JP2005312287A - Power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply that is cost effective and highly reliable in detecting a ground fault. <P>SOLUTION: One input terminal of a ground fault detecting circuit 44 is connected to the positive terminal of a solar cell module 11 via a resistor 41, to the positive terminal of a solar cell module 12 via a resistor 42, and to the positive terminal of a solar cell module 13 via a resistor 43. The other input terminal of the ground fault detecting circuit 44 is commonly connected to each negative terminal of the solar cell modules 11-13. If a ground fault occurs in a charged portion by the solar cell modules 11-13, it is detected by the ground fault detecting circuit 44. Thus, cost can be cut in comparison with the prior art in which a plurality of the ground fault detecting circuits are provided corresponding to each of a plurality of DC power supplies. Since a circuit structure is simplified, the reliability of the ground fault detection also improves. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power supply device, and more particularly to a power supply device that converts DC power generated by a plurality of DC power supplies into AC power and outputs the AC power.

  Solar cells and fuel cells generate direct-current power by converting natural energy into electrical energy. With the recent increase in awareness of global environmental problems, power generation systems using solar cells and fuel cells are attracting attention as clean power generation systems that do not emit carbon dioxide, which contributes to global warming.

  FIG. 15 is a circuit block diagram showing a schematic configuration of a photovoltaic power generation system using a conventional power supply device. In FIG. 15, this power supply device is configured by a grid interconnection inverter device 202, converts the DC power generated by the DC power supply unit 201 into AC power, and supplies the AC power to the commercial power system 203. In a normal state where no ground fault has occurred, the switch circuits SW41 to SW46, SW51, and SW52 are turned on.

  DC power supply unit 201 includes solar cell modules 211 to 213. The grid interconnection inverter 202 includes switching units 221 and 224, a DC / DC converter unit 222, an inverter circuit 223, ground fault detection circuits 225 to 227, a control unit 228, and a display unit 229. Switching unit 221 includes switch circuits SW41 to SW46. The DC / DC converter unit 222 includes DC / DC converters 231 to 233. Inverter circuit 223 includes transistors TR11 to TR14. Switching unit 224 includes switch circuits SW51 and SW52.

  Each of the solar cell modules 211 to 213 converts solar energy into electric energy and supplies DC power to the grid interconnection inverter device 202. Each of these solar cell modules 211 to 213 is formed by connecting a plurality of solar cells in series. The DC / DC converters 231 to 233 receive the DC power generated by the solar cell modules 211 to 213 via the switching unit 221, respectively. These DC / DC converters 231 to 233 convert the DC voltages obtained from the solar cell modules 211 to 213 into predetermined voltages, respectively. The output parts of the DC / DC converters 231 to 233 are coupled together and connected to the inverter circuit 223.

  The inverter circuit 223 converts the DC power from the DC / DC converters 231 to 233 into AC power. In the inverter circuit 223, the output power is adjusted by controlling the transistors TR11 to TR14 by PWM (Pulse Width Modulation). The AC power from the inverter circuit 223 is supplied to the commercial power system 203 via the switching unit 224.

  Here, when a ground fault occurs in the charging unit by the DC power supply unit 201, there is a possibility that a large current flows through the ground fault unit to cause ignition, smoke generation, or electric shock. In order to prevent this, ground fault detection circuits 225 to 227, a control unit 228, and a display unit 229 are provided. One of the input terminals of the ground fault detection circuit 225 is connected to the positive terminal of the solar cell module 211, the other input terminal is connected to the negative terminal of the solar cell module 211, and the ground fault in the charging unit by the solar cell module 211 is detected. To detect. The ground fault detection circuit 226 has one input terminal connected to the positive terminal of the solar cell module 212, the other input terminal connected to the negative terminal of the solar cell module 212, and a ground fault in the charging unit by the solar cell module 212. To detect. The ground fault detection circuit 227 has one input terminal connected to the positive terminal of the solar cell module 213, the other input terminal connected to the negative terminal of the solar cell module 213, and a ground fault in the charging unit by the solar cell module 213. To detect.

  FIG. 16 is a circuit diagram showing in detail the configuration of ground fault detection circuit 225 shown in FIG. In FIG. 16, this ground fault detection circuit 225 includes resistance elements 241 to 246, a current detector 247, and unidirectional elements 248 and 249. Here, the output voltage of the solar cell module 211 is E.

  The positive terminal of the solar cell module 211 is connected to the node N31, and the negative terminal is connected to the node N36. Resistance element 241 is connected between nodes N31 and N32. Resistance element 242 is connected between nodes N32 and N36. Node N32 is connected to a line of ground potential GND. The galvanometer 247 is connected between the node N32 and the node N33. Resistance element 243 is connected between nodes N31 and N34, and resistance element 244 is connected between nodes N34 and N36. Resistance element 245 is connected between nodes N31 and N35, and resistance element 246 is connected between nodes N35 and N36. The unidirectional element 248 is connected between the node N34 and the node N33, and the unidirectional element 249 is connected between the node N33 and the node N35.

  Here, the resistance value of the resistance element 241 is RP11, the resistance value of the resistance element 242 is RN11, the resistance value of the resistance element 243 is RP12, the resistance value of the resistance element 244 is RN12, the resistance value of the resistance element 245 is RP13, and the resistance element When the resistance value of 246 is RN13, the following formulas (1) and (2) are established.

RN11 / (RP11 + RN11)> RN12 / (RP12 + RN12) (1)
RP11 / (RP11 + RN11)> RP13 / (RP13 + RN13) (2)
From these formulas (1) and (2), in a normal state where no ground fault occurs, the potential of the node N34 is set to a potential (negative potential) lower than the potential (GND) of the node N32, and the potential of the node N35. Is set to a potential (positive potential) higher than the potential (GND) of the node N32. For this reason, a reverse voltage is applied to both unidirectional elements 248 and 249, and no current flows through the galvanometer 247.

  When a ground fault occurs on the positive terminal side of the charging unit by the solar cell module 211, the potential of the ground fault part is set to the ground potential GND. As a result, since the potential of the node N31 is lowered to the ground potential GND, the potential of the node N34 becomes −E × RP12 / (RP12 + RN12), and the potential of the node N35 becomes −E × RP13 / (RP13 + RN13). Therefore, a forward voltage is applied to the unidirectional element 249, a current flows from the node N32 to the node N35 via the galvanometer 247 and the unidirectional element 249, and a ground fault is detected. Note that since a reverse voltage remains applied to the unidirectional element 248, no current flows through the unidirectional element 248.

  On the other hand, when a ground fault occurs on the negative terminal side of the charging unit by the solar cell module 211, the potential of the node N36 rises to the ground potential GND, so that the potential of the node N34 becomes E × RN12 / (RP12 + RN12). The potential of N35 is E × RN13 / (RP13 + RN13). Therefore, a forward voltage is applied to unidirectional element 248, a current flows from node N34 to node N32 via unidirectional element 248 and galvanometer 247, and a ground fault is detected. Note that since a reverse voltage remains applied to the unidirectional element 249, no current flows through the unidirectional element 249.

  Returning to FIG. 15, the ground fault detection circuits 226 and 227 have the same configuration as the ground fault detection circuit 225 shown in FIG. 16, and operate in the same manner. When a ground fault is detected by the ground fault detection circuits 225 to 227, the control unit 228 quickly switches the switch circuits SW41 to SW46, SW51, and SW52 from the on state to the off state and stops the operation of the inverter circuit 223. . Therefore, the expansion of the power outage range and the public disaster when a ground fault occurs can be prevented. The control unit 228 further causes the display unit 229 to display a ground fault occurrence warning. As a result, the user can quickly recognize the occurrence of a ground fault.

  The following Patent Document 1 discloses an inexpensive and simple DC ground fault detection device that can obtain a constant ground fault detection sensitivity even when the DC power supply voltage fluctuates. According to this, it is possible to obtain a constant ground fault detection level that is unrelated to fluctuations in the power supply voltage.

  Patent Document 2 below discloses a DC ground fault detection device that can be set without being influenced by an input voltage in which the detection level of the ground fault resistance varies. According to this, even if the input voltage fluctuates like a solar cell, the detection level of the ground fault resistance does not fluctuate.

Patent Document 3 below discloses a ground fault detection device that can accurately detect a ground fault location even if the output voltage of a DC power supply fluctuates.
Japanese Patent Laid-Open No. 62-236320 JP-A-9-215175 Japanese Patent Laid-Open No. 2001-21606

  However, in the conventional power supply apparatus using a plurality of DC power supplies, it is necessary to provide a plurality of ground fault detection circuits corresponding to each of the plurality of DC power supplies. There was a problem that it was necessary and the cost increased. In addition, there is a problem that wiring becomes complicated and reliability is lowered.

  Therefore, a main object of the present invention is to provide a power supply device that is low in cost and highly reliable in detecting a ground fault.

