JP6405932B2 - Ground fault detection device and ground fault detection method - Google Patents

Description

  The present invention relates to a ground fault detection device and a ground fault detection method for detecting a ground fault of a solar cell string.

  A solar power generation system that generates power using sunlight includes a solar cell string formed by connecting a plurality of solar cell modules in series. The electric power generated by the solar cell string is supplied to the electric power transmission network via a power conditioning system (hereinafter referred to as PCS).

  The solar cell string is in a floating state without being grounded, and a ground fault occurs when the insulation resistance is lowered for some reason. Therefore, conventionally, as disclosed in Patent Document 1, a solar power generation system is provided with a ground fault detection device that detects the occurrence of a ground fault.

JP 2012-119382 A (released on June 21, 2012)

  The PCS generally has a ground fault detection function, and stops operation when a ground fault occurs in the solar cell string. Therefore, when a ground fault occurs and the PCS stops, the PCS stop is notified by an alarm, and the operator rushes to the installation position of the solar cell string by the alarm and finds the ground fault position by a ground fault measuring device for repair. To do.

  However, the insulation state of the solar cell string is likely to change depending on the measurement timing even within one day. For example, when the wiring of the solar cell string is deteriorated in insulation due to aging, the wiring may temporarily come into contact with another member to cause a ground fault. Therefore, after a short time after the occurrence of the ground fault (after the worker rushes), the insulation state of the solar cell string changes, and it is difficult to specify the position of the ground fault. For this reason, even if an operator is dispatched based on the warning of the occurrence of a ground fault, the ground fault position cannot be specified and cannot be repaired. Or it takes a long time for repair. In this case, the solar power generation system cannot be restarted. Or it takes a long time to restart.

  On the other hand, Patent Document 1 describes a configuration that detects a ground fault and a configuration that enables detection of a ground fault location. However, even if a ground fault that does not always reproduce occurs, a configuration that can determine the position of the ground fault is not shown.

  Accordingly, an object of the present invention is to provide a ground fault detection device and a ground fault detection method that can determine the position of a ground fault even when a ground fault that is not always reproduced occurs in a solar cell string.

  In order to solve the above problems, a ground fault detection device of the present invention includes a solar cell string connected to a power conditioner and a power conditioner that stops due to the occurrence of a ground fault in the solar cell string. In a ground fault detection device including a ground fault measuring unit that detects a position of the ground fault of the solar cell string of a photovoltaic system, a stop detection unit that detects a stop of the power conditioner, and the stop detection unit include: And a control unit that operates the ground fault measuring unit when detecting the stop of the power conditioner.

  According to said structure, when a power conditioner stops, a ground fault measuring part operate | moves and detects the position of the ground fault of a solar cell string. Therefore, when the inverter is stopped due to the occurrence of a ground fault, the position of the ground fault is quickly detected. As a result, the position of the ground fault can be detected without inviting a situation in which the ground fault has been eliminated since the ground fault has been measured for a while after the occurrence of the ground fault. That is, even when a ground fault that does not always reproduce occurs in the solar cell string, the position of the ground fault can be obtained.

  Said ground fault detection apparatus WHEREIN: The said ground fault measuring part is good also as a structure which measures ground fault resistance further.

  According to said structure, when a power conditioner stops by generation | occurrence | production of a ground fault, in addition to the detection of the position of a ground fault, a ground fault resistance can be measured appropriately.

  Said ground fault detection apparatus is provided in the power supply path between the said solar cell string and the said power conditioner, and switches the connection of the said solar cell string between the said power conditioner and the said ground fault measuring part. A power energization path switching unit, wherein the control unit is configured to connect the solar cell string to the ground fault measurement unit when the stop detection unit detects a stop of the power conditioner. It is good also as a structure which controls a switching part.

  According to said structure, when a power conditioner stops, the connection of a solar cell string and a power conditioner is interrupted | blocked, and a solar cell string is connected to a ground fault measuring part. Thereby, the influence of a power conditioner is excluded and the ground fault of the solar cell string by a ground fault measuring part can be measured appropriately.

  Further, since the power conduction path switching unit performs the switching operation after the power conditioner is stopped, that is, after the amount of current flowing through the power conduction path is reduced, a small and inexpensive switching element having a low withstand voltage can be used.

