Power supply system

Abstract

To provide a power supply system with which, when a case is assumed where an external power supply device is connected, it is possible to appropriately suppress erroneous actions in ground fault detection by a PCS.SOLUTION: The power supply system comprises: a specific electric power conversion device having a first converter that converts the DC electric power outputted from a distributed power supply installed in a facility to AC electric power and a second converter that converts the AC electric power outputted from an external power supply device to DC electric power; and a control unit. The facility has a grounding mechanism that grounds wirings in the facility when the facility is disengaged from a power grid. The first converter converts the DC electric power outputted from the second converter to AC electric power. The control unit executes specific control regarding the external power supply device when wirings in the facility are grounded by the grounding mechanism in the disengaged state and a specific condition for ground fault detection is satisfied in the specific electric power conversion device by reception of power from the external power supply device.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a power supply system.

Background Art

[0002] In recent years, the use of distributed power sources such as storage batteries and solar cells has attracted attention. For example, a power conversion device (hereinafter, PCS; Power Conditioning System) that converts the power output from a storage battery and the power input to the storage battery is known.

[0003] Furthermore, as such a PCS, a PCS having a converter that converts AC power output from an external power supply device (for example, an external solar cell and an external PCS) installed outside the PCS into DC power has been proposed (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, generally, when the PCS is in a state of being disconnected from the power grid (hereinafter, the disconnected state), it is required to ground the wiring in the facility where the PCS is installed (for example, grounding of the neutral line N).

[0006] As a result of intensive studies, the inventors have found that when grounding of the neutral line N is required in the disconnected state, if no countermeasures are taken, a malfunction of the ground fault detection of the PCS may occur due to the ground fault current between the external power supply device and the grounding end of the wiring in the facility.

[0007] Therefore, the present invention has been made to solve the above-described problems, and an object thereof is to provide a power system that can appropriately suppress malfunction of ground fault detection of a PCS when assuming a case where an external power supply device is connected.

Means for Solving the Problems

[0008] One aspect of the disclosure includes a specific power conversion device having a first converter that converts DC power output from a distributed power source installed in a facility into AC power and a second converter that converts AC power output from an external power supply device into DC power, and a control unit. The facility has a grounding mechanism for grounding wiring in the facility in a disconnected state where the facility is disconnected from the power grid. The first converter converts DC power output from the second converter into AC power, and the control unit executes specific control regarding the external power supply device when specific conditions for detecting a ground fault in the specific power conversion device are satisfied by receiving power from the external power supply device in a state where the grounding mechanism has grounded the wiring in the facility in the disconnected state.

Effects of the Invention

[0009] According to the present invention, it is possible to provide a power system that can appropriately suppress malfunction of ground fault detection of a PCS when assuming a case where an external power supply device is connected.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

[0011] Hereinafter, embodiments will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic.

[0012] [Embodiment] (Power Supply System) Hereinafter, a power supply system according to an embodiment will be described. As shown in FIGS. 1 and 2, the power supply system 1 includes a photovoltaic cell (hereinafter, PV) 110, a storage battery (hereinafter, BT) 120, a load 140, and a measuring device 150. The power supply system 1 includes a PCS (Power Conditioning System) 200 and a distribution board 300. The power supply system 1 includes an interface 400 and an external power supply device 500.

[0013] Although not particularly limited, the PV 110, the BT 120, the load 140, the PCS 200, the distribution board 300, and the interface 400 may be devices that constitute a facility. Note that the PV 110, the BT 120, the load 140, the PCS 200, the distribution board 300, and the interface 400 may be installed inside or outside the building where the facility is installed. The facility includes indoor wiring and electrical equipment.

[0014] PV110 is a distributed power source that generates electricity in response to light such as sunlight. For example, PV110 is composed of solar panels. In an embodiment, PV110 is connected to converter 210 and is connected through converter 210 to DC power line 200X through which the DC power output from converter 230 flows.

[0015] BT120 is a distributed power source that charges and discharges power. For example, BT120 is composed of storage cells. BT120 may be referred to as a stationary battery. In an embodiment, BT120 is connected to converter 220 and is connected through converter 220 to DC power line 200X through which the DC power output from converter 230 flows.

[0016] Load 140 is a device that consumes power. Load 140 may include video devices, audio devices, refrigerators, washing machines, air conditioners, personal computers, etc. Load 140 is electrically connected to distribution board 300 by AC wiring 300X within the facility. AC wiring 300X may be referred to as in-house wiring 300X or indoor wiring 300X.

[0017] Measurement device 150 measures the power flow (AC power) from power system 11 to the facility. Measurement device 150 may measure the reverse power flow (AC power) from the facility to power system 11. Measurement device 150 may be a reverse power flow prevention sensor for preventing the reverse power flow from the facility to power system 11.

[0018] PCS200 is a power conditioner corresponding to PV110 and BT120. Specifically, PCS200 includes converter 210, converter 220, converter 230, converter 240, control unit 250, and a switch group (switches 261 to 263, switches 271 to 273).

[0019] Such a PCS200 can be electrically connected to the indoor wiring 300X of the facility. More specifically, the indoor wiring 300X of the facility is connected to the distribution board 300, and the PCS200 can be electrically connected to the indoor wiring 300X via the distribution board 300.

[0020] The converter 210 converts the voltage of the DC power output from the PV110. The converter 210 may be referred to as a unidirectional DC / DC converter.

[0021] The converter 220 converts the voltage of the DC power output from the BT120. The converter 220 converts the voltage of the DC power output from the converter 210, the converter 230, and the converter 240. The converter 220 may be referred to as a bidirectional DC / DC converter.

[0022] The converter 230 converts the AC power input from the interface 400 into DC power. The converter 230 may be referred to as an AC / DC converter. In an embodiment, the converter 230 constitutes a second converter that converts the AC power output from the external power supply device 500 into DC power.