  A power supply device according to the present invention is a power supply device that converts DC power generated by a plurality of DC power generators into AC power and supplies the AC power to a load, and is provided corresponding to each of the plurality of DC power generators. A plurality of DC / DC converters each converting the output voltage of the corresponding DC power generator into a predetermined voltage and outputting the voltage to the first node; and the DC power applied to the first node as AC power An inverter that converts the power to the commercial power system and is provided corresponding to each of the plurality of DC power generators, each one electrode is connected to the positive terminal of the corresponding DC power generator, and each other electrode is Connected to multiple resistors connected to each other, the other electrode of the multiple resistors, and the negative terminal of the multiple DC power generators to detect ground faults in the charging section by multiple DC power generators, and detect ground faults Signal The first is that a ground fault detection circuit.

  A power supply device according to the present invention is a power supply device that converts DC power generated by a plurality of DC power generators into AC power and supplies the AC power to a commercial power system, each corresponding to a plurality of DC power generators A plurality of DC / DC converters, each of which converts an output voltage of a corresponding DC power generator into a predetermined voltage and outputs the voltage to a first node; and DC power applied to the first node An inverter for converting into AC power and supplying it to the commercial power system, each provided corresponding to a plurality of DC power generators, each one electrode is connected to the positive terminal of the corresponding DC power generator, each other A plurality of resistors whose electrodes are connected to each other, the other electrode of the plurality of resistors, and negative terminals of the plurality of DC power generators are detected, and ground faults of the charging unit by the plurality of DC power generators are detected. Fault detection It is obtained by a first ground fault detection circuit for outputting a degree.

  Preferably, the first ground fault detection circuit includes a first input node commonly connected to the other electrodes of the plurality of resistors and a second input node commonly connected to the negative terminals of the plurality of DC power generators. A first voltage dividing circuit including first and second resistance elements connected in series between the first and second resistance elements, wherein an output node between the first and second resistance elements is connected to a reference potential line; The third and fourth resistance elements are connected in series between one input node and the second input node. Normally, the reference potential is output from the output node between the third and fourth resistance elements. The ground fault detection signal is output, and the voltage across the terminals of the first resistance element is greater than the voltage between the terminals of the second resistance element by a predetermined level or more due to the ground fault of the charging unit by a plurality of DC power generators. In response, the reference potential from the output node between the third and fourth resistance elements A ground fault detection signal having a higher potential is output, and the voltage between the terminals of the second resistance element is equal to or higher than a predetermined level with respect to the voltage between the terminals of the first resistance element due to the ground fault of the charging unit by a plurality of DC power generators. And a second voltage dividing circuit that outputs a ground fault detection signal having a potential lower than the reference potential from the output node between the third and fourth resistance elements in response to the increase.

  Preferably, the first ground fault detection circuit includes a first input node commonly connected to the other electrodes of the plurality of resistors and a second input commonly connected to the negative terminals of the plurality of DC power generators. A first voltage dividing circuit including first and second resistance elements connected in series with the node, the output node between the first and second resistance elements being connected to a reference potential line; The third and fourth resistance elements are connected in series between the first input node and the second input node, and the reference potential is normally supplied from the output node between the third and fourth resistance elements. When the following potential is output and the voltage between the terminals of the first resistance element is greater than the voltage between the terminals of the second resistance element due to ground faults at the output portions of the plurality of DC power generators, Higher than the reference potential from the output node between the third and fourth resistance elements A second voltage dividing circuit for outputting a voltage and fifth and sixth resistance elements connected in series between the first input node and the second input node. A potential higher than the reference potential is output from the output node between the six resistance elements, and the voltage between the terminals of the second resistance element is changed between the terminals of the first resistance element due to the ground fault of the output portions of the plurality of DC power generators A third voltage dividing circuit that outputs a potential lower than the reference potential from the output node between the fifth and sixth resistance elements when the voltage exceeds a predetermined level or more than the voltage; A ground fault detection signal is output, the reference potential is compared with the potential of the output node of the second voltage dividing circuit, and the potential of the output node of the second voltage dividing circuit is made higher than the reference potential. Outputs a ground fault detection signal with a potential higher than the reference potential, and the reference potential and the third divided voltage Is compared with the potential of the output node of the third voltage dividing circuit and outputs a ground fault detection signal having a potential lower than the reference potential in response to the potential of the output node of the third voltage dividing circuit being made lower than the reference potential. Circuit.

  Preferably, the resistance value of at least one of the plurality of resistance elements included in the first ground fault detection circuit is variable.

  Preferably, the at least one resistance element includes first and second sub-resistance elements whose one electrodes are connected to each other, the other electrode of the first sub-resistance element, and the other electrode of the second sub-resistance element. And a first switch circuit that is turned on / off in response to an external control signal.

  Preferably, the at least one resistance element is connected between the first and second sub-resistance elements connected in series and between one electrode and the other electrode of the second sub-resistance element, and a control signal from the outside And a first switch circuit that is turned on / off in response to.

  In addition, preferably, when the potential of the ground fault detection signal is within a predetermined range, it is determined that no ground fault has occurred in the charging unit by the plurality of DC power generators, and the ground fault detection signal When the potential is not within the predetermined range, a control unit is provided that determines that a ground fault has occurred in the charging unit by the plurality of DC power generators.

  Preferably, the control unit electrically cuts off a path between the plurality of DC power generators and the commercial power system when it is determined that a ground fault has occurred in the charging unit by the plurality of DC power generators. .

  Preferably, the predetermined range is substantially a reference potential.

  Further preferably, the predetermined range is a range between a positive deviation reference value higher than the reference potential and a negative deviation reference value lower than the reference potential.

  In addition, preferably, a maximum voltage detection unit that measures the highest output voltage among the output voltages of each of the plurality of DC power generators is further provided. The control unit sets the positive deviation reference value and the negative deviation reference value according to the voltage measured by the maximum voltage detection unit.

  Preferably, the control unit sets and changes the positive-side deviation reference value and the negative-side deviation reference value according to the on / off state of the first switch circuit of at least one resistance element.

  Preferably, the first ground fault detection circuit is further connected between the output node of the first voltage dividing circuit and the reference potential line, and responds to a control signal from the outside in order to detect a ground fault. When the operation is performed, the output node of the first voltage dividing circuit and the reference potential line are connected. When the ground fault detection operation is not performed, the output node of the first voltage dividing circuit and the reference potential line are electrically connected. A second switch circuit that disconnects the first switch circuit from the second switch circuit.

  Further preferably, the ground electrode is connected to the other electrode of the plurality of resistors and the negative terminal of the plurality of DC power generators, detects a ground fault of the charging unit by the plurality of DC power generators, and outputs a ground fault detection signal. The second ground fault detection circuit having the same configuration as the first ground fault detection circuit and the first ground fault detection circuit are output in response to an external control signal. And a selection circuit that selectively gives a ground fault detection signal to the control unit. The resistance value of at least one of the plurality of resistance elements included in the second ground fault detection circuit is different from the resistance value of the corresponding resistance element of the first ground fault detection circuit.

  Preferably, even when a ground fault occurs at the positive terminal of any of the plurality of DC power generators, the potential of the ground fault detection signal is set to a potential lower than the reference potential. The output voltage of each of the plurality of DC power generators is predetermined.

  Preferably, each of the plurality of DC power generators is a solar cell.

  Preferably, the DC / DC converter includes an insulating transformer that performs a transformation operation in a state where the input terminal and the output terminal are insulated.

  Preferably, the first switch circuit includes a field effect transistor.

  Preferably, the first switch circuit is a jumper switch.

  In the power supply device according to the present invention, each is provided corresponding to a plurality of DC power generators, each of which converts the output voltage of the corresponding DC power generator into a predetermined voltage and outputs it to the first node. A plurality of DC / DC converters, an inverter for converting the DC power supplied to the first node into AC power and supplying the commercial power system, and a plurality of DC power generators, respectively, One electrode is connected to the positive terminal of the corresponding DC power generator, each of the other electrodes is connected to each other, and the other electrode of the resistors is connected to the other electrode and the negative terminals of the DC power generators And a first ground fault detection circuit that detects a ground fault of the charging unit by a plurality of DC power generators and outputs a ground fault detection signal. Therefore, a ground fault is detected by providing one ground fault detection circuit for a plurality of DC power generators. For this reason, cost reduction can be achieved compared with the conventional case where a plurality of ground fault detection circuits are provided corresponding to each of the plurality of DC power supplies. Further, since the circuit configuration is simplified, the reliability of ground fault detection is improved.

