Power distribution system and power distribution method

Abstract

To provide a technique that enables interchange of power in a large system in which a plurality of power generators and power storage devices are connected.SOLUTION: When a voltage of a first DC bus (19) is within a first range, a first DC cluster (1) outputs a discharge request via a switching circuit (18) and a DC grid (4). Also, when a voltage of a second DC bus (29) is within a second range, a second DC cluster (2) supplies power to the first DC cluster (1) via a switching circuit (28) and the DC grid (4) in response to the discharge request from the first DC cluster (1).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a power distribution system and a power distribution method.

Background Art

[0002] In recent years, systems in which power generation devices, charging devices, loads, etc. are connected to a DC circuit have been developed. As a related technology, there is an invention disclosed in Patent Document 1 below.

[0003] Patent Document 1 discloses an energy system including a plurality of devices, a DC circuit, and a control device. The plurality of devices include a first power generation device, a first output device, and a second output device. The first power generation device supplies power to the DC circuit. The first output device extracts power from the DC circuit and outputs it toward the grid power supply. The second output device extracts power from the DC circuit and outputs it toward the load. The control device switches the operating states of the plurality of devices based on which voltage category among a plurality of voltage categories corresponding to the voltage level the voltage of the DC circuit belongs to.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Patent Document 1, the control device switches the operating states of the plurality of devices based on which voltage category among a plurality of voltage categories corresponding to the voltage level the voltage of the DC circuit belongs to. However, Patent Document 1 cannot cope with a large-scale system in which a plurality of energy systems disclosed in Patent Document 1 are connected.

[0006] One aspect of the present invention aims to provide a technology that enables power sharing in a large-scale system to which a plurality of power generation devices and energy storage devices are connected.

Means for Solving the Problems

[0007] In order to solve the above problems, a power distribution system according to one aspect of the present invention is a power distribution system in which a plurality of DC clusters are connected via a DC grid. The first DC cluster includes at least a first power generation device, a first energy storage device, a first load, a first DC bus, and a first switching circuit. Each of the first power generation device and the first energy storage device is connected to the first DC bus via a power converter, and the first DC bus is connected to the DC grid via the first switching circuit. The second DC cluster includes at least a second power generation device, a second energy storage device, a second load, a second DC bus, and a second switching circuit. Each of the second power generation device and the second energy storage device is connected to the second DC bus via a power converter, and the second DC bus is connected to the DC grid via the second switching circuit. The power converter to which the first energy storage device is connected connects the first switching circuit and outputs a discharge request via the DC grid when the voltage of the first DC bus is within a first range with the first switching circuit disconnected. The power converter to which the second energy storage device is connected connects the second switching circuit and supplies power to the first DC cluster via the DC grid in response to the discharge request from the first DC cluster when the voltage of the second DC bus is within a second range exceeding the first range with the second switching circuit disconnected.

[0008] In order to solve the above problems, a power distribution method according to an aspect of the present invention is a power distribution method for a power distribution system in which a plurality of DC clusters are connected via a DC grid. The first DC cluster includes at least a first power generation device, a first energy storage device, a first load, a first DC bus, and a first switching circuit. Each of the first power generation device and the first energy storage device is connected to the first DC bus via a power converter, and the first DC bus is connected to the DC grid via the first switching circuit. The second DC cluster includes at least a second power generation device, a second energy storage device, a second load, a second DC bus, and a second switching circuit. Each of the second power generation device and the second energy storage device is connected to the second DC bus via a power converter, and the second DC bus is connected to the DC grid via the second switching circuit. When the voltage of the first DC bus is within a first range in a state where the first switching circuit is disconnected, the power converter to which the first energy storage device is connected connects the first switching circuit and outputs a discharge request via the DC grid. When the voltage of the second DC bus is within a second range exceeding the first range in a state where the second switching circuit is disconnected, the power converter to which the second energy storage device is connected connects the second switching circuit in response to the discharge request from the first DC cluster and supplies power to the first DC cluster via the DC grid.

Advantages of the Invention

[0009] According to one aspect of the present invention, it is possible to provide a technology that enables power sharing in a large-scale system in which a plurality of power generation devices and energy storage devices are connected.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0011] <Configuration Example of a Power Distribution System> FIG. 1 is a block diagram showing a configuration example of a power distribution system 100 according to an embodiment of the present invention. As shown in FIG. 1, the power distribution system 100 includes a first DC cluster 1, a second DC cluster 2, and a third DC cluster 3, each of which is connected via a DC grid 4. Note that in FIG. 1, three DC clusters are shown, but the number of DC clusters is not limited to this.

