates hydrogen or the like as a fuel gas to be supplied to the anode of the fuel cell unit 8a through a reforming process. The fuel cell control unit 8c controls the start and stop of operation, output state, etc. of the fuel cell unit 8a. The fuel cell control unit 8c also controls the power conversion operation by the power conversion unit 8b.

[0023] Information about the power measured by the power measuring unit 11 is transmitted to the fuel cell control unit 8c. The power measuring unit 11 is provided between the first connection point 4 and the second connection point 5 in the middle of the power line 2, and measures the power P2 flowing from the first connection point 4 to the second connection point 5. The power measuring unit 11 is configured using, for example, a current transformer (instrument current transformer) used to detect the current value of the power in the power line 2, and can derive the power value in the power line 2 from the product by a predetermined voltage value (for example, 100V, 200V, etc.). Note that the power measuring unit 11 may transmit only the current value of the power in the power line 2 to the fuel cell control unit 8c, and the fuel cell control unit 8c may derive the power value.

[0024] The power P2 measured by the power measuring unit 11 corresponds to the sum of the load power P4 received by the power load device 3 from the power line 2 and the received power P7 received by the charging / discharging device 9 from the power line 2, minus the power P6 supplied from the fuel cell device 8 to the power line 2.

[0025] The fuel cell control unit 8c of the fuel cell device 8 refers to the measurement result of the power measurement unit 11 and The supply power P6 supplied to the second connection point 5 is controlled within a range between a predetermined minimum supply power and a predetermined maximum supply power so as to follow the sum power P3 of the load power P4 received by the power load device 3 from the third connection point 6 and the received power P7 received by the charge / discharge device 9 from the third connection point 6. For example, the fuel cell device 8 adjusts the supply power P6 from the fuel cell device 8 to the power line 2 so that the power P2 flowing from the first connection point 4 to the second connection point 5 is preferably not negative and is as small a set power as possible (for example, so that the power P2 is 0 W).

[0026] The solar cell device 7 is configured to include an element (not shown) that directly converts the optical energy of incident light (sunlight) into electrical energy, and a power conversion unit (not shown) that converts the power generated by the element into power of the desired voltage, frequency, and phase, and outputs it to the power line 2.

[0027] The charging / discharging device 9 has a charging / discharging unit 9a that charges and discharges power between the power line 2, a power conversion unit 9b, and a charging / discharging control unit 9c that controls the operation of the power conversion unit 9b. The charging / discharging unit 9a can be configured using a secondary battery such as a lithium-ion battery. The charging / discharging control unit 9c controls the operation of the power conversion unit 9b to control the output power (discharging power) from the charging / discharging unit 9a to the power line 2, and the input power (charging power) from the power line 2 to the charging / discharging unit 9a.

[0028] Information on the power measured by the power measuring unit 12 is transmitted to the charge / discharge control unit 9c. In this embodiment, the power measuring unit 12 is provided between the second connection point 5 and the third connection point 6 in the middle of the power line 2, and measures the power P3 flowing from the second connection point 5 to the third connection point 6. In other words, the power P3 measured by the power measuring unit 12 corresponds to the sum of the load power P4 received by the power load device 3 from the power line 2 and the received power P7 received by the charge / discharge device 9 from the power line 2. The power measuring unit 12 is configured using, for example, a current transformer (instrument current transformer) used to detect the current value of the power in the power line 2, and can derive the power value in the power line 2 from the product by a predetermined voltage value (for example, 100V, 200V, etc.). Note that the power measuring unit 12 may transmit only the current value of the power in the power line 2 to the charge / discharge control unit 9c, and the charge / discharge control unit 9c may derive the power value. The charge / discharge control unit 9c then refers to the measurement result of the power measurement unit 12 to control the received power P7 that the charge / discharge device 9 receives from the power line 2.

