JP6547447B2 - Power recovery method for photovoltaic system and device therefor - Google Patents

Description

  The present invention relates to a method and apparatus for recovering power of a photovoltaic system, which recovers a reduction in power of a photovoltaic system including a photovoltaic string.

  A photovoltaic system includes solar cell strings, and each solar cell string is configured by connecting a number of solar cell modules in series. The direct current power generated by the solar cell string is converted to alternating current power by the power conditioner and supplied to the commercial power grid.

  As described above, it is known that in a solar cell string in which a large number of solar cell modules are connected in series and high-voltage power is output, a degradation phenomenon in which the amount of power generation is significantly reduced occurs, which is a PID (Potential Induced Degradation) phenomenon. It is done. Moreover, it is known that this PID phenomenon is eliminated by applying a voltage to a solar cell string as described in Patent Documents 1 and 2.

  Patent Document 1 describes that the solar cell is separated from the power conditioner, the positive electrode and the negative electrode of the solar cell are short-circuited, and a voltage for eliminating the PID phenomenon is applied between the positive electrode and the negative electrode and the earth. ing.

  Patent Document 2 describes that, during the nighttime, a DC high voltage of reverse bias that cancels out the PID phenomenon is applied between the positive electrode and the negative electrode of the solar cell.

  Further, Patent Document 3 describes a configuration in which a PID phenomenon is avoided and a ground fault is detected using an output current of a solar cell. Specifically, according to Patent Document 3, during normal operation of the solar power generation system, the ground potential at a predetermined point of the solar cell string is the potential of the positive electrode, and the negative electrode of each solar cell string has the same potential as the ground. It is described that the changeover switch is switched to avoid the PID phenomenon. Furthermore, during normal operation of the photovoltaic system, a ground fault of the solar cell string is detected, and in this case, the positive and negative poles of the solar cell string to be grounded are switched periodically by switching the switching switch. Is described.

  Further, Patent Document 4 describes a configuration provided with a power conditioner protection device that protects a power conditioner from the damage of lightning. The protection device detects lightning and thunder and controls the switching operation of the switch between the power conditioner and the solar cell array.

Unexamined-Japanese-Patent No. 2014-099438 (May 29, 2014 publication) JP, 2014-192443, A (October 6, 2014 publication) JP-A-2015-032602 (disclosed on February 16, 2015) JP, 2011-101557, A (May 19, 2011 release)

  However, in the above-described conventional configuration, a power supply device having a large capacity is required as a power supply device used to recover the output of the solar power generation system, and there is a problem that the cost is high.

  That is, in the configuration described in Patent Document 1, there is no definition of, for example, a time zone in which a voltage for eliminating the PID phenomenon is applied to the solar cell. Therefore, for example, in the case where the application of the voltage is performed during the daytime when the solar cell is generating electricity, a power supply device having a large capacity is required to eliminate the PID phenomenon. In this case, the power supply is expensive. In addition, no measures have been taken for dealing with the occurrence of a ground fault.

  In the configuration described in Patent Document 2, a voltage that eliminates the PID phenomenon is applied to the solar cell at night when the solar cell is not generating power, and this point reduces the capacity of the power supply device that outputs the voltage. Preferred above. However, as in the case of Patent Document 1, no countermeasure is taken into consideration when there is a ground fault, so the capacity of the power supply device that outputs the above voltage can not be reliably reduced. That is, when the solar cell is in a ground fault, a leakage current occurs, and a power source with a large capacity is required.

  The configuration described in Patent Document 3 is configured to avoid the PID phenomenon and detect a ground fault, but can not cope with the case where the PID phenomenon has occurred. Further, in the configuration described in Patent Document 4, the PID phenomenon is not considered.

  Therefore, the present invention can use a small-sized power supply device having a small capacity as a power supply device used to recover the output of the solar power generation system, and can provide a low-cost configuration of the solar power generation system. The purpose is to provide the device.