  Said ground fault detection apparatus is equipped with the electric current detection part which detects the electric current which flows through the electric power supply path between the said solar cell string and the said power conditioner, The said stop detection part is the electric current which the said electric current detection part detects A state in which the amount of change in the decrease direction exceeds a predetermined threshold may be detected as a stop of the power conditioner.

  According to said structure, the stop of a power conditioner can be detected appropriately by detecting the electric current which flows through the electric power conduction path between a solar cell string and a power conditioner.

  In the above ground fault detection device, the stop detection unit may detect that the power conditioner has stopped receiving information indicating that the power conditioner has stopped from the power conditioner.

  According to the above configuration, the stop detection unit detects that the inverter has received information indicating that the inverter is stopped from the power conditioner, so that the inverter detects the power conditioner stop. It is not necessary to detect the stop of the controller, and the configuration can be simplified.

  Said ground fault detection apparatus is good also as a structure mounted in the said power conditioner. According to the above configuration, the ground fault detection device is mounted in advance in the power conditioner, for example, is provided in advance in the casing of the power conditioner, thus simplifying the configuration of the photovoltaic power generation system. be able to.

  The ground fault detection method of the present invention includes a solar battery string connected to a power conditioner, and a power conditioner that stops due to the occurrence of a ground fault in the solar battery string. In the ground fault detection method including a ground fault measurement step for detecting the position of the ground fault, the ground fault detection method includes a stop detection step for detecting a stop of the power conditioner, and the stop of the power conditioner is detected in the stop detection step. When detected, the ground fault measuring step is performed.

  According to said structure, there exists an effect similar to said ground fault detection apparatus.

  According to the configuration of the present invention, the position of the ground fault can be obtained even when a ground fault that does not always reproduce occurs in the solar cell string.

It is a block diagram which shows the solar energy power generation system provided with the ground fault detection apparatus of embodiment of this invention. It is a block diagram which shows the outline | summary of the structure which paid its attention to one solar cell string of the solar energy power generation system shown in FIG. It is a circuit diagram which shows the specific structure of the solar power generation system provided with the ground fault detection apparatus of embodiment of this invention corresponding to the structure of the solar power generation system shown in FIG. It is a flowchart which shows operation | movement of the ground fault detection apparatus shown in FIG. It is a graph which shows the relationship between time, the operating voltage of the solar cell string shown in FIG. 3, and the electric power generated by the solar cell string when a ground fault occurs. It is a graph which shows the relationship between the time when PCS stops at daytime, and the generated electric power of the solar cell string shown in FIG. FIG. 4 is a circuit diagram showing a state in a case where an interelectrode voltage Va-Vb is obtained in the photovoltaic power generation system shown in FIG. 3. FIG. 4 is a circuit diagram illustrating a state in which a first voltage used for measuring ground fault resistance is obtained in the photovoltaic power generation system illustrated in FIG. 3. FIG. 4 is a circuit diagram illustrating a state in which a second voltage used for measurement of ground fault resistance is obtained in the photovoltaic power generation system illustrated in FIG. 3. It is a circuit diagram at the time of rewriting the circuit of the photovoltaic power generation system at the time of calculating | requiring the 1st voltage shown in FIG. 8 to the circuit which paid its attention to the solar cell module, the 1st voltage, and the ground fault position. It is a circuit diagram at the time of rewriting the circuit of the photovoltaic power generation system at the time of calculating | requiring the 2nd voltage shown in FIG. 9 to the circuit which paid its attention to the solar cell module, the 2nd voltage, and the ground fault position. It is a block diagram which shows the structure of the solar energy power generation system provided with the ground fault detection apparatus of other embodiment of this invention. It is a block diagram which shows the structure of the solar energy power generation system provided with the ground fault detection apparatus of further another embodiment of this invention.

[Embodiment 1]
(Outline of solar power generation system)
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a solar power generation system 1 including a ground fault detection device 12 according to an embodiment of the present invention. In FIG. 1, the DC system wiring is indicated by a solid line, and the AC system wiring is indicated by a dotted line.

  As shown in FIG. 1, the photovoltaic power generation system 1 includes a plurality of solar cell strings 11, a ground fault detection device 12, a connection box 13, a DC current collector 14, a power conditioning system (hereinafter referred to as PCS) 15, an AC A current collector panel 16 and a power distribution board 17 are provided.

