Insulation resistance test system, manufacturing method, and insulation resistance test method

Abstract

To allow the insulation resistance test of a photovoltaic power generation system having an over-voltage suppression element.SOLUTION: An insulation resistance test system is applied to the insulation resistance test of a photovoltaic power generation system provided on the output side of a solar battery device from a demarcation point having an over-voltage suppression element arranged between the output of the solar battery device and a ground electrode and provided in the middle of a path connecting the output of the solar battery device and the input of a power converter in the latter part of the solar battery device. The insulation resistance test system includes a test device generating a direct current test voltage having a size predetermined for an insulation resistance test between first and second terminals; the positive and negative electrodes of the path leading to the output of the solar battery device are separated from the input of the power converter and the ground electrode at the demarcation point; and the test device can apply the positive direct current voltage having a predetermined size to the second terminal in the state of connecting the second terminal to the ground electrode and connecting the first terminal to the negative electrode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an insulation resistance testing system, a manufacturing method, and an insulation resistance testing method. [Background technology]

[0002] In some photovoltaic power generation systems, the DC power generated by the solar cell device is sent via a power cable to a power converter (power conditioner), which then converts it into AC power. The insulation resistance test system is used to test the insulation resistance of such solar cell devices and the power cable connected to the output side of the solar cell device. Solar cell devices installed outdoors generate electricity when exposed to external light. There are techniques (such as JIS C 1302) for testing the insulation resistance of solar cell devices in such situations.

[0003] Some photovoltaic power generation systems are provided with an overvoltage suppression element or the like on the output side of the solar cell device to protect the solar cell device or the like from overvoltages such as lightning surges. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2018-512561 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if an overvoltage suppression element is installed in the path from the output of the solar cell device to the power conversion device to protect the solar cell device from overvoltage, the result of the insulation resistance test may show a result similar to that when the insulation resistance is reduced. To avoid this, work to disconnect the overvoltage suppression element from the path during the insulation resistance test is sometimes carried out, but this work, which follows procedures to avoid live wiring, is extremely cumbersome.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide an insulation resistance testing system, a manufacturing method, and an insulation resistance testing method that enable insulation resistance testing of a solar power generation system in which an overvoltage suppression element is provided on the output side of a solar cell device to be performed in a simple procedure. [Means for solving the problem]

[0007] (1) In order to solve the above problem, one aspect of the present invention is an insulation resistance test system used for an insulation resistance test of a solar power generation system in which an overvoltage suppression element arranged between the output of a solar cell device and a grounding electrode is arranged on the output side of the solar cell device rather than a demarcation point located midway along a path connecting the output of the solar cell device and the input of a power conversion device downstream of the solar cell device, the insulation resistance test system including a test device that generates a DC test voltage of a predetermined magnitude for the insulation resistance test between a first terminal and a second terminal, and in a state in which the positive and negative electrodes of the path connected to the output of the solar cell device are separated from the input and grounding electrode of the power conversion device, respectively, at the demarcation point, the second terminal is connected to the grounding electrode, and the first terminal is connected to the negative electrode, the test device is capable of applying the positive DC voltage of a predetermined magnitude to the second terminal. (2) In the insulation resistance test system, the test device generates the DC voltage such that the voltage of the first terminal is higher than the voltage of the second terminal by the DC test voltage. (3) In the above insulation resistance test system, the test device includes a switch capable of selecting a desired operation mode from a plurality of operation modes, including a first operation mode in which the voltage of the first terminal generates the DC voltage higher than the voltage of the second terminal, and a second operation mode in which the voltage of the first terminal generates a DC voltage lower than the voltage of the second terminal, and a switching circuit that switches between the voltage of the first terminal and the voltage of the second terminal. (4) One aspect of the present invention is a method for manufacturing an insulation resistance test system including a test device that generates, between a first terminal and a second terminal, a DC test voltage of a predetermined magnitude applicable to an insulation resistance test of a solar power generation system in which an overvoltage suppression element arranged between the output of a solar cell device and a grounding electrode is arranged between the output of the solar cell device and a demarcation point located midway along a path connecting the output of the solar cell device and the input of a power conversion device downstream of the solar cell device, and before the test device applies the positive DC voltage of the predetermined magnitude to the second terminal, the positive and negative electrodes of the path connected to the output of the solar cell device are disconnected from the input and grounding electrode of the power conversion device, respectively, at the demarcation point, and the second terminal is connected to the grounding electrode and the first terminal is connected to the negative electrode. (5) One aspect of the present invention is an insulation resistance test method for a solar power generation system in which an overvoltage suppression element disposed between the output of a solar cell device and a grounding electrode is disposed between the output of the solar cell device and a demarcation point provided midway along a path connecting the output of the solar cell device and the input of a power conversion device downstream of the solar cell device, the insulation resistance test method including a test step in which a test device generates a DC test voltage of a predetermined magnitude for an insulation resistance test between a first terminal and a second terminal, and in which the positive and negative electrodes of the path connected to the output of the solar cell device are disconnected from the input and grounding electrode of the power conversion device, respectively, at the demarcation point, the second terminal is connected to the grounding electrode, and the first terminal is connected to the negative electrode, and the predetermined positive DC voltage is applied to the second terminal. [Effects of the Invention]