  Preferably, the first ground fault detection circuit includes a first input node commonly connected to the other electrodes of the plurality of resistors and a second input node commonly connected to the negative terminals of the plurality of DC power generators. A first voltage dividing circuit including first and second resistance elements connected in series between the first and second resistance elements, wherein an output node between the first and second resistance elements is connected to a reference potential line; The third and fourth resistance elements are connected in series between one input node and the second input node. Normally, the reference potential is output from the output node between the third and fourth resistance elements. The ground fault detection signal is output, and the voltage across the terminals of the first resistance element is greater than the voltage between the terminals of the second resistance element by a predetermined level or more due to the ground fault of the charging unit by a plurality of DC power generators. In response, the reference potential from the output node between the third and fourth resistance elements A ground fault detection signal having a higher potential is output, and the voltage between the terminals of the second resistance element is equal to or higher than a predetermined level with respect to the voltage between the terminals of the first resistance element due to the ground fault of the charging unit by a plurality of DC power generators. And a second voltage dividing circuit that outputs a ground fault detection signal having a potential lower than the reference potential from the output node between the third and fourth resistance elements in response to the increase. In this case, a ground fault is detected when the potential of the output node of the second voltage dividing circuit changes from the reference potential.

  Preferably, the first ground fault detection circuit includes a first input node commonly connected to the other electrodes of the plurality of resistors and a second input commonly connected to the negative terminals of the plurality of DC power generators. A first voltage dividing circuit including first and second resistance elements connected in series with the node, the output node between the first and second resistance elements being connected to a reference potential line; The third and fourth resistance elements are connected in series between the first input node and the second input node, and the reference potential is normally supplied from the output node between the third and fourth resistance elements. When the following potential is output and the voltage between the terminals of the first resistance element is greater than the voltage between the terminals of the second resistance element due to ground faults at the output portions of the plurality of DC power generators, Higher than the reference potential from the output node between the third and fourth resistance elements A second voltage dividing circuit for outputting a voltage and fifth and sixth resistance elements connected in series between the first input node and the second input node. A potential higher than the reference potential is output from the output node between the six resistance elements, and the voltage between the terminals of the second resistance element is changed between the terminals of the first resistance element due to the ground fault of the output portions of the plurality of DC power generators A third voltage dividing circuit that outputs a potential lower than the reference potential from the output node between the fifth and sixth resistance elements when the voltage exceeds a predetermined level or more than the voltage; A ground fault detection signal is output, the reference potential is compared with the potential of the output node of the second voltage dividing circuit, and the potential of the output node of the second voltage dividing circuit is made higher than the reference potential. Outputs a ground fault detection signal with a potential higher than the reference potential, and the reference potential and the third divided voltage Is compared with the potential of the output node of the third voltage dividing circuit and outputs a ground fault detection signal having a potential lower than the reference potential in response to the potential of the output node of the third voltage dividing circuit being made lower than the reference potential. Circuit. In this case, the ground fault is detected by comparing the potentials of the output nodes of the first to third voltage dividing circuits.

  Preferably, the resistance value of at least one of the plurality of resistance elements included in the first ground fault detection circuit is variable. In this case, a state in which ground fault detection is impossible can be avoided, and the ground fault is reliably detected.

  Preferably, the at least one resistance element includes first and second sub-resistance elements whose one electrodes are connected to each other, the other electrode of the first sub-resistance element, and the other electrode of the second sub-resistance element. And a first switch circuit that is turned on / off in response to an external control signal. Also in this case, it is possible to avoid a state in which ground fault detection is impossible, and the ground fault is reliably detected.

  Preferably, the at least one resistance element is connected between the first and second sub-resistance elements connected in series and between one electrode and the other electrode of the second sub-resistance element, and a control signal from the outside And a first switch circuit that is turned on / off in response to. Also in this case, it is possible to avoid a state in which ground fault detection is impossible, and the ground fault is reliably detected.

  In addition, preferably, when the potential of the ground fault detection signal is within a predetermined range, it is determined that no ground fault has occurred in the charging unit by the plurality of DC power generators, and the ground fault detection signal When the potential is not within the predetermined range, a control unit is provided that determines that a ground fault has occurred in the charging unit by the plurality of DC power generators. In this case, the control unit determines whether or not a ground fault has occurred based on the potential of the ground fault detection signal.

  Preferably, the control unit electrically cuts off a path between the plurality of DC power generators and the commercial power system when it is determined that a ground fault has occurred in the charging unit by the plurality of DC power generators. . In this case, expansion of the power outage range and public disasters when a ground fault occurs are prevented.

  Preferably, the predetermined range is substantially a reference potential. In this case, whether or not a ground fault has occurred is determined based on whether or not the potential of the ground fault detection signal is substantially the reference potential.

  Further preferably, the predetermined range is a range between a positive deviation reference value higher than the reference potential and a negative deviation reference value lower than the reference potential. In this case, the ground fault detection sensitivity can be equalized by individually setting the positive side deviation reference value and the negative side deviation reference value.

  In addition, preferably, a maximum voltage detection unit that measures the highest output voltage among the output voltages of each of the plurality of DC power generators is further provided. The control unit sets the positive deviation reference value and the negative deviation reference value according to the voltage measured by the maximum voltage detection unit. In this case, the ground fault detection sensitivity can be further equalized.

  Preferably, the control unit sets and changes the positive-side deviation reference value and the negative-side deviation reference value according to the on / off state of the first switch circuit of at least one resistance element. In this case, the ground fault detection sensitivity can be further equalized.

  Preferably, the first ground fault detection circuit is further connected between the output node of the first voltage dividing circuit and the reference potential line, and responds to a control signal from the outside in order to detect a ground fault. When the operation is performed, the output node of the first voltage dividing circuit and the reference potential line are connected. When the ground fault detection operation is not performed, the output node of the first voltage dividing circuit and the reference potential line are electrically connected. A second switch circuit that disconnects the first switch circuit from the second switch circuit. In this case, the ground fault detection operation can be performed at an arbitrary timing.

  Further preferably, the ground electrode is connected to the other electrode of the plurality of resistors and the negative terminal of the plurality of DC power generators, detects a ground fault of the charging unit by the plurality of DC power generators, and outputs a ground fault detection signal. The second ground fault detection circuit having the same configuration as the first ground fault detection circuit and the first ground fault detection circuit are output in response to an external control signal. And a selection circuit that selectively gives a ground fault detection signal to the control unit. The resistance value of at least one of the plurality of resistance elements included in the second ground fault detection circuit is different from the resistance value of the corresponding resistance element of the first ground fault detection circuit. Also in this case, it is possible to avoid a state in which ground fault detection is impossible, and the ground fault is reliably detected.

  Preferably, even when a ground fault occurs at the positive terminal of any of the plurality of DC power generators, the potential of the ground fault detection signal is set to a potential lower than the reference potential. The output voltage of each of the plurality of DC power generators is predetermined. In this case, a state in which ground fault detection is impossible can be avoided, and the ground fault is reliably detected.

  Preferably, each of the plurality of DC power generators is a solar cell. Also in this case, it is possible to avoid a state in which ground fault detection is impossible, and the ground fault is reliably detected.

  Preferably, the DC / DC converter includes an insulating transformer that performs a transformation operation in a state where the input terminal and the output terminal are insulated. In this case, since the plurality of DC power generators and the commercial power system are insulated, the ground fault can be detected in a safe state.

  Preferably, the first switch circuit includes a field effect transistor. In this case, it is possible to reduce the volume and extend the life of the first switch circuit.

  Preferably, the first switch circuit is a jumper switch. In this case, the mounting of the first switch circuit can be facilitated and the cost can be reduced.

[Embodiment 1]
1 is a circuit block diagram showing a schematic configuration of a photovoltaic power generation system using a power supply device according to Embodiment 1 of the present invention. In FIG. 1, this power supply device (system interconnection device) is configured by a system interconnection inverter device 2, converts the DC power generated by the DC power supply unit 1 into AC power, and supplies the AC power to the commercial power system 3. In a normal state where no ground fault occurs, the switch circuits SW1 to SW6, SW11, and SW12 are turned on.

  DC power supply unit 1 includes solar cell modules 11 to 13. The grid interconnection inverter device 2 includes switching units 21 and 24, a DC / DC converter unit 22, an inverter circuit 23, a ground fault detection unit 25, a control unit 26, and a display unit 27. Switching unit 21 includes switch circuits SW1 to SW6. The DC / DC converter unit 22 includes DC / DC converters 31 to 33. Inverter circuit 23 includes transistors TR1 to TR4. Switching unit 24 includes switch circuits SW11 and SW12. The ground fault detection unit 25 includes resistors 41 to 43 and a ground fault detection circuit 44.

  The solar cell modules 11 to 13 convert solar energy into electric energy and supply DC power to the grid interconnection inverter device 2. These solar cell modules 11 to 13 are modules obtained by connecting a plurality of solar cells in series. The rated voltage of each of the solar cell modules 11 to 13 is 200V, and the rated power is 1500W. In a solar power generation system for home use, for example, a single crystal silicon solar battery cell is used.

