Power system and control device

Abstract

To provide a power system and a control device capable of more effectively utilizing power generated by a power generation facility.SOLUTION: The power system includes a relay positioned between a commercial power grid for supplying a first voltage, and a transformer that converts the first voltage supplied from the commercial power grid to a second voltage lower than the first voltage and supplies it to a load, a first power conditioner connected to a storage battery, and a second power conditioner connected to a power generation facility. Upon detecting a power outage in the commercial power grid, the relay transmits a power outage notification to both the first power conditioner and the second power conditioner. Upon receiving the power outage notification, the first power conditioner supplies power from the storage battery to the load. Upon receiving the power outage notification, the second power conditioner stops its output. When it receives the power outage notification and detects power being supplied to the load from the first power conditioner, it outputs the power generated by the power generation facility.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Distributed power sources such as photovoltaic power generation systems that are interconnected with commercial power grids are being used (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-193865 Summary of the Invention [Problem to be solved by the invention]

[0004] There are contracts for receiving high voltage power (e.g., 6600V) from a commercial power grid. In the case of receiving high voltage power, the received high voltage is transformed to a specified voltage (e.g., 100V) using a transformer and then supplied to a load. In this type of high voltage power receiving, when operating a power system that uses both a first power conditioner that supplies power from a storage battery and a second self-consumption power conditioner that supplies power generated by a solar cell, the first and second power conditioners are connected closer to the load than the transformer.

[0005] When the commercial power grid experiences a power outage, the first and second power conditioners stop outputting power. The first power conditioner then begins independent operation, disconnected from the commercial power grid, and begins supplying power from the storage battery to the load.

[0006] The second power conditioner cannot detect power outages in the commercial power grid by monitoring the circuit because the output from the first power conditioner generates voltage in the circuit to the load. Furthermore, because the second power conditioner is a self-consumption type, restarting output after it has been stopped to prevent reverse power flow must be carried out by a qualified person, such as a chief electrical engineer, in cooperation with the power company. Therefore, it takes time to restore the power from the solar panels after a power outage. Thus, when the commercial power grid experiences a power outage, the power generated by the solar panels cannot be effectively utilized.

[0007] An object of one aspect of the disclosed technology is to provide a power system and a control device that can more effectively utilize power generated by a power generation facility. [Means for solving the problem]

[0008] One aspect of the disclosed technology is exemplified by the following power system. The power system includes: a transformer disposed between a commercial power system and a load, which converts a first voltage supplied from the commercial power system into a second voltage lower than the first voltage and supplies the second voltage to the load; a relay disposed between the commercial power system and the transformer; a first power conditioner connected to the load and a storage battery; a second power conditioner disposed between the first power conditioner and the load, which is connected to a power generation facility; and a switch which connects the first power conditioner to the transformer while the commercial power system is supplying power and which disconnects the first power conditioner from the transformer while the commercial power system is experiencing a power outage. When the relay detects a power outage in the commercial power system, it disconnects an electric circuit connecting the commercial power system and the transformer and transmits a power outage notification to the first power conditioner and the second power conditioner. The first power conditioner stops output when it receives the power outage notification, and then starts outputting power from the storage battery while being disconnected from the commercial power grid by the switch. The second power conditioner stops output when it receives the power outage notification, and starts outputting power generated by the power generation facility when it receives the power outage notification and detects power supply from the first power conditioner to the load.

[0009] In this power system, when the power outage notification is received and the first power conditioner is outputting, the second power conditioner starts outputting. Here, when the power outage notification is received and the first power conditioner is outputting, disconnecting the electric circuit does not cause reverse power flow of the output of the second power conditioner. Therefore, in this power system, by starting the output of the second power conditioner, which was once stopped by the power outage notification, it is possible to more effectively utilize the power generated by the power generation facility.

[0010] The power system may further include the following feature. The relay detects reverse power occurring between the commercial power system and the transformer, determines output power to be output by the first power conditioner and the second power conditioner based on the detected reverse power, and notifies the first power conditioner and the second power conditioner of the determined output power. The first power conditioner and the second power conditioner then control their output according to the notified output power. A power system including these features allows the first power conditioner and the second power conditioner to continue outputting power while suppressing reverse power flow.

[0011] The power system may further include the following feature. When the second power conditioner receives the power outage notification and detects the supply of power from the first power conditioner to the load, the first power conditioner outputs the maximum power output within a range in which the storage battery can be charged, regardless of the output power notified by the relay. As described above, in a state in which the power outage notification is received and the supply of power from the first power conditioner to the load is detected, there is no need to worry about reverse power flow. Therefore, even if the output of the second power conditioner becomes the maximum within a range in which the first power conditioner can charge the storage battery, reverse power flow does not occur. A power system including these features can more effectively utilize the power generated by the power generation facility during a power outage in the commercial power grid.