[0012] The first DC cluster 1 includes a power storage device (Batt) 11, a fuel cell (FC) 12, a power generation device (PV) 13, an electric vehicle (EV) 14 which is an example of a load, power converters (DC / DC) 15-1 to 15-4, switches 16-1 to 16-4, a voltage / current sensor 17, a switch (switching circuit) 18, and a first DC bus 19. The power converters 15-1 to 15-4 have DC / DC converters and control the DC / DC converters, the switch (switching circuit) 18, etc. while referring to the voltage of the first DC bus 19 and the voltage of the DC grid 4. Hereinafter, the case where each of the power converters 15-1 to 15-4 operates autonomously will be described. However, for example, the first DC cluster 1 may have a control unit, and the control unit may control the power converters 15-1 to 15-4, the switch (switching circuit) 18, etc. while referring to the voltage of the first DC bus 19 and the voltage of the DC grid 4.

[0013] The energy storage device (Batt) 11 is connected to the first DC bus 19 via the power converter 15-1 and the switch 16-1. The power converter 15-1 has a bidirectional DC / DC converter. When charging the energy storage device 11, it converts the voltage of the first DC bus 19 to a predetermined voltage and supplies it to the energy storage device 11. Also, when the energy storage device 11 discharges, the power converter 15-1 converts the voltage output from the energy storage device 11 to a predetermined voltage and supplies it to the first DC bus 19 via the switch 16-1. Further, the power converter 15-1 controls the switch 16-1 to switch the connection / disconnection with the first DC bus 19.

[0014] The fuel cell (FC) 12 is, for example, a battery that uses hydrogen as fuel, and is connected to the first DC bus 19 via the power converter 15-2 and the switch 16-2. The power converter 15-2 converts the voltage output from the fuel cell (FC) 12 to a predetermined voltage and supplies it to the first DC bus 19 via the switch 16-2. Also, the power converter 15-2 controls the switch 16-2 to switch the connection / disconnection with the first DC bus 19.

[0015] The power generation device (PV) 13 is, for example, a power generation device having a solar cell that generates electricity by sunlight, and is connected to the first DC bus 19 via the power converter 15-3 and the switch 16-3. The power converter 15-3 converts the voltage output from the power generation device (PV) 13 to a predetermined voltage and supplies it to the first DC bus 19 via the switch 16-3. Also, the power converter 15-3 controls the switch 16-3 to switch the connection / disconnection with the first DC bus 19. Note that the power generation device (PV) 13 is not limited to solar power generation, and may be wind power generation, geothermal power generation, etc.

[0016] The electric vehicle (EV) 14 is an example of a load, and is connected to the first DC bus 19 via the power converter 15-4 and the switch 16-4. The power converter 15-4 converts the voltage of the first DC bus 19 to a predetermined voltage and supplies it to the electric vehicle (EV) 14. Also, the power converter 15-4 controls the switch 16-4 to switch the connection / disconnection with the first DC bus 19.

[0017] The voltage / current sensor 17 measures the voltage and current of the DC grid 4, and outputs the voltage value and current value of the DC grid 4 to the power converter 15-1 to which the power storage device (Batt) 11 is connected and the power converter 15-3 to which the power generation device (PV) 13 is connected.

[0018] The switch (switching circuit) 18 switches the connection / disconnection between the DC grid 4 and the first DC bus 19 according to an instruction from the power converter 15-1 to which the power storage device (Batt) 11 is connected.

[0019] Further, the second DC cluster 2 includes a power storage device (Batt) 21, a fuel cell (FC) 22, a power generation device (PV) 23, an electric vehicle (EV) 24 which is an example of a load, power converters 25-1 to 25-4, switches 26-1 to 26-4, a voltage / current sensor 27, a switch 28, and a second DC bus 29. Note that since the operation of the second DC cluster 2 is the same as that of the first DC cluster 1, detailed description thereof will not be given here.

[0020] Further, the third DC cluster 3 includes a power storage device (Batt) 31, a fuel cell (FC) 32, a power generation device (PV) 33, an electric vehicle (EV) 34 which is an example of a load, power converters 35-1 to 35-4, switches 36-1 to 36-4, a voltage / current sensor 37, a switch 38, and a third DC bus 39. Note that since the operation of the third DC cluster 3 is the same as that of the first DC cluster 1, detailed description thereof will not be given here.

[0021] <Operation classification of the DC cluster> FIG. 2 is a diagram for explaining the operation classification of the DC cluster. In FIG. 2, the vertical axis represents the voltage of the DC bus (DC grid). Hereinafter, the case where the DC cluster is the first DC cluster 1 will be described, but the operations of the second DC cluster 2 and the third DC cluster 3 are the same.

[0022] The power converters 15-1 to 15-4 monitor the voltage and current of the first DC bus 19 and operate according to the voltage of the first DC bus 19. When the voltage of the first DC bus 19 is 0 to V1 (all OFF), the power converters 15-1 to 15-4 control the switches 16-1 to 16-4 to disconnect the connection with the first DC bus 19. In this state, all of the switches 16-1 to 16-4 are OFF.