  The DC / DC converters 31 to 33 receive the DC power generated by the solar cell modules 11 to 13 via the switching unit 21, respectively. These DC / DC converters 31 to 33 convert the DC voltage obtained from the solar cell modules 11 to 13 to a predetermined voltage (for example, 350 V) by a switching regulator, respectively. Moreover, the DC / DC converters 31-33 efficiently take out the direct-current power from the solar cell modules 11-13 using the maximum power follow-up method (mountain climbing method), respectively. Since these DC / DC converters 31 to 33 use an insulating transformer for insulating the primary side and the secondary side, the DC power supply unit 1 and the commercial power system 3 are insulated. The output parts of the DC / DC converters 31 to 33 are coupled together and connected to the inverter circuit 23.

  The inverter circuit 23 converts the DC power from the DC / DC converters 31 to 33 into AC power. In the inverter circuit 23, the transistors TR1 to TR4 are PWM controlled to adjust the output power. AC power from the inverter circuit 23 is supplied to the commercial power system 3 via the switching unit 24.

  Here, when a ground fault occurs at a node having a charging unit by the DC power supply unit 1, the DC power supply unit 1 and the commercial power system 3 are insulated by the DC / DC converters 31 to 33 using an insulating transformer. There is no danger of a large current flowing at that time. However, safety is not ensured if a ground fault is further caused to a node on the opposite polarity side to the node where the ground fault occurs. Therefore, in order to detect a ground fault at the time when only one node of the charging unit by the DC power supply unit 1 is grounded, that is, before a danger such as a large current flows, resistors 41 to 43, ground faults are detected. A detection circuit 44, a control unit 26, and a display unit 27 are provided. By providing the resistors 41 to 43, it is possible to prevent the current from flowing back to the solar cell modules 11 to 13 when the difference between the output voltages of the solar cell modules 11 to 13 is large.

  One input terminal of the ground fault detection circuit 44 is connected to the plus terminal of the solar cell module 11 through the resistor 41, and is connected to the plus terminal of the solar cell module 12 through the resistor 42, and the resistor. It is connected to the plus terminal of the solar cell module 13 through 43. The other input terminal of the ground fault detection circuit 44 is commonly connected to each minus terminal of the solar cell modules 11 to 13. When a ground fault occurs in the charging unit by the solar cell modules 11 to 13, the ground fault is detected by the ground fault detection circuit 44. The ground fault detection circuit 44 outputs a ground fault detection signal to the control unit 26.

  FIG. 2 is a circuit diagram showing in detail the configuration of the ground fault detection circuit 44 shown in FIG. In FIG. 2, this ground fault detection circuit 44 includes resistance elements 51 to 57, a switch circuit SW <b> 13 and diodes 58 and 59. Here, the output voltages of the solar cell modules 11 to 13 are E1 to E3, respectively.

  The positive terminals of the solar cell modules 11 to 13 are commonly connected to the node N1 through resistors 41 to 43, respectively. The negative terminals of the solar cell modules 11 to 13 are commonly connected to the node N6. Resistance element 51 is connected between nodes N1 and N2, and resistance element 52 is connected between nodes N2 and N6. Switch circuit SW13 is connected between node N2 and the line of ground potential GND, and resistance element 53 is connected between node N2 and output node N3. Resistance element 54 is connected between nodes N1 and N4, and resistance element 55 is connected between nodes N4 and N6. Resistance element 56 is connected between nodes N1 and N5, and resistance element 57 is connected between nodes N5 and N6. Diode 58 is connected between node N4 and output node N3, and diode 59 is connected between output node N3 and node N5. A ground fault detection signal is given from output node N3 to control unit 26 shown in FIG.

  Resistive elements 51 and 52 constitute a voltage dividing circuit, and divide the voltage between nodes N1 and N6. Resistive elements 54 and 55 constitute a voltage dividing circuit, and the voltage between nodes N1 and N6 is divided to determine the potential of node N4. Resistive elements 56 and 57 constitute a voltage dividing circuit, and voltage between nodes N1 and N6 is divided to determine the potential of node N5.

  Here, the resistance value of the resistance element 51 is RP1, the resistance value of the resistance element 52 is RN1, the resistance value of the resistance element 54 is RP2, the resistance value of the resistance element 55 is RN2, the resistance value of the resistance element 56 is RP3, and the resistance element When the resistance value of 57 is RN3, the following mathematical formulas (3) and (4) are established.

RN1 / (RP1 + RN1) ≧ RN2 / (RP2 + RN2) (3)
RP1 / (RP1 + RN1) ≧ RP3 / (RP3 + RN3) (4)
For example, the resistance values RP1 and RN1 are 2.91 MΩ, the resistance values are RP2 and RN3 are 3.00 MΩ, and RN2 and RP3 are 2.82 MΩ.

  Switch circuit SW13 is turned on when a ground fault detection operation is performed by an external control signal, and is turned off when a ground fault detection operation is not performed. For example, the ground fault detection operation is performed only at the start of power generation of the solar cell by turning on the switch circuit SW13 only at the start of power generation of the solar cell modules 11-13. Further, when the switch circuit SW13 is controlled to be turned on / off at regular intervals, the ground fault detection operation can be performed at regular intervals. Thus, by providing the switch circuit SW13, the ground fault detection operation can be performed at an arbitrary timing.

  At the time of ground fault detection operation, in a state where no ground fault has occurred, the potential of the node N2 is set to the ground potential GND in response to the switch circuit SW13 being turned on. Therefore, from Equations (3) and (4), the potential of the node N4 is set to be equal to or lower than the potential of the node N2 (GND), and the potential of the node N5 is equal to the potential of the node N2 (GND). Or higher potential. Therefore, no forward voltage is applied to the diodes 58 and 59, and no current flows through the resistance element 53 for detecting a ground fault. At this time, a ground fault detection signal of ground potential GND is output from output node N3. Here, the resistance value of the resistance element 53 is set to a sufficiently small value (for example, 30 kΩ) as compared with the resistance values of the resistance elements 51, 52, 54 to 57.

  Next, an operation when a ground fault occurs on the positive terminal side of the solar cell module 11 will be described. When a ground fault occurs in the distribution line between the solar cell module 11 and the resistor 41 due to insulation deterioration or insulation failure and a current flows between the distribution line and the ground, the potential of the ground fault part is the ground potential GND. To be. When the output voltages of solar cell modules 11 to 13 are all equal, the potential at node N1 is lowered in response to the ground potential being set to ground potential GND. At this time, when the voltage between the terminals of the resistance element 52 becomes larger than the voltage between the terminals of the resistance element 51 by a predetermined level or more, the potential of the node N5 decreases to a negative potential and a forward voltage is applied to the diode 59, and the node N2 Current flows through resistance element 53 and diode 59 to node N5. The potential of output node N3 is set to the same potential (negative potential) as node N5. Note that since a reverse voltage is applied to the diode 58 in response to the negative potential of the node N4, no current flows through the diode 58. In this manner, the diodes 58 and 59 constitute a comparison circuit, which compares the potential (GND) of the node N2 with the potentials of the nodes N4 and N5, and changes the potential of the output node N3 according to the comparison result. Therefore, when a ground fault occurs on the positive terminal side of the solar cell modules 11 to 13, a negative potential ground fault detection signal is output from the output node N3.

  Here, even if a ground fault occurs on the positive terminal side of the solar cell modules 11 to 13, it can be assumed that a ground fault is not detected. When the solar cell modules 11 to 13 are installed at different angles, the output voltages E1 to E3 of the solar cell modules 11 to 13 may be different depending on the amount of solar radiation. For example, when the output voltage E1 of the solar cell module 11 is sufficiently smaller than the output voltages E2 and E3 of the solar cell modules 12 and 13, a ground fault occurs in the distribution line between the solar cell module 11 and the resistor 41. Even in this case, the potential of the node N1 may not be sufficiently lowered. In this case, the potential of the node N5 is not sufficiently lowered, and the forward voltage exceeding the threshold voltage is not applied to the diode 59. At this time, the ground fault is not detected, and the ground fault detection signal of the ground potential GND is output from the output node N3.

  For example, the output voltages E1 to E3 of the solar cell modules 11 to 13 are generated on the positive terminal side of the solar cell modules 11 to 13 in a special case where the undetectable conditions shown in the following formulas (5) to (7) are satisfied. The detected ground fault is not detected. Here, for easy understanding, the resistance values RP1, RN1, RP2, RN2, RP3, and RN3 of the resistance elements 51, 52, and 54 to 57 are all RPN.

