Power control system, power control device, and power control method

Abstract

To provide a power control system, a power control device, and a power control method, for improving the degree of utilization of power generated by distributed power supplies at the time of autonomous operation.SOLUTION: A power control system comprises: a first power control device (12) for controlling power output by a first distributed power supply (10); and a second power control device (22) for controlling power output by a second distributed power supply (20). The first power control device has a function for autonomous operation output. The second power control device has an individual operation prevention function for preventing individual operation of the second distributed power supply. The first power control device sets upper limit output power to the second power control device so as to inhibit the individual operation prevention function from operating at the time of the autonomous operation, and makes the first distributed power supply output power equal to or greater than power obtained by subtracting power output by the second distributed power supply from power consumed at a load or makes the first distributed power supply consume power obtained by subtracting power consumed at the load from the power output by the second distributed power supply.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a power control system, a power control device, and a power control method. [Background technology]

[0002] For example, in the case of a distributed power source such as a solar power generation system, if the power supply from the grid is cut off due to a power outage or the like while the power conditioner is operating, the power conditioner continues to be able to supply power, which is called an islanding state. When the power conditioner enters islanding mode, it is necessary to stop the power supply from the power conditioner (inverter) for the safety of workers and others. For example, Patent Document 1 proposes a technology for detecting islanding of an inverter connected to a power grid. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-318928 Summary of the Invention [Problem to be solved by the invention]

[0004] It would be extremely advantageous if we could employ distributed power sources that have measures in place to prevent islanding, while also increasing the utilization of the electricity generated by the distributed power sources when they are operating independently.

[0005] In view of the above circumstances, an object of the present disclosure is to provide a power control system, a power control device, and a power control method that increase the utilization of power generated by a distributed power source during independent operation. [Means for solving the problem]

[0006] A power control system according to an embodiment of the present disclosure includes: A power control system capable of supplying power output from a first distributed power source and a second distributed power source to a load during isolated operation when the first distributed power source and the second distributed power source are disconnected from a grid, a first power control device that controls the power output by the first distributed power source; a second power control device that controls the power output by the second distributed power source, the first power control device has a function of independent operation output, the second power control device has an islanding operation prevention function that prevents the second distributed power source from operating alone, The first power control device, during stand-alone operation, An upper limit of output power is set for the second power control device so that the islanding prevention function does not operate, and The first distributed power source is caused to output power equal to or greater than the power consumed by the load minus the power output by the second distributed power source, or the first distributed power source is caused to consume power equal to the power output by the second distributed power source minus the power consumed by the load.

[0007] A power control device according to an embodiment of the present disclosure includes: A power control system capable of supplying power output from a first distributed power source and a second distributed power source to a load during isolated operation when the first distributed power source is disconnected from a grid, comprising: a power control device for controlling the power output from the first distributed power source, The power control device has a function of independent operation output, The power control device, during stand-alone operation, a second power control device that controls the power output by the second distributed power source has an islanding prevention function that prevents the second distributed power source from operating in an islanding manner, and sets an upper limit on the output power of the second distributed power source; and The first distributed power source is caused to output power equal to or greater than the power consumed by the load minus the power output by the second distributed power source, or the first distributed power source is caused to consume power equal to the power output by the second distributed power source minus the power consumed by the load.

[0008] A power control method according to an embodiment of the present disclosure includes: A power control system capable of supplying power output from a first distributed power source and a second distributed power source to a load during isolated operation in which the first distributed power source and the second distributed power source are disconnected from a grid, comprising: During autonomous operation, a second power control device that controls the power output by the second distributed power source has an islanding prevention function that prevents the second distributed power source from operating in an islanding manner, and sets an upper limit on the output power of the second distributed power source; and The first distributed power source is caused to output power equal to or greater than the power consumed by the load minus the power output by the second distributed power source, or the first distributed power source is caused to consume power equal to the power output by the second distributed power source minus the power consumed by the load. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a power control system, a power control device, and a power control method that increase the utilization of power generated by a distributed power source during independent operation. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing an example of the schematic configuration and operation of a known power control system. [Figure 2] FIG. 2 is a diagram showing an example of the schematic configuration and operation of a known power control system. [Figure 3] FIG. 3 is a diagram showing an example of the schematic configuration and operation of a known power control system. [Figure 4] FIG. 4 is a diagram illustrating an example of a schematic configuration and operation of a power control system according to an embodiment. [Figure 5] FIG. 5 is a block diagram showing an example of a schematic configuration of a power control device. [Figure 6] FIG. 6 is a flowchart illustrating an example of the operation of the power control device according to an embodiment. [Figure 7] FIG. 7 is a diagram showing an example of a schematic configuration and operation of a power control system according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a power control system, a power control device, and a power control method according to an embodiment of the present disclosure will be described with reference to the drawings. To explain the power control system according to the present embodiment, the operation of a known power control system will first be described.

[0012] Figures 1 and 2 are block diagrams showing an example of the schematic configuration of a known power control system. Figure 1 shows an example of the operation of the known power control system during grid-connected operation. Figure 2 shows an example of the operation of the same known power control system as Figure 1 during stand-alone operation.

[0013] The power control system shown in Fig. 1 includes a first distributed power source 100, a second distributed power source 20, and a distribution board 40. The first distributed power source 100 includes a first power source 11 and a first power control device 120. The second distributed power source 20 includes a second power source 21 and a second power control device 22.

