Power System

Abstract

This power supply system comprises: a first converter that converts, into AC power, DC power which is output from a distributed power supply installed in a facility; a second converter that converts, into DC power, AC power which is output from an external power supply device; and a power interface that is for receiving the AC power output from the external power supply device. The facility has a grounding mechanism that grounds wiring in the facility when the facility is disconnected from a power system. The first converter converts DC power output from the second converter into AC power. The second converter is an isolated converter.

Description

[Technical Field]

[0001] The present disclosure relates to power supply systems. [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

[0005] 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 power interface for receiving the AC power output from the external power supply device, wherein the facility has a grounding mechanism that grounds wiring within the facility when the facility is disconnected from the power grid, the first converter converts DC power output from the second converter into AC power, and the second converter is an isolated converter. [Brief explanation of the drawings]

[0006] [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 a power supply system 1 (in a disconnected state) according to the first modified example. [Figure 4] FIG. 4 is a diagram showing a power supply system 1 (in a disconnected state) according to the first modified example. [Figure 5] FIG. 5 is a diagram showing a power supply system 1 (in a disconnected state) according to the first modified example. DETAILED DESCRIPTION OF THE INVENTION

[0007] 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.

[0008] [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 has a solar cell device (hereinafter referred to as PV) 110, a power storage device (hereinafter referred to as BT) 120, a load 140, and a measuring device 150. The power supply system 1 also has a PCS (Power Conditioning System) 200 and a distribution board 300. The power supply system 1 also has an interface 400 and an external power supply device 500.

[0009] 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 is indoor electrical wiring and electrical equipment.

[0010] 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.

[0011] The BT 120 is a distributed power source that charges and discharges power. For example, the BT 120 is configured by a power storage cell. The BT 120 may also be referred to as a stationary power storage device. 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.

[0012] 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 also be referred to as in-house wiring 300X.

[0013] 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.

[0014] 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).

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] Here, the converter 230 is an isolated converter. For example, the converter 230 may include an isolation transformer. Although not particularly limited, a half-bridge circuit, a full-bridge circuit, a flyback circuit, a forward circuit, a push-pull circuit, or the like may be used as a circuit for isolation.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] In the embodiment, the control unit 250 configures a control unit that executes control (hereinafter, "specific control") to receive power from the external power supply device 500 after the grounding mechanism 330 grounds the indoor wiring 300X. The specific control may include the following controls. 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.

[0025] 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.

[0026] 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.

[0027] The distribution board 300 includes an ELB (Earth Leakage Breaker) 310 and an in-facility breaker 320 .

[0028] 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.

[0029] The in-house breaker 320 is a breaker that cuts off 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.

[0030] In the embodiment, the facility includes a grounding mechanism 330 that grounds the in-home wiring 300X in a disconnected state in which the facility (PCS 200) is disconnected from the power grid 11. 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 ), and electrically connects the grounding terminal 331 to the distribution board 300 in a disconnected state (see FIG. 2 ).

[0031] 1 and 2, the grounding mechanism 330 connects one phase of the in-house 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.

[0032] 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.

[0033] 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.

[0034] 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 power storage device.

[0035] (Action and effect) In the embodiment, the power supply system 1 includes an isolated converter as the converter 230 that converts AC power output from the external power supply device 500 into DC power, under the assumption that the facility has a grounding mechanism 330 that grounds the indoor wiring 300X in a disconnected state. With this configuration, a smaller configuration can be adopted as the insulating configuration for suppressing a ground fault between the PCS 510 of the external power supply device 500 and the grounding end 331, compared to a case in which the converter 240 that performs power conversion of a larger power than the converter 230 is an isolated type. In other words, a ground fault between the PCS 510 of the external power supply device 500 and the grounding end 331 can be appropriately suppressed.

[0036] In the embodiment, the control unit 250 executes specific control to receive power from the external power supply device 500 after the grounding mechanism 330 has grounded the indoor wiring 300X. This configuration can prevent an unsafe state in which power is received from the external power supply device 500 before the indoor wiring 300X has been grounded by the grounding mechanism 330. [Change Example 1] Modification 1 of the embodiment will be described below, focusing mainly on the differences from the embodiment.

[0037] In Modification Example 1, a description will be given of a variation of the above-mentioned PCS 200. The variations of the PCS 200 include the following options.

[0038] In option 1, as shown in Fig. 3, the PCS 200 may not be connected to the PV 110 but may be connected to the BT 120. That is, the PCS 200 may not have the converter 210 and the switch 261, as compared to the examples shown in Figs.

[0039] In such a case, the external power supply device 500 may be a device including a PCS 510A and a PV 520A. The PCS 510A converts DC power output from the PV 520A into AC power. The PCS 510A may be a non-insulated PCS. The PV 520A is an external power supply that generates power in response to light such as sunlight.

[0040] In option 2, as shown in Fig. 4, the PCS 200 may not be connected to the BT 120 but may be connected to the PV 110. That is, the PCS 200 may not have the converter 220 and the switch 262, as compared to the examples shown in Figs.

