WO2022061490A1 - 一种光伏发电系统、检测光伏组串对地故障的方法及设备 - Google Patents

一种光伏发电系统、检测光伏组串对地故障的方法及设备 Download PDF

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Publication number
WO2022061490A1
WO2022061490A1 PCT/CN2020/116710 CN2020116710W WO2022061490A1 WO 2022061490 A1 WO2022061490 A1 WO 2022061490A1 CN 2020116710 W CN2020116710 W CN 2020116710W WO 2022061490 A1 WO2022061490 A1 WO 2022061490A1
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Prior art keywords
voltage
photovoltaic
disturbance
string
ground fault
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PCT/CN2020/116710
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English (en)
French (fr)
Inventor
杨波平
赵欢
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华为数字能源技术有限公司
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Application filed by 华为数字能源技术有限公司 filed Critical 华为数字能源技术有限公司
Priority to CN202080011340.8A priority Critical patent/CN114531932A/zh
Priority to JP2023518395A priority patent/JP2023542954A/ja
Priority to PCT/CN2020/116710 priority patent/WO2022061490A1/zh
Priority to AU2020469182A priority patent/AU2020469182B2/en
Priority to EP20954344.6A priority patent/EP4210219A4/en
Publication of WO2022061490A1 publication Critical patent/WO2022061490A1/zh
Priority to US18/187,882 priority patent/US20230223902A1/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
    • H02S50/10—Testing of PV devices, e.g. of PV modules or single PV cells
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

Definitions

  • the present application relates to the technical field of photovoltaic power generation, and in particular, to a photovoltaic power generation system, a method and equipment for detecting ground faults of photovoltaic strings.
  • a photovoltaic array generally includes a plurality of photovoltaic groups connected in series and in parallel.
  • photovoltaic arrays are prone to ground faults, that is, ground faults.
  • ground faults caused by photovoltaic arrays include: damage to the cable insulation of the photovoltaic array, short circuit to the ground inside the photovoltaic string, or short-term short circuit of the photovoltaic array to the ground due to weather and other reasons.
  • the photovoltaic array When the photovoltaic array has a ground fault, it will cause a large leakage current, which may cause a safety accident.
  • IEC standard 62109-2 stipulates that the DC insulation resistance of the photovoltaic array to the ground needs to be tested before starting the photovoltaic inverter. For non-isolated application scenarios, when the DC insulation resistance is low (cannot meet the leakage current requirements), it is not allowed The inverter is turned on until the DC insulation resistance returns to the normal value.
  • the present application provides a photovoltaic power generation system, a method and equipment for detecting ground faults of photovoltaic strings, which can detect whether photovoltaic strings fail to ground, and can automatically determine the specific fault location with high efficiency.
  • Embodiments of the present application provide a photovoltaic power generation system, including: a photovoltaic array, a photovoltaic device, and a controller; the photovoltaic array includes m photovoltaic strings, where m is an integer greater than or equal to 1; the photovoltaic device includes m power conversion circuits; The power conversion circuits are in one-to-one correspondence with the photovoltaic strings, and each photovoltaic string is connected to the corresponding power conversion circuit; the controller is used to obtain the terminal voltage of each photovoltaic string before the voltage disturbance, The terminal voltage is the positive-to-ground voltage or the negative-to-ground voltage of the photovoltaic string, that is, the voltage of PV+ or PV- to ground; the voltage disturbance is performed on each of the photovoltaic strings, and the terminal voltage of each photovoltaic string after the voltage disturbance is obtained.
  • the terminal voltage of the PV string will change significantly before and after the voltage disturbance.
  • the photovoltaic string with ground fault is determined; for the photovoltaic string with ground fault, the terminal of the photovoltaic string before the voltage disturbance is used.
  • the voltage and output voltage can be used to obtain the photovoltaic panel with ground fault, or the terminal voltage and output voltage of the photovoltaic string after voltage disturbance can be used to obtain the photovoltaic panel with ground fault.
  • the photovoltaic device can be an inverter, and the photovoltaic device includes a DC/DC DC/DC conversion circuit and a DC/AC DC/AC conversion circuit, and the photovoltaic string is connected to the input end of the DC/DC DC/DC conversion circuit.
  • the output end of the DC conversion circuit is used to connect the inverter circuit.
  • the DC/DC conversion circuit and the inverter circuit can be integrated in the inverter, and the controller of the inverter can be used to detect the ground fault of the photovoltaic string.
  • a controller can be set independently to realize the detection of the photovoltaic string. Ground fault detection.
  • the inverter may be a single-phase inverter or a three-phase inverter.
  • the PV string When the terminal voltage before the voltage disturbance and the terminal voltage after the voltage disturbance change significantly, it indicates that the PV string has a ground fault. Since all the photovoltaic panels in the photovoltaic string are connected in series, when a short circuit to ground occurs somewhere in the photovoltaic string, the potential at the location where the ground fault occurs is the reference ground, resulting in an increase in the terminal voltage of the photovoltaic string.
  • the reference potential takes the ground potential at the ground fault as the reference potential, and the specific location of the ground fault can be determined by the ratio of the terminal voltage to the output voltage of the entire string.
  • the method is simple and easy to implement, does not require any additional hardware equipment, and does not need to manually detect the N photovoltaic panels of the photovoltaic string one by one, so that the photovoltaic panels with ground faults can be automatically determined, and the detection efficiency is high.
  • the controller is specifically configured to determine that the photovoltaic string is a ground fault when the absolute value of the difference between the terminal voltage before the voltage disturbance of the photovoltaic string and the terminal voltage after the voltage disturbance exceeds a preset threshold. PV strings.
  • the controller is specifically configured to control the output voltage of the photovoltaic string disturbed by the voltage to change in the direction of voltage increase, or to change in the direction of voltage decrease.
  • the open circuit voltage is generally the maximum voltage, that is, it is not necessary to control
  • the default state is the open circuit voltage.
  • the controller is specifically configured to control the output voltage of the photovoltaic string disturbed by the voltage to change from the open-circuit voltage before the voltage disturbance to the first preset voltage after the voltage disturbance, where the first preset voltage is smaller than the open-circuit voltage .
  • the open-circuit voltage is controlled to the short-circuit voltage, that is, the voltage is changed from a large voltage to a small voltage.
  • the controller is specifically configured to control the output voltage of the photovoltaic strings disturbed by the voltage to change from the open-circuit voltage before the voltage disturbance to the short-circuit voltage after the voltage disturbance.
  • each photovoltaic panel connected in series divides the voltage across the photovoltaic string. Therefore, the specific ground fault location can be obtained by proportion.
  • the controller is specifically configured to use the ratio of the terminal voltage to the output voltage before the voltage disturbance of the photovoltaic string with the ground fault, and the number N of photovoltaic cell panels connected in series to obtain the photovoltaic cell panel with the ground fault.
  • the controller is specifically configured to obtain the photovoltaic cell panel with ground fault by the following formula when the terminal voltage is the positive-to-ground voltage:
  • the photovoltaic panel with ground fault is obtained by the following formula:
  • Upv+ represents the positive-to-ground voltage before the voltage disturbance
  • Upv- represents the negative-to-ground voltage before the voltage disturbance
  • Upv represents the output voltage before the voltage disturbance
  • N represents the series-connected photovoltaic cells included in the PV string with the ground fault.
  • the number of panels, x represents the xth photovoltaic panel starting from the positive pole of the photovoltaic string with ground fault.
  • the controller is specifically configured to use the ratio of the terminal voltage after the voltage disturbance of the photovoltaic string to the ground fault to the output voltage after the voltage disturbance, and the number N of photovoltaic panels in series to obtain the ground fault Photovoltaic panels.
  • the controller is specifically configured to obtain the photovoltaic cell panel with ground fault by the following formula when the terminal voltage is the positive-to-ground voltage:
  • the photovoltaic panel with ground fault is obtained by the following formula:
  • Uv+ represents the positive-to-ground voltage after voltage disturbance
  • Uv- represents the negative-to-ground voltage after voltage disturbance
  • Uv represents the output voltage after voltage disturbance
  • N represents the series-connected photovoltaic cells included in the photovoltaic string with the ground fault
  • x represents the xth photovoltaic panel starting from the positive pole of the photovoltaic string with ground fault.
  • An embodiment of the present application further provides a method for detecting a ground fault of a photovoltaic string, including: obtaining the terminal voltage of each photovoltaic string before voltage disturbance, where the terminal voltage is the positive-to-ground voltage or the negative-to-ground voltage of the photovoltaic string ; Perform voltage disturbance on each of the photovoltaic strings, respectively, to obtain the terminal voltage of each photovoltaic string after the voltage disturbance; determine the grounding according to the terminal voltage before the voltage disturbance and the terminal voltage after the voltage disturbance of each of the photovoltaic strings The faulty photovoltaic string; for the photovoltaic string with ground fault, use the terminal voltage and output voltage of the photovoltaic string before the voltage disturbance to obtain the photovoltaic panel with the ground fault, or use the terminal voltage of the photovoltaic string after the voltage disturbance and the output voltage is obtained from the ground fault of the PV panel.
  • the PV string When the terminal voltage before the voltage disturbance and the terminal voltage after the voltage disturbance change significantly, it indicates that the PV string has a ground fault. Since all the photovoltaic panels in the photovoltaic string are connected in series, when a short circuit to ground occurs somewhere in the photovoltaic string, the potential at the location where the ground fault occurs is the reference ground, resulting in an increase in the terminal voltage of the photovoltaic string.
  • the reference potential takes the ground potential at the ground fault as the reference potential, and the specific location of the ground fault can be determined by the ratio of the terminal voltage to the output voltage of the entire string.
  • the method is simple and easy to implement, does not require any additional hardware equipment, and does not need to manually detect the N photovoltaic panels of the photovoltaic string one by one, so that the photovoltaic panels with ground faults can be automatically determined, and the detection efficiency is high.
  • the determining the photovoltaic string with the ground fault according to the terminal voltage before the voltage disturbance of each photovoltaic string and the terminal voltage after the voltage disturbance specifically includes: when the terminal voltage of the photovoltaic string is before the voltage disturbance When the absolute value of the difference from the terminal voltage after the voltage disturbance exceeds the preset threshold, it is determined that the photovoltaic string is a photovoltaic string with a ground fault.
  • the performing voltage disturbance on each of the photovoltaic strings specifically includes: controlling the output voltage of the photovoltaic strings disturbed by the voltage to change in the direction of voltage increase, or to change in the direction of voltage decrease.
  • the controlling the output voltage of the photovoltaic strings disturbed by the voltage to change along the direction of voltage reduction specifically includes: controlling the output voltage of the photovoltaic strings disturbed by the voltage to change from the open-circuit voltage before the voltage disturbance to the voltage disturbance After the first preset voltage, the first preset voltage is smaller than the open circuit voltage.
  • the voltage disturbance can change the voltage from a large to a small direction, and also can change from a small to a large direction.
  • the voltage disturbance is performed on each of the photovoltaic strings respectively.
  • the open-circuit voltage is controlled to the short-circuit voltage, that is, the voltage changes from a large voltage to a small voltage.
  • it includes: controlling the output voltage of the photovoltaic strings disturbed by the voltage to change from the open-circuit voltage before the voltage disturbance to the short-circuit voltage after the voltage disturbance.
  • each photovoltaic panel connected in series divides the voltage across the photovoltaic string. Therefore, the specific ground fault location can be obtained by proportion.
  • the obtaining the photovoltaic panel with ground fault by using the terminal voltage and output voltage of the photovoltaic string before the voltage disturbance specifically includes: using the ratio of the terminal voltage and the output voltage before the voltage disturbance of the photovoltaic string with the ground fault, and Include the number N of PV panels connected in series to obtain the PV panels with a ground fault.
  • the ratio of the terminal voltage before the voltage disturbance of the photovoltaic string to the ground fault and the output voltage before the voltage disturbance, and the number N of photovoltaic panels connected in series are used to obtain the photovoltaic panel with the ground fault, which specifically includes:
  • the photovoltaic panel with ground fault is obtained by the following formula:
  • the photovoltaic panel with ground fault is obtained by the following formula:
  • Upv+ represents the positive-to-ground voltage before the voltage disturbance
  • Upv- represents the negative-to-ground voltage before the voltage disturbance
  • Upv represents the output voltage before the voltage disturbance
  • N represents the series-connected photovoltaic cells included in the PV string with the ground fault.
  • the number of panels, x represents the xth photovoltaic panel starting from the positive pole of the photovoltaic string with ground fault.
  • using the terminal voltage of the photovoltaic string after the voltage disturbance and the output voltage after the voltage disturbance to obtain the photovoltaic panel with a ground fault specifically includes: using the terminal voltage of the photovoltaic string after the ground fault after the voltage disturbance and the ratio of the output voltage after the voltage disturbance, and including the number N of photovoltaic panels connected in series to obtain the photovoltaic panels with a ground fault.
  • the ratio of the terminal voltage after the voltage disturbance of the photovoltaic string with the ground fault to the output voltage after the voltage disturbance, and the number N of photovoltaic panels connected in series to obtain the photovoltaic panel with the ground fault specifically including:
  • the photovoltaic panel with ground fault is obtained by the following formula:
  • the photovoltaic panel with ground fault is obtained by the following formula:
  • Uv+ represents the positive-to-ground voltage after voltage disturbance
  • Uv- represents the negative-to-ground voltage after voltage disturbance
  • Uv represents the output voltage after voltage disturbance
  • N represents the series-connected photovoltaic cells included in the photovoltaic string with the ground fault
  • x represents the xth photovoltaic panel starting from the positive pole of the photovoltaic string with ground fault.