  In order to solve the above-mentioned subject, the output recovery device of the photovoltaics system of the present invention is an output recovery device of a photovoltaics system provided with a photovoltaic string and a power conversion device, wherein the output is applied to the photovoltaic strings. An output recovery unit that applies an output recovery voltage as a recovery operation, a ground fault detection unit that performs a ground fault inspection of the solar cell string, and connection of the solar cell string to the first side that is the power conversion device side A connection switching unit that switches between the power recovery unit and the second side that is the ground fault detection unit, and the power recovery operation possible state when the condition that the solar cell string does not have a ground fault is satisfied at least And the connection switching unit is switched to the first side when the electric power is output from the solar cell string to the power conversion device. The connection switching unit and the ground fault detection unit are controlled such that the connection switching unit is controlled, and in the case of the ground fault inspection, the connection switching unit is switched to the second side and the ground fault inspection is performed. When the output recovery operation is performed, the connection switching unit switches to the second side at the nearest night after the ground fault inspection when the output recovery operation is enabled, and the output recovery operation is performed. And a control unit that controls the connection switching unit and the output recovery unit.

  According to said structure, when outputting electric power from a solar cell string to a power converter device, a connection switch part switches to a 1st side. In the case of the ground fault inspection, the connection switching unit switches to the second side, and the ground fault detection unit performs the ground fault inspection of the solar cell string. When the power recovery operation of the solar cell string is performed, the power recovery unit applies the power recovery voltage to the solar cell string at the latest night after the ground fault inspection when the power recovery operation is possible.

  Therefore, when the power recovery unit performs the power recovery operation on the solar cell string, there is no situation where the power recovery unit having a large capacity power source is required because the solar cell string has a ground fault. . Thus, the output recovery unit may be provided with a small-sized power supply device having a small capacity, and can be configured at a low cost. In addition, since the power recovery operation of the solar cell string is performed at night immediately after the ground fault inspection when the power recovery operation is possible, the power recovery voltage is applied to the solar cell string in which the ground fault occurs. The possibility of doing so can be reduced.

  The above-mentioned output recovery device of the solar power generation system includes a second information acquisition unit that acquires second information indicating a fear of lightning strike, and the determination unit further determines the lightning strike due to the absence of the second information. If the condition that there is no fear of the above condition is satisfied, it may be determined that the output recovery operation is possible.

  When lightning strikes occur near the solar cell string, there is a risk that the lightning strike of the induced lightning may destroy the power recovery unit through the electric wire of the solar cell string.

  However, according to the above configuration, the power recovery operable state is a state in which there is no ground fault in the solar cell string and no fear of lightning strike, and in the power recovery operation, there is no ground fault in the solar cell string and fear of lightning strike Do it in the absence of Thus, the connection switching unit and the output recovery unit can be protected from lightning strikes. Moreover, the expensive (SPD: Serge Protection Device) which protects the power supply of an output recovery part can be omitted. In addition, in the case where an inexpensive relay with a low withstand current is used for the connection switching unit, in particular, it is possible to prevent the connection switching unit from being damaged by lightning and maintain reliability even with a low cost configuration. be able to.

  The output recovery device of the solar power generation system described above includes a first information acquisition unit configured to acquire first information indicating whether or not the ground fault testable state is such that the output voltage or the output current of the solar cell string is less than a predetermined threshold. The control unit may control the connection switching unit and the ground fault detection unit such that the ground fault inspection is performed when the first information indicates that the ground fault test is possible. It may be

  According to the above configuration, the connection switching unit is switched to the second side when the ground fault inspection is possible (early morning or evening) when the output voltage or the output current of the solar cell string is less than the predetermined threshold value A fault detection unit performs a fault test on the solar cell string.

  Therefore, an inexpensive relay with a low current resistance can be used for the connection switching unit, and the cost can be reduced.

  The output recovery device of the above solar power generation system includes at least one of a voltage detection unit that detects an output voltage of the solar cell string and a current detection unit that detects an output current of the solar cell string, and the ground fault inspection The possible state information acquisition unit acquires the first information from at least one of the voltage detection unit and the current detection unit, and the control unit determines that the nighttime information is the voltage detection unit and the current It is good also as composition acquired from at least one with a detection part.

  According to the above configuration, the ground fault testable state information acquisition unit acquires the first information from at least one of the voltage detection unit and the current detection unit, and the control unit detects the voltage indicating that it is nighttime Acquired from at least one of the unit and the current detection unit.

  Therefore, it is possible to obtain the first information and the information indicating that it is nighttime by using at least one of the voltage detection unit and the current detection unit that the solar power generation system normally includes. In this case, a clock and a table of intensely changing daytime specific to high latitude are not necessary, and the configuration can be low cost.