E1≈RPN × (E2 + E3) / (3 × RP0 + 5 × RPN) (5)
E2≈RPN × (E1 + E3) / (3 × RP0 + 5 × RPN) (6)
E3≈RPN × (E1 + E2) / (3 × RP0 + 5 × RPN) (7)
However, the resistance values of the resistors 41 to 43 are all RP0 (for example, 1.00 MΩ). In a special case where the non-detectable condition shown in Equation (5) is satisfied, the ground fault generated on the positive terminal side of the solar cell module 11 is not detected. Further, in a special case that satisfies the non-detectable condition shown in Expression (6), the ground fault generated on the positive terminal side of the solar cell module 12 is not detected. Further, in a special case that satisfies the non-detectable condition shown in Expression (7), the ground fault generated on the positive terminal side of the solar cell module 13 is not detected.

  Here, the reason why Expressions (5) to (7) are established will be described. FIG. 3 is a circuit diagram for explaining the reason why Formula (5) is satisfied, and is a diagram to be compared with FIG. Referring to the circuit diagram of FIG. 3, the difference from the circuit diagram of FIG. 2 is that n solar cell modules 11 to 13 (where n is an arbitrary natural number) are replaced by DC power supplies DCPS1 to DCPSn. The resistors 41 to 43 are replaced with n resistors RDCPS1 to RDCPSn, and the switch circuit SW13 is omitted. Here, the output voltages of the DC power supplies DCPS1 to DCPSn are E1 to En, and the resistance values RP1, RN1, RP2, RN2, RP3, and RN3 of the resistance elements 51, 52, and 54 to 57 are all RPN.

  In FIG. 3, the potential of the node N1 is E0. When a ground fault occurs in the distribution line between the DC power supply DCPS1 and the resistor RDCPS1, the potential of the node N6 is set to −E1. Here, when the potential E0 of the node N1 does not sufficiently decrease and the potential E0 = E1, the potentials of the nodes N2, N4, and N5 are both set to the ground potential GND. Therefore, no forward voltage is applied to the diodes 58 and 69, and no current flows between the node N4 and the node N2 and between the node N2 and the node N5 (see the dotted line portion).

  FIG. 4 is an equivalent circuit diagram obtained by simplifying the circuit diagram shown in FIG. In FIG. 4, the resistance elements 54 to 57 shown in FIG. The resistance value of the resistance element 61 is RPN. Further, the ground fault between DC power supply DCPS1 and resistor RDCPS1 and node N2 are both connected to a line of ground potential GND.

  Here, according to Kirchhoff's law, the sum of the currents flowing into the node N1 becomes 0, so the following formula (8) is established.

  In this equation (8), when E1 = E0 is substituted and arranged, the following equation (9) is established.

  By substituting n = 3 in this equation (9), the above equation (5) is derived. Further, Equations (6) and (7) are derived in the same manner as Equation (5).

  However, in actuality, even when a condition that satisfies the non-detectable conditions shown in Equations (5) to (7) occurs temporarily, it is impossible to detect a ground fault because the output voltage of the solar cell has a characteristic that fluctuates. Therefore, a ground fault can be detected reliably. In the case of using a DC power source that outputs a constant voltage other than a solar battery, ground fault detection can be achieved if the output voltage of the DC power source does not satisfy the undetectable conditions shown in equations (5) to (7). An impossible state can be avoided.

  Returning to FIG. 2, the operation when a ground fault occurs on the negative terminal side of the solar cell module 11 will be described next. When a ground fault occurs in the distribution line between the solar cell module 11 and the node N6, the potential of the ground fault portion is set to the ground potential GND. Accordingly, the potential of node N6 rises from the negative potential to the ground potential GND, the voltage between terminals of resistance element 51 increases, the voltage between terminals of resistance element 52 becomes almost 0 V, and the potential of node N4 becomes Raised to positive potential. Therefore, a forward voltage is applied to diode 58, and a current flows from node N4 to node N2 via diode 58 and resistance element 53. At this time, the potential of the output node N3 is set to the same potential (positive potential) as that of the node N4. Note that since a reverse voltage is applied to the diode 59 in response to the potential of the node N5 being a positive potential, no current flows through the diode 59. Thus, when a ground fault occurs on the negative terminal side of the solar cell modules 11 to 13, a positive ground fault detection signal is output from the output node N3. In this case, it is not necessary to consider the undetectable conditions shown in the formulas (5) to (7) as in the case where a ground fault occurs on the positive terminal side of the solar cell modules 11 to 13, and the ground fault is surely made. Is detected.

  Moreover, even if a ground fault occurs at the same time on both the positive terminal side and the negative terminal side of any one of the solar cell modules 11 to 13, if another solar cell module generates an output voltage, A ground fault is reliably detected.

  Returning to FIG. 1, when the ground fault detection signal from the ground fault detection circuit 44 is the ground potential GND, the control unit 26 determines that no ground fault has occurred, and the ground fault detection signal is a positive potential or If the potential is negative, it is determined that a ground fault has occurred. When it is determined that a ground fault has occurred, the switch circuits SW1 to SW6, SW11, and SW12 are quickly switched from the on state to the off state, and the operation of the inverter circuit 23 is stopped. Therefore, the expansion of the power outage range and the public disaster when a ground fault occurs can be prevented. The control unit 26 further displays a warning about the occurrence of a ground fault on the display unit 27. As a result, the user can quickly recognize the occurrence of a ground fault.

  1 and 2, only one of the resistors 41 to 43 is attached and the other two resistors are removed and the ground fault detection operation is performed. If a ground fault occurs on the positive terminal side of the solar cell module corresponding to the attached resistor, a ground fault is detected. If a ground fault occurs on the positive terminal side of another solar cell module, a ground fault occurs. Is not detected. Thereby, since a ground fault detection can be performed individually with respect to each of the solar cell modules 11 to 13, a ground fault occurrence location can be specified.

  Therefore, in the first embodiment, a ground fault is reliably detected by providing one ground fault detection circuit 44 for a plurality of DC power supplies. For this reason, cost reduction can be achieved as compared with the conventional case where it is necessary to provide a plurality of ground fault detection circuits corresponding to each of the plurality of DC power supplies. Further, since the circuit configuration is simplified, the reliability of ground fault detection is improved.

  In addition, although the case where the DC power supply unit 1 includes three solar cell modules 11 to 13 has been described here, the number of solar cell modules may be two or any number of four or more. Good.

  Moreover, although the case where the solar cell modules 11-13 were comprised with the single crystal silicon solar cell was demonstrated here, the solar cell modules 11-13 are other types of solar cells, such as a polycrystalline silicon solar cell and a compound semiconductor solar cell. You may comprise with a battery.

  Furthermore, although the case where the DC power supply unit 1 is a solar cell has been described here, the DC power supply unit 1 may be a DC power supply such as a fuel cell, or a combination thereof.

  In addition, although the power supply device comprised by the grid connection inverter apparatus 2 demonstrated the electric power supply to the commercial power grid 3 to which the load was connected as an example here, as shown in FIG. The same applies to the case where the power supply device configured as described above supplies power only to the load 5.

[Modification of Embodiment 1]
6 is a block diagram showing a schematic configuration of a photovoltaic power generation system using a power supply device according to a modification of the first embodiment of the present invention, and is a diagram to be compared with FIG. The solar power generation system of FIG. 6 is different from the solar power generation system of FIG. 1 in that the ground fault detection unit 25 is provided outside the grid interconnection inverter device 71. In FIG. 6, portions corresponding to those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  This power supply device includes a ground fault detection unit 25 and a grid interconnection inverter device 71, converts the DC power generated by the DC power supply unit 1 into AC power, and supplies the AC power to the commercial power system 3. In this way, when the ground fault detection unit 25 is provided outside the grid interconnection inverter device 71, the ground fault detection unit 25 can be arbitrarily attached or removed as necessary.

[Embodiment 2]
FIG. 7 is a circuit diagram showing in detail the configuration of ground fault detection circuit 81 according to the second embodiment of the present invention, which is compared with FIG. The ground fault detection circuit 81 in FIG. 7 is different from the ground fault detection circuit 44 in FIG. 2 in that resistance elements 91 to 93 and switch circuits SW14 to SW16 are added. In FIG. 7, parts corresponding to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  Resistance element 91 and switch circuit SW14 are connected in series between nodes N2 and N6. Resistance element 92 and switch circuit SW15 are connected in series between nodes N4 and N6. Resistance element 93 and switch circuit SW16 are connected in series between nodes N5 and N6.

  By arbitrarily turning on / off these switch circuits SW14 to SW16 by an external control signal, the ratio between the resistance value between the nodes N1 and N2 and the resistance value between the nodes N2 and N6, and the resistance between the nodes N1 and N4 The ratio between the value and the resistance value between nodes N4 and N6 and the ratio between the resistance value between nodes N1 and N5 and the resistance value between nodes N5 and N6 can be changed. Therefore, in this Embodiment 2, the state which cannot detect a ground fault as shown to Numerical formula (5)-(7) can be avoided, and a ground fault can be detected reliably.

