Power 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 first converter that converts DC electric power outputted from a distributed power supply installed in a facility to AC electric power, a second converter that converts 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 a determination process of determining the allowability of receiving electric power from the external power supply device when wirings in the facility are grounded by the grounding mechanism in the disengaged state.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] In recent years, the use of distributed power sources such as storage batteries and solar cells has been attracting attention. For example, a power conditioning system (hereinafter referred to as PCS) that converts the power output from a storage battery and the power input to a 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 (e.g., an external solar cell and an external PCS) installed outside the PCS into DC power has been proposed (e.g., Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-175336 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, when a PCS is disconnected from the power grid (hereinafter referred to as the disconnected state), it is required to ground the wiring within the facility where the PCS is installed (for example, grounding the neutral wire N).

[0006] After careful consideration, the inventors discovered that if no measures are taken when the neutral wire N needs to be grounded in the disconnected state, the ground fault current between the external power supply device and the grounded end of the wiring within the facility may cause the PCS ground fault detection to malfunction.

[0007] Therefore, the present invention has been made to solve the above-mentioned problems, and aims to provide a power supply system that can appropriately suppress malfunction of the PCS's ground fault detection when an external power supply device is connected. [Means for solving the problem]

[0008] One aspect of the disclosure is a power supply system comprising a first converter that converts DC power output from a distributed power source installed in a facility into AC power, 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 that grounds wiring within the facility when the facility is in a disconnected state in which it is disconnected from the power grid, the first converter converts the DC power output from the second converter into AC power, and the control unit executes a determination process to determine whether power can be received from the external power supply device when the grounding mechanism grounds the wiring within the facility in the disconnected state. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a power supply system that can appropriately suppress malfunctions in ground fault detection of a PCS when an external power supply device is connected. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a power supply system 1 (in a grid-connected state) according to an embodiment. [Figure 2] FIG. 2 is a diagram showing the power supply system 1 (disconnected state) according to the embodiment. [Figure 3] FIG. 3 is a diagram showing an external power supply device 500A according to the embodiment. [Figure 4] FIG. 4 is a diagram showing an external power supply device 500B according to the embodiment. [Figure 5] FIG. 5 is a diagram showing an external power supply device 500C according to the embodiment. [Figure 6] FIG. 6 is a diagram illustrating a power supply control method according to the embodiment. [Figure 7] FIG. 7 is a diagram illustrating a power supply control method according to the embodiment. [Figure 8] FIG. 8 is a diagram illustrating a power supply control method according to the embodiment. [Figure 9] FIG. 9 is a diagram showing a power supply system 1 (in a disconnected state) according to the first modified example. DETAILED DESCRIPTION OF THE INVENTION

[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) A power supply system according to an embodiment will be described below. As shown in Figures 1 and 2, the power supply system 1 includes a solar cell (hereinafter referred to as PV) 110, a storage battery (hereinafter referred to as BT) 120, a load 140, and a measuring device 150. The power supply system 1 also includes a PCS (Power Conditioning System) 200 and a distribution board 300. The power supply system 1 also includes an interface 400 and an external power supply device 500.

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

[0014] The PV 110 is a distributed power source that generates power in response to light such as sunlight. For example, the PV 110 is configured by a solar panel. In the embodiment, the PV 110 is connected to a converter 210, and is connected via the converter 210 to a DC power line 200X through which DC power output from a converter 230 flows.

[0015] The BT 120 is a distributed power source that charges and discharges power. For example, the BT 120 is configured with a power storage cell. The BT 120 may also be referred to as a stationary storage battery. In the embodiment, the BT 120 is connected to a converter 220, and is connected via the converter 220 to a DC power line 200X through which DC power output from a converter 230 flows.

[0016] The load 140 is a device that consumes power. The load 140 may include video equipment, audio equipment, a refrigerator, a washing machine, an air conditioner, a personal computer, etc. The load 140 is electrically connected to the distribution board 300 by AC wiring 300X within the facility. The AC wiring 300X may be referred to as in-house wiring 300X or indoor wiring 300X.

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

[0018] The PCS 200 is a power conditioner compatible with the PV 110 and the BT 120. Specifically, the PCS 200 includes a converter 210, a converter 220, a converter 230, a converter 240, a control unit 250, and a group of switches (switches 261 to 263, switches 271 to 273).

[0019] Such a PCS200 can be electrically connected to indoor wiring 300X of the facility. More specifically, the indoor wiring 300X of the facility is connected to a 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 PV 110. The converter 210 may be referred to as a unidirectional DC / DC converter.