[0029] Information on the power measured by the power measuring unit 10 is transmitted to the charge / discharge control unit 9c. In this embodiment, the power measuring unit 10 is provided on the power line 2, upstream of the first connection point 4, and measures the power P1 flowing from the power system 1 to the first connection point 4. The power measuring unit 10 is configured using, for example, a current transformer (instrument current transformer) used to detect the current value of the power in the power line 2, and can derive the power value in the power line 2 from the product of the current value and a predetermined voltage value (for example, 100V, 200V, etc.). Note that the power measuring unit 10 may transmit only the current value of the power in the power line 2 to the charge / discharge control unit 9c, and the charge / discharge control unit 9c may derive the power value. Then, the charge / discharge control unit 9c controls the received power P7 that the charge / discharge device 9 receives from the power line 2 by referring to the measurement result of the power measuring unit 10.

[0030] When the charge / discharge history of the charge / discharge unit 9a indicates that there was a strong tendency toward charging, the charge / discharge control unit 9c of the charge / discharge device 9 switches to a first operation mode in which the received power is adjusted in a range between the maximum received power and the minimum received power so as to promote the reverse flow of the power generated by the solar cell device 7, and when the charge / discharge history of the charge / discharge unit 9a indicates that there was a strong tendency toward discharging, the charge / discharge control unit 9c switches to a second operation mode in which the received power is adjusted in a range between the maximum received power and the minimum received power so as to suppress the reverse flow of the power generated by the solar cell device 7.

[0031] In this embodiment, the charging / discharging device 9 switches to the second operating mode and operates when the maximum value of the remaining storage capacity SOC (state of charge) of the charging / discharging unit 9a during a first specified period in the past when it was operating in the first operating mode (an example of the above-mentioned charging / discharging history) is equal to or lower than the first remaining storage capacity (i.e., indicating that there was a strong tendency to discharge), and switches to the first operating mode and operates when the minimum value of the remaining storage capacity SOC of the charging / discharging unit 9a during a second specified period in the past when it was operating in the second operating mode (an example of the above-mentioned charging / discharging history) is equal to or higher than a second remaining storage capacity that is larger than the first remaining storage capacity (i.e., indicating that there was a strong tendency to charge).

[0032] As a specific example, the charging / discharging device 9 switches to the second operating mode and operates when the highest SOC (maximum remaining amount of stored power) of the charging / discharging unit 9a during the past 24 hours (first specified period) while it was operating in the first operating mode is below the "lower discharge limit + 10%" of the charging / discharging unit 9a (i.e., indicating a large tendency to discharge), and switches to the first operating mode and operates when the lowest SOC (minimum value of remaining amount of stored power) of the charging / discharging unit 9a during the past 24 hours (second specified period) while it was operating in the second operating mode is above 80% (an example of a second remaining amount of stored power), which is greater than the first remaining amount of stored power.

[0033] [First operating mode] In the first operating mode, the charging / discharging device 9 adjusts the received power so that the power P3 flowing from the second connection point 5 to the third connection point 6 on the power line 2 becomes a predetermined second target power (for example, 700 W (maximum supply power of the fuel cell device 8)).

[0034] 1 is a diagram showing the state of the distributed power system when the charge / discharge device 9 is operating in a first operation mode, in which the charge / discharge device 9 is charging power. In the diagram, the magnitude (absolute value) of each power and an arrow indicating its direction are shown. As shown in the diagram, when the load power P4 of the power load device 3 is 500 W, the charge / discharge control unit 9c controls the received power P7 that the charge / discharge device 9 receives from the power line 2 to 200 W (i.e., a charging power of 200 W) so that the power P3, which is the sum of the load power P4 (500 W) of the power load device 3 and the received power P7 that the charge / discharge device 9 receives from the power line 2, becomes 700 W. At this time, the fuel cell control unit 8c of the fuel cell device 8 controls the supply power P6 from the fuel cell device 8 to the power line 2 to 700 W, thereby making the sum (700 W) of the load power P4 received by the power load device 3 from the power line 2 and the received power P7 received by the charging / discharging device 9 from the power line 2 equal to the supply power P6 (700 W) from the fuel cell device 8 to the power line 2. As a result, the power P2 measured by the power measurement unit 11 becomes zero. In addition, since all of the supply power P5 (500 W) of the solar cell device 7 is supplied to the power system 1, the power flowing from the first connection point 4 to the power system 1 is 500 W (reverse flow of 500 W), that is, the power P1 flowing from the power system 1 to the first connection point 4 is -500 W.