[0041] In such a case, the external power supply device 500 may be a device including a PCS 510B and a BT 520B. The PCS 510B converts the DC power output from the BT 520B into AC power, and also converts the AC power output from the converter 230 into DC power. That is, the PCS 510B may be a bidirectional inverter. The PCS 510B may be a non-isolated PCS. The BT 520B is an external power supply that charges and discharges power.

[0042] In option 3, as shown in Fig. 5, the PCS 200 may not be connected to the BT 120 but may be connected to the PV 110. That is, the PCS 200 may not have the converter 220 and the switch 262, as compared to the examples shown in Figs.

[0043] In such a case, the external power supply device 500 may be a device including a PCS 510C and a PV 520C. The PCS 510C converts DC power output from the PV 520C into AC power. The PCS 510C may be a non-insulated PCS. The PV 520C is an external power supply that generates power in response to light such as sunlight. The capacitance to ground of the PV 520C may be greater than the capacitance to ground of the PV 110. In a first modification, the PV 520C is an external power supply that generates power in response to light such as sunlight. The PV 520C is an example of an external solar cell that has a capacitance to ground greater than the capacitance to ground of the PV 110.

[0044] Although not particularly limited, PV110 may be a crystalline solar cell, and PV520C may be an amorphous solar cell.

[0045] In option 3, it is assumed that the setting value used for ground fault detection of PCS200 is set based on the capacitance to ground of PV110 that may be connected to PCS200. In such a case, when PV520C, an amorphous solar cell having a capacitance to ground greater than the capacitance to ground of PV110, a crystalline solar cell, is connected, it is necessary to change the setting value used for ground fault detection of PCS200 in order to prevent malfunction of the ground fault detection function of PCS200. However, it should be noted that because converter 230 is an isolated converter, ground faults between PCS510C of external power supply device 500 and ground terminal 331 can be appropriately prevented without changing the setting value used for ground fault detection of PCS200.

[0046] [Other embodiments] Although the present disclosure has been described by the above-mentioned embodiments, the descriptions and drawings forming part of this disclosure should not be understood as limiting the present invention. From this disclosure, various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art.

[0047] 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.

[0048] In the above disclosure, a device including a power storage device and a PCS, and a device including a solar cell device 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.

[0049] 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.

[0050] 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)).

[0051] The above disclosure may have the following problems and effects.

[0052] 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).

[0053] After careful consideration, the inventors discovered that if the neutral wire N needs to be grounded in the disconnected state, a ground fault may occur between the grounded end of the wiring within the facility and the PCS unless any measures are taken.

[0054] According to the above disclosure, it is possible to provide a power supply system that can appropriately suppress ground faults that occur between the ground end of wiring within a facility and the PCS.

[0055] [Note] The above disclosure may be expressed as follows: 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 power interface for receiving the AC power output from the external power supply device, wherein the facility has a grounding mechanism that grounds wiring within the facility when the facility is disconnected from an electric power grid, the first converter converts DC power output from the second converter into AC power, and the second converter is an isolated converter.

[0056] A second feature is a power supply system according to the first feature, further comprising a control unit that executes control to receive power from the external power supply device after the wiring within the facility is grounded by the grounding mechanism.

[0057] A third feature is the power supply system according to the first or second feature, wherein the second converter is a converter that converts DC power output from the distributed power source into AC power.

[0058] A fourth feature is a power supply system according to any one of the first to third features, wherein the distributed power source is a solar cell, the external power source of the external power supply device is an external solar cell, and the capacitance to ground of the external solar cell is greater than the capacitance to ground of the solar cell.

[0059] A fifth feature is the power supply system according to any one of the first to fourth features, wherein the external power supply device is a non-insulated external power supply device. [Explanation of symbols]

[0060] 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...switches, 271 to 273...switches, 300...distribution board, 300X...AC wiring (in-house wiring), 310...ELB, 320...in-house breaker, 330...earthing mechanism, 331...earthing end, 332...switch, 400...interface, 500...external power supply device, 510, 510A, 510B, 510C...PCS, 520...external power supply, 520A...PV, 520B...BT, 520C...PV

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 power interface for receiving AC power output from the external power supply device; the facility has a grounding mechanism that grounds wiring within the facility when the facility is disconnected from the power grid; the first converter converts the DC power output from the second converter into AC power; the second converter is an isolated converter; A power supply system, wherein the external power supply device has a capacitance to ground greater than the capacitance to ground of the distributed power supply.

2. The power supply system according to claim 1 , further comprising a control unit that executes control to receive power from the external power supply device after the wiring within the facility is grounded by the grounding mechanism.

3. 2. The power supply system according to claim 1, wherein the second converter is a converter that converts DC power output from the distributed power source into AC power.

4. the distributed power source is a solar cell, 2. The power supply system according to claim 1, wherein the external power supply device has an external power source that is an external solar cell.

5. The power supply system according to claim 1 , wherein the external power supply device is a non-isolated external power supply device.

Images