  • Embodiments of the present application further provide a photovoltaic device for detecting ground faults, including: a power conversion circuit, a controller, and a voltage detection circuit; the power conversion circuits are in one-to-one correspondence with photovoltaic strings, and each photovoltaic string is connected to The corresponding power conversion circuit; the voltage detection circuit is used to obtain the terminal voltage of each photovoltaic string before the voltage disturbance, and the terminal voltage is the positive-to-ground voltage or the negative-to-ground voltage of the photovoltaic string; the control The controller is used to perform voltage disturbance on each of the photovoltaic strings; the voltage detection circuit is also used to obtain the terminal voltage of each photovoltaic string after the voltage disturbance; the controller is also used for The terminal voltage of the photovoltaic string before the voltage disturbance and the terminal voltage after the voltage disturbance are used to determine the photovoltaic string with ground fault; for the photovoltaic string with ground fault, the terminal voltage and output voltage of the photovoltaic string before the voltage disturbance are used. Obtain the photovolta
  • the controller is specifically configured to determine that the photovoltaic string is a pair when the absolute value of the difference between the terminal voltage before the voltage disturbance of the photovoltaic string and the terminal voltage after the voltage disturbance exceeds a preset threshold PV strings with ground faults.
  • the embodiment of the present application does not limit the direction of voltage disturbance, for example, the controller controls the output voltage of the photovoltaic string disturbed by the voltage to change in the direction of voltage increase, or to change in the direction of voltage decrease.
  • the controller controls the output voltage of the photovoltaic string disturbed by the voltage to change from an open circuit voltage before the voltage disturbance to a first preset voltage after the voltage disturbance, where the first preset voltage is smaller than the open circuit voltage. That is, a preset voltage can be set, and the preset voltage can be disturbed.
  • the controller uses the ratio of the terminal voltage to the output voltage before the voltage disturbance of the photovoltaic string with the ground fault, and includes the number N of photovoltaic cell panels connected in series to obtain the photovoltaic cell panel with the ground fault.
  • the embodiments of the present application have the following advantages:
  • the terminal voltage of the photovoltaic string before the change and the terminal voltage of the photovoltaic string after the change are used to judge whether the photovoltaic string has occurred.
  • the terminal voltage of the PV string refers to the positive-to-ground voltage or the negative-to-ground voltage.
  • the terminal voltage of the PV string will change significantly before and after the voltage disturbance.
  • the terminal voltage before the voltage disturbance and the terminal voltage after the voltage disturbance change significantly, it indicates that the PV string has a ground fault.
  • the potential at the location where the ground fault occurs is the reference ground, resulting in an increase in the terminal voltage of the photovoltaic string.
  • the reference potential takes the ground potential at the ground fault as the reference potential, and the specific location of the ground fault can be determined by the ratio of the terminal voltage to the output voltage of the entire string.
  • FIG. 1 is a schematic diagram of the ground fault of a single photovoltaic string provided by an embodiment of the present application
  • FIG. 2 is a schematic diagram of the impedance model corresponding to FIG. 1;
  • FIG. 3 is a schematic diagram of two strings of photovoltaic strings provided by an embodiment of the present application.
  • FIG. 4 is a schematic diagram of a photovoltaic power generation system corresponding to a single photovoltaic string according to an embodiment of the present application
  • FIG. 5 is a flowchart of a method for detecting a ground fault of a photovoltaic string provided by an embodiment of the present application
  • FIG. 6 is a schematic diagram of a photovoltaic power generation system corresponding to a multi-channel photovoltaic string provided by an embodiment of the present application;
  • FIG. 7 is a flowchart of another method for detecting a ground fault of a photovoltaic string provided by an embodiment of the present application.
  • FIG. 8 is a flowchart of another method for detecting a ground fault of a photovoltaic string provided by an embodiment of the present application.
  • FIG. 9 is a schematic diagram of a universal photovoltaic system provided by an embodiment of the present application.
  • FIG. 10 is a schematic diagram of another photovoltaic power generation system corresponding to a multi-channel photovoltaic string provided by an embodiment of the present application;
  • FIG. 11 is a flowchart of yet another method for detecting a ground fault of a photovoltaic string provided by an embodiment of the present application.
  • FIG. 12 is a schematic diagram of a photovoltaic device provided by an embodiment of the application.
  • FIG. 13 is a schematic diagram of another photovoltaic device provided by an embodiment of the application.
  • FIG. 14 is a schematic diagram of a photovoltaic power generation system provided by an embodiment of the present application.
  • the following takes a single-string photovoltaic string as an example to introduce the working conditions in the event of a ground fault, and analyzes the technology provided by the embodiments of the present application in combination with the ground fault Scenarios are based on how they work.
  • the ground fault is introduced.
  • the inverter is not allowed to start.
  • the impedance corresponding to the power-on For example, a short-circuit fault to ground is a special case of a ground fault.
  • FIG. 1 this figure is a schematic diagram of a ground fault of a single photovoltaic string according to an embodiment of the present application.
  • the photovoltaic string shown in FIG. 1 includes N photovoltaic cell panels connected in series, including photovoltaic cell panels 1, 2...x,...N-1,N.
  • the positive pole of the PV string is PV+, and the negative pole of the PV string is PV-.
  • N is an integer greater than or equal to 2.
  • the impedance model corresponding to FIG. 1 can be seen in FIG. 2 .
  • the resistance value of the internal resistance R0 of the photovoltaic panel is much smaller than the ground resistance Rg of the photovoltaic panel.
  • one photovoltaic panel has a ground fault, that is, the potential of the photovoltaic panel with the ground fault is approximately the reference zero potential, so the number of the photovoltaic panel at the fault location can be calculated by the following formula:
  • this figure is a schematic diagram of two strings of photovoltaic strings provided by an embodiment of the present application.
  • Each photovoltaic string includes 6 photovoltaic panels connected in series. As shown in FIG. 3 , the first photovoltaic string 100 includes photovoltaic panels 1-6, and the second photovoltaic string 200 includes photovoltaic panels 1-6.
  • the first photovoltaic string 100 and the second photovoltaic string 200 are in the same photovoltaic power generation system and have the same reference point, but the positive and negative poles of the first photovoltaic string 100 and the second photovoltaic string 200 are independent of each other, that is, PV1+ and PV2+ do not have connected together, PV1- and PV2- are not connected together.
  • the fourth photovoltaic cell panel 4 of the first photovoltaic string 100 has a ground fault.
  • the second photovoltaic string 200 has no ground fault.
  • the PV1-to-ground voltage is obtained by dividing the internal resistance R0 of the battery, that is,
  • the ground voltage of the second photovoltaic string 200 is still determined by its ground resistance Rg.
  • Rg ground resistance
  • Upv2 remains unchanged and the voltage value of Upv1 is changed
  • the first PV string The voltage of the string 100 to ground also becomes 0V. If Upv1 remains unchanged and Upv2 is changed, the voltage of Upv1- is still proportional to Upv1.
  • the technical solution adopted in the embodiment of the present application is to disturb the voltage of the photovoltaic string in the photovoltaic power generation system, and sample the ground voltage of the photovoltaic string (ie terminal voltage), compare the terminal voltage before and after the disturbance, you can judge whether the PV string has a ground fault, and when it is determined that the PV string has a ground fault, the PV+ ground voltage or PV- ground fault is further determined.
  • the proportional relationship of the voltage to the PV voltage yields the specific fault location.
  • the PV string is connected to the input end of the DC/DC DC/DC conversion circuit, and the output end of the DC/DC conversion circuit is used to connect to the inverter circuit.
  • the DC/DC conversion circuit and the inverter circuit can be integrated in the inverter, and the controller of the inverter can be used to detect the ground fault of the photovoltaic string.
  • a controller can be set independently to realize the detection of the photovoltaic string. Ground fault detection.
  • the inverter may be a single-phase inverter or a three-phase inverter, which is not specifically limited in the embodiments of the present application.
  • the following takes a three-phase inverter as an example to introduce, that is, the output end of the inverter outputs three-phase alternating current, which are L1, L2 and L3 respectively.
  • FIG. 4 is a schematic diagram of a photovoltaic power generation system corresponding to a single photovoltaic string provided in an embodiment of the present application.
  • the photovoltaic string 100 is connected to the input end of the inverter 300.
  • PV+ is connected to the positive input end of the DC/DC conversion circuit 301
  • PV- is connected to the DC/DC converter
  • the negative input terminal of the circuit 301, the DC/DC conversion circuit 301 is connected to the input terminal of the inverter circuit 302, and the output terminal of the inverter circuit 302 can be connected to the AC power grid.
  • the photovoltaic string includes N photovoltaic panels connected in series.
  • the numbering of photovoltaic panels starts from the positive PV+ near the PV string 100, that is, the photovoltaic panel connected to PV+ is the first photovoltaic panel, and the photovoltaic panel connected to PV- is the fifth photovoltaic panel.
  • N is greater than or equal to 2
  • a photovoltaic string includes at least two photovoltaic panels connected in series.
  • a ground fault may occur at any position in the photovoltaic string, and in the embodiment of the present application, only one ground fault occurs in one photovoltaic string is taken as an example for description.
  • the specific implementation manner of the DC/DC conversion circuit 301 and the inverter circuit 302 is not specifically limited in the embodiments of the present application.
  • the DC/DC conversion circuit 301 may be a booster circuit, a buck circuit or a buck-boost circuit, or may not have DC.
  • the photovoltaic modules are directly connected to the DC/AC circuit.
  • this embodiment does not specifically limit the specific topology of the inverter circuit 302 .
  • the method for detecting a photovoltaic string-to-ground fault can be applied to the controller of the inverter 300, and can also be applied to other controllers, such as a photovoltaic power station controller,
  • FIG. 5 is a flowchart of a method for detecting a ground fault of a photovoltaic string provided by an embodiment of the present application.
  • the method includes:
  • S501 Obtain the terminal voltage of each photovoltaic string before the voltage disturbance, and the terminal voltage is the voltage of the positive pole to the ground of the photovoltaic string or the voltage of the negative pole to the ground;
  • the terminal voltage before the voltage disturbance is obtained, that is, the PV+-to-ground voltage or PV-to-ground voltage before the disturbance.
  • the simplest control method before the voltage disturbance is to not control the PV string.
  • the output voltage of the PV string is generally its open-circuit voltage. .
  • S502 Perform voltage disturbance on each photovoltaic string respectively, and obtain the terminal voltage of each photovoltaic string after the voltage disturbance;
  • controlling the input voltage of the DC/DC conversion circuit 301 can realize the control of the output voltage of the photovoltaic string 100. Specifically, it can be realized by the controller of the inverter 300, or by Other control devices are implemented, which are not specifically limited in this embodiment.
  • controlling the output voltage of the photovoltaic string 100 to change from large to small or controlling the output voltage of the photovoltaic string 100 to change from small to large, or controlling the open-circuit voltage to the short-circuit voltage.
  • scanning control can be performed along the current-voltage IV curve of the photovoltaic module, so that the photovoltaic string 100 works at a certain point of the curve.
  • the output voltage of the photovoltaic string subjected to voltage disturbance is controlled to change from an open circuit voltage before the voltage disturbance to a first preset voltage after the voltage disturbance, where the first preset voltage is smaller than the open circuit voltage.
  • the first preset voltage may be a voltage corresponding to any one of the operating points that is smaller than the open circuit voltage.
  • S503 Determine the PV string with ground fault according to the terminal voltage before the voltage disturbance of each PV string and the terminal voltage after the voltage disturbance;
  • Whether a ground fault occurs in the PV string 100 can be judged according to the difference of Upv+ before and after the voltage disturbance, or it can be judged by the difference of Upv- before and after the voltage disturbance.
  • the photovoltaic string is a photovoltaic string with a ground fault.
  • the preset threshold may be set according to an actual application scenario, and the specific value is not specifically limited in this embodiment.
  • the voltage disturbance is performed between the open-circuit voltage and the short-circuit voltage, and the output voltage of the photovoltaic string is controlled to jump 300V to the short-circuit voltage point, and then the jump of the terminal voltage is judged.
  • Upv2 since the output voltage of the PV string changes from large to small, Upv2 is smaller than Upv1, therefore, Upv2-Upv1 is a negative value, therefore, when the absolute value of the difference between Upv2 and Upv1 is greater than the preset threshold, determine the photovoltaic The string has a ground fault.
  • Upv1 and Upv2 may be the positive pole-to-ground voltage or the negative pole-to-ground voltage.
  • Control the output voltage of the PV string to jump to the open-circuit voltage For example, first control the output voltage of the PV string to 600V, the sampling terminal voltage Upv1, and perform voltage disturbance, and control the output voltage of the PV string to 900V, that is, the voltage has increased by 300V , the sampling terminal voltage is Upv2, and the difference between Upv2 and Upv1 is obtained. Since the output voltage of the PV string increases from small to large, Upv2 is greater than Upv1. Therefore, Upv2-Upv1 is a positive value, and the difference between Upv2 and Upv1 is greater than the expected value. When the threshold is set, it is determined that there is a ground fault in this PV string.
  • the third type control the output voltage of the PV string from the open-circuit voltage to the short-circuit voltage.
  • Voltage disturbance controls the output voltage of the PV string from open-circuit voltage to short-circuit voltage, that is, the short-circuit voltage after the voltage disturbance is 0, that is, the output voltage changes from large to 0, and the sampling terminal voltage is also close to 0, then confirm that the PV string There is a ground fault.
  • the ratio of the terminal voltage to the output voltage of the photovoltaic string can be based on the ratio of the terminal voltage before the voltage disturbance to the output voltage of the photovoltaic string, or the ratio of the terminal voltage and the output voltage of the photovoltaic string after the disturbance.