[0021] Converter 220 converts the voltage of the DC power output from BT 120. Converter 220 converts the voltage of the DC power output from converter 210, converter 230, and converter 240. Converter 220 may be referred to as a bidirectional DC / DC converter.

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

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

[0024] Converter 240 converts DC power output from converter 210, converter 220, or converter 230 into AC power. Converter 240 converts AC power supplied from power grid 11 into DC power. Converter 240 may be referred to as a bidirectional inverter. In the embodiment, converter 240 constitutes a first converter that converts DC power output from a distributed power source (e.g., PV 110, BT 120) installed in the facility into AC power. Converter 240 also constitutes a first converter that converts DC power output from a second converter into AC power.

[0025] Here, the converter 210, the converter 220, the converter 230, and the converter 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 unit 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 configured by a single integrated circuit (IC), or may be configured by two or more circuits (such as integrated circuits and / or discrete circuits) that are communicatively 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 also be a device (for example, an EMS; Energy Management System) installed separately from the PCS 200.

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

[0029] In the embodiment, PCS 200 is an example of a specific power converter having converter 240 (first converter) and 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 ELB 310 (electric power system 11) described below and converter 240. Switch 272 is a switch that switches the electrical connection state between in-facility breaker 320 described below and converter 240. Switch 273 is a switch that switches between a grid-connected state in which the facility is connected to power system 11 and a disconnected state in which the facility is disconnected from power system 11. Note that, hereinafter, the state in which the facility is disconnected from power system 11 will be referred to as the disconnected state.

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

[0033] The ELB 310 is a breaker that interrupts a ground fault when a ground fault occurs. The ELB 310 is electrically connected to the power grid 11. The ELB 310 may also be referred to as a ground fault circuit interrupter.

[0034] The in-house breaker 320 is a breaker that interrupts the in-house wiring 300X when the current in the in-house wiring 300X exceeds a threshold. The in-house breaker 320 is connected to the in-house wiring 300X. The in-house breaker 320 may be called a safety breaker or a circuit breaker.

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

[0036] 1 and 2, the grounding mechanism 330 connects one phase of the indoor wiring 300X, i.e., the neutral wire (generally called terminal N) of the converter 240, to the ground terminal 331. This is the same whether the isolated operation output of the converter 240 is 100V or 200V.

[0037] The interface 400 is an interface electrically connected to the PCS 200 (specifically, the converter 230). The interface 400 is an interface electrically connected to an external power supply device 500. In the 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, interface 400 may be disposed inside PCS 200 or on the outer wall of a building that constitutes the facility. Interface 400 may have a connector shape or a terminal shape.

[0039] The external power supply device 500 includes a PCS 510 and an external power supply 520. The external power supply device 500 may be a non-insulated power supply device. The PCS 510 converts DC power output from the external power supply 520 into AC power. The PCS 510 may also convert AC power output from the PCS 200 into DC power. The PCS 510 may be a non-insulated PCS. The external power supply 520 is a power source such as a solar cell or a storage battery.

[0040] In this embodiment, the external power supply device 500 is electrically connected to the ground terminal 530. Variations in the manner of connection between the external power supply device 500 and the ground terminal 530 will be described later (see FIGS. 3 to 5).

[0041] (assignment) In the embodiment, it is assumed that the PCS 200 has a ground fault detection function. Specifically, the PCS 200 is configured to determine that a ground fault has occurred when a specific condition is satisfied, and then stop 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 and a predetermined time. Specifically, the specific condition is a condition in which a state in which the ground fault current in the wiring between the PCS 200 and the ground terminal 331 is equal to or greater than a predetermined threshold continues for a predetermined time. For example, the predetermined threshold may be set based on the ground capacitance of the PV 110 that may be connected to the PCS 200. The predetermined time may be determined in advance based on the safety design of the PCS 200, etc. It should be noted that at least a portion of the wiring between the PCS 200 and the ground terminal 331 is common to the wiring between the external power supply device 500 and the ground terminal 331.

[0043] As described above, the grounding mechanism 330 grounds the indoor wiring 300X in the disconnected state. The external power supply 500 is electrically connected to the ground terminal 530. Therefore, assuming a state in which the external power supply 500 is connected to the PCS 200, a ground fault current between the external power supply 500 and the ground terminal 331 will activate the ground fault detection function, and a malfunction of the ground fault detection of the PCS 200 may occur despite normal operation.

[0044] (Connection mode) The following describes variations in the manner of connection between the external power supply device 500 and the ground terminal 530.