[0014] The first distributed power source 100 may be a non-renewable energy power source, and may use, for example, a storage battery (referred to as BT in FIG. 1) as a power source. Hereinafter, the first distributed power source 100 will be described as a power storage device that uses, for example, a storage battery such as the first power source 11 as a power source. The second distributed power source 20 may be a renewable energy power source, and may use, for example, a solar cell (referred to as PV in FIG. 1) as a power source. Hereinafter, the second distributed power source 20 will be described as a photovoltaic power generation device that uses, for example, a solar cell such as the second power source 21 as a power source.

[0015] As shown in FIG. 1 , power from a first power source 11 is output to a first power control device 120. The first power control device 120 can be configured with a known power conditioner. The first power control device 120 converts the voltage of DC power output (discharged) from the storage battery, which is the first power source 11, into AC power by increasing or decreasing the voltage. The power converted to AC by the first power control device 120 is output to a distribution board 40 via a grid-connection relay 32 or an isolated operation relay 34. The distribution board 40 is connected to a grid 50 and a load 60.

[0016] The grid-connection relay 32 and the isolated operation relay 34 can be configured with any switches or the like. The grid-connection relay 32 and the isolated operation relay 34 are basically controlled so that one is open and the other is closed. That is, during grid-connection, the grid-connection relay 32 is closed and the isolated operation relay 34 is open (see FIG. 1). During isolated operation, the grid-connection relay 32 is opened and the isolated operation relay 34 is closed (see FIG. 2). Such control may be performed by the first power control device 120, or by another control unit or control device, etc.

[0017] The distribution board 40 includes a main breaker 31 that disconnects the grid 50 from the load 60, the first distributed power source 100, and the second distributed power source 20. The first distributed power source 100 operates in an independent mode when the grid 50 is disconnected by the main breaker 31. In this example, the distribution board 40 also includes a switching relay 42 that switches between grid-connected operation and independent operation in accordance with an instruction (control signal) from the first distributed power source 100. This allows the distribution board 40 to supply the output of the independent operation of the first distributed power source 100 to the load 60. In this example, the main breaker 31 and the switching relay 42 are controlled by the first power control device 120.

[0018] As shown in FIG. 1, the line connecting the grid-connected relay 32 and the switching relay 42 is referred to as a power transmission line PL1. The power transmission line PL1 is further connected to a grid 50. The line connecting the isolated operation relay 34 and the switching relay 42 is referred to as a power transmission line PL2. The line connecting the switching relay 42 and the load 60 is referred to as a power transmission line PL3. The switching relay 42 connects the power transmission line PL1 and the power transmission line PL3 during grid-connected operation (see FIG. 1). The switching relay 42 connects the power transmission line PL2 and the power transmission line PL3 during isolated operation in which the system is disconnected from the grid 50 (see FIG. 2). Here, the control of the switching relay 42 may be performed by the first power control device 120 or by another control unit, control device, or the like.

[0019] The system 50 may be a typical commercial power system (grid).

[0020] The load 60 may be any of various devices, such as home appliances used by a user, to which power is supplied from the power control system. While the load 60 is shown as a single component in FIG. 1, the load 60 is not limited to a single component and may be any number of various devices. Furthermore, the load 60 may be any of various devices connected via an outlet in indoor wiring.

[0021] The first power control device 120 may be a bidirectional inverter. In this case, the first power control device 120 can convert AC power from the grid 50 into DC, increase or decrease the voltage of the DC power, and supply (charge) the DC power to the storage battery, which is the first power source 11.

[0022] Power from the second power source 21 is output to the second power control device 22. The second power control device 22 can also be configured with a known power conditioner. The second power control device 22 converts the voltage of the DC power output from the second power source 21 into AC power by increasing or decreasing the voltage. The power converted to AC by the second power control device 22 is output to the distribution board 40 via the interconnection relay 33. The second distributed power source 20 is connected to the power transmission line PL1 so that the AC power from the second power control device 22 is output to the distribution board 40 via the power transmission line PL1. Here, the control of the interconnection relay 33 may be performed by the first power control device 120, or may be performed by another control unit or control device, etc.

[0023] As described above, the power control system shown in FIG. 1 is in a grid-connected operation state. The main breaker 31, the grid-connection relay 32, and the grid-connection relay 33 are closed, the isolated operation relay 34 is open, and the switching relay 42 connects the power transmission line PL1 and the power transmission line PL3. In this operating state, at least one of the output of the first distributed power source 100 and the output of the second distributed power source 20 can be supplied to the load 60. The load 60 can also be supplied with power from the grid 50. Furthermore, the first distributed power source 100 can be charged with power supplied from at least one of the grid 50 and the second distributed power source 20. The power generated by the second distributed power source 20 can also be sold to the grid 50. In this way, the power control system shown in FIG. 1 can control the power of multiple distributed power sources.

[0024] When, for example, a power outage is detected, the power control system shown in Fig. 1 enters an operating state as shown in Fig. 2. As described above, the power control system shown in Fig. 2 shows the state during isolated operation. The main breaker 31, the grid-connection relay 32, and the grid-connection relay 33 are open, the isolated operation relay 34 is closed, and the switching relay 42 connects the power transmission line PL2 and the power transmission line PL3.

[0025] More specifically, when a power outage or the like is detected in the power control system shown in Fig. 1, the first power control device 120 opens the main breaker 31, the grid-connection relay 32, and the grid-connection relay 33. Then, when the switching relay 42 connects the power transmission lines PL2 and PL3 and the isolated operation relay 34 is closed (see Fig. 2), the first distributed power source 100 starts outputting isolated operation and supplies power to the load 60. In the power control system shown in Fig. 1, it can take about 10 seconds from the time a power outage is detected until the switching relay 42 is activated. In this operating state, even during a power outage, the power stored in the storage battery of the first distributed power source 100 can be supplied to the load 60 by the isolated operation output.