[0023] Although not particularly limited, the converter 230 may have a function of converting the DC power output from the converter 210, the converter 220, or the converter 240 into AC power. In such a case, the converter 230 may be referred to as a bidirectional inverter.

[0024] The converter 240 converts the DC power output from the converter 210, the converter 220, or the converter 230 into AC power. The converter 240 converts the AC power supplied from the power grid 11 into DC power. The converter 240 may be referred to as a bidirectional inverter. In an embodiment, the converter 240 constitutes a first converter that converts the DC power output from the distributed power sources (for example, PV110, BT120) installed in the facility into AC power. Also, the converter 240 constitutes a first converter that converts the DC power output from the second converter into AC power.

[0025] Here, the converters 210, 220, 230, and 240 are electrically connected by a DC power line 200X through which DC power flows. The DC power line 200X may be referred to as a DC link section 200X.

[0026] The control unit 250 controls the PCS 200. The control unit 250 may include at least one processor. The at least one processor may be constituted by a single integrated circuit (IC), or may be constituted by two or more circuits (such as an integrated circuit and / or discrete circuits) communicably connected.

[0027] Although not particularly limited, the control unit 250 may be a controller installed inside the housing of the PCS, or may be a controller installed outside the housing of the PCS. The control unit 250 may be a device (for example, an EMS; Energy Management System) installed separately from the PCS 200.

[0028] After the control unit 250 grounds the indoor wiring 300X by the grounding mechanism 330, the control unit 250 may execute control to receive power from the external power supply device 500. For example, the control unit 250 may electrically connect between the interface 400 and the converter 230 by controlling the switch 263. The control unit 250 may start the output of AC power from the converter 230 by controlling the converter 230.

[0029] In the embodiment, the PCS 200 is an example of a specific power conversion device having a converter 240 (first converter) and a converter 230 (second converter).

[0030] The switch 261 is a switch that switches the electrical connection state between the PV 110 and the converter 210. The switch 262 is a switch that switches the electrical connection state between the BT 120 and the converter 220. The switch 263 is a switch that switches the electrical connection state between the interface 400 and the converter 230.

[0031] Switch 271 is a switch that switches the electrical connection state between the ELB 310 (power system 11), which will be described later, and the converter 240. Switch 272 is a switch that switches the electrical connection state between the in-facility breaker 320, which will be described later, and the converter 240. Switch 273 is a switch that switches between the connection state in which the facility is interconnected with the power system 11 and the disconnection state in which the facility is disconnected from the power system 11. Hereinafter, the state in which the facility is disconnected from the power system 11 will be referred to as the disconnection state.

[0032] The distribution board 300 has an ELB (Earth Leakage Breaker) 310 and an in-facility breaker 320.

[0033] ELB 310 is a breaker that shuts off leakage current when leakage occurs. ELB 310 is electrically connected to the power system 11. ELB 310 may be referred to as a leakage breaker.

[0034] The in-facility breaker 320 is a breaker that shuts off the indoor wiring 300X when the current in the indoor wiring 300X exceeds a threshold value. The in-facility breaker 320 is connected to the indoor wiring 300X. The in-facility breaker 320 may be referred to as a safety breaker or a circuit breaker.

[0035] In the embodiment, the facility has a grounding mechanism 330 that grounds the indoor wiring 300X in the disconnection state in which the facility (PCS 200) is disconnected from the power system 11. In other words, the facility has a grounding mechanism 330 that grounds the indoor wiring 300X of the facility in the disconnection state in which the indoor wiring 300X of the facility is disconnected from the power system by the switch 273 of the PCS 200. The grounding mechanism 330 has a grounding terminal 331 and a switch 332. For example, the switch 332 does not electrically connect the grounding terminal 331 and the distribution board 300 in the connection state (see FIG. 1), and electrically connects the grounding terminal 331 and the distribution board 300 in the disconnection state (see FIG. 2). Note that the grounding terminal refers to a portion that is electrically connected to the ground.

[0036] Although not particularly shown in FIGS. 1 and 2, the grounding mechanism 330 connects one phase of the indoor wiring 300X, that is, the neutral line of the converter 240 (generally called terminal N) to the grounding end 331. This is the same whether the self - operated output of the converter 240 is 100V or 200V.

[0037] The interface 400 is an interface that is electrically connected to the PCS200 (specifically, the converter 230). The interface 400 is an interface to which the external power supply device 500 is electrically connected. In an embodiment, the interface 400 constitutes a power interface for receiving AC power output from the external power supply device 500.

[0038] Although not particularly limited, the interface 400 may be disposed inside the PCS200 or on the outer wall of the building constituting the facility. The interface 400 may have a connector shape or a terminal shape.

[0039] The external power supply device 500 includes a PCS510 and an external power supply 520. The external power supply device 500 may be a non - insulated power supply device. The PCS510 converts DC power output from the external power supply 520 into AC power. The PCS510 may also convert AC power output from the PCS200 into DC power. The PCS510 may be a non - insulated PCS. The external power supply 520 is a power source such as a solar cell and a storage battery.

[0040] In an embodiment, the external power supply device 500 is electrically connected to the grounding end 530. Variations in the connection mode between the external power supply device 500 and the grounding end 530 will be described later (see FIGS. 3 - 5).

[0041] (Problem) In the embodiment, it is assumed that the PCS 200 has a ground fault detection function. Specifically, when a specific condition is satisfied, the PCS 200 is configured to determine that a ground fault has occurred and then stop the operation of the PCS 200. Such a function of the PCS 200 may be referred to as a ground fault detection function.