[0035] 2 is a diagram showing a state of the distributed power system when the charging / discharging device 9 is operating in the first operation mode, in which the charging / discharging device 9 is discharging power. As shown in the figure, when the load power P4 of the power load device 3 is 1500 W, the charging / discharging control unit 9c controls the power discharged by the charging / discharging device 9 to the power line 2 to 800 W, i.e., the received power P7 received by the charging / discharging device 9 from the power line 2 to -800 W, so that the sum of the load power P4 (1500 W) of the power load device 3 and the received power P7 received by the charging / discharging device 9 from the power line 2, that is, the sum of the load power P4 (1500 W) of the power load device 3 and the received power P7 received by the charging / discharging device 9 from the power line 2, becomes 700 W. At this time, the fuel cell control unit 8c of the fuel cell device 8 controls the supply power P6 from the fuel cell device 8 to the power line 2 to 700 W, thereby making the sum (700 W) of the load power P4 received by the power load device 3 from the power line 2 and the received power P7 received by the charging / discharging device 9 from the power line 2 equal to the supply power P6 (700 W) from the fuel cell device 8 to the power line 2. As a result, the power P2 measured by the power measurement unit 11 becomes zero. In addition, since all of the supply power P5 (500 W) of the solar cell device 7 is supplied to the power system 1, the power flowing from the first connection point 4 to the power system 1 is 500 W (reverse flow of 500 W), that is, the power P1 flowing from the power system 1 to the first connection point 4 is -500 W.

[0036] [Second operating mode] In the second operating mode, the charging / discharging device 9 derives a first provisional received power that the charging / discharging device 9 needs to receive from the third connection point 6 when the power P3 flowing from the second connection point 5 to the third connection point 6 on the power line 2 is set to a second target power (e.g., 700 W (maximum supply power of the fuel cell device 8)), and a second provisional received power that the charging / discharging device 9 needs to receive from the third connection point 6 when the power flowing from the power system 1 to the first connection point 4 is set to a predetermined third target power (e.g., 0 W). The charging / discharging device 9 then determines the larger of the first provisional received power and the second provisional received power as the received power P7.

[0037] FIG. 3 is a diagram showing the state of the distributed power system when the charge / discharge device 9 is operating in the second operation mode, and in this case, the charge / discharge device 9 is charging power. Although not shown, when the load power P4 of the power load device 3 is 500 W, the first temporary received power that the charge / discharge device 9 needs to receive from the third connection point 6 when the power P3 flowing from the second connection point 5 to the third connection point 6 in the power line 2 is set to the second target power (700 W (maximum supply power of the fuel cell device 8)) is 200 W (i.e., a charging power of 200 W). Also, as shown in FIG. 3, when the load power P4 of the power load device 3 is 500 W, the second temporary received power that the charge / discharge device 9 needs to receive from the third connection point 6 when the power P1 flowing from the power system 1 to the first connection point 4 is set to a predetermined third target power (0 W) is 700 W (i.e., a charging power of 700 W). In this case, the second provisional received power (700 W), which is the larger of the first provisional received power and the second provisional received power, is determined as the received power P7.