[0026] 2, because the interconnection relay 33 and the main breaker 31 are open, the power generated by the second distributed power source 20 does not flow back to the grid 50 during a power outage. Furthermore, the second power control device 22 has an islanding operation prevention function that prevents islanding operation, and can independently detect a power outage in the grid 50. Therefore, even if the grid 50 is not disconnected by the main breaker 31, islanding operation of the second distributed power source 20 is avoided, and the power generated by the second distributed power source 20 during a power outage does not flow back to the grid 50.

[0027] However, in the power control system shown in Fig. 2, the grid-connection relay 33 of the second distributed power source 20 is open and the second distributed power source 20 is not connected to the load 60. Therefore, in the operating state shown in Fig. 2, even if the second power source 21 is able to generate power, the power output by the second distributed power source 20 cannot be supplied to the load 60.

[0028] Fig. 3 is a block diagram showing a schematic configuration example of another known power control system, illustrating an example of operation during stand-alone operation. The same components as those in Figs. 1 and 2 are given the same reference numerals and descriptions thereof will be omitted. The other known power control system shown in Fig. 3 is a so-called multi-DC link type energy storage system, in which a first distributed power source 100 includes a first power control device 120 that controls a first power source 11 and a second power source 21. In other words, the first power control device 120 in Fig. 3 also performs the function of the second power control device 22 in Figs. 1 and 2.

[0029] In the power control system shown in Fig. 3, when the second distributed power source 20 is in an independent operation state and capable of generating power, the power output by the second distributed power source 20 can be supplied to the load 60. However, from the beginning, the second power source 21 is controlled by the first distributed power source 100. The power control system shown in Fig. 3 cannot be configured as a power control system that combines the first distributed power source 100 and the second distributed power source 20, each of which functions independently, as in Figs. 1 and 2.

[0030] Therefore, in a power control system according to an embodiment of the present disclosure, it is possible to configure a system by combining distributed power sources that function independently.

[0031] The power control system according to this embodiment will be described below. Fig. 4 is a block diagram showing an example of the schematic configuration of the power control system 1 according to this embodiment.

[0032] As shown in FIG. 4, the power control system 1 according to this embodiment includes a first power control device 12 instead of the first power control device 120 shown in FIG. 1. The first power control device 12 is a power conditioner. The power control system 1 includes a first distributed power source 10 and a second distributed power source 20. The first distributed power source 10 includes a first power source 11 and a first power control device 12. The second distributed power source 20 includes a second power source 21 and a second power control device 22. The first power control device 12 controls the power output by the first power source 11. The second power control device 22 controls the power output by the second power source 21.

[0033] Furthermore, in the power control system 1 according to this embodiment, there is no switching relay 42 in the distribution board 40, and the power transmission line PL1 and the power transmission line PL2 are connected to the power transmission line PL3.

[0034] Furthermore, in the power control system 1 according to this embodiment, the first power control device 12 can set the upper limit of output power by sending a command (dummy command) in the form of remote output control to the second power control device 22. Details of the dummy command will be described later.

[0035] Furthermore, as shown in FIG. 4, a current detection unit CT may be provided to detect the current flowing through the power transmission line PL1. The current detection unit CT is, for example, a current sensor such as a current transformer, but any element capable of detecting current may be used. The second power control device 22 detects a reference voltage waveform based on the detection signal of the current detection unit CT. The current detection unit CT may be built into the second distributed power source 20 as long as it can detect the reference voltage waveform. During stand-alone operation, when the second power control device 22 detects the reference voltage waveform, it closes the grid-connection relay 33, which was open. When the grid-connection relay 33 is closed, AC power (power A in FIG. 4) from the second power control device 22 is output to the distribution board 40 via the power transmission line PL1 and supplied to the load 60.

[0036] 4 shows the operation of the power control system 1 during isolated operation, with the interconnection relay 33 in a closed state. In the following, the AC power from the second power control device 22 output to the power transmission line PL1 is referred to as power A. The AC power from the first power control device 12 output to the power transmission line PL2 is referred to as power B. The AC power input to the first power control device 12 via the power transmission line PL2 is referred to as power B'. The AC power supplied to the load 60 via the power transmission line PL3 is referred to as power C.

[0037] The other components of the power control system 1 are the same as those described with reference to Fig. 1, and therefore will not be described again to avoid duplication. Furthermore, the control of opening and closing of the main breaker 31 by the first power control device 12 is the same as that described above with reference to Fig. 1, and therefore will not be described again below.

[0038] Next, the first power control device 12 and the second power control device 22 provided in the power control system 1 according to this embodiment will be further described. Fig. 5 is a block diagram showing an example of the schematic configuration of the first power control device 12 and the second power control device 22.

[0039] 5, the first power control device 12 includes a first DC / DC converter 13, a first inverter 14, a first control unit 15, a first storage unit 16, and a first communication unit 17. The second power control device 22 includes a second DC / DC converter 23, a second inverter 24, a second control unit 25, a second storage unit 26, and a second communication unit 27.

[0040] The first DC / DC converter 13 increases or decreases the voltage of the DC power from the first power supply 11. The DC power whose voltage has been increased or decreased by the first DC / DC converter 13 is output to the first inverter 14. The first DC / DC converter 13 can be configured using a known converter.