[0045] First, as shown in Fig. 3, an external power supply device 500A may be a device including a PCS 510A and a 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, a grid-connection terminal 551A, an independent 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 BT 520A. 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 AC power supplied from PCS 200 (interface 400) into DC power. Converter 542A may be referred to as a bidirectional inverter.

[0049] The independent connection end 552A is connected to the interface 400. That is, in the disconnected state, the independent connection end 552A outputs power from the PCS 510A to the PCS 200. In the disconnected state, the independent connection end 552A may input power from the PCS 200 to the PCS 510A.

[0050] The switch 561A is a switch that switches the electrical connection state between the BT 520A and the converter 541A. The switch 562A is a switch that switches the electrical connection state between the grid-connected connection end 551A and the converter 542A. The switch 563A is a switch that switches the electrical connection state between the independent connection end 552A and the converter 542A.

[0051] The grounding mechanism 570A is a grounding mechanism that grounds the external power supply device 500A in a disconnected state. The grounding mechanism 570A is grounded separately from the above-described grounding mechanism 330. Specifically, the grounding mechanism 570A is a mechanism that grounds the wiring between the PCS 542A and the independent connection end 552A in a disconnected state. The grounding mechanism 570A may be referred to as a specific grounding mechanism to distinguish it from the grounding mechanism 330. Alternatively, to distinguish between the grounding mechanism 330 and the grounding mechanism 570A, the grounding mechanism 330 may be referred to as a first grounding mechanism, and the grounding mechanism 570A may be referred to as a second grounding mechanism. The grounding mechanism 570A has a grounding end 571A and a switch 572A. The switch 572A electrically connects the grounding end 571A and the PCS 510A in a disconnected state, while not electrically connecting the grounding end 571A and the PCS 510A when the PCS 510A is in a grid-connected state.

[0052] 3 illustrates an example in which the grounding mechanism 570A is disposed inside the PCS 510A. However, the embodiment is not limited to this. The grounding mechanism 570A may be disposed outside the PCS 510A.

[0053] The BT520A is a distributed power source that charges and discharges power. For example, the BT520A is configured with a storage cell. To distinguish between the BT120 and the BT520A, the BT120 may be referred to as a first storage battery, and the BT520A may be referred to as a second storage battery.

[0054] Here, Fig. 3 illustrates a connection state in a disconnected state. The PCS 510A may be an insulated PCS or a non-insulated PCS. The ground terminal 571A is an example of the ground terminal 530 shown in Figs. 1 and 2. Although Fig. 3 illustrates a BT 520A as the external power supply 520, the external power supply 520 may also be a solar cell.

[0055] 3, in the disconnected state, a ground fault current in the wiring between the ground terminal 571A and the ground terminal 331 may cause the ground fault detection of the PCS 200 to malfunction. For example, it should be noted that even if the converter 541A is an isolation transformer type converter, the ground fault detection of the PCS 200 may malfunction.

[0056] Second, as shown in Fig. 4, an external power supply device 500B may be a device including a PCS 510B and a PV 520B. The external power supply device 500B is an example of the external power supply device 500 described above.

[0057] The PCS 510B includes a converter 541B, a converter 542B, a grid-connection terminal 551B, an independent connection terminal 552B, a switch 561B, a switch 562B, and a switch 563B.

[0058] Converter 541B converts the voltage of the DC power output from PV 520B. Converter 541B may be referred to as a unidirectional DC / DC converter.

[0059] Converter 542B converts the DC power output from converter 541B into AC power. Converter 542B may be a one-way inverter.

[0060] The independent connection end 552B is connected to the interface 400. That is, the independent connection end 552B outputs power from the PCS 510B to the PCS 200 in the disconnected state.

[0061] The switch 561B is a switch that switches the electrical connection state between the PV 520B and the converter 541B. The switch 562B is a switch that switches the electrical connection state between the grid-connected connection end 551B and the converter 542B. The switch 563B is a switch that switches the electrical connection state between the independent connection end 552B and the converter 542B.

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

[0063] 4 illustrates the connection state of the switch 563B of the PCS 510B in a disconnected state in which the indoor wiring 300X of the facility is disconnected from the power grid 11 as shown in FIG. 3. The PCS 510B is a non-insulated PCS. The PCS 510B is grounded by a circuit earth 571B. The PV 520B is grounded by an earth 521B. The circuit earth 571B is an example of the ground terminal 530 shown in FIG. 2.