[0023] When the voltage of the first DC bus 19 is V1 to V2 (the first range), the power converter 15-1 to which the energy storage device 11 is connected performs the operation of cluster power sharing charging. The details of the operation of cluster power sharing charging will be described later. At this time, the power converter 15-2 connects the switch 16-2 to supply the power from the fuel cell (FC) 12 to the first DC bus 19. Also, the power generation device (PV) 13 performs MPPT (Maximum Power Point Tracking) control, and the power converter 15-3 connects the switch 16-3 to supply the power from the power generation device (PV) 13 to the first DC bus 19. Also, the power converter 15-4 disconnects the switch 16-4 to stop the power supply to the electric vehicle (EV) 14.

[0024] When the voltage of the first DC bus 19 is V2 to V3, the power converter 15-1 connects the switch 16-1 to discharge the energy storage device 11 (battery discharge). At this time, the power converter 15-2 disconnects the switch 16-2 to stop the power supply from the fuel cell (FC) 12. Also, the power generation device (PV) 13 performs MPPT control, and the power converter 15-3 connects the switch 16-3 to supply the power from the power generation device (PV) 13 to the first DC bus 19. Also, the power converter 15-4 disconnects the switch 16-4 to stop the power supply to the electric vehicle (EV) 14.

[0025] When the voltage of the first DC bus 19 is between V3 and V4, the power converter 15-1 disconnects the switch 16-1 to disconnect the connection to the power storage device 11 (battery OFF). At this time, the power converter 15-2 disconnects the switch 16-2 to stop the power supply from the fuel cell (FC) 12. Also, the power generation device (PV) 13 performs MPPT control, and the power converter 15-3 connects the switch 16-3 to supply the power from the power generation device (PV) 13 to the first DC bus 19. Further, the power converter 15-4 disconnects the switch 16-4 to stop the power supply to the electric vehicle (EV) 14.

[0026] When the voltage of the first DC bus 19 is between V4 and V5, the power converter 15-1 connects the switch 16-1 to charge the power storage device 11 (battery charging). At this time, the power converter 15-2 disconnects the switch 16-2 to stop the power supply from the fuel cell (FC) 12. Also, the power generation device (PV) 13 performs MPPT control, and the power converter 15-3 connects the switch 16-3 to supply the power from the power generation device (PV) 13 to the first DC bus 19. Further, the power converter 15-4 disconnects the switch 16-4 to stop the power supply to the electric vehicle (EV) 14.

[0027] When the voltage of the first DC bus 19 is between V5 and V6, the power converter 15-1 connects the switch 16-1 to charge the power storage device 11. At this time, the power converter 15-2 disconnects the switch 16-2 to stop the power supply from the fuel cell (FC) 12. Also, the power generation device (PV) 13 performs MPPT control, and the power converter 15-3 connects the switch 16-3 to supply the power from the power generation device (PV) 13 to the first DC bus 19. Further, the power converter 15-4 connects the switch 16-4 to supply the power to the electric vehicle (EV) 14.

[0028] When the voltage of the first DC bus 19 is in the range of V6 to V7 (the second range), the power converter 15-1 performs the operation of cluster bridging discharge. The details of the cluster bridging discharge operation will be described later. At this time, the power converter 15-2 disconnects the switch 16-2 to stop the power supply from the fuel cell (FC) 12. Also, the power generation device (PV) 13 performs constant voltage control, and the power converter 15-3 connects the switch 16-3 to supply the power from the power generation device (PV) 13 to the first DC bus 19. Further, the power converter 15-4 connects the switch 16-4 to supply power to the electric vehicle (EV) 14. Note that the second range includes the case where the voltage of the first DC bus 19 is in the range of V7 to V8.

[0029] When the voltage of the first DC bus 19 is in the range of V7 to V8 (the third range), the power converter 15-1 performs the operation of cluster bridging discharge. The details of the cluster bridging discharge operation will be described later. At this time, the power converter 15-2 disconnects the switch 16-2 to stop the power supply from the fuel cell (FC) 12. Also, the power converter 15-3 disconnects the switch 16-3 to stop the power supply from the power generation device (PV) 13 (PV priority OFF). Further, the power converter 15-4 connects the switch 16-4 to supply power to the electric vehicle (EV) 14.

[0030] When the voltage of the first DC bus 19 is in the range of V8 to V9 (the fourth range), the power converters 15-1 to 15-4 control the switches 16-1 to 16-4 to disconnect the connection to the first DC bus 19. In this state, all of the switches 16-1 to 16-4 are turned OFF.

[0031] <Charge and Discharge between DC Clusters> FIG. 3 is a diagram for explaining charge and discharge between DC clusters. In FIG. 3, a case where the first DC cluster 1 is on the charging side and the second DC cluster 2 is on the discharging side is shown. When the voltage of the first DC bus 19 is within the range of cluster interconnection charging (V1 to V2), the power converter 15-1 of the first DC cluster 1 performs operations according to a predetermined processing procedure, and then connects switches 16-1 and 18 to receive power supply from the second DC cluster 2 and charge the energy storage device (Batt) 11.