[0041] The first inverter 14 converts the DC power from the first DC / DC converter 13 into AC power. During grid-connected operation, the AC power converted by the first inverter 14 is supplied to the load 60 via the grid-connection relay 32 and the power transmission line PL1 and the distribution board 40. During isolated operation, the AC power converted by the first inverter 14 is supplied to the load 60 via the isolated operation relay 34 and the power transmission line PL2 and the distribution board 40.

[0042] If the first power source 11 is a storage battery, it can be charged with power supplied from the second distributed power source 20. In this case, the first inverter 14 converts AC power from the second distributed power source 20 into DC power. The first DC / DC converter 13 then increases or decreases the voltage of the DC power from the first inverter 14 and supplies it to the first power source 11, which is a storage battery. The first power source 11 can be charged with the power supplied in this manner. If the first power source 11 is a storage battery, it can also be charged with power supplied from the grid 50.

[0043] The first control unit 15 controls and manages each functional unit of the first power control device 12 as a whole. The first control unit 15 can be configured to include, for example, a CPU (Central Processing Unit). The first control unit 15 controls switching between the grid-connected relay 32 and the independent operation relay 34. During grid-connected operation, the first control unit 15 closes the grid-connected relay 32 and opens the independent operation relay 34. When switching from grid-connected operation to independent operation due to a power outage or the like, the first control unit 15 opens the grid-connected relay 32 and closes the independent operation relay 34. The operation of the first control unit 15 will be described further below.

[0044] The first power control device 12 may include at least one processor as a first control unit 15 to provide control and processing capabilities for performing various functions. According to various embodiments, the at least one processor may be implemented as a single integrated circuit (IC), or as multiple communicatively coupled integrated circuits. The at least one processor may be implemented according to various known techniques.

[0045] In one embodiment, a processor comprises one or more circuits or units configured to perform one or more data computational procedures or processes. For example, a processor may comprise one or more microprocessors, microcontrollers, application specific integrated circuits (ASICs), digital signal processors, programmable logic devices, field programmable gate arrays, or combinations thereof.

[0046] The first storage unit 16 may be configured with a semiconductor memory, a magnetic memory, or the like. The first storage unit 16 stores various information and programs executed by the first control unit 15. The first storage unit 16 may function as a work memory for the first control unit 15. Furthermore, the first storage unit 16 may be included in the first control unit 15.

[0047] The first communication unit 17 includes one or more communication modules that communicate with the communication device 70. The first communication unit 17 may include, for example, a communication module that complies with a wired or wireless LAN standard. In this embodiment, the communication device 70 is a network hub, and the first communication unit 17 and the communication device 70 are connected via a wired LAN. As another example, the first communication unit 17 may include a communication module that complies with a mobile communication standard such as 4G (4th Generation) or 5G (5th Generation).

[0048] The second DC / DC converter 23 increases or decreases the voltage of the DC power from the second power supply 21. The DC power whose voltage has been increased or decreased by the second DC / DC converter 23 is output to the second inverter 24. The second DC / DC converter 23 can be configured using a known converter.

[0049] The second inverter 24 converts the DC power from the second DC / DC converter 23 into AC power. The AC power converted by the second inverter 24 passes through the interconnection relay 33 and the power transmission line PL1, and is supplied to the load 60 via the distribution board 40.

[0050] The second control unit 25 controls and manages each functional unit and the entire second power control unit 22. The second power control unit 22 may include at least one processor as the second control unit 25 to provide control and processing power for executing various functions. The configuration of the second control unit 25 may be the same as or different from that of the first control unit 15.

[0051] As described above, the second control unit 25 closes the interconnection relay 33 when it detects the reference voltage waveform based on the detection signal of the current detection unit CT.

[0052] The second storage unit 26 may be configured with a semiconductor memory, a magnetic memory, or the like. The second storage unit 26 stores various information and programs executed by the second control unit 25. The various information includes an execution schedule and an update schedule for remote output control. The second storage unit 26 may function as a work memory for the second control unit 25. The second storage unit 26 may also be included in the second control unit 25.

[0053] The second communication unit 27 includes one or more communication modules that communicate with the communication device 70. The second communication unit 27 may include, for example, a communication module that complies with a wired or wireless LAN standard. In this embodiment, the communication device 70 is a network hub, and the second communication unit 27 and the communication device 70 are connected via a wired LAN. As another example, the second communication unit 27 may include a communication module that complies with a mobile communication standard such as 4G or 5G. The configuration of the second communication unit 27 may be the same as or different from that of the first communication unit 17.

[0054] Here, the second power control device 22 has an islanding prevention function. Therefore, when the first control unit 15 of the first power control device 12 detects, for example, a power outage and opens the grid-connected relay 32 and closes the grid-independent operation relay 34 to switch from grid-connected operation to grid-independent operation, the second power control device 22 keeps the grid-connected relay 33 open until it detects a reference voltage waveform from the grid 50. In this embodiment, the first power control device 12 generates a reference voltage waveform when switching from grid-connected operation to grid-independent operation. In order for the second power control device 22 to recognize the reference voltage waveform generated by the first power control device 12 as being from the grid 50 (to determine that it is equivalent to the reference voltage waveform sent from the grid 50), the power of the generated reference voltage waveform must be sufficiently large. More specifically, the second power control device 22 determines that it has detected a reference voltage waveform from the grid 50 when there is a phase difference between the voltage waveform that the second power control device 22 itself generates and attempts to output and the detected reference voltage waveform. The phase difference is maintained when the power magnitude of the reference voltage waveform is equal to or greater than the power magnitude of the voltage waveform generated by the second power control device 22 itself. Therefore, the first control unit 15 of the first power control device 12 sets an upper limit on the output power of the second power control device 22 so that the islanding prevention function of the second power control device 22 does not operate. Then, the first control unit 15 generates and outputs a reference voltage waveform equal to or greater than the output power of the second power control device 22.