  The ground fault detection device 12 and the connection box 13 are provided for each solar cell string 11, and each solar cell string 11 is connected to the DC current collector panel 14 via the ground fault detection device 12 and the connection box 13. The DC current collector panel 14 collectively supplies power from the solar cell strings 11 obtained via the connection box 13 to a PCS (power conditioner) 15. The DC current collector board 14, the PCS 15, the AC current collector board 16, and the power distribution board 17 are connected in series in this order in the supply direction of the power generated by the solar cell string 11.

(Outline of the configuration focusing on one solar cell string 11)
FIG. 2 is a block diagram showing an outline of the configuration focusing on one solar cell string 11 of the photovoltaic power generation system 1 shown in FIG.

  As shown in FIG. 2, the solar cell string 11 is formed by connecting a plurality of solar cell modules 21 such as 10 to 20 in series. Each solar cell module 21 includes a plurality of solar cells (not shown) connected in series, and is formed in a panel shape. The ground fault resistance 22 is a resistance between the solar cell string 11 and the ground 23.

  When a ground fault occurs in the solar cell string 11, the resistance between the solar cell string 11 and the ground 23, that is, the ground fault resistance 22 extremely decreases. For this reason, the ground fault current flows in the loop of the solar cell string 11 → the ground fault resistance 22 → the ground 23 → the PCS 15 → the solar cell string 11.

  The PCS 15 includes a ground fault detection unit 24. The ground fault detector 24 detects the occurrence of a ground fault from the ground fault current flowing from the ground 23 into the PCS 15 via the AC system. The PCS 15 stops operation when a ground fault is detected by the ground fault detection unit 24.

  When the PCS 15 stops operation, power supply to the power system after the PCS 15 is stopped. For this reason, the electric current which flows from the solar cell string 11 to PCS15 falls rapidly. The ground fault detection device 12 detects this change in current (change in the amount of current exceeding a predetermined threshold in the current decreasing direction), and determines that the PCS 15 has stopped when this state is detected.

(Specific configuration of solar power generation system)
FIG. 3 is a circuit diagram showing a specific configuration of the solar power generation system 1 including the ground fault detection device 12 according to the embodiment of the present invention, corresponding to the configuration of the solar power generation system 1 shown in FIG. is there. FIG. 3 shows a state where the power generated by the solar cell string 11 is supplied to the PCS 15 and the ground fault detection device 12 is not performing a measurement operation (power output state).

  As shown in FIG. 3, the ground fault detection device 12 includes a power conduction path switching switch (power conduction path switching section) 31, a ground fault current detection circuit (ground fault measurement section) 32, a PV voltage detection circuit 33, and a current sensor 34. (Stop detection unit), controller (stop detection unit, ground fault measurement unit, control unit) 35, AC / DC power supply unit 36, inspection first energization path 37a, inspection second energization path 37b, and ground energization path 38 ing.

  The power supply path switching switch 31 switches the connection of the solar cell string 11 between the PCS 15 and the ground fault detection device 12. Specifically, the connection of the power conduction paths 25a and 25b, which are power output lines from the solar cell string 11, is switched between the PCS 15 side and the inspection first and second conduction paths 37a and 37b side.

  The ground fault current detection circuit 32 detects a ground fault current generated when a ground fault occurs in the solar cell string 11. For this purpose, the ground fault current detection circuit 32 includes an inspection first changeover switch 41, an inspection second changeover switch 42, an inspection third energization path 43, an inspection resistor R1, and voltage dividing resistors R2 to R5 that are protective resistors. Yes.

  The inspection first changeover switch 41 is connected to one end of the inspection third energization path 43, and the connection of one end of the inspection third energization path 43 is connected to the inspection first changeover switch 41. It switches between 37a and the earthing | grounding electricity supply path 38 currently earth | grounded. The inspection second changeover switch 42 is connected to the other end of the inspection third energization path 43, and the connection of the other end of the inspection third energization path 43 is connected to the inspection first changeover switch 41. Switching between the energization path 37b and the grounded energization path 38 that is grounded is performed.