[0064] 4, in the disconnected state, a ground fault current in the wiring between circuit earth 571B and ground terminal 331 may cause a malfunction of the ground fault detection of PCS 200. It should be noted that a ground fault detection malfunction does not occur in the connected state but occurs in the disconnected state (isolated operation). Therefore, it is difficult to detect a ground fault detection malfunction in advance.

[0065] 5, an external power supply device 500C may be a device including a PCS 510C and a PV 520C. The external power supply device 500C is an example of the external power supply device 500 described above.

[0066] The PCS 510C includes a converter 541C, a converter 542C, a grid-connection terminal 551C, an isolated 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 PV 520C. The converter 541C may be referred to as a unidirectional DC / DC converter.

[0068] Converter 542C converts the DC power output from converter 541C into AC power. Converter 542C may be a one-way inverter.

[0069] The independent connection end 552C is connected to the interface 400. That is, the independent connection end 552C outputs power from the PCS 510C to the PCS 200 in the disconnected state.

[0070] The switch 561C is a switch that switches the electrical connection state between the PV 520C and the converter 541C. The switch 562C is a switch that switches the electrical connection state between the grid-connected connection end 551C and the converter 542C. The switch 563C is a switch that switches the electrical connection state between the independent connection end 552C and the converter 542C.

[0071] PV520C is a distributed power source that generates electricity in response to sunlight or other light. For example, PV520C is composed of solar panels.

[0072] Here, FIG. 5 illustrates a connection state in a disconnected state. The PCS 510C is a non-insulated PCS. The capacitance to ground of the PV 520C is greater than the capacitance to ground of the PV 110. For example, the PV 110 may be a crystalline solar cell, and the PV 520C may be an amorphous solar cell. The PV 520C is grounded by an earth 521C. The earth 521C is an example of the ground terminal 530 shown in FIG. 2.

[0073] 5, in the disconnected state, a ground fault current in the wiring between earth 521C and ground terminal 331 may cause the ground fault detection of PCS200 to malfunction. For example, assuming a case in which PCS510C has a ground fault detection function, if the capacitance to the ground of PV520C is greater than the capacitance to the ground of PV110, the predetermined threshold used in the ground fault detection function of PCS510C is greater than the predetermined threshold used in the ground fault detection function of PCS200. Therefore, it should be noted that a ground fault may be detected by PCS200 without being detected by PV520C.

[0074] (Example of operation) An example of operation for solving the above-mentioned problem will be described below.

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

[0076] Specifically, in the disconnected state, if the state in which the ground fault current is equal to or greater than a predetermined threshold continues for a specific time that is shorter than a predetermined time, 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. In other words, in the disconnected state, if a malfunction of the ground fault detection of the PCS 200 is expected, 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.

[0077] On the other hand, the control unit 250 may determine that power can be received from the external power supply device 500 when, in the disconnected state, the state in which the ground fault current is equal to or greater than the predetermined threshold value does not continue for a specific time that is shorter than the predetermined time. In other words, the control unit 250 may determine that power can be received from the external power supply device 500 when, in the disconnected state, malfunction of the ground fault detection of the PCS 200 is not expected.

[0078] Here, the condition that the state in which 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 to be a condition for determining whether or not a malfunction of the ground fault detection of the PCS 200 is expected in the disconnected state. In other words, if the determination condition is satisfied, it may be determined that a malfunction of the ground fault detection of the PCS 200 is expected in the disconnected state, and if the determination condition is not satisfied, it may be determined that a malfunction of the ground fault detection of the PCS 200 is not expected in the disconnected state.

[0079] When it is determined that power cannot be received from the external power supply device 500, the control unit 250 may issue a notification or a notice that power cannot be received from the external power supply device 500. When it is determined that power can be received from the external power supply device 500, the control unit 250 may issue a notification or a notice that power can be received from the external power supply device 500. The notification may be to a user of the PCS200. The notification may be one or more notifications selected from a sound and a display. The notification may be the transmission of information to a notification recipient. The notification recipient may be an EMS, or one or more recipients selected from a server that manages the PCS200 (e.g., an equipment management server), a server that manages the power of the facility (e.g., a power management server), and a terminal carried by a user of the PCS200.

[0080] When the received power from the external power supply device 500 is equal to or less than a first threshold in the disconnected state, the control unit 250 may issue an alert or notification that power is not being received from the external power supply device 500. The first threshold may be set arbitrarily as long as it is smaller than the power corresponding to a predetermined threshold that defines a specific condition for detecting a ground fault in the PCS 200. A state in which the received power from the external power supply device 500 is equal to or less than the first threshold may be assumed to be a state in which the external power supply device 500 is not ready to output power (e.g., powered off) or a state in which the external power supply device 500 is not connected to the PCS 200. The alert may be one or more of an audible alert and a visual alert. The notification may be a transmission of information to a notification recipient. The notification recipient may be an EMS, a server that manages the PCS 200 (e.g., an equipment management server), a server that manages the power of the facility (e.g., a power management server), or a terminal owned by a user of the PCS 200.