[0055] In this embodiment, the first control unit 15 of the first power control device 12 sets the upper limit of output power by sending a dummy command in the form of remote output control to the second power control device 22. Here, a distributed power system that has a reverse power flow (power selling) contract with an electric power company is required to have a function for receiving remote output control commands from the electric power company's power server 72. During grid-connected operation, the second communication unit 27 receives remote output control commands from the power server 72 via a network 71 such as the Internet and a communication device 70, and controls the output magnitude of the second power control device 22 according to a specified schedule. The first power control device 12 uses the remote output control command reception function of the second power control device 22 to send a dummy command in the form of remote output control that sets the upper limit of output power during stand-alone operation.

[0056] The second power control device 22 detects the reference voltage waveform generated by the first power control device 12 based on the detection signal of the current detection unit CT, and when it recognizes this reference voltage waveform as equivalent to that of the grid 50, it closes the grid-connection relay 33. Figures 4 and 5 show the state of the power control system 1 in this case (a state in which the grid-connection relay 33 is closed, the grid-connection relay 32 is open, and the isolated operation relay 34 is closed). At this time, the second distributed power source 20 is connected to the load 60, and power A from the second power control device 22 can be supplied to the load 60.

[0057] 4 and 5, the first power control device 12 causes the first distributed power source 10 to output power (power B) that is equal to or greater than the power (power C) consumed by the load 60 minus the power (power A) output by the second distributed power source 20, or causes the first distributed power source 10 to consume power (power B') that is the power (power A) output by the second distributed power source 20 minus the power (power C) consumed by the load 60. Hereinafter, the control by the first power control device 12 will be specifically described assuming that the first power source 11 is a storage battery and the second power source 21 is a solar cell.

[0058] When the storage battery (first power source 11) discharges during stand-alone operation, the first power control device 12 causes the storage battery to discharge power B equal to or greater than the power obtained by subtracting power A output from the solar cell (second power source 21) from power C consumed by the load 60. For example, if power C consumed by the load 60 is 3.9 kW and the upper limit of output power for the second power control device 22 is set to 1.9 kW, power A will not exceed 1.9 kW, so the first power control device 12 causes power B to be output at 2.0 kW or greater. During stand-alone operation, power is supplied to the load 60 using combined power including power from the solar cell, thereby reducing the power consumption of the storage battery and enabling a long-term power supply, while also making effective use of the power generated by the solar cell. Here, the first power control device 12 sets the upper limit of the output power of the second power control device 22 to be equal to or less than half of power C consumed by the load 60. Furthermore, in the following, the above-mentioned power relational expression (power B≧power C−power A) when the storage battery is discharging during independent operation may be referred to as the “relational expression between power A, power B, and power C.”

[0059] When the storage battery (first power source 11) is being charged during stand-alone operation, the first power control device 12 charges the storage battery with power B', which is the power A output from the solar cell (second power source 21) minus the power C consumed by the load 60. For example, the power C consumed by the load 60 is 1.0 kW, the upper limit of the output power for the second power control device 22 is set to 1.9 kW, and the power A is 1.9 kW. In this case, the first power control device 12 charges the storage battery with power B' of 0.9 kW. During stand-alone operation, power is supplied to the load 60 using power from the solar cell, and any surplus power is charged to the storage battery, thereby making it possible to maximize power utilization. Here, the first power control device 12 sets the upper limit of the output power of the second power control device 22 to a value equal to or less than the power that can charge the storage battery. In other words, even if the power C consumed by the load 60 is zero, all of the power A output from the solar cell is effectively used for charging up to the amount of power that can charge the storage battery. Furthermore, in the following, the above-mentioned power relational expression (power B' = power A - power C) when the storage battery is charging during independent operation may be referred to as the "relational expression between power A, power B' and power C."

[0060] In this embodiment, the first power control device 12 performs constant voltage control so that the relational expression between power A, power B, and power C or the relational expression between power A, power B', and power C is satisfied. Constant voltage control is control that keeps the voltage at point CP (see FIG. 4) on the power transmission line PL3 constant. The voltage at point CP corresponds to the output voltage of the first inverter 14. For example, when power C is supplied to balance the power consumed by the load 60, the voltage at point CP is assumed to be 200 V. When power A output from the solar cell increases and the voltage at point CP exceeds 200 V, the first power control device 12 charges the storage battery with surplus power exceeding the power consumed by the load 60 as power B'. When power A output from the solar cell decreases and the voltage at point CP is 200 V or less, the first power control device 12 discharges power B to compensate for the power shortage compared to the power consumed by the load 60. By performing constant voltage control, the first power control device 12 can automatically switch between discharging and charging the storage battery without performing complex calculations.

[0061] Furthermore, the power control system 1 according to this embodiment is configured by combining a standard first distributed power source 10 and a standard second distributed power source 20, each of which functions independently, and does not require a special configuration (multi-DC link type) as shown in Fig. 3. Therefore, it is possible to easily convert an existing system of distributed power sources that functions independently into the power control system 1 according to this embodiment.

