WO2021057037A1 - 一种光伏发电系统及方法 - Google Patents

一种光伏发电系统及方法 Download PDF

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Publication number
WO2021057037A1
WO2021057037A1 PCT/CN2020/090227 CN2020090227W WO2021057037A1 WO 2021057037 A1 WO2021057037 A1 WO 2021057037A1 CN 2020090227 W CN2020090227 W CN 2020090227W WO 2021057037 A1 WO2021057037 A1 WO 2021057037A1
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Prior art keywords
branch
power generation
generation system
photovoltaic power
insulation
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Application number
PCT/CN2020/090227
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English (en)
French (fr)
Inventor
高拥兵
王晨
林天散
胡杨
Original Assignee
华为技术有限公司
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Application filed by 华为技术有限公司 filed Critical 华为技术有限公司
Priority to EP20868782.2A priority Critical patent/EP4024641A4/en
Publication of WO2021057037A1 publication Critical patent/WO2021057037A1/zh
Priority to US17/701,940 priority patent/US20220216690A1/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S50/00—Monitoring or testing of PV systems, e.g. load balancing or fault identification
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H1/00—Details of emergency protective circuit arrangements
    • H02H1/0007—Details of emergency protective circuit arrangements concerning the detecting means
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/02—Details
    • H02H3/04—Details with warning or supervision in addition to disconnection, e.g. for indicating that protective apparatus has functioned
    • H02H3/042—Details with warning or supervision in addition to disconnection, e.g. for indicating that protective apparatus has functioned combined with means for locating the fault
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
    • H02H3/32—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors
    • H02H3/33—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers
    • H02H3/332—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers with means responsive to dc component in the fault current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
    • H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
    • H02H7/1213—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for DC-DC converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/20—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for electronic equipment
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/261—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations
    • H02H7/263—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations involving transmissions of measured values
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/16—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to fault current to earth, frame or mass
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
    • H02H3/32—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors
    • H02H3/33—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/40—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to ratio of voltage and current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
    • H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
    • H02H7/122—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for inverters, i.e. dc/ac converters
    • H02H7/1222—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for inverters, i.e. dc/ac converters responsive to abnormalities in the input circuit, e.g. transients in the DC input
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/10—Parallel operation of dc sources
    • H02J1/102—Parallel operation of dc sources being switching converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin

Definitions

  • This application relates to the field of photovoltaic power generation technology, and in particular to a photovoltaic power generation system and method.
  • Photovoltaic power generation is a technology that uses the photovoltaic effect of the semiconductor interface to convert light energy into electrical energy.
  • Photovoltaic power generation systems usually include photovoltaic units, power converters, inverters and other equipment.
  • MPPT Maximum Power Point Tracking
  • this application provides a photovoltaic power generation system and method, which can determine the DC branch with an insulation failure in the photovoltaic power generation system, so that measures can be taken in time for the DC branch with an insulation failure to eliminate potential safety hazards.
  • this application provides a photovoltaic power generation system, which includes an inverter, a controller, and at least two DC branches; each DC branch includes a DC-DC converter and a leakage current detection device.
  • the input end of the DC-DC converter is connected to the corresponding photovoltaic unit, and the output end of the DC-DC converter is connected to the input end of the inverter;
  • the DC-DC converter is used to convert the direct current output by the corresponding photovoltaic unit into DC-DC It is transmitted to the inverter;
  • the inverter is used to invert the direct current delivered by the DC-DC converter into alternating current;
  • the leakage current detection device is used to detect the leakage current of the DC branch where it is located, and send the leakage current to the controller.
  • the controller is used to determine the DC branch with insulation fault according to the magnitude and direction of the leakage current of each DC branch before the photovoltaic power generation system is running.
  • the controller is also used to determine that an insulation fault occurs in the DC branch when the leakage current of the DC branch exceeds the preset range when the photovoltaic power generation system is running.
  • the controller can determine the insulation failure according to the magnitude and direction of the leakage current of each DC branch DC branch.
  • the leakage current of the DC branch with the insulation failure will increase significantly. Therefore, when the leakage current of the DC branch exceeds the preset range, the controller can determine the DC Insulation failure occurs in the branch, so that measures can be taken in time for the DC branch with insulation failure to eliminate potential safety hazards.
  • the photovoltaic power generation system further includes an insulation resistance detection device.
  • the insulation resistance detection device is used to detect the insulation resistance value to the ground of the photovoltaic power generation system before the operation of the photovoltaic power generation system, and send the insulation resistance value to the ground to the controller.
  • the controller is used to determine that an insulation fault occurs in the photovoltaic power generation system when the insulation resistance to ground is less than the preset impedance range.
  • the leakage current detection device can detect the leakage current of each DC branch and send the leakage current to the controller so that the controller can according to the leakage current of each DC branch The size and direction of the DC branch determine the insulation fault.
  • the leakage current detection device is not required to detect the leakage current of each DC branch, so the detection efficiency of the insulation resistance can be improved.
  • each DC branch further includes: an input voltage detection device.
  • the input voltage detection device is used to detect the voltage to the ground of the input terminal of the DC-DC converter of the corresponding DC branch.
  • the controller is also used to determine that the corresponding DC branch has an insulation failure when the voltage to ground at the input end of the DC-DC converter is less than the preset input voltage range.
  • the controller can determine that an insulation failure DC branch has occurred according to the detection result of the input voltage detection device. It is also possible to compare and verify the obtained judgment conclusion with the judgment conclusion obtained by using the leakage current of the DC branch to further improve the accuracy of insulation fault detection.
  • each DC branch further includes: an output voltage detection device.
  • the output voltage detection device is used to detect the voltage to the ground of the output terminal of the DC-DC converter of the corresponding DC branch.
  • the controller is used to determine that the corresponding DC branch has an insulation failure when the voltage to the ground at the output end of the DC-DC converter is less than the preset output voltage range.
  • the controller can determine that an insulation failure DC branch has occurred according to the detection result of the output voltage detection device. It is also possible to compare and verify the obtained judgment conclusion with the judgment conclusion obtained by using the leakage current of the DC branch to further improve the accuracy of insulation fault detection.
  • each DC branch further includes: a breaking device.
  • the controller is also used to control the disconnection of the disconnecting device on the DC branch where the insulation fault occurs when it is determined that an insulation fault occurs in the DC branch, so as to realize the rapid isolation of the insulation fault.
  • the controller is further configured to control the occurrence of insulation after the disconnection device on the DC branch on which an insulation fault occurs is disconnected.
  • the DC-DC converter on the failed DC branch is shut down to protect the corresponding DC branch and facilitate fault maintenance.
  • the breaking device of each DC branch is integrated in the DC-DC converter, or the breaking of each DC branch is The device is integrated in the inverter.
  • the specific installation position of the segmentation device can be determined according to actual conditions, which is not specifically limited in this application.
  • the leakage current detection device of each DC branch is integrated in the corresponding DC-DC converter, or each The leakage current detection device of each DC branch is integrated in the inverter.
  • the specific location of the leakage current detection device can be determined according to the actual situation, which is not specifically limited in this application.
  • this application also provides a photovoltaic power generation system, which includes an insulation resistance detection device, an inverter, a controller, and at least two DC branches.
  • Each DC branch includes: DC-DC converter and breaking device.
  • the input end of the DC-DC converter is connected to the corresponding photovoltaic unit, and the output end of the DC-DC converter is connected to the input end of the inverter.
  • the DC-DC converter is used to convert the DC power output by the corresponding photovoltaic unit to the inverter after DC-DC conversion.
  • the inverter is used to invert the direct current delivered by the DC-DC converter into alternating current.
  • the insulation resistance detection device is used to detect the insulation resistance value to the ground of the photovoltaic power generation system before the operation of the photovoltaic power generation system, and send the insulation resistance value to the ground to the controller.
  • the controller is used to determine the insulation failure of the photovoltaic power generation system when the insulation resistance to ground is less than the preset impedance range; to control the disconnection of the breaking device in each DC branch in turn to determine the DC branch with insulation failure.
  • the insulation resistance detection device detects the insulation resistance value of the photovoltaic power generation system to the ground, and then can determine whether the photovoltaic power generation system as a whole has an insulation failure.
  • the controller can By sequentially controlling the disconnection of the breaking device in each DC branch to determine the DC branch with insulation failure, it can promptly encourage the insulation failure of the DC branch with insulation failure to eliminate potential safety hazards.
  • this application also provides a method for diagnosing insulation failure of a photovoltaic power generation system.
  • the photovoltaic power generation system includes: an inverter and at least two DC branches; each DC branch includes: a DC-DC converter and a leakage Current detection device; the input end of the DC-DC converter is connected to the corresponding photovoltaic unit; the output end of the DC-DC converter is connected to the input end of the inverter.
  • the method includes: controlling the DC-DC converter to perform DC-DC conversion on the DC power output by the corresponding photovoltaic unit and transmitting it to the inverter; controlling the inverter to invert the DC power delivered by the DC-DC converter into AC power; and receiving
  • the leakage current detection device detects the leakage current of the DC branch where it is located; before the photovoltaic power generation system is operated, the DC branch with insulation failure is determined according to the magnitude and direction of the leakage current of each DC branch; when the photovoltaic power generation system is running, When the magnitude of the leakage current of the DC branch exceeds the preset range, it is determined that the DC branch has an insulation fault.
  • the DC branch with insulation fault can be determined according to the magnitude and direction of the leakage current of each DC branch.
  • the method can determine the DC branch with an insulation fault before or during the operation of the photovoltaic power generation system, and then can control the DC branch with an insulation fault to stop working in time to isolate the insulation fault and eliminate potential safety hazards.
  • the method before determining the DC branch with an insulation fault according to the magnitude and direction of the leakage current of each DC branch, the method further includes: obtaining the insulation resistance value to the ground of the photovoltaic power generation system ; When the insulation resistance to ground is less than the preset impedance range, it is determined that the photovoltaic power generation system has an insulation failure.
  • the leakage current of each DC branch can be detected by the leakage current detection device, and the leakage current is sent to the controller, so that the controller can according to the magnitude and direction of the leakage current of each DC branch Determine the DC branch with insulation fault.
  • the leakage current detection device can be controlled to detect the leakage current of each DC branch, so the detection efficiency of the insulation resistance can be improved.
  • the method further includes: obtaining the voltage of the input terminal of the DC-DC converter of the corresponding DC branch with respect to ground; -When the voltage to the ground at the input of the DC converter is less than the preset input voltage range, it is determined that the corresponding DC branch has an insulation failure.
  • the controller can determine the occurrence of an insulation fault DC branch according to the detection result of the input voltage detection device, and can also compare and verify the obtained judgment conclusion with the judgment conclusion obtained by using the leakage current of the DC branch to further improve the accuracy of the insulation fault detection Sex.
  • the method further includes: obtaining the voltage of the output terminal of the DC-DC converter of the corresponding DC branch with respect to ground; When the voltage of the converter's output terminal to ground is less than the preset output voltage range, it is determined that the corresponding DC branch has an insulation fault.
  • the controller can determine the occurrence of an insulation fault DC branch according to the detection result of the output voltage detection device, and can also compare and verify the obtained judgment conclusion with the judgment conclusion obtained by using the leakage current of the DC branch to further improve the accuracy of insulation fault detection Sex.
  • each DC branch includes a disconnecting device, and the method further includes: when it is determined that the DC branch has an insulation fault, controlling the occurrence of insulation The breaking device on the faulty DC branch circuit is disconnected to realize the fast and effective isolation of the insulation fault.
  • the method further includes: after controlling the disconnection of the breaking device on the DC branch where the insulation fault occurs, controlling the occurrence of insulation The DC-DC converter on the failed DC branch is shut down to protect the corresponding DC branch and facilitate fault maintenance.
  • the present application also provides another method for diagnosing insulation failure of a photovoltaic power generation system
  • the photovoltaic power generation system includes: an insulation resistance detection device, an inverter, and at least two DC branches; each DC branch includes: DC-DC converter and breaking device; the input end of the DC-DC converter is connected to the corresponding photovoltaic unit; the output end of the DC-DC converter is connected to the input end of the inverter, the method includes: controlling the DC-DC conversion The inverter converts the DC power output by the corresponding photovoltaic unit to the inverter after DC-DC conversion; controls the inverter to invert the DC power delivered by the DC-DC converter into AC power; controls the insulation resistance detection device before the photovoltaic power generation system runs , To detect the insulation resistance to ground of the photovoltaic power generation system; when the insulation resistance to ground is less than the preset impedance range, determine that the photovoltaic power generation system has an insulation failure; to control the disconnection of each of the DC branches in turn to
  • the insulation resistance detection device detects the insulation resistance value of the photovoltaic power generation system to the ground, and then can determine whether the photovoltaic power generation system as a whole has an insulation failure.