  For example, N-channel MOS transistors are used for these switch circuits SW14 to SW16. The N-channel MOS transistor has advantages such as being able to pass a larger current than the P-channel MOS transistor, having a smaller volume and a longer life than other switching elements. Further, jumper switches may be used for these switch circuits SW14 to SW16. Since the jumper switch has a very simple structure in which the circuit is turned on / off by attaching / detaching a jumper plug to / from a signal pin on the circuit board, there is an advantage that it is easy to mount and inexpensive.

[Modification of Embodiment 2]
FIG. 8 is a circuit diagram showing in detail the configuration of ground fault detection circuit 101 according to the modification of the second embodiment of the present invention, and is a diagram to be compared with FIG. The ground fault detection circuit 101 in FIG. 8 is different from the ground fault detection circuit 44 in FIG. 2 in that resistance elements 111 to 113 and switch circuits SW17 to SW19 are added. In FIG. 8, portions corresponding to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  Resistance elements 52 and 111 are connected in series between nodes N2 and N6. Switch circuit SW17 is connected between nodes N11 and N6 between resistance elements 52 and 111. Resistance elements 55 and 112 are connected in series between nodes N4 and N6. Switch circuit SW18 is connected between nodes N12 and N6 between resistance elements 55 and 112. Resistance elements 57 and 113 are connected in series between nodes N5 and N6. Switch circuit SW19 is connected between nodes N13 and N6 between resistance elements 57 and 113.

  By arbitrarily turning on / off these switch circuits SW17 to SW19 by an external control signal, the ratio between the resistance value between the nodes N1 and N2 and the resistance value between the nodes N2 and N6, and the resistance between the nodes N1 and N4 The ratio between the value and the resistance value between nodes N4 and N6 and the ratio between the resistance value between nodes N1 and N5 and the resistance value between nodes N5 and N6 can be changed. Therefore, in the modified example of the second embodiment, as in the second embodiment, it is possible to avoid a state where ground fault detection is not possible as shown in the mathematical formulas (5) to (7). It can be detected reliably.

  For example, N-channel MOS transistors are used for these switch circuits SW17 to SW19. The N-channel MOS transistor has advantages such as being able to pass a larger current than the P-channel MOS transistor, having a smaller volume and a longer life than other switching elements. Further, jumper switches may be used for these switch circuits SW17 to SW19. A jumper switch has the advantage of being easy to mount and cheap.

[Embodiment 3]
FIG. 9 is a circuit block diagram showing a schematic configuration of a photovoltaic power generation system using a power supply device according to Embodiment 3 of the present invention, and is a diagram compared with FIG. The solar power generation system of FIG. 9 is different from the solar power generation system of FIG. 1 in that a ground fault detection circuit 131 and selection units 132 and 133 are added. The selection unit 132 includes switch circuits SW21 to SW24, and the selection unit 133 includes switch circuits SW25 and SW26. 9, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the ground fault detection unit 121, the ground fault detection circuit 131 is provided in parallel with the ground fault detection circuit 44. The node N21 is connected to the positive terminal of the solar cell module 11 through the resistor 41, is connected to the positive terminal of the solar cell module 12 through the resistor 42, and is connected to the solar cell module through the resistor 43. 13 positive terminals are connected. Node N22 is commonly connected to the negative terminals of solar cell modules 11-13. Switch circuit SW21 is connected between node N21 and one input terminal of ground fault detection circuit 44. Switch circuit SW22 is connected between node N22 and the other input terminal of ground fault detection circuit 44. Switch circuit SW23 is connected between node N21 and one input terminal of ground fault detection circuit 131. Switch circuit SW24 is connected between node N22 and the other input terminal of ground fault detection circuit 131. The switch circuit SW25 is connected between the output terminal of the ground fault detection circuit 44 and the input terminal of the control unit 26. The switch circuit SW26 is connected between the output terminal of the ground fault detection circuit 131 and the input terminal of the control unit 26.

  The circuit configuration of the ground fault detection circuit 131 is the same as that of the ground fault detection circuit 44, but the resistance values of the internal resistance elements are different. For this reason, the undetectable condition of the ground fault detection circuit 131 is different from the undetectable condition of the ground fault detection circuit 44 shown in the equations (5) to (7). The switch circuits SW21 to SW26 are controlled to be turned on / off by an external control signal so that a ground fault detection operation is performed in one of the ground fault detection circuits 44 and 131. That is, when the ground fault detection circuit 44 performs the ground fault detection operation, the switch circuits SW21, SW22, SW25 are turned on, and the switch circuits SW23, SW24, SW26 are turned off. On the other hand, when the ground fault detection circuit 131 performs the ground fault detection operation, the switch circuits SW23, SW24, SW26 are turned on, and the switch circuits SW21, SW22, SW25 are turned off. In this way, the ground fault detection signal output from one of the ground fault detection circuits 44 and 131 is selectively given to the control unit 26. Therefore, in this Embodiment 3, the state which cannot detect a ground fault as shown to Numerical formula (5)-(7) can be avoided, and a ground fault can be detected reliably.

[Embodiment 4]
FIG. 10 is a circuit diagram showing in detail the configuration of ground fault detection circuit 141 according to the fourth embodiment of the present invention, and is a diagram contrasted with FIG. The ground fault detection circuit 141 of FIG. 10 is different from the ground fault detection circuit 44 of FIG. 2 in that the resistance elements 54 to 57 and the diodes 58 and 89 are deleted and the resistance elements 151 and 152 are added. It is. Further, although the switch circuit SW13 is omitted in FIG. 10, the switch circuit SW13 may be provided as in FIG. 10, parts corresponding to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  Resistive elements 151 and 152 constitute a voltage dividing circuit, and the voltage between nodes N1 and N6 is divided to determine the potential of output node N3. The resistance value of the resistance element 151 is RP4, and the resistance value of the resistance element 152 is RN4. Here, each resistance value is set so that the voltage division ratio (RP1: RN1) of the resistance elements 51 and 52 is equal to the voltage division ratio (RP4: RN4) of the resistance elements 151 and 152. Since the voltage dividing ratio of the resistance elements 51 and 52 is equal to the voltage dividing ratio of the resistance elements 151 and 152, the potential of the output node N3 is set to the same ground potential GND as that of the node N2 in a state where no ground fault occurs.

  When a ground fault occurs on the positive terminal side of the solar cell module 11 and the distribution line between the solar cell module 11 and the resistor 41, the potential of the ground fault portion is set to the ground potential GND. When the output voltages of solar cell modules 11 to 13 are all equal, the potential at node N1 is lowered in response to the ground potential being set to ground potential GND. At this time, the voltage between the terminals of the resistance element 52 becomes larger than the voltage between the terminals of the resistance element 51, and the potential of the output node N3 is lowered from the ground potential GND to be a negative potential. Thus, when a ground fault occurs on the positive terminal side of the solar cell modules 11 to 13, a negative ground fault detection signal is output from the output node N3.

  When a ground fault occurs on the negative terminal side of the solar cell module 11 and the distribution line between the solar cell module 11 and the node N6, the potential of the ground fault portion is set to the ground potential GND. Accordingly, the potential of node N6 rises from the negative potential to the ground potential GND, the voltage between terminals of resistance element 51 increases, the voltage between terminals of resistance element 52 becomes approximately 0 V, and the potential of node N3 becomes It rises from the ground potential GND and is set to a positive potential. Thus, when a ground fault occurs on the negative terminal side of the solar cell modules 11 to 13, a positive ground fault detection signal is output from the output node N3.

  The control unit 26 (see FIG. 1) determines whether or not a ground fault has occurred based on whether or not the potential of the ground fault detection signal from the ground fault detection circuit 141 is within a predetermined range. Specifically, when the ground fault detection signal is higher than the negative deviation reference value and lower than the positive deviation reference value, it is determined that no ground fault has occurred. On the other hand, when the potential of the ground fault detection signal is lower than the preset negative side deviation reference value, and when the potential of the ground fault detection signal is higher than the preset positive side deviation reference value, a ground fault occurs. It is determined that When it is determined that a ground fault has occurred, the switch circuits SW1 to SW6, SW11, and SW12 are quickly switched from the on state to the off state, and the operation of the inverter circuit 23 is stopped.

  The amount of change in the potential of the output node N3 when a ground fault having a predetermined resistance value RG occurs on the positive terminal side of the solar cell module 11, and the ground having the predetermined resistance value RG on the negative terminal side of the solar cell module 11 In some cases, the amount of change in potential of the output node N3 when a fault occurs is different. For this reason, the positive side deviation reference value and the negative side deviation reference value are individually set. Thereby, the difference in the ground fault detection sensitivity when the ground fault occurs on the positive terminal side of the solar cell module and the ground fault occurs on the negative terminal side is corrected, and the ground fault detection sensitivity is equalized. Here, the case where the ground fault having the predetermined resistance value RG is generated means that the potential of the ground fault portion is set higher than the ground potential GND by an amount corresponding to the resistance value RG.