  A method of recovering power of a solar power generation system according to the present invention is a method of recovering power of a solar power generation system including a solar cell string and a power conversion device connected to the solar cell string, wherein A ground fault detection step of disconnecting from the conversion device and performing a ground fault inspection of the solar cell string, and a judgment step of judging that the power recovery operation is possible if at least the condition that the solar cell string has no ground fault is satisfied; An output recovery voltage for applying an output recovery voltage as an output recovery operation to the solar cell string in a state disconnected from the power conversion device immediately after the ground inspection step when the output recovery operation is enabled And a process.

  According to said structure, there exists an effect similar to the output recovery device of said solar power generation system.

  According to the configuration of the present invention, the output recovery unit may be provided with a small-sized power supply device having a small capacity, and can be configured at low cost. In addition, since the power recovery operation of the solar cell string is performed at night immediately after the ground fault inspection when the power recovery operation is possible, the power recovery voltage is applied to the solar cell string in which the ground fault occurs. The possibility of doing so can be reduced.

It is a circuit diagram showing composition of a solar energy power generation system provided with an output restoration device of an embodiment of the invention. FIG. 2 is a schematic circuit diagram showing the configuration of a PID recovery power supply unit shown in FIG. 1; It is a flowchart which shows operation | movement of the ground fault detection of the output-recovery apparatus shown in FIG. It is a graph which shows an example of the daily change of the open circuit voltage in the solar cell string shown in FIG. 1, and an electric power generation amount. It is a circuit diagram which shows the ground fault inspection state about the solar cell string of the test object in the solar energy power generation system shown in FIG. It is a flowchart which shows operation | movement of PID recovery of the output recovery apparatus shown in FIG. It is a circuit diagram which shows the PID recovery operation state about the solar cell string of the process target in the output recovery apparatus shown in FIG. It is a general | schematic circuit diagram which carries out the structure of the PID recovery power supply part with which the output recovery device of other embodiment of this invention is equipped.

First Embodiment
[Configuration of photovoltaic system]
Embodiments of the present invention will be described below based on the drawings. FIG. 1 is a circuit diagram showing a configuration of a solar power generation system provided with the power recovery device of the present embodiment.

  As shown in FIG. 1, the solar power generation system 1 includes a plurality of solar cell strings 11, a power recovery device 12, and a power conditioning system (power conversion device, hereinafter referred to as PCS) 13 as a power conversion device. . FIG. 1 shows a state in which the power generated by the solar cell string 11 is supplied to the PCS 13 and the power recovery device 12 is not in operation (power output state).

(Solar cell string 11)
The solar cell string 11 is configured by connecting in series a plurality of solar cell modules 21 such as 10 to 20, for example. Each solar cell module 21 includes a plurality of solar cells (not shown) connected in series, and is formed in a panel shape. Each solar cell string 11 is connected to the PCS 13 by the power conduction paths 23a and 23b. The power conduction paths 23 a and 23 b are provided for each solar cell string 11.

(Output recovery device 12)
The power recovery device 12 applies a PID recovery voltage (power recovery voltage) to the solar cell string 11 to recover the power of the solar cell string 11 whose power is reduced due to the PID phenomenon. To this end, the power recovery device 12 includes a power path switching switch (connection switching unit) 31, a ground fault detection switching switch (ground fault detection unit) 32, a PID recovery switching switch (output recovery unit) 33, and a ground fault detection device. (Ground fault detection unit) 34, PID recovery power supply unit (output recovery unit) 35, lightning sensor (second information acquisition unit) 36, PV current detection unit (current detection unit, ground fault testable state information acquisition unit) 37, A PV voltage detection unit (voltage detection unit, ground fault testable state information acquisition unit) 38, a control unit (determination unit) 39, and processing conduction paths 41a and 41b are provided.

  The power conduction path switching switch 31 is provided in the power conduction paths 23a and 23b corresponding to each solar cell string 11, and switches the connection of the solar cell string 11 between the PCS 13 side and the processing conduction paths 41a and 41b. The power conducting paths 23a and 23b are provided for each of the solar cell strings 11, whereas the processing conducting paths 41a and 41b are shared by the respective solar cell strings 11.

  The ground fault detection switch 32 turns on and off the connection between the processing current paths 41 a and 41 b and the ground fault detection device 34. The PID recovery switching switch 33 turns on and off the connection between the processing energization paths 41 a and 41 b and the PID recovery power supply unit 35.