[0062] As described above, during stand-alone operation, the first power control device 12 sets the upper limit of output power by sending a dummy command in the form of remote output control to the second power control device 22. In order to appropriately set the upper limit of the output power of the second power control device 22, the first power control device 12 may acquire information about the rated capacity of the second power control device 22 in advance before sending the dummy command in the form of remote output control. The information about the rated capacity may be stored in, for example, the first storage unit 16. In this case, the first power control device 12 can prevent the upper limit of the output power of the second power control device 22 that it sets from exceeding the rated capacity and can prevent an unstable state caused by a temporary voltage drop that would result from such an exceedance.

[0063] Furthermore, the first power control device 12 may change the upper limit of the output power of the second power control device 22 by a new dummy command in response to fluctuations in the load 60. Here, a sensor that detects the current flowing through the power transmission line PL3 may be provided (see the first current detection unit CT1 in FIG. 7), and the first power control device 12 may detect fluctuations in the load 60 based on a detection signal from the sensor. At this time, if the power consumed by the load 60 decreases, the first power control device 12 can also lower the upper limit of the output power of the second power control device 22 by a dummy command. By responding to fluctuations in the load 60 in this way, it is possible to prevent the power A from becoming larger than the power B (the upper limit of the output power of the second power control device 22 is no longer half or less of the power C), thereby preventing the islanding operation prevention function of the second power control device 22 from activating.

[0064] Furthermore, as described above, during autonomous operation, the power control system 1 supplies power to the load 60 using combined power including power from the solar cell, thereby reducing the power consumption of the storage battery and enabling a long-term power supply. The available capacity and available time of the storage battery may be displayed on a display device of a HEMS (Home Energy Management System), for example.

[0065] Furthermore, the communication device 70 used to transmit the dummy command of the first power control device 12 is not limited to a network hub. As another example, the communication device 70 may be a router, a remote control for a HEMS, or a distributed power source. In other words, the communication device 70 may be a device having various communication functions used to receive a command for remote output control from a power server 72 of a power company.

[0066] For example, if the communication device 70 is a remote control for a HEMS or a distributed power source, the transmission of a dummy command may be executed as follows: First, the remote control for the HEMS or the distributed power source is activated when the first power control device 12 starts independent operation. The first control unit 15 of the first power control device 12 instructs the remote control for the HEMS or the distributed power source to generate and transmit a dummy command. Upon receiving the dummy command from the remote control for the HEMS or the distributed power source, the second power control device 22 sets an upper limit on the output power in accordance with the dummy command. If the communication device 70 is a remote control for a HEMS or a distributed power source, the dummy command for independent operation can be generated by the same device as the command for normal remote output control during grid-connected operation.

[0067] Furthermore, during grid-connected operation, the contents of the remote output control commands from the power server 72 (including, for example, an update schedule) may be managed as an electronic calendar associated with the date and time. The electronic calendar is stored, for example, in the second storage unit 26. The electronic calendar may also be managed by the power server 72, a HEMS, or the like. The second control unit 25 may, for example, read the electronic calendar from the second storage unit 26, control the second power source 21 according to the electronic calendar, and adjust the output power of the second power control device 22. Here, the contents of the electronic calendar stored in the second storage unit 26 may be changed by a dummy command during isolated operation. At this time, for example, when a power outage is resolved and the system returns from isolated operation to grid-connected operation, the first control unit 15 of the first power control device 12 may request the power server 72 or the HEMS to transmit the electronic calendar to the second power control device 22. Furthermore, if the communication device 70 is a HEMS, the HEMS may transmit the electronic calendar to the second power control device 22 when the system returns from isolated operation to grid-connected operation, even without a request from the first power control device 12.

[0068] Furthermore, during grid-connected operation, not only the second power control device 22 but also the first power control device 12 may acquire the content of the remote output control command. At this time, the content of the remote output control command may be stored in the first storage unit 16. When returning from independent operation to grid-connected operation, the first control unit 15 of the first power control device 12 may transmit the content of the remote output control command stored in the first storage unit 16 to the second power control device 22 by a dummy command. Even if the content of the electronic calendar stored in the second storage unit 26 is changed by a dummy command during independent operation, the first control unit 15 can restore the content of the electronic calendar by further overwriting the content of the remote output control command from the power server 72 by a dummy command. Here, the content of the remote output control command transmitted by the first control unit 15 may be, for example, the content of the schedule after power restoration, or may be, for example, the entire content of the annual schedule.

[0069] Here, the first power control device 12 may apply an interlock that prevents the electronic calendar in the second storage unit 26 from being updated, so as to prevent the contents of the electronic calendar stored in the second storage unit 26 from being accidentally changed. The first power control device 12 may release the interlock only when a remote output control command is received from the power server 72 or when a dummy command is output.

[0070] FIG. 6 is a flowchart illustrating the operation (power control method) of the first power control device 12 and the second power control device 22 provided in the power control system 1 according to this embodiment during independent operation.

[0071] When the first power control device 12 detects a power outage or the like, it switches from grid-connected operation to independent operation (Yes in step S1). When switching from grid-connected operation to independent operation, the first power control device 12 opens the grid-connected relay 32 and closes the independent operation relay 34. When the first power control device 12 does not detect a power outage or the like and continues grid-connected operation (No in step S1), it does not perform the processes in the following steps S2 to S6.

[0072] The first power control device 12 outputs a reference voltage waveform (step S2). The first power control device 12 also sets an upper limit on output power for the second power control device 22 by sending a dummy command so that the islanding prevention function does not operate (step S3). The second power control device 22 detects the reference voltage waveform based on the detection signal of the current detection unit CT. Upon detecting the reference voltage waveform, the second power control device 22 closes the interconnection relay 33, which was in the open state (see FIG. 4).