[0038] FIG. 4 is a diagram showing the state of the distributed power system when the charge / discharge device 9 is operating in the second operation mode, and in this case, the charge / discharge device 9 is charging power. Although not shown, when the load power P4 of the power load device 3 is 1500 W, the first temporary received power that the charge / discharge device 9 needs to receive from the third connection point 6 when the power P3 flowing from the second connection point 5 to the third connection point 6 on the power line 2 is set to the second target power (700 W (maximum supply power of the fuel cell device 8)) is -800 W (i.e., the power that the charge / discharge device 9 needs to discharge to the power line 2 is 800 W). Also, as shown in FIG. 4, when the load power P4 of the power load device 3 is 1500 W, the second temporary received power that the charge / discharge device 9 needs to receive from the third connection point 6 when the power P1 flowing from the power system 1 to the first connection point 4 is set to the predetermined third target power (0 W) is -300 W (i.e., the power that the charge / discharge device 9 needs to discharge to the power line 2 is 300 W). In this case, the charging / discharging device 9 determines the second provisional received power (−300 W), which is the larger of the first provisional received power and the second provisional received power, as the received power P7. That is, as shown in FIG 4, the power discharged by the charging / discharging device 9 to the power line 2 is adjusted to 300 W.

[0039] As described above, by adjusting the received power P7 of the charging / discharging device 9, it is possible to promote the reverse flow of the power generated by the solar cell device 7 and suppress the reverse flow of the power generated by the solar cell device 7. When the charging / discharging history of the charging / discharging unit 9a indicates that the tendency to charge is large, the charging / discharging device 9 operates in a first operation mode in which the received power P7 is adjusted so that the reverse flow of the power generated by the solar cell device 7 is promoted, and when the charging / discharging history of the charging / discharging unit 9a indicates that the tendency to discharge is large, the charging / discharging device 9 operates in a second operation mode in which the received power is adjusted so that the reverse flow of the power generated by the solar cell device 7 is suppressed. In other words, when the charging / discharging history of the charging / discharging unit 9a indicates that the tendency to charge is large, the reverse flow of the power generated by the solar cell device 7 is promoted, that is, the power generated by the solar cell device 7 is less likely to be used for the load power P4 of the power load device 3 and the charging of the charging / discharging device 9, so that the remaining amount of electricity stored in the charging / discharging unit 9a can be prevented from becoming too large. Furthermore, when the charge / discharge history of the charge / discharge unit 9a indicates a strong tendency toward discharge, the reverse flow of the generated power of the solar cell device 7 is suppressed, that is, the generated power of the solar cell device 7 is more easily utilized for the load power P4 of the power load device 3 and for charging the charge / discharge device 9, thereby preventing the remaining storage capacity of the charge / discharge unit 9a from becoming too small. In addition, it is possible to realize a device having the functions of the charge / discharge device 9 used in a distributed power supply system (that is, a charge / discharge device).

[0040] <Second embodiment> The distributed power system of the second embodiment is different from the above-mentioned embodiment in the contents of the first operation mode and the second operation mode of the charge / discharge device 9. The distributed power system of the second embodiment will be described below, but the description of the same configuration as the above-mentioned embodiment will be omitted.

[0041] 5 to 8 are diagrams showing the configuration of a distributed power supply system according to the second embodiment. Information on the power P5 measured by the power measuring unit 13 is transmitted to the charge / discharge control unit 9c. In this embodiment, the power measuring unit 13 is provided between the solar cell device 7 and the first connection point 4 of the power line 2, and measures the power P5 flowing from the solar cell device 7 to the first connection point 4. The power measuring unit 13 is configured using, for example, a current transformer (instrument current transformer) used to detect the current value of the power, and can derive the power value from the product of the current value and a predetermined voltage value (for example, 100V, 200V, etc.). Note that the power measuring unit 13 may transmit only the current value of the power to the charge / discharge control unit 9c, and the charge / discharge control unit 9c may derive the power value. Then, the charge / discharge control unit 9c controls the received power P7 that the charge / discharge device 9 receives from the power line 2 by referring to the measurement result of the power measuring unit 13.