[0042] Here, the specific condition is defined by a predetermined threshold value and a predetermined time. Specifically, the specific condition is a condition in which the ground fault current of the wiring between the PCS 200 and the grounding terminal 331 is equal to or greater than the predetermined threshold value and continues for the predetermined time. For example, the predetermined threshold value may be set based on the capacitance to ground of the PV 110 that can be connected to the PCS 200. The predetermined time may be determined in advance according to the safety design of the PCS 200 or the like. It should be noted that at least a part of the wiring between the PCS 200 and the grounding terminal 331 is common with the wiring between the external power supply device 500 and the grounding terminal 331.

[0043] As described above, the grounding mechanism 330 grounds the indoor wiring 300X in the open state. Further, the external power supply device 500 is electrically connected to the grounding terminal 530. Therefore, assuming that the external power supply device 500 is connected to the PCS 200, the ground fault detection function is activated by the ground fault current between the external power supply device 500 and the grounding terminal 331, and a malfunction of the ground fault detection of the PCS 200 may occur even though it is originally a normal operation.

[0044] (Connection mode) Hereinafter, variations in the connection mode between the external power supply device 500 and the grounding terminal 530 will be described.

[0045] First, as shown in FIG. 3, the external power supply device 500A may be a device having the PCS 510A and the BT 520A. The external power supply device 500A is an example of the external power supply device 500 described above.

[0046] The PCS 510A includes a converter 541A, a converter 542A, an interconnection terminal 551A, a self - standing connection terminal 552A, a switch 561A, a switch 562A, a switch 563A, and a grounding mechanism 570A.

[0047] Converter 541A converts the voltage of the DC power output from BT520A. Converter 541A converts the voltage of the DC power output from Converter 542A. Converter 541A may be referred to as a bidirectional DC / DC converter.

[0048] Converter 542A converts the DC power output from Converter 541A into AC power. Converter 542A may convert the AC power supplied from PCS200 (Interface 400) into DC power. Converter 542A may be referred to as a bidirectional inverter.

[0049] The self - supporting connection terminal 552A is connected to Interface 400. That is, the self - supporting connection terminal 552A outputs power from PCS510A to PCS200 in the islanded state. The self - supporting connection terminal 552A may input power from PCS200 to PCS510A in the islanded state.

[0050] Switch 561A is a switch that switches the electrical connection state between BT520A and Converter 541A. Switch 562A is a switch that switches the electrical connection state between the tie connection terminal 551A and Converter 542A. Switch 563A is a switch that switches the electrical connection state between the self - supporting connection terminal 552A and Converter 542A.

[0051] The grounding mechanism 570A is a grounding mechanism that grounds the external power supply device 500A in the disconnection state. The grounding mechanism 570A is grounded separately from the above-described grounding mechanism 330. Specifically, the grounding mechanism 570 is a mechanism that grounds the wiring between the PCS 542A and the self-supporting connection terminal 552A in the disconnection state. The grounding mechanism 570A may be referred to as a specific grounding mechanism for the purpose of distinguishing it from the grounding mechanism 330. Alternatively, for the purpose of distinguishing the grounding mechanism 330 and the grounding mechanism 570A, the grounding mechanism 330 may be referred to as the first grounding mechanism, and the grounding mechanism 570A may be referred to as the second grounding mechanism. The grounding mechanism 570A has a grounding terminal 571A and a switch 572A. The switch 572A electrically connects the grounding terminal 571A and the PCS 510A in the disconnection state without electrically connecting the grounding terminal 571A and the PCS 510A in the connection state of the PCS 510A.

[0052] In FIG. 3, an example of a case where the grounding mechanism 570A is disposed inside the PCS 510A is illustrated. However, the embodiment is not limited to this. The grounding mechanism 570A may be disposed outside the PCS 510A.

[0053] The BT 520A is a distributed power source that charges and discharges electric power. For example, the BT 520A is composed of storage cells. For the purpose of distinguishing the BT 120 and the BT 520A, the BT 120 may be referred to as the first storage battery, and the BT 520A may be referred to as the second storage battery.

[0054] Here, in FIG. 3, the connection state in the disconnection state is illustrated. The PCS 510A may be an insulated PCS or a non-insulated PCS. The grounding terminal 571A is an example of the grounding terminal 530 shown in FIGS. 1 and 2. In FIG. 3, the BT 520A is illustrated as the external power source 520, but the external power source 520 may be a solar cell.

[0055] That is, in the case shown in FIG. 3, in the islanded state, false operation of the ground fault detection of the PCS200 may occur due to the ground fault current of the wiring between the ground terminal 571A and the ground terminal 331. For example, even if the converter 541A is an isolation transformer type converter, it should be noted that false operation of the ground fault detection of the PCS200 may occur.

[0056] Second, as shown in FIG. 4, the external power supply device 500B may be a device having the PCS510B and the PV520B. The external power supply device 500B is an example of the above-described external power supply device 500.

[0057] The PCS510B includes a converter 541B, a converter 542B, an interconnection terminal 551B, an independent connection terminal 552B, a switch 561B, a switch 562B, and a switch 563B.

[0058] The converter 541B converts the voltage of the DC power output from the PV520B. The converter 541B may be referred to as a unidirectional DC / DC converter.

[0059] The converter 542B converts the DC power output from the converter 541B into AC power. The converter 542B may be a unidirectional inverter.

[0060] The independent connection terminal 552B is connected to the interface 400. That is, the independent connection terminal 552B outputs power from the PCS510B to the PCS200 in the islanded state.

[0061] The switch 561B is a switch that switches the electrical connection state between the PV520B and the converter 541B. The switch 562B is a switch that switches the electrical connection state between the interconnection terminal 551B and the converter 542B. The switch 563B is a switch that switches the electrical connection state between the independent connection terminal 552B and the converter 542B.

[0062] The PV520B is a distributed power source that generates electricity in response to light such as sunlight. For example, the PV520B is composed of solar panels.