[0008] According to each aspect of the present invention, it is possible to perform an insulation resistance test on a photovoltaic power generation system provided with an overvoltage suppression element. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing an application example of an insulation resistance test apparatus 100 according to a first embodiment. [Figure 2] 1 is a schematic diagram illustrating the configuration of an insulation resistance test device 100 according to an embodiment. [Figure 3] 10 is a flowchart showing the procedure of an N-phase side test according to the embodiment. [Figure 4] FIG. 10 is a diagram for explaining a voltage distribution in a solar string according to the embodiment. [Figure 5] FIG. 10 is a diagram for explaining a voltage distribution in a solar string according to the embodiment. [Figure 6] 1 is a schematic configuration diagram of an operation panel surface of an insulation resistance test apparatus 100 according to an embodiment. [Figure 7] FIG. 10 is a schematic diagram illustrating the configuration of an insulation resistance test apparatus 100A of an operation mode change type according to a second embodiment. [Figure 8] FIG. 10 is a diagram for explaining the use of an insulation resistance test apparatus 100B according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The solar cell device in the embodiment represents a solar cell panel, a solar cell string, a solar cell array, etc. The insulation resistance test device in the embodiment is an example of an insulation resistance meter.

[0011] (First embodiment) 1 is a diagram showing an application example of an insulation resistance test apparatus 100 according to the first embodiment. This insulation resistance test apparatus 100 is an apparatus for performing an insulation resistance test on a solar cell string in which a plurality of solar cell panels (photovoltaic panels) are connected in series, for example.

[0012] As shown in Fig. 1, the solar cell device 2 is configured by connecting multiple PV panels PV1, PV2, PV3, ..., PVn in series. n is an integer indicating the number of PV panels in series (number of panels) in the solar cell device 2. When the PV panels PV1, PV2, PV3, ..., PVn are not to be distinguished from one another, they are referred to as PV panel N. Each PV panel N is configured to include a predetermined number of solar cells.

[0013] The solar cell device 2 used during normal times is connected to a power conditioner (hereinafter simply referred to as "PCS") 20 by a power cable 10 (FIG. 2), which is a power supply line for generated power, via a junction box 30 and a collector panel 40. The power cable 10 includes at least a positive power supply line 11 and a negative power supply line 12. The positive power supply line 11 is connected to the positive electrode side of the solar cell device 2 and is called the P phase. The negative power supply line 12 is connected to the negative electrode side of the solar cell device 2 and is called the N phase. The positive power supply line 11 and the negative power supply line 12 are each insulated from, for example, earth E.

[0014] For example, the junction box 30 is provided with switches 31 and 32, load switches 33 and 34, and SPDs 5 and 6. The power collection board 40 is provided with switches 41 and 42. The load switch 33 and the load switch 34 each include, for example, three sets of double-pole single-throw (DPST) switches. The load switch 33 includes switches 33A, 33B, and 33C. The load switch 34 includes switches 34A, 34B, and 34C. The set of switches 33A and 34A, the set of switches 33B and 34B, and the set of switches 33C and 34C each form a double-pole single-throw (DPST) switch. The switch 41 and the switch 42 include, for example, three sets of double-pole single-throw (DPST) switches. The switch 41 includes switches 41A, 41B, and 41C. The switch 42 includes switches 42A, 42B, and 42C. The set of switches 41A and 42A, the set of switches 41B and 42B, and the set of switches 41C and 42C each form a double-pole single-throw (DPST) switch. The above-mentioned double-pole single-throw (DPST) may be a double-pole double-throw (DPDT) switch.

[0015] The power feeder 11 includes a power feeder 11A, a power feeder 11B, and a power feeder 11C, which are separated by the junction box 30 and the collector board 40. The power feeder 12 includes a power feeder 12A, a power feeder 12B, and a power feeder 12C, which are separated by the junction box 30 and the collector board 40.