[0012] The disclosed technology can also be understood from the perspective of a control device. The control device controls the first and second power conditioners of a power system including: a commercial power system that supplies a first voltage; a relay that is arranged between a transformer that converts the first voltage supplied from the commercial power system into a second voltage that is lower than the first voltage and supplies the second voltage to a load; a first power conditioner that is connected to the load and a storage battery; a second power conditioner that is arranged between the first power conditioner and the load and to which a power generation facility is connected; and a switch that connects the first power conditioner to the transformer while the commercial power system is supplying power and disconnects the first power conditioner from the transformer while the commercial power system is experiencing a power outage. When the control device receives a power outage notification from the relay that has detected a power outage in the commercial power system, the control device transmits an output stop instruction to the first power conditioner and the second power conditioner to stop the output of the first power conditioner and the second power conditioner, and after the output stop in response to the output stop instruction, when the control device detects that the first power conditioner has started outputting power from the storage battery in a state where the first power conditioner is separated from the commercial power system by the switch, the control device transmits an output start instruction to the second power conditioner to start outputting power generated by the power generation facility. .

[0013] When the power outage notification is received and the first power conditioner is outputting, disconnecting the electric circuit prevents reverse power flow of the output of the second power conditioner. In such a case, the control device can cause the second power conditioner to start outputting. Therefore, by starting the output of the second power conditioner, which was once stopped by the power outage notification, the control device can more effectively utilize the power generated by the power generation facility. [Effects of the Invention]

[0014] According to the disclosed technology, the electric power generated by the power generation facility can be utilized more effectively. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram illustrating an example of a high-voltage interconnected power system according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of a hardware configuration of a protective relay and a power conditioner according to the embodiment. [Figure 3] FIG. 3 is a diagram illustrating an example of a processing block of a protective relay according to an embodiment. [Figure 4] FIG. 4 is a diagram illustrating an example of a processing block of the power conditioner according to the embodiment. [Figure 5] FIG. 5 is a diagram illustrating an example of a processing block of the power conditioner according to the embodiment. [Figure 6] FIG. 6 is a diagram showing an example of a processing sequence of the high-voltage interconnected power system. [Figure 7] FIG. 7 is a diagram schematically illustrating the operating state of the power conditioner according to the presence or absence of power supply from the power grid in the embodiment. [Figure 8] FIG. 8 is a diagram showing an example of a high-voltage interconnected power system according to a first modification. [Figure 9] FIG. 9 is a diagram showing an example of a processing block of a protective relay according to a first modified example. [Figure 10] FIG. 10 is a diagram illustrating an example of a processing block of a power conditioner according to a first modified example. [Figure 11] FIG. 11 is a diagram illustrating an example of a processing block of a power conditioner according to a first modified example. [Figure 12] FIG. 12 is a diagram showing an example of a high-voltage interconnected power system according to a second modification. DETAILED DESCRIPTION OF THE INVENTION

[0016] <Application example> An application example of the present invention will be described. An example of this application example is a high-voltage grid-connected power system 100 illustrated in FIG. 1. The high-voltage grid-connected power system 100 converts high voltage supplied by a power system 1 into low voltage using a transformer 3 and supplies the low voltage to a load 5. In the high-voltage grid-connected power system 100, power conditioners 6 and 7 are arranged between the transformer 3 and the load 5. A storage battery 8 is connected to the power conditioner 6, and a solar cell string 9 is connected to the power conditioner 7. The high-voltage grid-connected power system 100 is provided with a switch that connects the power conditioner 6 to the transformer 3 while the power system 1 is supplying power, and that disconnects the power conditioner 6 from the transformer 3 while the power system 1 is experiencing a power outage.

[0017] A protective relay 2 is disposed between the power grid 1 and the transformer 3. When the protective relay 2 detects a power outage in the power grid 1, it disconnects the electric circuit PL1 connecting the power grid 1 and the transformer 3 and sends a power outage notification to the power conditioners 6 and 7.

[0018] Upon receiving the power outage notification, power conditioner 6 stops output and then starts output in standalone operation. At this time, the power conditioner 6 is in a state of being separated from the power grid 1 by the protective relay 2 and the automatic switching circuit 4.

[0019] Upon receiving the power outage notification, the power conditioner 7 stops output. Then, when the power conditioner 7 receives the power outage notification and detects that the power conditioner 6 is operating in an isolated mode, it starts output. When the power outage notification is received and the power conditioner 6 is operating in an isolated mode, the output of the power conditioner 7 does not flow reversely, so the power conditioner 7 can start outputting. Since the power conditioner 7 starts outputting in this mode, the high-voltage grid-connected power system 100 can more effectively utilize the power generated by the photovoltaic string 9.

[0020] <Embodiment> Hereinafter, an embodiment will be described with reference to the drawings. Fig. 1 is a diagram showing an example of a high-voltage grid-connected power system 100 according to an embodiment. The high-voltage grid-connected power system 100 is a system in which a consumer having a load 5 receives and uses high-voltage power supplied from a power system 1. Examples of the consumer having the load 5 include a store, a factory, etc.

[0021] The high-voltage interconnected power system 100 includes a power system 1, a protective relay 2, a transformer 3, an automatic transfer circuit 4, a load 5, and power conditioners 6 and 7. In the high-voltage interconnected power system 100, the protective relay 2, the transformer 3, the automatic transfer circuit 4, the load 5, the power conditioner 6, the power conditioner 7, the storage battery 8, and the solar cell string 9 are consumer equipment having the load 5. The power system 1 and the transformer 3 are connected by an electric circuit PL1, and the protective relay 2 is disposed on the electric circuit PL1. The transformer 3 and the automatic transfer circuit 4 are connected by an electric circuit PL2. The automatic transfer circuit 4, the load 5, and the power conditioners 6 and 7 are connected by an electric circuit PL3. The protective relay 2 and the power conditioners 6 and 7 are also connected by a signal line SL1.