  The power conduction path changeover switch 31, the ground fault detection changeover switch 32, and the PID recovery changeover switch 33 are, for example, relays, and the switching operation or the on / off operation is controlled by the control unit 39.

  The ground fault detection device 34 detects the presence or absence of a ground fault of the solar cell string 11, and when a ground fault occurs, detects the position of the ground fault of the solar cell string 11. In the detection of the presence or absence of the ground fault, the ground fault resistance value (insulation resistance value) between the solar cell string 11 and the ground point is determined, and the ground fault occurs when the obtained ground fault resistance value is smaller than the reference resistance value It is determined that The ground fault detection device 34 may be of a known configuration.

  The PID recovery power supply unit 35 is a power supply device that supplies a PID recovery voltage (output recovery voltage) that recovers the output of the solar cell string 11 whose output is reduced due to the PID phenomenon. In the present embodiment, as shown in FIG. 2, the PID recovery power supply unit 35 shorts the processing current paths 41a and 41b, that is, shorts the PN terminal of the solar cell string 11, and shorts the PN terminal and the ground. During this time, the PID recovery voltage is applied. FIG. 2 is a schematic circuit diagram showing the configuration of the PID recovery power supply unit 35. As shown in FIG.

  The lightning sensor 36 detects, for example, the presence or absence of the occurrence of lightning in the vicinity of the solar cell string 11 (presence or absence of the possibility of lightning). As the lightning sensor 36, one having a known configuration can be used.

  The PV current detection unit 37 is provided, for example, in the power conducting path 23a corresponding to each solar cell string 11, and detects the amount of current flowing through the power conducting path 23a, that is, the amount of current flowing from the solar cell string 11 to the PCS 13 Are output to the control unit 39. The PV voltage detection unit 35 detects the voltage between contacts (voltage between the PN terminals) of the solar cell string 11 and outputs the detection result to the control unit 39.

(Control unit 39)
The control unit 39 monitors the generated current of the solar cell string 11 detected by the PV current detection unit 34 and the generated voltage (inter-electrode voltage) of the solar cell string 11 detected by the PV voltage detection unit 35, Information on the power generation state of the solar cell string 11 is acquired.

  In addition, the control unit 39 acquires information on the presence or absence of a ground fault for each of the solar cell strings 11 detected by the ground fault detection device 34. Further, the control unit 39 acquires, from the lightning sensor 36, information (second information) on the presence or absence of the occurrence of lightning in the vicinity of the solar cell string 11.

  When acquiring information on the presence or absence of a ground fault for each solar cell string 11 from the ground fault detection device 34, the control unit 39 sequentially performs the ground fault detection by the ground fault detection device 34 for each solar cell string 11 in the early morning or the evening. The operations of the power conduction path changeover switch 31 and the ground fault detection changeover switch 32 are controlled so that the inspection of the fault is performed. Control unit 39 detects the amount of current flowing from solar cell string 11 to PCS 13 detected by PV current detection unit 37 in the early morning and the evening, and between the poles of solar cell string 11 detected by PV voltage detection unit 38. Based on at least one of the voltage.

  The control unit 39 detects the occurrence of lightning by the lightning sensor 36 at the latest night after the ground fault inspection with respect to the solar cell string 11 in which the ground fault is not generated as a result of the inspection by the ground fault detection device 34 If not, it controls the power path switching switch 31, the ground fault detection switch 32 and the PID recovery power supply 35 so that the PID recovery voltage is applied from the PID recovery power supply 35.

  The control unit 39 includes a storage unit 40, and stores various types of information in the storage unit 40, such as information on the inspection result of the presence or absence of the ground fault in the solar cell string 11.

[Operation of Output Recovery Device 12]
(Operation of ground fault inspection)
In the above configuration, the operation of the power recovery device 12 will be described below. FIG. 3 is a flowchart showing an operation of ground fault detection of the power recovery device 12. FIG. 4 is a graph showing an example of the daily change of the open circuit voltage and the amount of power generation in the solar cell string 11. FIG. 5 is a circuit diagram showing a ground fault inspection state of the solar cell string 11 to be inspected.