[0063] Here, in FIG. 4, the connection state of the switch 563B of the PCS510B in the disconnected state where the indoor wiring 300X of the facility is disconnected from the power grid 11 as shown in FIG. 3 is illustrated. The PCS510B is a non-insulated type PCS. The PCS510B is grounded by the circuit ground 571B. The PV520B is grounded by the ground 521B. The circuit ground 571B is an example of the ground terminal 530 shown in FIG. 2.

[0064] That is, in the case shown in FIG. 4, in the disconnected state, due to the ground fault current of the wiring between the circuit ground 571B and the ground terminal 331, a malfunction of the ground fault detection of the PCS200 may occur. It should be noted that the malfunction of the ground fault detection does not occur in the interconnected state but occurs in the disconnected state (island operation). Therefore, it is difficult to detect the malfunction of the ground fault detection in advance.

[0065] Thirdly, as shown in FIG. 5, the external power supply device 500C may be a device having the PCS510C and the PV520C. The external power supply device 500C is an example of the external power supply device 500 described above.

[0066] The PCS510C includes a converter 541C, a converter 542C, a grid connection terminal 551C, an island connection terminal 552C, a switch 561C, a switch 562C, and a switch 563C.

[0067] The converter 541C converts the voltage of the DC power output from the PV520C. The converter 541C may be referred to as a unidirectional DC / DC converter.

[0068] The converter 542C converts the DC power output from the converter 541C into AC power. The converter 542C may be a unidirectional inverter.

[0069] The self - supporting connection terminal 552C is connected to the interface 400. That is, the self - supporting connection terminal 552C outputs power from the PCS510C to the PCS200 in the islanded state.

[0070] The switch 561C is a switch for switching the electrical connection state between the PV520C and the converter 541C. The switch 562C is a switch for switching the electrical connection state between the tie connection terminal 551C and the converter 542C. The switch 563C is a switch for switching the electrical connection state between the self - supporting connection terminal 552C and the converter 542C.

[0071] The PV520C is a distributed power source that generates electricity in response to light such as sunlight. For example, the PV520C is composed of a solar panel.

[0072] Here, in FIG. 5, the connection state in the islanded state is illustrated. The PCS510C is a non - insulated PCS. The capacitance to ground of the PV520C is larger than the capacitance to ground of the PV110. For example, the PV110 may be a crystalline solar cell, and the PV520C may be a non - crystalline solar cell. The PV520C is grounded by the ground 521C. The ground 521C is an example of the grounding terminal 530 shown in FIG. 2.

[0073] That is, in the case shown in FIG. 5, in the islanded state, due to the ground fault current of the wiring between the ground 521C and the grounding terminal 331, a malfunction of the ground fault detection of the PCS200 may occur. For example, when assuming a case where the PCS510C has a ground fault detection function, if the capacitance to ground of the PV520C is larger than the capacitance to ground of the PV110, the predetermined threshold value used in the ground fault detection function of the PCS510C is larger than the predetermined threshold value used in the ground fault detection function of the PCS200. Therefore, it should be noted that a ground fault may be detected by the PCS200 without being detected by the PV520C.

[0074] (Operation example) Hereinafter, an operation example for solving the above - described problems will be described.

[0075] First, the control unit 250 may be configured as a control unit that executes a determination process for determining whether power can be received from the external power supply device 500 in a state where the grounding mechanism 330 grounds the wiring in the facility (indoor wiring 300X) in the islanded state. The control unit 250 may execute the determination process before the above-described specific conditions are satisfied. By executing such a determination process, it is possible to suppress the malfunction of the ground fault detection of the PCS 200 associated with the output power of the external power supply device 500.

[0076] Specifically, the control unit 250 may determine that power reception from the external power supply device 500 is not possible when the state where the ground fault current is equal to or greater than a predetermined threshold continues for a specific time shorter than a predetermined time in the islanded state. That is, the control unit 250 may determine that it is not possible for the PCS 200 to receive power from the external power supply device 500 when a malfunction of the ground fault detection of the PCS 200 is assumed in the islanded state.

[0077] On the other hand, the control unit 250 may determine that power reception from the external power supply device 500 is possible when the state where the ground fault current is equal to or greater than a predetermined threshold does not continue for a specific time shorter than a predetermined time in the islanded state. That is, the control unit 250 may determine that power reception from the external power supply device 500 is possible when a malfunction of the ground fault detection of the PCS 200 is not assumed in the islanded state.

[0078] Here, the condition that the state where the ground fault current is equal to or greater than a predetermined threshold continues for a specific time shorter than a predetermined time may be referred to as a determination condition. The determination condition may be considered as a condition for determining whether a malfunction of the ground fault detection of the PCS 200 is assumed in the islanded state. That is, when the determination condition is satisfied, it may be determined that a malfunction of the ground fault detection of the PCS 200 is assumed in the islanded state, and when the determination condition is not satisfied, it may be determined that a malfunction of the ground fault detection of the PCS 200 is not assumed in the islanded state.

[0079] When it is determined that power reception from the external power supply device 500 is impossible, the control unit 250 may perform notification or notice indicating that power reception from the external power supply device 500 is impossible. When it is determined that power reception from the external power supply device 500 is possible, the control unit 250 may perform notification or notice indicating that power reception from the external power supply device 500 is possible. The notification may be for the user of the PCS 200. The notification may be one or more notifications selected from sound and display. The notice may be transmission of information to the notice recipient. The notice recipient may be the EMS, or one or more recipients selected from the server that manages the PCS 200 (for example, the facility management server), the server that manages the power of the facility (for example, the power management server), and the terminal possessed by the user of the PCS 200.