  Therefore, in the fourth embodiment, similarly to the first embodiment, the ground fault is reliably detected by providing one ground fault detection circuit 141 for a plurality of DC power supplies. For this reason, a low-cost power supply device with high reliability of ground fault detection can be realized. Furthermore, by setting the positive side deviation reference value and the negative side deviation reference value individually, the ground fault detection sensitivity can be equalized.

  In this way, in the control unit 26, whether a ground fault has occurred based on whether or not the potential of the ground fault detection signal is within a predetermined range determined by the negative side deviation reference value and the positive side deviation reference value. The determination method can be applied to the ground fault detection circuits 44, 81, and 101 described in the first to third embodiments. In this case, the same effect can be obtained.

[Embodiment 5]
FIG. 11 is a circuit block diagram showing a schematic configuration of a photovoltaic power generation system using a power supply device according to Embodiment 5 of the present invention, which is compared with FIG. The solar power generation system of FIG. 11 is different from the solar power generation system of FIG. 1 in that a voltage detection circuit 171 and diodes 172 to 174 are added, and the ground fault detection circuit 44 is replaced with a ground fault detection circuit 141. It is a point. This ground fault detection circuit 141 has the configuration shown in FIG. 10 in the fourth embodiment. In FIG. 11, portions corresponding to those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the ground fault detection unit 161, the positive terminals of the solar cell modules 11 to 13 are commonly connected to one input terminal of the voltage detection circuit 171 through the diodes 172 to 174. The negative terminals of the solar cell modules 11 to 13 are commonly connected to the other input terminal of the ground fault detection circuit 44. The voltage detection circuit 171 measures a voltage between one input terminal and the other input terminal. When the output voltages (DC voltages) of the solar cell modules 11 to 13 are different, the voltage detection circuit 171 measures the maximum output voltage among the output voltages of the solar cell modules 11 to 13. For example, when the output voltage of the solar cell module 11 is the maximum, a forward voltage is applied to the diode 172 and a reverse voltage is applied to the diodes 173 and 174. For this reason, the output voltage of the solar cell module 11 is measured by the voltage detection circuit 171. The voltage detection circuit 171 gives the measured voltage value to the control unit 26. The voltage detection circuit 171 and the diodes 172 to 174 constitute a maximum voltage detection unit 162.

  The control unit 26 determines whether or not a ground fault has occurred based on whether or not the potential of the ground fault detection signal from the ground fault detection circuit 141 is within a predetermined range. Specifically, when the ground fault detection signal is higher than the negative deviation reference value and lower than the positive deviation reference value, it is determined that no ground fault has occurred. On the other hand, when the potential of the ground fault detection signal is lower than the preset negative side deviation reference value, and when the potential of the ground fault detection signal is higher than the preset positive side deviation reference value, a ground fault occurs. It is determined that When it is determined that a ground fault has occurred, the switch circuits SW1 to SW6, SW11, and SW12 are quickly switched from the on state to the off state, and the operation of the inverter circuit 23 is stopped. Here, the negative side deviation reference value and the positive side deviation reference value are determined according to the measured voltage value given from the voltage detection circuit 171.

  FIG. 12 is a diagram showing the relationship between the positive side deviation reference value and the negative side deviation reference value set in the fifth embodiment and the measured voltage value. Referring to FIG. 12, the positive side deviation reference value is set to increase in proportion to the measured voltage value, and the negative side deviation reference value is set to decrease in proportion to the measured voltage value. This is because the amount of change in the potential of the ground fault detection signal when a ground fault occurs increases as the measured voltage value increases. Such a relationship between the deviation reference value and the measured voltage value may be programmed in advance in, for example, a microcomputer provided in the control unit 26.

  Therefore, in the fifth embodiment, the positive side deviation reference value and the negative side deviation reference value are set according to the voltage value measured by the maximum voltage detection unit 162. Thereby, further equalization of ground fault detection sensitivity is achieved.

[Embodiment 6]
FIG. 13 is a circuit diagram showing in detail the configuration of ground fault detection circuit 181 according to the sixth embodiment of the present invention, and is a diagram to be compared with FIG. The ground fault detection circuit 181 in FIG. 13 is different from the ground fault detection circuit 141 in FIG. 10 in that a resistance element 191 and a switch circuit SW31 are added. In FIG. 13, portions corresponding to those in FIG. 10 are denoted by the same reference numerals, and detailed description thereof is omitted.

  Resistance element 191 and switch circuit SW31 are connected in series between nodes N2 and N6. Resistance element 192 and switch circuit SW32 are connected in series between nodes N3 and N6. For these switch circuits SW31 and SW32, for example, N-channel MOS transistors or jumper switches are used. By arbitrarily turning on / off these switch circuits SW31 and SW32 with an external control signal, the ratio between the resistance value between the nodes N1 and N2 and the resistance value between the nodes N2 and N6, and between the nodes N1 and N3 The ratio between the resistance value and the resistance value between nodes N3 and N6 can be changed. In this case, as described with reference to FIG. 7 in the second embodiment, a state in which ground fault detection is impossible can be avoided, and a ground fault can be reliably detected.

  FIG. 14 is a diagram showing the relationship between the positive side deviation reference value and the negative side deviation reference value set in the sixth embodiment and the measured voltage value. Referring to FIG. 14, the solid line corresponds to the case where both switch circuits SW31 and SW32 are in the off state, and the dotted line corresponds to the case where both switch circuits SW31 and SW32 are in the on state. Such a relationship between the deviation reference value and the measured voltage value may be programmed in advance in, for example, a microcomputer provided in the control unit 26.

  When switch circuits SW31 and SW32 are switched from the off state to the on state, both the resistance value between nodes N2 and N6 and the resistance value between nodes N3 and N6 are reduced. Therefore, the ratio between the resistance value between the nodes N1 and N2 and the resistance value between the nodes N2 and N6 and the ratio between the resistance value between the nodes N1 and N3 and the resistance value between the nodes N3 and N6 change. Therefore, the amount of change in the potential of the output node N3 when a ground fault occurs changes. For this reason, the positive side deviation reference value and the negative side deviation reference value corresponding to each of the OFF state and the ON state of the switch circuits SW31 and SW32 are set. Thereby, the difference in the ground fault detection sensitivity between the OFF state and the ON state of the switch circuits SW31 and SW32 is corrected, and the ground fault detection sensitivity is equalized.

  As described above, in the sixth embodiment, the positive side deviation reference value and the negative side deviation reference value are set corresponding to each of the OFF state and the ON state of the switch circuits SW31 and SW32. Thereby, further equalization of ground fault detection sensitivity is achieved.

  Although not illustrated, a configuration in which a resistance element and a switch circuit are added may be used as described with reference to FIG. 7 in the modification of the second embodiment. In this case, similar operations and effects are established.

  As described above, the method of setting the positive side deviation reference value and the negative side deviation reference value corresponding to each of the OFF state and the ON state of the switch circuit in the control unit 26 is the same as that of the second embodiment and the second embodiment. The present invention is also applicable to the ground fault detection circuits 81 and 101 described in the modified example. In this case, the same effect can be obtained.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a circuit block diagram which shows schematic structure of the solar energy power generation system using the power supply device by Embodiment 1 of this invention. FIG. 2 is a circuit diagram showing in detail a configuration of a ground fault detection circuit shown in FIG. 1. It is a circuit diagram for demonstrating the reason formula (5) is materialized. FIG. 4 is an equivalent circuit diagram obtained by simplifying the circuit diagram shown in FIG. 3. It is a circuit block diagram which shows a structure in case the power supply device comprised with an inverter apparatus supplies electric power only to load. It is a block diagram which shows schematic structure of the solar energy power generation system using the power supply device by the modification of Embodiment 1 of this invention. It is a circuit diagram which shows in detail the structure of the ground fault detection circuit by Embodiment 2 of this invention. It is a circuit diagram which shows in detail the structure of the ground fault detection circuit by the example of a change of Embodiment 2 of this invention. It is a circuit block diagram which shows schematic structure of the solar energy power generation system using the power supply device by Embodiment 3 of this invention. It is a circuit diagram which shows in detail the structure of the ground fault detection circuit 141 by Embodiment 4 of this invention. It is a circuit block diagram which shows schematic structure of the solar energy power generation system using the power supply device by Embodiment 5 of this invention. It is a figure which shows the relationship between the positive side deviation reference value and negative side deviation reference value which are set in this Embodiment 5, and a measured voltage value. It is a circuit diagram which shows in detail the structure of the ground fault detection circuit 181 by Embodiment 6 of this invention. It is a figure which shows the relationship between the positive side deviation reference value and negative side deviation reference value which are set in this Embodiment 6, and a measured voltage value. It is a circuit block diagram which shows schematic structure of the solar energy power generation system using the conventional power supply device. FIG. 16 is a circuit diagram showing in detail a configuration of a ground fault detection circuit 225 shown in FIG. 15.