  The inspection third energizing path 43 is provided with a detection resistor R1 and voltage dividing resistors R2 to R5 in series. The voltage dividing resistors R2 to R3 are provided between the detection resistor R1 and the inspection first changeover switch 41, and the voltage dividing resistors R4 to R5 are provided between the detection resistor R1 and the inspection second changeover switch 42. Yes. The voltage across the detection resistor R1 is input to the controller 35 via the comparator 39. It is assumed that the resistance value of the detection resistor R1 is lower than the resistance values of the voltage dividing resistors R2 to R5.

  The voltage dividing resistors R <b> 2 to R <b> 5 reduce the first and second voltages V <b> 1 and V <b> 2 generated at both ends of the detection resistor R <b> 1 to reduce the voltage input to the controller 35. Thus, the controller 35 can be configured by a microcomputer, and the ground fault detection device 12 can be miniaturized. Further, the voltage dividing resistors R2 to R5 are present in any of a circuit for obtaining the interelectrode voltage Va-Vb, a circuit for obtaining the first voltage V1, and a circuit for obtaining the second voltage V2. .

  The current sensor 34 is provided, for example, in the power conduction path 25a, and detects the amount of current flowing through the power conduction path 25a, that is, the amount of current flowing from the solar cell string 11 to the PCS 15.

  The PV voltage detection circuit 33 detects the interelectrode voltage Va-Vb (voltage between PN terminals) of the solar cell string 11. For this purpose, the PV voltage detection circuit 33 includes resistors R11 to R13 which are voltage-dividing resistors connected in series. For example, the voltage generated across the resistor R12 is input to the controller 35 via the comparator 40.

  The controller 35 is based on the generated current of the solar cell string 11 detected by the current sensor 34 and the generated voltage of the solar cell string 11 detected by the PV voltage detection circuit 33 (interelectrode voltage Va−Vb). The power generation amount of the solar cell string 11 is monitored. Further, the controller 35 monitors whether the PCS 15 is stopped during the operation of the PCS 15 as described above based on the current flowing through the power conduction path 25a detected by the current sensor 34.

  Furthermore, the controller 35 controls the switching operation of the power energizing path selector switch 31, the inspection first selector switch 41, and the inspection second selector switch 42, and the ground fault resistance and the ground when the ground fault occurs in the solar cell string 11 are controlled. Find the entanglement position. Moreover, the memory 45 which memorize | stores various information, such as a measurement result, is provided.

  In this case, the controller 35 causes the power energization path changeover switch 31 to be connected to the inspection first and second inspection energization paths 37a and 37b in the measurement operation of the ground fault detection device 12. The state is switched to.

  The controller 35 sets the inspection first changeover switch 41 to the inspection first energization path 37a and the inspection second changeover switch 42 to the inspection second energization path 37b (see FIG. 7), and detects the detection resistance. A voltage generated at both ends of R1 is acquired, and an interelectrode voltage Va-Vb that is a voltage between the positive and negative electrodes of the solar cell string 11 is obtained.

  Further, the controller 35 sets the inspection first changeover switch 41 to the inspection first energization path 37a and the inspection second changeover switch 42 to the ground energization path 38 (see FIG. 8), and sets the detection resistor R1. The first voltage V1 generated at both ends is acquired. Furthermore, the controller 35 sets the inspection first changeover switch 41 to the ground energization path 38 and the inspection second changeover switch 42 to the inspection second energization path 37b (see FIG. 9), and sets the detection resistor R1. The second voltage V2 generated at both ends is acquired. The controller 35 obtains the ground fault resistance (resistance value) and the ground fault position of the solar cell string 11 based on the acquired inter-electrode voltage Va-Vb and the first and second voltages V1, V2. Details thereof will be described later.

(Outline of operation of ground fault detection device)
In the above configuration, the operation of the ground fault detection device 12 will be described below. FIG. 4 is a flowchart showing the operation of the ground fault detection device 12. FIG. 5 is a graph showing the relationship between time and the operating voltage of the solar cell string 11 and the generated power of the solar cell string 11 when a ground fault occurs. FIG. 6 is a graph showing the relationship between the time when the PCS stops during the daytime and the generated power of the solar cell string.