[0080] When the received power from the external power supply device 500 is equal to or less than the first threshold value in the islanded state, the control unit 250 may perform notification or notice indicating that power reception from the external power supply device 500 is not possible. The first threshold value may be smaller than the power corresponding to the predetermined threshold value that defines the specific condition for detecting a ground fault in the PCS 200, and may be set arbitrarily. As the state where the received power from the external power supply device 500 is equal to or less than the first threshold value, a state where the external power supply device 500 is not ready to output power (such as power off) may be assumed, or a state where the external power supply device 500 is not connected to the PCS 200 may be assumed. The notification may be one or more notifications selected from sound and display. The notice may be transmission of information to the notice recipient. The notice recipient may be the EMS, or one or more recipients selected from the server that manages the PCS 200 (for example, the facility management server), the server that manages the power of the facility (for example, the power management server), and the terminal possessed by the user of the PCS 200.

[0081] The control unit 250 may execute determination processing when the received power from the external power supply device 500 is equal to or greater than a second threshold value in the islanded state. The second threshold value may be smaller than the power corresponding to a predetermined threshold value that defines a specific condition for detecting a ground fault in the PCS 200, and may be arbitrarily set. That is, the control unit 250 executes the determination processing after the output power of the external power supply device 500 (that is, the ground fault current between the external power supply device 500 and the ground terminal 331) has stabilized.

[0082] The control unit 250 may execute determination processing during the installation process of the PCS 200 (the first converter, the second converter) and the external power supply device 500. In such a case, the control unit 250 stores the result of the determination processing, and when performing self-sustained operation in the islanded state, may specify whether power can be received from the external power supply device 500 based on the result of the determination processing.

[0083] Note that the installation process may be, for example, a construction process of connecting the external power supply device 500 to the PCS 200, or when the external power supply device 500 has a movable configuration, it may be a construction process of temporarily connecting the external power supply device 500 to the PCS 200.

[0084] The control unit 250 may execute determination processing during the process of starting the self-sustained operation of the facility after the installation of the PCS 200 (the first converter, the second converter) and the external power supply device 500. The control unit 250 may execute determination processing each time self-sustained operation is started in the islanded state.

[0085] Second, the control unit 250 may be configured as a control unit that executes specific control regarding the external power supply device 500 when specific conditions for detecting a ground fault in the PCS 200 (specific power conversion device) can be satisfied by receiving power from the external power supply device 500 in a state where the grounding mechanism 330 grounds the wiring (indoor wiring 300X) in the facility in the islanded state.

[0086] Here, the case where the specific conditions can be satisfied may be considered as the case where the above-described determination conditions are satisfied. In other words, the case where the specific conditions can be satisfied may be considered as the case where a malfunction of the ground fault detection of the PCS200 is assumed in the islanded state.

[0087] As a specific control, the control unit 250 may stop the power conversion operation of the PCS230 (second converter). That is, the control unit 250 may stop drawing power from the external power supply device 500 to the PCS230 (second converter).

[0088] As a specific control, the control unit 250 may stop the power output of the external power supply device 500. For example, the control unit 250 may transmit a control command for instructing the stop of the power output of the external power supply device 500 to the control unit of the PCS510.

[0089] As a specific control, the control unit 250 may directly or indirectly control a specific grounding mechanism (for example, the grounding mechanism 570A shown in FIG. 3) so that the external power supply device 500 is not grounded. For example, when the control unit 250 can directly control the grounding mechanism 570A, the control unit 250 may transmit a command for controlling so that the external power supply device 500 is not grounded in the islanded state to the grounding mechanism 570A. When the PCS510A controls the grounding mechanism 570A, the control unit 250 may transmit a command for controlling so that the external power supply device 500 is not grounded in the islanded state to the control unit of the PCS510A and indirectly control the grounding mechanism 570A.

[0090] As a specific control, the control unit 250 may control the external power supply device 500 so that the output current or output power of the external power supply device 500 becomes less than a specific threshold value. The specific threshold value is a value smaller than the current or power corresponding to a predetermined threshold value that defines the specific conditions for detecting a ground fault in the PCS200. The specific threshold value may be expressed as a ratio (for example, 20%) with respect to the rated output of the PCS510. For example, the control unit 250 may transmit a control command for instructing that the current or power of the external power supply device 500 becomes less than the specific threshold value to the control unit of the PCS510.

[0091] (Power control method) Hereinafter, the power control method according to the embodiment will be described.

[0092] First, a case where a determination process is executed in the installation process of the PCS 200 and the external power supply device 500 will be described.

[0093] As shown in FIG. 6, in step S10, the preparation of the external power supply device 500 is executed. The preparation of the external power supply device 500 may include a process of electrically connecting the external power supply device 500 to the PCS 200, or may include a process of transitioning the external power supply device 500 to a state where power can be output by turning on the power of the external power supply device 500 or the like.

[0094] In step S11, the switch group (switch 263, switch 271, switch 272, switch 273, switch 332) is switched to a state in which it is in a disconnected state (see FIG. 2). The switching of the switch group may be executed by the control unit 250 or may be executed by other means.

[0095] In step S12, the PCS 200 starts receiving power from the external power supply device 500. The start of receiving power from the external power supply device 500 may be executed by controlling the converter 230 by the control unit 250.

[0096] In step S13, the control unit 250 determines whether or not the determination condition is satisfied. For example, the control unit 250 determines whether or not a state in which the ground fault current between the external power supply device 500 and the ground terminal 331 is equal to or greater than a predetermined threshold value continues for a predetermined time. If the determination condition is satisfied, the process of step S14 is executed, and if the determination condition is not satisfied, the process of step S15 is executed.

[0097] In step S14, the control unit 250 determines that power reception from the external power supply device 500 is impossible in the disconnection state (i.e., the state where the grounding mechanism 330 grounds the indoor wiring 300X). The control unit 250 may store the determination result. The control unit 250 may perform notification or notice indicating that power reception from the external power supply device 500 is impossible.