  • N and x here represent percentages, that is, N represents 100%, and the percentage represented by x is the distance between the photovoltaic strings.
  • a fault at a percentage of PV+, eg x 20%, would indicate a fault to ground at about 20%. In order to locate the ground fault more accurately, the voltage sampling near the short-circuit point can be avoided as much as possible.
  • the ratio of Upv+ before voltage disturbance to Upv before voltage disturbance is used to obtain the photovoltaic panel with ground fault.
  • the above is only an introduction to a specific implementation method. As long as there is a certain proportional relationship between the terminal voltage and the output voltage of the entire string, the specific ground fault location can be determined. The above ratio is not necessarily exactly 2/ 5. There is a slight deviation due to differences in sampling or the actual working environment, but the corresponding ground fault photovoltaic panel can be determined as long as it is within the preset deviation range.
  • ground fault of a photovoltaic panel not only refers to the short circuit to the ground of the photovoltaic panel itself, but also the short circuit to the ground caused by the insulation damage of the series cables before and after it.
  • the output voltage of the photovoltaic string is disturbed, that is, the output voltage of the photovoltaic string is controlled to change, and the terminal voltage of the photovoltaic string before the change and the terminal voltage of the photovoltaic string after the change are used to determine Determine whether the PV string has a ground fault.
  • the terminal voltage before the voltage disturbance and the terminal voltage after the voltage disturbance change significantly it indicates that the PV string has a ground fault.
  • All photovoltaic panels in the photovoltaic string are connected in series. When a ground fault occurs at a certain position in the photovoltaic string, the potential at the ground fault is approximately equal to the reference ground.
  • the voltage obtained by the photovoltaic panel can be regarded as the terminal voltage.
  • the specific location of the ground fault can be determined by using the ratio of the terminal voltage to the output voltage of the entire string.
  • the method is simple and easy to implement, does not require any additional hardware equipment, and does not need to manually detect the N photovoltaic panels of the photovoltaic string one by one, so that the photovoltaic panels with ground faults can be automatically determined, and the efficiency is high.
  • each photovoltaic string corresponds to its own DC/DC conversion circuit, that is, the photovoltaic string
  • DC/DC conversion circuit that is, the photovoltaic string
  • each PV string is independent and is connected to its corresponding DC/DC conversion circuit, the input control and sampling of each PV string do not affect each other, and each PV string can independently perform voltage disturbance, which can simultaneously perform voltage For the disturbance, the voltage disturbance may be performed in a time-sharing manner, which is not specifically limited in the embodiments of the present application.
  • this figure is a schematic diagram of a photovoltaic power generation system corresponding to a plurality of photovoltaic strings provided in an embodiment of the present application.
  • three photovoltaic strings are used as an example for description, namely a first photovoltaic string 100a, a second photovoltaic string 100b, and a third photovoltaic string 100c, wherein the first photovoltaic string 100a and the second photovoltaic string All strings 100b have ground faults.
  • each of the three photovoltaic strings includes 5 photovoltaic panels connected in series, from PV+ to PV- are the first to fifth photovoltaic panels.
  • the first photovoltaic string 100a is connected to the input end of the first DC/DC conversion circuit 301a;
  • the second photovoltaic string 100b is connected to the input end of the second DC/DC conversion circuit 301b;
  • the third photovoltaic string 100c is connected to the input end of the third DC/DC conversion circuit 301c.
  • the output terminals of the first DC/DC conversion circuit 301 a , the second DC/DC conversion circuit 301 b and the third DC/DC conversion circuit 301 c are all connected to the input terminal of the inverter circuit 302 .
  • the outputs of the first DC/DC conversion circuit 301a, the second DC/DC conversion circuit 301b and the third DC/DC conversion circuit 301c may be connected in parallel to the same bus.
  • the first DC/DC conversion circuit 301a, the second DC/DC conversion circuit 301b, the third DC/DC conversion circuit 301c, and the inverter circuit 302 may be integrated inside the inverter.
  • the fourth photovoltaic cell panel in the first photovoltaic string 100a has a ground fault
  • the first photovoltaic cell panel in the second photovoltaic string 100b has a ground fault
  • the specific implementation manner of judging the first photovoltaic string 100a and the second photovoltaic string 100b may use the method introduced in the first embodiment of the method, which will not be repeated here. For example, Upv+ before and after the voltage disturbance can be detected to judge whether the ground fault occurs, and Upv- before and after the voltage disturbance can also be detected to judge whether the ground fault has occurred.
  • the photovoltaic cell panel with the ground fault is obtained.
  • FIG. 7 is a flowchart of another method for detecting a ground fault of a photovoltaic string provided by an embodiment of the present application.
  • S701-S703 are respectively the same as S501-S503, and will not be repeated here.
  • the photovoltaic panel with ground fault is obtained by the following formula:
  • the photovoltaic panel with the ground fault can be obtained by the following formula:
  • Upv+ represents the positive-to-ground voltage before the voltage disturbance
  • Upv- represents the negative-to-ground voltage before the voltage disturbance
  • Upv represents the output voltage before the voltage disturbance
  • N represents the series-connected PV strings included in the ground fault
  • the number of photovoltaic panels, x represents the xth photovoltaic panel starting from the positive pole of the photovoltaic string with the ground fault.
  • the above formula is based on the principle that N photovoltaic panels are connected in series.
  • the Upv+/Upv of the photovoltaic string is x/N. Since both Upv+ and Upv can be obtained through the voltage detection circuit, and N is a known number, x can be obtained, and x is the photovoltaic panel with a ground fault.
  • the photovoltaic panel that determines the ground fault can also be obtained by the negative-to-ground voltage and output voltage of the photovoltaic string before the disturbance, that is, when the xth photovoltaic panel is short-circuited to the ground, the photovoltaic string is ( 1-
  • the open-circuit voltage U1 when the first photovoltaic string 100a is in an open circuit and the open-circuit voltage U2 when the second photovoltaic string 100b is in an open circuit are respectively collected before the voltage disturbance.
  • the PV-to-ground voltage U1- when the first photovoltaic string 100a is open-circuit and the PV-to-ground voltage U2- when the second photovoltaic string 100b is open-circuit are collected respectively.
  • the photovoltaic panel x1 (1-U1-
  • Photovoltaic panel x2 (1-
  • Figure 7 describes the use of the ratio of the terminal voltage before the disturbance to the output voltage before the disturbance to determine the location of the ground fault.
  • the following describes the use of the ratio of the terminal voltage after the disturbance to the output voltage after the disturbance to determine the location of the ground fault. .
  • FIG. 8 is a flowchart of another method for detecting a ground fault of a photovoltaic string provided by an embodiment of the present application.
  • S801-S703 are respectively the same as S501-S503, and are not repeated here.
  • the photovoltaic panel with ground fault is obtained by the following formula:
  • the photovoltaic panel with the ground fault can be obtained by the following formula:
  • Uv+ represents the positive-to-ground voltage after the voltage disturbance
  • Uv- represents the negative-to-ground voltage after the voltage disturbance
  • Uv represents the output voltage after the voltage disturbance
  • N represents the series-connected PV strings included in the ground fault
  • the number of photovoltaic panels, x represents the xth photovoltaic panel starting from the positive pole of the photovoltaic string with the ground fault.
  • the above formula is based on the principle that N photovoltaic panels are connected in series.
  • the Uv+/Uv of the photovoltaic string is x/N. Since both Uv+ and Uv can be obtained through the voltage detection circuit, and N is a known number, x can be obtained, and x is the photovoltaic panel with a ground fault.
  • the photovoltaic panel that determines the ground fault can also be obtained by the negative-to-ground voltage and output voltage of the photovoltaic string before the disturbance, that is, when the xth photovoltaic panel is short-circuited to the ground, the photovoltaic string is ( 1-
  • the PV string does not perform any control, and works at the operating point corresponding to the open-circuit voltage.
  • the output voltage of the PV string is controlled to decrease from the open-circuit voltage.
  • FIG. 6 it is only introduced that three photovoltaic strings correspond to three DC/DC conversion circuits, and each string includes five photovoltaic panels as an example.
  • the technical solution provided in this embodiment does not limit the specific photovoltaic strings.
  • the number of channels and the number of photovoltaic panels are shown in FIG. 9 , which is a schematic diagram of a universal photovoltaic system provided by the embodiment of the present application.
  • the photovoltaic system includes m photovoltaic strings in total, where m is an integer greater than or equal to 2, and each photovoltaic string corresponds to a DC/DC or DC/AC conversion circuit.
  • Each photovoltaic string includes n photovoltaic panels connected in series, where n is an integer greater than or equal to 2.
  • the number of PV strings with ground faults is not limited. As long as there is only one ground fault in each PV string, the method provided in this embodiment can precisely locate the fault location.
  • the method provided in this embodiment can be applied to the detection of ground faults when the inverter corresponds to multiple photovoltaic strings.
  • Multiple photovoltaic strings have neither a common positive pole nor a common negative pole, and are independently connected to the corresponding DC/DC.
  • the DC/AC conversion circuit when a ground fault occurs in one or more strings, the change of the terminal voltage before and after the voltage disturbance can accurately determine whether the PV string has a ground fault, and when only one PV string exists When a ground fault occurs, the photovoltaic panel with ground fault can be obtained through the proportional relationship between the terminal voltage and the output voltage.
  • the method is simple and easy to implement, does not require any additional hardware equipment, and does not need to manually detect the N photovoltaic panels of the photovoltaic string one by one, so that the photovoltaic panels with ground faults can be automatically determined, and the efficiency is high.
  • This embodiment introduces multi-channel photovoltaic strings, each photovoltaic string corresponds to its own DC/DC or DC/AC conversion circuit, that is, one photovoltaic string corresponds to one DC/DC conversion circuit, but the positive The input terminals or the negative input terminals are shorted together, for example, the positive input terminals of all the conversion circuits are shorted together, or the negative input terminals of all the conversion circuits are shorted together.
  • FIG. 10 is a schematic diagram of another photovoltaic power generation system corresponding to a plurality of photovoltaic strings provided by the embodiment of the present application.
  • the negative input terminals of all the DC/DC conversion circuits are short-circuited together, that is, the PV- of each photovoltaic string is short-circuited, and the PV+ of each photovoltaic string is independently connected to the corresponding DC/DC conversion circuit. of the positive input.
  • three photovoltaic strings are used as an example for description, namely a first photovoltaic string 100a, a second photovoltaic string 100b, and a third photovoltaic string 100c, wherein the first photovoltaic string 100a and the second photovoltaic string All strings 100b have ground faults.
  • the three photovoltaic strings include 5 photovoltaic panels connected in series, from PV+ to PV- are the first to fifth photovoltaic panels.
  • the first photovoltaic string 100a is connected to the input end of the first DC/DC conversion circuit 301a;
  • the second photovoltaic string 100b is connected to the input end of the second DC/DC conversion circuit 301b;
  • the third photovoltaic string 100c is connected to the input end of the third DC/DC conversion circuit 301c.
  • the negative input terminals of the first DC/DC conversion circuit 301a, the second DC/DC conversion circuit 301b and the third DC/DC conversion circuit 301c are all connected together, that is, PV- are all shorted together, so the three PV strings are Upv-equal. .
  • the negative input terminals of the first DC/DC conversion circuit 301a, the second DC/DC conversion circuit 301b and the third DC/DC conversion circuit 301c are all connected together.
  • the outputs of the first DC/DC conversion circuit 301a, the second DC/DC conversion circuit 301b and the third DC/DC conversion circuit 301c may be connected in parallel.
  • the first DC/DC conversion circuit 301a, the second DC/DC conversion circuit 301b, the third DC/DC conversion circuit 301c, and the inverter circuit 302 may be integrated inside the inverter.
  • FIG. 11 is a flowchart of yet another method for detecting a ground fault of a photovoltaic string provided by an embodiment of the present application.
  • S1101 Collect the ground voltage Upv- of PV- shorted together before the voltage disturbance
  • S1102 Perform voltage disturbance on the first photovoltaic string
  • voltage disturbance mode please refer to the introduction of the above embodiment, and it is sufficient to not perform any control on the photovoltaic strings of the other circuits.
  • voltage disturbance is first performed on the first photovoltaic string 100a.
  • S1103 Collect the PV--to-ground voltage Upv- after the voltage disturbance.
  • Each photovoltaic string can be disturbed one by one. This embodiment does not limit starting from the first photovoltaic string, that is, does not limit the sequence of each photovoltaic string whose voltage is disturbed.
  • Upv- is the voltage of the negative electrode of the PV array as a whole to the ground.
  • S1104 When the absolute value of the difference between Upv- before the voltage disturbance and Upv- after the voltage disturbance is greater than a preset threshold, determine that the first photovoltaic string has a ground fault.
  • S1105 Perform S1102-S1104 on other PV strings to determine whether a ground fault occurs.
  • the position of the photovoltaic panel with the ground fault can be accurately obtained only when only one string has a ground fault.
  • a ground fault occurs, only the photovoltaic string with ground fault can be accurately determined, and the position of the specific photovoltaic panel with ground fault cannot be accurately obtained.
  • the PV- of each PV string is shorted together as an example for introduction.
  • the PV- of each PV string can also be independent of each other, and the PV+ of each PV string is shorted together.
  • the voltage disturbance of the PV strings can accurately determine whether there is a ground fault in each PV string.
  • the position of the faulty photovoltaic panel can be accurately located by using the ratio between the terminal voltage and the output voltage.
  • an embodiment of the present application also provides a photovoltaic device, the working principle of which is described in detail below with reference to the accompanying drawings.
  • this figure is a schematic diagram of a photovoltaic device for detecting ground faults according to an embodiment of the present application.