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

[0082] The control unit 250 may execute the determination process during the installation process of the PCS 200 (first converter, second converter) and the external power supply device 500. In such a case, the control unit 250 may store the result of the determination process, and when performing independent operation in the parallel-off state, may determine whether or not power can be received from the external power supply device 500 based on the result of the determination process.

[0083] The installation process may be, for example, a construction process for connecting the external power supply device 500 to the PCS200, or, if the external power supply device 500 has a movable configuration, may be a construction process for temporarily connecting the external power supply device 500 to the PCS200.

[0084] The control unit 250 may execute the determination process in the process of starting autonomous operation of the facility after installing the PCS 200 (first converter, second converter) and the external power supply device 500. The control unit 250 may execute the determination process every time autonomous operation is started in the disconnected state.

[0085] Secondly, the control unit 250 may be configured as a control unit that executes specific control regarding the external power supply unit 500 when, in a disconnected state, the grounding mechanism 330 grounds the wiring within the facility (indoor wiring 300X), and when power is received from the external power supply unit 500, specific conditions for detecting a ground fault in the PCS200 (specific power conversion device) may be satisfied.

[0086] Here, the case where the specific condition may be satisfied may be considered to be the case where the above-described determination condition is satisfied. In other words, the case where the specific condition may be satisfied may be considered to be the case where a malfunction of the ground fault detection of the PCS 200 is expected in the disconnected state.

[0087] As the specific control, the control unit 250 may stop the power conversion operation of the PCS 230 (second converter). That is, the control unit 250 may stop drawing power from the external power supply device 500 to the PCS 230 (second converter).

[0088] As the 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 send a control command to the control unit of the PCS 510 to instruct the external power supply device 500 to stop the power output.

[0089] As the 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, if the control unit 250 can directly control the grounding mechanism 570A, the control unit 250 may send a command to the grounding mechanism 570A to control the external power supply device 500 so that it is not grounded in the disconnected state. If the PCS 510A controls the grounding mechanism 570A, the control unit 250 may send a command to the control unit of the PCS 510A to control the grounding mechanism 570A so that the external power supply device 500 is not grounded in the disconnected state, thereby indirectly controlling the grounding mechanism 570A.

[0090] As the specific control, the control unit 250 may control the external power supply 500 so that the output current or output power of the external power supply 500 is less than a specific threshold. The specific threshold is a value smaller than the current or power corresponding to a predetermined threshold that defines a specific condition for detecting a ground fault in the PCS 200. The specific threshold may be expressed as a percentage (e.g., 20%) of the rated output of the PCS 510. For example, the control unit 250 may send a control command to the control unit of the PCS 510 to instruct the external power supply 500 to reduce the current or power to less than the specific threshold.

[0091] (Power supply control method) A power supply control method according to an embodiment will be described below.

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

[0093] 6, in step S10, preparation of the external power supply device 500 is performed. 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 it can output power by, for example, turning on the power of the external power supply device 500.

[0094] In step S11, the switch group (switch 263, switch 271, switch 272, switch 273, switch 332) is switched to a state in which the switches are in a disconnected state (see FIG. 2). The switching of the switch group may be performed by the control unit 250 or 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 performed by the control unit 250 controlling the converter 230.

[0096] In step S13, the control unit 250 determines whether a determination condition is satisfied. For example, the control unit 250 determines whether 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 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 cannot be received from the external power supply device 500 in the disconnected state (i.e., the state in which the grounding mechanism 330 grounds the indoor wiring 300X). The control unit 250 may store the determination result. The control unit 250 may issue a notification or notification that power cannot be received from the external power supply device 500.

[0098] In step S15, the control unit 250 determines that power can be received from the external power supply device 500 in the disconnected state (i.e., a state in which the grounding mechanism 330 grounds the indoor wiring 300X). The control unit 250 may store the determination result. The control unit 250 may also issue a notification or notification that power can be received from the external power supply device 500.

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

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

[0101] Secondly, a case will be described in which the determination process is executed in the process of starting independent operation after the installation of the PCS 200 and the external power supply device 500.

[0102] 7, in step S20, the PCS 200 receives an instruction to start independent operation. The reception of the instruction to start independent operation may be interpreted as the detection of a power outage.