[0098] In step S15, the control unit 250 determines that power reception from the external power supply device 500 is possible in the disconnection state (i.e., the state where the grounding mechanism 330 grounds the indoor wiring 300X). The control unit 250 may store the determination result. The control unit 250 may perform notification or notice indicating that power reception from the external power supply device 500 is possible.

[0099] In step S16, the PCS 200 ends power reception from the external power supply device 500. The end of power reception from the external power supply device 500 may be executed by controlling the converter 230 by the control unit 250.

[0100] In step S17, the switch group (switches 263, 271, 272, 273, 332) is switched to the state in the interlocked state (see FIG. 1). The switching of the switch group may be executed by the control unit 250 or may be executed by other means.

[0101] Second, a case where determination processing is executed in the process of starting self - operation after the installation of the PCS 200 and the external power supply device 500 will be described.

[0102] As shown in FIG. 7, in step S20, the PCS 200 receives an instruction to start self - operation. The reception of the instruction to start self - operation may be reinterpreted as detection of a power outage.

[0103] In step S21, the switch group (switches 263, 271, 272, 273, 332) is switched to the state in the open state (see FIG. 2). The switching of the switch group may be executed by the control unit 250 or may be executed by other means.

[0104] In step S22, the PCS 200 starts receiving power from the external power supply device 500. The start of receiving power from the external power supply device 500 may be executed by controlling the converter 230 by the control unit 250.

[0105] In step S23, the control unit 250 determines whether or not the determination condition is satisfied. For example, the control unit 250 determines whether or not a state where the ground fault current between the external power supply device 500 and the ground terminal 331 is equal to or greater than a predetermined threshold value continues for a predetermined time. If the determination condition is satisfied, the process of step S24 is executed, and if the determination condition is not satisfied, the process of step S25 is executed.

[0106] In step S24, the control unit 250 determines that power reception from the external power supply device 500 is impossible in the open state (that is, the state where the grounding mechanism 330 grounds the indoor wiring 300X). The control unit 250 may store the determination result. The control unit 250 may execute notification or notice indicating that power reception from the external power supply device 500 is impossible.

[0107] In step S25, the control unit 250 determines that power reception from the external power supply device 500 is possible in the open state (that is, the state where the grounding mechanism 330 grounds the indoor wiring 300X). The control unit 250 may store the determination result. The control unit 250 may execute notification or notice indicating that power reception from the external power supply device 500 is possible.

[0108] In step S26, the PCS 200 receives an instruction to end the self-operation. The reception of the instruction to end the self-operation may be read as detection of restoration of power supply after a power outage.

[0109] In step S27, the PCS 200 terminates power reception from the external power supply device 500. The termination of power reception from the external power supply device 500 may be executed by controlling the converter 230 by the control unit 250.

[0110] In step S28, the switch group (switch 263, switch 271, switch 272, switch 273), switch 332) is switched to the state in the interlocked state (see FIG. 1). The switching of the switch group may be executed by the control unit 250 or may be executed by other means.

[0111] Thirdly, a case of executing specific control regarding the external power supply device 500 will be described. Here, mainly for the purpose of explaining the specific control in the islanded state (self-sustained operation), a part of the determination regarding whether the determination condition is satisfied (for example, steps S22, S24, S25, S26, S27, S28 shown in FIG. 7, etc.) will be omitted.

[0112] As shown in FIG. 8, in step S30, the PCS 200 receives an instruction to start self-sustained operation. The reception of the instruction to start self-sustained operation may be interpreted as the detection of a power outage.

[0113] In step S31, the switch group (switch 263, switch 271, switch 272, switch 273, switch 332) is switched to the state in the islanded state (see FIG. 2). The switching of the switch group may be executed by the control unit 250 or may be executed by other means.

[0114] In step S31, the control unit 250 determines whether the determination condition is satisfied. As described above, whether the determination condition is satisfied may be determined in the installation process of the PCS 200 and the external power supply device 500 (see FIG. 6), or may be determined in the process of starting self-sustained operation after the installation of the PCS 200 and the external power supply device 500 (see FIG. 7).

[0115] In step S32, the control unit 250 determines whether or not the determination condition is satisfied. For example, the control unit 250 determines whether or not a state in which the ground fault current between the external power supply device 500 and the ground terminal 331 is equal to or greater than a predetermined threshold value continues for a predetermined time. When the determination condition is satisfied, the process of step S33 is executed, and when the determination condition is not satisfied, the process of step S34 is executed.

[0116] In step S33, the control unit 250 executes specific control. The specific control may be a process of stopping the power conversion operation of the PCS 230. The specific control may be a process of stopping the power output of the external power supply device 500. The specific control may be a process of controlling a specific grounding mechanism (for example, the grounding mechanism 570A shown in FIG. 3) so that the external power supply device 500 is not grounded. The specific control may be a process of controlling the output current or output power of the external power supply device 500 to be less than a specific threshold value.

[0117] In step 34, the control unit 250 may execute normal control. Normal control is a term used for comparison with specific control, and may be any control other than specific control. For example, the normal control may be a control that permits power reception from the external power supply device 500 without imposing any particular restrictions.

[0118] (Operation and Effect) In the embodiment, the control unit 250 executes a determination process for determining whether or not power reception from the external power supply device 500 is permitted in a state where the grounding mechanism 330 grounds the wiring (indoor wiring 300X) in the facility in the disconnection state. According to such a configuration, it is possible to determine whether or not to permit power reception from the external power supply device 500 according to whether or not a malfunction of the ground fault detection of the PCS 200 may occur due to the ground fault current between the external power supply device 500 and the ground terminal 331. Therefore, when assuming a case where the external power supply device 500 is connected, it is possible to appropriately suppress a malfunction of the ground fault detection of the PCS 200.