[0022] The power system 1 is, for example, a commercial power system operated by a power company. The power system 1 supplies power generated by a power plant to a load 5.

[0023] The protective relay 2 is a device that detects short-circuit faults, ground faults, etc., and isolates the transformer 3, automatic transfer circuit 4, load 5, and power conditioners 6 and 7 from the power grid 1. When the protective relay 2 detects a power outage in the power grid 1, it sends a power outage notification to the power conditioners 6 and 7 via signal line SL1. Furthermore, the protective relay 2 monitors reverse power flow, and when it detects reverse power flow, it sends an output stop instruction to the power conditioners 6 and 7 by a Reverse Power Relay (RPR) signal via signal line SL1. In the high-voltage interconnected power system 100, the switching point between the equipment of the power grid 1 and the equipment of a customer having a load 5 is on the high-voltage side (high-voltage circuit 110 side) of the transformer 3, so the protective relay 2 is placed between the power grid 1 and the transformer 3.

[0024] The transformer 3 transforms high-voltage power (e.g., 6600V) supplied from the power grid 1 into low-voltage power (e.g., 200V or 100V) to be used by the load 5. In the high-voltage interconnected power system 100, the side of the power grid 1 from the transformer 3 becomes a high-voltage circuit 110 to which high-voltage power is applied, and the side of the load 5 from the transformer 3 becomes a low-voltage circuit 120 to which low-voltage power is applied. The power grid 1 and the transformer 3 are connected by an electric circuit PL1, and the protective relay 2 is arranged on the electric circuit PL1.

[0025] The automatic switching circuit 4 is a circuit that switches the source of power supply to the load 5 between the power grid 1 and the power conditioner 6. The automatic switching circuit 4 has a contact 41 connected to the power grid 1 side and a contact 42 connected to the power conditioner 6 side. While power is being supplied from the power grid 1, the automatic switching circuit 4 switches to the contact 41 side, and is supplied to the load 5. Furthermore, when the power supply from the power grid 1 is interrupted, the automatic switching circuit 4 switches to the contact 42 side, so that the power from the power conditioner 6 is supplied to the load 5.

[0026] The load 5 is an electrical device that operates by consuming supplied power. Examples of the load 5 include an air conditioner, a refrigerator, a lighting fixture, a motor device, a robot, and a computer system.

[0027] The power conditioner 6 converts DC power from the storage battery 8 into AC power and outputs it. The DC power stored in the storage battery 8 is converted into AC power by the power conditioner 6 and supplied to the load 5. The power conditioner 6 is connected to PL2 by an electric circuit PL21. The power conditioner 6 is also connected to a contact 42 of the automatic switching circuit 4 by an electric circuit PL31. When the automatic switching circuit 4 is switched to the contact 41 side, the power conditioner 6 is connected to the power grid 1. The output of power by the power conditioner 6 connected to the power grid 1 is called grid-connected operation. When the automatic switching circuit 4 is switched to the contact 42 side, the power conditioner 6 is disconnected from the power grid 1. The output of power by the power conditioner 6 disconnected from the power grid 1 is called isolated operation.

[0028] The power conditioner 7 converts DC power from the photovoltaic string 9 into AC power and outputs it. The DC power generated by the photovoltaic string 9 is converted into AC power by the power conditioner 7 and input to the power conditioner 6, and the storage battery 8 is charged via the power conditioner 6. The power conditioner 7 is connected to the electric circuit PL3 ​​by the electric circuit PL32.

[0029] Here, the power conditioner 7 is a total self-consumption type power conditioner. In other words, reverse power flow from the power conditioner 7 to the high-voltage circuit 110 is not permitted. Therefore, when the protective relay 2 detects reverse power flow, the power conditioner 7 receives an output stop instruction by an RPR signal from the protective relay 2 that detected the reverse power flow. Upon receiving the output stop instruction, the power conditioner 7 stops the output of power from the photovoltaic string 9.

[0030] Furthermore, when power outage notification is received from protective relay 2, power conditioners 6 and 7 stop outputting power. After that, power conditioner 6 switches to stand-alone operation and resumes power output. On the other hand, power conditioner 7, which is a total self-consumption type power conditioner, does not automatically resume output. Therefore, when power conditioner 6 is operating stand-alone, it is no longer possible to charge storage battery 8 with power generated by photovoltaic string 9.

[0031] In this embodiment, the following configuration is adopted so that the storage battery 8 can be charged with the power generated by the photovoltaic string 9 even when the power conditioner 6 is operating independently.

[0032] <Hardware configuration> 2 is a diagram illustrating an example of the hardware configuration of the protective relay 2, the power conditioner 6, and the power conditioner 7 according to the embodiment. The protective relay 2 includes a CPU 21, a main memory unit 22, an auxiliary memory unit 23, a communication unit 24, and a connection bus B1. The CPU 21, the main memory unit 22, the auxiliary memory unit 23, and the communication unit 24 are interconnected by the connection bus B1.