  The ground fault detection device 34 detects the presence or absence of a ground fault of the solar cell string 11 when the power generation state of the solar cell string 11 is a ground fault testable state and no lightning is generated in the vicinity of the solar cell string 11. inspect. Specifically, as shown in FIG. 4, the ground fault testable state is a state where the power generation amount (output current) of the solar cell string 11 is sufficiently small (for example, a state less than or equal to the standby current of PCS 13) (P part). Alternatively, while the output voltage (open circuit voltage) of the solar cell string 11 is in the process of falling, the power generation amount (output current) is sufficiently small (for example, less than or equal to the standby current of the PCS 13). (Part Q). Part P occurs in the early morning and part Q occurs in the evening. The range A indicates the operating time of the PCS 13.

  Further, the condition that the output voltage (open circuit voltage) of the solar cell string 11 is larger than zero may be added to the ground fault testable state. This makes it possible to conduct an inspection using the generated current of the solar cell string 11.

  Therefore, in the ground fault testable state described above, the value of the output voltage of the solar cell string 11 is less than the first threshold set to a value larger than zero and smaller than the average value of the output voltage in the operation time of the PCS 13 It meets the condition that there is. Further, the above ground fault testable condition satisfies the condition that the value of the output current of the solar cell string 11 is equal to or less than a second threshold set to a value smaller than the average value of the output current during the operation time of the PCS 13 There is.

  The first threshold may be, for example, one half of the average value of the output voltage of the solar cell string 11 during the operation time of the PCS 13. The second threshold may be, for example, one half of the average value of the output current of the solar cell string 11 during the operation time of the PCS 13.

  The control unit 39 determines whether the power generation state of the solar cell string 11 is in the ground fault testable state, that is, whether it is early morning or evening, regardless of the PV current detection unit 37 and the PV voltage detection unit 38. The determination may be made based on time information obtained by communication with a sunshine meter, a clock, or an external device.

  As shown in FIG. 1, in the normal operation state of the solar power generation system 1, the power conduction path switching switch 31 corresponding to each solar cell string 11 is switched to the PCS 13 side, and the ground fault detection switching switch 32 and the PID recovery switching The switch 33 is off (S11).

  The control unit 39 of the power recovery device 12 outputs the output voltage (first information) and the output current (first information) of the solar cell string 11 based on the detection results of the PV current detection unit 34 and the PV voltage detection unit 35. Is monitored (S12), it is determined whether the power generation state of the solar cell string 11 is the ground fault testable state (S13).

  As a result of the determination in S13, if the power generation state of the solar cell string 11 is the ground fault inspection enabled state, the control unit 39 acquires the detection result of the lightning sensor 36 (lightning information (second information)) (S14) ), It is determined whether or not lightning occurs near the solar cell string 11 (S15). The lightning information may be acquired not from the lightning sensor 36 but from, for example, local weather information.

  As a result of the determination in S15, if lightning is generated, the control unit 39 ends the process. On the other hand, if lightning is not generated, the control unit 39 switches the power conduction path changeover switch 31 corresponding to the inspection target solar cell string 11 to the processing conduction paths 41a and 41b as shown in FIG. 5 (S16) ). The order of the solar cell strings 11 to be inspected may be any order such as the order of arrangement of the solar cell strings 11 or the order in which the power generation state is in the ground fault testable state.

  Next, the control unit 39 turns on the ground fault detection switch 32 (S17, see FIG. 5). Thus, the solar cell string 11 to be inspected is connected to the ground fault detection device 34 via the process current paths 41a and 41b.

  Next, the ground fault detection device 34 inspects the solar cell string 11 to be inspected for the occurrence of the ground fault, and further detects the ground fault position when the ground fault occurs (S18).

  As a result of the inspection in S18, if there is a ground fault in the solar cell string 11 to be inspected (S19), the control unit 39 inspects the management device (not shown) of the photovoltaic power generation system 1 The occurrence of a ground fault in the target solar cell string 11 and the position of the ground fault are reported. Further, the storage unit 40 stores information such as the presence or absence of the occurrence of a ground fault and the ground fault position for the solar cell string 11 to be inspected (S20).

  Thereafter, the ground fault detection switch 32 is turned off (S21), and the process proceeds to S24. In S24, the control unit 39 determines whether the inspection for all the solar cell strings 11 is completed, and if the inspection is completed, the process is ended, while if the inspection is not completed, in S12 The process returns to S12 and the subsequent steps are repeated.

  On the other hand, as a result of the inspection in S18, if the ground fault does not occur in the solar cell string 11 to be inspected (S19), the control unit 39 turns off the ground fault detection switch 32 (S22).