[0103] In step S21, the switch group (switch 263, switch 271, switch 272, switch 273, switch 332) is switched to a state in which the switches are in a disconnected state (see FIG. 2). The switching of the switch group may be performed by control unit 250 or 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 performed by the control unit 250 controlling the converter 230.

[0105] In step S23, the control unit 250 determines whether a determination condition is satisfied. For example, the control unit 250 determines whether 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 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 cannot be received from the external power supply device 500 in the disconnected state (i.e., the state in which the grounding mechanism 330 grounds the indoor wiring 300X). The control unit 250 may store the determination result. The control unit 250 may issue a notification or notification that power cannot be received from the external power supply device 500.

[0107] In step S25, the control unit 250 determines that power can be received from the external power supply device 500 in the disconnected state (i.e., a state in which the grounding mechanism 330 grounds the indoor wiring 300X). The control unit 250 may store the determination result. The control unit 250 may also issue a notification or notification that power can be received from the external power supply device 500.

[0108] In step S26, the PCS 200 receives an instruction to end the independent operation. The reception of the instruction to end the independent operation may be interpreted as the detection of recovery from power outage.

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

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

[0111] Thirdly, a case will be described in which specific control is executed for the external power supply device 500. Here, the specific control in the parallel-off state (independent operation) will be mainly described, and therefore some of the determinations regarding whether the determination conditions are satisfied (for example, steps S22, S24, S25, S26, S27, S28, etc. shown in FIG. 7) will be omitted.

[0112] 8, in step S30, the PCS 200 receives an instruction to start independent operation. The reception of the instruction to start independent 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 a state in which the switches are in a disconnected state (see FIG. 2). The switching of the switch group may be performed by the control unit 250 or by other means.

[0114] In step S31, the control unit 250 determines whether or not the determination condition is satisfied. As described above, whether or not the determination condition is satisfied may be determined during the installation process of the PCS 200 and the external power supply device 500 (see FIG. 6), or may be determined during the process of starting independent 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 a determination condition is satisfied. For example, the control unit 250 determines whether 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 continues for a predetermined time. If the determination condition is satisfied, the process of step S33 is executed, and if 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 processing to stop the power conversion operation of the PCS 230. The specific control may be processing to stop the power output of the external power supply device 500. The specific control may be processing to 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. The specific control may be processing to control the output current or output power of the external power supply device 500 to be less than a specific threshold.

[0117] In step 34, the control unit 250 may execute normal control. Normal control is a term that contrasts with specific control, and may be any control other than specific control. For example, normal control may be control that allows power to be received from the external power supply device 500 without any particular restrictions.

[0118] (Action and effect) In the embodiment, the control unit 250 executes a determination process to determine whether or not to allow power to be received from the external power supply 500 in a state in which the grounding mechanism 330 grounds the wiring within the facility (indoor wiring 300X) in a disconnected state. With this configuration, it is possible to determine whether or not to allow power to be received from the external power supply 500 depending on whether or not a ground fault current between the external power supply 500 and the ground terminal 331 could cause a malfunction of the ground fault detection of the PCS 200. Therefore, assuming a case in which the external power supply 500 is connected, it is possible to appropriately suppress a malfunction of the ground fault detection of the PCS 200.

[0119] In the embodiment, when it is determined that power cannot be received from the external power supply device 500, the control unit 250 may execute a notification or notification to that effect. With such a configuration, it is possible to know that power cannot be expected to be received from the external power supply device 500, and it is possible to appropriately formulate a plan for autonomous operation, etc.

[0120] In the embodiment, the control unit 250 executes specific control on the external power supply 500 when a specific condition for detecting a ground fault in the PCS 200 (specific power conversion device) may be satisfied by receiving power from the external power supply 500 while the grounding mechanism 330 is in a disconnected state and grounds the wiring within the facility (indoor wiring 300X). Here, the specific control may be a process for stopping the power conversion operation of the PCS 230. The specific control may be a process for stopping the power output of the external power supply 500. The specific control may be a process for controlling the specific grounding mechanism (e.g., the grounding mechanism 570A shown in FIG. 3) so that the external power supply 500 is not grounded. The specific control may be a process for controlling the output current or output power of the external power supply 500 to be less than a specific threshold. With this configuration, when a case in which the external power supply 500 is connected is assumed, it is possible to appropriately suppress malfunction of the ground fault detection of the PCS 200.

[0121] [Change Example 1] Modification 1 of the embodiment will be described below, focusing mainly on the differences from the embodiment.