[0016] That is, a P-phase terminal PVP, which is an output terminal on the positive (+) side of the solar cell device 2, is connected to an input terminal on the positive side of the PCS 20 via a power feeder 11A, a load switch 33, a positive electrode frame in the junction box 30, a switch 31, a power feeder 11B, a switch 41, a positive electrode frame in the current collector 40, a switch 41, and a power feeder 11C. An N-phase terminal PVN, which is an output terminal on the negative (-) side of the solar cell device 2, is connected to an input terminal on the negative side of the PCS 20 via a power feeder 12A, a load switch 34, a negative electrode frame in the junction box 30, a switch 32, a power feeder 12B, a switch 42, a negative electrode frame in the current collector 40, and a power feeder 12C.

[0017] The PCS 20 converts the DC power generated by the solar cell device 2 into AC power using a power conversion circuit (not shown), and outputs the converted AC power to a power system such as a commercial system.

[0018] The power feeder lines 11 and 12 that supply power from the solar cell device 2 to the PCS 20 may be relayed and wired using a junction box 30, a collector panel 40, or the like, as shown in Fig. 1. In the example shown in Fig. 1, the switches 31 and 32 are housed in the junction box 30. The switches 41 and 42 are housed in the collector panel 40.

[0019] For example, the negative pole side power supply line 12C connected to the (-) side input terminal of the PCS 20 is grounded to earth E inside the PCS 20. When the switch 32 is in the ON state (connected state), the N phase terminal PVN of the solar cell device 2 is grounded to earth E inside the PCS 20 via the power supply line 12A, the switch 32, the power supply line 12B, the switch 42, and the power supply line 12C.

[0020] SPD5 and SPD6 are overvoltage suppression elements and may be, for example, lightning arresters (SPDs). Details regarding SPD5 and SPD6 will be described later.

[0021] (Configuration for measuring insulation resistance) When measuring the insulation resistance of the solar cell device 2, a measurer using the insulation resistance test apparatus 100 turns off the switches 41 and 42, for example. This cuts off the connection between the solar cell device 2 and the PCS 20. If no ground fault occurs, the solar cell device 2 is in a floating state.

[0022] Fig. 2 is a schematic diagram of the insulation resistance test apparatus 100 of the embodiment. Fig. 6 is a schematic diagram of the operation panel surface of the insulation resistance test apparatus 100 of the embodiment. After the solar cell device 2 is brought into a floating state as described above, the insulation resistance test device 100 detects the insulation resistance of the solar cell device 2.

[0023] As described above, even if the solar cell device 2 is in a floating state, the following circuits exist within the junction box 30. One end of the SPD 5 is connected at a connection point BP to the positive electrode side (P phase) of the solar cell device 2. The other end of the SPD 5 is grounded via a grounding wire 13. By providing the SPD 5, it is possible to prevent an overvoltage exceeding a predetermined voltage from being applied to the positive electrode side of the solar cell device 2 and the positive-side power supply line 11.

[0024] One end of the SPD 6 is connected at a connection point BN to the negative electrode side (N phase) of the solar cell device 2. The other end of the SPD 6 is grounded via a grounding wire 13. By providing the SPD 6, it is possible to prevent an overvoltage exceeding a predetermined voltage from being applied to the negative electrode side of the solar cell device 2 and the negative-side power supply line 12.

[0025] A rectifying element 7 may be provided on the positive electrode side (P phase) of the solar cell device 2. The rectifying element 7 is, for example, a diode. The rectifying element 7 passes the current output by the solar cell device 2 in the forward direction and blocks the current when the solar cell device 2 is reverse-biased.

[0026] The rectifying element 7 shown in FIG. 2 is provided on the positive-side power supply line 11 closer to the solar cell device 2 than the connection point BP of the SPD 5, in other words, on the opposite side of the power converter with respect to the connection point BP.

[0027] The insulation resistance test apparatus 100 includes, for example, a first terminal TB1 and a second terminal TB2. A test lead TLA is connected to the first terminal TB1, which is connected to an N-phase terminal TBN of the current collection box 40. The first terminal TB1 is connected via the test lead TLA to the negative feeder 12 of the power cable 10 connected to the solar cell device 2 under test. A test lead TLB is connected to the second terminal TB2, which is connected to the ground terminal TBE of the current collection box 40. The second terminal TB2 is grounded via the test lead TLB and the ground wire 13.

[0028] The following describes a model of the configuration of the insulation resistance test apparatus 100. The insulation resistance test apparatus 100 includes, for example, a DC voltage source 101, a switch 102, resistors 103 and 104, a switch 108 (FIGS. 6 and 7), a voltage detection unit 110, a current detection unit 120, and a control unit 130.

[0029] The switch 108 is a switch that switches the operation mode and test voltage range of the insulation resistance test apparatus 100. The switch 108 is not shown in FIG.

[0030] DC voltage source 101 outputs a desired DC voltage during an insulation resistance test. The DC voltage output by DC voltage source 101 is set, for example, by control unit 130, which will be described later. The adjustment of this voltage will be described later.