[0033] CPU21 is also called a microprocessor unit (MPU) or processor. At least some of the processing performed by the CPU 21 may be performed by an integrated circuit (IC) or other digital circuit. Integrated circuits include large-scale integrated circuits (LSIs), application-specific integrated circuits (ASICs), and programmable logic devices (PLDs). PLDs include, for example, field-programmable gate arrays (FPGAs). The CPU 21 may be a combination of a processor and an integrated circuit. This combination is called, for example, a microcontroller unit (MCU), a system-on-a-chip (SoC), a system LSI, or a chipset. In the protective relay 2, the CPU 21 loads a program stored in the auxiliary memory 23 into the working area of ​​the main memory 22 and controls peripheral devices through the execution of the program. This allows the protective relay 2 to perform processing consistent with a predetermined purpose. The main memory 22 and the auxiliary memory 23 are recording media readable by the CPU 21.

[0034] The main storage unit 22 is exemplified as a storage unit that is directly accessed by the CPU 21. The main storage unit 22 includes a random access memory (RAM) and a read only memory (ROM).

[0035] The auxiliary storage unit 23 stores various programs and various data in a readable and writable recording medium. The auxiliary storage unit 23 is also called an external storage device. The auxiliary storage unit 23 is, for example, an erasable programmable ROM (EPROM), a solid state drive (SSD), or the like.

[0036] The communication unit 24 is, for example, an interface with the signal line SL1, and communicates with an external device via the signal line SL1.

[0037] The power conditioner 6 includes a CPU 61, a main memory 62, an auxiliary memory 63, a communication unit 64, a first connection unit 65, a second connection unit 66, a third connection unit 67, and a connection bus B6. The CPU 61, the main memory 62, the auxiliary memory 63, the communication unit 64, and the connection bus B6 are similar to the CPU 21, the main memory 22, the auxiliary memory 23, the communication unit 24, and the connection bus B1 of the protective relay 2, and therefore their description will be omitted. The first connection unit 65 is an interface that connects to the storage battery 8. The power conditioner 6 exchanges power with the storage battery 8 via the first connection unit 65. The second connection unit 66 is a connector to which the electric circuit PL21 is connected. The third connection unit 67 is a connector to which the electric circuit PL31 is connected.

[0038] The power conditioner 7 includes a CPU 71, a main memory 72, an auxiliary memory 73, a communication unit 74, a first connection unit 75, a second connection unit 76, a third connection unit 77, and a connection bus B7. The CPU 71, the main memory 72, the auxiliary memory 73, the communication unit 74, and the connection bus B7 are similar to the CPU 21, the main memory 22, the auxiliary memory 23, the communication unit 24, and the connection bus B1 of the protective relay 2, and therefore their description will be omitted. The first connection unit 75 is an interface that connects the photovoltaic string 9. The power conditioner 7 receives power generated by the photovoltaic string 9 via the first connection unit 75. The second connection unit 76 is a connector to which the electric circuit PL32 is connected.

[0039] <Protective relay 2 processing block> 3 is a diagram showing an example of a processing block of the protective relay 2 according to the embodiment. The protective relay 2 includes a power measurement unit 201, a reverse power determination unit 202, and a power outage determination unit 203. The protective relay 2 executes the processes of each unit of the protective relay 2, such as the power measurement unit 201, the reverse power determination unit 202, and the power outage determination unit 203, by the CPU 21 executing a computer program deployed in an executable manner in the main memory unit 22.

[0040] The power measurement unit 201 measures the power flowing through the electrical line PL1.

[0041] The reverse power determination unit 202 determines whether or not there is power flowing backward from the low-voltage circuit 120 to the power grid 1. The reverse power determination unit 202 detects the backward flow, for example, based on the power measured by the power measurement unit 201. When the reverse power determination unit 202 detects the backward flow, it sends an output stop instruction to the power conditioners 6 and 7, for example, by an RPR signal via the signal line SL1.

[0042] The power outage determination unit 203 determines a power outage in the power grid 1. The power outage determination unit 203 determines a power outage in the power grid 1, for example, based on the power measured by the power measurement unit 201. When the power outage determination unit 203 determines that the power grid 1 has experienced a power outage, it sends a power outage notification to the power conditioners 6 and 7 notifying them that a power outage has occurred in the power grid 1. Furthermore, when the power outage determination unit 203 detects a power outage, it may, for example, drive the relay of the protective relay 2 to cut off the electric circuit PL1. Furthermore, when the power outage determination unit 203 detects, based on the power measured by the power measurement unit 201, that the power grid 1 has started to supply power after the power outage (hereinafter also referred to as power restoration), it sends a power restoration notification to the power conditioners 6 and 7 notifying them that power has been restored in the power grid 1.

[0043] <Power conditioner 6 processing block> 4 is a diagram showing an example of a processing block of the power conditioner 6 according to the embodiment. The power conditioner 6 includes a power outage determination unit 601 and an output control unit 602. The power conditioner 6 executes the processes of each unit of the power conditioner 6, such as the power outage determination unit 601 and the output control unit 602, by the CPU 61 executing a computer program deployed in an executable manner in the main memory unit 62.

[0044] When the power outage determination unit 601 receives a power outage notification from the protective relay 2, it determines that a power outage has occurred in the power system 1.