  Next, the control unit 39 switches the power conduction path switching switch 31 corresponding to the solar cell string 11 to be inspected to the PCS 13 side (S23). As a result, the solar cell string 11 for which the ground fault inspection result is obtained in the ground fault inspection is connected to the PCS 13.

  Thereafter, in S24, it is determined whether the inspection on all the solar cell strings 11 is completed, and if the inspection is completed, the process is ended. On the other hand, if the inspection is not completed, the process returns to S12, and the operations after S12 are repeated. That is, the control unit 39 switches the power conduction path switching switch 31 corresponding to the next solar cell string 11 to be inspected to the processing conduction paths 41a and 41b, and turns on the ground fault detection switching switch 32. Hereinafter, in the same manner, the presence or absence of a ground fault of the solar cell string 11 is inspected.

  The operation of acquiring the lightning information in S14 and the operation of determining whether to continue or cancel the PID recovery operation (output recovery operation) according to the presence or absence of the lightning occurrence in S15 are the ground fault detection switch 32. In order to protect the PID recovery switch 33, although it is preferable to perform this, it is not an essential operation as a premise for performing the PID recovery operation.

  Further, the determination of the presence or absence of the occurrence of the ground fault in S19 is for determining whether or not the PID recovery operation is to be performed (if the occurrence of the ground fault is not performed, the PID recovery operation is performed). Therefore, from the viewpoint of reducing the capacity of the PID recovery power supply unit 35, that is, reducing the cost of the output recovery device 12, the threshold (ground fault resistance value, second threshold) when determining the presence or absence of a ground fault in S19 is The threshold value (ground fault resistance value, first threshold value) may be set higher than the threshold value when determining the presence or absence of a normal ground fault occurrence. For example, the first threshold is 400 kΩ, whereas the second threshold is 800 kΩ to 1 MΩ.

  Further, in the above process, only the solar cell string 11 in which the ground fault has not occurred is connected to the PCS 13 in S19 and S23. However, as described above, when it is configured to determine the presence or absence of the ground fault by the first and second threshold values, the solar cell whose ground fault resistance is equal to or greater than the first threshold value and less than the second threshold value The string 11 may also be connected to the PCS 13 after the ground fault inspection. However, the solar cell string 11 is not targeted for the PID recovery operation (not targeted for processing).

(PID recovery operation)
Next, the operation of the PID recovery for the solar cell string 11 by the power recovery device 12 will be described. This operation is performed at the early morning after the operation of detecting the ground fault for the solar cell string 11 or at the latest night after the evening.

  FIG. 6 is a flowchart showing an operation of the PID recovery of the power recovery device 12. FIG. 7 is a circuit diagram showing a PID recovery operation state of the solar cell string 11 to be processed.

  In power recovery device 12, when the power generation state of solar cell string 11 is the PID recovery enabled state (power recovery operable enabled state) and no lightning is generated near solar cell string 11, the previous ground fault occurs. As a result of the inspection, the PID recovery operation is performed on the solar cell string 11 to be processed which is the solar cell string 11 determined to have not generated a ground fault.

  The PID recovery operation may be performed on the solar cell string 11 whose output is reduced among the solar cell strings 11 in which the ground fault does not occur. Alternatively, it may be periodically performed on all solar cell strings 11 in which a ground fault has not occurred regardless of the decrease in output.

  In the present embodiment, the power recovery device 12 performs the PID recovery operation at night. Therefore, that the power generation state of the solar cell string 11 is in the state capable of PID recovery operation means that the output current of the solar cell string 11 detected by the PV current detection unit 37 and the sun detected by the PV voltage detection unit 38 The voltage between contacts of the battery string 11 is zero or almost zero.

  Therefore, control unit 39 can determine whether or not solar cell string 11 is in the state where the PID recovery operation is possible based on the outputs of PV current detection unit 37 and PV voltage detection unit 38. Note that the control unit 39 does not use the PV current detection unit 37 and the PV voltage detection unit 38 to determine whether the solar cell string 11 is in the state where the PID recovery operation is possible, that is, whether it is nighttime. Alternatively, the determination may be made based on time information obtained by communication with an external device.

  As shown in FIG. 1, in the normal operation state of the solar power generation system 1, the power conduction path switching switch 31 corresponding to each solar cell string 11 is switched to the PCS 13 side, and the ground fault detection switching switch 32 and the PID recovery switching The switch 33 is off (S31).