[0122] In the embodiment, the grid connection terminals of the external power supply device 500 (the grid connection terminal 551A shown in FIG. 3, the grid connection terminal 551B shown in FIG. 4, and the grid connection terminal 551C shown in FIG. 5) are connected to the interface 400 of the PCS 200. In contrast, in the first modified example, the grid connection terminals of the external power supply device 500 are connected to wiring within the facility (indoor wiring 300X) without being connected to the power grid 11 in the disconnected state. That is, in the disconnected 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, an external power supply device 500D may be a device having a PCS 510D and a BT 520D. The PCS 510D and the BT 520D are similar to the PCS 510A and the BT 520A described in Fig. 3, and therefore details thereof will be omitted.

[0124] Here, in the disconnected state, the grid-connected terminal 551D is connected to the in-facility breaker 320 (i.e., the indoor wiring 300X) without being connected to the power grid 11. The independent connection terminal 552D is connected to the interface 400 of the PCS 200, similar to the independent connection terminal 552A described in FIG.

[0125] In Modification 1, as specific control, the control unit 250 outputs power from the grid connection end 551D of the external power supply device 500. That is, when the determination condition is satisfied, the control unit 250 outputs power from the grid connection end 551D without using the independent connection end 552D even in a parallel-off state (independent operation). In other words, the control unit 250 turns off the switch 563D to not connect the converter 542D to the independent connection end 552D, and turns on the switch 562D to connect the converter 542D to the grid connection end 551D.

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

[0127] If the determination condition is not satisfied, the control unit 250 outputs power from the independent connection terminal 552D as usual without using the grid connection terminal 551D. In other words, the control unit 250 turns off the switch 562D to not connect the converter 542D to the grid connection terminal 551D, and turns on the switch 563D to connect the converter 542D to the independent connection terminal 552D. This type of control may be considered an example of normal control.

[0128] (Action and effect) In the first modification, the control unit 250 may output power from the grid connection end 551D of the external power supply device 500 as specific control under the assumption that the grid connection end 551D of the external power supply device 500D is connected to the in-facility breaker 320 (i.e., the indoor wiring 300X) without being connected to the power grid 11 in the disconnected state. With this configuration, the output power of the external power supply device 500 does not pass through the PCS 200, and therefore, malfunction of the ground fault detection of the PCS 200 can be appropriately suppressed.

[0129] [Other embodiments] Although the present invention has been described by the above-mentioned embodiments, the descriptions and drawings that form part of this disclosure should not be understood to limit the present invention. From this disclosure, various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art.

[0130] In the above disclosure, the determination condition is, for example, that the ground fault current between the external power supply 500 and the ground terminal 331 remains equal to or greater than a predetermined threshold for a specific period of time. However, the above disclosure is not limited to this. The determination condition may be any condition that determines whether a specific condition can be satisfied in a disconnected state. In other words, the determination condition may be any condition that determines whether a malfunction of the ground fault detection of the PCS 200 is anticipated in a disconnected state. For example, the determination condition may be determined based on the behavior of the ground fault current that may cause a malfunction of the ground fault detection of the PCS 200 in a disconnected state.

[0131] In the above disclosure, the case where the control unit 250 is the control unit of the PCS200 has been mainly described. However, the above disclosure is not limited to this. The control unit 250 may be configured by a control unit of the PCS200 and a control unit of the PCS510 that can communicate with each other. The control unit 250 may be configured by a control unit of the PCS200 and an EMS that can communicate with each other. The control unit 250 may be configured by a control unit of the PCS200, a control unit of the PCS510, and an EMS that can communicate with each other. The control unit 250 may be configured by only the EMS.

[0132] In the above disclosure, the PV 110 and the BT 120 are 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, a device including a storage battery and a PCS, and a device including a solar cell and a PCS have been exemplified as the external power supply device 500. However, the above disclosure is not limited to this. The external power supply device 500 may also be a device including a PCS and 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. The external power supply device 500 may also be an engine generator without a PCS.

[0134] Although not specifically mentioned in the above disclosure, the disconnected state may be read as an independent state. "External" may mean at least outside the PCS 200. "External" may mean outside the facility where the PCS 200 is installed. "Power supply device" may be considered a term indicating a device including a power supply and a PCS, or may be considered a term indicating a power supply that does not require a PCS.

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

[0136] [Note] The above disclosure may be expressed as follows:

[0137] A first feature is a power supply system including a first converter that converts DC power output from a distributed power source installed in a facility into AC power, 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 that grounds wiring within the facility when the facility is in a disconnected state in which the facility is disconnected from the power grid, the first converter converts the DC power output from the second converter into AC power, and the control unit executes a determination process to determine whether power can be received from the external power supply device when the grounding mechanism grounds the wiring within the facility in the disconnected state.

