WO2015015836A1 - Solar power generation system - Google Patents

Abstract

A ground-fault detection device in one mode of this invention detects ground faults in a power generation unit in a solar power generation system provided with the following: said power generation unit, which comprises one or more solar-cell modules that utilize sunlight to generate electrical power; and a load device that, electrically isolated from either the power generation unit or the ground, consumes or converts the electrical power generated by the power generation unit. The aforementioned ground-fault detection device is characterized by the provision of the following: a first grounding path that connects to a given part of the power generation unit and either makes the ground potential of every part of the power generation unit greater than or equal to zero or makes the ground potential of every part of the power generation unit less than or equal to zero; a second grounding path that brings the ground potential of the power generation unit to a potential that is different from the ground potential that results when the first grounding path is connected; a potential control unit that controls the ground potential of the power generation unit by switching between connecting the first grounding path to the power generation unit and connecting the second grounding path to the power generation unit; and a ground-fault detection unit that measures the current that flows through the first grounding path when same is connected to the power generation unit by the potential control unit, measures the current that flows through the second grounding path when same is connected to the power generation unit by the potential control unit, and detects ground faults in the power generation unit on the basis of the results of said measurements. This ground-fault detection device is also characterized in that, during normal operation, the potential control unit connects the first grounding path to the power generation unit.

Description

Solar power system

This application claims priority based on JP2013-158871 (application number) filed in Japan on July 31, 2013. The contents described in JP2013-158871 are incorporated into the present application.

One embodiment of the present invention relates to a photovoltaic power generation system and a photovoltaic power generation method, for example, a photovoltaic power generation system and method in which a PID (Potential Induced Degradation) measure is taken.

In a photovoltaic power generation system that generates power using sunlight, generally, a plurality of solar cell modules are connected in series and in parallel, and the generated power that has become a large voltage and a large current is a power conditioner or the like. Are supplied to a commercial power system and the like. In the photovoltaic power generation system, a plurality of solar cell modules are connected in series to form a solar cell string. A plurality of solar cell strings are connected in parallel to form a solar cell array.

Recently, as the voltage generated by the photovoltaic power generation system becomes higher, the performance of the photovoltaic power generation system deteriorates due to the influence of the ground voltage and the power generation amount decreases in such a photovoltaic power generation system. It has become.

13A and 13B are conceptual diagrams for explaining an example of the PID phenomenon. 13A and 13B show one solar cell string 502 as an example of the solar cell array of the photovoltaic power generation system. And in FIG. 13A, the case where a p-type semiconductor is used for the bulk of a solar cell is shown as an example. When the potential in the middle of the solar cell string 502 connected to the load device 510 becomes a ground potential, the performance may be deteriorated at a negative potential rather than the ground potential. On the other hand, FIG. 13B shows an example in which an n-type semiconductor is used for the bulk of the solar cell. When the potential in the middle of the solar cell string 502 connected to the load device 510 becomes a ground potential, the performance may be deteriorated at a positive potential rather than the ground potential.

14A and 14B are conceptual diagrams for explaining an example of a countermeasure technique for the PID phenomenon. As a countermeasure method against the PID phenomenon, it has been considered to take a countermeasure on the solar cell module and the cell itself, but as a reliable technique, it is considered to ground the negative electrode or the positive electrode of the photovoltaic power generation system. ing. In FIG. 14A, the case where a p-type semiconductor is used for the bulk of a solar cell is shown as an example. In such a case, the negative electrode side of the solar cell string 502 is grounded in a state where the solar power generation system is constructed in a system insulated from a commercial power system or the like. As a result, the entire solar cell string 502 can be prevented from having a negative potential with respect to the ground potential. Such measures can avoid the PID phenomenon. In FIG. 14B, the case where an n-type semiconductor is used for the bulk of a solar cell is shown as an example. In such a case, the positive electrode side of the solar cell string 502 is grounded in a state where the solar power generation system is constructed in a system insulated from a commercial power system or the like. Thereby, it can prevent that the solar cell string 502 whole becomes a positive electric potential rather than the electric potential of the earth. Such measures can avoid the PID phenomenon.

However, new problems arise when the system is grounded. That is when a ground fault occurs in the system. If there is an insulation failure in the solar cell array, a ground fault may occur where the electric circuit comes into contact with the outside in an unintended manner. For example, when a person or an object touches a poorly insulated part, or when a poorly insulated part comes into contact with a metal mount or the like. If a ground fault occurs even at one location in the system, the potential of the ground fault location becomes the ground potential, so a closed loop circuit is formed between the ground location for PID countermeasures and the ground fault location, and a large current is externally supplied. May lead to a major accident.

JP 2013-033825 A

FIG. 15 is a conceptual diagram for explaining an example of the ground fault countermeasure of the photovoltaic power generation system in which the PID countermeasure is taken. FIG. 15 shows a case where the negative electrode side of the solar cell string 502 is grounded. FIG. 15 shows a configuration in which an ammeter or / and a fuse are arranged at the ground location 530 for PID countermeasures for ground fault countermeasures. In such a configuration, as shown in FIG. 15, for example, when a ground fault occurs in the middle of the solar cell string 502 or on the positive electrode side, a closed loop circuit is provided between the grounding location 530 for PID countermeasures and the ground fault location 600. As a result, a large current flows to the outside. Therefore, such a current is monitored with an ammeter or / and a fuse, and when a current exceeding a threshold value flows, the photovoltaic power generation system can be urgently stopped as a ground fault. However, such a configuration creates a blind spot for ground fault detection as described below.

FIG. 16 is a conceptual diagram for explaining an example of a blind spot for detecting a ground fault in a photovoltaic power generation system in which a PID countermeasure is taken. As shown in FIG. 16, for example, first, when the first ground fault occurs on the negative electrode side of the solar cell string 502, no potential difference occurs between the grounding location 530 for PID countermeasures and the ground fault location 602. Therefore, it is difficult to detect such a first ground fault with an ammeter or / and a fuse arranged at the grounding location 530 for PID countermeasures. Therefore, the solar power generation system continues normal operation. In this state, for example, when a second ground fault occurs in the middle of the solar cell string 502 or on the positive electrode side, the ground fault location 602 of the first ground fault accident and the ground fault location 600 of the second ground fault accident. When the insulation resistance at the first ground fault point is smaller than the resistance value of the ground wire for PID countermeasures, a large current flows to the outside. However, since the ground location 530 for PID countermeasures is located outside the closed loop circuit, the ammeter or / and the fuse disposed at the ground location 530 for PID countermeasures cannot detect such a second ground fault. Have difficulty. As a result, it will lead to a big accident that a large current flows outside without detecting a ground fault. As described above, the configuration shown in FIG. 16 forms a blind spot (detection dead zone) where ground fault detection is difficult.

Accordingly, one aspect of the present invention provides a photovoltaic power generation system that can overcome the above-described problems and eliminate a blind spot where ground fault detection is difficult while grounding for PID countermeasures is performed. Objective.

The ground fault detection apparatus according to one aspect of the present invention includes:
A power generation unit configured using one or more solar cell modules that generate power using sunlight, and a load device that consumes or converts the power generated by the power generation unit while being insulated from the power generation unit or the ground. In the photovoltaic power generation system comprising, a ground fault detection device for detecting a ground fault in the power generation unit,
A first grounding circuit connected to a given point of the power generation unit to make the ground potential of all points of the power generation unit greater than or less than zero;
A second grounding circuit for setting the ground potential of the power generation unit to a potential different from that when the first grounding circuit is connected;
A potential control unit that controls the ground potential of the power generation unit by switching between the first grounding circuit and the second grounding circuit and connecting to the power generation unit;
The potential control unit measures a measurement value based on the current flowing through the first grounding circuit connected to the power generation unit and a measurement value based on the current flowing through the second grounding circuit connected to the power generation unit, and based on the measurement result A ground fault detection unit that detects a ground fault of the power generation unit,
The potential control unit connects the first grounding circuit to the power generation unit during normal operation.

The ground fault detection apparatus according to another aspect of the present invention includes:
A power generation unit configured using one or more solar cell modules that generate power using sunlight, and a load device that consumes or converts the power generated by the power generation unit while being insulated from the power generation unit or the ground. In the photovoltaic power generation system comprising, a ground fault detection device for detecting a ground fault in the power generation unit,
One side is connected to the ground, and the other side is connected to the positive electrode or negative electrode of the power generation unit,
A ground fault detection unit that measures a measurement value based on a current flowing through the grounding circuit and detects a ground fault based on the measurement result; and
The ground circuit has a direct current power source and is characterized in that the ground potential at all locations of the power generation unit is positive or negative.

The ground fault detection apparatus according to another aspect of the present invention includes:
A power generation unit configured using one or more solar cell modules that generate power using sunlight, and a load device that consumes or converts the power generated by the power generation unit while being insulated from the power generation unit or the ground. In the photovoltaic power generation system comprising, a ground fault detection device for detecting a ground fault in the power generation unit,
One side is connected to the ground, and the other side is connected to the positive electrode or negative electrode of the power generation unit,
A ground fault detection unit that measures a measurement value based on a current flowing through the grounding circuit and detects a ground fault based on the measurement result; and
The grounding electric circuit has an AC power supply, and is characterized in that the ground potential at all locations of the power generation unit is averaged over zero or less than zero.

The photovoltaic power generation method of one embodiment of the present invention includes:
A power generation unit configured using one or more solar cell modules that generate power using sunlight, and a load device that consumes or converts the power generated by the power generation unit while being insulated from the power generation unit or the ground. In the state where the power generation unit and the load device are connected using the solar power generation system including the above, and the ground potential of all locations of the power generation unit is set to zero or more or zero or less using the first ground circuit. While performing normal operation of photovoltaic power generation, measure the measured value based on the current flowing through the first grounding circuit,
Using the second grounding circuit, the measured value based on the current flowing through the second grounding circuit is measured in a state where the ground potential of the power generation unit is set to a potential different from that when the first grounding circuit is connected to the power generation unit ,
A ground fault of the power generation unit is detected based on a measurement value based on a current flowing through a first grounding circuit connected to the power generation unit and a measurement value based on a current flowing through a second grounding circuit connected to the power generation unit. And

The photovoltaic power generation method according to another aspect of the present invention includes:
A power generation unit configured using one or more solar cell modules that generate power using sunlight, and a load device that consumes or converts the power generated by the power generation unit while being insulated from the power generation unit or the ground. In the state where the power generation unit and the load device are connected using the solar power generation system including the above, and the ground potential of all locations of the power generation unit is set to zero or more or zero or less using the first ground circuit. We perform normal operation of photovoltaic power generation,
With the power generation unit and the load device disconnected, connect the first grounding circuit to the power generation unit, measure the measured value based on the current flowing through the first grounding circuit,
In a state where the power generation unit and the load device are disconnected, the second grounding circuit is connected to the power generation unit, and the ground potential of the power generation unit is set to a different potential from that when the first grounding circuit is connected to the power generation unit. Measure the measured value based on the current flowing through the second grounding circuit,
A ground fault of the power generation unit is detected based on a measurement value based on a current flowing through a first grounding circuit connected to the power generation unit and a measurement value based on a current flowing through a second grounding circuit connected to the power generation unit. And

According to one aspect of the present invention, it is possible to eliminate a blind spot where ground fault detection is difficult while grounding for PID countermeasures is performed.

1 is a configuration diagram showing a configuration of a photovoltaic power generation system in Embodiment 1. FIG. It is a block diagram which shows the structure of the solar energy power generation system in Embodiment 2. FIG. 10 is a configuration diagram showing a configuration of a photovoltaic power generation system in a third embodiment. It is a block diagram which shows the structure of the solar energy power generation system in Embodiment 4. FIG. 10 is a configuration diagram showing a configuration of a photovoltaic power generation system in a fifth embodiment. FIG. 10 is a configuration diagram showing a configuration of a solar power generation system in a sixth embodiment. FIG. 10 is a configuration diagram illustrating a configuration of a solar power generation system in a seventh embodiment. FIG. 20 is a diagram for describing a ground fault detection operation in a seventh embodiment. FIG. 10 is a configuration diagram showing a configuration of a photovoltaic power generation system in an eighth embodiment. FIG. 20 is a diagram for describing a ground fault detection operation in an eighth embodiment. FIG. 10 is a configuration diagram illustrating a configuration of a solar power generation system in a ninth embodiment. 209 is a diagram for describing a ground fault detection operation in a ninth embodiment. FIG. It is a conceptual diagram for demonstrating an example of a PID phenomenon. It is a conceptual diagram for demonstrating an example of a PID phenomenon. It is a conceptual diagram for demonstrating an example of the countermeasure method to a PID phenomenon. It is a conceptual diagram for demonstrating an example of the countermeasure method to a PID phenomenon. It is a conceptual diagram for demonstrating an example of the ground fault countermeasure of the solar power generation system in which the PID countermeasure was taken. It is a conceptual diagram for demonstrating an example of the blind spot of the ground fault detection of the photovoltaic power generation system with which the PID countermeasure was taken.