[0032] Also, when the voltage of the second DC bus 29 is within the range of cluster interconnection discharging (V6 to V8), the power converter 25-1 of the second DC cluster 2 performs operations according to a predetermined processing procedure, and then connects switches 26-1 and 28 to supply power to the first DC cluster 1.

[0033] FIG. 4 is a diagram for explaining the operation classification of the first DC cluster 1 on the charging side and the second DC cluster 2 on the discharging side. As shown in the left diagram of FIG. 4, when the voltage of the first DC bus 19 is within the range of cluster interconnection charging (V1 to V2), the power converter 15-1 of the first DC cluster 1 connects switch 18 and outputs a discharge request by setting the voltage of the DC grid 4 to the voltage of the first DC bus 19. The first DC cluster 1 maintains this state and waits for the second DC cluster 2 on the discharging side to start power supply after the second DC cluster 2 on the discharging side performs operations according to a predetermined processing procedure.

[0034] As shown in the right diagram of FIG. 4, when the voltage of the second DC bus 29 is within the range of cluster interconnection discharging (V6 to V8) and there is a discharge request from the first DC cluster 1, the power converter 25-1 of the second DC cluster 2 raises the voltage of the second DC bus 29 until it is within the range of PV priority OFF (V7 to V8). At this time, the power converter 25-3 disconnects switch 26-3 to stop the power supply from the power generation device (PV) 23.

[0035] Next, the power converter 25-1 of the second DC cluster 2 lowers the voltage of the second DC bus 29 until it becomes the same as the voltage of the DC grid 4, and then connects the switch 28 to start power supply to the first DC cluster 1. Due to the power supply of the second DC cluster 2, the voltage of the DC grid 4 gradually rises, and as shown in FIG. 4, the voltage of the DC grid 4 becomes the DC grid voltage during power sharing between clusters.

[0036] When power sharing is performed between DC clusters, the power converter 15-1 of the first DC cluster 1 on the charging side does not perform the operation according to the operation mode, but continues to perform the charging operation of the energy storage device (Batt) 11. Similarly, when power sharing is performed between DC clusters, the power converter 25-1 of the second DC cluster 2 on the discharging side does not perform the operation according to the operation mode, but continues to perform the discharging operation of the energy storage device (Batt) 21.

[0037] <Processing procedures of DC clusters 1 to 3> FIG. 5 is a flowchart for explaining the overall operation of each DC cluster. First, DC clusters 1 to 3 measure the voltage of the DC bus within their own cluster, and determine whether the voltage of the DC bus is within the range of cluster power sharing discharge (V6 to V8) (S11).

[0038] If the voltage of the DC bus of DC clusters 1 to 3 is within the range of cluster power sharing discharge (S11, Yes), they perform the processing of "possible" inter-cluster discharge shown in FIG. 7 (S12). Also, if the voltage of the DC bus of DC clusters 1 to 3 is not within the range of cluster power sharing discharge (S11, No), they determine whether the voltage of the DC bus is within the range of cluster power sharing charge (V1 to V2) (S13).

[0039] If the voltage of the DC bus of DC clusters 1 to 3 is within the range of cluster power sharing charge (S13, Yes), they perform the processing of "requested" inter-cluster discharge shown in FIG. 6 (S14). Also, if the voltage of the DC bus of DC clusters 1 to 3 is not within the range of cluster power sharing charge (S13, No), they perform the processing according to the operation mode (charging / OFF / discharging of the energy storage device) of V2 to V6 shown in FIG. 2 (S15).

[0040] FIG. 6 is a flowchart for explaining the operation of the charging-side DC cluster (inter-cluster discharge "request"). Note that the case where the charging-side DC cluster is the first DC cluster 1 will be described, but the same operation is assumed to be performed even if the charging-side DC cluster is the second DC cluster 2 or the third DC cluster 3.

[0041] First, the power converter 15-1 of the first DC cluster 1 acquires the voltage of the DC grid 4 from the voltage / current sensor 17, and determines whether a voltage (V1 to V2) is applied across the clusters (DC grid 4) (S21). If a voltage is applied to the DC grid 4 (S21, Yes), it is assumed that another DC cluster has output a discharge request, and the process returns to the "startup" operation shown in FIG. 5 (S22). Note that the operation of cluster-to-cluster charging can be performed by only one DC cluster within the power distribution system 100.

[0042] If no voltage is applied to the DC grid 4 (S21, No), the power converter 15-1 turns on the switch 18 for a certain period of time to connect the first DC bus 19 and the DC grid 4, and outputs a discharge request to other DC clusters (S23).

[0043] Next, the power converter 15-1 acquires the current of the DC grid 4 from the voltage / current sensor 17, and determines whether the power storage device (Batt) 11 is being charged based on the direction of the current (S24).

[0044] If the power converter 15-1 determines that the power storage device (Batt) 11 is not being charged (S24, No), it determines that power supply from other DC clusters is not possible, turns off the switch 18 (S25), and returns to the "startup" operation shown in FIG. 5 (S26).