  As shown in FIG. 5, the operating voltage of the solar cell string 11 rises to a predetermined voltage at 7:00, for example, and falls at 18:00. The generated power gradually rises (dotted line) later than the rising of the operating voltage, and gradually falls (two-dot chain line) prior to the falling of the operating voltage. On the other hand, the generated power suddenly falls (dotted line) when the PCS 15 stops. Similarly, as shown in FIG. 6, the generated power of the solar cell string 11 suddenly falls when the PCS 15 stops during the operation of the PCS 15, and the ground fault detection device 12 detects the ground fault resistance and the ground fault position. Is done.

  Here, the operating time zone (S11 in FIG. 4) of the PCS 15 is a time zone in which power equal to or higher than a predetermined value is obtained from the solar cell string 11. In FIG. 5, for example, from the rising point of the generated power (starting point of the dotted line). It is set in the range up to the time of falling (end of the two-dot chain line). Therefore, during the operation time zone of the PCS 15, a current of a predetermined value or more flows through the power conduction paths 25 a and 25 b between the solar cell string 11 and the PCS 15. In addition, during the operation time zone of the PCS 15, the PCS 15 operates if there is no problem such as a failure or an accident in the photovoltaic power generation system 1.

  Also, before the start of the PCS 15 operating time zone (S17 in FIG. 4), it is an early morning time zone, and after the end of the PCS 15 operating time zone (S17 in FIG. 4) is an evening time zone. In FIG. 5, before the start of the PCS 15 operating time period, the period from the rising point of PV power generation voltage (starting end of solid line indicating PV generation voltage) to the starting point of PV generation power (starting point of dotted line indicating PV generation power) Is the time zone. In addition, after the end of the PCS 15 operating time period, the PV power generation voltage falls from the time when the PV generated power falls (the end of the two-dot chain line indicating the PV generated power) (the end of the solid line indicating the PV generated voltage). ).

  Note that the operating time zone of the PCS 15, before the start of the operating time zone, and after the end of the operating time zone may be stored in the memory 45, for example. Alternatively, the controller 35 may determine from the current detected by the current sensor 34 and the voltage detected by the PV voltage detection circuit 33.

  As shown in FIG. 4, the controller 35 of the ground fault detection device 12 determines whether or not it is the operating time zone of the PCS 15 (S11), and if it is the operating time zone of the PCS 15, monitors whether or not the PCS 15 is stopped. (S12).

  As described above, the PCS 15 stops when a ground fault occurs during operation (during operation). When the PCS 15 is stopped, the current flowing through the power conduction paths 25a and 25b between the solar cell string 11 and the PCS 15 decreases rapidly. Therefore, the controller 35 determines whether the PCS 15 is operating and whether the PCS 15 is stopped during operation by monitoring the currents in the power supply paths 25a, 25b detected by the current sensor 34. Can do.

  Here, when the PCS 15 stops during the operation time zone of the PCS 15 (S13), the controller 35 of the ground fault detection device 12 connects the power conduction paths 25a and 25b to the inspection first and inspection second conduction paths 37a and 37b. Thus, the power energization path selector switch 31 is switched. Thereby, the power supply paths 25a and 25b from the solar cell string 11 to the PCS 15 are blocked (S14).

  Next, the ground fault detection device 12 measures the ground fault resistance 22 of the solar cell string 11 and detects the ground fault position (S15), and the measurement result is stored in the memory 45 of the controller 35 (S16).

  The measurement result stored in the memory 45 is transmitted from the controller 35 to, for example, a management device (not shown) of the photovoltaic power generation system 1 and displayed on a display device (not shown) of the management device. Also good. Alternatively, it may be displayed on a display device (not shown) of the ground fault detection device 12.

  On the other hand, if it is not the operating time zone of PCS15 in S11, it is determined whether the operating time zone of PCS15 is before the start or after the operating time zone of PCS15 is ended (S17).

  If the determination result in S17 is YES, the ground fault resistance and the ground fault position are detected as a pre-operation inspection or a post-operation inspection of the solar cell string 11 (PCS 15) by the operations of S14 to S16 described above. .

(Measurement operation of ground fault resistance)
FIG. 7 is a circuit diagram showing a state in the case of obtaining the interelectrode voltage Va-Vb in the photovoltaic power generation system 1 shown in FIG. FIG. 8 is a circuit diagram showing a state when the first voltage V1 is obtained in the photovoltaic power generation system 1 shown in FIG. FIG. 9 is a circuit diagram showing a state when the second voltage V2 is obtained in the photovoltaic power generation system 1 shown in FIG.