FIG. 1 is a configuration diagram showing the configuration of the photovoltaic power generation system according to the first embodiment. In FIG. 1, a solar power generation system 100 is a system that generates power using solar energy. The solar power generation system 100 includes a solar cell array 300 (an example of a power generation unit) and a load device 400. A plurality of solar cell modules 10a to 10e (an example of a power generation unit) electrically connected in series constitute a solar cell string 12 (an example of a power generation unit). Each solar cell module 10 is a module that uses sunlight to convert solar energy into electrical energy and output it as DC power. The solar cell array 300 includes a plurality of solar cell strings 12a to 12c arranged in parallel. The plurality of solar cell strings 12a to 12c are electrically connected in parallel inside the solar cell array 300. In the example of FIG. 1, each solar cell string 12 is constituted by five solar cell modules 10a to 10e connected in series, but is not limited thereto. The number in series may be two, three, four, or six or more. What is necessary is just to set suitably. Similarly, the solar cell array 300 is configured by three solar cell strings 12a to 12c connected in parallel, but is not limited thereto. The number in parallel may be one, two, or four or more. What is necessary is just to set suitably. Thus, the power generation unit in the first embodiment is configured using one or more solar cell modules that generate power using sunlight.

In the solar cell array 300, the positive electrode (+) and the negative electrode (-) of each solar cell string 12a-c are connected to the solar cell strings 12a-c from the system or connected to the system, respectively. Is connected. In the example of FIG. 1, one end of the switch device 102a is connected to the negative electrode wiring of the solar cell string 12a, and one end of the switch device 102b is connected to the positive electrode wiring. Further, a backflow prevention diode 20a is connected to the other side of both ends of the switch device 102b. Similarly, one end of the switch device 102c is connected to the negative electrode wiring of the solar cell string 12b, and one end of the switch device 102d is connected to the positive electrode wiring. Further, a backflow prevention diode 20b is connected to the other side of both ends of the switch device 102d. Similarly, one end of the switch device 102e is connected to the negative electrode wiring of the solar cell string 12c, and one end of the switch device 102f is connected to the positive electrode wiring. A backflow prevention diode 20c is connected to the other side of both ends of the switch device 102f. Each of the backflow prevention diodes 20a to 20c is arranged such that the current flowing from the corresponding solar cell string 12a to 12c flows in the forward direction. The number of switch devices 102 that can be arranged on both poles of the solar cell string 12 is arranged. Each switch device 102 is preferably a switch capable of automatically controlling the opening / closing operation electrically. In this case, when a ground fault is detected in the solar cell, the system can be disconnected up to the string unit and stopped. Although a mechanical switch may be used, it is more preferable to use, for example, a semiconductor switch. For example, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is preferably used.

In the example of FIG. 1, the backflow prevention diode 20 is disposed only on the positive electrode side of each solar cell string 12, but is not limited thereto. The backflow prevention diode 20 may be disposed only on the negative electrode side of each solar cell string 12. Or the backflow prevention diode 20 may be arrange | positioned at both the positive electrode of each solar cell string 12, and the negative electrode, respectively. In any case, each backflow prevention diode 20 is arranged such that the direction in which the current supplied from the corresponding solar cell string 12 flows is the forward direction.

In the example of FIG. 1, each of the solar cell strings 12a to 12c is connected in parallel on the other side of the switch device 102, one of which is connected to the negative electrode of the corresponding solar cell string 12, and one of the corresponding solar cell strings 12 The other side of the backflow prevention diode 20 connected to the positive electrode side is connected in parallel. As a result, the plurality of solar cell strings 12a to 12c are connected in parallel to form the solar cell array 300. A fuse can be used instead of the backflow prevention diode. In this case, although a reverse current cannot be prevented completely, a solar cell array capable of preventing an excessive reverse current can be configured.

The negative electrode wiring (negative electrode bus) of the solar cell array 300 is connected to a switch 402 such as a circuit breaker or disconnector, and the positive electrode wiring (positive electrode bus) is connected to a switch 404 such as a circuit breaker or disconnector. The switches 402 and 404 are connected to the load device 400, respectively. As described above, the positive electrode (+) side of the solar cell array 300 is connected to the load device 400 via the switch 404, and the negative electrode (−) side is connected to the load device 400 via the switch 402. The load device 400 has an insulating transformer inside or on the output side, and prevents the solar cell array from being electrically connected to the ground. Examples of the load device 400 include a power conditioner. The DC power supplied from the solar cell array 300 to the load device 400 is converted into, for example, three-phase AC power in the load device 400 and supplied to, for example, a commercial power system. As described above, the load device 400 consumes or converts the power generated by the solar cell array 300 while being insulated from the solar cell array 300 (power generation unit) or the ground.

Moreover, in Embodiment 1, the ground fault detection apparatus 36 which detects the ground fault in the solar cell array 300 (power generation part) is further provided. The ground fault detection device 36 includes a changeover switch 80 (an example of a potential control unit), a ground fault detection unit (a resistor 84 and a voltage monitoring unit 86), and a ground line 40. In FIG. 1, the first terminal on one side of the changeover switch 80 branches off from the negative electrode wiring of the solar cell array 300 (“negative electrode bus” connecting the negative electrode of the solar cell array 300 and the negative electrode of the load device 400). Wiring is connected. The second terminal on one side of the changeover switch 80 is connected to a wiring branched from the positive electrode wiring of the solar cell array 300 (“positive electrode bus” connecting the positive electrode of the solar cell array 300 and the positive electrode of the load device 400). The The changeover switch 80 is arranged to be able to switch between the negative electrode wiring (negative electrode bus) of the solar cell array 300 and the positive electrode wiring (positive electrode bus) of the solar cell array 300. One end of the resistor 84 is connected to the other terminal of the changeover switch 80. The other end of the resistor 84 is connected to the ground line 40. Then, the ground line 40 is grounded at the ground point 41.
In FIG. 1, when the changeover switch 80 is connected to the negative electrode wiring side (first terminal) of the solar cell array 300, the solar cell array 300 includes a negative electrode side connection point 50, a changeover switch 80, a resistor 84, It will be in the state connected to the earthing electric circuit (1st earthing electric circuit) which consists of the earthing | grounding wire 40. FIG. On the other hand, when the changeover switch 80 is connected to the positive electrode wiring side (second terminal) of the solar cell array 300, the solar cell array 300 has the positive electrode side connection point 51, the changeover switch 80, the resistor 84, and the ground line. 40 is connected to a grounding circuit (second grounding circuit) consisting of 40. As described above, the changeover switch 80 switches and connects the two types of grounding electric circuits to the solar cell array 300. As described above, the first grounding electric circuit is configured to be connectable to one pole of the power generation unit, and the second grounding electric circuit is configured to be connectable to the other pole of the power generation unit.

Further, the voltage monitoring unit 86 monitors the potential difference (voltage) at both ends of the resistor 84. As the voltage monitoring unit 86, for example, a voltmeter electrically connected in parallel with the resistor 84 can be used. In FIG. 1, a three-way switch is illustrated as the changeover switch 80, but the switch is not limited to this, and any switch can be used as long as it can switch between a state where the negative electrode bus is grounded and a state where the positive electrode bus is grounded. Alternatively, a circuit configuration may be used. The changeover switch 80 uses a switch that can automatically electrically control the opening / closing operation. Although a mechanical switch may be used, it is more preferable to use, for example, a semiconductor switch. For example, it is preferable to use a MOSFET.

The solar power generation system 100 as described above is operated as follows as a solar power generation method. During normal operation, the solar cell array 300 and the load device 400 are connected, and the ground potential at all locations of the solar cell array 300 is controlled to zero or more or less than zero using the ground wire 40. Perform normal operation of photovoltaic power generation. Specifically, it operates as follows. Each switch device 102 and switches 402 and 404 that are driven by control from a control system (not shown) are both ON (closed), and the changeover switch 80 is connected to the negative electrode wiring (negative electrode bus) side of the solar cell array 300. Normal operation is performed in the connected state. That is, during normal operation, the first grounding circuit is connected to the solar cell array 300 as a countermeasure against PID (Potential Induced Degradation) (that is, the negative electrode of the solar cell array 300 is grounded via the grounding wire 40 and the resistor 84). In the example of FIG. 1, a solar cell using a p-type semiconductor for the bulk of the solar cell or a transparent conductive film is shown as an example. Therefore, the negative electrode wiring is grounded. When an n-type semiconductor is used for the bulk of the solar cell, it goes without saying that the positive electrode wiring (positive electrode bus) is grounded via the resistor 84. In this way, the negative electrode of the photovoltaic power generation system 100 is grounded via the resistor 84. In this way, during the normal operation of the system, the changeover switch 80 (potential control unit) uses the ground wire 40 to connect the ground potential at a predetermined point of the solar cell array 300 to the positive electrode (the n-type semiconductor is placed in the bulk of the solar cell). When used, it is controlled to the potential of the negative electrode). Thereby, the negative electrode of each solar cell string 12a-c can be controlled to the same potential as the ground, and the PID phenomenon can be avoided. As described above, the first grounding electric circuit is connected to a given location of the power generation unit, and makes the ground potential at all locations of the power generation unit to be greater than or equal to zero.

The voltage monitoring unit 86 detects a ground fault of the solar cell array 300 during normal operation of the solar power generation system 100. Specifically, voltage monitoring is performed in a state in which the negative electrode wiring (negative electrode bus) side of the solar cell array 300 is connected to the resistor 84 by the changeover switch 80 (that is, the first grounding circuit is connected to the solar cell array 300). The unit 86 measures the voltage V <b> 1 across the resistor 84. That is, the voltage monitoring unit 86 measures the voltage V1 across the resistor 84 as a measurement value based on the current flowing through the first grounding circuit connected to the solar cell array 300. When the measured voltage V1 exceeds a preset threshold value, it is determined that there is a ground fault by a control system (not shown). And the solar power generation system 100 can be stopped urgently. When a ground fault occurs in the middle of any solar cell string 12 or on the positive electrode side, a closed circuit is formed via the ground fault location and the first grounding circuit, and the sun existing between the ground fault location and the negative electrode Since a voltage is generated in the resistor 84 when a current flows through the ground circuit 40 due to the electromotive force of the battery, a ground fault can be determined based on the voltage V1. However, in such a configuration, when a ground fault occurs on the negative electrode side of any of the solar battery strings 12, there is no electromotive force in the closed circuit formed via the grounding location and the first grounding circuit, Since no voltage is generated in the resistor 84, it is difficult to detect a ground fault. Therefore, the blind spot of the ground fault detection that normal operation is continued as it is is generated.

Therefore, in the first embodiment, the second grounding electrical circuit is connected to the solar cell array 300 by the changeover switch 80 and the ground fault detection device 36 performs ground fault detection periodically. The second grounding circuit sets the ground potential of the power generation unit to a potential different from that when the first grounding circuit is connected. For example, the ground fault is detected every time the photovoltaic power generation system 100 is started or periodically during operation. For example, ground fault detection is performed at intervals of 1 to 2 hours. In this state, the voltage monitoring unit 86 measures the voltage V <b> 2 applied across the resistor 84. That is, the voltage monitoring unit 86 measures the voltage V2 across the resistor 84 as a measurement value based on the current flowing through the second grounding circuit connected to the solar cell array 300. When the measured voltage V2 exceeds a preset threshold value, it is determined that there is a ground fault by a control system (not shown). And the solar power generation system 100 can be stopped urgently. When a ground fault occurs in the middle of any one of the solar cell strings 12 or on the negative electrode side, a potential difference is generated between the positive electrode wiring (positive electrode bus) of the solar cell array 300 and the ground, so that the ground fault can be determined based on the voltage V2. That is, by switching the changeover switch 80, it can be compensated that the negative electrode is a blind spot for ground fault detection. In other words, by switching from the first grounding electrical circuit to the second grounding electrical circuit with the changeover switch 80, it is possible to detect a ground fault at a spot that is a blind spot in the first grounding electrical circuit. As described above, the ground fault detection unit uses the changeover switch 80 (potential control unit) to obtain the measurement value based on the current flowing through the first grounding circuit connected to the power generation unit and the second grounding circuit connected to the power generation unit. The measured value based on the flowing current is measured, and the ground fault of the power generation unit is detected based on the measurement result. In detecting the ground fault, the ground fault of the solar cell array 300 is detected in a state where the connection between the solar cell array 300 and the load device 400 is disconnected by the switches 402 and 404 driven by control from a control system (not shown). You may do it. Thereby, the influence from the load apparatus 400 can be excluded.