[0045] If the power converter 15-1 determines that the power storage device (Batt) 11 is being charged (S24, Yes), it determines whether the voltage of the first DC bus 19 (intra-cluster voltage) is within the range of V8 to V9 (all OFF) (S27).

[0046] If the voltage of the first DC bus 19 is within the range of V8 to V9 (all OFF) (S27, Yes), assuming that there is a notice of cluster power sharing discharge stop from the DC cluster on the discharge side, the power converters 15-1 to 15-4 control the switches 16-1 to 16-4 to disconnect the connection with the first DC bus 19. Then, the power converter 15-1 turns off the switch 18 (S25) and returns to the "startup" operation shown in FIG. 5 (S26).

[0047] Also, if the voltage of the first DC bus 19 is not within the range of V8 to V9 (all OFF) (S27, No), the power converter 15-1 detects the SOC (State Of Charge) of the energy storage device (Batt) 11, determines whether the SOC (charge amount) is equal to or greater than a first predetermined value, and judges whether charging is still required (S28).

[0048] If the power converter 15-1 determines that charging of the energy storage device (Batt) 11 is still required (SOC is less than the first predetermined value) (S28, Yes), it returns to step S24 and repeats the subsequent processing. Also, if the power converter 15-1 determines that charging of the energy storage device (Batt) 11 is no longer required (SOC is equal to or greater than the first predetermined value) (S28, No), it raises the voltage of the first DC bus 19 to within the range of V8 to V9 (all OFF) (S29) and outputs a discharge stop request to the DC cluster on the discharge side. Note that multiple DC clusters on the discharge side are also allowed.

[0049] Next, the power converters 15-1 to 15-4 control the switches 16-1 to 16-4 to disconnect the connection with the first DC bus 19. Then, the power converter 15-1 confirms that the voltage of the first DC bus 19 is 0V, turns off the switch 18 (S30), and returns to the "startup" operation shown in FIG. 5 (S31).

[0050] FIG. 7 is a flowchart for explaining the operation of the DC cluster on the discharge side (cluster-to-cluster discharge "possible"). Note that the case where the DC cluster on the discharge side is the second DC cluster 2 will be described, but the same operation is assumed to be performed even if the DC cluster on the discharge side is the first DC cluster 1 or the third DC cluster 3.

[0051] First, the power converter 25-1 of the second DC cluster 2 acquires the voltage of the DC grid 4 from the voltage / current sensor 27, and determines whether a voltage (V1 to V2) is applied across the clusters (DC grid 4) (S41). If no voltage is applied to the DC grid 4 (S41, No), assuming that no other DC cluster is outputting a discharge request, it returns to the "startup" operation shown in FIG. 5 (S42).

[0052] Also, if a voltage is applied to the DC grid 4 (S41, Yes), the power converter 25-1 raises the voltage of the second DC bus 29 to within the range of V7 to V8 (PV priority OFF) (S43), and stops the power supply from the power generation device 23 to the second DC bus 29 to the power converter 25-3. Then, the power converter lowers the voltage of the second DC bus 29 until it becomes the same as that of the DC grid 4 (S44), and turns on the switch 28 (S45).

[0053] When cluster-to-cluster power discharge is started, the second DC cluster 2 performs an operation according to the operation section shown in FIG. 2 (S46). When power is being transferred between DC clusters, the power converter 25-1 does not perform the operation according to the operation section, but continues the discharge operation of the energy storage device (Batt) 21.

[0054] Next, the power converter 25-1 determines whether the voltage of the second DC bus 29 (intra-cluster voltage) is within the range of V8 to V9 (all OFF) (S47). If the voltage of the second DC bus 29 is within the range of V8 to V9 (all OFF) (S47, Yes), assuming that a discharge stop request is output from the first DC cluster 1 on the charging side or that another discharging DC cluster is outputting a discharge stop notification, the power converters 25-1 to 25-4 control the switches 26-1 to 26-4 to disconnect the connection with the second DC bus 29, and then the power converter 25-1 turns off the switch 28 (S50).

[0055] Next, the second DC cluster 2 returns to its normal operation of determining which operation in the operation section shown in FIG. 2 to perform according to the voltage of the second DC bus 29 (S51), and returns to the "startup" operation shown in FIG. 5 (S52).

[0056] Also, in step S47, if the voltage of the second DC bus 29 is not within the range of V8 to V9 (all OFF) (S47, No), the power converter 25-1 detects the SOC of the power storage device (Batt) 21, determines whether the SOC (charge amount) is equal to or greater than a second predetermined value, and determines whether discharge is still possible (S48).

[0057] If the power converter 25-1 determines that the power storage device (Batt) 21 can still be discharged (SOC is equal to or greater than the second predetermined value) (S48, Yes), it returns to step S47 and repeats the subsequent processing. Also, if the power converter 25-1 determines that the power storage device (Batt) 21 can no longer be charged (SOC is less than the second predetermined value) (S48, No), it raises the voltage of the second DC bus 29 to within the range of V8 to V9 (all OFF) (S49), and notifies the first DC cluster 1 on the charging side to stop discharging.