[0042] Information on the power P6 measured by the power measuring unit 14 is transmitted to the charge / discharge control unit 9c. In this embodiment, the power measuring unit 14 is provided between the fuel cell device 8 and the second connection point 5 of the power line 2, and measures the power P6 flowing from the fuel cell device 8 to the second connection point 5. The power measuring unit 14 is configured using, for example, a current transformer (instrument current transformer) used to detect the current value of the power, and can derive the power value from the product of the current value and a predetermined voltage value (for example, 100V, 200V, etc.). The power measuring unit 14 may transmit only the current value of the power to the charge / discharge control unit 9c, and the charge / discharge control unit 9c may derive the power value. Then, the charge / discharge control unit 9c controls the received power P7 that the charge / discharge device 9 receives from the power line 2 by referring to the measurement result of the power measuring unit 14.

[0043] [First operating mode] In the first operating mode, the charge / discharge device 9 adjusts the received power P7 so that the power P3 flowing from the second connection point 5 to the third connection point 6 on the power line 2 becomes greater than the supply power P6 of the fuel cell device 8 by a set power.

[0044] Although not shown in the figures, for example, when the supply power P6 of the fuel cell device 8 is 500 W, the charge / discharge control unit 9c adjusts the received power P7 so that the power P3 flowing from the second connection point 5 to the third connection point 6 becomes 600 W, which is 100 W (an example of the set power) greater than the supply power P6. When such an adjustment is made, the power P2 flowing from the first connection point 4 to the second connection point 5 becomes 100 W, so the fuel cell device 8 increases the supply power P6 so that the power P2 becomes 0 W. In this way, the charge / discharge device 9 continues to adjust the received power P7 so that the power P3 flowing from the second connection point 5 to the third connection point 6 on the power line 2 becomes greater than the supply power P6 of the fuel cell device 8 by the set power, and the supply power P6 of the fuel cell device 8 finally reaches its maximum supply power. Furthermore, in order to prevent the power P1 supplied from the power system 1 to the first connection point 4, i.e., the received power from the power system 1, from becoming large, the charging / discharging device 9 may set the upper limit value of the power P3 to the maximum supply power of the fuel cell device 8 (e.g., 700 W).

[0045] 5 is a diagram showing the state of the distributed power system when the charge / discharge device 9 is operating in the first operation mode, and in this case, the charge / discharge device 9 is charging power. As shown in the figure, when the load power P4 of the power load device 3 is 500 W, the charge / discharge control unit 9c adjusts the received power P7 that the charge / discharge device 9 receives from the power line 2, so that the power P3 going from the second connection point 5 to the third connection point 6, that is, the power P3 which is the sum of the load power P4 (500 W) of the power load device 3 and the received power P7 that the charge / discharge device 9 receives from the power line 2, is the maximum supply power (700 W) of the fuel cell device 8 which is set as the upper limit value of the power P3. In this case, the received power P7 that the charge / discharge device 9 receives from the power line 2 is 200 W. That is, the charge / discharge device 9 is charging 200 W from the power line 2. The fuel cell control unit 8c of the fuel cell device 8 controls the supply power P6 from the fuel cell device 8 to the power line 2 to 700 W, so the power P2 flowing from the first connection point 4 to the second connection point 5 is 0 W. And, because all of the supply power P5 (500 W) of the solar cell device 7 is supplied to the power grid 1, the power flowing from the first connection point 4 to the power grid 1 is 500 W (reverse flow of 500 W), that is, the power P1 flowing from the power grid 1 to the first connection point 4 is -500 W.