  • a photovoltaic device for detecting a ground fault provided by an embodiment of the present application includes: a power conversion circuit, a controller 400, and a voltage detection circuit 500;
  • the power conversion circuits are in one-to-one correspondence with photovoltaic strings, and each photovoltaic string is connected to the corresponding power conversion circuit; that is, one power conversion circuit corresponds to one photovoltaic string, and the power conversion circuit may be a DC/DC conversion circuit , can also be a DC/AC conversion circuit. Since the photovoltaic strings are in one-to-one correspondence with the power conversion circuit, individual control of the photovoltaic strings can be realized.
  • two photovoltaic strings are used as an example for introduction, namely a first photovoltaic string 100 a and a second photovoltaic string 100 b.
  • the first photovoltaic string 100a is connected to the corresponding first power conversion circuit 300a, and the second photovoltaic string 100b is connected to the corresponding second power conversion circuit 300b.
  • the voltage detection circuit 500 is used to obtain the terminal voltage of each photovoltaic string before the voltage disturbance, and the terminal voltage is the positive-to-ground voltage or the negative-to-ground voltage of the photovoltaic string;
  • each photovoltaic string may be provided with a voltage detection circuit, or multiple photovoltaic strings may share a voltage detection circuit, which is not specifically limited in this embodiment.
  • the controller 400 is configured to perform voltage disturbance on each of the photovoltaic strings respectively;
  • the controller 400 can simultaneously control the first photovoltaic string 100a and the second photovoltaic string 100b Perform a voltage perturbation.
  • the controller 400 needs to sequentially perform voltage disturbance on the first photovoltaic string 100a and the second photovoltaic string 100b.
  • the output voltage of the photovoltaic string subjected to voltage disturbance is controlled to change from an open circuit voltage before the voltage disturbance to a first preset voltage after the voltage disturbance, where the first preset voltage is smaller than the open circuit voltage.
  • the first preset voltage may be a voltage corresponding to any one of the operating points that is smaller than the open circuit voltage.
  • the voltage detection circuit 500 is further configured to obtain the terminal voltage of each photovoltaic string after the voltage disturbance;
  • the controller 400 is further configured to determine the photovoltaic string with ground fault according to the terminal voltage of each photovoltaic string before voltage disturbance and the terminal voltage after voltage disturbance; for the photovoltaic string with ground fault, Use the terminal voltage and output voltage of the photovoltaic string before the voltage disturbance to obtain the photovoltaic panel with ground fault, or use the terminal voltage and output voltage of the photovoltaic string after the voltage disturbance to obtain the photovoltaic panel with ground fault.
  • the voltage detection circuit 500 can also obtain the output voltage of the photovoltaic string before the voltage disturbance.
  • the voltage detection circuit 500 can also obtain the output voltage of the photovoltaic string after the voltage disturbance.
  • the position of the controller 400 is not specifically limited in this embodiment, and may be a controller corresponding to a power conversion circuit, that is, each power conversion circuit corresponds to one controller. It is also possible that the power conversion circuits share one controller, and each power conversion circuit can communicate with the controller.
  • Whether a ground fault occurs in the PV string can be judged by the difference between Upv+ before and after the voltage disturbance, or by the difference between Upv- before and after the voltage disturbance.
  • the photovoltaic string is a photovoltaic string with a ground fault.
  • the ratio of the terminal voltage to the output voltage of the photovoltaic string can be based on the ratio of the terminal voltage before the voltage disturbance to the output voltage of the photovoltaic string, or the ratio of the terminal voltage and the output voltage of the photovoltaic string after the disturbance.
  • N and x here represent percentages, that is, N represents 100%, and the percentage represented by x is the distance between the photovoltaic strings.
  • a fault at a percentage of PV+, eg x 20%, would indicate a fault to ground at about 20%.
  • the photovoltaic device provided in this embodiment may be in the form shown in FIG. 4 , or in the form shown in FIG. 6 , or in the form shown in FIG. 10 .
  • the negative input terminals of all DC/DC conversion circuits in FIG. 10 are connected to Together, in addition, the positive input terminals of all DC/DC conversion circuits may be connected together.
  • FIG. 13 is a schematic diagram of another photovoltaic device for detecting ground faults provided by an embodiment of the present application.
  • the photovoltaic device shown in FIG. 13 does not include a DC/DC conversion circuit, but only includes a DC/AC conversion circuit, that is, when the photovoltaic device is an inverter, the inverter is a single-stage inverter, as shown in FIGS. 6 and 10 .
  • the inverter shown is a two-stage inverter, which includes both a DC/DC conversion circuit and a DC/AC conversion circuit.
  • the first photovoltaic string 100a is connected to the corresponding first DC/AC conversion circuit 300a, and the second photovoltaic string 100b is connected to the corresponding second DC/AC conversion circuit 300b.
  • the voltage detection circuit 500 is used to detect the terminal voltage and output voltage of the first photovoltaic string 100a and the second photovoltaic string 100b before the voltage disturbance, and is also used to detect the first photovoltaic string 100a and the second photovoltaic string 100b after the voltage disturbance.
  • the voltage detection circuit 500 sends both the detected terminal voltage and the output voltage to the controller 400 .
  • the controller 400 controls the output voltage of the first photovoltaic string 100a by controlling the input voltage of the first DC/AC conversion circuit 300a, and controls the output voltage of the second photovoltaic string 100b by controlling the input voltage of the second DC/AC conversion circuit 300b. output voltage, thereby realizing voltage disturbance to the first photovoltaic string 100a and the second photovoltaic string 100b.
  • the ratio of Upv+ before voltage disturbance to Upv before voltage disturbance is used to obtain the photovoltaic panel with ground fault.
  • the above is only an introduction to a specific implementation method. As long as there is a certain proportional relationship between the terminal voltage and the output voltage of the entire string, the specific ground fault location can be determined. The above ratio is not necessarily exactly 2/ 5. There is a slight deviation due to differences in sampling or the actual working environment, but the corresponding ground fault photovoltaic panel can be determined as long as it is within the preset deviation range.
  • ground fault of a photovoltaic panel not only refers to the short circuit to the ground of the photovoltaic panel itself, but also the short circuit to the ground caused by the insulation damage of the series cables before and after it.
  • the photovoltaic equipment provided in this embodiment by perturbing the output voltage of the photovoltaic string, that is, controlling the output voltage of the photovoltaic string to change, uses the terminal voltage of the photovoltaic string before the voltage disturbance and the voltage of the photovoltaic string after the voltage disturbance.
  • the terminal voltage is used to judge whether the PV string has a ground fault. When the terminal voltage before the voltage disturbance and the terminal voltage after the voltage disturbance change significantly, it indicates that the PV string has a ground fault.
  • All photovoltaic panels in the photovoltaic string are connected in series. When a ground fault occurs at a certain position in the photovoltaic string, the potential at the ground fault is approximately equal to the reference ground.
  • the voltage obtained by the photovoltaic panel can be regarded as the terminal voltage.
  • the specific location of the ground fault can be determined by using the ratio of the terminal voltage to the output voltage of the entire string.
  • the method is simple and easy to implement, does not require any additional hardware equipment, and does not need to manually detect the N photovoltaic panels of the photovoltaic string one by one, so that the photovoltaic panels with ground faults can be automatically determined, and the efficiency is high.
  • the faulty PV panel can be obtained by the ratio of the terminal voltage before the voltage disturbance to the output voltage of the PV string, or by the ratio of the terminal voltage after the voltage disturbance to the output voltage of the PV string.
  • the details are as follows. introduce.
  • the first is to use the terminal voltage before the voltage disturbance and the output voltage of the entire string before the voltage disturbance.
  • the controller is specifically used to obtain the photovoltaic cell panel with ground fault through the following formula when the terminal voltage is the positive-to-ground voltage:
  • the photovoltaic panel with ground fault is obtained by the following formula:
  • Upv+ represents the positive-to-ground voltage before the voltage disturbance
  • Upv- represents the negative-to-ground voltage before the voltage disturbance
  • Upv represents the output voltage before the voltage disturbance
  • N represents the series-connected photovoltaic cells included in the PV string with the ground fault.
  • the number of panels, x represents the xth photovoltaic panel starting from the positive pole of the photovoltaic string with ground fault.
  • the above formula is based on the principle that N photovoltaic panels are connected in series.
  • the Upv+/Upv of the photovoltaic string is x/N. Since both Upv+ and Upv can be obtained through the voltage detection circuit, and N is a known number, x can be obtained, and x is the photovoltaic panel with a ground fault.
  • the photovoltaic panel that determines the ground fault can also be obtained by the negative-to-ground voltage and output voltage of the photovoltaic string before the disturbance, that is, when the xth photovoltaic panel is short-circuited to the ground, the photovoltaic string is ( 1-
  • the open-circuit voltage U1 when the first photovoltaic string 100a is in an open circuit and the open-circuit voltage U2 when the second photovoltaic string 100b is in an open circuit are respectively collected before the voltage disturbance.
  • the PV-to-ground voltage U1- when the first photovoltaic string 100a is open-circuit and the PV-to-ground voltage U2- when the second photovoltaic string 100b is open-circuit are collected respectively.
  • the photovoltaic panel x1 (1-U1-
  • Photovoltaic panel x2 (1-
  • the above describes the use of the ratio of the terminal voltage before the disturbance to the output voltage before the disturbance to determine the location of the ground fault.
  • the following describes the use of the ratio of the terminal voltage after the disturbance to the output voltage after the disturbance to determine the location of the ground fault.
  • the second is to use the terminal voltage after voltage disturbance and the output voltage of the entire string after voltage disturbance.
  • the controller is specifically configured to use the ratio of the terminal voltage after the voltage disturbance of the photovoltaic string with the ground fault to the output voltage after the voltage disturbance, and the number N of the photovoltaic panels in series to obtain the photovoltaic panel with the ground fault.
  • the controller is specifically used to obtain the photovoltaic cell panel with ground fault through the following formula when the terminal voltage is the positive-to-ground voltage:
  • the photovoltaic panel with ground fault is obtained by the following formula:
  • Uv+ represents the positive-to-ground voltage after voltage disturbance
  • Uv- represents the negative-to-ground voltage after voltage disturbance
  • Uv represents the output voltage after voltage disturbance
  • N represents the series-connected photovoltaic cells included in the photovoltaic string with the ground fault
  • x represents the xth photovoltaic panel starting from the positive pole of the photovoltaic string with ground fault.
  • the PV string does not perform any control, and works at the operating point corresponding to the open-circuit voltage.
  • the output voltage of the PV string is controlled to decrease from the open-circuit voltage.
  • connection relationship between photovoltaic equipment and photovoltaic strings is shown in Figure 4 and Figure 6, no matter if there are one or more photovoltaic strings, as long as one ground fault occurs in one string, the connection can be realized. Precise location of fault location.
  • connection relationship between photovoltaic equipment and photovoltaic strings is shown in Figure 10, since the PV- of all photovoltaic strings are short-circuited together, it is not possible to perform voltage disturbance on two or more photovoltaic strings at the same time. Perform voltage disturbances on each PV string respectively.
  • the voltage disturbance of the PV strings can accurately determine whether there is a ground fault in each PV string.
  • the position of the faulty photovoltaic panel can be accurately located by using the ratio between the terminal voltage and the output voltage.
  • the position of the ground fault in the photovoltaic string can be accurately located.
  • all PV strings with ground faults can be identified, and when only one ground fault exists in one PV string, The fault location can be pinpointed.
  • all PV strings with ground faults can be identified.
  • the terminal voltage and output voltage can be used The ratio relationship can accurately locate the location of the faulty photovoltaic panel.
  • the embodiments of the present application also provide a photovoltaic power generation system, which will be described in detail below with reference to the accompanying drawings.
  • this figure is a schematic diagram of a photovoltaic power generation system provided by an embodiment of the present application.
  • Embodiments of the present application provide a photovoltaic power generation system, including: a photovoltaic array, a photovoltaic device, and a controller;
  • the photovoltaic array includes m photovoltaic strings, where m is an integer greater than or equal to 1;
  • the photovoltaic device includes m power conversion circuits; the power conversion circuits are in one-to-one correspondence with the photovoltaic strings, and each of the photovoltaic strings is connected to the corresponding power conversion circuit;
  • the controller is used to obtain the terminal voltage of each photovoltaic string before the voltage disturbance, and the terminal voltage is the positive-to-ground voltage or the negative-to-ground voltage of the photovoltaic string; the voltage disturbance is respectively performed on each of the photovoltaic strings, Obtain the terminal voltage of each photovoltaic string after the voltage disturbance respectively; determine the photovoltaic string with ground fault according to the terminal voltage of each photovoltaic string before the voltage disturbance and the terminal voltage after the voltage disturbance; For photovoltaic strings, use the terminal voltage and output voltage of the photovoltaic string before the voltage disturbance to obtain the photovoltaic panel with ground fault, or use the terminal voltage and output voltage of the photovoltaic string after the voltage disturbance to obtain the photovoltaic panel with ground fault.
  • the controller is specifically configured to determine that the photovoltaic string is a photovoltaic group with ground fault when the absolute value of the difference between the terminal voltage before the voltage disturbance of the photovoltaic string and the terminal voltage after the voltage disturbance exceeds a preset threshold string.
  • the controller is specifically configured to control the output voltage of the photovoltaic string disturbed by the voltage to change in the direction of voltage increase, or to change in the direction of voltage decrease.
  • the controller is specifically configured to control the output voltage of the photovoltaic string disturbed by the voltage to change from an open-circuit voltage before the voltage disturbance to a first preset voltage after the voltage disturbance, where the first preset voltage is smaller than the open-circuit voltage.
  • the controller is specifically configured to control the output voltage of the photovoltaic string disturbed by the voltage to change from the open-circuit voltage before the voltage disturbance to the short-circuit voltage after the voltage disturbance.