[0058] Next, the power converters 25-1 to 25-4 control the switches 26-1 to 26-4 to disconnect the connection with the second DC bus 29. Then, the power converter 25-1 confirms that the voltage of the second DC bus 29 is 0V and turns off the switch 28 (S50).

[0059] Next, the second DC cluster 2 returns to its normal operation of determining which operation in the operation section shown in FIG. 2 to perform according to the voltage of the second DC bus 29 (S51), and returns to the "startup" operation shown in FIG. 5 (S52).

[0060] <Effect of the power distribution system 100> As described above, according to the power distribution system 100 according to the present embodiment, when the voltage of the first DC bus 19 is within the first range, the power converter 15-1 outputs a discharge request via the switching circuit 18 and the DC grid 4. Then, when the voltage of the second DC bus 29 is within the second range, the power converter 25-1 supplies power to the first DC cluster 1 via the switching circuit 28 and the DC grid 4 in response to the discharge request from the first DC cluster 1. Therefore, power can be transferred in a large-scale system in which a plurality of power generation devices (PV) 13 and 23 and energy storage devices (Batt) 11 and 21 are connected.

[0061] Further, when the voltage of the first DC bus 19 is within the first range, the power converter 15-1 connects the first DC bus 19 and the DC grid 4 by the switching circuit 18, and sets the voltage of the DC grid 4 to the voltage of the first DC bus 19, thereby outputting a discharge request. Therefore, by simply connecting the first DC bus 19 and the DC grid 4 by the switching circuit 18, a discharge request can be output to the second DC cluster 2.

[0062] Further, the power converter 25-1 to which the energy storage device 21 is connected lowers the voltage of the second DC bus 29 until it becomes the same as the voltage of the DC grid 4, and connects the second DC bus 29 and the DC grid 4 by the switching circuit 28 to supply power to the first DC cluster 1. Therefore, the second DC cluster 2 can transfer power to the first DC cluster 1 without generating an inrush current.

[0063] Further, after the power converter 25-1 connects the second DC bus 29 and the DC grid 4 by the switching circuit 28, the power converter 25-3 to which the power generation device 23 is connected resumes the power output by the power generation device 23. Therefore, power transfer from the second DC cluster 2 to the first DC cluster 1 can be performed more efficiently.

[0064] When the charge amount of the power storage device 11 becomes equal to or greater than a first predetermined value, the power converter 15-1 to which the power storage device 11 is connected is controlled to increase the voltage of the DC grid 4 until it is within a fourth range, and a discharge stop request is output to the second DC cluster 2. Therefore, when charging of the power storage device 11 becomes unnecessary, the first DC cluster 1 can output a discharge stop request to the second DC cluster 2 simply by increasing the voltage of the DC grid 4.

[0065] When the charge amount of the power storage device 21 becomes equal to or less than a second predetermined value, the power converter 25-1 to which the power storage device 21 is connected is controlled to increase the voltage of the DC grid 4 until it is within the fourth range, and discharge stop is notified to the first DC cluster 1. Therefore, when discharging of the power storage device 21 becomes impossible, the second DC cluster 2 can notify discharge stop to the first DC cluster 1 simply by increasing the voltage of the DC grid.

[0066] When the voltage of the DC grid 4 is within the fourth range, the power converters 15-1, 15-3, 15-4 to which the power generation device 13, the power storage device 11, and the load 14 are respectively connected are controlled to decrease the voltage of the first DC bus 19 until it becomes 0 V, and the switching circuit 18 disconnects the first DC bus 19 from the DC grid 4. Therefore, power transfer between clusters can be stably stopped.

[0067] When the voltage of the DC grid 4 is within the fourth range, the power converters 25-3, 25-1, 25-4 to which the power generation device 23, the power storage device 21, and the load 24 are respectively connected are controlled to decrease the voltage of the second DC bus 29 until it becomes 0 V, and the switching circuit 28 disconnects the second DC bus 29 from the DC grid 4. Therefore, power transfer between clusters can be stably stopped.

[0068] 〔Example of Realization by Software〕 The control block of the power distribution system 100 may be realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like, or may be realized by software.

[0069] In the latter case, the power distribution system 100 includes a computer that executes instructions of a program, which is software for realizing each function. This computer includes, for example, one or more processors and a computer-readable recording medium storing the above program. Then, in the above computer, when the above processor reads and executes the above program from the above recording medium, the object of the present invention is achieved. As the above processor, for example, a CPU (Central Processing Unit) can be used. As the above recording medium, a "non-transitory tangible medium", for example, in addition to a ROM (Read Only Memory) and the like, a tape, a disk, a card, a semiconductor memory, a programmable logic circuit, etc. can be used. Further, it may further include a RAM (Random Access Memory) for expanding the above program. Further, the above program may be supplied to the above computer via any transmission medium (such as a communication network or a broadcast wave) capable of transmitting the program. Note that one aspect of the present invention can also be realized in the form of a data signal embedded in a carrier wave, in which the above program is embodied by electronic transmission.