[0031] Switch 102 is, for example, a double-pole single-throw (DPST) momentary switch. The contacts of switch 102 are closed while its knob (FIG. 6) is pressed, and open when the knob is released. In addition to the single pole shown in FIG. 2, there is also an auxiliary contact (not shown) that is linked to this and is connected to control unit 130, which will be described later.

[0032] The negative electrode of DC voltage source 101 is connected to second terminal TB2 via switch 102 and resistors 103 and 104. When switch 102 is closed during an insulation test, a voltage for the insulation test is output. Resistors 103 and 104 are connected in series with DC voltage source 101. Resistor 103 has a specified impedance and limits the current that flows during an insulation resistance test. Resistor 103 can be replaced with an element having an impedance. If the impedance of resistor 104 is set sufficiently smaller than the impedance of resistor 103, the current that flows during an insulation resistance test will be mainly affected by the impedance of resistor 103.

[0033] The positive electrode side of DC voltage source 101 is connected to first terminal TB1. DC voltage source 101 may be configured to include, for example, an AC voltage source, an isolation transformer, a rectifier circuit, a capacitor, and the like, all of which are not shown. In this case, the capacitor is charged with a DC voltage based on the peak value of the result of rectification by the rectifier circuit after voltage conversion of the output voltage of the AC voltage source by the isolation transformer. The output voltage of DC voltage source 101 may be configured to be adjustable by adjusting the settings of each of the above components. Known methods may be used for the configuration of DC voltage source 101 and for adjusting the output voltage. In the following description of this embodiment, DC voltage source 101 will be modeled as outputting a DC current of a predetermined voltage.

[0034] The voltage detection unit 110 measures the potential difference between the first terminal TB1 and the second terminal TB2. This potential difference is called voltage V1. To specify voltage V1 more precisely, the voltage detection unit 110 measures the potential difference between the first terminal TB1 and the voltage dividing point VDP on the negative side of the DC voltage source 101 while the circuit is closed by the switch 102. Note that the voltage drop due to the resistor 104 is assumed to be negligible.

[0035] The current detection unit 120 detects the current flowing through the resistor 104 during the insulation resistance test. For example, the current detection unit 120 is provided between the voltage dividing point VDP on the negative side of the DC voltage source 101 and the second terminal TB2. The resistor 104 may be a part of the current detection unit 120.

[0036] The control unit 130 includes a microcomputer (microcontroller) 131 and an input / output unit 132. The microcomputer 131 includes, for example, a CPU (central processing unit), a storage device such as a main storage device or an auxiliary storage device, a communication device, and the like, and performs predetermined operations by executing a predetermined program stored in, for example, the auxiliary storage device. The input / output unit 132 includes a display unit (FIG. 6) such as a liquid crystal display device, and displays, under the control of the microcomputer 131, a display for selecting a test voltage, a display of the selected test voltage, a display of the insulation resistance test result, and the like. The input / output unit 132 detects user operations on the switches 102, 108 (FIG. 6), and notifies the microcomputer 131 of the detection results. For example, the input / output unit 132 detects the designation of the test voltage selected by the user through the operation of the switch 108.

[0037] An example of testing insulation resistance using the negative feeder 12 of a power cable will be described.

[0038] Even if the PCS 20 (Fig. 1) is disconnected from the output of the outdoor solar cell device 2, the solar cell device 2 generates power by itself by receiving light and outputs a DC voltage. In this case, when a test voltage is applied to the first phase of the power cable 10 to test the insulation resistance, the voltage of the second phase will be different from the test voltage.

[0039] As shown in Figure 2, SPD5 and SPD6 are provided on the output side of the solar cell device 2. The clamping voltage ratings of SPD5 and SPD6 may be the same. When the voltage to ground of any phase of the power cable 10 exceeds the clamping voltages of SPD5 and SPD6, SPD5 and SPD6 become conductive and suppress the overvoltage. From the perspective of the insulation resistance test device 100, it is difficult to distinguish this situation from a state in which the power cable 10 has a ground fault or a pseudo-ground fault, making it impossible to continue the test accurately.

[0040] Therefore, when performing an insulation resistance test, the insulation resistance test apparatus 100 limits the voltage to ground of the power cable 10 to a voltage lower than the limit voltage of SPD5 and SPD6, thereby enabling the test to be performed without causing SPD5 and SPD6 to respond.

[0041] The N-phase side test of the embodiment will be described with reference to Fig. 3. Fig. 3 is a flowchart showing the procedure of the N-phase side test of the embodiment. First, the setting of the insulation resistance test device 100 for testing the N-phase side will be described.