  • the controller can By sequentially controlling the disconnection of the breaking device in each DC branch to determine the DC branch with insulation failure, it can promptly encourage the insulation failure of the DC branch with insulation failure to eliminate potential safety hazards.
  • Each DC branch of the photovoltaic power generation system provided in this application includes a DC-DC converter and a leakage current detection device, which can detect the leakage current of the DC branch where it is located, and send the detection result of the leakage current To the controller. Because when the photovoltaic power generation system has an insulation failure before operation, the leakage current of the normal DC branch will flow to the DC branch where the insulation failure occurs, so the magnitude of the leakage current of the DC branch where the insulation failure occurs is the leakage current of all normal DC branches.
  • the sum of the magnitude of the current, the direction of the leakage current of the DC branch with insulation failure is opposite to the direction of the leakage current of all normal DC branches, so the controller can determine the insulation failure according to the magnitude and direction of the leakage current of each DC branch DC branch.
  • the leakage current of the DC branch with the insulation failure will increase significantly. Therefore, when the leakage current of the DC branch exceeds the preset range, the controller can determine the DC The branch circuit has an insulation failure.
  • the photovoltaic power generation system provided in this application can determine the DC branch with insulation failure before or during operation, so as to take measures in time for the DC branch with insulation failure, for example, control the DC branch with insulation failure to stop working in time To isolate insulation faults and eliminate safety hazards.
  • Figure 1 is a schematic diagram of a photovoltaic power generation system
  • Figure 2 is a schematic diagram of a photovoltaic power generation system provided by an embodiment of the application.
  • FIG. 3 is a schematic diagram of another photovoltaic power generation system provided by an embodiment of the application.
  • FIG. 4 is a schematic diagram of another photovoltaic power generation system provided by an embodiment of the application.
  • FIG. 5 is a schematic diagram of still another photovoltaic power generation system provided by an embodiment of the application.
  • Fig. 6 is a schematic diagram of another photovoltaic power generation system provided by an embodiment of the application.
  • FIG. 7 is a schematic diagram of yet another photovoltaic power generation system provided by an embodiment of the application.
  • FIG. 8 is a schematic diagram of still another photovoltaic power generation system provided by an embodiment of the application.
  • FIG. 9 is a schematic diagram of another photovoltaic power generation system provided by an embodiment of the application.
  • FIG. 10 is a flowchart of a method for diagnosing insulation failure of a photovoltaic power generation system according to an embodiment of the application
  • FIG. 11 is a flowchart of yet another method for diagnosing insulation failure of a photovoltaic power generation system according to an embodiment of the application.
  • FIG. 1 is a schematic diagram of a photovoltaic power generation system.
  • the photovoltaic power generation system includes a photovoltaic unit 104, a DC-DC converter 102, and an inverter 103.
  • the DC-DC converter 102 is used to convert the DC power output by the corresponding photovoltaic unit 104 to the inverter 103 after DC-DC conversion.
  • the insulation resistance of the entire photovoltaic power generation system can be detected to determine whether the photovoltaic power generation system has an insulation failure.
  • the insulation resistance value of the photovoltaic power generation system decreases, and the photovoltaic power generation system can be shut down for troubleshooting.
  • this application provides a photovoltaic power generation system and method.
  • a leakage current detection device is added to each DC branch of the photovoltaic power generation system, which can detect the leakage current in each DC branch and The test result is sent to the controller.
  • the controller can determine the DC branch with insulation fault according to the magnitude and direction of the leakage current of each DC branch before the photovoltaic power generation system is running. It can also determine the DC branch with an insulation fault when the photovoltaic power generation system is running, when the leakage current of the DC branch exceeds When the preset range is set, it is determined that the DC branch has an insulation failure. Therefore, it is possible to determine the DC branch with an insulation failure in the photovoltaic power generation system, and then it is possible to control the DC branch with an insulation failure to stop working in time to isolate the insulation failure.
  • the DC branch with insulation failure is called the fault branch.
  • FIG. 2 is a schematic diagram of a photovoltaic power generation system provided by an embodiment of the application.
  • the photovoltaic power generation system includes an inverter 103, a controller (not shown in the figure) and at least two DC branches. That is, the number of DC branches can be greater than or equal to 2.
  • Each DC branch includes: a leakage current detection device 101 and a DC-DC converter 102.
  • the input end of the DC-DC converter 102 is connected to the corresponding photovoltaic unit 104, and the output end of the DC-DC converter 102 is connected to the input end of the inverter 103.
  • the DC-DC converter 102 is used to convert the DC power output by the corresponding photovoltaic unit 104 to the inverter 103 after DC-DC conversion.
  • the photovoltaic unit 104 of the embodiment of the present application may include one photovoltaic module, or multiple photovoltaic modules formed in series and parallel. For example, multiple photovoltaic modules are connected in series to form a photovoltaic string, and multiple photovoltaic strings are connected in parallel to form a photovoltaic. unit.
  • the specific number of photovoltaic modules is not specifically limited in the embodiments of the present application, and those skilled in the art can set it according to actual application scenarios.
  • the DC-DC converter 102 is used for power conversion, and may be specifically a Boost circuit, for example, to implement MPPT adjustment.
  • the inverter 103 is used to invert the direct current delivered by the DC-DC converter 102 into alternating current.
  • each DC branch is connected in parallel and then connected to the input end of the inverter 103 as an example. It can be understood that each DC branch can also be connected to different input ports of the inverter 103, and the parallel connection is realized inside the inverter 103.
  • the embodiments of this application do not make specific limitations.
  • the leakage current detection device 101 is used to detect the leakage current of the DC branch where it is located, and send the leakage current to the controller.
  • the leakage current detection device 101 detects the leakage current on the DC side.
  • the leakage current detection device 101 is located between the photovoltaic unit 104 and the DC-DC converter 102 as an example. It can be understood that the leakage current detection device 101 of each DC branch can also be integrated in the corresponding DC-DC converter. In the DC converter 102, or integrated in the inverter 103, it can also be separately provided, for example, connected between the DC-DC converter 102 and the inverter 103.
  • the leakage current detection device 101 when the leakage current detection device 101 is integrated in the corresponding DC-DC converter 102, the leakage current detection device 101 can be integrated in the input end of the DC-DC converter 102, or integrated in the output of the DC-DC converter 102 end.
  • the leakage current detection device 101 is located between the photovoltaic unit 104 and the DC-DC converter 102 as an example for description.
  • the leakage current detection device 101 is located in other positions, the working principle is similar, and the details are not repeated in the embodiment of the present application.
  • the leakage current detection device 101 is used to detect the current and leakage current of the positive output branch PV+ and the negative output branch PV- of the photovoltaic unit 104 in the DC branch before and during the operation of the photovoltaic power generation system.
  • the detection device 101 may use the difference between the current magnitude of the positive output branch PV+ and the current magnitude of the negative output branch PV- as the detection value of the leakage current, and then send the detection value I RCD of the leakage current to the controller. .
  • the controller determines the DC branch with insulation fault according to the magnitude and direction of the leakage current of each DC branch.
  • the controller can determine the DC with insulation failure according to the magnitude and direction of the leakage current of each DC branch Branch road. The following is an example.
  • DC branch 1-DC branch 5 Take the photovoltaic inverter system including the following five DC branches: DC branch 1-DC branch 5, where the PV1+ branch of DC branch 1 has an insulation failure as an example for illustration.
  • the leakage current detection value of each DC branch can be seen in the table 1.
  • the positive and negative signs in front of the leakage current detection value in the table represent the different directions of leakage current.
  • the leakage current of the normal DC branch will flow to the insulation failure.
  • the leakage current of the DC branch with insulation failure ie 40mA
  • the leakage current of the DC branch with insulation failure ie 40mA
  • the direction of the current is opposite to the direction of the leakage current of all normal DC branches. Therefore, the controller of the photovoltaic power generation system can determine the DC branch with insulation fault as the DC branch 1 according to the magnitude and direction of the leakage current of each DC branch.
  • the above values are only schematic descriptions. In actual detection, there may be relatively small discrepancies. For example, the sum of the absolute value of the leakage current of the branch with an insulation fault is approximately equal to the sum of the absolute value of the leakage current of the normal branch. .
  • the photovoltaic power generation system determines that there is no insulation failure before operation or the insulation failure has been eliminated, the photovoltaic power generation system can enter the operating state, but when the photovoltaic power generation system is in operation, the insulation failure may occur due to accidental collisions of humans and animals, rain and snow, etc.
  • the magnitude of the leakage current of the DC branch with an insulation failure will increase significantly, so it can be determined whether the DC branch has an insulation failure according to the magnitude of the leakage current of the DC branch.
  • the preset range of the leakage current of the DC branch when there is no insulation fault can be determined in advance.
  • the leakage current detection device 101 detects the leakage current of the DC branch in real time and The leakage current is sent to the controller, and the controller is also used to determine that the DC branch has an insulation failure when the magnitude of the leakage current of the DC branch exceeds a preset range.
  • the preset range can be set according to actual application scenarios, which is not specifically limited in the embodiment of the present application.
  • Each DC branch of the photovoltaic power generation system provided by the embodiment of the application includes a DC-DC converter and a leakage current detection device.
  • the leakage current detection device can detect the leakage current of the DC branch where it is located, and detect the leakage current. The result is sent to the photovoltaic power generation system controller. Because when the photovoltaic power generation system has an insulation failure before operation, the leakage current of the normal DC branch will flow to the DC branch where the insulation failure occurs, so the magnitude of the leakage current of the DC branch where the insulation failure occurs is the leakage current of all normal DC branches.
  • the sum of the magnitude of the current, the direction of the leakage current of the DC branch with insulation failure is opposite to the direction of the leakage current of all normal DC branches, so the controller of the photovoltaic power generation system can determine the magnitude and direction of the leakage current of each DC branch DC branch with insulation failure.
  • the leakage current of the DC branch with the insulation failure will increase significantly. Therefore, when the leakage current of the DC branch exceeds the preset range, the controller can determine the DC The branch circuit has an insulation failure.
  • the photovoltaic power generation system provided in the embodiments of the present application can determine the DC branch with an insulation fault before or during operation, and can control the DC branch with an insulation fault to stop working in time to isolate the insulation fault and eliminate potential safety hazards.
  • Each DC branch of the photovoltaic power generation system provided in the above embodiment includes a leakage current detection device, which can detect the leakage current of the corresponding DC branch before the photovoltaic power generation system is operated.
  • the embodiment of the application also provides a photovoltaic power generation system, which can detect the insulation resistance value of the photovoltaic power generation system to ground, and then can first determine whether the photovoltaic power generation system as a whole has an insulation failure, and when it is determined that the photovoltaic power generation system has an insulation failure, then According to the leakage current detected by the leakage current detection device, the DC branch where the insulation fault occurs is located. If there is no insulation fault, there is no need to locate the insulation fault based on the leakage current detected by the leakage current detection device, thereby improving work efficiency.
  • the following is a detailed description with reference to the drawings.
  • FIG. 3 is a schematic diagram of another photovoltaic power generation system provided by an embodiment of the application.
  • the photovoltaic power generation system further includes an insulation resistance detection device 105.
  • an insulation resistance detection device 105 for the description of the remaining parts, reference may be made to the foregoing embodiment, and this embodiment will not be repeated here.
  • each DC branch is connected in parallel, and then connected to the input end of the inverter 103, and the insulation resistance detection device 105 is connected to the DC bus of the photovoltaic power generation system as an example. That is, the insulation resistance detection device 105 can be an independent device. . It is understandable that the insulation resistance detection device 105 may also be integrated inside the inverter 103, or integrated inside the DC-DC converter 102, or integrated inside the photovoltaic unit 104, or placed outside the photovoltaic power generation system. Wherein, when the insulation resistance detection device 105 is integrated inside the DC-DC converter 102, the insulation resistance detection device 105 may be integrated at the input end or the output end of the DC-DC converter 102. The embodiment of the present application does not specifically limit the installation position of the insulation resistance detection device 105.
  • the photovoltaic power generation system When the photovoltaic power generation system has no insulation failure, the photovoltaic power generation system is insulated to the ground. When an insulation failure occurs in the photovoltaic power generation system, the insulation resistance to ground of the photovoltaic power generation system will decrease. Therefore, the preset impedance range of the photovoltaic power generation system when no insulation failure occurs can be determined in advance.
  • the impedance detection device 105 detects the ground insulation resistance value of the photovoltaic power generation system and sends the ground insulation resistance value to the controller.
  • the controller is also used to determine the insulation failure of the photovoltaic power generation system when the insulation resistance to ground is less than the preset impedance range.
  • the preset impedance range can be set according to actual application scenarios, and the embodiment of the present application does not specifically limit it here.