  The control unit 39 of the power recovery device 12 monitors the output voltage and output current of the solar cell string 11 based on the detection results of the PV current detection unit 34 and the PV voltage detection unit 35 (S32), thereby the solar cell string It is determined whether the power generation state of 11 is the PID recovery operation possible state (S33).

  As a result of the determination in S33, if the power generation state of the solar cell string 11 is the state where the PID recovery operation is possible, the control unit 39 acquires the detection result (lightning information) of the lightning sensor 36 (S34). It is determined whether or not lightning is generated in the vicinity (S35).

  As a result of the determination in S35, if lightning is generated, the control unit 39 ends the process. On the other hand, if lightning is not generated, as shown in FIG. 7, the control unit 39 moves the power conduction path changeover switch 31 corresponding to any of the solar cell strings 11 to be processed to the processing conduction paths 41a and 41b. Switch (S36).

  Next, the control unit 39 turns on the PID recovery switch 33 (S37, see FIG. 7). Thereby, the solar cell string 11 to be treated is connected to the PID recovery power supply unit 35 via the treatment current paths 41a and 41b.

  Next, the PID recovery power supply unit 35 applies a PID recovery voltage (output recovery voltage) to the processing target solar cell string 11 for a predetermined time (S38). The predetermined time for applying the PID recovery voltage is a time set to eliminate the PID phenomenon of the solar cell string 11.

  Next, the control unit 39 turns off the PID recovery switching switch 33 (S39), and switches the power conduction path switching switch 31 corresponding to the solar cell string 11 for which the PID recovery operation is completed to the PCS 13 side (S40). Thereafter, it is determined whether the PID recovery operation for all the solar cell strings 11 to be processed is completed (S41). As a result of the determination in S41, if the PID recovery operation for all the solar cell strings 11 to be processed is complete, the PID recovery operation is ended, while if the PID recovery operation is not completed, the process returns to S32. Repeat the processing after that.

  In the present embodiment, the PID recovery operation is sequentially performed on the solar cell strings 11 to be processed. However, the PID recovery operation may be performed simultaneously for all solar cell strings 11 to be processed. In this case, the power passage switching switch 31 corresponding to each solar cell string 11 is switched to the processing passage 41a, 41b side.

  In addition, the solar cell string 11 that could not be recovered by the PID recovery operation may not be connected to the PCS 13 after the PID recovery operation, and may remain disconnected from the PCS 13.

(Advantages of power recovery device 12)
As described above, when performing the PID recovery operation on each solar cell string 11 of the solar power generation system, the power recovery device 12 inspects each solar cell string 11 for the occurrence of a ground fault, and performs a ground fault. The PV recovery operation is not performed on the solar cell string 11 in which the V is generated (only the solar cell string 11 in which the ground fault is not generated is the target of the PID recovery operation).

  Therefore, when performing the PID recovery operation by applying the PID recovery voltage from the PID recovery power supply unit 35 to the solar cell string 11, the large capacity PID recovery power supply unit is generated because the solar cell string 11 has a ground fault. There will be no need for 35. As a result, the output recovery device 12 can use a small-sized power supply device with a small capacity as the PID recovery power supply unit 35, and can be configured at low cost.

  Moreover, the inspection of the ground fault with respect to each solar cell string 11 is performed when the power generation state of the solar cell string 11 is the ground fault testable state, that is, in the early morning or the evening. Therefore, an inexpensive relay with a low current resistance can be used as the power conduction path switching switch 31 for switching the solar cell string 11 from the PCS 13 to the processing conduction paths 41a and 41b.

  Furthermore, when lightning is generated in the vicinity of the solar cell string 11 (when there is a possibility of lightning), it is necessary to switch the solar cell string 11 from the PCS 13 side to the processing current paths 41a and 41b. That is, the ground fault inspection and the PID recovery operation which require the switching operation of the power conduction path changeover switch 31 are not performed. Thereby, when lightning strikes occur near the solar cell string 11, the electric lightning of the induced lightning is a solar cell by releasing the electric shock to the SPD (Surge Protection Device) provided in the conventional solar power generation system including the PCS 13. It is transmitted to the ground fault detection device 34, the PID recovery power supply unit 35, the power conduction path switching switch 31 and the like through the electric wire of the string 11, and avoiding the destruction of these components and measures against the shock of the output recovery device 12. Cost can be reduced. In particular, even in the case where an inexpensive relay with a low withstand current is used as the power conduction path switching switch 31, the power conduction path switching switch 31 can be protected from lightning strikes.