Thus, the changeover switch 80 (potential control unit) controls the ground potential of the power generation unit by switching between the first grounding circuit and the second grounding circuit and connecting to the power generation unit. When detecting a ground fault, the ground fault detection device 36 detects a ground fault of the solar cell array 300 in each of two or more different ground potential states controlled by the changeover switch 80 (potential control unit). In other words, in a state where the negative electrode wiring (negative electrode bus) side (negative electrode side connection point 50) side of the solar cell array 300 is connected to the resistor 84 by the changeover switch 80 (a state where the solar cell array 300 is connected to the first grounding electric circuit). When connected to 40, the potential of the negative electrode of the solar cell array 300 becomes the potential of the ground (ground). Therefore, the ground potential of the positive electrode of solar cell array 300 (the positive electrode of each solar cell string 12a to 12c) is controlled to a positive potential. The ground potential in the middle of each solar cell string 12a-c is also positive. On the other hand, in the state where the positive electrode (positive electrode bus) side (positive electrode connection point 51) side of the solar cell array 300 is connected to the resistor 84 by the changeover switch 80 (connected to the second grounding circuit), By being connected, the potential of the positive electrode of the solar cell array 300 is controlled to the potential of the ground (ground). Therefore, the ground potential of the negative electrode of the solar cell array 300 (the negative electrode of each of the solar cell strings 12a to 12c) is a negative potential. Further, the ground potential in the middle of each of the solar cell strings 12a to 12c is also negative. Thus, the changeover switch 80 (an example of a potential control unit) can intentionally control the ground potential of the solar cell array 300.

As described above, in the example of the ground fault detection device shown in FIG. 1, it is possible to detect such a ground fault even if a ground fault (insulation failure or the like) occurs in any part of the solar cell array 300. Therefore, ground fault detection becomes possible at the stage when the first ground fault accident (first ground fault accident) occurs, and the blind spot location for ground fault detection can be eliminated.

As described above, in the first embodiment, the same grounding wire 40 is used, on the one hand, for PID countermeasures, and on the other hand, for ground fault detection excluding blind spots. During normal operation, since the ground potential of the negative electrode of the solar cell array 300 becomes the ground potential by the changeover switch 80 (potential control unit), the two different values controlled by the changeover switch 80 (potential control unit). One of the above ground potential states is set.

In the example described above, the ground fault determination is simply performed by comparing the voltage of the resistor 84 with the threshold value, but the present invention is not limited to this. For example, in a state where the negative electrode wiring (negative electrode bus) side of the solar cell array 300 is connected to the resistor 84 by the changeover switch 80, the voltage monitoring unit 86 measures the voltage V1 applied to both ends of the resistor 84. Next, in a state where the positive electrode wiring (positive electrode bus) side of the solar cell array 300 is connected to the resistor 84 by the changeover switch 80, the voltage monitoring unit 86 measures the voltage Va applied to both ends of the resistor 84. Further, the voltage V0 between the negative electrode and the positive electrode of the solar cell array 300 is measured by a device (not shown). Then, the insulation resistance is calculated using the resistance value R of the resistor 84 and the measured voltages V1, Va, V0. If the obtained insulation resistance is less than a preset threshold value, it is determined that there is a ground fault. Is also suitable.
In the first embodiment, the case where the voltage across the resistor 84 is measured as the measurement value based on the current flowing through the first grounding circuit and the measurement value based on the current flowing through the second grounding circuit has been described. However, the present invention is not limited to this. It is not necessary to measure the current in each state of the state in which the first grounding electric circuit is connected to the solar cell array 300 and the state in which the second grounding electric circuit is connected to the solar cell array 300, and compare it with the threshold value. It is good also as a structure which performs a ground fault determination.

In the above-described example, the case where the ground fault detection is performed in units of the solar cell array 300 is shown, but the present invention is not limited to this. For example, the ground fault detection may be performed in units of 12 solar cell strings. In such a case, the two switch devices 102 connected to the solar cell string 12 to be detected are turned on (closed), and then the two switch devices 102 of the remaining solar cell strings 12 are turned off (open). In the state, the above-described ground fault detection may be performed. Thereby, ground fault detection can be performed for the solar cell string 12 to be detected while only the solar cell string 12 to be detected is normally operated.

As described above, according to the first embodiment, it is possible to eliminate a blind spot where it is difficult to detect a ground fault while performing grounding for PID countermeasures.

FIG. 2 is a configuration diagram showing the configuration of the photovoltaic power generation system according to the second embodiment. 2, in the photovoltaic power generation system 100 according to the second embodiment, a DC power supply 91 is further arranged in the configuration of FIG. 1 as one of the internal configurations of the ground fault detection device 36. In other words, the ground fault detection device 36 includes a changeover switch 80 (an example of a potential control unit), a ground fault detection unit (a resistor 84 and a voltage monitoring unit 86), a DC power supply 91, and a ground line 40. One end of the resistor 84 is connected to the changeover switch 80 and the positive electrode of the DC power supply 91, the other is connected to the ground line 40, and the ground line 40 is grounded at the ground point 41. Further, the voltage monitoring unit 86 monitors the voltage at both ends of the resistor 84. One of the changeover switches 80 is connected to a wiring branched from the negative electrode wiring (negative electrode bus) of the solar cell array 300, and the other is connected so that the resistor 84 and the negative electrode of the DC power supply 91 can be switched. The DC power supply 91 applies a voltage so that, for example, the ground potential of the positive electrode of the solar cell array 300 becomes almost zero when the negative electrode of the solar cell array 300 is connected to the ground via the DC power supply 91 and the resistor 84. It is preferable. Other configurations are the same as those in FIG. The contents other than those described in particular are the same as those in the first embodiment.
In FIG. 2, when the changeover switch 80 is connected to the first terminal 80a (a state where the first terminal 80a and the third terminal 80c are connected), the solar cell array 300 is connected to the negative electrode side connection point. 50, a changeover switch 80 (first terminal 80 a), a resistor 84, and a grounding circuit (first grounding circuit) composed of the ground wire 40. On the other hand, when the changeover switch 80 is connected to the second terminal 80b (a state in which the second terminal 80b and the third terminal 80c are connected), the solar cell array 300 is switched to the negative-side connection point 50. The switch 80 (second terminal 80 b), the DC power supply 91, the resistor 84, and the ground line 40 are connected to a ground circuit (second ground circuit). As described above, the changeover switch 80 switches and connects the two types of grounding electric circuits to the solar cell array 300. As described above, the second grounding electric circuit has the DC power supply 91 and is configured to apply a DC voltage to the power generation unit while being connected to the solar cell array 300 (power generation unit).

The solar power generation system 100 as described above is operated as follows as a solar power generation method. During normal operation, the solar cell array 300 and the load device 400 are connected, and the ground potential at all locations of the solar cell array 300 is controlled to zero or more or less than zero using the ground wire 40. Perform normal operation of photovoltaic power generation. Specifically, it operates as follows. Each switch device 102 driven by control from a control system (not shown) and the switches 402 and 404 are both ON (closed), and the changeover switch 80 is connected to the negative electrode wiring (negative electrode side connection point 50) of the solar cell array 300. ) And the resistor 84 (a state in which the changeover switch 80 is connected to the first terminal 80a and the solar cell array 300 is connected to the first ground circuit). That is, during normal operation, the first grounding circuit is connected to the solar cell array 300 as a countermeasure against PID (that is, the negative electrode of the solar cell array 300 is grounded at the grounding point 41 via the grounding wire 40 and the resistor 84). . In the example of FIG. 2, a solar cell using a p-type semiconductor for the bulk of the solar cell or a transparent conductive film is shown as an example. Therefore, the negative electrode wiring is grounded. When an n-type semiconductor is used for the bulk of the solar cell, it goes without saying that the positive electrode wiring (positive electrode bus) is grounded via the resistor 84. In this way, the negative electrode of the photovoltaic power generation system 100 is grounded via the resistor 84. In this way, during normal operation of the system, the changeover switch 80 (potential control unit) uses the ground wire 40 to connect the negative electrode of the solar cell array 300 (positive electrode when an n-type semiconductor is used for the bulk of the solar cell). Is controlled to zero. Thereby, the ground potential of each of the solar cell strings 12a to 12c can be controlled to zero or more, and the PID phenomenon can be avoided.

The voltage monitoring unit 86 detects a ground fault of the solar cell array 300 during normal operation of the solar power generation system 100. Specifically, in the state where the negative electrode wiring (negative electrode bus) side of the solar cell array 300 is connected to the resistor 84 by the changeover switch 80 (that is, the state connected to the first ground circuit), the voltage monitoring unit 86 The voltage V1 applied to both ends of 84 is measured. That is, the voltage monitoring unit 86 measures the voltage V1 across the resistor 84 as a measurement value based on the current flowing through the first grounding circuit connected to the solar cell array 300. When the measured voltage V1 exceeds a preset threshold value, it is determined that there is a ground fault by a control system (not shown). And the solar power generation system 100 can be stopped urgently. When a ground fault occurs in the middle of any solar cell string 12 or on the positive electrode side, a closed circuit is formed via the ground fault location and the first grounding circuit, and the sun existing between the ground fault location and the negative electrode Since a voltage is generated in the resistor 84 when a current flows through the ground circuit 40 due to the electromotive force of the battery, a ground fault can be determined based on the voltage V1. However, in such a configuration, when a ground fault occurs on the negative electrode side of any of the solar battery strings 12, there is no electromotive force in the closed circuit formed via the grounding location and the first grounding circuit, Therefore, no voltage is generated in the resistor 84, and ground fault detection is difficult. Therefore, the blind spot of the ground fault detection that normal operation is continued as it is is generated.

Therefore, in the second embodiment, the second grounding circuit is connected to the negative electrode wiring (negative electrode bus) side of the solar cell array 300 by the changeover switch 80 periodically, and the ground fault detection device 36 detects the ground fault. I do. For example, the ground fault is detected every time the photovoltaic power generation system 100 is started or periodically during operation. For example, ground fault detection is performed at intervals of 1 to 2 hours.
When detecting the ground fault, the ground fault is detected in units of the solar cell array 300 in a state where the connection between the solar cell array 300 and the load device 400 is disconnected by the switches 402 and 404 driven by control from a control system (not shown). Thus, the influence from the load device 400 can be eliminated.

When the negative electrode of the solar cell array 300 is connected to the ground via the DC power source 91 and the resistor 84 (that is, when the solar cell array 300 is connected to the second ground circuit), the DC power source 91 is, for example, solar It is preferable to apply a voltage so that the ground potential of the positive electrodes of the battery array 300 is almost zero. In this case, when the detection sensitivities in both the state where the DC power supply 90 is inserted between the changeover switch 80 and the resistor 84 and the state where the DC power source 90 is not inserted are combined, uniform ground fault detection is performed everywhere in the solar cell array 300. Sensitivity can be obtained. In this state, the voltage monitoring unit 86 measures the voltage V <b> 2 applied across the resistor 84. That is, the voltage monitoring unit 86 measures the voltage V2 across the resistor 84 as a measurement value based on the current flowing through the second grounding circuit connected to the solar cell array 300. When the measured voltage V2 exceeds a preset threshold value, it is determined that there is a ground fault by a control system (not shown). And the solar power generation system 100 can be stopped urgently. In the example of the ground fault detection device shown in FIG. 2, even when a ground fault (such as defective insulation) occurs in any part of the solar cell array 300, a potential difference occurs between both ends of the resistor 84, so that the ground fault can be detected. It becomes.

Thus, in the case of ground fault detection, the ground fault detection device 36 detects the ground fault of the solar cell array 300 in each of two or more different ground potential states controlled by the changeover switch 80 (potential control unit). To do. In other words, in a state where the negative electrode wiring (negative electrode bus) side of the solar cell array 300 is connected to the resistor 84 by the changeover switch 80, the potential of the negative electrode of the solar cell array 300 is grounded by being connected to the ground line 40. ) Potential. Therefore, the ground potential of the positive electrode of solar cell array 300 (the positive electrode of each solar cell string 12a to 12c) is controlled to a positive potential. The ground potential in the middle of each solar cell string 12a-c is also positive. On the other hand, when the connection of the negative electrode wiring (negative electrode bus) side of the solar cell array 300 to the DC power source 91 side is switched by the changeover switch 80, the voltage from the DC power source 91 is set so that the ground potential of the positive electrode of the solar cell array 300 becomes almost zero. Applied. Therefore, the ground potential of the entire solar cell array 300 (the entire solar cell strings 12a to 12c) is a negative potential equal to or lower than the ground potential.
In this way, by applying a voltage so that the ground potential of the positive electrode becomes almost zero, detection in both the state where the DC power supply 90 is inserted between the changeover switch 80 and the resistor 84 and the state where it is not inserted are performed. When the sensitivity is integrated, uniform ground fault detection sensitivity can be obtained everywhere in the solar cell array 300.
Thus, the changeover switch 80 (an example of a potential control unit) can intentionally control the ground potential of the solar cell array 300.