Explanation of symbols

  1,201 DC power supply unit, 2,71,202 grid-connected inverter device, 3,203 commercial power system, 11-13, 211-213 solar cell module, 4 inverter device, 5 load, 21,24, 221,224 Switching unit, 22, 222 DC / DC converter unit, 23, 223 inverter circuit, 25, 161 ground fault detection unit, 26, 228 control unit, 27, 229 display unit, 31-33, 231-233 DC / DC converter, 41-43 Resistor, 44, 81, 101, 131, 141, 181, 2525-227 Ground fault detection circuit, 51-57, 61, 91-93, 111-113, 151, 152, 191, 192, 241 246 Resistance element, 162 Maximum voltage detection unit, 58, 59, 172 to 174 Diode, 132, 133 selection unit 171 voltage detection circuit, 247 current detector, 248, 249 unidirectional element.

Claims (20)

A power supply device that converts DC power generated by a plurality of DC power generators into AC power and supplies the AC power to a load,
A plurality of DC / DC converters provided corresponding to the plurality of DC power generators, each of which converts the output voltage of the corresponding DC power generator into a predetermined voltage and outputs the voltage to the first node;
An inverter that converts the DC power supplied to the first node into AC power and supplies it to the commercial power system, and is provided corresponding to each of the plurality of DC power generators, each one electrode corresponding to A plurality of resistors connected to the positive terminal of the DC power generator, each other electrode connected to each other;
The first electrode connected to the other electrode of the plurality of resistors and the negative terminal of the plurality of DC power generators, detects a ground fault of a charging unit by the plurality of DC power generators, and outputs a ground fault detection signal. A power supply device comprising a ground fault detection circuit. A power supply device that converts DC power generated by a plurality of DC power generators into AC power and supplies the AC power to a commercial power system,
A plurality of DC / DC converters provided corresponding to the plurality of DC power generators, each of which converts the output voltage of the corresponding DC power generator into a predetermined voltage and outputs the voltage to the first node;
An inverter that converts the DC power supplied to the first node into AC power and supplies it to the commercial power system, and is provided corresponding to each of the plurality of DC power generators, each one electrode corresponding to A plurality of resistors connected to the positive terminal of the DC power generator, each other electrode connected to each other;
The first electrode connected to the other electrode of the plurality of resistors and the negative terminal of the plurality of DC power generators, detects a ground fault of a charging unit by the plurality of DC power generators, and outputs a ground fault detection signal. A power supply device comprising a ground fault detection circuit. The first ground fault detection circuit includes:
The first input node connected in series between the first input node commonly connected to the other electrode of the plurality of resistors and the second input node commonly connected to the negative terminals of the plurality of DC power generators. And a second resistive element, and a first voltage dividing circuit in which an output node between the first and second resistive elements is connected to a reference potential line, and the first input node and the second resistive element In the normal state, the ground fault detection signal of the reference potential is output from the output node between the third and fourth resistance elements. In response to the fact that the voltage across the first resistance element is greater than the voltage across the second resistance element by a predetermined level or more due to a ground fault in the charging section of the plurality of DC power generators. The output between the third and fourth resistance elements The ground fault detection signal having a potential higher than the reference potential is output from a node, and the voltage across the second resistance element is changed to the first resistance element due to the ground fault of the charging unit by the plurality of DC power generators. The ground fault detection signal having a potential lower than the reference potential is output from the output node between the third and fourth resistance elements in response to the voltage exceeding the predetermined voltage being greater than a predetermined level. The power supply device according to claim 1, further comprising: a voltage dividing circuit. The first ground fault detection circuit includes:
The first input node connected in series between the first input node commonly connected to the other electrode of the plurality of resistors and the second input node commonly connected to the negative terminals of the plurality of DC power generators. A first voltage dividing circuit including an output node between the first and second resistance elements connected to a reference potential line;
An output node between the third and fourth resistance elements in a normal state, including third and fourth resistance elements connected in series between the first input node and the second input node; From the output terminal of the plurality of DC power generators, the voltage between the terminals of the first resistance element is a predetermined level higher than the voltage between the terminals of the second resistance element. A second voltage dividing circuit that outputs a potential higher than the reference potential from an output node between the third and fourth resistance elements,
Output nodes between the fifth and sixth resistance elements are normally included, including fifth and sixth resistance elements connected in series between the first input node and the second input node. Output a potential equal to or higher than the reference potential, and the voltage across the second resistance element is a predetermined level higher than the voltage across the first resistance element due to the ground fault of the output portions of the plurality of DC power generator When the voltage becomes larger than this, a third voltage dividing circuit that outputs a potential lower than the reference potential from an output node between the fifth and sixth resistance elements, and, in normal times, the ground of the reference potential. A fault detection signal is output, and the reference potential and the potential of the output node of the second voltage dividing circuit are compared, and the potential of the output node of the second voltage dividing circuit is made higher than the reference potential. Depending on the situation, the ground fault is higher than the reference potential. A detection signal is output, and the potential of the output node of the third voltage dividing circuit is made lower than the reference potential by comparing the reference potential with the potential of the output node of the third voltage dividing circuit. The power supply device according to claim 1, further comprising a comparison circuit that outputs the ground fault detection signal having a potential lower than the reference potential.   5. The power supply device according to claim 3, wherein a resistance value of at least one of the plurality of resistance elements included in the first ground fault detection circuit is variable. The at least one resistance element is:
The first and second sub-resistance elements whose one electrodes are connected to each other, and connected between the other electrode of the first sub-resistance element and the other electrode of the second sub-resistance element, and from the outside The power supply device according to claim 5, further comprising: a first switch circuit that is turned on / off in response to the control signal. The at least one resistance element is:
First and second sub-resistance elements connected in series, and a first sub-resistance element connected between one electrode and the other electrode of the second sub-resistance element and turned on / off in response to an external control signal The power supply device according to claim 5, further comprising:   Further, when the potential of the ground fault detection signal is within a predetermined range, it is determined that a ground fault has not occurred in the charging unit by the plurality of DC power generators, and the potential of the ground fault detection signal is determined. 8 is provided with a control unit that determines that a ground fault has occurred in the charging unit of the plurality of DC power generators when the voltage is not within a predetermined range. The power supply described.   The control unit electrically cuts off a path between the plurality of DC power generators and the commercial power system when it is determined that a ground fault has occurred in the charging unit by the plurality of DC power generators. The power supply device according to claim 8.   The power supply device according to claim 8 or 9, wherein the predetermined range is substantially a reference potential.   The predetermined range is a range between a positive deviation reference value higher than the reference potential and a negative deviation reference value lower than the reference potential. Power supply. Furthermore, a maximum voltage detector that measures the highest output voltage among the output voltages of each of the plurality of DC power generators,
The power supply device according to claim 11, wherein the control unit sets the positive deviation reference value and the negative deviation reference value according to the voltage measured by the maximum voltage detection unit.   The control unit changes the setting of the positive-side deviation reference value and the negative-side deviation reference value according to the on / off state of the first switch circuit of the at least one resistance element. The power supply device according to claim 12.   The first ground fault detection circuit is further connected between an output node of the first voltage dividing circuit and the reference potential line, and performs a ground fault detection operation in response to an external control signal. If the output node of the first voltage dividing circuit is connected to the reference potential line, the output node of the first voltage dividing circuit is connected to the reference potential line. 14. The power supply device according to claim 3, further comprising a second switch circuit that electrically disconnects the switch. Further, connected to the other electrode of the plurality of resistors and the negative terminal of the plurality of DC power generators, detects a ground fault of the charging unit by the plurality of DC power generators, and outputs a ground fault detection signal. In response to a second ground fault detection circuit having the same configuration as the first ground fault detection circuit and an external control signal, an output is output from either the first ground fault detection circuit or the second ground fault detection circuit. A selection circuit that selectively gives a ground fault detection signal to the control unit,
The resistance value of at least one resistance element among the plurality of resistance elements included in the second ground fault detection circuit is different from the resistance value of the corresponding resistance element of the first ground fault detection circuit. The power supply device according to claim 14.   Even when a ground fault occurs at the positive terminal of any DC power generator of the plurality of DC power generators, the potential of the ground fault detection signal is set to a potential lower than the reference potential. The power supply apparatus according to claim 3 or 4, wherein an output voltage of each of the plurality of DC power generators is predetermined.   The power supply device according to any one of claims 1 to 16, wherein each of the plurality of DC power generators is a solar battery.   The power supply apparatus according to any one of claims 1 to 17, wherein the DC / DC converter includes an insulating transformer that performs a transformation operation in a state where an input terminal and an output terminal thereof are insulated.   The power supply device according to claim 6, wherein the first switch circuit includes a field effect transistor.   The power supply device according to claim 6, wherein the first switch circuit is a jumper switch.

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