[0046] 6 is a diagram showing the state of the distributed power system when the charge / discharge device 9 is operating in the first operation mode, in which the charge / discharge device 9 is discharging power. As shown in the figure, when the load power P4 of the power load device 3 is 1500 W, the charge / discharge control unit 9c adjusts the received power P7 that the charge / discharge device 9 receives from the power line 2, so that the power P3 going from the second connection point 5 to the third connection point 6, i.e., the sum of the load power P4 (1500 W) of the power load device 3 and the received power P7 that the charge / discharge device 9 receives from the power line 2, is the maximum supply power (700 W) of the fuel cell device 8 set to the upper limit value of the power P3. In this case, the power that the charge / discharge device 9 discharges to the power line 2 is 800 W, i.e., the received power P7 that the charge / discharge device 9 receives from the power line 2 is -800 W. The fuel cell control unit 8c of the fuel cell device 8 controls the supply power P6 from the fuel cell device 8 to the power line 2 to 700 W, so the power P2 flowing from the first connection point 4 to the second connection point 5 is 0 W. And, because all of the supply power P5 (500 W) of the solar cell device 7 is supplied to the power grid 1, the power flowing from the first connection point 4 to the power grid 1 is 500 W (reverse flow of 500 W), that is, the power P1 flowing from the power grid 1 to the first connection point 4 is -500 W.

[0047] [Second operating mode] In the second operating mode, the charging / discharging device 9 adjusts the received power P7 so that the power P3 flowing from the second connection point 5 to the third connection point 6 on the power line 2 becomes a value obtained by adding the power P5 supplied by the solar cell device 7 to the first connection point 4 to a power that is a set power greater than the supply power P6 of the fuel cell device 8.

[0048] Although not shown in the figures, for example, when the supply power P6 of the fuel cell device 8 is 500 W and the power P5 supplied by the solar cell device 7 to the first connection point 4 is 500 W, the charge / discharge control unit 9c adjusts the received power P7 so that the power P3 flowing from the second connection point 5 to the third connection point 6 becomes 1100 W, which is the sum of 600 W, which is 100 W (an example of the set power) greater than the supply power P6, and the 500 W supplied by the solar cell device 7 to the first connection point 4. When such an adjustment is made, the power P2 flowing from the first connection point 4 to the second connection point 5 becomes 600 W, so the fuel cell device 8 increases the supply power P6 so as to make the power P2 0 W. In this way, the charger / discharger 9 continues to adjust the received power P7 so that the power P3 flowing from the second connection point 5 to the third connection point 6 on the power line 2 becomes a value obtained by adding the power P5 supplied by the solar cell device 7 to the first connection point 4 to a power that is larger than the supply power P6 of the fuel cell device 8 by a set power, and the supply power P6 of the fuel cell device 8 finally reaches its maximum supply power. Note that, in order to prevent the power P1 supplied from the power system 1 to the first connection point 4, i.e., the received power from the power system 1, from becoming large, the charger / discharger 9 may set the upper limit value of the power P3 to a value obtained by adding the maximum supply power (e.g., 700 W) of the fuel cell device 8 to the power P5 supplied by the solar cell device 7 to the first connection point 4. In other words, when the power P5 supplied by the solar cell device 7 to the first connection point 4 is 500 W, the charger / discharger 9 sets the upper limit value of the power P3 to 1200 W.

[0049] FIG. 7 is a diagram showing the state of the distributed power system when the charge / discharge device 9 is operating in the second operation mode, and in this case, the charge / discharge device 9 is charging power. As shown in the figure, when the load power P4 of the power load device 3 is 500 W, the charge / discharge control unit 9c adjusts the received power P7 that the charge / discharge device 9 receives from the power line 2, so that the power P3 going from the second connection point 5 to the third connection point 6, that is, the sum of the load power P4 (500 W) of the power load device 3 and the received power P7 that the charge / discharge device 9 receives from the power line 2, is 1200 W, which is the upper limit value of the power P3 (i.e., the maximum supply power (700 W) of the fuel cell device 8 plus 500 W, which is the power P5 that the solar cell device 7 supplies to the first connection point 4). In this case, the received power P7 that the charge / discharge device 9 receives from the power line 2 is 700 W. That is, the charge / discharge device 9 is charging 700 W from the power line 2. The fuel cell control unit 8c of the fuel cell device 8 controls the supply power P6 from the fuel cell device 8 to the power line 2 to 700 W, so the power P2 flowing from the first connection point 4 to the second connection point 5 is 500 W. All of the supply power P5 (500 W) of the solar cell device 7 is supplied to the second connection point 5. The power P1 flowing from the power system 1 to the first connection point 4 is 0 W.