As described above, in the example of the ground fault detection device shown in FIG. 2, such a ground fault can be detected even when a ground fault (insulation failure or the like) occurs in any part of the solar cell array 300. Therefore, ground fault detection becomes possible at the stage when the first ground fault accident (first ground fault accident) occurs, and the blind spot location for ground fault detection can be eliminated.

As described above, in the second embodiment, the same ground wire 40 is used, on the one hand, for PID countermeasures, and on the other hand, for ground fault detection that excludes blind spots. During normal operation, since the ground potential of the negative electrode of the solar cell array 300 becomes the ground potential by the changeover switch 80 (potential control unit), the two different values controlled by the changeover switch 80 (potential control unit). The point that one of the above ground potential states is set is the same as in FIG.

In the example described above, the ground fault determination is performed simply by comparing the voltage of the resistor 84 with the threshold value, but the present invention is not limited to this. For example, in a state where the negative electrode wiring (negative electrode bus) side of the solar cell array 300 is connected to the resistor 84 by the changeover switch 80, the voltage monitoring unit 86 measures the voltage V1 applied to both ends of the resistor 84. Next, in a state where the negative electrode wiring (negative electrode bus) of the solar cell array 300 is connected to the DC power supply 91 side by the changeover switch 80, the voltage monitoring unit 86 measures the voltage Vb applied to both ends of the resistor 84. Then, the insulation resistance is calculated using the voltage Vdc of the DC power supply 91, the resistance value R of the resistor 84, and the measured voltages V1 and Vb, and if the obtained insulation resistance is less than a preset threshold value, It is also preferable to determine that there is a fault.

As described above, according to the second embodiment, it is possible to eliminate a blind spot where it is difficult to detect a ground fault while grounding for PID countermeasures is performed.

FIG. 3 is a configuration diagram illustrating the configuration of the photovoltaic power generation system according to the third embodiment. 3, in photovoltaic power generation system 100 according to Embodiment 3, an AC power supply 87 is further arranged in the configuration of FIG. 1 as one of the internal configurations of ground fault detection device 36. In other words, the ground fault detection device 36 includes a changeover switch 80 (an example of a potential control unit), a ground fault detection unit (a resistor 84 and a voltage monitoring unit 86), an AC power supply 87, and a ground line 40. One of both ends of the resistor 84 is connected to the changeover switch 80 and the AC power supply 87, the other is connected to the ground line 40, and the ground line 40 is grounded at the ground point 41. Further, the voltage monitoring unit 86 monitors the voltage at both ends of the resistor 84. One of the changeover switches 80 is connected to a wiring branched from the negative electrode wiring (negative electrode bus) of the solar cell array 300, and the other is connected so that the resistor 84 and the AC power supply 87 can be switched. Other configurations are the same as those in FIG. The contents other than those described in particular are the same as those in the first embodiment.
That is, in FIG. 3, when the changeover switch 80 is connected to the first terminal 80a (a state where the first terminal 80a and the third terminal 80c are connected), the solar cell array 300 is connected to the negative electrode side connection point. 50, a changeover switch 80 (first terminal 80 a), a resistor 84, and a grounding circuit (first grounding circuit) composed of the ground wire 40. On the other hand, when the changeover switch 80 is connected to the second terminal 80b (a state in which the second terminal 80b and the third terminal 80c are connected), the corresponding battery array 300 is switched to the negative-side connection point 50. The switch 80 (second terminal 80 b), the AC voltage source 87, the resistor 84, and the ground wire 40 are connected to a ground circuit (second ground circuit). As described above, the changeover switch 80 switches and connects the two types of grounding electric circuits to the solar cell array 300. As described above, the second grounding electric circuit has the AC power supply 87 and is configured to apply an AC voltage to the power generation unit while being connected to the solar cell array 300 (power generation unit).

The solar power generation system 100 as described above is operated as follows as a solar power generation method. During normal operation, solar power generation is performed with solar cell array 300 and load device 400 connected, and ground potential is controlled to be zero or more or zero or less at all locations of solar cell array 300 using ground wire 40. Perform normal operation. Specifically, it operates as follows. Each switch device 102 driven by control from a control system (not shown) and the switches 402 and 404 are all in an ON state (closed), and the changeover switch 80 is connected to the negative electrode wiring (negative electrode bus) and the resistance of the solar cell array 300. The normal operation is performed in a state where the terminal 84 is connected (a state where the resistor 84 is turned on). That is, during normal operation, the first grounding circuit is connected to the solar cell array 300 as a countermeasure against PID (that is, the negative electrode of the solar cell array 300 is grounded at the grounding point 41 via the grounding wire 40 and the resistor 84). . In the example of FIG. 3, the case where a p-type semiconductor is used for the bulk of a solar cell, or the solar cell using a transparent conductive film is shown as an example. Therefore, the negative electrode wiring is grounded. When an n-type semiconductor is used for the bulk of the solar cell, it goes without saying that the positive electrode wiring (positive electrode bus) is grounded via the resistor 84. In this way, the negative electrode of the photovoltaic power generation system 100 is grounded via the resistor 84. In this way, during the normal operation of the system, the changeover switch 80 (potential control unit) uses the ground wire 40 to connect the ground potential at a predetermined point of the solar cell array 300 to the positive electrode (the n-type semiconductor is placed in the bulk of the solar cell). When used, it is controlled to the potential of the negative electrode). Thereby, the negative electrode of each solar cell string 12a-c can be controlled to the same potential as the ground, and the PID phenomenon can be avoided.

The voltage monitoring unit 86 detects a ground fault of the solar cell array 300 during normal operation of the solar power generation system 100. Specifically, in a state where the negative electrode wiring (negative electrode bus) side of the solar cell array 300 is connected to the resistor 84 by the changeover switch 80 (that is, connected to the first ground circuit), the voltage monitoring unit 86 is The voltage V1 applied across the resistor 84 is measured. That is, the voltage monitoring unit 86 measures the voltage V1 across the resistor 84 as a measurement value based on the current flowing through the first grounding circuit connected to the solar cell array 300. When the measured voltage V1 exceeds a preset threshold value, it is determined that there is a ground fault by a control system (not shown). And the solar power generation system 100 can be stopped urgently. When a ground fault occurs in the middle of any solar cell string 12 or on the positive electrode side, a closed circuit is formed via the ground fault location and the first grounding circuit, and the sun existing between the ground fault location and the negative electrode Since a voltage is generated in the resistor 84 when a current flows through the ground circuit 40 due to the electromotive force of the battery, a ground fault can be determined based on the voltage V1. However, in such a configuration, when a ground fault occurs on the negative electrode side of any of the solar battery strings 12, there is no electromotive force in the closed circuit formed via the grounding location and the first grounding circuit, Therefore, no voltage is generated in the resistor 84, and ground fault detection is difficult. Therefore, the blind spot of the ground fault detection that normal operation is continued as it is is generated.

Therefore, in the third embodiment, the second grounding electric circuit is connected to the solar cell array 300 by periodically switching the changeover switch 80, and the ground fault detection device 36 performs ground fault detection. For example, the ground fault is detected every time the photovoltaic power generation system 100 is started or periodically during operation. For example, ground fault detection is performed at intervals of 1 to 2 hours.
When detecting the ground fault, the ground fault is detected in units of the solar cell array 300 in a state where the connection between the solar cell array 300 and the load device 400 is disconnected by the switches 402 and 404 driven by control from a control system (not shown). May be performed. Thereby, the influence from the load apparatus 400 can be excluded.

In this state, the voltage monitoring unit 86 measures the voltage V2 in phase with the AC power supply 87 applied to both ends of the resistor 84 in synchronization with the phase of the AC power supply 87. That is, the voltage monitoring unit 86 measures the voltage V2 across the resistor 84 as a measurement value based on the current flowing through the second grounding circuit connected to the solar cell array 300. Then, when the voltage V2 exceeds a preset threshold for the phase, a control system (not shown) determines that there is a ground fault. And the solar power generation system 100 can be stopped urgently. In the example of the ground fault detection device shown in FIG. 3, even when a ground fault (insulation failure or the like) occurs in any part of the solar cell array 300, a potential difference occurs between both ends of the resistor 84, so that the ground fault can be detected. It becomes.

Thus, in the case of ground fault detection, the ground fault detection device 36 detects the ground fault of the solar cell array 300 in each of two or more different ground potential states controlled by the changeover switch 80 (potential control unit). To do. In other words, in a state where the negative electrode wiring (negative electrode bus) side of the solar cell array 300 is connected to the resistor 84 by the changeover switch 80 (a state where the solar cell array 300 is connected to the first grounding electric circuit), The negative electrode potential of the battery array 300 becomes the ground (ground) potential. Therefore, the ground potential of the positive electrode of solar cell array 300 (the positive electrode of each solar cell string 12a to 12c) is controlled to a positive potential. The ground potential in the middle of each solar cell string 12a-c is also positive. On the other hand, when the connection of the negative electrode wiring (negative electrode bus) side of the solar cell array 300 is switched to the AC power supply 87 side by the changeover switch 80 (that is, when the solar cell array 300 is connected to the second ground circuit by the changeover switch 80), The ground potential of the negative electrode of the solar cell array 300 is variable depending on the voltage pole applied from the AC power supply 87. Thus, the changeover switch 80 (an example of a potential control unit) can intentionally control the ground potential of the solar cell array 300.

As described above, in the example of the ground fault detection device shown in FIG. 3, it is possible to detect such a ground fault even when a ground fault (such as an insulation failure) occurs in any part of the solar cell array 300. Therefore, ground fault detection becomes possible at the stage when the first ground fault accident (first ground fault accident) occurs, and the blind spot location for ground fault detection can be eliminated.

As described above, in the third embodiment, the same ground wire 40 is used, on the one hand, for PID countermeasures, and on the other hand, for ground fault detection that excludes blind spots. During normal operation, the changeover switch 80 (potential control unit) controls the AC voltage not to be applied to the negative electrode or the positive electrode of the solar cell array 300, and the ground potential of the negative electrode of the solar cell array 300 is ground (ground). 1 is the same as FIG. 1 in that it is set to one of two or more different ground potential states controlled by the changeover switch 80 (potential control unit).

In the example described above, the ground fault determination is performed simply by comparing the voltage of the resistor 84 with the threshold value, but the present invention is not limited to this. For example, in a state where the negative electrode wiring (negative electrode bus) side of the solar cell array 300 is connected to the resistor 84 by the changeover switch 80, the voltage monitoring unit 86 measures the voltage V1 applied to both ends of the resistor 84. Next, in a state where the negative electrode wiring (negative electrode bus) of the solar cell array 300 is connected to the AC power supply 87 side by the changeover switch 80, the voltage monitoring unit 86 measures the voltage Vc applied across the resistor 84. Then, the insulation resistance is calculated using the voltage Vac of the AC power supply 87, the resistance value R of the resistor 84, and the measured voltages V1 and Vc, and if the obtained insulation resistance is less than a preset threshold value, It is also preferable to determine that there is a fault.

As described above, according to the third embodiment, it is possible to eliminate a blind spot where it is difficult to detect a ground fault while performing grounding for PID countermeasures.

FIG. 4 is a configuration diagram showing the configuration of the photovoltaic power generation system according to the fourth embodiment. 4, in the photovoltaic power generation system 100 according to the fourth embodiment, as an internal configuration of the ground fault detection device 36, a switch 81 and two resistors 83a and 83b are arranged instead of the changeover switch 80 of FIG. The In other words, the ground fault detection device 36 includes a switch 81 (an example of a potential control unit), resistors 83a and 83b, a ground fault detection unit (the resistor 84 and the voltage monitoring unit 86), and the ground line 40. One end of the resistor 84 is connected to the switch 81 and the resistor 83a, the other end is connected to the ground line 40, and the ground line 40 is grounded at the ground point 41. Further, the voltage monitoring unit 86 monitors the voltage at both ends of the resistor 84. The other of both ends of the switch 81, one of which is connected to the resistor 84, is connected to one of both ends of the resistor 83b. The other side of the resistor 83a is connected to a wiring branched from the negative electrode wiring (negative electrode bus) of the solar cell array 300. The other of the resistors 83b is connected to a wiring branched from the positive electrode wiring (positive electrode bus) of the solar cell array 300. For the resistors 83a and 83b, for example, resistors having the same resistance value may be used. In other words, when the switch 81 is ON (closed), the midpoint obtained by dividing the voltage (potential difference) between the two electrodes of the solar cell array 300 by the resistors 83a and 83b is connected to the ground via the resistor 84.