  In the ground fault detection device 12, when obtaining the interelectrode voltage Va−Vb, the controller 35 switches the power conduction path changeover switch 31 from the power output state shown in FIG. 3 to the power conduction path 25 a, as shown in FIG. 7. 25b is switched so as to be connected to the inspection first and second energization paths 37a and 37b. Thereby, the power supply paths 25a and 25b from the solar cell string 11 to the PCS 15 are blocked. In addition, the controller 35 connects the inspection first changeover switch 41 with one end of the inspection third energization path 43 to the inspection first energization path 37 a, and connects the inspection second changeover switch 42 with the other end of the inspection third energization path 43. Is switched to be connected to the inspection second energization path 37b.

  In this state, both positive and negative poles of the solar cell string 11 are connected via the detection resistor R1 and the voltage dividing resistors R2 to R5. Thereby, the voltage according to the resistance value of the detection resistor R1 when the voltage between the positive and negative of the solar cell string 11 is divided by the detection resistor R1 and the voltage dividing resistors R2 to R5 is generated at both ends of the detection resistor R1. This voltage is taken into the controller 35 via the comparator 39, and the controller 35 obtains the interelectrode voltage Va-Vb.

  Next, when obtaining the first voltage V1, as shown in FIG. 8, the controller 35 performs the first inspection in a state where the power conduction paths 25a and 25b are connected to the first and second conduction paths 37a and 37b. The changeover switch 41 is switched so that one end of the inspection third energization path 43 is connected to the inspection first energization path 37a, and the inspection second changeover switch 42 is switched to the ground energization path 38 of the other end of the inspection third energization path 43. Switch to be connected to.

  In this state, the positive electrode (P terminal) of the solar cell string 11 is grounded via the detection resistor R1 and the voltage dividing resistors R2 to R5. Thereby, at both ends of the detection resistor R1, the resistance value of the detection resistor R1 when the voltage between the positive electrode of the solar cell string 11 and the ground potential is divided by the detection resistor R1 and the voltage dividing resistors R2 to R5 is determined. The first voltage V1 is generated. The first voltage V1 is taken into the controller 35 via the comparator 39, and the controller 35 obtains the first voltage V1.

  Next, when obtaining the second voltage V2, as shown in FIG. 9, the controller 35 performs the first inspection in the state where the power conduction paths 25a and 25b are connected to the first and second conduction paths 37a and 37b. The changeover switch 41 is switched so that one end of the inspection third energization path 43 is connected to the ground energization path 38, and the other end of the inspection second energization path 43 is switched to the inspection second energization path 37b. Switch to be connected to.

  In this state, the negative electrode (N terminal) of the solar cell string 11 is grounded via the detection resistor R1 and the voltage dividing resistors R2 to R5. As a result, both ends of the detection resistor R1 correspond to the resistance value of the detection resistor R1 when the voltage between the negative electrode of the solar cell string 11 and the ground potential is divided by the detection resistor R1 and the voltage dividing resistors R2 to R5. A second voltage V2 is generated. The second voltage V2 is taken into the controller 35 via the comparator 39, and the controller 35 obtains the second voltage V2. Note that the order of obtaining the interelectrode voltage Va-Vb, the first voltage V1, and the second voltage V2 is not fixed.

Next, the controller 35 calculates the inter-electrode voltage Va-Vb, the first and second voltages V1, V2, and the total resistance value Rsum (= R1 + R2 + R3 + R4 + R5) of the inspection third conduction path 43 by the following equation:
Rleake = Rsum × | Va−Vb | ÷ | V1−V2 | −Rsum (1)
The resistance value Rleake is obtained.

(Ground fault position detection operation)
Moreover, the controller 35 calculates | requires the generation position (ground fault position) of a ground fault from ratio of the absolute value of 1st and 2nd voltage V1, V2. As an example, the solar cell string 11 is obtained by connecting five solar cell modules 31 in series, and the ground fault is the third solar cell modules 31 and 4 when viewed from the P terminal side of the solar power generation system 1. It is assumed that it occurs between the individual solar cell modules 31. Reference numeral 34 denotes the ground fault resistance 22 at the ground fault position.