[0042] The user operates switch 108 to set the desired operating mode, and leaves the knob of switch 102 in an unoperated state, allowing DC voltage source 101 to charge to a usable state. In this state, the user connects the second terminal TB2 to the ground electrode terminal TBE and connects the N phase of the power cable 10 to the first terminal TB1, thereby making it possible to output a desired voltage between the first terminal TB1 and the second terminal TB2, completing preparations for the insulation resistance test (step Sb0).

[0043] The user operates the knob of the switch 102 to keep the contact closed until the measurement is completed. The insulation resistance test apparatus 100 detects that the switch 102 has been closed and starts the measurement (step Sb1).

[0044] Insulation resistance test apparatus 100 outputs a predetermined voltage VE from DC voltage source 101 and applies a positive voltage VE to the N phase (step Sb2). As a result, the N phase circuit voltage V2 becomes the voltage VE of DC voltage source 101. The P phase circuit voltage becomes the sum of the voltage VE of DC voltage source 101 and the generated voltage Vp output by power generation from the solar string.

[0045] The insulation resistance test apparatus 100 simultaneously measures the insulation resistance Rg between the P phase and the N phase and the ground (step Sb5). For example, the current detection unit 120 may measure the current flowing through the resistor 104 during the simultaneous measurement and calculate the insulation resistance Rg from the current value I.

[0046] The control unit 130 determines whether the insulation resistance Rg is equal to or less than a predetermined threshold value RTH (step Sb6). The magnitude of the threshold value RTH may be set to, for example, 0.4 MΩ.

[0047] If the insulation resistance Rg is equal to or less than the predetermined threshold value RTH, the control unit 130 determines that the insulation resistance between the N phase and the P phase has decreased, and causes the input / output unit 132 to display the result (step Sb7).

[0048] If the insulation resistance Rg exceeds the predetermined threshold value RTH, the control unit 130 determines that the insulation resistance of neither the N phase nor the P phase has decreased, and displays the result on the input / output unit 132 (step Sb8).

[0049] The user checks the result of the judgment and releases the knob of the switch 102 that he has been holding, opening the contacts. The insulation resistance test apparatus 100 detects that the switch 102 has been opened and ends the measurement (step Sb9). When the insulation resistance test apparatus 100 detects an overcurrent or overvoltage, it may limit the output current by adjusting the impedance of the resistor 103, regardless of the state of the switch 102, in order to protect the circuit.

[0050] By performing an insulation resistance test following the above series of steps, the N-phase circuit voltage can be maintained at the test voltage and the insulation resistance can be measured under that condition. This makes it possible to measure the insulation resistance at the specified test voltage with both SPDs 5 and 6 attached to the circuit.

[0051] The voltage distribution in the solar cell device 2 will be described with reference to FIGS. 4 and 5 are diagrams for explaining the voltage distribution in the solar cell device 2 of the embodiment. 4, one example of this solar cell device 2 (solar string) includes 20 solar panels, PV panels PV1 to PV20. The PV panels N are connected in series by connection cords L1 to L21, respectively.

[0052] Graph Gv1a in Fig. 5 shows the potential of each part when the solar cell device 2 (solar string) shown in Fig. 4 is connected to the PCS 20. Graph Gv1a is the result of linear approximation based on the potential of the N phase, which is set to the potential of earth E (0V). Graph Gv1a shows the potential of each part when it is assumed, for example, that each PV panel N is in a power generating state outputting a DC voltage of +40V. In this case, the potential of the P phase is +800V.

[0053] Graph Gv2a shows the potential of each part when the photovoltaic device 2 (solar string) is disconnected from the PCS 20 and floated by turning off the switches 41 and 42, and then a test voltage VE (for example, DC voltage: +280V) is applied to the N phase. Note that, like graph Gv1a, graph Gv2a is the result of linear approximation based on the N phase potential (+280V in this case). It can be seen that the potential of graph Gv2a is higher across the entire range by the test voltage (DC voltage: +280V) compared to graph Gv1a. According to graph Gv2a, the potential of the P phase is 1080V. In this case, the P-phase voltage must be lower than the clamping voltage SPDL of the SPD. In this state, if a current of a specified value or more does not flow through resistor 104, the voltage drop across resistor 104 will be smaller than the threshold value, ensuring a desired level of insulation resistance.

[0054] According to the above embodiment, the solar power generation system 1 includes SPDs 5 and 6 (overvoltage suppression elements) disposed between the output of the solar cell device 2 and Earth E (ground electrode) on the output side of a demarcation point provided midway along a path connecting the output of the solar cell device 2 and the input of the PCS 20 (power conversion device) downstream of the solar cell device 2. The insulation resistance test system 3 is applicable to insulation resistance testing of the solar power generation system 1. The insulation resistance test device 100 generates a DC test voltage of a predetermined magnitude for insulation resistance testing between the first terminal TB1 and the second terminal TB2. When the positive and negative terminals of the path connected to the output of the solar cell device 2 are disconnected from the input of the PCS 20 (power conversion device) and Earth E (ground electrode) at the demarcation point, the second terminal TB2 is connected to the ground electrode, and the first terminal TB1 is connected to the negative terminal, the insulation resistance test device 100 is configured to apply a positive DC voltage of a predetermined magnitude to the second terminal TB2. This enables insulation resistance testing of the solar power generation system 1 provided with an overvoltage suppression element.