  • the photovoltaic power generation system provided in the embodiments of the present application also has an insulation resistance detection device, which can detect the insulation resistance value to ground of the photovoltaic power generation system and send the insulation resistance value to ground to the controller, thereby enabling the controller to set the insulation resistance value to ground.
  • an insulation resistance detection device which can detect the insulation resistance value to ground of the photovoltaic power generation system and send the insulation resistance value to ground to the controller, thereby enabling the controller to set the insulation resistance value to ground.
  • it is less than the preset impedance range it is determined that the photovoltaic power generation system has an insulation fault.
  • the leakage current of each DC branch can be detected by the leakage current detection device, and the leakage current is sent to the controller, so that the controller can according to the magnitude and direction of the leakage current of each DC branch Determine the DC branch with insulation fault.
  • the leakage current detection device is not required to detect the leakage current of each DC branch, so the detection efficiency of the insulation resistance can be improved.
  • the third embodiment of the present application also provides a photovoltaic power generation system, which can be based on the input end of the DC-DC converter.
  • the ground voltage or the output terminal-to-ground voltage further determines whether an insulation fault occurs in the DC branch to verify whether the insulation fault judged based on the leakage current is accurate, which will be described in detail below with reference to the drawings.
  • FIG 4 is a schematic diagram of yet another photovoltaic power generation system provided by an embodiment of the application.
  • each DC branch further includes an input voltage detection device 106.
  • each DC branch further includes an input voltage detection device 106.
  • the input voltage detection device 106 can be connected to the input end of the DC-DC converter 102, specifically can be integrated inside the DC-DC converter 102, or integrated inside the photovoltaic unit 104, or it can be installed separately, which is not used in this embodiment of the application. Specific restrictions.
  • the input voltage detection device 106 is used to detect the voltage to ground of the input terminal of the DC-DC converter 102 of the corresponding DC branch, which may specifically include the ground voltage of the positive input terminal and the ground voltage of the negative input terminal.
  • the input voltage detection device 106 The test result can also be sent to the controller.
  • the preset input voltage range of the DC branch when no insulation fault occurs can be predetermined.
  • the preset input voltage range may include a preset input voltage range corresponding to the positive input terminal and a preset input voltage range corresponding to the negative input terminal.
  • the controller compares the ground voltage of the positive input terminal detected by the input voltage detection device 106 with the preset input voltage range corresponding to the positive input terminal, and compares the ground voltage of the negative input terminal with the preset input voltage range corresponding to the negative input terminal .
  • the preset input voltage range can be set according to actual application scenarios, and the embodiment of the present application does not specifically limit it here.
  • the controller may compare the detected voltage with a preset value, such as a preset value, by inputting the voltage at the positive input terminal detected by the voltage detecting device 106 When it is 0, when the detected voltage is 0, it is judged that an insulation fault occurs between the positive input terminal and the ground.
  • the preset value is a positive value near 0, when the detected voltage is less than or equal to the preset value, it is determined that an insulation failure of the positive input terminal to the ground occurs.
  • the controller determines that the voltage to the ground of the input terminal of the DC-DC converter 102 is less than the preset input voltage range, it determines that the corresponding DC branch has an insulation failure. At this time, the controller can compare and verify the judgment conclusion with the judgment conclusion obtained by using the leakage current of the DC branch in the system embodiment 1, so as to improve the accuracy of insulation fault detection, which can effectively prevent the controller from misjudgment and effectively isolate Insulation failure.
  • FIG. 5 is a schematic diagram of yet another photovoltaic power generation system provided by an embodiment of the application.
  • each DC branch further includes an output voltage detection device 107.
  • the output voltage detection device 107 is connected to the output terminal of the DC-DC converter 102, and may be specifically integrated inside the DC-DC converter 102, or may be provided separately, and the embodiment of the present application does not specifically limit it.
  • the output voltage detection device 107 is used to detect the voltage to ground of the output terminal of the DC-DC converter 102 of the corresponding DC branch, which may specifically include the ground voltage of the positive output terminal and the ground voltage of the negative output terminal.
  • the output voltage detection device 107 The test result can also be sent to the controller.
  • the preset output voltage range of the DC branch when no insulation fault occurs can be predetermined.
  • the preset output voltage range may include a preset output voltage range corresponding to the positive output terminal and a preset output voltage range corresponding to the negative output terminal.
  • the controller compares the ground voltage of the positive output terminal detected by the output voltage detection device 107 with the preset output voltage range corresponding to the positive output terminal, and compares the ground voltage of the negative output terminal with the preset output voltage range corresponding to the negative output terminal .
  • the preset output voltage range can be set according to actual application scenarios, which is not specifically limited in the embodiment of the present application.
  • the controller determines that the voltage to the ground of the output terminal of the DC-DC converter 102 is less than the preset output voltage range, it determines that the corresponding DC branch has an insulation failure. At this time, the controller can compare and verify the judgment conclusion with the judgment conclusion obtained by using the leakage current of the DC branch in the system embodiment 1, so as to improve the accuracy of insulation fault detection, which can effectively prevent the controller from misjudgment and effectively isolate Insulation failure.
  • FIG. 6 is a schematic diagram of another photovoltaic power generation system provided by an embodiment of the application.
  • each DC branch further includes an input voltage detection device 106 and an output voltage detection device 107.
  • each DC branch further includes an input voltage detection device 106 and an output voltage detection device 107.
  • the photovoltaic power generation system adds voltage detection devices at the input and output ends of the DC-DC converter 102, so that the controller can be more accurate according to the detection results of the voltage detection devices at the input and output ends of the DC-DC converter 102 Determine the DC branch with an insulation failure.
  • the controller can compare and verify the obtained judgment conclusion with the judgment conclusion obtained by using the leakage current of the DC branch in the system embodiment 1, so as to further improve the accuracy of insulation fault detection, which can effectively prevent the controller from misjudgment, and then Can effectively isolate insulation faults.
  • each DC branch of the photovoltaic power generation system provided by the embodiment of the present application not only adds a leakage current detection device, but also adds a voltage detection device to at least one of the input and output ends of the DC-DC converter. , So that the controller can determine the occurrence of an insulation fault DC branch according to the detection result of the voltage detection device. It is also possible to compare and verify the obtained judgment conclusion with the judgment conclusion obtained by using the leakage current of the DC branch in the first embodiment of the system, so as to further improve the accuracy of insulation fault detection. Therefore, the photovoltaic power generation system provided by the embodiment of the present application can effectively prevent the controller from misjudgment, thereby improving the accuracy of insulation fault isolation.
  • the photovoltaic power generation system provided by the embodiment of the present application can determine the DC branch where the insulation fault occurs, the disconnection of the fault branch can be further controlled to achieve insulation fault isolation.
  • the power converter of the faulty branch can be controlled to shut down by the controller to isolate the insulation fault.
  • a breaking device can be added to each DC branch to isolate the insulation fault, which will be described in detail below with reference to the accompanying drawings.
  • FIG. 7 is a schematic diagram of another photovoltaic power generation system provided by an embodiment of the application.
  • each DC branch further includes a disconnecting device 108.
  • each DC branch further includes a disconnecting device 108.
  • the breaking device 108 is set at the output end of the DC-DC converter 102 and used as an independent device as an example. It can be understood that the breaking device 108 in actual application can also be set as an independent device in the DC-DC converter.
  • the input end of 102 is either integrated in the input end of the DC-DC converter 102, or integrated in the input end of the inverter 103, or integrated in the photovoltaic unit 104.
  • the breaking device 108 may also be integrated in the inverter 103.
  • the embodiment of the present application does not specifically limit the location of the breaking device 108 in the photovoltaic power generation system.
  • the controller is also used to control the disconnection of the disconnecting device 108 on the DC branch where the insulation fault occurs when it is determined that the DC branch has an insulation fault. After the disconnecting device 108 is disconnected, the faulty branch is disconnected, so the faulty branch cannot be connected.
  • the inverter 103 further realizes isolation of insulation faults.
  • controller controls the DC-DC converter 102 on the DC branch circuit where the insulation fault occurs to shut down after controlling the disconnection device 108 on the DC branch circuit where the insulation fault occurs.
  • FIG. 8 is a schematic diagram of yet another photovoltaic power generation system provided by an embodiment of the application.
  • the photovoltaic power generation system also includes an insulation resistance detection device 105, which can detect the insulation resistance to ground of the photovoltaic power generation system and send the insulation resistance to ground to the controller, so that the controller can make the insulation resistance to ground less than the preset impedance. In the range, it is determined that the photovoltaic power generation system has an insulation failure.
  • the leakage current of each DC branch can be detected by the leakage current detection device, and the leakage current is sent to the controller, so that the controller can according to the magnitude and direction of the leakage current of each DC branch Determine the DC branch with insulation fault.
  • the leakage current detection device is not required to detect the leakage current of each DC branch, so the detection efficiency of the insulation resistance can be improved.
  • Each DC branch of the photovoltaic power generation system not only adds a leakage current detection device, but also adds a breaking device.
  • the controller determines the DC branch with an insulation failure according to the detection result of the leakage current detection device, The controller can also control the disconnecting device of the DC branch with an insulation fault to disconnect, so as to realize the isolation of the insulation fault.
  • the leakage current of the DC branch can be detected by the leakage current detection device, and then the DC branch of the insulation fault can be determined by the controller.
  • the embodiment of the application also provides a photovoltaic power generation system.
  • Each DC branch includes a breaking device but not a leakage current detection device.
  • the controller controls each The breaking device in the DC branch is disconnected to determine the DC branch with insulation failure, which will be described in detail below with reference to the drawings.
  • FIG. 9 is a schematic diagram of another photovoltaic power generation system provided by an embodiment of the application.
  • the photovoltaic power generation system includes: an insulation resistance detection device 105, an inverter 103, a controller (not shown in the figure), and at least two DC branches. That is, the number of DC branches can be greater than or equal to 2.
  • each DC branch includes: a DC-DC converter 102 and a breaking device 108.
  • the input end of the DC-DC converter 102 is connected to the corresponding photovoltaic unit 104, and the output end of the DC-DC converter 102 is connected to the input end of the inverter 103.
  • the photovoltaic unit 104 of the embodiment of the present application may include one photovoltaic module, or multiple photovoltaic modules formed in series and parallel. For example, multiple photovoltaic modules are connected in series to form a photovoltaic string, and multiple photovoltaic strings are connected in parallel to form a photovoltaic. unit.
  • the specific number of photovoltaic modules is not specifically limited in the embodiments of the present application, and those skilled in the art can set it according to actual application scenarios.
  • the DC-DC converter 102 is used for power conversion, and may be specifically a Boost circuit, for example, to implement MPPT adjustment.
  • the DC-DC converter 102 performs DC-DC conversion on the DC power output by the corresponding photovoltaic unit 104 and transmits it to the inverter 103.
  • the inverter 103 is used to invert the direct current delivered by the DC-DC converter 102 into alternating current.
  • each DC branch is connected in parallel and then connected to the input end of the inverter 103 as an example. It can be understood that each DC branch can also be connected to different input ports of the inverter 103, and the parallel connection is realized inside the inverter 103.
  • the embodiments of this application do not make specific limitations.
  • the photovoltaic power generation system When the photovoltaic power generation system has no insulation failure, the photovoltaic power generation system is insulated to the ground. When an insulation failure occurs in the photovoltaic power generation system, the insulation resistance to ground of the photovoltaic power generation system will decrease. Therefore, the preset impedance range of the photovoltaic power generation system when no insulation failure occurs can be determined in advance.
  • the impedance detection device 105 detects the ground insulation resistance value of the photovoltaic power generation system and sends the ground insulation resistance value to the controller. The controller can determine that an insulation fault occurs in the photovoltaic power generation system when the insulation resistance value to the ground is less than the preset resistance range.
  • the controller can also determine the DC branch with insulation failure by sequentially controlling the disconnection device 108 in each DC branch to disconnect.
  • the breaking device disconnects the DC branch with an insulation fault, it is equivalent to achieving insulation fault isolation, and when the photovoltaic power generation system isolates the insulation fault, the photovoltaic power generation system restores its insulation to the ground. Therefore, if the breaking device disconnects the DC branch with an insulation fault, the detection result of the insulation resistance detection device will be restored to the preset impedance range.
  • the controller can sequentially control the disconnection of the breaking device in each DC branch, and then determine the DC branch with an insulation fault according to the detection result of the insulation resistance detection device after the breaking device is disconnected.
  • the photovoltaic power generation system detects the insulation resistance value of the photovoltaic power generation system to the ground through the insulation resistance detection device before the photovoltaic power generation system operates, and then can first determine whether the entire photovoltaic power generation system is insulated Fault, when it is determined that the photovoltaic power generation system has an insulation fault, the controller can determine the DC branch with the insulation fault by sequentially controlling the disconnection of the breaking device in each DC branch, and then can promptly check the DC branch with the insulation fault Encourage insulation failures to eliminate potential safety hazards.