  • the controller is specifically configured to use the ratio of the terminal voltage to the output voltage before the voltage disturbance of the photovoltaic string with the ground fault, and the number N of photovoltaic cell panels connected in series to obtain the photovoltaic cell panel with the ground fault.
  • the controller is specifically used to obtain the photovoltaic cell panel with ground fault through the following formula when the terminal voltage is the positive-to-ground voltage:
  • the photovoltaic panel with ground fault is obtained by the following formula:
  • Upv+ represents the positive-to-ground voltage before the voltage disturbance
  • Upv- represents the negative-to-ground voltage before the voltage disturbance
  • Upv represents the output voltage before the voltage disturbance
  • N represents the series-connected photovoltaic cells included in the PV string with the ground fault.
  • the number of panels, x represents the xth photovoltaic panel starting from the positive pole of the photovoltaic string with ground fault.
  • the controller is specifically configured to use the ratio of the terminal voltage after the voltage disturbance of the photovoltaic string with the ground fault to the output voltage after the voltage disturbance, and the number N of the photovoltaic panels in series to obtain the photovoltaic panel with the ground fault.
  • the controller is specifically used to obtain the photovoltaic cell panel with ground fault through the following formula when the terminal voltage is the positive-to-ground voltage:
  • the photovoltaic panel with ground fault is obtained by the following formula:
  • Uv+ represents the positive-to-ground voltage after voltage disturbance
  • Uv- represents the negative-to-ground voltage after voltage disturbance
  • Uv represents the output voltage after voltage disturbance
  • N represents the series-connected photovoltaic cells included in the photovoltaic string with the ground fault
  • x represents the xth photovoltaic panel starting from the positive pole of the photovoltaic string with ground fault.
  • the photovoltaic power generation system provided in this embodiment includes: a photovoltaic array 100 and the photovoltaic device 1000 described in the above embodiments;
  • the photovoltaic array 100 includes M photovoltaic strings, where M is an integer greater than or equal to 1;
  • the photovoltaic device 100 includes M of the power conversion circuits.
  • the M photovoltaic strings in the photovoltaic array 100 have a one-to-one relationship with the M power conversion circuits in the photovoltaic device 1000 , that is, the input end of each power conversion circuit is connected to its corresponding photovoltaic string.
  • the photovoltaic device may be an inverter or a combiner box, which may be specifically limited in the embodiments of the present application.
  • the inverter may be a two-level inverter, as shown in FIG. 6 , which may include a DC/DC conversion circuit and a DC/AC conversion circuit.
  • the inverter can also be a single-stage inverter, that is, only includes a DC/AC conversion circuit, as shown in FIG. 13 .
  • the controller in the photovoltaic power generation system specifically implements the implementation of the ground fault of the photovoltaic components, which can be referred to the descriptions of the method embodiments and the photovoltaic device embodiments, and will not be repeated here.
  • the photovoltaic power generation system includes the photovoltaic equipment described in the above embodiments.
  • the ground fault in the photovoltaic string can be accurately located. s position.
  • all PV strings with ground faults can be identified, and when only one ground fault exists in one PV string, The fault location can be pinpointed.
  • all PV strings with ground faults can be identified.
  • the terminal voltage and output voltage can be used The ratio relationship can accurately locate the location of the faulty photovoltaic panel.
  • the photovoltaic power generation system can realize the ground fault monitoring of the photovoltaic array before the inverter is connected to the grid.
  • the DC insulation resistance is low, that is, when a ground fault occurs, the fault can be removed according to the located fault location in time, so that the photovoltaic
  • the power generation system can operate normally as soon as possible, connect to the grid for power generation, and improve work efficiency.
  • At least one (item) refers to one or more, and "a plurality” refers to two or more.
  • “And/or” is used to describe the relationship between related objects, indicating that there can be three kinds of relationships, for example, “A and/or B” can mean: only A, only B, and both A and B exist , where A and B can be singular or plural.
  • the character “/” generally indicates that the related objects are an “or” relationship.
  • At least one item(s) below” or similar expressions thereof refer to any combination of these items, including any combination of single item(s) or plural items(s).
  • At least one (a) of a, b or c can mean: a, b, c, "a and b", “a and c", “b and c", or "a and b and c" ", where a, b, c can be single or multiple.

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  • Photovoltaic Devices (AREA)
  • Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
  • Emergency Protection Circuit Devices (AREA)
  • Supply And Distribution Of Alternating Current (AREA)
  • Control Of Electrical Variables (AREA)
  • Inverter Devices (AREA)

Abstract

本申请公开了一种光伏发电系统、检测光伏组串对地故障的方法及设备，系统中的功率变换电路与光伏组串一一对应；控制器获得电压扰动前各个光伏组串的端电压，端电压为光伏组串的正极对地电压或负极对地电压；对各个光伏组串分别进行电压扰动，分别获得电压扰动后各个光伏组串的端电压；根据每个光伏组串电压扰动前的端电压和电压扰动后的端电压确定对地故障的光伏组串；对对地故障的光伏组串，利用电压扰动前光伏组串的端电压和输出电压获得对地故障的光伏电池板，或利用电压扰动后光伏组串的端电压和输出电压获得对地故障的光伏电池板。该方案简单易于实现，不需增加任何硬件，不需要人工逐一检测，可自动确定对地故障的光伏电池板，效率高。

Description

一种光伏发电系统、检测光伏组串对地故障的方法及设备 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、检测光伏组串对地故障的方法及设备。
背景技术
目前，光伏发电越来越受重视，光伏阵列输出的直流电经过逆变器变换为交流电后可以反馈给交流电网。为了提高功率输出，光伏阵列一般包括多个光伏组串并联在一起。
实际应用中，光伏阵列容易发生对地故障，即对地故障。常见的引发光伏阵列对地故障包括：光伏阵列的线缆绝缘损坏、光伏组串内部对地短路，或者由于天气等原因导致的光伏阵列对地短时短路等。当光伏阵列发生对地故障时会引起较大的漏电流，从而可能引发安全事故。
IEC标准62109-2规定，光伏逆变器开机前需要对光伏阵列对地的直流绝缘阻抗进行检测，对于非隔离型应用场景，在直流绝缘阻抗较低(无法满足漏电流要求)时，不允许逆变器开机，直到直流绝缘阻抗恢复到正常值。
目前，光伏发电系统通过检测直流绝缘阻抗判断发生对地故障时，无法确定具体的对地故障位置，需要人工到现场对光伏组串进行逐一排查，排查时间较长，效率低。
申请内容
本申请提供了一种光伏发电系统、检测光伏组串对地故障的方法及设备，能够检测光伏组串是否对地故障，且能够自动判断具体的故障位置，且效率较高。
本申请实施例提供一种光伏发电系统，包括：光伏阵列、光伏设备和控制器；光伏阵列包括m个光伏组串，所述m为大于等于1的整数；光伏设备包括m个功率变换电路；所述功率变换电路与所述光伏组串一一对应，每个所述光伏组串连接对应的所述功率变换电路；控制器，用于在电压扰动前，获得各个光伏组串的端电压，端电压为光伏组串的正极对地电压或负极对地电压，即PV+或PV-对地的电压；对各个所述光伏组串分别进行电压扰动，分别获得电压扰动后各个光伏组串的端电压；当光伏组串的内部发生对地故障时，光伏组串的端电压在电压扰动前后会有明显的变化。根据每个所述光伏组串电压扰动前的端电压和电压扰动后的端电压确定对地故障的光伏组串；对所述对地故障的光伏组串，利用电压扰动前光伏组串的端电压和输出电压获得对地故障的光伏电池板，或利用电压扰动后光伏组串的端电压和输出电压获得对地故障的光伏电池板。