[0055] The insulation resistance test system 3 is formed on-site when measuring insulation resistance. For example, in one example of a method for manufacturing the insulation resistance test system 3, before the insulation resistance test apparatus 100 applies a positive DC voltage of a predetermined magnitude to the second terminal TB2, the positive and negative electrodes of the path leading to the output of the solar cell device 2 are separated from the input of the PCS 20 (power conversion device) and the earth E (ground electrode) at demarcation points, and the second terminal TB2 is connected to the earth E and the first terminal TB1 is connected to the negative electrode, thereby enabling the insulation resistance test of the solar power generation system 1 by the insulation resistance test apparatus 100.

[0056] (Second embodiment) 7 is a schematic diagram showing the configuration of an insulation resistance test apparatus 100A of an operation mode changeable type according to a second embodiment of the present invention. FIG. 7 is a schematic diagram showing the configuration of an insulation resistance test apparatus 100A of an operation mode changeable type according to an embodiment of the present invention.

[0057] Insulation resistance test apparatus 100A is configured to include AC voltage source 105, isolation transformer 106, and rectifier circuit 107 for charging DC voltage source 101A. This DC voltage source 101A includes a capacitor, and is charged with a DC voltage based on the peak value of the result of rectification by rectifier circuit 107 after voltage conversion of the output voltage of AC voltage source 105 by isolation transformer 106. The output voltage of DC voltage source 101A may be configured to be adjustable by adjusting the settings of each of the above components. Known methods may be used for the configuration of DC voltage source 101A and for adjusting the output voltage.

[0058] In the following description, DC voltage source 101A will be modeled as outputting a DC current of a predetermined voltage. In this embodiment, a more specific example for switching the polarity of the output voltage will be described.

[0059] The rectifier circuit 107 includes a switch 107N and a switch 107P. The switch 107N and the switch 107P each include a semiconductor switching element. The rectifier circuit 107 is an example of a configuration using a power semiconductor switching element. In this embodiment, a case where a MOSFET is used as the semiconductor switching element is illustrated. The symbol for the MOSFET shown in FIG. 6 also shows a diode connected in anti-parallel. This diode may be a body diode of the MOSFET, or may be a diode provided separately from the MOSFET. For ease of explanation, the diodes will be denoted by reference symbols.

[0060] For example, the switch 107N includes a MOSFET 107NS and a diode 107ND. The switch 107P includes a MOSFET 107PS and a diode 107PD. For example, the MOSFETs 107NS and 107PS are N-channel types.

[0061] The source of the MOSFET 107PS and the anode of the diode 107PD are connected to the secondary winding of the transformer 106. The drain of the MOSFET 107PS and the cathode of the diode 107PD are connected to the drain of the MOSFET 107NS and the cathode of the diode 107ND. The source of the MOSFET 107NS and the anode of the diode 107ND are connected to the first terminal TB1.

[0062] The switch 107N can be set to a first state in which it allows current to flow in both directions, and a second state in which it allows current to flow in the forward direction of the diode 107ND. The switch 107P can be set to a third state in which it allows current to flow in both directions, and a fourth state in which it allows current to flow in the forward direction of the diode 107PD. For example, if either the switch 107N or the switch 107P (third interrupter) is turned on, a rectifier circuit is formed, and the direction of current can be switched depending on which switch is turned on. More specifically, by setting switch 107N to the first state and switch 107P to the fourth state, a current can flow in the forward direction of diode 107PD. Alternatively, by setting switch 107N to the second state and switch 107P to the third state, a current can flow in the forward direction of diode 107ND. This allows the direction of the current flowing through rectifier circuit 107 to be switched by control, and the polarity of the voltage output from DC voltage source 101A to be switched.

[0063] According to the above embodiment, in addition to achieving the same effects as the first embodiment, by realizing a configuration for switching the polarity of the voltage generated by the insulation resistance test apparatus 100A, it becomes possible to apply the insulation resistance test apparatus 100A to a general method, for example, a insulation resistance test conforming to JIS C 1302, in addition to the insulation resistance test according to the method of the first embodiment.