In this case, when the circuit (see FIG. 8) of the photovoltaic power generation system 1 when the first voltage V1 is obtained is rewritten to a circuit that focuses on the solar cell module 31, the first voltage V1, and the ground fault position, as shown in FIG. become. Similarly, when the circuit (see FIG. 9) of the photovoltaic power generation system 1 when the second voltage V2 is obtained is rewritten to a circuit that focuses on the solar cell module 31, the second voltage V2, and the ground fault position, as shown in FIG. become. Therefore, the ratio between the absolute value of the first voltage V1 and the absolute value of the second voltage V2 is
| V1 |: | V2 | = 3: 2
Thus, the ground fault position can be obtained from this ratio.

  As described above, in the ground fault detection device 12 of the photovoltaic power generation system 1 according to the present embodiment, when the PCS 15 is stopped, there is a possibility of the occurrence of a ground fault. 11 is switched from the PCS 15 side to the ground fault detection device 12 side, and the ground fault resistance and the ground fault position are obtained.

  Therefore, when a ground fault occurs in the solar cell string 11, the ground fault resistance and the ground fault position can be immediately obtained, and the measurement result can be stored in the memory 45. As a result, the ground fault was measured for a while after the occurrence of the ground fault, so that the ground fault resistance and the ground fault position were obtained without causing the ground fault to be resolved. Can be repaired. That is, even when a ground fault that is not always reproduced occurs in the solar cell string 11, the position of the ground fault can be obtained, and the photovoltaic power generation system 1 can be restarted quickly.

  Further, since the power supply path changeover switch 31 performs the switching operation after the PCS 15 is stopped, that is, after the amount of current flowing through the power supply paths 25a and 25b is reduced, it is possible to use a small and inexpensive switching element with a low withstand voltage. it can.

  Moreover, since the ground fault detection apparatus 12 is an independent structure, it can attach later with respect to the solar power generation system which is not equipped with the ground fault detection apparatus 12 previously.

  Moreover, in the ground fault detection apparatus 12, the positive / negative of the solar cell string 11 is shown in all the switching patterns of the inspection first and inspection second changeover switches 41 and 42 shown in FIG. 3 and FIGS. The two poles are not short-circuited. That is, even in a switching pattern in which the positive and negative poles of the solar cell string 11 are connected, at least the detection resistor R1 is interposed between the positive and negative poles. Therefore, for example, even when a failure occurs such that the inspection first and second change-over switches 41 and 42 are welded at any one of the switching positions, a large current flows through the circuit of the photovoltaic power generation system 1 and the circuit is An excessive heat generation can be prevented.

  Further, when obtaining the ground fault resistance, the inter-electrode voltage Va-Vb and the first and second voltages V1, V2 are measured using a circuit including the same detection resistor R1 and the same voltage dividing resistors R2 to R5. It is like that. Therefore, it is possible to eliminate the occurrence of measurement errors due to differences in resistance values and temperature coefficients during the individual manufacturing of the detection resistor R1 and the voltage dividing resistors R2 to R5. Thereby, the resistance value of the ground fault resistance 22 can be measured accurately.

  As shown in FIG. 3, when the controller 35 is configured by a microcomputer, one input port is required for measuring the interelectrode voltage Va-Vb and the first and second voltages V1, V2. Well, the number of ports required for the controller 35 can be reduced.

  Further, since the voltage dividing resistors R2 to R5 are provided in series with the detection resistor R1, when the controller 35 is configured by a microcomputer, the voltage input to the controller 35 can be easily lowered to an appropriate voltage. it can.

  In addition, although this Embodiment showed about the example in which the ground fault detection apparatus 12 was provided for every solar cell string 11, it is not limited to this. That is, only one ground fault detection device 12 may be provided in the solar power generation system 1 and may be used by switching between the plurality of solar cell strings 11.

[Embodiment 2]
Another embodiment of the present invention will be described below with reference to the drawings. FIG. 12 is a block diagram illustrating a configuration of the solar power generation system 2 including the ground fault detection device 12 according to the embodiment of this invention.