  • an embodiment of the present application also provides a method for diagnosing insulation failure of a photovoltaic power generation system, which will be described in detail below with reference to the accompanying drawings.
  • FIG. 10 is a flowchart of a method for diagnosing insulation failure of a photovoltaic power generation system according to an embodiment of the application.
  • the photovoltaic power system includes: an inverter, a controller, and at least two DC branches.
  • Each DC branch includes: DC-DC converter and leakage current detection device.
  • the input end of the DC-DC converter is connected to the corresponding photovoltaic unit, and the output end of the DC-DC converter is connected to the input end of the inverter.
  • the DC-DC converter is used to convert the DC power output by the corresponding photovoltaic unit to the inverter after DC-DC conversion.
  • the inverter is used to invert the direct current delivered by the DC-DC converter into alternating current.
  • the leakage current detection device is used to detect the leakage current of the DC branch where it is located.
  • the leakage current detection device of each DC branch detects the leakage current of the DC branch and sends the detection result of the leakage current to the controller.
  • the leakage current of the normal DC branch will flow to the DC branch with the insulation fault. Therefore, the leakage current of the DC branch with the insulation fault is the sum of the leakage currents of all normal DC branches.
  • the direction of the leakage current of the DC branch with insulation failure is opposite to the direction of the leakage current of all normal DC branches. Therefore, the controller can determine the DC branch with insulation failure according to the magnitude and direction of the leakage current of each DC branch.
  • the leakage current of the DC branch with an insulation failure will increase significantly. Therefore, it can be determined whether the DC branch has an insulation failure according to the leakage current of the DC branch.
  • the preset range of the leakage current of the DC branch when there is no insulation fault can be pre-determined. After the photovoltaic power generation system enters the operating state, the leakage current detection device detects the leakage current of the DC branch in real time and sends the leakage current to Controller.
  • the controller is also used to determine that the DC branch has an insulation failure when the magnitude of the leakage current of the DC branch exceeds a preset range.
  • the preset range can be set according to actual application scenarios, and the embodiment of the present application does not specifically limit it.
  • the method for diagnosing the insulation fault of a photovoltaic power generation system can determine the DC branch with an insulation fault according to the magnitude and direction of the leakage current of each DC branch before the photovoltaic power generation system is operated.
  • the method can determine the DC branch with an insulation fault before or during the operation of the photovoltaic power generation system, and then can control the DC branch with an insulation fault to stop working in time to isolate the insulation fault and eliminate potential safety hazards.
  • the photovoltaic power generation system further includes an insulation resistance detection device
  • the following steps may also be included before S201:
  • the photovoltaic power generation system When the photovoltaic power generation system has no insulation failure, the photovoltaic power generation system is insulated to the ground. When an insulation failure occurs in the photovoltaic power generation system, the insulation resistance to ground of the photovoltaic power generation system will decrease. Therefore, the preset impedance range of the photovoltaic power generation system when no insulation failure occurs can be determined in advance.
  • the impedance detection device detects the ground insulation resistance value of the photovoltaic power generation system and sends the ground insulation resistance value to the controller.
  • the controller can determine that an insulation fault occurs in the photovoltaic power generation system when the insulation resistance value to the ground is less than the preset resistance range.
  • the leakage current of each DC branch can be detected by the leakage current detection device, and the leakage current is sent to the controller, so that the controller can according to the magnitude and direction of the leakage current of each DC branch Determine the DC branch with insulation fault.
  • the leakage current detection device can be controlled to detect the leakage current of each DC branch no longer, so the detection efficiency of the insulation resistance can be improved.
  • the method further includes the following steps:
  • the input voltage detection device detects the voltage to the ground of the input terminal of the DC-DC converter of the corresponding DC branch, which may specifically include the ground voltage of the positive input terminal and the ground voltage of the negative input terminal.
  • the input voltage detection device can also detect the result Send to the controller.
  • the preset input voltage range may include a preset input voltage range corresponding to the positive input terminal and a preset input voltage range corresponding to the negative input terminal.
  • the controller can compare the ground voltage of the positive input terminal detected by the input voltage detection device with the preset input voltage range corresponding to the positive input terminal, and compare the ground voltage of the negative input terminal with the preset input voltage range corresponding to the negative input terminal .
  • the controller can compare and verify the judgment conclusion with the judgment conclusion obtained by using the leakage current of the DC branch in S202 to improve the accuracy of the insulation fault detection, which can effectively prevent the controller from misjudgment and effectively isolate the insulation fault.
  • the method further includes the following steps:
  • the output voltage detection device detects the voltage to ground of the output terminal of the DC-DC converter of the corresponding DC branch, which can specifically include the ground voltage of the positive output terminal and the ground voltage of the negative output terminal.
  • the output voltage detection device can also detect the result Send to the controller.
  • the preset output voltage range may include a preset output voltage range corresponding to the positive output terminal and a preset output voltage range corresponding to the negative output terminal.