[0070] 〔Summary〕 The power distribution system according to Embodiment 1 of the present invention is a power distribution system in which a plurality of DC clusters are connected via a DC grid. The first DC cluster includes at least a first power generation device, a first power storage device, a first load, a first DC bus, and a first switching circuit. Each of the first power generation device and the first power storage device is connected to the first DC bus via a power converter, and the first DC bus is connected to the DC grid via the first switching circuit. The second DC cluster includes at least a second power generation device, a second power storage device, a second load, a second DC bus, and a second switching circuit. Each of the second power generation device and the second power storage device is connected to the second DC bus via a power converter, and the second DC bus is connected to the DC grid via the second switching circuit. When the voltage of the first DC bus is within a first range while the first switching circuit is disconnected, the power converter to which the first power storage device is connected connects the first switching circuit and outputs a discharge request via the DC grid. When the voltage of the second DC bus is within a second range exceeding the first range while the second switching circuit is disconnected, the power converter to which the second power storage device is connected connects the second switching circuit in response to the discharge request from the first DC cluster and supplies power to the first DC cluster via the DC grid.

[0071] In the power distribution system according to Embodiment 2 of the present invention, in the above Embodiment 1, when the voltage of the first DC bus is within the first range, the power converter to which the first power storage device is connected connects the first DC bus and the DC grid by the first switching circuit, and sets the voltage of the DC grid to the voltage of the first DC bus, thereby outputting the discharge request.

[0072] In the power distribution system according to Embodiment 3 of the present invention, in the above Embodiment 2, when the power converter to which the second power storage device is connected responds to the discharge request from the first DC cluster, the voltage of the second DC bus is increased until it falls within a third range exceeding the second range, so as to stop the power output from the second power generation device to the power converter to which the second power generation device is connected. Then, after lowering the voltage of the second DC bus until it becomes the same as the voltage of the DC grid, the second switching circuit connects the second DC bus and the DC grid, and starts supplying power to the first DC cluster.

[0073] In the power distribution system according to Embodiment 4 of the present invention, in the above Embodiment 3, after the second switching circuit connects the second DC bus and the DC grid, the power converter to which the second power generation device is connected resumes the power output by the second power generation device.

[0074] In the power distribution system according to Embodiment 5 of the present invention, in the above Embodiment 3, when the charge amount of the first power storage device connected to the first power converter reaches a first predetermined value or more, the voltage of the DC grid is increased until it falls within a fourth range exceeding the second range, and a discharge stop request is output to the second DC cluster.

[0075] In the power distribution system according to Embodiment 6 of the present invention, in the above Embodiment 3, when the charge amount of the second power storage device connected to the second power converter becomes a second predetermined value or less, the voltage of the DC grid is increased until it falls within a fourth range exceeding the second range, and a discharge stop is notified to the first DC cluster.

[0076] In the power distribution system according to Embodiment 7 of the present invention, in the above Embodiment 5 or 6, when the voltage of the DC grid falls within the fourth range, the power converters to which the first power generation device and the first power storage device are respectively connected lower the voltage of the first DC bus until it becomes 0V, and the power converter to which the first power storage device is connected disconnects the first DC bus and the DC grid by the first switching circuit.

[0077] In the power distribution system according to aspect 8 of the present invention, in the above aspect 5 or 6, when the voltage of the DC grid is within the fourth range, the power converters to which the second power generation device and the second power storage device are respectively connected lower the voltage of the second DC bus until it becomes 0 V, and the power converter to which the second power storage device is connected disconnects the second DC bus from the DC grid by the second switching circuit.

[0078] A power distribution method according to aspect 9 of the present invention is a power distribution method for a power distribution system in which a plurality of DC clusters are connected via a DC grid. The first DC cluster includes at least a first power generation device, a first power storage device, a first load, a first DC bus, and a first switching circuit. Each of the first power generation device and the first power storage device is connected to the first DC bus via a power converter, and the first DC bus is connected to the DC grid via the first switching circuit. The second DC cluster includes at least a second power generation device, a second power storage device, a second load, a second DC bus, and a second switching circuit. Each of the second power generation device and the second power storage device is connected to the second DC bus via a power converter, and the second DC bus is connected to the DC grid via the second switching circuit. When the voltage of the first DC bus is within the first range in a state where the first switching circuit is disconnected, the power converter to which the first power storage device is connected connects the first switching circuit and outputs a discharge request via the DC grid. When the voltage of the second DC bus is within a second range exceeding the first range in a state where the second switching circuit is disconnected, the power converter to which the second power storage device is connected supplies power to the first DC cluster via the DC grid by connecting the second switching circuit in response to the discharge request from the first DC cluster.