The switch 81 uses a switch that can automatically control the opening / closing operation electrically. Although a mechanical switch may be used, it is more preferable to use, for example, a semiconductor switch. For example, it is preferable to use a MOSFET. Other configurations are the same as those in FIG. The contents other than those described in particular are the same as those in the first embodiment.
That is, in FIG. 4, when the switch 81 is OFF (open), the solar cell array 300 has a ground circuit (first ground circuit) composed of the negative electrode side connection point 50, the resistor 83 a, the resistor 84, and the ground wire 40. ) Is connected. On the other hand, when the switch 81 is ON (closed), the solar cell array 300 includes the resistor 84 and the ground wire 40 at the midpoint obtained by dividing the negative electrode side connection point 50 and the positive electrode side connection point 51 by the resistor 83a and the resistor 83b. It will be in the state connected to the earthing electric circuit (2nd earthing electric circuit) connected to the earth through this. As described above, the switch 81 switches and connects the two types of grounding circuit to the solar cell array 300. As described above, the first grounding electric circuit is configured to be connectable to one electrode of the solar cell array 300 (power generation unit) and includes the first resistor 83a. The second grounding electric circuit is configured to be an electric circuit that is grounded at a midpoint obtained by dividing the positive electrode and the negative electrode of the solar cell array 300 (power generation unit) by a given resistance (resistor 83a and resistor 83b). Yes.

The solar power generation system 100 as described above is operated as follows as a solar power generation method. During normal operation, solar power generation is performed with solar cell array 300 and load device 400 connected, and ground potential at all locations of solar cell array 300 is controlled to be greater than or equal to zero using ground line 40. Perform normal operation. Specifically, it operates as follows. Each switch device 102 driven by control from a control system (not shown) and the switches 402 and 404 are all in an ON (closed) state, and the switch 81 is in an OFF (open) state (connected to the first ground circuit). Normal operation is performed in the That is, during normal operation, the first grounding circuit is connected to the solar cell array 300 as a countermeasure against PID (that is, the negative electrode of the solar cell array 300 is grounded at the grounding point 41 via the grounding wire 40 and the resistors 84 and 83a. To do). In the example of FIG. 4, a solar cell using a p-type semiconductor for the bulk of the solar cell or a transparent conductive film is shown as an example. Therefore, the negative electrode wiring is grounded. When an n-type semiconductor is used for the bulk of the solar cell, it goes without saying that the positive electrode wiring (positive electrode bus) is grounded via the resistors 84 and 83a. In this way, the negative electrode of the photovoltaic power generation system 100 is grounded via the resistor 84. In this way, during the normal operation of the system, the changeover switch 80 (potential control unit) uses the ground wire 40 to set the ground potential at a predetermined point of the solar cell array 300 to the positive electrode (the n-type semiconductor is placed in the solar cell bulk). When used, it is controlled to the potential of the negative electrode). Thereby, the negative electrode of each solar cell string 12a-c can be controlled to the ground potential, and the PID phenomenon can be avoided.

The voltage monitoring unit 86 detects a ground fault of the solar cell array 300 during normal operation of the solar power generation system 100. Specifically, the voltage monitoring unit 86 measures the voltage V1 applied to both ends of the resistor 84 in a state where the negative electrode wiring (negative electrode bus) side of the solar cell array 300 is connected to the series resistors 84 and 83a by the changeover switch 80. To do. That is, the voltage monitoring unit 86 measures the voltage V1 across the resistor 84 as a measurement value based on the current flowing through the first grounding circuit connected to the solar cell array 300. When the measured voltage V1 exceeds a preset threshold value, it is determined that there is a ground fault by a control system (not shown). And the solar power generation system 100 can be stopped urgently. When a ground fault occurs in the middle of any solar cell string 12 or on the positive electrode side, a closed circuit is formed via the ground fault location and the first grounding circuit, and the sun existing between the ground fault location and the negative electrode Since a voltage is generated in the resistor 84 when a current flows through the ground circuit 40 due to the electromotive force of the battery, a ground fault can be determined based on the voltage V1. However, in such a configuration, when a ground fault occurs on the negative electrode side of one of the solar battery strings 12, no electromotive force exists in the closed circuit formed via the ground fault location and the first grounding circuit. Since no voltage is generated in the resistor 84, ground fault detection is difficult. Therefore, the blind spot of the ground fault detection that normal operation is continued as it is is generated.

Therefore, in the fourth embodiment, the ground fault detector 36 is further connected to the solar cell array 300 by periodically switching the switch 81 from OFF (open) to ON (closed) to connect the second grounding electric circuit to the solar cell array 300. The ground fault is detected at. For example, the ground fault is detected every time the photovoltaic power generation system 100 is started or periodically during operation. For example, ground fault detection is performed at intervals of 1 to 2 hours.
When detecting the ground fault, the ground fault is detected in units of the solar cell array 300 in a state where the connection between the solar cell array 300 and the load device 400 is disconnected by the switches 402 and 404 driven by control from a control system (not shown). May be performed. Thereby, the influence from the load apparatus 400 can be excluded.

In this state, the voltage monitoring unit 86 measures the voltage V <b> 2 applied across the resistor 84. That is, the voltage monitoring unit 86 measures the voltage V2 across the resistor 84 as a measurement value based on the current flowing through the second grounding circuit connected to the solar cell array 300. When the voltage V2 exceeds a preset threshold value, a control system (not shown) determines that there is a ground fault. And the solar power generation system 100 can be stopped urgently. In the example of the ground fault detection device shown in FIG. 4, in the state where the switch 81 is turned on (closed), it is difficult to determine the ground fault when a ground fault occurs at the intermediate potential position of any solar cell string 12. However, when a ground fault occurs at this position, the ground fault can be determined during normal operation by the voltage V1 described above. Therefore, it becomes possible to detect a ground fault at the stage when the first ground fault accident (first ground fault accident) occurs, and it is possible to eliminate the blind spot of ground fault detection by the current monitoring unit 42 during normal operation.

Thus, in the case of ground fault detection, the ground fault detection device 36 detects the ground fault of the solar cell array 300 in each of two or more different ground potential states controlled by the switch 81 (potential control unit). . In other words, when the switch 81 is in the OFF state, the potential of the negative electrode of the solar cell array 300 becomes the potential of the ground (ground) by being connected to the ground line 40. Therefore, the ground potential of the positive electrode of solar cell array 300 (the positive electrode of each solar cell string 12a to 12c) is controlled to a positive potential. The ground potential in the middle of each solar cell string 12a-c is also positive. On the other hand, when the switch 81 is switched to ON, the ground potential, which is the intermediate potential between the two poles of the solar cell array 300, becomes the ground potential. Thus, the changeover switch 80 (an example of a potential control unit) can intentionally control the ground potential of the solar cell array 300.

As described above, in the example of the ground fault detection device shown in FIG. 4, it is possible to detect such a ground fault even when a ground fault accident (insulation failure or the like) occurs in any part of the solar cell array 300. Therefore, ground fault detection becomes possible at the stage when the first ground fault accident (first ground fault accident) occurs, and the blind spot location for ground fault detection can be eliminated.

As described above, in the fourth embodiment, the same ground wire 40 is used, on the one hand, for PID countermeasures, and on the other hand, for ground fault detection that excludes blind spots. During normal operation, since the ground potential of the negative electrode of the solar cell array 300 becomes the ground potential by the switch 81 (potential control unit), two or more different voltages controlled by the switch 81 (potential control unit) are used. The point that one of the ground potential states is set is the same as in FIG.

As described above, according to the fourth embodiment, it is possible to eliminate or further reduce a blind spot where it is difficult to detect a ground fault while performing grounding for PID countermeasures.

FIG. 5 is a configuration diagram showing the configuration of the photovoltaic power generation system in the fifth embodiment. 5, in the photovoltaic power generation system 100 according to the fifth embodiment, a DC power source 92 is arranged instead of the changeover switch 80 in FIG. In other words, the ground fault detection device 36 includes a DC power source 92, a ground fault detection unit (the resistor 84 and the voltage monitoring unit 86), and the ground line 40. One end of the resistor 84 is connected to the negative electrode of the DC power supply 92, and is connected to a wiring branched from the negative electrode wiring (negative electrode bus) of the solar cell array 300 via the DC power supply 92. The other end of the resistor 84 is grounded. The DC power supply 92 applies a voltage so that the ground potential at all locations of the solar cell array 300 is positive. Other configurations are the same as those in FIG. The contents other than those described in particular are the same as those in the first embodiment.

The solar power generation system 100 as described above is operated as follows as a solar power generation method. During normal operation, solar power generation is performed with solar cell array 300 and load device 400 connected, and ground potential at all locations of solar cell array 300 is controlled to be positive or negative using ground wire 40. To drive. Specifically, it operates as follows. Each switch device 102 driven by control from a control system (not shown) and the switches 402 and 404 are both in an ON (closed) state and are normally operated. That is, during normal operation, as a countermeasure against PID, the negative electrode of the DC power source 92 is grounded at the grounding point 41 by the ground wire 40 via at least a part (resistor 84) of the ground fault detection unit, and the positive electrode of the DC power source 92 is connected. Connect to the negative electrode of the solar cell array 300. In this way, the DC power source 92 controls the ground potential to be a positive potential even at the negative electrode (minimum potential) of the photovoltaic power generation system 100. In this way, during normal operation of the system, the DC power supply 92 (potential control unit) uses the ground line 40 to set the ground potential at a predetermined point of the solar cell array 300 to a positive potential (n-type semiconductor in the solar cell bulk). When using, control to negative potential). Thereby, the negative electrode of each solar cell string 12a-c can be controlled to a positive potential with respect to the ground potential, and the PID phenomenon can be avoided.

In the example of FIG. 5, when a p-type semiconductor is used for the bulk of a solar cell, or a solar cell using a transparent conductive film is shown as an example. Therefore, the positive electrode of the DC power supply 92 whose negative electrode side is grounded via the ground wire 40 and the resistor 84 is grounded to the negative electrode wiring of the solar cell array 300. When an n-type semiconductor is used for the bulk of the solar cell, the negative electrode of the DC power supply 92 whose positive electrode side is grounded via the ground wire 40 and the resistor 84 is grounded to the positive electrode wiring (positive electrode bus) of the solar cell array 300. Needless to say. As described above, in FIG. 5, the grounding circuit is configured such that one side is connected to the ground and the other side is connectable to the positive electrode or the negative electrode of the solar cell array 300 (power generation unit). The grounding circuit has a DC power source 92 and makes the ground potential at all locations of the solar cell array 300 (power generation unit) positive or negative.

The voltage monitoring unit 86 detects a ground fault of the solar cell array 300 during normal operation of the solar power generation system 100. Specifically, the voltage monitoring unit 86 measures the voltage V <b> 1 across the resistor 84 in a state in which the lowest ground potential of the solar cell array 300 is controlled to be a positive potential by the DC power source 92. That is, the voltage monitoring unit 86 measures the voltage V1 across the resistor 84 as a measurement value based on the current flowing through the grounding circuit (the grounding circuit having the DC power supply 92, the resistor 84, and the grounding line 40) connected to the solar cell array 300. To do. When the measured voltage V1 exceeds a preset threshold value, it is determined that there is a ground fault by a control system (not shown). And the solar power generation system 100 can be stopped urgently. In the example of the ground fault detection device shown in FIG. 5, when a ground fault occurs in the middle of one of the solar battery strings 12 or on the positive electrode side, a closed circuit is formed through the ground fault location and the grounding electrical circuit 40. Since the solar cell module existing between the ground fault location and the negative electrode and the DC power source 92 become an electromotive force and a current flows through the grounding circuit 40, a potential difference is generated between both ends of the resistor 84, so that the ground fault can be detected. Become. Similarly, when a ground fault occurs on the negative electrode side of any of the solar battery strings 12, a DC power source 92 existing between the ground fault location and the negative electrode serves as an electromotive force and a current flows through the grounding circuit 40. As a result, a potential difference is generated between both ends of the resistor 84, so that the ground fault can be detected. Therefore, ground fault detection becomes possible at the stage when the first ground fault accident (first ground fault accident) occurs, and the blind spot location for ground fault detection can be eliminated. As described above, the ground fault detection unit (resistor 84, voltage monitoring unit 86) measures the measurement value based on the current flowing through the ground circuit, and detects the ground fault based on the measurement result.

Thus, the DC power supply 92 (an example of a potential control unit) can intentionally control the ground potential of the solar cell array 300.