其中，光伏设备可以为逆变器，光伏设备包括直流/直流DC/DC变换电路和直流/交流DC/AC变换电路，光伏组串连接在直流/直流DC/DC变换电路的输入端，DC/DC变换电路的输出端用于连接逆变电路。其中，DC/DC变换电路和逆变电路可以集成在逆变器内部，利用逆变器的控制器实现对光伏组串对地故障的检测，当然也可以独立设置一个控制器实现对光伏组串对地故障的检测。其中，逆变器内部可以没有DC/DC电路，仅有DC/AC变换电路。其中，逆变器可以为单相逆变器，也可以为三相逆变器。
当电压扰动前的端电压和电压扰动后的端电压发生明显变化时表明该光伏组串发生 对地故障。由于光伏组串中的所有光伏电池板串联在一起，当光伏组串内某一处发生对地短路时，则发生对地故障的位置的电位为参考地，因此导致光伏组串的端电压的参考电位以对地故障处的地电位为参考电位，利用端电压与整串的输出电压的比例可以确定出发生对地故障的具体位置。该方法简单易行，不需要额外增加任何硬件设备，而且不需要人工对光伏组串的N个光伏电池板进行逐一检测，便可以自动确定出对地故障的光伏电池板，检测效率较高。
优选地，不限定时扰动前的端电压减去扰动后的端电压，还是扰动后的端电压减去扰动前的端电压，主要是看电压变化量的一个绝对值。因为电压扰动可能控制端电压向增大方向变化，也可能控制端电压向减小方向变化。所述控制器，具体用于当所述光伏组串电压扰动前的端电压与电压扰动后的端电压的差值的绝对值超过预设阈值时，确定该路光伏组串为对地故障的光伏组串。
优选地，所述控制器，具体用于控制被电压扰动的光伏组串的输出电压沿着电压增大的方向变化，或者沿着电压减小的方向变化。
优选地，因为开路电压一般是最大电压，即不必控制，默认状态时就是开路电压。所述控制器，具体用于控制被电压扰动的光伏组串的输出电压从电压扰动前的开路电压变化到电压扰动后的第一预设电压，所述第一预设电压小于所述开路电压。
优选地，一般情况下，进行电流电压扫描时，都是从开路电压控制到短路电压，即从大电压变化到较小的电压。所述控制器，具体用于控制被电压扰动的光伏组串的输出电压从电压扰动前的开路电压变化到电压扰动后的短路电压。
优选地，由于光伏组串中的光伏电池板都是串联关系，串联的各个光伏电池板对光伏组串两端的电压进行分压，因此，可以通过比例来获得具体的对地故障位置。所述控制器，具体用于利用所述对地故障的光伏组串电压扰动前的端电压和输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板。
优选地，所述控制器，具体用于当所述端电压为正极对地电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(Upv+/Upv)；
当所述端电压为负极对地电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(1-|Upv-|/Upv)；
其中，Upv+表示电压扰动前的正极对地电压，Upv-表示电压扰动前的负极对地电压，Upv表示电压扰动前的输出电压；N表示发生对地故障的光伏组串包括的串联的光伏电池板的数量，x表示所述对地故障的光伏组串从正极开始的第x块光伏电池板。
优选地，所述控制器，具体用于利用所述对地故障的光伏组串电压扰动后的端电压和电压扰动后输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板。
优选地，所述控制器，具体用于当所述端电压为正极对地电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(Uv+/Uv)；
当所述端电压为负极对地电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(1-|Uv-|/Uv)；
其中，Uv+表示电压扰动后的正极对地电压，Uv-表示电压扰动后的负极对地电压，Uv表示电压扰动后的输出电压；N表示发生对地故障的光伏组串包括的串联的光伏电池板的数量，x表示所述对地故障的光伏组串从正极开始的第x块光伏电池板。
本申请实施例还提供一种检测光伏组串对地故障的方法，包括：获得电压扰动前各个光伏组串的端电压，所述端电压为光伏组串的正极对地电压或负极对地电压；对各个所述光伏组串分别进行电压扰动，分别获得电压扰动后各个光伏组串的端电压；根据每个所述光伏组串电压扰动前的端电压和电压扰动后的端电压确定对地故障的光伏组串；对所述对地故障的光伏组串，利用电压扰动前光伏组串的端电压和输出电压获得对地故障的光伏电池板，或利用电压扰动后光伏组串的端电压和输出电压获得对地故障的光伏电池板。
当电压扰动前的端电压和电压扰动后的端电压发生明显变化时表明该光伏组串发生对地故障。由于光伏组串中的所有光伏电池板串联在一起，当光伏组串内某一处发生对地短路时，则发生对地故障的位置的电位为参考地，因此导致光伏组串的端电压的参考电位以对地故障处的地电位为参考电位，利用端电压与整串的输出电压的比例可以确定出发生对地故障的具体位置。该方法简单易行，不需要额外增加任何硬件设备，而且不需要人工对光伏组串的N个光伏电池板进行逐一检测，便可以自动确定出对地故障的光伏电池板，检测效率较高。
优选地，所述根据每个所述光伏组串电压扰动前的端电压和电压扰动后的端电压确定对地故障的光伏组串，具体包括：当所述光伏组串电压扰动前的端电压与电压扰动后的端电压的差值的绝对值超过预设阈值时，确定该路光伏组串为对地故障的光伏组串。
优选地，所述对各个所述光伏组串分别进行电压扰动，具体包括：控制被电压扰动的光伏组串的输出电压沿着电压增大的方向变化，或者沿着电压减小的方向变化。
优选地，所述控制被电压扰动的光伏组串的输出电压沿着电压减小的方向变化，具体包括：控制被电压扰动的光伏组串的输出电压从电压扰动前的开路电压变化到电压扰动后的第一预设电压，所述第一预设电压小于所述开路电压。
优选地，电压扰动既可以从大向小的方向进行电压变化，也可以从小向大的方向变化。所述对各个所述光伏组串分别进行电压扰动，一般情况下，进行电流电压扫描时，都是从开路电压控制到短路电压，即从大电压变化到较小的电压。具体包括：控制被电压扰动的光伏组串的输出电压从电压扰动前的开路电压变化到电压扰动后的短路电压。
优选地，由于光伏组串中的光伏电池板都是串联关系，串联的各个光伏电池板对光伏组串两端的电压进行分压，因此，可以通过比例来获得具体的对地故障位置。所述利用电压扰动前光伏组串的端电压和输出电压获得对地故障的光伏电池板，具体包括：利用所述对地故障的光伏组串电压扰动前的端电压和输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板。
优选地，利用所述对地故障的光伏组串电压扰动前的端电压和电压扰动前的输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板，具体包括：当所述端电压为正极对地电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(Upv+/Upv)；
当所述端电压为负极对地电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(1-|Upv-|/Upv)；
其中，Upv+表示电压扰动前的正极对地电压，Upv-表示电压扰动前的负极对地电压，Upv表示电压扰动前的输出电压；N表示发生对地故障的光伏组串包括的串联的光伏电池板的数量，x表示所述对地故障的光伏组串从正极开始的第x块光伏电池板。
优选地，所述利用电压扰动后光伏组串的端电压和电压扰动后的输出电压获得对地故障的光伏电池板，具体包括：利用所述对地故障的光伏组串电压扰动后的端电压和电压扰动后输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板。
优选地，利用所述对地故障的光伏组串电压扰动后的端电压和电压扰动后输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板，具体包括：
当所述端电压为正极对地电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(Uv+/Uv)；
当所述端电压为负极对地电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(1-|Uv-|/Uv)；
其中，Uv+表示电压扰动后的正极对地电压，Uv-表示电压扰动后的负极对地电压，Uv表示电压扰动后的输出电压；N表示发生对地故障的光伏组串包括的串联的光伏电池板的数量，x表示所述对地故障的光伏组串从正极开始的第x块光伏电池板。
本申请实施例还提供一种检测对地故障的光伏设备，包括：功率变换电路、控制器和电压检测电路；所述功率变换电路与光伏组串一一对应，每个所述光伏组串连接对应的所述功率变换电路；所述电压检测电路，用于获得电压扰动前各个光伏组串的端电压，所述端电压为光伏组串的正极对地电压或负极对地电压；所述控制器，用于对各个所述光伏组串分别进行电压扰动；所述电压检测电路，还用于分别获得电压扰动后各个光伏组串的端电压；所述控制器，还用于根据每个所述光伏组串电压扰动前的端电压和电压扰动后的端电压确定对地故障的光伏组串；对所述对地故障的光伏组串，利用电压扰动前光伏组串的端电压和输出电压获得对地故障的光伏电池板，或利用电压扰动后光伏组串的端电压和输出电压获得对地故障的光伏电池板。
优选地，所述控制器，具体用于当所述光伏组串电压扰动前的端电压与电压扰动后的端电压的差值的绝对值超过预设阈值时，确定该路光伏组串为对地故障的光伏组串。
优选地，本申请实施例不限定电压扰动的方向，例如控制器控制被电压扰动的光伏组串的输出电压沿着电压增大的方向变化，或者沿着电压减小的方向变化。
优选地，控制器控制被电压扰动的光伏组串的输出电压从电压扰动前的开路电压变化到电压扰动后的第一预设电压，所述第一预设电压小于所述开路电压。即可以设定一个预设电压，扰动到该预设电压即可。
优选地，控制器利用所述对地故障的光伏组串电压扰动前的端电压和输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板。
从以上技术方案可以看出，本申请实施例具有以下优点：
通过对光伏组串的输出电压进行扰动，即控制光伏组串的输出电压发生变化，利用变化前的光伏组串的端电压和变化后的光伏组串的端电压来判断该光伏组串是否发生对地故障，光伏组串的端电压是指正极对地电压或负极对地电压。当光伏组串的内部发生对地故障时，光伏组串的端电压在电压扰动前后会有明显的变化。当电压扰动前的端电压和电压扰动后的端电压发生明显变化时表明该光伏组串发生对地故障。由于光伏组串中的所有光伏电池板串联在一起，当光伏组串内某一处发生对地短路时，则发生对地故障的位置的电位为参考地，因此导致光伏组串的端电压的参考电位以对地故障处的地电位为参考电位，利用端电压与整串的输出电压的比例可以确定出发生对地故障的具体位置。该方法简单易行，不需要额外增加任何硬件设备，而且不需要人工对光伏组串的N个光伏电池板进行逐一检测，便可以自动确定出对地故障的光伏电池板，检测效率较高。
附图说明
图1为本申请实施例提供的单个光伏组串对地故障的示意图；
图2为图1对应的阻抗模型示意图；
图3为本申请实施例提供的两个串光伏组串的示意图；
图4为本申请实施例提供的单个光伏组串对应的光伏发电系统示意图；
图5为本申请实施例提供的一种检测光伏组串对地故障的方法流程图；
图6为本申请实施例提供的多路光伏组串对应的光伏发电系统示意图；
图7为本申请实施例提供的另一种检测光伏组串对地故障的方法流程图；
图8为本申请实施例提供的又一种检测光伏组串对地故障的方法流程图；
图9为本申请实施例提供的一种普适性的光伏系统的示意图；
图10为本申请实施例提供的另一种多路光伏组串对应的光伏发电系统示意图；
图11为本申请实施例提供的再一种检测光伏组串对地故障的方法流程图；
图12为本申请实施例提供的一种光伏设备的示意图；
图13为本申请实施例提供的另一种光伏设备的示意图；
图14为本申请实施例提供的一种光伏发电系统的示意图。
具体实施方式
为了使本领域技术人员更好地理解本申请实施例提供的技术方案，下面以单串光伏组串为例介绍对地故障时的工作情况，并结合对地故障分析本申请实施例提供的技术方案基于的工作原理。
首先介绍对地故障，标准要求直流绝缘阻抗较低(无法满足漏电流要求)时，不允许逆变器开机，本申请实施例的对地故障是指直流绝缘阻抗低于标准允许的逆变器开机对应的阻抗。例如对地短路故障属于对地故障的一种特殊情况。
方法实施例一：
参见图1，该图为本申请实施例提供的单个光伏组串对地故障的示意图。
图1所示的光伏组串包括N个光伏电池板串联在一起，包括光伏电池板1、2……x、…N-1、N。光伏组串的正极为PV+，光伏组串的负极为PV-。N为大于等于2的整数。
图1对应的阻抗模型可以参见图2所示。
当光伏组串没有发生对地故障时，光伏电池板的内阻R0的阻值远小于光伏电池板的对地电阻Rg。
当光伏组串中的某一块光伏电池板发生对地故障时(大部分为对地绝缘阻抗低故障)，该光伏电池板的对地阻抗Rg变为一个接近0的小阻抗，此时，PV+对地电压Upv+和PV-对地电压Upv-与光伏组串正负极之间的电压Upv存在比例关系，其中，Upv+-Upv-＝Upv。
因为N个光伏电池板串联，有一块光伏电池板发生对地故障，即接地故障的光伏电池板的电位近似为参考零电位，所以故障位置的光伏电池板的编号可以通过以下公式计算获得：
x＝N*(1-|Upv-|/Upv)或x＝N*(Upv+/Upv)
为了使本领域技术人员更充分理解本申请实施例提供的技术方案，下面以两个光伏组串中的一串中的一处发生对地故障为例进行介绍。
参见图3，该图为本申请实施例提供的两个串光伏组串的示意图。
每路光伏组串包括6块串联的光伏电池板，如图3所示，第一光伏组串100包括光伏电池板1-6，第二光伏组串200包括光伏电池板1-6。第一光伏组串100和第二光伏组串200在同一光伏发电系统，参考地相同，但第一光伏组串100和第二光伏组串200的正级、负极相互独立，即PV1+和PV2+没有连接在一起，PV1-和PV2-没有连接在一起。
其中，第一光伏组串100的第四块光伏电池板4发生了对地故障。第二光伏组串200没有发生对地故障。
此时，PV1-对地电压由电池内阻R0分压得到，即|Upv1-|/Upv1＝2/6＝1/3。
由于第二光伏组串200的对地电压仍然由其对地阻抗Rg决定。此时若Upv2不变，改变Upv1的电压值，则第一光伏组串100的对地电压会跟随变化，其大小Upv1-＝-1/3Upv1，例如，当Upv1＝0时，第一光伏组串100对地电压也变为0V。若Upv1维持不变，改变Upv2，Upv1-的电压仍与Upv1保持比例关系。
因此，为了精确确定某个光伏组串中对地故障的光伏电池板，本申请实施例采用的技术方案是，扰动光伏发电系统中的光伏组串的电压，采样光伏组串对地电压(即端电压)，比较扰动前后的端电压，即可判断该路光伏组串是否发生对地故障，当确定该串光伏组串发生对地故障时，再进一步由PV+对地电压或PV-对地电压与PV电压的比例关系得到具体的故障位置。