  • the controller compares the ground voltage of the positive output terminal detected by the output voltage detection device with the preset output voltage range corresponding to the positive output terminal, and compares the ground voltage of the negative output terminal with the preset output voltage range corresponding to the negative output terminal.
  • the controller can compare and verify the judgment conclusion with the judgment conclusion obtained by using the leakage current of the DC branch in S202 to improve the accuracy of the insulation fault detection, which can effectively prevent the controller from misjudgment and effectively isolate the insulation fault.
  • each DC branch of the photovoltaic power generation system further includes a breaking device
  • the method further includes the following steps:
  • the disconnecting device on the DC branch where the insulation fault has occurred is controlled to disconnect, so as to open the faulty branch, and then isolate the insulation fault.
  • the embodiment of the present application also provides a method for diagnosing the insulation fault of a photovoltaic power generation system, which can be applied to a photovoltaic power generation system that does not include a leakage current detection device in a DC branch, which will be described in detail below with reference to the accompanying drawings.
  • FIG. 11 is a flowchart of yet another method for diagnosing insulation failure of a photovoltaic power generation system according to an embodiment of the application.
  • the photovoltaic power generation system includes: an insulation resistance detection device, an inverter, a controller, and at least two direct current branches.
  • Each DC branch includes: DC-DC converter and breaking device.
  • the input end of the DC-DC converter is connected to the corresponding photovoltaic unit, and the output end of the DC-DC converter is connected to the input end of the inverter.
  • the DC-DC converter is used to convert the DC power output by the corresponding photovoltaic unit to the inverter after DC-DC conversion.
  • the inverter is used to invert the direct current delivered by the DC-DC converter into alternating current.
  • the insulation resistance detection device is used to detect the insulation resistance value of the photovoltaic power generation system to the ground before the photovoltaic power generation system runs, and send the detection result to the controller.
  • the method in this embodiment can be implemented by a controller, and the method provided in this embodiment includes the following steps:
  • the photovoltaic power generation system When the photovoltaic power generation system has no insulation failure, the photovoltaic power generation system is insulated to the ground. When an insulation failure occurs in the photovoltaic power generation system, the insulation resistance to ground of the photovoltaic power generation system will decrease. Therefore, the preset impedance range of the photovoltaic power generation system when no insulation failure occurs can be determined in advance.
  • the impedance detection device detects the ground insulation resistance value of the photovoltaic power generation system and sends the ground insulation resistance value to the controller.
  • the controller can determine that an insulation fault occurs in the photovoltaic power generation system when the insulation resistance value to the ground is less than the preset resistance range.
  • S302 Control the disconnection of the breaking device in each DC branch in turn to determine the DC branch with insulation fault.
  • the breaking device disconnects the DC branch with an insulation fault, it is equivalent to achieving insulation fault isolation, and when the photovoltaic power generation system isolates the insulation fault, the photovoltaic power generation system restores its insulation to the ground. Therefore, if the breaking device disconnects the DC branch with an insulation fault, the detection result of the insulation resistance detection device will be restored to the preset impedance range.
  • the controller can sequentially control the disconnection of the breaking device in each DC branch, and then determine the DC branch with an insulation fault according to the detection result of the insulation resistance detection device after the breaking device is disconnected.
  • the controller can determine the DC branch with an insulation fault by sequentially controlling the disconnection of the breaking device in each DC branch, and then can promptly check the occurrence of the insulation fault.
  • the DC branch with insulation failure shall be encouraged by insulation failure to eliminate potential safety hazards.
  • At least one (item) refers to one or more, and “multiple” refers to two or more.
  • “And/or” is used to describe the association relationship of associated objects, indicating that there can be three types of relationships, for example, “A and/or B” can mean: only A, only B, and both A and B , Where A and B can be singular or plural.
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Abstract

一种光伏发电系统及方法，涉及光伏发电技术领域。系统包括：逆变器（103）、控制器和至少两个直流支路。每个直流支路包括：DC-DC变换器（102）和漏电流检测装置（101）。其中，漏电流检测装置（101）用于检测所在的直流支路的漏电流，将漏电流发送给控制器；控制器用于在光伏发电系统运行前根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路；控制器还用于在光伏发电系统运行时，当直流支路的漏电流的大小超过预设范围时确定直流支路发生绝缘故障。利用该系统能够确定光伏发电系统出现绝缘故障的直流支路，以便于及时对出现绝缘故障的直流支路采取措施，排除安全隐患。

Description

一种光伏发电系统及方法
本申请要求于2019年9月24日提交中国专利局、申请号为201910905938.0、发明名称为“一种光伏发电系统及方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及光伏发电技术领域，尤其涉及一种光伏发电系统及方法。
背景技术
光伏发电是利用半导体界面的光生伏特效应，将光能转变为电能的一种技术。光伏发电系统通常包括光伏单元、功率变换器以及逆变器等设备。
随着光伏发电系统的输入容量配置越来越高，目前一般采用多路MPPT(Maximum Power Point Tracking，最大功率点跟踪)的方式扩大发电量，即逆变器的输入端包括多条直流支路，每条直流支路均包括光伏单元和功率变换器。
对于包括多条直流支路的光伏发电系统，某一处的绝缘故障会对光伏发电系统的运行和人畜的接触带来安全隐患，因此需要对光伏发电系统进行绝缘故障检测。可以通过检测光伏发电系统整体对地的绝缘阻抗值进而判断光伏发电系统是否出现绝缘故障。但当判断出光伏发电系统出现绝缘故障时，无法具体定位出现绝缘故障的直流支路，也无法做到在光伏发电系统运行前和运行时进行故障隔离。
申请内容
为了解决以上技术问题，本申请提供了一种光伏发电系统及方法，能够确定光伏发电系统出现绝缘故障的直流支路，以便于及时对出现绝缘故障的直流支路采取措施，排除安全隐患。
第一方面，本申请提供了一种光伏发电系统，该系统包括：逆变器、控制器和至少两个直流支路；每个直流支路包括：DC-DC变换器和漏电流检测装置。DC-DC变换器的输入端连接对应的光伏单元，DC-DC变换器的输出端连接逆变器的输入端；DC-DC变换器用于将对应的光伏单元输出的直流电进行直流-直流变换后传输给逆变器；逆变器用于将DC-DC变换器输送的直流电逆变为交流电；漏电流检测装置用于检测所在的直流支路的漏电流，将漏电流发送给控制器。控制器用于在光伏发电系统运行前，根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路。控制器还用于在光伏发电系统运行时，当直流支路的漏电流的大小超过预设范围时，确定直流支路发生绝缘故障。
由于当光伏发电系统在运行前出现绝缘故障时，正常直流支路的漏电流会流向出现绝缘故障的直流支路，因此出现绝缘故障的直流支路的漏电流的大小为所有正常直流支路漏电流大小的和，出现绝缘故障的直流支路的漏电流的方向与所有正常直流支路漏电流的方向相反，因此控制器可以根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路。当光伏发电系统在运行时出现绝缘故障时，出现绝缘故障的直流支路的漏电流大小会显著增大，因此当直流支路的漏电流的大小超过预设范围 时，控制器能够确定该直流支路发生绝缘故障，以便于及时对出现绝缘故障的直流支路采取措施，排除安全隐患。
结合第一方面，在第一种可能的实现方式中，该光伏发电系统还包括：绝缘阻抗检测装置。绝缘阻抗检测装置用于在光伏发电系统运行前，检测光伏发电系统的对地绝缘阻抗值，将对地绝缘阻抗值发送给控制器。控制器用于当对地绝缘阻抗值小于预设阻抗范围时确定光伏发电系统发生绝缘故障。
当绝缘阻抗检测装置确定光伏发电系统出现绝缘故障时，可以通过漏电流检测装置检测各直流支路的漏电流，并将漏电流发送给控制器，以使控制器根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路。而当确定光伏发电系统未出现绝缘故障时，则不需要漏电流检测装置检测各个直流支路的漏电流，因此能够提升绝缘阻抗的检测效率。