As described above, in the fifth embodiment, the same ground wire 40 is used, on the one hand, for PID countermeasures, and on the other hand, for ground fault detection that excludes blind spots.

As described above, according to the fifth embodiment, it is possible to eliminate a blind spot where it is difficult to detect a ground fault while grounding for PID countermeasures is performed.

FIG. 6 is a configuration diagram showing the configuration of the photovoltaic power generation system according to the sixth embodiment. 6, in the photovoltaic power generation system 100 according to the sixth embodiment, an AC power supply 93 is arranged instead of the changeover switch 80 shown in FIG. In other words, the ground fault detection device 36 includes an AC power source 93, a ground fault detection unit (the resistor 84 and the voltage monitoring unit 86), and the ground wire 40. One end of the resistor 84 is connected to the AC power supply 93, and is connected to the wiring branched from the negative electrode side connection point 50 of the negative electrode wiring (negative electrode bus) of the solar cell array 300 via the AC power supply 93. The other end of the resistor 84 is grounded. The AC power supply 93 applies an AC voltage so that the ground potential of the negative electrode bus of the solar cell array 300 varies around 0V. Other configurations are the same as those in FIG. The contents other than those specifically described are the same as those in the fifth embodiment.

The solar power generation system 100 as described above is operated as follows as a solar power generation method. At the time of normal operation, the solar cell array 300 and the load device 400 are connected, and the time average value of the ground potential at all points of the solar cell array 300 is controlled to a potential of zero or more or zero or less using the ground line 40. In the state, drive solar power. Specifically, it operates as follows. Each switch device 102 driven by control from a control system (not shown) and the switches 402 and 404 are both in an ON (closed) state and are normally operated. That is, during normal operation, one phase of the AC power supply 93 is grounded at the grounding point 41 by the grounding wire 40 via at least a part (resistor 84) of the ground fault detection unit, as a countermeasure against PID. The pole is connected to the negative electrode of the solar cell array 300. In this way, the AC power supply 93 is controlled so that the time average value of the ground potential becomes zero even at the negative electrode (minimum potential) of the photovoltaic power generation system 100. Thus, during normal operation of the system, the AC power supply 93 (potential control unit) uses the ground wire 40 to set the ground potential at a predetermined point of the solar cell array 300 to 0 or positive potential (n in the bulk of the solar cell). When a type semiconductor is used, control is performed to 0 or a negative potential). Thereby, the PID phenomenon can be avoided.

In the example of FIG. 6, a solar cell using a p-type semiconductor for the bulk of the solar cell or a transparent conductive film is shown as an example. Therefore, the reverse phase of the AC power supply 93 whose one phase is grounded via the ground line 40 and the resistor 84 is grounded to the negative electrode wiring of the solar cell array 300. When an n-type semiconductor is used for the bulk of the solar cell, the reverse phase of the AC power supply 93 whose positive electrode side is grounded via the ground wire 40 and the resistor 84 is grounded to the positive electrode wiring (positive electrode bus) of the solar cell array 300. Needless to say. Thus, the grounding circuit is configured such that one side is connected to the ground and the other side is connectable to the positive electrode or the negative electrode of the solar cell array 300 (power generation unit). The grounding circuit has an AC power supply 93, and the ground potential of all locations of the solar cell array 300 (power generation unit) is averaged over time to zero or less.

The voltage monitoring unit 86 detects a ground fault of the solar cell array 300 during normal operation of the solar power generation system 100. Specifically, the voltage monitoring unit 86 measures the voltage V <b> 1 applied across the resistor 84 in a state where the ground potential of the lowest potential of the solar cell array 300 is fluctuated around 0 by the AC power supply 93. To do. That is, the voltage monitoring unit 86 measures the voltage V1 across the resistor 84 as a measured value based on the current flowing through the grounding circuit (the AC power supply 93, the resistor 84, and the grounding circuit 40 having the grounding wire 40) connected to the solar cell array 300. To do. Of the measured amplitude of the voltage V1, when a component having the same phase as that of the AC power supply 93 exceeds a preset threshold, it is determined that a ground fault has occurred by a control system (not shown). As described above, the ground fault detection unit measures the measurement value based on the current flowing through the grounding circuit, and detects the ground fault based on the measurement result. And the solar power generation system 100 can be stopped urgently. In the example of the ground fault detection device shown in FIG. 6, even if a ground fault occurs at any location of the solar cell string 12, a closed circuit is formed via the ground fault location and the grounding electric circuit 40, and Since the AC power supply 93 is included in the ground, a current difference flows between the two ends of the resistor 84 when a current flows through the grounding circuit 40, so that the ground fault can be detected. Therefore, ground fault detection becomes possible at the stage when the first ground fault accident (first ground fault accident) occurs, and the blind spot location for ground fault detection can be eliminated.

Thus, the AC power supply 93 (an example of a potential control unit) can intentionally control the ground potential of the solar cell array 300.

As described above, in the sixth embodiment, the same grounding wire 40 is used, on the one hand, for PID countermeasures, and on the other hand, for ground fault detection excluding blind spots.

As described above, according to the fifth embodiment, it is possible to eliminate a blind spot where it is difficult to detect a ground fault while grounding for PID countermeasures is performed.

In each of the above-described embodiments, the configuration has been described in which the ground fault is detected and the PID countermeasure is taken for each solar cell array 300 unit. However, the present invention is not limited to this. In the seventh embodiment, a configuration in which ground fault detection and PID countermeasures are performed for each of the solar cell strings 12a to 12c will be described.

FIG. 7 is a configuration diagram showing the configuration of the photovoltaic power generation system according to the seventh embodiment. In FIG. 7, between the negative electrode wiring of each solar cell string 12a-c and the corresponding switch device 102a, c, e, the negative electrode of the corresponding solar cell string 12a-c is disconnected from the system or connected to the system. Switch devices 103a, c, e are arranged. Then, between the positive electrode wiring of each solar cell string 12a-c and the corresponding switch device 102b, d, f, the switch device for disconnecting the positive electrode of the corresponding solar cell string 12a-c from the system or connecting it to the system 103b, d, and f are arranged. In addition, the wiring branched from the negative electrode wiring of each of the solar cell strings 12a to 12c is connected to the ground fault detection device 36 via the backflow prevention diode 46 and the switch device 33. The switch device 103 uses a switch that can automatically electrically control the opening / closing operation. Although a mechanical switch may be used, it is more preferable to use, for example, a semiconductor switch. For example, it is preferable to use a MOSFET.

Specifically, in FIG. 7, the wiring branched from the negative wiring connecting the negative electrode of the solar cell string 12a and the switch device 103a is connected to the negative electrode side of the ground fault detection device 36 via the backflow prevention diode 46a and the switch device 33a. Connected. Moreover, the wiring branched from the positive electrode wiring which connects the positive electrode of the solar cell string 12a and the switch apparatus 103b is connected to the positive electrode side of the ground fault detection apparatus 36 via the switch apparatus 31a. Similarly, a wire branched from a negative electrode wire connecting the negative electrode of the solar cell string 12b and the switch device 103c is connected to the negative electrode side of the ground fault detection device 36 via the backflow prevention diode 46b and the switch device 33b. Moreover, the wiring branched from the positive electrode wiring which connects the positive electrode of the solar cell string 12b and the switch apparatus 103d is connected to the positive electrode side of the ground fault detection apparatus 36 via the switch apparatus 31b. Similarly, a wire branched from a negative electrode wire connecting the negative electrode of the solar cell string 12c and the switch device 103e is connected to the negative electrode side of the ground fault detection device 36 via the backflow prevention diode 46c and the switch device 33c. Moreover, the wiring branched from the positive electrode wiring which connects the positive electrode of the solar cell string 12c and the switch apparatus 103f is connected to the ground fault detection apparatus 36 via the switch apparatus 31c. The connection from each solar cell string 12 to the ground fault detection device 36 is connected in parallel as shown in FIG. The negative side of the ground fault detection device 36 is grounded to the ground location 41 via the ground wire 40. As shown in FIG. 7, the diodes 46a to 46c are connected with the direction from the ground (ground) toward the negative electrodes of the solar cell strings 12a to 12c as the forward direction.

In the example of FIG. 7, the switch device 102, the backflow prevention diode 20, and the switches 402 and 404 are disposed in the same connection box (dotted line), and the switch device 103, the backflow prevention diode 46, and the ground fault detection device 36 are provided. The example arrange | positioned in another one connection box (dotted line) is shown. If the connection box is not particularly divided, the function of the switch device 103 can be substituted by the switch device 102. In that case, the switch device 103 may be omitted.

Other than that, the contents other than those described in particular are the same as in the first embodiment.

The internal configuration of ground fault detection device 36 in the seventh embodiment may be any of ground fault detection devices 36 shown in FIG. 1 (first embodiment) to FIG. 6 (sixth embodiment). . For example, when the ground fault detection device described in FIG. 1 (Embodiment 1) is used, N (−) of the ground fault detection device 36 in FIG. 7 corresponds to the negative electrode side connection point 50 shown in FIG. P (+) of the ground fault detection device 36 corresponds to the positive electrode side connection point 51 shown in FIG. In this case, during normal operation, as shown in FIG. 7, the switch devices 33a to 33c are turned on (closed), and the ground fault detector 36 and the negative electrode wiring of each of the solar cell strings 12a to 12c are connected. 31a-c are turned OFF (open), and the ground fault detector 36 and the positive electrode wiring of each solar cell string 12a-c are disconnected. In this state, the negative switch wiring of each of the solar cell strings 12a to 12c is connected to the resistor 84 (connected to the first ground circuit) by the changeover switch 80 in the ground fault detection device 36, and PID countermeasures are taken.

In other words, in the step of performing normal operation of solar power generation, a power generation unit (for example, solar cell string 12a) configured using one or more solar cell modules that generate power using sunlight, and a power generation unit or Using a photovoltaic power generation system comprising a load device 400 that consumes or converts power generated by the power generation unit while being insulated from the ground, the power generation unit (for example, the solar cell string 12a) and the load device 400 And connect the ground potential of all locations of the power generation unit to zero or more (when a p-type semiconductor is used for the bulk of the solar cell) or less than zero (use an n-type semiconductor for the bulk of the solar cell) using the first grounding circuit. When used, normal operation of solar power generation is performed.

Further, in the seventh embodiment, ground fault detection is periodically performed for each of the solar cell strings a to c. At that time, the ground fault detection unit uses the grounding wire 40 to generate power in a state where the power generation unit (for example, the solar cell string 12a) and the load device 400 are disconnected (a state where the power generation unit is disconnected from the system). The ground fault of the part is detected.

FIG. 8 is a diagram for explaining a ground fault detection operation using the ground fault detection device 36 described in FIG. 1 (Embodiment 1) in the seventh embodiment. In the seventh embodiment, ground fault detection is performed for each solar cell string 12. When the ground fault is detected, the switch device 103 (for example, the switch devices 103a and 103b) that is driven by the control from the control system (not shown) of the solar cell string 12 (for example, the solar cell string 12a) that is the target of the ground fault detection is turned off. (Open) and the solar cell string 12 to be subjected to ground fault detection is disconnected from the system. After that, the switch device 31 that is driven by control from a control system (not shown) while the switch device 33 (for example, the switch device 33a) of the solar cell string 12 (for example, the solar cell string 12a) that is a target of ground fault detection is kept ON. (For example, the switch device 31a) is turned ON (closed), and the positive electrode side and the negative electrode side of the solar cell string 12 to be detected for ground fault are connected to the ground fault detection device 36. Further, the switch devices 31 and 33 of the solar cell string 12 that are not the targets of ground fault detection are both turned OFF. In this state, the changeover switch 80 (potential control unit) in the ground fault detection device 36 is connected to the solar cell string 12a to be inspected by switching between the first grounding circuit and the second grounding circuit, and the solar cell string 12a. The ground fault is detected by measuring the voltage drop value of the resistor 84 in two ground potential states having different ground potentials. In other words, in a state where the power generation unit and the load device are disconnected, the step of connecting the first grounding circuit to the power generation unit and measuring the measurement value based on the current flowing through the first grounding circuit, the power generation unit and the load device, In a state where the second grounding circuit is connected to the power generation unit, the ground potential of the power generation unit is set to a potential different from that when the first grounding circuit is connected to the power generation unit. Measuring a measurement value based on the flowing current. And the ground fault of a power generation part is detected based on the measured value based on the electric current which flows through the 1st grounding electric circuit connected to the electric power generation part, and the measured value based on the electric current which flows through the 2nd earthing electric circuit connected to the electric power generation part. FIG. 1 illustrates the case where a p-type semiconductor is used for the bulk of the solar cell or the case where a solar cell using a transparent conductive film is used as an example. In Embodiment 7, the bulk of the solar cell is described. When an n-type semiconductor is used, it goes without saying that the positive electrode wiring of the solar cell strings 12a to 12c is connected to the ground fault detection device 36 and grounded during normal operation. Further, during normal operation, the voltage monitoring unit 86 may constantly monitor the voltage while taking measures against PID, and the ground fault may be determined.