[0064] More specifically, for example, the insulation resistance test apparatus 100A includes a switch 108 and a switching circuit 107. The insulation resistance test apparatus 100A is configured to be able to select a desired operation mode from a plurality of operation modes using the switch 108, including a first operation mode in which the voltage at the first terminal TB1 generates a DC voltage higher than the voltage at the second terminal TB2, and a second operation mode in which the voltage at the first terminal TB1 generates a DC voltage lower than the voltage at the second terminal TB2. The switching circuit 107 can reverse the polarity by switching between the voltage at the first terminal TB1 and the voltage at the second terminal TB2 according to the operation mode selected by the switch 108.

[0065] (Third embodiment) A simple setting of an operation mode will be described as a third embodiment with reference to Fig. 8. Fig. 8 is a diagram for explaining the use of an insulation resistance test apparatus 100B according to the third embodiment. In the second embodiment described above, an operation mode changeable insulation resistance test apparatus 100A was described, but in this embodiment, an example will be described in which measurements similar to those in the first embodiment are possible by using an insulation resistance test apparatus 100B that outputs a negative voltage to the first terminal TB1 and a positive voltage to the second terminal TB2.

[0066] The insulation resistance test apparatus 100B outputs a negative voltage to the first terminal TB1 and a positive voltage to the second terminal TB2. As shown in Fig. 8(a), an example of the insulation resistance test apparatus 100B may be applicable to a dielectric strength test in accordance with JIS C 1302. In the case of JIS C 1302, a potential (e.g., -1000 V) more negative than the potential of the earth E is applied to the positive electrode terminal PVP of the solar cell device 2 to measure the insulation resistance.

[0067] Alternatively, as shown in FIG. 8(b), the connection destinations of the first terminal TB1 and the second terminal TB2 may be replaced with the connection destinations of the insulation resistance test apparatus 100 of the first embodiment, and the connection cord connected to earth E may be replaced with an inverse connection cord, with the other connection cord being connected to the negative terminal PVN of the solar cell device 2.

[0068] According to this, when the insulation resistance test apparatus 100B is used, the same effects as those of the first embodiment are achieved.

[0069] According to the above embodiment, in the insulation resistance test apparatus 100, the first terminal BT1 is connected to the negative power supply line 12 of the power cable 10 connected to the solar cell device 2 under test. The second terminal BT2 is grounded. The control unit 130 tests the insulation resistance of the device under test based on the voltage (V1, V2, etc.) detected by the voltage detection unit 110, thereby enabling an insulation resistance test to be performed on the solar power generation system 1 provided with SPDs 5 and 6.

[0070] In addition, SPD5 and SPD6 with predetermined limiting voltages are provided between the output terminal of the solar cell device 2 related to the insulation resistance test device 100 and ground, and the limiting voltage specified for the power cable 10 may be specified based on the discharge start voltages of SPD5 and SPD6.

[0071] Furthermore, by outputting a DC voltage specified based on the power generation voltage Vp output by solar cell device 2, DC voltage source 101 can keep the voltage on the positive electrode side of solar cell device 2 lower than the discharge start voltage of SPD 5, making it possible to perform an insulation resistance test without removing SPD 5 from the circuit. Note that the power generation voltage Vp output by solar cell device 3 is not limited to the actually measured voltage, but may be a voltage determined in advance based on the rated output voltage, maximum output voltage, etc. of solar cell device 3.

[0072] The power generation voltage Vp output by the solar cell device 3 is not limited to an actually measured voltage, but may be a voltage determined in advance based on the rated output voltage, maximum output voltage, etc. of the solar cell device 3. For example, the control unit 130 of the insulation resistance test apparatus 100 sets the DC voltage of the DC voltage source 101. The control unit 130 determines the output voltage range of the DC voltage source based on the power generation voltage Vp output by the solar cell device 3 and a limiting voltage specified for the power cable 10 so that the potential of the power cable 10 to ground does not exceed the limiting voltage specified for the power cable 10. The control unit 130 may set the output voltage of the DC voltage source 101 within the specified output voltage range. The limiting voltage specified for the power cable 10 may be determined based on the limiting voltages of the SPDs 5 and 6, the rated insulation voltage of the power cable 10, etc.

[0073] The measurement of the insulation resistance of the positive electrode side power supply wire connected to the positive electrode of the solar cell device 2 can also be performed by measuring the insulation resistance of the negative electrode side power supply wire connected to the negative electrode of the solar cell device 2.

[0074] In addition, the control unit 130 of the insulation resistance test apparatus 100 may regulate the output voltage of the DC voltage source 101 so that the sum of the DC voltage VE output by the DC voltage source 101 during the test and the rated voltage (maximum output voltage) of the solar cell device 2 does not exceed the limit voltage regulated for the power cable 10 connected to the solar cell device 2 being measured.