[0119] In an embodiment, when it is determined that power reception from the external power supply device 500 is impossible, the control unit 250 may execute notification or notice indicating that power reception from the external power supply device 500 is impossible. According to such a configuration, it is possible to recognize that power reception from the external power supply device 500 cannot be expected, and it is possible to appropriately formulate a plan for autonomous operation or the like.

[0120] In an embodiment, when specific conditions for detecting a ground fault in the PCS 200 (specific power conversion device) by power reception from the external power supply device 500 are satisfied in a state where the grounding mechanism 330 grounds the wiring in the facility (indoor wiring 300X) in the disconnection state, specific control regarding the external power supply device 500 is executed. Here, the specific control may be a process of stopping the power conversion operation of the PCS 230. The specific control may be a process of stopping the power output of the external power supply device 500. The specific control may be a process of controlling a specific grounding mechanism (for example, the grounding mechanism 570A shown in FIG. 3) so that the external power supply device 500 is not grounded. The specific control may be a process of controlling the output current or output power of the external power supply device 500 to be less than a specific threshold value. According to such a configuration, when a case where the external power supply device 500 is connected is assumed, it is possible to appropriately suppress a malfunction of ground fault detection of the PCS 200.

[0121] [Modification Example 1] Hereinafter, Modification Example 1 of the embodiment will be described. Hereinafter, the differences from the embodiment will be mainly described.

[0122] In the embodiment, the connection terminal for connection (connection terminal 551A shown in FIG. 3, connection terminal 551B shown in FIG. 4, connection terminal 551C shown in FIG. 5) of the external power supply device 500 is connected to the interface 400 of the PCS 200. On the other hand, in Modification Example 1, the connection terminal for connection of the external power supply device 500 is connected to the wiring in the facility (indoor wiring 300X) without being connected to the power grid 11 in the disconnection state. That is, in the disconnection state, the output power of the external power supply device 500 is supplied to the load 140 connected to the indoor wiring 300X without passing through the PCS 200.

[0123] For example, as shown in FIG. 9, the external power supply device 500D may be a device having a PCS 510D and a BT 520D. Since the PCS 510D and the BT 520D are the same as the PCS 510A and the BT 520A described in FIG. 3, the details thereof will be omitted.

[0124] Here, the tie connection terminal 551D is connected to the facility breaker 320 (i.e., the indoor wiring 300X) without being tied to the power grid 11 in the islanded state. The self - supporting connection terminal 552D is connected to the interface 400 of the PCS 200 in the same manner as the self - supporting connection terminal 552A described in FIG. 3.

[0125] In Modification 1, as specific control, the control unit 250 outputs power from the tie connection terminal 551D of the external power supply device 500. That is, when the determination condition is satisfied, the control unit 250 outputs power from the tie connection terminal 551D even in the islanded state (self - supporting operation) without using the self - supporting connection terminal 552D. In other words, the control unit 250 turns off the switch 563D to disconnect the converter 542D from the self - supporting connection terminal 552D, and turns on the switch 562D to connect the converter 542D to the tie connection terminal 551D.

[0126] Here, as the reference waveform of the tie operation output of the PCS 510D in the specific control, the waveform of the self - supporting operation output of the PCS 200 may be used.

[0127] Note that when the determination condition is not satisfied, the control unit 250 outputs power from the self - supporting connection terminal 552D in the normal manner without using the tie connection terminal 551D. In other words, the control unit 250 turns off the switch 562D to disconnect the converter 542D from the tie connection terminal 551D, and turns on the switch 563D to connect the converter 542D to the self - supporting connection terminal 552D. Such control may be considered as an example of normal control.

[0128] (Operation and Effect) In Modification Example 1, on the premise that the connection terminal 551D of the external power supply device 500D is connected to the facility breaker 320 (that is, the indoor wiring 300X) without being connected to the power grid 11 in the islanded state, as specific control, the control unit 250 may output power from the connection terminal 551D of the external power supply device 500. According to such a configuration, since the output power of the external power supply device 500 does not pass through the PCS 200, it is possible to appropriately suppress the malfunction of the ground fault detection of the PCS 200.

[0129] [Other Embodiments] Although the present invention has been described by the above-described embodiments, the descriptions and drawings forming a part of this disclosure should not be understood as limiting the present invention. Various alternative embodiments, examples, and operation techniques will be apparent to those skilled in the art from this disclosure.

[0130] In the above disclosure, the case where the determination condition is that the ground fault current between the external power supply device 500 and the grounding terminal 331 continues for a specific time in a state equal to or greater than a predetermined threshold value has been illustrated. However, the above disclosure is not limited to this. The determination condition may be any condition for determining whether a specific condition can be satisfied in the islanded state. In other words, the determination condition may be any condition for determining whether a malfunction of the ground fault detection of the PCS 200 is assumed in the islanded state. For example, the determination condition may be determined by the behavior of the ground fault current in which a malfunction of the ground fault detection of the PCS 200 can be assumed in the islanded state.

[0131] In the above disclosure, the case where the control unit 250 is the control unit of the PCS 200 has been mainly described. However, the above disclosure is not limited to this. The control unit 250 may be composed of the control unit of the PCS 200 and the control unit of the PCS 510 that can communicate with each other. The control unit 250 may be composed of the control unit of the PCS 200 and the EMS that can communicate with each other. The control unit 250 may be composed of the control unit of the PCS 200, the control unit of the PCS 510, and the EMS that can communicate with each other. The control unit 250 may be composed of only the EMS.

[0132] In the above disclosure, PV110 and BT120 were exemplified as distributed power sources installed in the facility. However, the above disclosure is not limited thereto. The distributed power sources installed in the facility may include one or more distributed power sources selected from a fuel cell device, a wind power generation device, a hydroelectric power generation device, a geothermal power generation device, and a biomass power generation device.