[0045] When the output control unit 602 receives an output stop command from the protective relay 2, it stops the output of the power conditioner 6. When the power outage determination unit 601 determines that a power outage has occurred, the output control unit 602 stops the output of the power conditioner 6 and then starts the output of the power conditioner 6 in stand-alone operation. When the output control unit 602 receives a power restoration notification from the protective relay 2, it stops the output of the power conditioner 6 and then starts the output of the power conditioner 6 in grid-connected operation.

[0046] 5 is a diagram showing an example of a processing block of the power conditioner 7 according to the embodiment. The power conditioner 7 includes an independent operation determination unit 701 and an output control unit 702. The power conditioner 7 executes the processes of each unit of the power conditioner 7, such as the independent operation determination unit 701 and the output control unit 702, by the CPU 71 executing a computer program deployed in an executable manner in the main memory unit 72.

[0047] The isolated operation determination unit 701 determines whether the power conditioner 6 is operating in an isolated manner. The isolated operation determination unit 701 monitors, for example, the current in the electric circuit PL3. Then, when the isolated operation determination unit 701 receives a power outage notification from the protective relay 2 and current is flowing in the electric circuit PL3, it determines that the power conditioner 6 is operating in an isolated manner. When the isolated operation determination unit 701 receives a power outage notification from the protective relay 2 and current is not flowing in the electric circuit PL3, it determines that the power conditioner 6 is not operating in an isolated manner. The isolated operation determination unit 701 also determines that the power conditioner 6 is not operating in an isolated manner when it does not receive a power outage notification from the protective relay 2.

[0048] When the output control unit 702 receives an output stop command from the protective relay 2, it stops the output of the power conditioner 6. Then, the output control unit 702 stops the output of the power conditioner 6 when the power conditioner 6 is in an autonomous state. When the isolated operation determination unit 701 determines that the power conditioner 6 is operating, the power conditioner 7 starts outputting electricity. That is, when the power conditioner 6 is operating in an isolated mode, the power conditioner 7 outputs the power generated by the photovoltaic string 9 to the electric circuit PL3. When the power conditioner 6 is operating in an isolated mode, the output of the power conditioner 7 does not flow back to the electric power grid 1. Therefore, when the isolated operation determination unit 701 determines that the power conditioner 6 is operating in an isolated mode, the output control unit 702 may maximize the output of the power conditioner 7. Here, the maximum output of the power conditioner 7 may be, for example, the maximum within the range in which the power conditioner 6 can charge the storage battery 8. The chargeable power range is notified, for example, from the power conditioner 6 to the power conditioner 7 via a predetermined communication cable or the like.

[0049] <Processing flow> Fig. 6 is a diagram showing an example of a processing sequence of the high-voltage interconnected power system 100. Fig. 6 illustrates a processing sequence of the protective relay 2 and the power conditioners 6 and 7 when a power outage occurs in the power system 1. Hereinafter, an example of the processing sequence of the high-voltage interconnected power system 100 will be described with reference to Fig. 6.

[0050] In step S1, the power outage determination unit 203 of the protective relay 2 detects a power outage in the power grid 1. In step S2, the power outage determination unit 203 of the protective relay 2 sends a power outage notification to the power conditioner 6. In step S3, the power outage determination unit 203 of the protective relay 2 sends a power outage notification to the power conditioner 7.

[0051] In step S4, the power outage determination unit 601 of the power conditioner 6 determines that a power outage has occurred in the power grid 1 based on the power outage notification received in step S2. The output control unit 602 of the power conditioner 6 stops the output of the power conditioner 6.

[0052] In step S5, the isolated operation determination unit 701 of the power conditioner 7 determines that a power outage has occurred in the power grid 1 based on the power outage notification received in step S3. The output control unit 702 of the power conditioner 7 stops the output of the power conditioner 7.

[0053] In step S6, the output control unit 602 of the power conditioner 6 starts the output of the power conditioner 6 in stand-alone operation.

[0054] In step S7, the isolated operation determination unit 701 of the power conditioner 7 determines whether the power conditioner 6 is in isolated operation. In step S8, the output control unit 702 of the power conditioner 7 starts output of the power conditioner 7 when it is determined in step S7 that the power conditioner 6 is in isolated operation.

[0055] In step S9, the power outage determination unit 203 of the protective relay 2 detects the restoration of power to the power grid 1. In step S10, the power outage determination unit 203 of the protective relay 2 sends a power restoration notification to the power conditioner 6. In step S11, the power outage determination unit 203 of the protective relay 2 sends a power restoration notification to the power conditioner 7.

[0056] In step S12, the output control unit 602 of the power conditioner 6 that received the power restoration notification in step S10 stops the output of the power conditioner 6. In step S13, the output control unit 702 of the power conditioner 7 that received the power restoration notification in step S11 stops the output of the power conditioner 7.

[0057] In step S14, the output control unit 602 of the power conditioner 6 starts the output of the power conditioner 6 in grid-connected operation.

[0058] In step S15, a qualified person such as a chief electrical engineer starts output of the power conditioner 7 in cooperation with the power company of the power system 1. That is, the start of output of the power conditioner 7 after power restoration is performed manually by an operator.

[0059] <Operating status of power conditioners 6 and 7> Fig. 7 is a diagram schematically illustrating the operating states of the power conditioners 6 and 7 according to the presence or absence of power supply from the power grid 1 in the embodiment. Hereinafter, the operating states of the power conditioners 6 and 7 according to the presence or absence of power supply from the power grid 1 will be described with reference to Fig. 6.