为了便于理解，下面先介绍对于一路光伏组串对地故障的判断，光伏组串连接在直流/直流DC/DC变换电路的输入端，DC/DC变换电路的输出端用于连接逆变电路。其中，DC/DC变换电路和逆变电路可以集成在逆变器内部，利用逆变器的控制器实现对光伏组串对地故障的检测，当然也可以独立设置一个控制器实现对光伏组串对地故障的检测。其中，逆变器内部可以没有DC/DC电路，仅有DC/AC变换电路。其中，逆变器可以为单相逆变器，也可以为三相逆变器，本申请实施例中不作具体限定。
下面以三相逆变器为例进行介绍，即逆变器的输出端输出三相交流电，分别为L1、L2和L3。
参见图4，该图为本申请实施例提供的单个光伏组串对应的光伏发电系统示意图。
本实施例以单个光伏组串为例进行介绍，光伏组串100连接在逆变器300的输入端，具体为，PV+连接DC/DC变换电路301的正输入端，PV-连接DC/DC变换电路301的负输入端，DC/DC变换电路301连接逆变电路302的输入端，逆变电路302的输出端可以连接交流电网。
光伏组串包括N个串联在一起的光伏电池板，图4中仅是以N＝5为例进行介绍，以5块光伏电池板中的第2块发生对地故障为例。光伏电池板的编号是从靠近光伏组串100的正极PV+开始，即连接PV+的光伏电池板为第1块光伏电池板，连接PV-的光伏电池板为第5块光伏电池板。一般情况下，N大于等于2，即一路光伏组串至少包括2块光伏电池板串联。光伏组串中任何位置均有可能发生对地故障，本申请实施例中仅以一路光伏组串中仅有一处发生对地故障为例进行介绍。
本申请实施例中不具体限定DC/DC变换电路301和逆变电路302的具体实现方式，例如DC/DC变换电路301可以为升压电路，降压电路或升降压电路，也可以没有DC/DC电路，光伏组件直接连接到DC/AC电路上。同样本实施例也不具体限定逆变电路302的具体拓扑形式。
本实施例提供的检测光伏组串对地故障的方法，可以应用于逆变器300的控制器中，也可以应用于其他控制器中，例如光伏电站控制器中，
参见图5，该图为本申请实施例提供的一种检测光伏组串对地故障的方法流程图。
该方法包括：
S501：获得电压扰动前各个光伏组串的端电压，端电压为光伏组串正极对地的电压或负极对地的电压；
对于图4所示的光伏组串，获得电压扰动前的端电压，即扰动前的PV+对地电压或PV-对地电压。
具体实现时，电压扰动前最简单的控制方式就是对光伏组串不进行任何控制，当不控制光伏组串的输出电压时，光伏组串的输出电压一般为其开路电压。。
S502：对各个光伏组串分别进行电压扰动，分别获得电压扰动后各个光伏组串的端电压；
图4所示的仅包括一个光伏组串，即控制DC/DC变换电路301的输入电压可以实现光伏组串100的输出电压的控制，具体可以由逆变器300的控制器实现，也可以由其他控制装置实现，本实施例中不作具体限定。
具体的电压扰动方式包括很多种，例如，控制光伏组串100的输出电压从大向小变化，或者，控制光伏组串100的输出电压从小向大变化，或者从开路电压控制为短路电压。一般可以沿着光伏组件的电流-电压IV曲线进行扫描控制，使光伏组串100工作在曲线某一点。
例如，当控制被电压扰动的光伏组串的输出电压沿着电压减小的方向变化，具体包括：
控制被电压扰动的光伏组串的输出电压从电压扰动前的开路电压变化到电压扰动后的第一预设电压，所述第一预设电压小于所述开路电压。
第一预设电压可以是小于开路电压的任意一个工作点对应的电压。
S503：根据每个光伏组串电压扰动前的端电压和电压扰动后的端电压确定对地故障的光伏组串；
当光伏组串100中的某个光伏电池板发生对地故障时，光伏组串100的正极PV+对地电压Upv+会与扰动前的对地电压明显不同，同理，光伏组串100的负极PV-对地电压Upv-在扰动前后也明显不同。
对于该光伏组串100是否发生对地故障，可以根据Upv+在电压扰动前后的差值来判断是否发生短路故障，也可以通过Upv-在电压扰动前后的差值来判断是否发生短路故障。
例如，当所述光伏组串电压扰动前的端电压与电压扰动后的端电压的差值的绝对值超过预设阈值时，确定该路光伏组串为对地故障的光伏组串。
预设阈值可以根据实际的应用场景进行设置，具体的取值在本实施例中不作具体限定。
下面具体举例进行说明，分别以三种来举例；
第一种：控制光伏组串的输出电压从大向小变化。
在开路电压与短路电压之间进行电压扰动，控制光伏组串的输出电压向短路电压点跳变300V，进而判断端电压的跳变。例如先控制光伏组串的输出电压为600V，采样端电压为Upv1，进行电压扰动，控制光伏组串的输出电压为300V，即电压降低了300V，采样端电压为Upv2，获得Upv2与Upv1的差值，由于光伏组串的输出电压由大变小，因此，Upv2小于Upv1，因此，Upv2-Upv1为负值，因此，Upv2与Upv1的差值的绝对值大于预设阈值时，确定该路光伏组串发生对地故障。
需要说明的是，Upv1、Upv2可以为正极对地电压，也可以为负极对地电压。
第二种：控制光伏组串的输出电压从小向大变化。
控制光伏组串的输出电压向开路电压跳变，例如先控制光伏组串的输出电压为600V，采样端电压Upv1，进行电压扰动，控制光伏组串的输出电压为900V，即电压升高了300V，采样端电压为Upv2，获得Upv2与Upv1的差值，由于光伏组串的输出电压由小变大，因此，Upv2大于Upv1，因此，Upv2-Upv1为正值，Upv2与Upv1的差值大于预设阈值时，确定该路光伏组串发生对地故障。
第三种：控制光伏组串的输出电压从开路电压变为短路电压。
电压扰动控制光伏组串的输出电压从开路电压变为短路电压，即电压扰动后的短路电压为0，即输出电压从大向0变化，采样端电压也接近0，则确认该路光伏组串存在对地故障。
S504：对存在对地故障的光伏组串，利用电压扰动前光伏组串的端电压和输出电压获得对地故障的光伏电池板，或利用电压扰动后光伏组串的端电压和输出电压获得对地故障的光伏电池板。
对于一路光伏组串，当只有一处发生对地故障时，光伏组串的端电压与光伏组串的输出电压存在比例关系，因此，可以利用端电压与光伏组串的输出电压的比例关系，获得光伏组串中对地故障的光伏电池板的位置。
其中，端电压与光伏组串的输出电压的比例，可以利用电压扰动之前的端电压和光伏组串的输出电压的比例，也可以利用扰动之后的端电压和光伏组串的输出电压的比例。
以图4为例，由于5块光伏电池板串联在PV+和PV-之间。当第2块光伏电池板发生对地故障时，无论是电压扰动前，还是电压扰动后，当检测Upv+的绝对值与Upv的比例为2/5，或者Upv-的绝对值与Upv的比例为3/5时，均表明是第2块光伏电池板发生了对地故障。需要说明的是：此处第2块光伏电池板是指从PV+端开始数的第2块光伏电池板。另外，当有的光伏阵列不知道其中每个光伏组串包括的光伏电池板的数量时，此处的N和x表示百分比，即N表示100％，x表示的百分比即是光伏组串中距离PV+的百分比处发生的故障，例如x＝20％，则表明约20％处发生对地故障。为了对地故障的定位更准确，可以尽量避开短路点附近的电压采样。
例如，利用电压扰动前的Upv+与电压扰动前的Upv的比例获得发生对地故障的光伏电池板。
需要说明的是，以上仅是介绍一种具体的实现方式，只要端电压和整串的输出电压存在一定的比例关系，便可以确定具体的对地故障位置，以上的比例不一定恰好是2/5，因为采样或者实际工作的环境有所差异，出现稍微的偏差，但是只要在预设的偏差范围内即可确定对应的对地故障光伏电池板。
需要说明的是，某块光伏电池板对地故障不仅是指光伏电池板本身对地发生了短路，也可以是其前后的串联线缆绝缘破损导致的对地短路。
本实施例提供的方法，通过对光伏组串的输出电压进行扰动，即控制光伏组串的输出电压发生变化，利用变化前的光伏组串的端电压和变化后的光伏组串的端电压来判断该光伏组串是否发生对地故障。电压扰动前的端电压和电压扰动后的端电压发生明显变化时表明该光伏组串发生对地故障。光伏组串中的所有光伏电池板串联在一起，当光伏组串中某一位置发生对地故障时，对地故障处的电位与参考地近似相等，此时从光伏组串一端到故障处所有光伏电池板分得的电压即可认为是端电压，因而，利用端电压与整串的输出电压的比例可以确定出发生对地故障的具体位置。该方法简单易行，不需要额外增加任何硬件设备，而且不需要人工对光伏组串的N个光伏电池板进行逐一检测，便可以自动确定出对地故障的光伏电池板，效率较高。
方法实施例二：
以上实施例是以逆变器对应一路光伏组串为例进行的介绍，下面介绍一个逆变器对应多路光伏组串，每路光伏组串对应各自的DC/DC变换电路，即光伏组串与DC/DC变换电路是一对一的对应关系，而且各个DC/DC变换电路各自独立，正输入端或负输入端并没有短接在一起。由于各个光伏组串独立，分别连接各自对应的DC/DC变换电路，因此，每路光伏组串的输入控制和采样互不影响，各个光伏组串可以分别独立进行电压扰动，既可以同时进行电压扰动，可以分时进行电压扰动，本申请实施例中均不作具体限定。
参见图6，该图为本申请实施例提供的多个光伏组串对应的光伏发电系统示意图。
本实施例中以三个光伏组串为例进行说明，分别为第一光伏组串100a、第二光伏组串100b和第三光伏组串100c，其中第一光伏组串100a和第二光伏组串100b均发生对地故障。并且三个光伏组串均包括5块光伏电池板串联，从PV+至PV-依次为第1块至第5块光伏 电池板。
第一光伏组串100a连接第一DC/DC变换电路301a的输入端；
第二光伏组串100b连接第二DC/DC变换电路301b的输入端；
第三光伏组串100c连接第三DC/DC变换电路301c的输入端。
第一DC/DC变换电路301a、第二DC/DC变换电路301b和第三DC/DC变换电路301c的输出端均连接逆变电路302的输入端。第一DC/DC变换电路301a、第二DC/DC变换电路301b和第三DC/DC变换电路301c的输出端可以并联接到同一母线。
第一DC/DC变换电路301a、第二DC/DC变换电路301b、第三DC/DC变换电路301c和逆变电路302可以集成在逆变器的内部。
其中，第一光伏组串100a中的第4块光伏电池板发生对地故障，第二光伏组串100b中的第1块光伏电池板发生对地故障。
判断第一光伏组串100a和第二光伏组串100b的具体实现方式可以利用方法实施例一介绍的方式，在此不再赘述。例如可以检测电压扰动前后的Upv+来判断是否发生对地故障，也可以检测电压扰动前后的Upv-来判断是否发生对地故障。
利用电压扰动前光伏组串的端电压和输出电压获得对地故障的光伏电池板，具体包括：
利用所述对地故障的光伏组串电压扰动前的端电压和输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板。
即，当确定第一光伏组串100a和第二光伏组串100b发生对地故障时，利用第一光伏组串100a扰动前的端电压与扰动前的输出电压的比例和N＝5来确定发生对地故障的位置。同理，利用第二光伏组串100b扰动前的端电压与电压扰动前的输出电压的比例和N＝5来确定发生对地故障的位置。
参见图7，该图为本申请实施例提供的另一种检测光伏组串对地故障的方法流程图。
S701-S703分别与S501-S503相同，在此不再赘述。
S704：对发生对地故障的光伏组串，利用所述对地故障的光伏组串电压扰动前的端电压和电压扰动前的输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板。
具体包括：
当所述端电压为正极对地的电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(Upv+/Upv)；
当所述端电压为负极对地的电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(1-|Upv-|/Upv)；
其中，Upv+表示电压扰动前的正极对地的电压，Upv-表示电压扰动前的负极对地的电压，Upv表示电压扰动前的输出电压；N表示发生对地故障的光伏组串包括的串联的光伏电池板的数量，x表示所述对地故障的光伏组串从正极开始的第x块光伏电池板。
以上公式基于的原理是N个光伏电池板串联，当第x块光伏电池板对地短路时，该光伏组串的Upv+/Upv为x/N。由于Upv+和Upv均可以通过电压检测电路获得，而N又是已知数，因此，可以获得x，x便是发生对地故障的光伏电池板。同理确定对地故障的光伏电 池板也可以通过扰动前的光伏组串的负极对地电压和输出电压来获得，即当第x块光伏电池板对地短路时，该光伏组串的为(1-|Upv-|/Upv)为x/N。由于Upv-和Upv均可以通过电压检测电路获得，而N又是已知数，因此，可以获得x。
例如，分别电压扰动前采集第一光伏组串100a处于开路时的开路电压U1和第二光伏组串100b处于开路时的开路电压U2。分别采集电压扰动前第一光伏组串100a处于开路时PV-对地电压U1-和第二光伏组串100b处于开路时PV-对地电压U2-。
则，第一光伏组串100a发生对地故障的光伏电池板x1＝(1-U1-|/U1)*N；
第一光伏组串100a发生对地故障的光伏电池板x2＝(1-|U2-|/U2)*N。
图7介绍的是利用扰动前的端电压和扰动前的输出电压的比例来确定对地故障的位置，下面介绍利用扰动后的端电压和扰动后的输出电压的比例来确定对地故障的位置。
参见图8，该图为本申请实施例提供的又一种检测光伏组串对地故障的方法流程图。
S801-S703分别与S501-S503相同，在此不再赘述。
S804：对发生对地故障的光伏组串，利用所述对地故障的光伏组串电压扰动后的端电压和输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板。
具体包括：
当所述端电压为正极对地的电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(Uv+/Uv)；
当所述端电压为负极对地的电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(1-|Uv-|/Uv)；
其中，Uv+表示电压扰动后的正极对地的电压，Uv-表示电压扰动后的负极对地的电压，Uv表示电压扰动后的输出电压；N表示发生对地故障的光伏组串包括的串联的光伏电池板的数量，x表示所述对地故障的光伏组串从正极开始的第x块光伏电池板。
以上公式基于的原理是N个光伏电池板串联，当第x块光伏电池板对地短路时，该光伏组串的Uv+/Uv为x/N。由于Uv+和Uv均可以通过电压检测电路获得，而N又是已知数，因此，可以获得x，x便是发生对地故障的光伏电池板。同理确定对地故障的光伏电池板也可以通过扰动前的光伏组串的负极对地电压和输出电压来获得，即当第x块光伏电池板对地短路时，该光伏组串的为(1-|Uv-|/Uv)为x/N。由于Uv-和Uv均可以通过电压检测电路获得，而N又是已知数，因此，可以获得x。
下面结合具体示例进行介绍，例如电压扰动前，光伏组串不进行任何控制，工作在开路电压对应的工作点，电压扰动时控制光伏组串的输出电压从开路电压进行降低。
图6中仅是以三个光伏组串对应三个DC/DC变换电路，每个组串包括5个光伏电池板为例进行的介绍，本实施例提供的技术方案不限定具体的光伏组串的路数以及光伏电池板的个数，如图9所示，为本申请实施例提供的一种普适性的光伏系统的示意图。
该光伏系统共包括m个光伏组串，m为大于等于2的整数，每个光伏组串对应一个DC/DC或DC/AC变换电路。每个光伏组串包括n个串联的光伏电池板，n为大于等于2的整数。并且不限定发生对地故障的光伏组串的路数，只要每路光伏组串中仅出现一处对地故障，利用本实施例提供的方法便可以精确定位故障位置。