结合第一方面及上述任意一种实现方式，在第二种可能的实现方式中，每个直流支路还包括：输入电压检测装置。输入电压检测装置用于检测对应的直流支路的DC-DC变换器的输入端对地电压。控制器还用于在DC-DC变换器的输入端对地电压小于预设输入电压范围时，确定对应的直流支路发生绝缘故障。
通过在DC-DC变换器的输入端增加输入电压检测装置，以使控制器根据输入电压检测装置的检测结果确定发生绝缘故障直流支路。还可以将获取的判断结论与利用直流支路的漏电流获取的判断结论进行比较验证，以进一步提高绝缘故障检测的准确性。
结合第一方面及上述任意一种实现方式，在第三种可能的实现方式中，每个直流支路还包括：输出电压检测装置。输出电压检测装置用于检测对应的直流支路的所述DC-DC变换器的输出端对地电压。控制器用于在DC-DC变换器的输出端对地电压小于预设输出电压范围时，确定对应的直流支路发生绝缘故障。
通过在DC-DC变换器的输出端增加输出电压检测装置，以使控制器根据输出电压检测装置的检测结果确定发生绝缘故障直流支路。还可以将获取的判断结论与利用直流支路的漏电流获取的判断结论进行比较验证，以进一步提高绝缘故障检测的准确性。
结合第一方面及上述任意一种实现方式，在第四种可能的实现方式中，每个直流支路还包括：分断装置。控制器还用于在确定直流支路发生绝缘故障时，控制发生绝缘故障的所述直流支路上的分断装置断开，以实现绝缘故障的快速隔离。
结合第一方面及上述任意一种实现方式，在第五种可能的实现方式中，控制器还用于在控制发生绝缘故障的所述直流支路上的所述分断装置断开后，控制发生绝缘故障的所述直流支路上的所述DC-DC变换器关机，以保护对应的直流支路，便于故障维护。
结合第一方面及上述任意一种实现方式，在第六种可能的实现方式中，每个直流支路的分断装置集成在DC-DC变换器中，或，每个直流支路的所述分断装置集成在逆变器中。分段装置的具体设置位置可以根据实际情况确定，本申请对此不作具体限定。
结合第一方面及上述任意一种实现方式，在第七种可能的实现方式中，每个直流支路的所述漏电流检测装置集成在对应的所述DC-DC变换器中，或，每个直流支路的 所述漏电流检测装置集成在逆变器中。漏电流检测装置的具体设置位置可以根据实际情况确定，本申请对此不作具体限定。
第二方面，本申请还提供了一种光伏发电系统，该系统包括：绝缘阻抗检测装置、逆变器、控制器和至少两个直流支路。每个直流支路包括：DC-DC变换器和分断装置。DC-DC变换器的输入端连接对应的光伏单元，DC-DC变换器的输出端连接逆变器的输入端。DC-DC变换器用于将对应的光伏单元输出的直流电进行直流-直流变换后传输给逆变器。逆变器用于将DC-DC变换器输送的直流电逆变为交流电。绝缘阻抗检测装置，用于在光伏发电系统运行前，检测光伏发电系统的对地绝缘阻抗值，将对地绝缘阻抗值发送给控制器。控制器用于当对地绝缘阻抗值小于预设阻抗范围时，确定光伏发电系统发生绝缘故障；依次控制每个直流支路中的分断装置断开来确定存在绝缘故障的直流支路。
在光伏发电系统运行前，通过绝缘阻抗检测装置检测光伏发电系统的对地绝缘阻抗值，进而能够先判断光伏发电系统整体是否出现了绝缘故障，当确定光伏发电系统出现绝缘故障时，控制器能够通过依次控制每个直流支路中的分断装置断开来确定存在绝缘故障的直流支路，进而能够及时对出现绝缘故障的直流支路进行绝缘故障鼓励，以排除安全隐患。
第三方面，本申请还提供了一种诊断光伏发电系统绝缘故障的方法，光伏发电系统包括：逆变器和至少两个直流支路；每个直流支路包括：DC-DC变换器和漏电流检测装置；DC-DC变换器的输入端连接对应的光伏单元；DC-DC变换器的输出端连接逆变器的输入端。方法包括：控制DC-DC变换器将对应的光伏单元输出的直流电进行直流-直流变换后传输给逆变器；控制逆变器将所述DC-DC变换器输送的直流电逆变为交流电；接收漏电流检测装置检测的其所在直流支路的漏电流；在光伏发电系统运行前，根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路；在光伏发电系统运行时，当直流支路的漏电流的大小超过预设范围时，确定直流支路发生绝缘故障。
利用该方法，在光伏发电系统运行前，能够根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路。还能在在光伏发电系统运行时，当直流支路的漏电流的大小超过预设范围时，确定直流支路发生绝缘故障。因此该方法能够在光伏发电系统运行前或者运行时均能够确定出现绝缘故障的直流支路，进而能够及时控制出现绝缘故障的直流支路停止工作以隔离绝缘故障，排除安全隐患。
结合第三方面，在第一种可能的实现方式中，在根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路之前还包括：获得光伏发电系统的对地绝缘阻抗值；当对地绝缘阻抗值小于预设阻抗范围时，确定光伏发电系统发生绝缘故障。
当确定光伏发电系统出现绝缘故障时，可以通过漏电流检测装置检测各直流支路的漏电流，并将漏电流发送给控制器，以使控制器根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路。而当确定光伏发电系统未出现绝缘故障时，则可以控制漏电流检测装置检测不再检测各个直流支路的漏电流，因此能够提升绝缘阻 抗的检测效率。
结合第三方面及上述任意一种实现方式，在第二种可能的实现方式中，该方法还包括：获得对应的直流支路的所述DC-DC变换器的输入端对地电压；在DC-DC变换器的输入端对地电压小于预设输入电压范围时，确定对应的直流支路发生绝缘故障。
控制器可以根据输入电压检测装置的检测结果确定发生绝缘故障直流支路，还可以将获取的判断结论与利用直流支路的漏电流获取的判断结论进行比较验证，以进一步提高绝缘故障检测的准确性。
结合第三方面及上述任意一种实现方式，在第三种可能的实现方式中，该方法还包括：获得对应的直流支路的DC-DC变换器的输出端对地电压；在DC-DC变换器的输出端对地电压小于预设输出电压范围时，确定对应的直流支路发生绝缘故障。
控制器可以根据输出电压检测装置的检测结果确定发生绝缘故障直流支路，还可以将获取的判断结论与利用直流支路的漏电流获取的判断结论进行比较验证，以进一步提高绝缘故障检测的准确性。
结合第三方面及上述任意一种实现方式，在第四种可能的实现方式中，每个直流支路均包括分断装置，该方法还包括：在确定直流支路发生绝缘故障时，控制发生绝缘故障的直流支路上的分断装置断开，以实现绝缘故障的快速有效隔离。
结合第三方面及上述任意一种实现方式，在第五种可能的实现方式中，该方法还包括：在控制发生绝缘故障的所述直流支路上的所述分断装置断开后，控制发生绝缘故障的直流支路上的所述DC-DC变换器关机，以保护对应的直流支路，便于故障维护。
第四方面，本申请还提供了另一种诊断光伏发电系统绝缘故障的方法，该光伏发电系统包括：绝缘阻抗检测装置、逆变器和至少两个直流支路；每个直流支路包括：DC-DC变换器和分断装置；DC-DC变换器的输入端连接对应的光伏单元；DC-DC变换器的输出端连接所述逆变器的输入端，该方法包括：控制DC-DC变换器将对应的光伏单元输出的直流电进行直流-直流变换后传输给逆变器；控制逆变器将DC-DC变换器输送的直流电逆变为交流电；控制绝缘阻抗检测装置在光伏发电系统运行前，检测光伏发电系统的对地绝缘阻抗值；当对地绝缘阻抗值小于预设阻抗范围时，确定光伏发电系统发生绝缘故障；依次控制每个所述直流支路中的分断装置断开来确定存在绝缘故障的直流支路。
在光伏发电系统运行前，通过绝缘阻抗检测装置检测光伏发电系统的对地绝缘阻抗值，进而能够先判断光伏发电系统整体是否出现了绝缘故障，当确定光伏发电系统出现绝缘故障时，控制器能够通过依次控制每个直流支路中的分断装置断开来确定存在绝缘故障的直流支路，进而能够及时对出现绝缘故障的直流支路进行绝缘故障鼓励，以排除安全隐患。
本申请至少具有以下优点：
本申请提供的光伏发电系统的每个直流支路均包括DC-DC变换器和漏电流检测装置，该漏电流检测装置能够检测所在的直流支路的漏电流，并将漏电流的检测结果发送给控制器。由于当光伏发电系统在运行前出现绝缘故障时，正常直流支路的漏电流 会流向出现绝缘故障的直流支路，因此出现绝缘故障的直流支路的漏电流的大小为所有正常直流支路漏电流大小的和，出现绝缘故障的直流支路的漏电流的方向与所有正常直流支路漏电流的方向相反，因此控制器可以根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路。当光伏发电系统在运行时出现绝缘故障时，出现绝缘故障的直流支路的漏电流大小会显著增大，因此当直流支路的漏电流的大小超过预设范围时，控制器能够确定该直流支路发生绝缘故障。
本申请提供的光伏发电系统在运行前或者运行时均能够确定出现绝缘故障的直流支路，以便于及时对出现绝缘故障的直流支路采取措施，例如及时控制出现绝缘故障的直流支路停止工作以隔离绝缘故障，排除安全隐患。
附图说明
图1为一种光伏发电系统的示意图；
图2为本申请实施例提供的一种光伏发电系统的示意图；
图3为本申请实施例提供的另一种光伏发电系统的示意图；
图4为本申请实施例提供的又一种光伏发电系统的示意图；
图5为本申请实施例提供的再一种光伏发电系统的示意图；
图6为本申请实施例提供的另一种光伏发电系统的示意图；
图7为本申请实施例提供的又一种光伏发电系统的示意图；
图8为本申请实施例提供的再一种光伏发电系统的示意图；
图9为本申请实施例提供的另一种光伏发电系统的示意图；
图10为本申请实施例提供的一种诊断光伏发电系统绝缘故障的方法的流程图；
图11为本申请实施例提供的又一种诊断光伏发电系统绝缘故障的方法的流程图。
具体实施方式
目前，对于包括多条直流支路的光伏发电系统，在光伏发电系统运行前，出现绝缘故障时，会影响光伏发电系统的正常启动；当光伏发电系统运行时，出现绝缘故障时，如果人畜接触则会带来安全隐患；因此需要对光伏发电系统进行绝缘故障检测。
下面首先结合附图说明一种对光伏发电系统进行绝缘故障检测的方法。
参见图1，该图为一种对光伏发电系统的示意图。
该光伏发电系统包括：光伏单元104、DC-DC变换器102以及逆变器103。
DC-DC变换器102用于将对应的光伏单元104输出的直流电进行直流-直流变换后传输给逆变器103。
可以通过检测整个光伏发电系统的绝缘阻抗以确定光伏发电系统是否出现绝缘故障。当光伏发电系统出现绝缘故障时，光伏发电系统的绝缘阻抗值下降，此时可以关闭光伏发电系统进行故障检修。
但当利用该方法判断出光伏发电系统出现绝缘故障时，无法具体定位出现绝缘故障的直流支路，因此也无法做到在光伏发电系统运行前和运行时进行故障隔离。
为了解决上述技术问题，本申请提供了一种光伏发电系统及方法，在光伏发电系 统的每条直流支路中增加了漏电流检测装置，能够检测出每条直流支路中的漏电流并将检测结果发送给控制器。控制器能够在光伏发电系统运行前，根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路，还能够在光伏发电系统运行时，当直流支路的漏电流的大小超过预设范围时，确定直流支路发生绝缘故障。因此能够确定光伏发电系统出现绝缘故障的直流支路，进而能够及时控制出现绝缘故障的直流支路停止工作以隔离绝缘故障。
为了使本技术领域的人员更好地理解本申请方案，下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行描述。以下说明中将出现绝缘故障的直流支路称为故障支路。
系统实施例一：
本申请实施例提供了一种光伏发电系统，下面结合附图具体说明。
参见图2，该图为本申请实施例提供的一种光伏发电系统的示意图。
该光伏发电系统包括：逆变器103、控制器(图中未示出)和至少两个直流支路。即直流支路的个数可以大于或等于2。
每个直流支路包括：漏电流检测装置101和DC-DC变换器102。
DC-DC变换器102的输入端连接对应的光伏单元104，DC-DC变换器102的输出端连接逆变器103的输入端。DC-DC变换器102用于将对应的光伏单元104输出的直流电进行直流-直流变换后传输给逆变器103。
本申请实施例的光伏单元104可以包括一个光伏组件，也可以包括多个光伏组件串并联形成，例如多个光伏组件先串联在一起形成光伏组串，多个光伏组串再并联在一起形成光伏单元。本申请实施例中不具体限定光伏组件的具体数量，本领域技术人员可以根据实际应用场景进行设置。
DC-DC变换器102用于进行功率变换，例如可以具体为Boost(升压)电路，用于实现MPPT调节。
逆变器103用于将DC-DC变换器102输送的直流电逆变为交流电。
图中以各个直流支路先并联后连接逆变器103的输入端为例，可以理解的是，各个直流支路也可以连接逆变器103的不同输入端口，在逆变器103内部实现并联，本申请实施例不作具体限定。
漏电流检测装置101，用于检测所在的直流支路的漏电流，将漏电流发送给控制器。漏电流检测装置101检测的是直流侧的漏电流。
附图2中以漏电流检测装置101位于光伏单元104和DC-DC变换器102之间为例，可以理解的是，每个直流支路的漏电流检测装置101还可以集成在对应的DC-DC变换器102中，或集成在逆变器103中，还可以单独设置，例如连接于DC-DC变换器102和逆变器103之间。
其中，当漏电流检测装置101集成在对应的DC-DC变换器102中时，漏电流检测装置101可以集成在DC-DC变换器102的输入端，或者集成在DC-DC变换器102的输出端。
下面以漏电流检测装置101位于光伏单元104和DC-DC变换器102之间为例进行说明，当漏电流检测装置101位于其他位置时的工作原理类似，本申请实施例不再赘述。
在一种可能的实现方式中，漏电流检测装置101用于在光伏发电系统运行前以及运行时检测所在直流支路光伏单元104正输出支路PV+和负输出支路PV-的电流，漏电流检测装置101可以将正输出支路PV+的电流大小和负输出支路PV-的电流大小之差作为漏电流的检测值，再将漏电流的检测值I RCD发送给控制器。。
在光伏发电系统运行前，控制器根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路。
具体的，当直流支路出现绝缘故障时，正常直流支路的漏电流会流向出现绝缘故障的直流支路，因此出现绝缘故障的直流支路的漏电流的大小为所有正常直流支路漏电流大小的和，出现绝缘故障的直流支路的漏电流的方向与所有正常直流支路漏电流的方向相反，因此控制器可以根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路。下面举例说明。
以光伏逆变系统包括以下五条直流支路：直流支路1-直流支路5，其中直流支路1的PV1+支路出现绝缘故障为例进行说明，各直流支路漏电流检测值可以参见表1。
表1一条PV支路短路时漏电流检测值数据表
Figure PCTCN2020090227-appb-000001
表中漏电流检测值前的正号与负号表征漏电流的不同方向，当直流支路1的PV1+支路在运行前出现绝缘故障时，正常直流支路的漏电流会流向出现绝缘故障的直流支路，出现绝缘故障的直流支路的漏电流的大小(即40mA)为所有正常直流支路漏电流大小的和(即10mA×4＝40mA)，并且出现绝缘故障的直流支路的漏电流的方向与所有正常直流支路漏电流的方向相反。因此光伏发电系统的控制器可以根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路为直流支路1。
可以理解的是，以上数值仅是示意性说明，实际检测中，可能有比较小的出入，例如发生绝缘故障的支路的漏电流绝对值之和近似等于正常支路的漏电流绝对值之和。
当光伏发电系统确定运行前无绝缘故障或已经排除绝缘故障后，光伏发电系统可以进入运行状态，但当光伏发电系统处于运行状态时可能由于人畜意外碰撞、雨雪天气等因素而出现绝缘故障，出现绝缘故障的直流支路的漏电流的大小会显著增大，因此可以根据直流支路的漏电流的大小确定直流支路是否出现绝缘故障。