[0050] FIG. 8 is a diagram showing the state of the distributed power system when the charge / discharge device 9 is operating in the second operation mode, and in this case, the charge / discharge device 9 is charging power. As shown in the figure, when the load power P4 of the power load device 3 is 1500 W, the charge / discharge control unit 9c adjusts the received power P7 that the charge / discharge device 9 receives from the power line 2, so that the power P3 going from the second connection point 5 to the third connection point 6, i.e., the sum of the load power P4 (1500 W) of the power load device 3 and the received power P7 that the charge / discharge device 9 receives from the power line 2, is 1200 W, which is the upper limit value of the power P3 (i.e., the maximum supply power (700 W) of the fuel cell device 8 plus 500 W, which is the power P5 that the solar cell device 7 supplies to the first connection point 4). In this case, the power that the charge / discharge device 9 discharges to the power line 2 is 300 W, i.e., the received power P7 that the charge / discharge device 9 receives from the power line 2 is -300 W. The fuel cell control unit 8c of the fuel cell device 8 controls the supply power P6 from the fuel cell device 8 to the power line 2 to 700 W, so the power P2 flowing from the first connection point 4 to the second connection point 5 is 500 W. All of the supply power P5 (500 W) of the solar cell device 7 is supplied to the second connection point 5. The power P1 flowing from the power system 1 to the first connection point 4 is 0 W.

[0051] <Another embodiment> <1> In the above embodiment, specific examples of the configurations of the distributed power supply system and the charge / discharge device of the present invention have been given and explained, but the configurations can be changed as appropriate. For example, the configurations of the fuel cell device 8 and the charge / discharge device 9 are not limited to those shown in the drawings and can be modified as appropriate.

[0052] In the above embodiment, the fuel cell device 8 is given as an example of the power generating device of the present invention, but various other power generating devices that can freely adjust the output within a range between a predetermined minimum and maximum power to be provided can be used. For example, a power generating device that includes an engine and a generator driven by the engine can be used.

[0053] <2> In the above embodiment, the criteria by which the charging / discharging device 9 switches between the first operation mode and the second operation mode can be changed as appropriate. For example, the charging / discharging device 9 may switch to the second operation mode and operate when the total amount of discharged power from the charging / discharging unit 9a during the past first predetermined period when the device was operating in the first operation mode is equal to or larger than the first discharged power amount or the total amount of charged power to the charging / discharging unit 9a is equal to or smaller than the first charged power amount (i.e., when the charging / discharging history indicates that the tendency to discharge was large or the tendency to charge was small), and may switch to the first operation mode and operate when the total amount of discharged power from the charging / discharging unit 9a during the past second predetermined period when the device was operating in the second operation mode is equal to or smaller than the second discharged power amount or the total amount of charged power to the charging / discharging unit 9a is equal to or larger than the second charged power amount (i.e., when the charging / discharging history indicates that the tendency to charge was large or the tendency to discharge was small). For example, when the first predetermined period and the second predetermined period are the same length, the first discharged power amount is a value larger than the second discharged power amount, and the first charged power amount is a value smaller than the second charged power amount.

[0054] <3> In the above embodiment, the distributed power system and the charge / discharge device of the present invention are described using specific power values ​​as examples, but these are described for illustrative purposes and can be changed as appropriate.