Second Embodiment
Another embodiment of the present invention will be described below based on the drawings. FIG. 8 is a schematic circuit diagram showing a configuration of the PID recovery power supply unit 35 provided in the output recovery device 12 of the present embodiment.

  In output recovery device 12 of the present embodiment, as shown in FIG. 8, PID recovery power supply unit 35 is configured to apply a PID recovery voltage between the P terminal and the N terminal of solar cell string 11. . The operation and other configurations of the power recovery device 12 are similar to those of the power recovery device 12 described above.

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

  Industrial Applicability The present invention can be used for an apparatus for recovering an output reduced due to a PID phenomenon of a photovoltaic power generation system comprising a photovoltaic string formed by connecting a plurality of photovoltaic modules in series.

DESCRIPTION OF SYMBOLS 1 Solar power generation system 11 Solar cell string 12 Power recovery device 13 Power conditioning system (power conversion device)
21 solar cell module 23a, 23b power conducting path 31 power conducting path changeover switch (connection switching unit)
32 Ground fault detection switch (ground fault detection unit)
33 PID Recovery Switch (Output Recovery Unit)
34 Ground fault detection device (ground fault detection unit)
35 PID Recovery Power Supply (Output Recovery)
36 Lightning sensor (second information acquisition unit)
37 PV current detection unit (current detection unit, ground fault testable state information acquisition unit)
38 PV voltage detection unit (voltage detection unit, ground fault testable status information acquisition unit)
39 Control unit (judgment unit)
41a, 41b process current path

Claims (5)

In a power recovery device of a photovoltaic power generation system comprising a solar cell string and a power conversion device,
An output recovery unit applying an output recovery voltage to the solar cell string as an output recovery operation;
A ground fault detection unit that performs a ground fault inspection of the solar cell string;
A connection switching unit that switches the connection of the solar cell string between a first side that is the power conversion device side and a second side that is the output recovery unit and the ground fault detection unit side;
A determination unit that determines that the power recovery operation is possible if the solar cell string satisfies at least the condition that there is no ground fault;
When outputting power from the solar cell string to the power conversion device, the connection switching unit is controlled so that the connection switching unit switches to the first side, and in the case of the ground fault inspection, the connection switching is performed. Control the connection switching unit and the ground fault detection unit so that the unit switches to the second side and the ground fault inspection is performed, and the output recovery operation is enabled when the output recovery operation is performed Control for controlling the connection switching unit and the output recovery unit such that the connection switching unit switches to the second side and the output recovery operation is performed at the nearest night after the ground inspection in a given case A power recovery device for a photovoltaic power generation system comprising: A second information acquisition unit that acquires second information indicating a fear of lightning strike;
The sunlight according to claim 1, wherein the determination unit further determines that the power recovery operation is possible when a condition that there is no fear of lightning strike is satisfied by the absence of the second information. Power recovery system for power generation system. The ground fault testable state information acquisition unit acquires first information indicating whether the ground fault testable state in which the output voltage or the output current of the solar cell string is equal to or less than a predetermined threshold value,
The control unit controls the connection switching unit and the ground fault detection unit such that the ground fault test is performed when the first information indicates that the ground fault test is possible. The power recovery device of the photovoltaic power system according to claim 1 or 2. A voltage detection unit that detects an output voltage of the solar cell string; and a current detection unit that detects an output current of the solar cell string,
The ground fault testable state information acquiring unit acquires the first information from at least one of the voltage detecting unit and the current detecting unit, and the control unit detects the voltage indicating that the nighttime is detected. The power recovery device of the photovoltaic power generation system according to claim 3, wherein the power recovery device is acquired from at least one of a part and the current detection part. In a power recovery method of a photovoltaic power generation system comprising a photovoltaic string and a power conversion device connected to the photovoltaic string,
A ground fault detection step of disconnecting the solar cell string from the power converter and performing a ground fault inspection of the solar cell string;
A determination step of determining that the power recovery operation is possible if the solar cell string is at least satisfied with the condition of no ground fault;
An output recovery process for applying an output recovery voltage as an output recovery operation to the solar cell string in a state disconnected from the power conversion device at the nearest night after the ground fault inspection process when the output recovery operation is enabled And a power recovery method of a photovoltaic system characterized by comprising.

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