具体的，可以预先确定直流支路在未出现绝缘故障时的漏电流的大小的预设范围，在光伏发电系统进入运行状态后，漏电流检测装置101实时检测所在直流支路的漏电流并将漏电流发送给控制器，控制器还用于当直流支路的漏电流的大小超过预设范围时，确定直流支路发生绝缘故障。其中，预设范围可以根据实际应用场景进行设置， 本申请实施例不作具体限定。
本申请实施例提供的光伏发电系统的每个直流支路均包括DC-DC变换器和漏电流检测装置，该漏电流检测装置能够检测所在的直流支路的漏电流，并将漏电流的检测结果发送给光伏发电系统控制器。由于当光伏发电系统在运行前出现绝缘故障时，正常直流支路的漏电流会流向出现绝缘故障的直流支路，因此出现绝缘故障的直流支路的漏电流的大小为所有正常直流支路漏电流大小的和，出现绝缘故障的直流支路的漏电流的方向与所有正常直流支路漏电流的方向相反，因此光伏发电系统的控制器可以根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路。当光伏发电系统在运行时出现绝缘故障时，出现绝缘故障的直流支路的漏电流大小会显著增大，因此当直流支路的漏电流的大小超过预设范围时，控制器能够确定该直流支路发生绝缘故障。
本申请实施例提供的光伏发电系统在运行前或者运行时均能够确定出现绝缘故障的直流支路，进而能够及时控制出现绝缘故障的直流支路停止工作以隔离绝缘故障，排除安全隐患。
以上实施例提供的光伏发电系统的每条直流支路都包括了漏电流检测装置，能够在光伏发电系统运行前检测对应直流支路的漏电流。本申请实施例还提供了一种光伏发电系统，能够检测光伏发电系统的对地绝缘阻抗值，进而能够先判断光伏发电系统整体是否出现了绝缘故障，当确定光伏发电系统出现绝缘故障时，再根据漏电流检测装置检测的漏电流来定位发生绝缘故障的直流支路。如果未出现绝缘故障，则不需要根据漏电流检测装置检测的漏电流来定位绝缘故障，从而提高工作效率。下面结合附图具体说明。
系统实施例二：
参见图3，该图为本申请实施例提供的另一种光伏发电系统的示意图。
该光伏发电系统与系统实施例一提供的光伏发电系统的区别在于，还包括：绝缘阻抗检测装置105。关于其余部分的说明可以参见上述实施例，本实施例在此不再赘述。
本申请实施例以各个直流支路先并联，然后连接逆变器103的输入端，绝缘阻抗检测装置105连接光伏发电系统的直流总线为例进行说明，即绝缘阻抗检测装置105可以为独立的装置。可以理解的是，绝缘阻抗检测装置105还可以集成在逆变器103内部、或集成在DC-DC变换器102内部、或集成在光伏单元104内部以及外置于光伏发电系统。其中，当绝缘阻抗检测装置105集成在DC-DC变换器102内部时，绝缘阻抗检测装置105可以集成在DC-DC变换器102的输入端或者输出端。本申请实施例对绝缘阻抗检测装置105的设置位置不作具体限定。
当光伏发电系统无绝缘故障时，光伏发电系统对地绝缘。当光伏发电系统出现绝缘故障时，光伏发电系统的对地绝缘阻抗值会减小，因此可以预先确定光伏发电系统在未出现绝缘故障时的预设阻抗范围，在光伏发电系统运行前，通过绝缘阻抗检测装置105检测光伏发电系统的对地绝缘阻抗值并将对地绝缘阻抗值发送给控制器。控制 器还用于当对地绝缘阻抗值小于预设阻抗范围时，确定光伏发电系统发生绝缘故障。
其中，预设阻抗范围可以根据实际应用场景进行设置，本申请实施例在此不作具体限定。
本申请实施例提供的光伏发电系统还具有绝缘阻抗检测装置，能够检测光伏发电系统的对地绝缘阻抗值并将对地绝缘阻抗值发送给控制器，进而能够使控制器在对地绝缘阻抗值小于预设阻抗范围时确定光伏发电系统出现了绝缘故障。当确定光伏发电系统出现绝缘故障时，可以通过漏电流检测装置检测各直流支路的漏电流，并将漏电流发送给控制器，以使控制器根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路。而当确定光伏发电系统未出现绝缘故障时，则不需要漏电流检测装置检测各个直流支路的漏电流，因此能够提升绝缘阻抗的检测效率。
为了防止控制器误判，更加准确地确定直流支路是否出现绝缘故障，进而有效隔离绝缘故障，本申请实施例三还提供了一种光伏发电系统，能够根据DC-DC变换器的输入端对地电压或输出端对地电压进一步确定直流支路是否发生绝缘故障，来验证根据漏电流判断的绝缘故障是否准确，下面结合附图具体说明。
系统实施例三：
参见图4，该图为本申请实施例提供的又一种光伏发电系统的示意图。
该光伏发电系统与系统实施例二提供的光伏发电系统的区别在于，每个直流支路还包括：输入电压检测装置106。关于其余部分的说明可以参见上述实施例，本实施例在此不再赘述。
输入电压检测装置106可以连接在DC-DC变换器102的输入端，具体可以集成在DC-DC变换器102的内部，或集成在光伏单元104的内部，还可以单独设置，本申请实施例不作具体限定。
输入电压检测装置106，用于检测对应的直流支路的DC-DC变换器102的输入端对地电压，具体可以包括正输入端的对地电压和负输入端的对地电压，输入电压检测装置106还可以将检测结果发送给控制器。
当DC-DC变换器102的输入端出现绝缘故障时，输入端的对地电压会降低，因此可以预先确定直流支路在未出现绝缘故障时的预设输入电压范围。具体的，预设输入电压范围可以包括正输入端对应的预设输入电压范围和负输入端对应的预设输入电压范围。
控制器将输入电压检测装置106检测的正输入端的对地电压与正输入端对应的预设输入电压范围进行比较，将负输入端的对地电压与负输入端对应的预设输入电压范围进行比较。
其中，预设输入电压范围可以根据实际应用场景进行设置，本申请实施例在此不作具体限定。例如当DC-DC变换器102的正输入端发生对地绝缘故障时，输入电压检测装置106检测的正输入端电压，控制器可以将检测得到的电压与预设值进行比较，例如预设值为0时，当检测得到的电压为0时，则判断正输入端对地发生绝缘故障。 又例如当预设值为0附近的一个正值时，当检测得到的电压小于或等于预设值时，则判断正输入端对地发生绝缘故障。
当控制器确定DC-DC变换器102的输入端对地电压小于预设输入电压范围时，确定对应的直流支路发生绝缘故障。此时控制器可以将判断结论与系统实施例一中利用直流支路的漏电流获取的判断结论进行比较验证，以提高绝缘故障检测的准确性，能够有效防止控制器误判，进而能够有效隔离绝缘故障。
还可以参见图5，该图为本申请实施例提供的再一种光伏发电系统的示意图。
该光伏发电系统与系统实施例二提供的光伏发电系统的区别在于，每个直流支路还包括：输出电压检测装置107。关于其余部分的说明可以参见上述实施例，本实施例在此不再赘述。
输出电压检测装置107连接在DC-DC变换器102的输出端，具体可以集成在DC-DC变换器102的内部，也可以单独设置，本申请实施例不作具体限定。
输出电压检测装置107，用于检测对应的直流支路的DC-DC变换器102的输出端对地电压，具体可以包括正输出端的对地电压和负输出端的对地电压，输出电压检测装置107还可以将检测结果发送给控制器。
当DC-DC变换器102的输出端出现绝缘故障时，输出端的对地电压会降低，因此可以预先确定直流支路在未出现绝缘故障时的预设输出电压范围。具体的，预设输出电压范围可以包括正输出端对应的预设输出电压范围和负输出端对应的预设输出电压范围。
控制器将输出电压检测装置107检测的正输出端的对地电压与正输出端对应的预设输出电压范围进行比较，将负输出端的对地电压与负输出端对应的预设输出电压范围进行比较。
其中，预设输出电压范围可以根据实际应用场景进行设置，本申请实施例在此不作具体限定。
当控制器确定DC-DC变换器102的输出端对地电压小于预设输出电压范围时，确定对应的直流支路发生绝缘故障。此时控制器可以将判断结论与系统实施例一中利用直流支路的漏电流获取的判断结论进行比较验证，以提高绝缘故障检测的准确性，能够有效防止控制器误判，进而能够有效隔离绝缘故障。
还可以参见图6，该图为本申请实施例提供的另一种光伏发电系统的示意图。
该光伏发电系统与系统实施例二提供的光伏发电系统的区别在于，每个直流支路还包括：输入电压检测装置106和输出电压检测装置107。关于其余部分的说明可以参见上述实施例，本实施例在此不再赘述。
关于输入电压检测装置106的说明可以参见本实施例中图4对应的相关说明，关于输出电压检测装置107的说明可以参见本实施例中图5对应的相关说明，在此不再赘述。
该光伏发电系统在DC-DC变换器102的输入端和输出端均增加了电压检测装置，以使控制器能够根据DC-DC变换器102的输入端和输出端的电压检测装置的检测结果 更加准确的确定发生绝缘故障直流支路。此时控制器可以将获取的判断结论与系统实施例一中利用直流支路的漏电流获取的判断结论进行比较验证，以进一步提高绝缘故障检测的准确性，能够有效防止控制器误判，进而能够有效隔离绝缘故障。
综上所述，本申请实施例提供的光伏发电系统的每条直流支路不仅增加了漏电流检测装置，并且在DC-DC变换器的输入端和输出端中的至少一端增加了电压检测装置，以使控制器根据电压检测装置的检测结果确定发生绝缘故障直流支路。还可以将获取的判断结论与系统实施例一中利用直流支路的漏电流获取的判断结论进行比较验证，以进一步提高绝缘故障检测的准确性。因此本申请实施例提供的光伏发电系统能够有效防止控制器误判，进而提升绝缘故障隔离时的准确度。
由于本申请实施例提供的光伏发电系统能够确定出现绝缘故障的直流支路，因此可以进一步控制该故障支路断开以实现绝缘故障隔离。在一种可能的实现方式中，可以通过控制器控制故障支路的功率变换器关机以隔离绝缘故障。在另一种可能的实现方式中，可以在每个直流支路中增加分断装置以隔离绝缘故障，下面结合附图具体说明。
系统实施例四：
参见图7，该图为本申请实施例提供的又一种光伏发电系统的示意图。
该光伏发电系统与系统实施例一提供的光伏发电系统的区别在于，每个直流支路还包括：分断装置108。关于其余部分的说明可以参见上述实施例，本实施例在此不再赘述。
图中以分断装置108设置于DC-DC变换器102的输出端且作为独立的装置为例，可以理解的是，实际应用中的分断装置108还可以作为独立的装置设置于DC-DC变换器102的输入端，或集成在DC-DC变换器102的输入端，或集成在逆变器103的输入端，或集成在光伏单元104内。此外，当各个直流支路先连接逆变器103的不同输入端口，在逆变器103内部实现并联时，分断装置108也可以集成在逆变器103中。本申请实施例对分断装置108在光伏发电系统中的设置位置不作具体限定。
控制器还用于在确定直流支路发生绝缘故障时，控制发生绝缘故障的直流支路上的分断装置108断开，分断装置108断开后，所在故障支路断路，因此故障支路无法接入逆变器103，进而实现了绝缘故障的隔离。
进一步的，控制器在控制发生绝缘故障的所述直流支路上的分断装置108断开后，控制发生绝缘故障的直流支路上的DC-DC变换器102关机。
还可以参见图8，该图为本申请实施例提供的再一种光伏发电系统的示意图。
该光伏发电系统还包括绝缘阻抗检测装置105，能够检测光伏发电系统的对地绝缘阻抗值并将对地绝缘阻抗值发送给控制器，进而能够使控制器在对地绝缘阻抗值小于预设阻抗范围时确定光伏发电系统出现了绝缘故障。当确定光伏发电系统出现绝缘故障时，可以通过漏电流检测装置检测各直流支路的漏电流，并将漏电流发送给控制器，以使控制器根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路。 而当确定光伏发电系统未出现绝缘故障时，则不需要漏电流检测装置检测各个直流支路的漏电流，因此能够提升绝缘阻抗的检测效率。
进一步的，也可以在每个直流支路的DC-DC变换器102的输入端增加输入电压检测装置和/或在DC-DC变换器102的输出端增加输出电压检测装置，具体可以参见系统实施例三中的相关说明，本申请实施例在此不再赘述。
本申请实施例提供的光伏发电系统的每条直流支路不仅增加了漏电流检测装置，还增加了分断装置，当控制器根据漏电流检测装置的检测结果确定出存在绝缘故障的直流支路，控制器还可以控制存在绝缘故障的直流支路的分断装置断开，以实现绝缘故障的隔离。
以上系统实施例均可以通过漏电流检测装置检测所在的直流支路的漏电流，进而通过控制器确定绝缘故障的直流支路。本申请实施例还提供一种光伏发电系统，每个直流支路中均包括分断装置而不包括漏电流检测装置，当确定光伏发电系统在运行前发生绝缘故障时，控制器通过依次控制每个直流支路中的分断装置断开来确定存在绝缘故障的直流支路，下面结合附图具体说明。
系统实施例五：
参见图9，该图为本申请实施例提供的另一种光伏发电系统的示意图。
本申请实施例提供的光伏发电系统包括：绝缘阻抗检测装置105、逆变器103、控制器(图中并未示出)和至少两个直流支路。即直流支路的个数可以大于或等于2。
其中，每个直流支路包括：DC-DC变换器102和分断装置108。
DC-DC变换器102的输入端连接对应的光伏单元104，DC-DC变换器102的输出端连接逆变器103的输入端。本申请实施例的光伏单元104可以包括一个光伏组件，也可以包括多个光伏组件串并联形成，例如多个光伏组件先串联在一起形成光伏组串，多个光伏组串再并联在一起形成光伏单元。本申请实施例中不具体限定光伏组件的具体数量，本领域技术人员可以根据实际应用场景进行设置。
DC-DC变换器102用于进行功率变换，例如可以具体为Boost(升压)电路，用于实现MPPT调节。DC-DC变换器102将对应的光伏单元104输出的直流电进行直流-直流变换后传输给逆变器103。
逆变器103用于将DC-DC变换器102输送的直流电逆变为交流电。
图中以各个直流支路先并联后连接逆变器103的输入端为例，可以理解的是，各个直流支路也可以连接逆变器103的不同输入端口，在逆变器103内部实现并联，本申请实施例不作具体限定。
当光伏发电系统无绝缘故障时，光伏发电系统对地绝缘。当光伏发电系统出现绝缘故障时，光伏发电系统的对地绝缘阻抗值会减小，因此可以预先确定光伏发电系统在未出现绝缘故障时的预设阻抗范围，在光伏发电系统运行前，通过绝缘阻抗检测装置105检测光伏发电系统的对地绝缘阻抗值并将对地绝缘阻抗值发送给控制器。控制器能够当对地绝缘阻抗值小于预设阻抗范围时，确定光伏发电系统发生绝缘故障。
控制器还能够通过依次控制每个直流支路中的分断装置108断开来确定存在绝缘故障的直流支路。
当分断装置断开存在绝缘故障的直流支路时，即相当于实现了绝缘故障隔离，而当光伏发电系统隔离绝缘故障后，光伏发电系统恢复对地绝缘。因此若分断装置断开了存在绝缘故障的直流支路，绝缘阻抗检测装置的检测结果会恢复至预设阻抗范围。控制器可以依次控制每个直流支路中的分断装置断开，进而根据分断装置断开后绝缘阻抗检测装置的检测结果确定存在绝缘故障的直流支路。
综上所述，本申请实施例提供的光伏发电系统，在光伏发电系统运行前，通过绝缘阻抗检测装置检测光伏发电系统的对地绝缘阻抗值，进而能够先判断光伏发电系统整体是否出现了绝缘故障，当确定光伏发电系统出现绝缘故障时，控制器能够通过依次控制每个直流支路中的分断装置断开来确定存在绝缘故障的直流支路，进而能够及时对出现绝缘故障的直流支路进行绝缘故障鼓励，以排除安全隐患。
方法实施例一：
基于以上实施例提供的光伏发电系统，本申请实施例还提供了一种诊断光伏发电系统绝缘故障的方法，下面结合附图具体说明。
参见图10，该图为本申请实施例提供的一种诊断光伏发电系统绝缘故障的方法的流程图。
其中，该光伏电系统包括：逆变器、控制器和至少两个直流支路。
每个直流支路包括：DC-DC变换器和漏电流检测装置。DC-DC变换器的输入端连接对应的光伏单元，DC-DC变换器的输出端连接逆变器的输入端。
DC-DC变换器用于将对应的光伏单元输出的直流电进行直流-直流变换后发送给所述逆变器。
逆变器用于将DC-DC变换器输送的直流电逆变为交流电。
漏电流检测装置，用于检测所在的直流支路的漏电流。
关于光伏电系统的具体说明可以参见系统实施例一，本申请实施例在此不再赘述。
本申请实施例所述的方法可以由控制器实现，本实施例提供的方法包括以下步骤：
S201：在光伏发电系统运行前，根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路。