[0138] A second feature is the power supply system of the first feature, wherein the control unit executes the determination process before a specific condition for detecting a ground fault in a specific power conversion device having the first converter and the second converter is satisfied.

[0139] A third feature is the power supply system of the second feature, wherein the specific condition is that a state in which a ground fault current between the external power supply device and a ground end of wiring within the facility is equal to or greater than a predetermined threshold continues for a predetermined time, and the control unit determines that power cannot be received from the external power supply device when, in the disconnected state, the state in which the ground fault current is equal to or greater than the predetermined threshold continues for a specific time that is shorter than the predetermined time.

[0140] A fourth feature is a power supply system in which, in any one of the first to third features, the control unit issues an alert or notification to the effect that power cannot be received from the external power supply device when it is determined that power cannot be received from the external power supply device.

[0141] A fifth feature is a power supply system in which, in any one of the first to fourth features, the control unit issues an alert or notification that power is not being received from the external power supply device when the received power from the external power supply device is equal to or less than a first threshold value in the disconnected state.

[0142] A sixth feature is a power supply system in which, in any one of the first to fifth features, the control unit executes the determination process when the received power from the external power supply device in the disconnected state is greater than or equal to a second threshold.

[0143] A seventh feature is a power supply system in any one of the first to seventh features, wherein the control unit executes the determination process during an installation process of the first converter, the second converter, and the external power supply device.

[0144] An eighth feature is a power supply system in which, in any one of the first to eighth features, the control unit executes the determination process in a process of starting autonomous operation of the facility after installation of the first converter, the second converter, and the external power supply device. [Explanation of symbols]

[0145] 1...power supply system, 11...power system, 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 section, 261 to 263...switch, 271 to 273...switch, 300...distribution board, 300X...AC wiring (indoor wiring), 310...ELB, 320...facility breaker, 330...earthing mechanism, 331...grounding end, 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 end, 541A, 541B, 541C, 541D...Converter, 542A, 542B, 542C, 542D...Converter, 551A, 551B, 551C, 551D...Grid connection end, 552A, 552B, 552C, 552D...Isolating connection end, 561A, 561B, 561C, 561D...Switch, 562A, 562B, 562C, 562D...Switch, 563A, 563B, 563C, 563D...Switch, 570A, 570D...Earthing mechanism, 571A, 571D...Ground terminal, 571B...Circuit earth, 572A, 572D...Switch

Claims

1. a first converter that converts DC power output from a distributed power source installed in the facility into AC power; a second converter that converts AC power output from the external power supply device into DC power; a control unit, the facility has a grounding mechanism that grounds wiring within the facility in a disconnected state in which 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 a determination process to determine whether power can be received from the external power supply device in a state in which the grounding mechanism grounds wiring within the facility in the disconnected state, and the determination process is a process of determining that power cannot be received from the external power supply device when a determination condition is satisfied in the disconnected state, and determining that power can be received from the external power supply device when the determination condition is not satisfied in the disconnected state, A power supply system, wherein the determination condition is that a state in which a ground fault current between the external power supply device and a ground end of wiring within the facility is equal to or greater than a predetermined threshold continues for a specific period of time.

2. The power supply system according to claim 1 , wherein the control unit executes the determination process before a specific condition for detecting a ground fault is satisfied in a specific power conversion device including the first converter and the second converter.

3. the specific condition is a condition in which the state in which the ground fault current is equal to or greater than the predetermined threshold continues for a predetermined time, The power supply system according to claim 2 , wherein the specific time is shorter than the predetermined time.

4. The power supply system according to claim 1 , wherein, when it is determined that power cannot be received from the external power supply device, the control unit issues a notification or a notice to that effect.

5. 2. The power supply system according to claim 1, wherein the control unit issues an alert or notification that power is not being received from the external power supply device when the power received from the external power supply device is equal to or less than a first threshold value in the disconnected state.

6. The power supply system according to claim 1 , wherein the control unit executes the determination process when the power received from the external power supply device in the disconnected state is equal to or greater than a second threshold value.

7. The power supply system according to claim 1 , wherein the control unit executes the determination process during an installation process of the first converter, the second converter, and the external power supply device.

8. The power supply system according to claim 1 , wherein the control unit executes the determination process in a step of starting autonomous operation of the facility after installation of the first converter, the second converter, and the external power supply device.

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