[0079] 〔Supplementary Notes〕 The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

Explanation of Reference Numerals

[0080] 1 First DC Cluster 2 Second DC Cluster 3 Third DC Cluster 4 DC Grid 11, 21, 31 Energy Storage Device (Batt) 12, 22, 32 Fuel Cell (FC) 13, 23, 33 Power Generation Device (PV) 14, 24, 34 Electric Vehicle (EV) 15-1 to 15-4, 25-1 to 25-4, 35-1 to 35-4 Power Converter 16-1 to 16-4, 26-1 to 26-4, 36-1 to 36-4 Switch 17, 27, 37 Voltage / Current Sensor 18, 28, 38 Switching Circuit (Switch) 19 First DC Bus 29 Second DC Bus 39 Third DC Bus 100 Distribution System

Claims

1. A power distribution system in which a plurality of DC clusters are connected via a DC grid, The first DC cluster includes at least a first power generation device, a first energy storage device, a first load, a first DC bus, and a first switching circuit. Each of the first power generation device and the first energy storage device is connected to the first DC bus via a power converter, and the first DC bus is connected to the DC grid via the first switching circuit. The second DC cluster includes at least a second power generation device, a second energy storage device, a second load, a second DC bus, and a second switching circuit. Each of the second power generation device and the second energy storage device is connected to the second DC bus via a power converter, and the second DC bus is connected to the DC grid via the second switching circuit. When the voltage of the first DC bus is within a first range while the first switching circuit is disconnected, the power converter connected to the first energy storage device connects the first switching circuit and outputs a discharge request via the DC grid. When the voltage of the second DC bus is within a second range exceeding the first range while the second switching circuit is disconnected, the power converter connected to the second energy storage device connects the second switching circuit in response to the discharge request from the first DC cluster and supplies power to the first DC cluster via the DC grid. A power distribution system.

2. The power converter connected to the first energy storage device When the voltage of the first DC bus is within the first range, the first switching circuit connects the first DC bus and the DC grid, and the discharge request is output by setting the voltage of the DC grid to the voltage of the first DC bus. The power distribution system according to claim 1.

3. The power converter connected to the second energy storage device When responding to the discharge request from the first DC cluster, the voltage of the second DC bus is raised until it is within a third range exceeding the second range, so that the power converter connected to the second power generation device stops the power output from the second power generation device. After that, the voltage of the second DC bus is lowered until it is the same as the voltage of the DC grid, and then The second switching circuit connects the second DC bus and the DC grid, and starts supplying power to the first DC cluster. The power distribution system according to claim 2.

4. The power converter connected to the second power generation device The power distribution system according to claim 3, wherein after the second switching circuit connects the second DC bus and the DC grid, the power output by the second power generation device is resumed.

5. The power converter to which the first power storage device is connected When the charge amount of the first power storage device becomes equal to or greater than a first predetermined value, the voltage of the DC grid is increased until it is within a fourth range exceeding the second range, and a discharge stop request is output to the second DC cluster. The power distribution system according to claim 3.

6. The power converter to which the second power storage device is connected When the charge amount of the second power storage device becomes equal to or less than a second predetermined value, the voltage of the DC grid is increased until it is within a fourth range exceeding the second range, and the first DC cluster is notified of the discharge stop. The power distribution system according to claim 3.

7. The power converters to which the first power generation device and the first power storage device are respectively connected When the voltage of the DC grid is within the fourth range, the voltage of the first DC bus is decreased until it becomes 0 V. The power converter to which the first power storage device is connected disconnects the first DC bus and the DC grid by the first switching circuit. The power distribution system according to claim 5 or 6.

8. The power converters to which the second power generation device and the second power storage device are respectively connected When the voltage of the DC grid is within the fourth range, the voltage of the second DC bus is decreased until it becomes 0 V. The power converter to which the second power storage device is connected disconnects the second DC bus and the DC grid by the second switching circuit. The power distribution system according to claim 5 or 6.

9. A power distribution method for a power distribution system in which a plurality of DC clusters are connected via a DC grid, The first DC cluster includes at least a first power generation device, a first power storage device, a first load, a first DC bus, and a first switching circuit. Each of the first power generation device and the first power storage device is connected to the first DC bus via a power converter, and the first DC bus is connected to the DC grid via the first switching circuit. The second DC cluster includes at least a second power generation device, a second power storage device, a second load, a second DC bus, and a second switching circuit. Each of the second power generation device and the second power storage device is connected to the second DC bus via a power converter, and the second DC bus is connected to the DC grid via the second switching circuit. When the voltage of the first DC bus is within a first range in a state where the first switching circuit is disconnected, a power converter to which the first power storage device is connected connects the first switching circuit and outputs a discharge request via the DC grid; When the voltage of the second DC bus is within a second range exceeding the first range in a state where the second switching circuit is disconnected, a power converter to which the second power storage device is connected connects the second switching circuit and supplies power to the first DC cluster via the DC grid in response to the discharge request from the first DC cluster; A power distribution method including the above.

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