[0060] During period T1, power is normally supplied from power grid 1. Therefore, power conditioner 6 operates in grid-connected mode, and power conditioner 7 operates in self-consumption mode. The power supply source for load 5 during period T1 is power grid 1.

[0061] During period T2, the power grid 1 experiences a power outage. Therefore, the power conditioner 6 stops outputting and then starts independent operation. After stopping outputting, the power conditioner 7 checks whether the power conditioner 6 is operating independently. After checking whether the power conditioner 6 is operating independently, the power conditioner 7 starts outputting. For example, the storage battery 8 connected to the power conditioner 6 is charged by the output of the power conditioner 7. There is a power outage during the beginning of period T2, and after the power conditioner 6 starts operating independently, power is supplied to the load 5 from the power conditioner 6.

[0062] In period T3, power is restored to power grid 1. Therefore, power conditioner 6 stops output and then starts grid-connected operation. After power conditioner 7 stops output, a qualified person such as a chief electrical engineer works with the power company of power grid 1 to start output from power conditioner 7. The output from power conditioner 7 is consumed by the power grid. There is a power outage at the beginning of period T3, and after that, power is supplied to load 5 from power grid 1.

[0063] <Effects of the embodiment> In the high-voltage interconnected power system 100, when the power grid 1 experiences a power outage, the power conditioner 6 starts independent operation. When the power conditioner 6 starts independent operation, the current output by the power conditioner 6 flows through the electric circuit PL3. Because a current flows through the electric circuit PL3 ​​even during a power outage in the power grid 1, the power conditioner 7 cannot detect a power outage in the power grid 1 based on the presence or absence of a current in the electric circuit PL3.

[0064] In this embodiment, the protective relay 2 arranged on the electric circuit PL1 of the high-voltage circuit 110 detects a power outage in the power grid 1 and sends a power outage notification to the power conditioners 6 and 7. Therefore, the power conditioner 7 can detect a power outage in the power grid 1.

[0065] Then, when the power conditioner 7 receives a power outage notification from the protective relay 2 and detects that a current is flowing in the electric circuit PL3, it determines that the power conditioner 6 is in independent operation. When the power conditioner 7 determines that the power conditioner 6 is in independent operation, it starts outputting the power generated by the photovoltaic string 9. When the power conditioner 6 is in independent operation, the low-voltage circuit 120 is separated from the power grid 1 by the protective relay 2. Therefore, even if the power conditioner 7 starts output, the output of the power conditioner 7 does not flow reversely. Therefore, the high-voltage grid-connected power system 100 according to this embodiment can more effectively utilize the power of the photovoltaic string 9 during a power outage without causing a reverse power flow.

[0066] <First Modification> In the embodiment described above, the protective relay 2 does not notify the power conditioners 6, 7 of how much output to provide. In the first modified example, a configuration will be described in which the protective relay 2 determines the output of the power conditioners 6, 7, and notifies the determined output to the power conditioners 6, 7. Components common to the embodiment will be assigned the same reference numerals, and descriptions thereof will be omitted. Below, the first modified example will be described with reference to the drawings.

[0067] 8 is a diagram showing an example of a high-voltage interconnected power system 100A according to a first modified example. The high-voltage interconnected power system 100A differs from the high-voltage interconnected power system 100 according to the embodiment in that it includes a protective relay 2A instead of the protective relay 2, and power conditioners 6A and 7A instead of the power conditioners 6 and 7.

[0068] 9 is a diagram showing an example of a processing block of a protective relay 2A according to Modification 1. The protective relay 2A differs from the protective relay 2 according to the embodiment in that it further includes a self-consumption control unit 204.

[0069] The self-consumption control unit 204 detects reverse power on the electric line PL1 and, based on the detected reverse power, determines the output power to be output from the power conditioners 6 and 7. The self-consumption control unit 204 notifies the power conditioners 6A and 7A of the determined output power.

[0070] 10 is a diagram showing an example of a processing block of a power conditioner 6A according to the first modification. The power conditioner 6A differs from the power conditioner 6 according to the embodiment in that it includes an output control unit 602A instead of the output control unit 602. The output control unit 602A controls the output of the power conditioner 6A in response to an output notification from the self-consumption control unit 204 of the protective relay 2.

[0071] 11 is a diagram showing an example of a processing block of a power conditioner 7A according to Modification 1. The power conditioner 7A differs from the power conditioner 7 according to the embodiment in that it includes an output control unit 702A instead of the output control unit 702.

[0072] The output control unit 702A controls the output of the power conditioner 7 in accordance with the output notification from the self-consumption control unit 204 of the protective relay 2. When the independent operation determination unit 701 determines that the power conditioner 6A is operating independently, the output control unit 702A maximizes the output of the power conditioner 7A regardless of the output specified by the output notification from the self-consumption control unit 204.

[0073] According to the first modification, the output is notified from the protective relay 2, so the outputs of the power conditioners 6A and 7A are controlled so as to prevent reverse power flow from the power conditioner 7A. Furthermore, when the power conditioner 6A is operating independently, the output of the power conditioner 7A does not cause reverse power flow, so the power conditioner 7A outputs at maximum power regardless of the output notified from the protective relay 2. Therefore, according to the first modification, the power generated by the photovoltaic string 9 can be used more effectively.