在光伏发电系统运行前，各个直流支路的漏电流检测装置检测所在的直流支路的漏电流并将漏电流的检测结果发送给控制器。
当直流支路出现绝缘故障时，正常直流支路的漏电流会流向出现绝缘故障的直流支路，因此出现绝缘故障的直流支路的漏电流的大小为所有正常直流支路漏电流大小的和，出现绝缘故障的直流支路的漏电流的方向与所有正常直流支路漏电流的方向相反，因此控制器可以根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路。
S202：在光伏发电系统运行时，当直流支路的漏电流的大小超过预设范围时，确 定直流支路发生绝缘故障。
当光伏发电系统运行时，出现绝缘故障的直流支路的漏电流的大小会显著增大，因此可以根据直流支路的漏电流的大小确定直流支路是否出现绝缘故障。
可以预先确定直流支路在未出现绝缘故障时的漏电流的大小的预设范围，在光伏发电系统进入运行状态后，漏电流检测装置实时检测所在直流支路的漏电流并将漏电流发送给控制器。
控制器还用于当直流支路的漏电流的大小超过预设范围时，确定直流支路发生绝缘故障。其中，预设范围可以根据实际应用场景进行设置，本申请实施例不作具体限定。
综上所述，本申请实施例提供的诊断光伏发电系统绝缘故障的方法，在光伏发电系统运行前，能够根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路。还能在在光伏发电系统运行时，当直流支路的漏电流的大小超过预设范围时，确定直流支路发生绝缘故障。因此该方法能够在光伏发电系统运行前或者运行时均能够确定出现绝缘故障的直流支路，进而能够及时控制出现绝缘故障的直流支路停止工作以隔离绝缘故障，排除安全隐患。
进一步的，当光伏发电系统还包括绝缘阻抗检测装置时，S201之前还可以包括以下步骤：
获得光伏发电系统的对地绝缘阻抗值；
当对地绝缘阻抗值小于预设阻抗范围时，确定光伏发电系统发生绝缘故障。
当光伏发电系统无绝缘故障时，光伏发电系统对地绝缘。当光伏发电系统出现绝缘故障时，光伏发电系统的对地绝缘阻抗值会减小，因此可以预先确定光伏发电系统在未出现绝缘故障时的预设阻抗范围，在光伏发电系统运行前，通过绝缘阻抗检测装置检测光伏发电系统的对地绝缘阻抗值并将对地绝缘阻抗值发送给控制器。
控制器能够当对地绝缘阻抗值小于预设阻抗范围时，确定光伏发电系统发生绝缘故障。
当确定光伏发电系统出现绝缘故障时，可以通过漏电流检测装置检测各直流支路的漏电流，并将漏电流发送给控制器，以使控制器根据各个直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路。而当确定光伏发电系统未出现绝缘故障时，则可以控制漏电流检测装置检测不再检测各个直流支路的漏电流，因此能够提升绝缘阻抗的检测效率。
进一步的，当每个直流支路的DC-DC变换器的输入端连接输入电压检测装置时，该方法还包括以下步骤：
获得对应的直流支路的DC-DC变换器的输入端对地电压；
在DC-DC变换器的输入端对地电压小于预设输入电压范围时，确定对应的直流支路发生绝缘故障。
通过输入电压检测装置检测对应的直流支路的DC-DC变换器的输入端对地电压，具体可以包括正输入端的对地电压和负输入端的对地电压，输入电压检测装置还可以 将检测结果发送给控制器。
当DC-DC变换器的输入端出现绝缘故障时，输入端的对地电压会降低，因此可以预先确定直流支路在未出现绝缘故障时的预设输入电压范围。具体的，预设输入电压范围可以包括正输入端对应的预设输入电压范围和负输入端对应的预设输入电压范围。
控制器能够将输入电压检测装置检测的正输入端的对地电压与正输入端对应的预设输入电压范围进行比较，将负输入端的对地电压与负输入端对应的预设输入电压范围进行比较。当确定DC-DC变换器的输入端对地电压小于预设输入电压范围时，确定对应的直流支路发生绝缘故障。此时控制器可以将判断结论与S202中利用直流支路的漏电流获取的判断结论进行比较验证，以提高绝缘故障检测的准确性，能够有效防止控制器误判，进而能够有效隔离绝缘故障。
进一步的，当每个直流支路的DC-DC变换器的输出端连接输出电压检测装置时，该方法还包括以下步骤：
获得对应的直流支路的DC-DC变换器的输出端对地电压；
在DC-DC变换器的输出端对地电压小于预设输出电压范围时，确定对应的直流支路发生绝缘故障。
通过输出电压检测装置检测对应的直流支路的DC-DC变换器的输出端对地电压，具体可以包括正输出端的对地电压和负输出端的对地电压，输出电压检测装置还可以将检测结果发送给控制器。
当DC-DC变换器的输出端出现绝缘故障时，输出端的对地电压会降低，因此可以预先确定直流支路在未出现绝缘故障时的预设输出电压范围。具体的，预设输出电压范围可以包括正输出端对应的预设输出电压范围和负输出端对应的预设输出电压范围。
控制器将输出电压检测装置检测的正输出端的对地电压与正输出端对应的预设输出电压范围进行比较，将负输出端的对地电压与负输出端对应的预设输出电压范围进行比较。当确定DC-DC变换器的输出端对地电压小于预设输出电压范围时，确定对应的直流支路发生绝缘故障。此时控制器可以将判断结论与S202中利用直流支路的漏电流获取的判断结论进行比较验证，以提高绝缘故障检测的准确性，能够有效防止控制器误判，进而能够有效隔离绝缘故障。
进一步的，当光伏发电系统的每个直流支路还包括分断装置时，该方法还包括以下步骤：
在确定直流支路发生绝缘故障时，控制发生绝缘故障的直流支路上的分断装置断开，以使故障支路断路，进而隔离绝缘故障。
方法实施例二：
本申请实施例还提供了一种诊断光伏发电系统绝缘故障的方法，能够应用于直流支路中不包括漏电流检测装置的光伏发电系统，下面结合附图具体说明。
参见图11，该图为本申请实施例提供的又一种诊断光伏发电系统绝缘故障的方法的流程图。
其中，该光伏发电系统包括：绝缘阻抗检测装置、逆变器、控制器和至少两个直 流支路。
每个直流支路包括：DC-DC变换器和分断装置。
DC-DC变换器的输入端连接对应的光伏单元，DC-DC变换器的输出端连接逆变器的输入端。
DC-DC变换器用于将对应的光伏单元输出的直流电进行直流-直流变换后传输给逆变器。
逆变器用于将DC-DC变换器输送的直流电逆变为交流电。
绝缘阻抗检测装置，用于在光伏发电系统运行前，检测光伏发电系统的对地绝缘阻抗值，并将检测结果发送给控制器。
关于光伏电系统的具体说明可以参见系统实施例五，本申请实施例在此不再赘述。
本实施例的方法可以由控制器实现，本实施例提供的方法包括以下步骤：
S301：当对地绝缘阻抗值小于预设阻抗范围时，确定光伏发电系统发生绝缘故障。
当光伏发电系统无绝缘故障时，光伏发电系统对地绝缘。当光伏发电系统出现绝缘故障时，光伏发电系统的对地绝缘阻抗值会减小，因此可以预先确定光伏发电系统在未出现绝缘故障时的预设阻抗范围，在光伏发电系统运行前，通过绝缘阻抗检测装置检测光伏发电系统的对地绝缘阻抗值并将对地绝缘阻抗值发送给控制器。
控制器能够当对地绝缘阻抗值小于预设阻抗范围时，确定光伏发电系统发生绝缘故障。
S302：依次控制每个直流支路中的分断装置断开来确定存在绝缘故障的直流支路。
当分断装置断开存在绝缘故障的直流支路时，即相当于实现了绝缘故障隔离，而当光伏发电系统隔离绝缘故障后，光伏发电系统恢复对地绝缘。因此若分断装置断开了存在绝缘故障的直流支路，绝缘阻抗检测装置的检测结果会恢复至预设阻抗范围。控制器可以依次控制每个直流支路中的分断装置断开，进而根据分断装置断开后绝缘阻抗检测装置的检测结果确定存在绝缘故障的直流支路。
综上所述，利用本申请实施例提供的诊断光伏发电系统绝缘故障的方法，在光伏发电系统运行前，通过绝缘阻抗检测装置检测光伏发电系统的对地绝缘阻抗值，进而能够先判断光伏发电系统整体是否出现了绝缘故障，当确定光伏发电系统出现绝缘故障时，控制器能够通过依次控制每个直流支路中的分断装置断开来确定存在绝缘故障的直流支路，进而能够及时对出现绝缘故障的直流支路进行绝缘故障鼓励，以排除安全隐患。
应当理解，在本申请中，“至少一个(项)”是指一个或者多个，“多个”是指两个或两个以上。“和/或”，用于描述关联对象的关联关系，表示可以存在三种关系，例如，“A和/或B”可以表示：只存在A，只存在B以及同时存在A和B三种情况，其中A，B可以是单数或者复数。字符“/”一般表示前后关联对象是一种“或”的关系。“以下至少一项(个)”或其类似表达，是指这些项中的任意组合，包括单项(个)或复数项(个)的任意组合。例如，a，b或c中的至少一项(个)，可以表示：a，b，c，“a和b”，“a和c”，“b和c”，或“a和b和c”，其中a，b，c可以是单个，也可以是多个。
以上所述，仅是本申请的较佳实施例而已，并非对本申请作任何形式上的限制。虽然本申请已以较佳实施例揭露如上，然而并非用以限定本申请。任何熟悉本领域的技术人员，在不脱离本申请技术方案范围情况下，都可利用上述揭示的方法和技术内容对本申请技术方案做出许多可能的变动和修饰，或修改为等同变化的等效实施例。因此，凡是未脱离本申请技术方案的内容，依据本申请的技术实质对以上实施例所做的任何简单修改、等同变化及修饰，均仍属于本申请技术方案保护的范围内。

Claims (16)

  1. 一种光伏发电系统，其特征在于，包括：逆变器、控制器和至少两个直流支路；
    每个所述直流支路包括：DC-DC变换器和漏电流检测装置；
    所述DC-DC变换器的输入端连接对应的光伏单元；所述DC-DC变换器的输出端连接所述逆变器的输入端；
    所述DC-DC变换器，用于将所述对应的光伏单元输出的直流电进行直流-直流变换后传输给所述逆变器；
    所述逆变器，用于将所述DC-DC变换器输送的直流电逆变为交流电；
    所述漏电流检测装置，用于检测所在的直流支路的漏电流，将所述漏电流发送给所述控制器；
    所述控制器，用于在所述光伏发电系统运行前，根据各个所述直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路；
    所述控制器，还用于在所述光伏发电系统运行时，当所述直流支路的漏电流的大小超过预设范围时，确定所述直流支路发生绝缘故障。
  2. 根据权利要求1所述的光伏发电系统，其特征在于，还包括：绝缘阻抗检测装置；
    所述绝缘阻抗检测装置，用于在所述光伏发电系统运行前，检测所述光伏发电系统的对地绝缘阻抗值，将所述对地绝缘阻抗值发送给所述控制器；
    所述控制器，用于当所述对地绝缘阻抗值小于预设阻抗范围时，确定所述光伏发电系统发生绝缘故障。
  3. 根据权利要求1所述的光伏发电系统，其特征在于，每个所述直流支路还包括：输入电压检测装置；
    所述输入电压检测装置，用于检测对应的直流支路的所述DC-DC变换器的输入端对地电压；
    所述控制器，用于在所述DC-DC变换器的输入端对地电压小于预设输入电压范围时，确定对应的直流支路发生绝缘故障。
  4. 根据权利要求1或3所述的光伏发电系统，其特征在于，每个所述直流支路还包括：输出电压检测装置；
    所述输出电压检测装置，用于检测对应的直流支路的所述DC-DC变换器的输出端对地电压；
    所述控制器，用于在所述DC-DC变换器的输出端对地电压小于预设输出电压范围时，确定对应的直流支路发生绝缘故障。
  5. 根据权利要求1-4任一项所述的光伏发电系统，其特征在于，每个所述直流支路还包括：分断装置；
    所述控制器，还用于在确定所述直流支路发生绝缘故障时，控制发生绝缘故障的所述直流支路上的分断装置断开，以隔离绝缘故障。
  6. 根据权利要求5所述的光伏发电系统，其特征在于，所述控制器，还用于在控 制发生绝缘故障的所述直流支路上的所述分断装置断开后，控制发生绝缘故障的所述直流支路上的所述DC-DC变换器关机。
  7. 根据权利要求5所述的光伏发电系统，其特征在于，每个所述直流支路的分断装置集成在所述DC-DC变换器中，或，每个所述直流支路的所述分断装置集成在所述逆变器中。
  8. 根据权利要求1-4任一项所述的光伏发电系统，其特征在于，每个所述直流支路的所述漏电流检测装置集成在对应的所述DC-DC变换器中，或，每个所述直流支路的所述漏电流检测装置集成在所述逆变器中。
  9. 一种光伏发电系统，其特征在于，包括：绝缘阻抗检测装置、逆变器、控制器和至少两个直流支路；
    每个所述直流支路包括：DC-DC变换器和分断装置；
    所述DC-DC变换器的输入端连接对应的光伏单元；所述DC-DC变换器的输出端连接所述逆变器的输入端；
    所述DC-DC变换器，用于将所述对应的光伏单元输出的直流电进行直流-直流变换后传输给所述逆变器；
    所述逆变器，用于将所述DC-DC变换器输送的直流电逆变为交流电；
    所述绝缘阻抗检测装置，用于在所述光伏发电系统运行前，检测所述光伏发电系统的对地绝缘阻抗值，将所述对地绝缘阻抗值发送给所述控制器；
    所述控制器，用于当所述对地绝缘阻抗值小于预设阻抗范围时，确定所述光伏发电系统发生绝缘故障；依次控制每个所述直流支路中的分断装置断开来确定存在绝缘故障的直流支路。
  10. 一种诊断光伏发电系统绝缘故障的方法，其特征在于，所述光伏发电系统包括：逆变器和至少两个直流支路；每个所述直流支路包括：DC-DC变换器和漏电流检测装置；所述DC-DC变换器的输入端连接对应的光伏单元；所述DC-DC变换器的输出端连接所述逆变器的输入端；
    所述方法包括：
    控制所述DC-DC变换器将所述对应的光伏单元输出的直流电进行直流-直流变换后传输给所述逆变器；控制所述逆变器将所述DC-DC变换器输送的直流电逆变为交流电；接收所述漏电流检测装置检测的其所在直流支路的漏电流；
    在所述光伏发电系统运行前，根据各个所述直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路；
    在所述光伏发电系统运行时，当所述直流支路的漏电流的大小超过预设范围时，确定所述直流支路发生绝缘故障。
  11. 根据权利要求10所述的方法，其特征在于，在所述根据各个所述直流支路的漏电流的大小和方向确定存在绝缘故障的直流支路，之前还包括：
    获得所述光伏发电系统的对地绝缘阻抗值；
    当所述对地绝缘阻抗值小于预设阻抗范围时，确定所述光伏发电系统发生绝缘故 障。
  12. 根据权利要求10所述的方法，其特征在于，还包括：
    获得对应的直流支路的所述DC-DC变换器的输入端对地电压；
    在所述DC-DC变换器的输入端对地电压小于预设输入电压范围时，确定对应的直流支路发生绝缘故障。
  13. 根据权利要求10或12所述的方法，其特征在于，还包括：
    获得对应的直流支路的所述DC-DC变换器的输出端对地电压；
    在所述DC-DC变换器的输出端对地电压小于预设输出电压范围时，确定对应的直流支路发生绝缘故障。
  14. 根据权利要求10-13任一项所述的方法，其特征在于，每个所述直流支路均包括分断装置；
    所述方法还包括：
    在确定所述直流支路发生绝缘故障时，控制发生绝缘故障的所述直流支路上的分断装置断开，以隔离绝缘故障。
  15. 根据权利要求14所述的方法，其特征在于，还包括：
    在控制发生绝缘故障的所述直流支路上的所述分断装置断开后，控制发生绝缘故障的所述直流支路上的所述DC-DC变换器关机。
  16. 一种诊断光伏发电系统绝缘故障的方法，其特征在于，所述光伏发电系统包括：绝缘阻抗检测装置、逆变器和至少两个直流支路；每个所述直流支路包括：DC-DC变换器和分断装置；所述DC-DC变换器的输入端连接对应的光伏单元；所述DC-DC变换器的输出端连接所述逆变器的输入端；
    所述方法包括：
    控制所述DC-DC变换器将所述对应的光伏单元输出的直流电进行直流-直流变换后传输给所述逆变器；控制所述逆变器将所述DC-DC变换器输送的直流电逆变为交流电；控制所述绝缘阻抗检测装置在所述光伏发电系统运行前，检测所述光伏发电系统的对地绝缘阻抗值；
    当所述对地绝缘阻抗值小于预设阻抗范围时，确定所述光伏发电系统发生绝缘故障；
    依次控制每个所述直流支路中的分断装置断开来确定存在绝缘故障的直流支路。
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