Further, in the seventh embodiment, when the ground fault detection device 36 described in FIG. 2 (the second embodiment) is used, N (−) of the ground fault detection device 36 in FIG. 50, and nothing is connected to the P (+) side of the ground fault detection device 36 in FIG. That is, when the ground fault detection device 36 shown in FIG. 2 is used in the seventh embodiment, wiring branched from the positive electrode wiring of each of the solar cell strings 12a to 12c becomes unnecessary. In this case, during normal operation, the switch devices 33a to 33c are turned on (closed), the changeover switch 80 in the ground fault detection device 36 is connected to the terminal 80a (that is, connected to the first ground circuit), and PID Take measures. Further, ground fault detection is periodically performed for each of the solar cell strings a to c. Specifically, first, the solar cell string (for example, the solar cell string 12a) to be inspected is disconnected from the system by the switch devices 103a and 103b (the other switch devices 103c to 103f are turned on (closed)). To do). Then, the switch device 33a is turned on (closed) to connect the solar cell string 12a to the ground fault detection device 36 (the other solar cell strings 12b and 12c are separated from the ground fault detection device 36 by the switch devices 33b and c). In this state, the changeover switch 80 in the ground fault detection device 36 is used to switch and connect the first grounding circuit and the second grounding circuit to the solar cell string 12a to be inspected. The ground fault is detected by measuring the voltage drop value of the resistor 84 in the potential state. During normal operation, the voltage monitoring unit 86 may constantly monitor the voltage while taking measures against PID, and the ground fault determination may be performed. Note that FIG. 2 illustrates the case where a p-type semiconductor is used for the bulk of the solar cell or the case where a solar cell using a transparent conductive film is used as an example. In Embodiment 7, the bulk of the solar cell is described. When an n-type semiconductor is used, the ground fault detection device 36 shown in FIG. 2 is connected to the positive electrode wiring of each solar cell string 12a. In other words, the terminal 80c of the changeover switch 80 of the ground fault detection device 36 shown in FIG. 2 is connected to P (+) of the ground fault detection device 36 shown in FIG. -) Nothing is connected to the side. At this time, the DC power supply 91 is arranged so that the positive electrode side is connected to the terminal 80b of the changeover switch 80, and is arranged so that a positive potential can be applied to the positive electrode wiring of each solar cell string 12a.

Similarly, in the seventh embodiment, when the ground fault detection device 36 described in FIG. 3 (the third embodiment) is used, N (−) of the ground fault detection device 36 in FIG. This corresponds to the point 50, and nothing is connected to the P (+) side of the ground fault detection device 36 in FIG. That is, when the ground fault detection device 36 shown in FIG. 3 is used in the seventh embodiment, the wiring branched from the positive electrode wiring of each of the solar cell strings 12a to 12c becomes unnecessary. In this case, during normal operation, the switch devices 33a to 33c are turned on (closed), the changeover switch 80 in the ground fault detection device 36 is connected to the terminal 80a (that is, connected to the first ground circuit), and PID Take measures. Further, ground fault detection is periodically performed for each of the solar cell strings a to c. Specifically, first, the solar cell string (for example, the solar cell string 12a) to be inspected is disconnected from the system by the switch devices 103a and 103b (the other switch devices 103c to 103f are turned on (closed)). To do). Then, the switch device 33a is turned on (closed) to connect the solar cell string 12a to the ground fault detection device 36 (the other solar cell strings 12b and 12c are separated from the ground fault detection device 36 by the switch devices 33b and c). In this state, the changeover switch 80 in the ground fault detection device 36 is used to switch and connect the first grounding circuit and the second grounding circuit to the solar cell string 12a to be inspected. The ground fault is detected by measuring the voltage drop value of the resistor 84 in the potential state. In addition, it is good also as a structure which always monitors a voltage with the voltage monitoring part 86, taking a PID countermeasure, and performing a ground fault determination. Note that FIG. 3 illustrates the case where a p-type semiconductor is used for the bulk of the solar cell or the case where a solar cell using a transparent conductive film is used as an example. In Embodiment 7, the bulk of the solar cell is described. When an n-type semiconductor is used, the ground fault detection device 36 shown in FIG. 3 is connected to the positive electrode wiring of each solar cell string 12a. In other words, the terminal 80c of the changeover switch 80 of the ground fault detection device 36 shown in FIG. 2 is connected to P (+) of the ground fault detection device 36 shown in FIG. -) Nothing is connected to the side.

Further, in the seventh embodiment, when the ground fault detection device 36 described in FIG. 4 (the fourth embodiment) is used, N (−) of the ground fault detection device 36 in FIG. 50, and P (+) of the ground fault detection device 36 in FIG. 7 corresponds to the positive electrode side connection point 51 shown in FIG. In this case, during normal operation, the switch devices 33a to 33c are turned on (closed), the ground fault detector 36 is connected to the negative wiring of each of the solar cell strings 12a to 12c, and the switch devices 31a to 31c are turned off (open). ) To disconnect the ground fault detector 36 and the positive electrode wiring of each of the solar cell strings 12a to 12c. In this state, the negative switch wiring of each of the solar cell strings 12a to 12c is connected to the resistor 84 (connected to the first ground circuit) by the changeover switch 80 in the ground fault detection device 36, and PID countermeasures are taken. Further, ground fault detection is periodically performed for each of the solar cell strings a to c. Specifically, first, the solar cell string (for example, the solar cell string 12a) to be inspected is disconnected from the system by the switch devices 103a and 103b (the other switch devices 103c to 103f are turned on (closed)). To do). Then, the switch device 33a and the switch device 31a are turned on (closed) to connect the solar cell string 12a to the ground fault detection device 36 (the other solar cell strings 12b and c are the switch devices 33b and c and the switch devices 31b and c). To disconnect from the ground fault detection device 36). In this state, the changeover switch 80 in the ground fault detection device 36 is used to switch and connect the first grounding circuit and the second grounding circuit to the solar cell string 12a to be inspected. The ground fault is detected by measuring the voltage drop value of the resistor 84 in the potential state. During normal operation, the voltage monitoring unit 86 may constantly monitor the voltage while taking countermeasures against PID to determine the ground fault.

Further, in the seventh embodiment, when the ground fault detection device 36 described in FIG. 5 (the fifth embodiment) is used, N (−) of the ground fault detection device 36 in FIG. 50, and nothing is connected to the P (+) side of the ground fault detection device 36 in FIG. That is, when the ground fault detection device 36 shown in FIG. 5 is used in the seventh embodiment, the wiring branched from the positive electrode wiring of each of the solar cell strings 12a to 12c becomes unnecessary. In this case, the ground fault detection device 36 is always connected to the solar cell strings 12a to 12c. Therefore, in the seventh embodiment, when the ground fault detection device 36 shown in FIG. 5 is used, the switches 33a to 33c may be omitted. Note that FIG. 5 illustrates the case where a p-type semiconductor is used for the bulk of the solar cell or the case where a solar cell using a transparent conductive film is used as an example. When an n-type semiconductor is used, the ground fault detection device 36 shown in FIG. 5 is connected to the positive electrode wiring of each solar cell string 12a. In other words, the DC power source 92 shown in FIG. 5 is connected to P (+) of the ground fault detection device 36 shown in FIG. 7, and nothing is connected to the N (−) side of the ground fault detection device 36 in FIG. It becomes a state. At this time, the DC power source 92 is arranged so that the negative electrode side is connected to the positive electrode wiring of each solar cell string 12a, and is arranged so that a negative potential can be applied to the positive electrode wiring of each solar cell string 12a.

Further, in the seventh embodiment, when the ground fault detection device 36 described in FIG. 6 (the sixth embodiment) is used, N (−) of the ground fault detection device 36 in FIG. 50, and nothing is connected to the P (+) side of the ground fault detection device 36 in FIG. That is, when the ground fault detection device 36 shown in FIG. 5 is used in the seventh embodiment, the wiring branched from the positive electrode wiring of each of the solar cell strings 12a to 12c becomes unnecessary. In this case, the ground fault detection device 36 is always connected to the solar cell strings 12a to 12c. Therefore, in the seventh embodiment, when the ground fault detection device 36 shown in FIG. 6 is used, the switches 33a to 33c may be omitted. 6 illustrates the case where a p-type semiconductor is used for the bulk of the solar cell or the case where a solar cell using a transparent conductive film is used as an example. In Embodiment 7, the bulk of the solar cell is described. When an n-type semiconductor is used, the ground fault detection device 36 shown in FIG. 6 is connected to the positive electrode wiring of each solar cell string 12a. In other words, the AC power supply 93 shown in FIG. 6 is connected to P (+) of the ground fault detection device 36 shown in FIG. 7, and nothing is connected to the N (−) side of the ground fault detection device 36 in FIG. It becomes a state.

By performing the switching operation as described above, the internal configuration of the ground fault detection device 36 according to the seventh embodiment is, for example, a circuit configuration using the switch 80, the resistor 84, and the voltage monitoring unit 86 illustrated in FIG. Is used, the voltage V1 can be measured during normal operation. And voltage V2 can be measured in the case of periodic ground fault detection. Therefore, ground fault detection similar to the content described in FIG. 1 can be performed.

As described above, in the seventh embodiment, a ground fault detection device (for example, the first to fourth embodiments) that performs ground fault detection using two kinds of grounding electric circuits, or a direct current voltage is applied to the solar cell. A ground fault detection device (for example, Embodiment 5) that detects the ground fault by controlling the ground potential of the entire battery to be positive (or negative), or by constantly changing the ground potential of the solar battery by applying an AC voltage. Using a grounding circuit in a ground fault detection device (for example, Embodiment 6) that performs ground fault detection, the negative electrode wiring (or positive electrode wiring) of each of the solar cell strings 12a to 12c is grounded during normal operation, and PID As a countermeasure, it is possible to reliably detect the ground fault of each of the solar cell strings 12a to 12c without a blind spot where it is difficult to detect the ground fault. That is, since the grounding circuit of the ground fault detection device is used, it is not necessary to add a new configuration for PID countermeasures, and ground fault detection can be reliably performed.

FIG. 9 is a configuration diagram showing the configuration of the photovoltaic power generation system in the eighth embodiment. 9 is the same as FIG. 7 except that the backflow prevention diode 46 is eliminated. Further, the contents other than those specifically described below are the same as those in the seventh embodiment.

The solar power generation system 100 as described above is operated as follows as a solar power generation method. During normal operation, the solar cell array 300 and the load device 400 are connected, and the ground potential at a predetermined point of each of the solar cell strings 12a to 12c is set to the positive or negative potential using the ground circuit in the ground fault detection device 36. In the state controlled to normal operation of solar power generation. Specifically, it operates as follows. The switch devices 102 and 103 and the switches 402 and 404 that are driven by control from a control system (not shown) are all ON (closed), and the switch devices 31 are all OFF (open). As for the switch device 33, the normal operation is performed in a state where only the switch device 33 for any one of the solar cell strings 12a to 12c is ON (closed). That is, during normal operation, the ground fault detection device 36 is connected to the negative electrode of any one of the solar cell strings 12a to 12c (for example, the solar cell string 12a) as a countermeasure against PID. In this state, the ground fault detection device 36 controls the ground potential of the solar cell string 12a, and executes PID countermeasures. For example, when the ground fault detection device 36 shown in FIG. 1 (Embodiment 1) is used, the first grounding electric circuit is connected to the solar cell string 12a by the changeover switch 80. Since the negative electrodes of the solar cell strings 12a to 12c are connected in parallel, all the solar cell strings 12a can be obtained by grounding the negative electrode of the solar cell string 12a via the first grounding circuit in the ground fault detection device 36. The ground potential of the negative electrodes c to c can be controlled to the ground potential. In the example of FIG. 9, the case where a p-type semiconductor is used for the bulk of the solar cell or a solar cell using a transparent conductive film is shown as an example. Therefore, the negative electrode wiring is grounded. When an n-type semiconductor is used for the bulk of the solar cell, it goes without saying that the positive electrode wiring is grounded. As described above, during normal operation of the system, the switch devices 31 and 33 use the grounding circuit of the ground fault detection device 36 to connect the ground potential at a predetermined point of the solar cell array 300 to the positive electrode (n-type in the bulk of the solar cell). When a semiconductor is used, the potential is controlled to the negative electrode). Thereby, the negative electrode of each solar cell string 12a-c can be controlled to ground potential, and the PID phenomenon can be avoided.