  In the solar power generation system 1 described above, the ground fault detection device 12, that is, the controller 35 is configured to detect the stop of the PCS 15 by the change of the current sensor 34 and detect the ground fault of the solar cell string 11. However, instead of this, as shown in FIG. 12, the ground fault detection device 12 notifies the occurrence of the ground fault of the solar cell string 11 from the PCS 15 including the ground fault detection unit 24 (ground fault occurrence notification signal). ), That is, the ground fault of the solar cell string 11 may be detected by receiving information indicating the stop of the PCS 15.

  About another structure and operation | movement of the ground fault detection apparatus 12, it is the same as that of the above-mentioned solar power generation system 1. FIG. Note that the communication between the ground fault detection device 12 and the PCS 15 may be either wired or wireless.

  According to said structure, the ground fault detection apparatus 12 does not need to detect the stop of PCS15 itself, and can simplify a structure.

[Embodiment 3]
Still another embodiment of the present invention will be described below with reference to the drawings. FIG. 13 is a block diagram illustrating a configuration of the solar power generation system 3 including the ground fault detection device 12 according to the embodiment of this invention.

  In the solar power generation system 1 described above, the ground fault detection device 12 is provided independently. However, instead of this, the ground fault detection device 12 may have a configuration provided in the PCS 15 as shown in FIG. In this case, the ground fault detection device 12 is provided, for example, in the housing of the PCS 15. About another structure and operation | movement of the ground fault detection apparatus 12, it is the same as that of the above-mentioned solar power generation system 1. FIG. According to said structure, the structure of the solar power generation system 1 can be simplified.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used in the field of repairing and checking a ground fault that occurs in a photovoltaic power generation system that includes a photovoltaic string configured by connecting a plurality of photovoltaic modules in series.

DESCRIPTION OF SYMBOLS 1 Solar power generation system 11 Solar cell string 12 Ground fault detection apparatus 15 Power conditioning system (power conditioner)
21 solar cell module 22 ground fault resistance 25a power conduction path 25b power conduction path 31 power conduction path switch (power conduction path switching unit)
32 Ground fault current detection circuit (Ground fault measurement unit)
34 Current sensor (stop detection unit)
35 Controller (Stop detection unit, ground fault measurement unit, control unit)
37a Inspection first energization path 37b Inspection second energization path 38 Ground energization path 41 Inspection first changeover switch 42 Inspection second changeover switch 43 Inspection third energization path

Claims (5)

A ground for detecting a position of the ground fault of the solar battery string of a solar power generation system having a solar battery string connected to a power conditioner and a power conditioner that stops due to occurrence of a ground fault in the solar battery string In the ground fault detection device provided with the fault measurement unit,
A stop detection unit for detecting a stop of the inverter ;
And the control section,
A power supply path switching unit that is provided in a power supply path between the solar cell string and the power conditioner and switches connection of the solar cell string between the power conditioner and the ground fault measurement unit; ,
The control unit controls the power supply path switching unit so that the solar cell string is connected to the ground fault measurement unit when the stop detection unit detects a stop of the power conditioner,
The power supply path switching unit performs a switching operation after the power conditioner is stopped .   The ground fault detection device according to claim 1, wherein the ground fault measurement unit further measures ground fault resistance. A current detector that detects a current flowing through a power conduction path between the solar cell string and the power conditioner;
The stop detection unit, according to claim 1 or 2, characterized by detecting a state in which the amount of change in the decreasing direction of the current the current detection unit detects exceeds a predetermined threshold value as the stop of the power conditioner Ground fault detection device. The stop detection unit, the ground fault according to claim 1 or 2, characterized in that detecting the reception of the information to the effect that from the power conditioner showing a stop of the power conditioner as a stop of the power conditioner Detection device. A ground for detecting a position of the ground fault of the solar battery string of a solar power generation system having a solar battery string connected to a power conditioner and a power conditioner that stops due to occurrence of a ground fault in the solar battery string In the ground fault detection method comprising the fault measurement step,
A stop detection step of detecting a stop of the inverter ,
In the power supply path between the solar cell string and the power conditioner, the power supply path for switching the connection of the solar cell string between the power conditioner and the ground fault measuring unit that detects the position of the ground fault Switching step,
When the stop of the power conditioner is detected in the stop detection step, the connection is performed so that the solar cell string is connected to the ground fault measurement unit after the stop of the power conditioner in the power conduction path switching step. A ground fault detection method characterized by switching .

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