[0074] <Second Modification> In the embodiment described above, the power conditioner 7 determines whether the power conditioner 6 is operating autonomously. In the second modification, a configuration will be described in which a control device connected to the power conditioners 6, 7 determines whether the power conditioner 6 is operating autonomously. Components common to the embodiment will be assigned the same reference numerals, and descriptions thereof will be omitted. The second modification will be described below with reference to the drawings.

[0075] 12 is a diagram showing an example of a high-voltage interconnected power system 100B according to a second modification. The high-voltage interconnected power system 100B differs from the high-voltage interconnected power system 100 according to the embodiment in that it includes a power conditioner 6B instead of the power conditioner 6, a power conditioner 7B instead of the power conditioner 7, and further includes a control device 10.

[0076] The control device 10 and the protective relay 2 are connected by a signal line SL1A. The control device 10 and the power conditioner 6B are connected by a signal line SL2. The control device 10 and the power conditioner 7B are connected by a signal line SL3. The control device 10 is also connected to an ammeter 11 arranged on an electrical path PL3.

[0077] The control device 10 is an information processing device that controls the power conditioners 6B and 7B in accordance with instructions from the protective relay 2 and a current value measured by an ammeter 11.

[0078] The power conditioner 6B differs from the power conditioner 6 according to the embodiment in that the output is controlled in response to an instruction from the control device 10. The power conditioner 7B also differs from the power conditioner 7 according to the embodiment in that the output is controlled in response to an instruction from the control device 10 and in that the power conditioner 7B does not determine whether the power conditioner 6 is operating autonomously.

[0079] When the control device 10 receives a power outage notification from the protective relay 2, it instructs the power conditioners 6B and 7B to stop output. Upon receiving the output stop instruction from the control device 10, the power conditioners 6B and 7B stop output.

[0080] The power conditioner 6B starts outputting in an independent operation. Note that the power conditioner 6B may start outputting in an independent operation after receiving an output start instruction from the control device 10.

[0081] The control device 10 also determines whether the power conditioner 6B is operating in an autonomous mode. The control device 10 monitors, for example, the current value measured by the ammeter 11. When the control device 10 receives a power outage notification from the protective relay 2 and a current is flowing through the electric circuit PL3, the control device 10 determines that the power conditioner 6B is operating in an autonomous mode.

[0082] When the control device 10 determines that the power conditioner 6B is operating autonomously, it sends an output start instruction to the power conditioner 7B. Upon receiving the output start instruction from the control device 10, the power conditioner 7B starts output.

[0083] According to the second modification, the output of the power conditioner 7B can be started during a power outage even if the power conditioner 7B does not determine whether the power conditioner 6B is operating in an autonomous mode. In other words, according to the second modification, it is possible to more effectively utilize the power generated by the photovoltaic string 9 connected to the power conditioner 7B, which cannot determine whether the power conditioner 6B is operating in an autonomous mode.

[0084] <Other variations> In the embodiment described above, the solar cell string 9 is connected to the power conditioner 7, but the power generation equipment connected to the power conditioner 7 is not limited to the solar cell string 9. Examples of the power generation equipment connected to the power conditioner 7 include a wind power generation system, a fuel cell, and the like.

[0085] <Appendix 1> a commercial power system (1) that supplies a first voltage; a relay (2, 2A) disposed between the transformer (3) that converts the first voltage into a second voltage lower than the first voltage and supplies the second voltage to a load; a first power conditioner (6, 6A) connected to the load (5) and a storage battery (8); a second power conditioner (7, 7A) disposed between the first power conditioner (6, 6A) and the load (5) and connected to a power generation facility (9); a switch (4) that connects the first power conditioner (6, 6A) to the transformer (3) while the commercial power system (1) is supplying power, and that disconnects the first power conditioner (6, 6A) from the transformer (3) while the commercial power system is experiencing a power outage; When the relay (2, 2A) detects a power outage in the commercial power system (1), it disconnects an electric circuit (PL1) connecting the commercial power system (1) and the transformer (3) and transmits a power outage notification to the first power conditioner (6, 6A) and the second power conditioner (7, 7A); the first power conditioner (6, 6A) stops output when receiving the power outage notification, and then starts outputting power from the storage battery (8) while being disconnected from the commercial power grid (1) by the switch (4); The second power conditioner (7, 7A) stops output when it receives the power outage notification, and starts outputting the power generated by the power generation facility (9) when it receives the power outage notification and detects power supply from the first power conditioner (6, 6A) to the load (5). Power system (100, 100A). <Appendix 2> The relay (2A) Detecting reverse power occurring between the commercial power system (1) and the transformer (3); determining output power to be output from the first power conditioner (6A) and the second power conditioner (7A) based on the detected reverse power; notifying the first power conditioner (6A) and the second power conditioner (7A) of the determined output power; The first power conditioner (6A) and the second power conditioner (7A) control outputs according to the notified output power. 10. The power system (100A) of claim 1. <Appendix 3> The second power conditioner (7A) When the power outage notification is received and the supply of power from the first power conditioner (6A) to the load (5) is detected, the first power conditioner outputs a maximum output of power within a range in which the storage battery can be charged, regardless of the output power notified from the relay (2A). 1. The power system (100A) of claim 2. <Appendix 4> a relay (2) arranged between a commercial power system (1) that supplies a first voltage, a transformer (3) that converts the first voltage supplied from the commercial power system (1) into a second voltage lower than the first voltage and supplies the second voltage to a load (5); a first power conditioner (6B) connected to the load (5) and a storage battery (8); a second power conditioner (7B) arranged between the first power conditioner (6) and the load (5) and connected to a power generation facility (9); and a switch (4) that connects the first power conditioner (6B) to the transformer (3) while the commercial power system (1) is supplying power and disconnects the first power conditioner (6B) from the transformer (3) while the commercial power system (1) is experiencing a power outage; And, When receiving a power outage notification from the relay (2) that has detected a power outage in the commercial power system (1), the power conditioner (1) transmits an output stop instruction to the first power conditioner (6B) and the second power conditioner (7B) to stop output of the first power conditioner (6B) and the second power conditioner (7B); After the output is stopped in response to the output stop instruction, when it is detected that the first power conditioner (6B) has started outputting power from the storage battery (8) in a state in which the storage battery (8) is disconnected from the commercial power grid (1) by the switch (4), an output start instruction for starting output of power generated by the power generation facility (9) is transmitted to the second power conditioner (7B). Control device (10). [Explanation of symbols]