[0055] <4> In addition, the configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, provided no contradiction arises. Furthermore, the embodiments disclosed in this specification are illustrative, and the embodiments of the present invention are not limited thereto, and can be appropriately modified within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0056] INDUSTRIAL APPLICABILITY The present invention can be used in a distributed power system and a charge / discharge device that can switch between a state that promotes reverse power flow of power generated by a solar cell device and a state that suppresses reverse power flow. [Explanation of symbols]

[0057] 1 Power system 2. Power Lines 3 Power load device 4 First connection point 5 Second connection point 6 Third connection point 7 Solar cell device 8. Fuel cell equipment (power generation equipment) 8a Fuel cell section 9 Charge / discharge device 9a Charge / discharge section

Claims

1. The power system includes a power line connected to a power grid, a solar cell device, a power generation device, and a charging / discharging device having a charging / discharging unit, a connection point to the power grid is provided on an upstream side of the power line, and a first connection point, a second connection point, and a third connection point are provided in this order on the power line from the connection point to the power grid toward a downstream side; a power load device connected to the third connection point, a solar cell device connected to the first connection point, a power generation device connected to the second connection point, and a charging / discharging device connected to the third connection point; When the charging power from the third connection point by the charging / discharging device is regarded as positive received power, and the discharging power to the third connection point by the charging / discharging device is regarded as negative received power, the power generation device adjusts the supply power supplied to the second connection point within a range between maximum supply power and minimum supply power so as to follow the sum of the load power received by the power load device from the third connection point and the received power received by the charging / discharging device from the third connection point; A distributed power supply system in which the charging / discharging device switches to a first operating mode in which the received power is adjusted in a range between maximum received power and minimum received power so as to promote reverse flow of power generated by the solar cell device when the charging / discharging history of the charging / discharging unit indicates that there was a strong tendency to charge, and switches to a second operating mode in which the received power is adjusted in a range between maximum received power and minimum received power so as to suppress reverse flow of power generated by the solar cell device when the charging / discharging history of the charging / discharging unit indicates that there was a strong tendency to discharge.

2. The charging / discharging device is In the first operation mode, the received power is adjusted so that the power flowing from the second connection point to the third connection point in the power line becomes a predetermined second target power; 2. The distributed power system according to claim 1, wherein, in the second operating mode, a first provisional received power that the charging / discharging device needs to receive from the third connection point when power flowing from the second connection point to the third connection point on the power line is set to the second target power, and a second provisional received power that the charging / discharging device needs to receive from the third connection point when power flowing from the power system to the first connection point is set to a predetermined third target power are derived, and the larger of the first provisional received power and the second provisional received power is determined to be the received power.

3. The charging / discharging device is In the first operation mode, the received power is adjusted so that the power flowing from the second connection point to the third connection point in the power line is greater than the generated power of the power generation device by a set power. A distributed power system as described in claim 1, wherein, in the second operating mode, the received power is adjusted so that the power flowing from the second connection point to the third connection point on the power line is a value obtained by adding the power generated by the power generation device to the power supplied by the solar cell device to the first connection point, the received power being greater than the set power by the power generation device.

4. The charging / discharging device is When a maximum value of a remaining charge amount of the charge / discharge unit during a past first predetermined period in which the charge / discharge unit was operating in the first operation mode is equal to or smaller than a first remaining charge amount, the charge / discharge unit switches to the second operation mode and operates in the second operation mode; A distributed power system as described in any one of claims 1 to 3, wherein when the minimum value of the remaining charge of the charge / discharge unit during a past second predetermined period when the charge / discharge unit was operating in the second operating mode is equal to or greater than a second remaining charge that is greater than the first remaining charge.

5. The charging / discharging device is When a total amount of discharged power from the charge / discharge unit during a past first predetermined period in which the device was operating in the first operation mode is equal to or greater than a first discharge amount of power or when a total amount of charged power to the charge / discharge unit is equal to or less than a first charge amount of power, the device switches to the second operation mode and operates in the second operation mode; The distributed power system according to any one of claims 1 to 3, wherein the system switches to the first operating mode and operates when the total amount of discharged power from the charge / discharge unit during a past second predetermined period in which the system was operating in the second operating mode is equal to or less than a second discharged power amount or when the total amount of charged power to the charge / discharge unit is equal to or more than a second charged power amount.

6. A charge / discharge device having the functions of the charge / discharge device used in the distributed power supply system according to any one of claims 1 to 5.

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