[0073] The first power control device 12 determines whether the storage battery is in a state requiring a discharging operation or a charging operation. In this embodiment, the first power control device 12 executes constant voltage control, and determines that the storage battery is in a state requiring a discharging operation when the voltage at point CP is equal to or less than a reference value (for example, 200 V). Furthermore, the first power control device 12 determines that the storage battery is not in a state requiring a discharging operation (is in a state requiring a charging operation) when the voltage at point CP exceeds the reference value.

[0074] When the first power control device 12 determines that the storage battery is in a state requiring a discharge operation (Yes in step S4), it controls the storage battery to discharge power B that is equal to or greater than the power C consumed by the load 60 minus the power A output by the second power control device 22 (step S5).

[0075] When the first power control device 12 determines that the storage battery is in a state requiring charging (No in step S4), it controls the storage battery to be charged with power B', which is the power A output by the second power control device 22 minus the power C consumed by the load 60 (step S6).

[0076] As described above, the power control system 1, power control device (first power control device 12), and power control method according to this embodiment can continue to supply the output of a distributed power source such as a solar power generation device to the load 60 in accordance with the output of the independent operation of the power storage device, without activating the islanding operation prevention function of the distributed power source. Therefore, it is possible to increase the utilization rate of the power generated by the distributed power source during independent operation.

[0077] Furthermore, the first power control device 12 according to this embodiment can set an upper limit on output power by sending a dummy command in the form of remote output control to the second power control device 22. Because the function of receiving commands for remote output control is provided in existing systems, it is possible to easily convert existing systems into the power control system 1 according to this embodiment by updating the control program or the like.

[0078] In addition, the first power control device 12 of this embodiment can automatically switch between discharging and charging the storage battery without performing complex calculations by performing constant voltage control to keep the voltage on the transmission line PL3 connected to the load 60 constant.

[0079] While the present disclosure has been described based on various drawings and examples, it should be noted that those skilled in the art would readily be able to make various modifications or alterations based on the present disclosure. Therefore, it should be noted that these modifications and alterations are within the scope of the present disclosure. For example, functions contained in each functional unit may be rearranged so as not to cause logical inconsistencies. Multiple functional units may be combined into one or separated. The above-described embodiments of the present disclosure are not limited to faithful implementation of each of the described embodiments, but may be implemented by combining features or omitting some features as appropriate.

[0080] In the above embodiment, the first power control device 12 performed control to keep the voltage at point CP on the power transmission line PL3 constant (constant voltage control). Here, as shown in Fig. 7, the power control system 1 may include a first current detection unit CT1 and a second current detection unit CT2, and the first power control device 12 may perform control to adjust the power B or the power B' based on the detection values ​​from the first current detection unit CT1 and the second current detection unit CT2.

[0081] The first current detection unit CT1 detects the current flowing to the load 60 via the transmission line PL3. The second current detection unit CT2 detects the current flowing from the second power control device 22 to the transmission line PL1. The second current detection unit CT2 also functions as the current detection unit CT used to detect the reference voltage waveform in the above embodiment. The first control unit 15 of the first power control device 12 calculates power C by multiplying the detection value (current value) of the first current detection unit CT1 by a voltage value (e.g., the output voltage value of the first inverter 14). The first control unit 15 of the first power control device 12 calculates power A by multiplying the detection value (current value) of the second current detection unit CT2 by a voltage value (e.g., the output voltage value of the first inverter 14). The first control unit 15 may then perform control to adjust power B or power B' so that the above-described relationship between power A, power B, and power C or the relationship between power A, power B', and power C is satisfied.

[0082] In the above embodiment, the first distributed power source 10 has been described as a power storage device. Furthermore, in the above embodiment, the second distributed power source 20 has been described as a solar power generation device. Here, the first distributed power source 10 is not limited to a power storage device. Furthermore, the second distributed power source 20 is not limited to a solar power generation device. The first distributed power source 10 may be any of various non-renewable energy power sources capable of supplying and receiving power, such as a distributed power generation system composed of a fuel cell device and a heat pump water heater. Furthermore, the second distributed power source 20 may be any of various renewable energy power sources. For example, the second distributed power source 20 may be a fuel cell device such as a solid oxide fuel cell (SOFC) or a polymer electrolyte fuel cell (PEFC). Furthermore, for example, if the first distributed power source 10 is a power storage device, the second distributed power source 20 may be another power storage device.

[0083] In the above embodiment, the power control system 1 is configured to include one first power control device 12 and one second power control device 22. Here, the power control system 1 may be configured to include multiple first power control devices 12. In this case, the above-mentioned power B is the total AC power of the multiple first power control devices 12. Furthermore, the power control system 1 may be configured to include multiple second power control devices 22. In this case, the above-mentioned power A is the total AC power of the multiple second power control devices 22. The same applies when some of the multiple second power sources 21 to which the multiple second power control devices 22 are connected are fuel cells. Here, in order to start the fuel cell and obtain power during independent operation, a known method such as a method using a pseudo current circuit can be adopted.