[0086] 1...Power system 2. Protective relay 2A Protective Relay 3. Transformer 4. Automatic switching circuit 5. Load 6. Power conditioner 6A Power Conditioner 7. Power conditioner 7A Power Conditioner 8. Storage battery 9. Solar cell string 10. Control device 11...Ammeter 21 CPU 22...Main memory 23...Auxiliary storage section 24. Communications Department 61 CPU 62...Main memory 63...Auxiliary storage section 64 Communications Department 65··First connection part 66··Second connection part 67··Third connection part 71 CPU 72...Main memory 73...Auxiliary storage section 74. Communications Department 75··First connection part 76··Second connection part 41. Contact 42 Contacts 100··High-voltage interconnected power system 100A High-voltage grid-connected power system 100B High-voltage interconnected power system 110 High-voltage circuit 120 Low-voltage circuit 201 Power measurement unit 202...Reverse power determination section 203...Power outage determination section 204··Self-Consumption Control Unit 601...Power outage determination section 602 Output control section 602A··Output control section 701: Autonomous operation determination unit 702 Output control section 702A Output control section B1 Connecting bus B6··Connecting bus B7··Connecting bus PL1·Electric circuit PL2 Circuit PL3 Circuit PL4 Circuit PL21 Circuit PL31 Circuit PL32 Circuit SL1··Signal line SL1A··Signal cable SL2··Signal cable SL3 signal line

Claims

1. a relay disposed between a commercial power system that supplies a first voltage and a transformer that converts the first voltage supplied from the commercial power system into a second voltage that is lower than the first voltage and supplies the second voltage to a load; a first power conditioner connected to the load and the storage battery; a second power conditioner disposed between the first power conditioner and the load and connected to a power generation facility; a switch that connects the first power conditioner to the transformer while the commercial power grid is supplying power and that disconnects the first power conditioner from the transformer while the commercial power grid is experiencing a power outage; When the relay detects a power outage in the commercial power system, it disconnects an electric path connecting the commercial power system and the transformer and transmits a power outage notification to the first power conditioner and the second power conditioner; the first power conditioner stops output when receiving the power outage notification, and then starts outputting power from the storage battery while being disconnected from the commercial power grid by the switch; the second power conditioner stops output when it receives the power outage notification, and starts outputting the power generated by the power generation facility when it receives the power outage notification and detects power supply from the first power conditioner to the load. Power system.

2. The relay is Detecting reverse power occurring between the commercial power system and the transformer; determining output power to be output from the first power conditioner and the second power conditioner based on the detected reverse power; notifying the first power conditioner and the second power conditioner of the determined output power; The first power conditioner and the second power conditioner control outputs in accordance with the notified output power. The power system of claim 1 .

3. The second power conditioner comprises: When the power outage notification is received and the supply of power from the first power conditioner to the load is detected, the first power conditioner outputs a maximum output of power within a range in which the storage battery can be charged, regardless of the output power notified from the relay. The power system of claim 2 .

4. a relay disposed between a commercial power system that supplies a first voltage and a transformer that converts the first voltage supplied from the commercial power system into a second voltage lower than the first voltage and supplies the second voltage to a load; a first power conditioner connected to the load and a storage battery; a second power conditioner disposed between the first power conditioner and the load and connected to a power generation facility; and a switch that connects the first power conditioner to the transformer while the commercial power system is supplying power and disconnects the first power conditioner from the transformer while the commercial power system is experiencing a power outage, the control device controlling the first power conditioner and the second power conditioner, When receiving a power outage notification from the relay that detected the power outage in the commercial power system, an output stop instruction to stop the output of the first power conditioner and the second power conditioner is transmitted to the first power conditioner and the second power conditioner. death, After the output is stopped in response to the output stop instruction, when it is detected that the first power conditioner has started outputting power from the storage battery in a state in which the storage battery is disconnected from the commercial power grid by the switch, an output start instruction is transmitted to the second power conditioner to start outputting power generated by the power generation facility. Control device.

Images