[0075] Alternatively, a program for implementing the control unit 130 of the insulation resistance test apparatus 100 may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed to cause the insulation resistance test apparatus 100 to perform a predetermined processing operation. The term "computer system" as used herein includes hardware such as an OS and peripheral devices. The term "computer system" also includes a WWW system equipped with a website provision environment (or display environment). The term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computer systems. The term "computer-readable recording medium" also includes devices that retain a program for a certain period of time, such as volatile memory (RAM) within a computer system that acts as a server or client when the program is transmitted via a network such as the Internet or a communication line such as a telephone line.

[0076] The program may also be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by transmission waves in the transmission medium. Here, the "transmission medium" that transmits the program refers to a medium that has the function of transmitting information, such as a network or a communication line. The program may also be a program that realizes part of the above-mentioned functions. Furthermore, the program may be a so-called differential file (differential program) that can realize the above-mentioned functions in combination with a program already recorded in the computer system.

[0077] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as the inventions described in the claims and their equivalents. [Explanation of symbols]

[0078] 1...Photovoltaic power generation system, 2...Photovoltaic device, 3...Insulation resistance test system, 5, 6...SPD, 10...Power cable, 11...Positive power supply line, 12...Negative power supply line, 100...Insulation resistance test device, 101...DC voltage source, 102, 108...Switch, 103, 104...Resistor, 110...Voltage detection unit, 120...Current detection unit, 130...Control unit, E...Earth (ground electrode)

Claims

1. An insulation resistance test system used for testing the insulation resistance of a photovoltaic power generation system in which the output of a solar cell device and the input of a power conversion device downstream of the solar cell device are connected by a power supply line, and an overvoltage suppression element disposed between the output of the solar cell device and a ground electrode is disposed closer to the output side of the solar cell device than to the input of the power conversion device, A test device that generates a DC test voltage of a predetermined magnitude between a first terminal and a second terminal for an insulation resistance test. Equipped with In a state where the positive and negative terminals of the power supply line connected to the output of the solar cell device are disconnected from the input and ground terminal of the power conversion device, respectively, the second terminal is connected to the ground terminal, and the first terminal is connected to the negative terminal, When the solar cell device is generating power, The test device comprises: A positive DC test voltage can be generated and applied to the first terminal so that the voltage applied to the positive electrode of the power supply line is lower than the limit voltage of the overvoltage suppression element. Insulation resistance test system.

2. The test device generates a DC test voltage such that the voltage of the first terminal is higher than the voltage of the second terminal by the DC test voltage.

2. The insulation resistance test system according to claim 1.

3. The test device comprises: a switch capable of selecting a desired operation mode from a plurality of operation modes, including a first operation mode in which the DC test voltage is generated such that the voltage of the first terminal is higher than the voltage of the second terminal, and a second operation mode in which the DC test voltage is generated such that the voltage of the first terminal is lower than the voltage of the second terminal; a switching circuit that switches between a voltage at the first terminal and a voltage at the second terminal; 3. The insulation resistance test system according to claim 1, further comprising:

4. A method for manufacturing an insulation resistance test system used in an insulation resistance test of a solar power generation system, in which the output of a solar cell device and the input of a power conversion device downstream of the solar cell device are connected by a power supply line, and an overvoltage suppression element disposed between the output of the solar cell device and a grounding electrode is disposed closer to the output side of the solar cell device than to the input of the power conversion device, before applying a DC test voltage having a predetermined magnitude for an insulation resistance test between the first terminal and the second terminal, the positive and negative terminals of the power supply line connected to the output of the solar cell device are disconnected from the input and ground terminal of the power conversion device, respectively, the second terminal is connected to the ground terminal, and the first terminal is connected to the negative terminal; When the solar cell device is generating power, A positive DC test voltage can be generated and applied to the first terminal so that the voltage applied to the positive electrode of the power supply line is lower than the limit voltage of the overvoltage suppression element. Manufacturing method of insulation resistance test system.

5. A method for testing the insulation resistance of a solar power generation system in which the output of a solar cell device and the input of a power conversion device downstream of the solar cell device are connected by a power supply line, and an overvoltage suppression element disposed between the output of the solar cell device and a ground electrode is disposed closer to the output side of the solar cell device than to the input of the power conversion device, a testing step in which the test apparatus generates a DC test voltage having a predetermined magnitude for an insulation resistance test between the first terminal and the second terminal; Including, In a state where the positive and negative terminals of the power supply line connected to the output of the solar cell device are disconnected from the input and ground terminal of the power conversion device, respectively, the second terminal is connected to the ground terminal, and the first terminal is connected to the negative terminal, When the solar cell device is generating power, The test device comprises: generating a positive DC test voltage such that the voltage applied to the positive electrode of the power supply line is lower than the limit voltage of the overvoltage suppression element, and applying the positive DC test voltage to the first terminal; Insulation resistance test method.

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