[0084] In the above embodiment, the power control system 1 is described as being configured by combining a standard first distributed power source 10 and a standard second distributed power source 20, each of which functions independently. Here, the power control system 1 can use a power storage device having an overload protection function and an overvoltage protection function as the first distributed power source 10 without changing the configuration. Here, the overload protection function and the overvoltage protection function are functions in which the first power control device 12 stops the output of power when the voltage on the power transmission line PL3 connected to the load 60 is undervoltage or overvoltage. As described above, in the power control system 1 according to this embodiment, the first power control device 12 performs constant voltage control. The first power control device 12 controls the voltage on the power transmission line PL3 to avoid an undervoltage state (e.g., 180 V or less) or an overvoltage state (e.g., 220 V or more) and maintains a constant reference voltage (e.g., 200 V). Therefore, even if a power storage device having an overload protection function and an overvoltage protection function is used as the first distributed power source 10, the power control system 1 can effectively utilize the power generated by the storage battery and the solar cell by avoiding the activation of the overload protection function and the overvoltage protection function. Even if the first power control device 12 does not perform constant voltage control, it is preferable that the power control system 1 controls the voltage on the power transmission line PL3 connected to the load 60 within an output voltage range in which the overload protection function and the overvoltage protection function do not activate.

[0085] Furthermore, in the power control system 1 according to this embodiment, an upper limit on output power is set for the second power control device 22, and the setting of the upper limit on output power may be terminated at the following times: The setting of the upper limit on output power may be terminated when the system is no longer in autonomous operation; The setting of the upper limit on output power may be terminated when the first power source 11 loses the power it can supply (for example, when the first power source 11, which is a storage battery, becomes empty) when the power consumed by the load 60 is greater than the power generated by the second power source 21; The setting of the upper limit on output power may be terminated when the first power source 11 can no longer consume power (for example, when the first power source 11, which is a storage battery, becomes fully charged) when the power generated by the second power source 21 is greater than the power consumed by the load 60. [Explanation of symbols]

[0086] 1. Power control system 10 1st distributed power source 11 1st power supply 12 First power control device 13 First DC / DC converter 14 First inverter 15 First Control Section 16 1st memory section 17 First Communications Department 20 2nd distributed power supply 21 2nd power supply 22 Second power control device 23 Second DC / DC converter 24 Second inverter 25 Second Control Section 26 2nd memory section 27 Second Communications Department 31 Main breaker 32 Grid-connected relay 33 Grid-connected relay 34 Standalone Operation Relay 40 Distribution board 42 Switching relay 50 lines 60 load 70 Communication equipment 71 Network 72 Power Server 100 1st distributed power source 120 First power control device CT current detection section CT1 First current detection section CT2 Second current detection section PL1 Transmission Line PL2 Transmission Line PL3 Transmission Line

Claims

1. A power control system capable of supplying power output from a first distributed power source and a second distributed power source to a load during isolated operation in which the first distributed power source and the second distributed power source are disconnected from a grid, a first power control device that controls the power output by the first distributed power source; a second power control device that controls the power output by the second distributed power source, the first power control device has a function of independent operation output, the second power control device has an islanding operation prevention function that prevents the second distributed power source from operating alone, The first power control device, during stand-alone operation, A predetermined output power is set for the second power control device so that the islanding prevention function does not operate, and a power control system that causes the first distributed power source to output power or causes the first distributed power source to consume power;

2. The power control system described in Claim 1, wherein the first power control device sets an upper limit output power as the specified output power during autonomous operation.

3. The first power control device, during independent operation, 2. The power control system of claim 1, wherein the first distributed power source is caused to output power equal to or greater than the power consumed by the load minus the power output by the second distributed power source, or the first distributed power source is caused to consume power equal to the power output by the second distributed power source minus the power consumed by the load.

4. 4. The power control system according to claim 1, wherein the first power control device sets the predetermined output power by sending a command in a remote output control format to the second power control device.

5. The power control system according to claim 1 , wherein the first power control device performs constant voltage control to keep constant a voltage in a power transmission line connected to the load.

6. the first distributed power source is a non-renewable energy power source; The power control system according to claim 1 , wherein the second distributed power source is a renewable energy power source.

7. The power control system according to claim 1 , wherein the first distributed power source is a storage battery.

8. The power control system according to claim 1 , wherein the second distributed power source is a solar cell.

9. The first power control device 9. The power control system according to claim 1, wherein, when operating autonomously and power output from the first distributed power source is required, the first distributed power source is caused to discharge power equal to or greater than the power consumed by the load minus the power output from the second distributed power source.

10. The first power control device 10. The power control system according to claim 1, wherein, when the first distributed power source is in an autonomous operation state and a power supply to the first distributed power source is required, the first distributed power source is charged with power obtained by subtracting the power consumed by the load from the power output by the second distributed power source.

11. The first power control device 11. The power control system according to claim 1, wherein the voltage in the power transmission line connected to the load is controlled within an output voltage range in which an overload protection function and an overvoltage protection function do not operate.

12. A power control system capable of supplying power output from a first distributed power source and a second distributed power source to a load during isolated operation when the first distributed power source is disconnected from a grid, comprising: a power control device that controls the power output from the first distributed power source, The power control device has a function of independent operation output, The power control device, during stand-alone operation, a second power control device that controls the power output by the second distributed power source sets a predetermined output power so that an islanding operation prevention function that prevents islanding operation of the second distributed power source does not operate; and a power control device that causes the first distributed power source to output power or causes the first distributed power source to consume power;

13. 1. A power control method for controlling power output by a first distributed power source in a power control system capable of supplying power output from a first distributed power source and a second distributed power source to a load during isolated operation in which the first distributed power source and the second distributed power source are disconnected from a grid, comprising: During autonomous operation, a second power control device that controls the power output by the second distributed power source sets a predetermined output power so that an islanding operation prevention function that prevents islanding operation of the second distributed power source does not operate; and A power control method for causing the first distributed power source to output power or for causing the first distributed power source to consume power.

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