As described above, by turning on (closing) only the switch device 33 for one of the solar cell strings 12a to 12c, the backflow from the other solar cell strings 12a to 12c can be eliminated. Therefore, the backflow prevention diode 46 can be omitted.

FIG. 10 is a diagram for explaining the ground fault detection operation in the eighth embodiment. In the eighth embodiment, ground fault detection is performed for each solar cell string 12. For example, in the case of using the ground fault detection device 36 shown in FIG. 1 (Embodiment 1), the solar cell string 12 (for example, the solar cell string 12a) that is a target of ground fault detection at the time of ground fault detection. The switch device 103 (for example, the switch devices 103a and 103b) that is driven by the control from the control system that is not turned off is turned off (opened), and the solar cell string 12 that is the target of ground fault detection is disconnected from the system. After that, the switch device 31 that is driven by control from a control system (not shown) while the switch device 33 (for example, the switch device 33a) of the solar cell string 12 (for example, the solar cell string 12a) that is a target of ground fault detection is kept ON. (For example, the switch device 31a) is turned ON (closed), and the positive electrode side and the negative electrode side of the solar cell string 12 to be detected for ground fault are connected to the ground fault detection device 36. Further, the switch devices 31 and 33 of the solar cell string 12 that are not the targets of ground fault detection are both turned OFF.

By performing the switching operation as described above, the internal configuration of the ground fault detection device 36 according to the eighth embodiment is, for example, a circuit configuration using the switch 80, the resistor 84, and the voltage monitoring unit 86 illustrated in FIG. Is used, the voltage V1 can be measured during normal operation. And voltage V2 can be measured in the case of periodic ground fault detection. Therefore, ground fault detection similar to the content described in FIG. 1 can be performed.

As described above, in the eighth embodiment, it is possible to eliminate a blind spot where it is difficult to detect a ground fault for each solar cell string 12 while performing grounding for PID countermeasures.

FIG. 11 is a configuration diagram showing the configuration of the photovoltaic power generation system according to the ninth embodiment. In FIG. 11, the branch point of the wiring for branching from the negative electrode and the positive electrode of each of the ground fault detection device 36, each switch device 31, 33, and each solar cell string 12a-c and connecting to each switch device 31, 33 is shown. The position is between the switch device 102 on the negative electrode side and the position where the negative electrodes of the solar cell strings 12a to 12c are connected in parallel. On the positive electrode side, the diode 20 and the positive electrode of the solar cell strings 12a to 12c are connected in parallel. 9 is the same as FIG. 9 except that it has moved between the connected positions. The position of the branch point of the wiring for branching from the negative electrode and the positive electrode of each solar cell string 12a-c and connecting to each switch device 31, 33 is set to the position of FIG. Even when the negative electrode of c is grounded at the same time, the diode 46 can be omitted. Further, the contents other than those specifically described below are the same as those in the seventh embodiment.

The solar power generation system 100 as described above is operated as follows as a solar power generation method. During normal operation, the solar cell array 300 and the load device 400 are connected, and the ground potential at a predetermined point of each of the solar cell strings 12a to 12c is set to the positive or negative potential using the ground circuit in the ground fault detection device 36. In the state controlled to normal operation of solar power generation. Specifically, it operates as follows. The switch devices 102 and 103, the switch devices 33, and the switches 402 and 404 that are driven by control from a control system (not shown) are all ON (closed), and the switch devices 31 are all OFF (open). ), Normal operation is performed. That is, during normal operation, the ground fault detection device 36 is connected to the negative electrode of each of the solar cell strings 12a to 12c as a countermeasure against PID. In other words, during normal operation, the switch devices 31 and 33 intentionally control only the switch device 31 on the negative electrode side ON and turn off the switch device 33 on the positive electrode side to ground the negative electrode wiring. In the example of FIG. 11, a solar cell using a p-type semiconductor for the bulk of the solar cell or a transparent conductive film is shown as an example. Therefore, the negative electrode wiring is grounded. When an n-type semiconductor is used for the bulk of the solar cell, it goes without saying that the positive electrode wiring is grounded. Thus, the negative electrode of the photovoltaic power generation system 100 is in a state of being grounded via at least a part of the ground fault detection device 36 (negative electrode side circuit (not shown)). As described above, during normal operation of the system, the switch devices 31 and 33 use the grounding circuit of the ground fault detection device 36 to connect the ground potential at a predetermined point of the solar cell array 300 to the positive electrode (n-type in the bulk of the solar cell). When a semiconductor is used, the potential is controlled to the negative electrode). Thereby, the negative electrode of each solar cell string 12a-c can be controlled to ground potential, and the PID phenomenon can be avoided.

FIG. 11 is a diagram for explaining a ground fault detection operation in the ninth embodiment. In the ninth embodiment, ground fault detection is performed for each solar cell string 12. When the ground fault is detected, the switch device 103 (for example, the switch devices 103a and 103b) that is driven by the control from the control system (not shown) of the solar cell string 12 (for example, the solar cell string 12a) that is the target of the ground fault detection is turned off. (Open) and the solar cell string 12 to be subjected to ground fault detection is disconnected from the system. After that, the switch device 31 that is driven by control from a control system (not shown) while the switch device 33 (for example, the switch device 33a) of the solar cell string 12 (for example, the solar cell string 12a) that is a target of ground fault detection is kept ON. (For example, the switch device 31a) is turned ON (closed), and the positive electrode side and the negative electrode side of the solar cell string 12 to be detected for ground fault are connected to the ground fault detection device 36. Further, the switch devices 31 and 33 of the solar cell string 12 that are not the targets of ground fault detection are both turned OFF.

By performing the switching operation as described above, the internal configuration of the ground fault detection device 36 according to the ninth embodiment is, for example, a circuit configuration using the switch 80, the resistor 84, and the voltage monitoring unit 86 illustrated in FIG. Is used, the voltage V1 can be measured during normal operation. And voltage V2 can be measured in the case of periodic ground fault detection. Therefore, ground fault detection similar to the content described in FIG. 1 can be performed.

As described above, in the ninth embodiment, it is possible to eliminate a blind spot where it is difficult to detect a ground fault for each solar cell string 12 while performing grounding for PID countermeasures.

The embodiment has been described above with reference to specific examples. However, the present invention is not limited to these specific examples. The failure detection method described above is an example, and is not limited to the failure detection method described above. Any other fault detection method such as ground fault may be used as long as it is a ground fault detection method that intentionally controls the ground potential of the solar cell using a grounding circuit and determines the presence or absence of a ground fault without a blind spot.

In addition, although descriptions are omitted for parts that are not directly necessary for the description of the present invention, such as a device configuration and a control method, a required device configuration and a control method can be appropriately selected and used.

In addition, all photovoltaic power generation systems that include elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention.

One embodiment of the present invention relates to a solar power generation system and a solar power generation method, and can be used for, for example, a solar power generation system and method in which PID countermeasures are taken.

DESCRIPTION OF SYMBOLS 10 Solar cell module 12,502 Solar cell string 20,46 Diode 31,33,102,103 Switch apparatus 36 Detection part 40 Ground line 41,530 Grounding location 80,81 Changeover switch 83,84 Resistance 91 DC power supply 86 Voltage monitoring part 87 AC power supply 100 Photovoltaic power generation system 300 Solar cell array 400, 510 Load device 402, 404 Switch 500 Photovoltaic power generation system 600, 602 Ground fault location

Claims (12)

1. A power generation unit configured using one or more solar cell modules that generate power using sunlight, and a load that consumes or converts the power generated by the power generation unit while being insulated from the power generation unit or the ground. In a photovoltaic power generation system comprising a device, a ground fault detection device that detects a ground fault in the power generation unit,
   A first grounding circuit that is connected to a given location of the power generation unit and makes the ground potential of all locations of the power generation unit greater than or less than zero;
   A second grounding circuit for setting the ground potential of the power generation unit to a potential different from that when the first grounding circuit is connected;
   A potential control unit that controls the ground potential of the power generation unit by switching between the first grounding circuit and the second grounding circuit and connecting to the power generation unit,
   The potential control unit measures a measurement value based on a current flowing through the first grounding circuit connected to the power generation unit and a measurement value based on a current flowing through the second grounding circuit connected to the power generation unit. A ground fault detection unit that detects a ground fault of the power generation unit based on a measurement result,
   The electric potential control unit connects the first grounding electric circuit to the power generation unit during normal operation.
2. The first grounding circuit is configured to be connectable to one pole of the power generation unit, and the second grounding circuit is configured to be connectable to the other pole of the power generation unit. The ground fault detection apparatus of description.
3. The ground fault detection device according to claim 1, wherein the second grounding circuit has a DC power supply and applies a DC voltage to the power generation unit in a state of being connected to the power generation unit.
4. The ground fault detection device according to claim 1, wherein the second grounding circuit has an AC power supply and applies an AC voltage to the power generation unit in a state of being connected to the power generation unit.
5. The first grounding electric circuit is configured to be connectable to one pole of the power generation unit, and has a first resistance,
   2. The ground fault detection device according to claim 1, wherein the second grounding electric circuit is an electric circuit that is grounded at a midpoint obtained by dividing a voltage between a positive electrode and a negative electrode of the power generation unit with a given resistance.
6. 2. The solar power generation according to claim 1, wherein the ground fault detection unit detects a ground fault of the power generation unit using the ground wire in a state where the power generation unit and the load device are separated from each other. system.
   
7. A power generation unit configured using one or more solar cell modules that generate power using sunlight, and a load that consumes or converts the power generated by the power generation unit while being insulated from the power generation unit or the ground. In a photovoltaic power generation system comprising a device, a ground fault detection device that detects a ground fault in the power generation unit,
   One side is connected to the ground, and the other side can be connected to the positive or negative electrode of the power generation unit,
   Measuring a measured value based on the current flowing through the grounding circuit, and detecting a ground fault based on the measurement result,
   The ground fault circuit has a DC power source, and makes a ground potential in all locations of the power generation unit positive or negative.
8. The solar power generation according to claim 7, wherein the ground fault detection unit detects a ground fault of the power generation unit using the ground wire in a state where the power generation unit and the load device are separated. system.
9. A power generation unit configured using one or more solar cell modules that generate power using sunlight, and a load that consumes or converts the power generated by the power generation unit while being insulated from the power generation unit or the ground. In a photovoltaic power generation system comprising a device, a ground fault detection device that detects a ground fault in the power generation unit,
   One side is connected to the ground, and the other side can be connected to the positive or negative electrode of the power generation unit,
   Measuring a measured value based on the current flowing through the grounding circuit, and detecting a ground fault based on the measurement result,
   The grounding circuit has an AC power supply, and the ground potential of all locations of the power generation unit is time-averaged to be zero or more or zero or less.
10. The solar power generation according to claim 9, wherein the ground fault detection unit detects a ground fault of the power generation unit using the ground wire in a state where the power generation unit and the load device are separated. system.
11. A power generation unit configured using one or more solar cell modules that generate power using sunlight, and a load that consumes or converts the power generated by the power generation unit while being insulated from the power generation unit or the ground. The power generation unit and the load device are connected to each other, and ground potentials at all locations of the power generation unit are set to zero or more or zero or less using the first ground circuit. In this state, while performing normal operation of solar power generation, measure the measured value based on the current flowing through the first grounding circuit,
    A measured value based on the current flowing through the second grounding circuit in a state where the ground potential of the power generation unit is set to a potential different from that when the first grounding circuit is connected to the power generation unit using the second grounding circuit. Measure and
    Based on the measured value based on the current flowing through the first grounded electrical circuit connected to the power generating unit and the measured value based on the current flowing through the second grounded electrical circuit connected to the power generating unit, the ground fault of the power generating unit is determined. A photovoltaic power generation method characterized by detecting.
12. A power generation unit configured using one or more solar cell modules that generate power using sunlight, and a load that consumes or converts the power generated by the power generation unit while being insulated from the power generation unit or the ground. The power generation unit and the load device are connected to each other, and ground potentials at all locations of the power generation unit are set to zero or more or zero or less using the first ground circuit. In the state where
    In a state where the power generation unit and the load device are disconnected, the first grounding circuit is connected to the power generation unit, and a measurement value based on a current flowing through the first grounding circuit is measured.
    In a state where the power generation unit and the load device are disconnected, the second grounding circuit is connected to the power generation unit, and the ground potential of the power generation unit is different from that when the first grounding circuit is connected to the power generation unit. Measure the measured value based on the current flowing through the second ground circuit in the state of potential,
    Based on the measured value based on the current flowing through the first grounded electrical circuit connected to the power generating unit and the measured value based on the current flowing through the second grounded electrical circuit connected to the power generating unit, the ground fault of the power generating unit is determined. A photovoltaic power generation method characterized by detecting.

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