[0133] In the above disclosure, as the external power supply device 500, a device including a storage battery and a PCS, and a device including a solar cell and a PCS were exemplified. However, the above disclosure is not limited thereto. The external power supply device 500 may be a device including one or more distributed power sources selected from a fuel cell device, a wind power generation device, a hydroelectric power generation device, a geothermal power generation device, and a biomass power generation device and a PCS. The external power supply device 500 may be an engine generator without a PCS.

[0134] Although not particularly mentioned in the above disclosure, the disconnection state may be read as the self - supporting state. "External" may mean at least outside the PCS200. "External" may mean outside the facility where the PCS200 is installed. "Power supply device" may be considered as a term indicating a device including a power supply and a PCS, or may be considered as a term indicating a power supply that does not require a PCS.

[0135] Although not particularly mentioned in the above disclosure, the communication between units such as the converter 220, the converter 230, the converter 240, the control unit 250, and various measurement devices may be executed in accordance with a predetermined protocol (for example, RS485, ECHONET Lite (registered trademark)).

[0136] [Appendix] The above disclosure may be expressed as follows.

[0137] A first feature is a power system including a specific power conversion device having a first converter that converts DC power output from a distributed power source installed in a facility into AC power and a second converter that converts AC power output from an external power supply device into DC power, and a control unit. The facility has a grounding mechanism for grounding the wiring in the facility in a disconnected state where the facility is disconnected from the power grid. The first converter converts the DC power output from the second converter into AC power. The control unit executes specific control regarding the external power supply device when a specific condition for detecting a ground fault in the specific power conversion device by receiving power from the external power supply device is satisfied in a state where the grounding mechanism has grounded the wiring in the facility in the disconnected state.

[0138] A second feature is the power system according to the first feature, wherein the control unit stops the power conversion operation of the second converter as the specific control.

[0139] A third feature is the power system according to the first or second feature, wherein the control unit stops the power output of the external power supply device as the specific control.

[0140] A fourth feature is the power system according to any one of the first to third features, wherein a specific grounding mechanism for grounding the external power supply device in the disconnected state is installed separately from the grounding mechanism, and the control unit directly or indirectly controls the specific grounding mechanism so that the external power supply device is not grounded as the specific control.

[0141] A fifth feature is the power system according to the first feature, wherein the specific condition is a condition in which a ground fault current between the external power supply device and the grounding end of the wiring in the facility continues for a predetermined time with a value equal to or greater than a predetermined threshold, and the control unit controls the external power supply device so that the output current or output power of the external power supply device is less than a specific threshold corresponding to the predetermined threshold as the specific control.

[0142] The sixth feature is that in the first feature, the connection terminal of the external power supply device is connected to the wiring in the facility without being connected to the power grid in the islanded state, and the control unit outputs power from the connection output terminal of the external power supply device as the specific control, which is a power system.

Explanation of Signs

[0143] 1…Power system, 11…Power grid, 110…PV, 120…BT, 140…Load, 150…Measuring device, 200…PCS, 200X…DC power line (DC link section), 210…Converter, 220…Converter, 230…Converter, 240…Converter, 250…Control unit, 261~263…Switch, 271~273…Switch, 300…Distribution board, 300X…AC wiring (indoor wiring), 310…ELB, 320…In-facility breaker, 330…Grounding mechanism, 331…Grounding terminal, 332…Switch, 400…Interface, 500…External power supply device, 510, 510A, 510B, 510C, 510D…PCS, 520…External power supply, 520A, 520D…BT, 520B, 520C…PV, 521B, 521C…Earth, 530…Grounding terminal, 541A, 541B, 541C, 541D…Converter, 542A, 542B, 542C, 542D…Converter, 551A, 551B, 551C, 551D…Connection terminal, 552A, 552B, 552C, 552D…Self-supporting connection terminal, 561A, 561B, 561C, 561D…Switch, 562A, 562B, 562C, 562D…Switch, 563A, 563B, 563C, 563D…Switch, 570A, 570D…Grounding mechanism, 571A, 571D…Grounding terminal, 571B…Circuit earth, 572A, 572D…Switch

Claims

1. A specific power conversion device having a first converter that converts DC power output from a distributed power source installed in a facility into AC power and a second converter that converts AC power output from an external power supply device into DC power, and a control unit, wherein the facility has a grounding mechanism for grounding the wiring in the facility in a disconnected state where the facility is disconnected from the power grid, the first converter converts the DC power output from the second converter into AC power, the control unit executes specific control regarding the external power supply device when a specific condition for detecting a ground fault in the specific power conversion device by receiving power from the external power supply device can be satisfied in a state where the grounding mechanism has grounded the wiring in the facility in the disconnected state, a power system.

2. The control unit stops the power conversion operation of the second converter as the specific control, the power system according to claim 1.

3. The control unit stops the power output of the external power supply device as the specific control, the power system according to claim 1.

4. A specific grounding mechanism for grounding the external power supply device in the disconnected state is installed separately from the grounding mechanism, the control unit directly or indirectly controls the specific grounding mechanism so that the external power supply device is not grounded as the specific control, the power system according to claim 1.

5. The specific condition is a condition in which a state where the ground fault current between the external power supply device and the grounded end of the wiring in the facility is equal to or greater than a predetermined threshold continues for a predetermined time, the control unit controls the external power supply device so that the output current or output power of the external power supply device is less than a specific threshold corresponding to the predetermined threshold as the specific control, the power system according to claim 1.

6. The connection terminal of the external power supply device is connected to the wiring in the facility without being connected to the power grid in the disconnected state, the control unit outputs power from the connection output terminal of the external power supply device as the specific control, the power system according to claim 1.

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