本实施例提供的方法，可以适用于逆变器对应多个光伏组串时的对地故障的检测，多个光伏组串既不共正极，又不共负极，各自独立连接对应的DC/DC或DC/AC转换电路，在一串或多串发生对地故障时，可以通过电压扰动前后的端电压的变化准确确定该光伏组串是否发生对地故障，而且当一路光伏组串中仅存在一处对地故障时，可以通过端电压与输出电压的比例关系获得对地故障的光伏电池板。该方法简单易行，不需要额外增加任何硬件设备，而且不需要人工对光伏组串的N个光伏电池板进行逐一检测，便可以自动确定出对地故障的光伏电池板，效率较高。
方法实施例三：
本实施例介绍多路光伏组串，每路光伏组串对应各自的DC/DC或DC/AC变换电路，即一个光伏组串对应一个DC/DC变换电路，但是各个DC/DC变换电路的正输入端或负输入端短接在一起，例如所有变换电路的正输入端短接在一起，或者所有变换电路的负输入端短接在一起。
参见图10，该图为本申请实施例提供的另一种多个光伏组串对应的光伏发电系统示意图。
本实施例中以所有DC/DC变换电路的负输入端短接在一起，即各个光伏组串的PV-短接在一起，而各个光伏组串的PV+独立连接各自对应的DC/DC变换电路的正输入端。
本实施例中以三个光伏组串为例进行说明，分别为第一光伏组串100a、第二光伏组串100b和第三光伏组串100c，其中第一光伏组串100a和第二光伏组串100b均发生对地故障。并且三个光伏组串均包括5块光伏电池板串联，从PV+至PV-依次为第1块至第5块光伏电池板。
第一光伏组串100a连接第一DC/DC变换电路301a的输入端；
第二光伏组串100b连接第二DC/DC变换电路301b的输入端；
第三光伏组串100c连接第三DC/DC变换电路301c的输入端。
第一DC/DC变换电路301a、第二DC/DC变换电路301b和第三DC/DC变换电路301c的负输入端均连接在一起，即PV-均短接在一起，因此三个光伏组串的Upv-相等。。
第一DC/DC变换电路301a、第二DC/DC变换电路301b和第三DC/DC变换电路301c的负输入端均连接在一起。第一DC/DC变换电路301a、第二DC/DC变换电路301b和第三DC/DC变换电路301c的输出端可以并联在一起。
第一DC/DC变换电路301a、第二DC/DC变换电路301b、第三DC/DC变换电路301c和逆变电路302可以集成在逆变器的内部。
由于所有光伏组串的PV-短接在一起，因此不能同时对两个或两个以上的光伏组串进行电压扰动，需要先后分别对各个光伏组串进行电压扰动。
参见图11，该图为本申请实施例提供的再一种检测光伏组串对地故障的方法流程图。
S1101：采集电压扰动前短接在一起的PV-的对地电压Upv-；
S1102：对第一光伏组串进行电压扰动；
具体的电压扰动方式可以参见以上实施例的介绍，对于其余路的光伏组串不进行任何 控制即可。例如，先对第一光伏组串100a进行电压扰动。
S1103：采集电压扰动后PV-的对地电压Upv-。
可以逐一对各个光伏组串进行扰动，本实施例不限定从第一光伏组串开始，即不限定电压扰动的各个光伏组串的先后顺序。
由于各路光伏组串的PV-短接在一起，因此，设置一路PV-对地的电压采样电路即可，节省硬件成本。
由于所有光伏组串的PV-短接在一起，因此，Upv-是光伏阵列的负极整体对地的电压。
S1104：当电压扰动前的Upv-与电压扰动后的Upv-的差值的绝对值大于预设阈值时，判断第一光伏组串存在对地故障。
S1105：对其他光伏组串执行S1102-S1104判断是否发生对地故障。
由于PV-短接在一起，因此需要对各个光伏组串逐一进行电压扰动，来判断是否发生对地故障。
例如，对第二光伏组串进行电压扰动时，其他光伏组串不进行任何控制，仅控制第二光伏组串的输出电压改变。
S1106：当对所有光伏组串电压扰动完毕时，如果仅有一路光伏组串存在对地故障，则利用电压扰动前的Upv-与电压扰动前该路光伏组串的输出电压的比值获得对地故障的光伏电池板。
例如，当所有光伏组串电压扰动完毕，判断仅有第一光伏组串存在对地故障时，利用x＝(1-|Upv-|/U1)*N，获得第一光伏组串中对地故障的光伏电池板。其中U1为第一光伏组串的输出电压。
本实施例提供的方法，由于各个光伏组串的正极或负极连接在一起，因此，只能当仅有一串存在对地故障时，可以准确获得对地故障的光伏电池板的位置，当多串发生对地故障时，仅能准确判断出对地故障的光伏组串，并不能准确获得对地故障的具体光伏电池板的位置。
本实施例中仅是以各个光伏组串的PV-短接在一起为例进行介绍，同理，各个光伏组串的PV-也可以相互独立，而各个光伏组串的PV+短接在一起。
本申请实施例提供的方法，对于多路光伏组串的一端短接在一起时，即光伏阵列中的多路光伏组串的正极短接在一起，或负极短接在一起，依次对每路光伏组串进行电压扰动，可以准确判断各个光伏组串是否存在对地故障。当只有一处存在对地故障时，利用端电压与输出电压的比值关系，可以准确定位故障的光伏电池板的位置。
光伏设备实施例一
基于以上实施例提供的一种检测光伏组串对地故障方法，本申请实施例还提供一种光伏设备，下面结合附图对其工作原理进行详细介绍。
参见图12，该图为本申请实施例提供的一种检测对地故障的光伏设备的示意图。
本申请实施例提供的一种检测对地故障的光伏设备，包括：功率变换电路、控制器400和电压检测电路500；
所述功率变换电路与光伏组串一一对应，每个所述光伏组串连接对应的所述功率变换电路；即一个功率变换电路对应一个光伏组串，功率变换电路可以为DC/DC变换电路，也可以为DC/AC变换电路。由于光伏组串与功率变换电路一一对应，因此可以实现对光伏组串的单独控制。
图12中以两个光伏组串为例进行介绍，分别为第一光伏组串100a和第二光伏组串100b。
第一光伏组串100a连接对应的第一功率变换电路300a，第二光伏组串100b连接对应的第二功率变换电路300b。
所述电压检测电路500，用于获得电压扰动前各个光伏组串的端电压，所述端电压为光伏组串的正极对地电压或负极对地电压；
需要说明的是，每个光伏组串可以设置一个电压检测电路，也可以多个光伏组串共用一个电压检测电路，本实施例中不作具体限定。
所述控制器400，用于对各个所述光伏组串分别进行电压扰动；
当第一功率变换电路300a和第二功率变换电路300b的正输入端和负输入端均独立，不连接在一起时，控制器400可以同时对第一光伏组串100a和第二光伏组串100b进行电压扰动。当第一功率变换电路300a和所述功率变换电路300b的正输入端或负输入端连接在一起时，控制器400需要依次对第一光伏组串100a和第二光伏组串100b进行电压扰动。
具体的电压扰动方式包括很多种，例如，控制光伏组串的输出电压从大向小变化，或者，控制光伏组串的输出电压从小向大变化，或者从开路电压控制为短路电压。一般可以沿着光伏组件的电流-电压IV曲线进行扫描控制，使光伏组串100工作在IV曲线某一点。
例如，当控制被电压扰动的光伏组串的输出电压沿着电压减小的方向变化，具体包括：
控制被电压扰动的光伏组串的输出电压从电压扰动前的开路电压变化到电压扰动后的第一预设电压，所述第一预设电压小于所述开路电压。
第一预设电压可以是小于开路电压的任意一个工作点对应的电压。
所述电压检测电路500，还用于分别获得电压扰动后各个光伏组串的端电压；
所述控制器400，还用于根据每个所述光伏组串电压扰动前的端电压和电压扰动后的端电压确定对地故障的光伏组串；对所述对地故障的光伏组串，利用电压扰动前光伏组串的端电压和输出电压获得对地故障的光伏电池板，或利用电压扰动后光伏组串的端电压和输出电压获得对地故障的光伏电池板。
需要说明的是，定位对地故障位置时，当利用电压扰动前的电压参数时，电压检测电路500还可以获得电压扰动前光伏组串的输出电压。当利用电压扰动后的电压参数时，电压检测电路500还可以获得电压扰动后光伏组串的输出电压。
本实施例中不具体限定控制器400的位置，可以为功率变换电路对应的控制器，即每个功率变换电路对应一个控制器。也可以是功率变换电路共用一个控制器，各个功率变换电路之间可以与控制器互相通信。
当光伏组串中的某个光伏电池板发生对地故障时，光伏组串的正极PV+对地电压Upv+会与扰动前的对地电压明显不同，同理，光伏组串的负极PV-对地电压Upv-在扰动前后也明显不同。
对于光伏组串是否发生对地故障，可以根据Upv+在电压扰动前后的差值来判断是否发 生短路故障，也可以通过Upv-在电压扰动前后的差值来判断是否发生短路故障。
例如，当光伏组串电压扰动前的端电压与电压扰动后的端电压的差值的绝对值超过预设阈值时，确定该路光伏组串为对地故障的光伏组串。
对于一路光伏组串，当只有一处发生对地故障时，光伏组串的端电压与光伏组串的输出电压存在比例关系，因此，可以利用端电压与光伏组串的输出电压的比例关系，获得光伏组串中对地故障的光伏电池板的位置。
其中，端电压与光伏组串的输出电压的比例，可以利用电压扰动之前的端电压和光伏组串的输出电压的比例，也可以利用扰动之后的端电压和光伏组串的输出电压的比例。
继续参见图4，由于5块光伏电池板串联在PV+和PV-之间。当第2块光伏电池板发生对地故障时，无论是电压扰动前，还是电压扰动后，当检测Upv+的绝对值与Upv的比例为2/5，或者Upv-的绝对值与Upv的比例为3/5时，均表明是第2块光伏电池板发生了对地故障。需要说明的是：此处第2块光伏电池板是指从PV+端开始数的第2块光伏电池板。另外，当有的光伏阵列不知道其中每个光伏组串包括的光伏电池板的数量时，此处的N和x表示百分比，即N表示100％，x表示的百分比即是光伏组串中距离PV+的百分比处发生的故障，例如x＝20％，则表明约20％处发生对地故障。
本实施例提供的光伏设备可以为图4所示的形式，也可以为图6所示的形式，还可以如图10所示的形式，图10中所有DC/DC变换电路的负输入端连接在一起，另外，也可以是所有DC/DC变换电路的正输入端连接在一起。
另外，当功率变换电路可以为DC/AC变换电路，参见图13所示，该图为本申请实施例提供的另一种检测对地故障的光伏设备的示意图。
图13所示的光伏设备不包括DC/DC变换电路，仅包括DC/AC变换电路，即当光伏设备为逆变器时，该逆变器为单级逆变器，图6和图10所示的逆变器为两级逆变器，既包括DC/DC变换电路，又包括DC/AC变换电路。
第一光伏组串100a连接对应的第一DC/AC变换电路300a，第二光伏组串100b连接对应的第二DC/AC变换电路300b。
电压检测电路500用于检测电压扰动前第一光伏组串100a和第二光伏组串100b的端电压和输出电压，也用于检测电压扰动后第一光伏组串100a和第二光伏组串100b的端电压和输出电压，电压检测电路500将检测端电压和输出电压均发送给控制器400。
控制器400通过控制第一DC/AC变换电路300a的输入电压来控制第一光伏组串100a的输出电压，通过控制第二DC/AC变换电路300b的输入电压来控制第二光伏组串100b的输出电压，从而实现对于第一光伏组串100a和第二光伏组串100b的电压扰动。
例如，利用电压扰动前的Upv+与电压扰动前的Upv的比例获得发生对地故障的光伏电池板。
需要说明的是，以上仅是介绍一种具体的实现方式，只要端电压和整串的输出电压存在一定的比例关系，便可以确定具体的对地故障位置，以上的比例不一定恰好是2/5，因为采样或者实际工作的环境有所差异，出现稍微的偏差，但是只要在预设的偏差范围内即可确定对应的对地故障光伏电池板。
需要说明的是，某块光伏电池板对地故障不仅是指光伏电池板本身对地发生了短路，也可以是其前后的串联线缆绝缘破损导致的对地短路。
本实施例提供的光伏设备，通过对光伏组串的输出电压进行扰动，即控制光伏组串的输出电压发生变化，利用电压扰动前的光伏组串的端电压和电压扰动后的光伏组串的端电压来判断该光伏组串是否发生对地故障。电压扰动前的端电压和电压扰动后的端电压发生明显变化时表明该光伏组串发生对地故障。光伏组串中的所有光伏电池板串联在一起，当光伏组串中某一位置发生对地故障时，对地故障处的电位与参考地近似相等，此时从光伏组串一端到故障处所有光伏电池板分得的电压即可认为是端电压，因而，利用端电压与整串的输出电压的比例可以确定出发生对地故障的具体位置。该方法简单易行，不需要额外增加任何硬件设备，而且不需要人工对光伏组串的N个光伏电池板进行逐一检测，便可以自动确定出对地故障的光伏电池板，效率较高。
定位故障的光伏电池板，可以通过电压扰动前的端电压与光伏组串的输出电压的比例获得，也可以通过电压扰动后的端电压与光伏组串的输出电压的比例获得，下面分别进行具体介绍。
第一种，利用电压扰动前的端电压和电压扰动前整串的输出电压。
控制器，具体用于当所述端电压为正极对地电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(Upv+/Upv)；
当所述端电压为负极对地电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(1-|Upv-|/Upv)；
其中，Upv+表示电压扰动前的正极对地电压，Upv-表示电压扰动前的负极对地电压，Upv表示电压扰动前的输出电压；N表示发生对地故障的光伏组串包括的串联的光伏电池板的数量，x表示所述对地故障的光伏组串从正极开始的第x块光伏电池板。
以上公式基于的原理是N个光伏电池板串联，当第x块光伏电池板对地短路时，该光伏组串的Upv+/Upv为x/N。由于Upv+和Upv均可以通过电压检测电路获得，而N又是已知数，因此，可以获得x，x便是发生对地故障的光伏电池板。同理确定对地故障的光伏电池板也可以通过扰动前的光伏组串的负极对地电压和输出电压来获得，即当第x块光伏电池板对地短路时，该光伏组串的为(1-|Upv-|/Upv)为x/N。由于Upv-和Upv均可以通过电压检测电路获得，而N又是已知数，因此，可以获得x。
例如，分别电压扰动前采集第一光伏组串100a处于开路时的开路电压U1和第二光伏组串100b处于开路时的开路电压U2。分别采集电压扰动前第一光伏组串100a处于开路时PV-对地电压U1-和第二光伏组串100b处于开路时PV-对地电压U2-。
则，第一光伏组串100a发生对地故障的光伏电池板x1＝(1-U1-|/U1)*N；
第一光伏组串100a发生对地故障的光伏电池板x2＝(1-|U2-|/U2)*N。
以上介绍的是利用扰动前的端电压和扰动前的输出电压的比例来确定对地故障的位置，下面介绍利用扰动后的端电压和扰动后的输出电压的比例来确定对地故障的位置。
第二种，利用电压扰动后的端电压和电压扰动后整串的输出电压。
控制器，具体用于利用所述对地故障的光伏组串电压扰动后的端电压和电压扰动后输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板。
控制器，具体用于当所述端电压为正极对地电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(Uv+/Uv)；
当所述端电压为负极对地电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(1-|Uv-|/Uv)；
其中，Uv+表示电压扰动后的正极对地电压，Uv-表示电压扰动后的负极对地电压，Uv表示电压扰动后的输出电压；N表示发生对地故障的光伏组串包括的串联的光伏电池板的数量，x表示所述对地故障的光伏组串从正极开始的第x块光伏电池板。
例如电压扰动前，光伏组串不进行任何控制，工作在开路电压对应的工作点，电压扰动时控制光伏组串的输出电压从开路电压进行降低。
需要说明的是，当光伏设备和光伏组串的连接关系如图4、图6所示时，无论光伏组串时一个还是多个，只要一串中发生一处对地故障，均可以实现对故障位置的精确定位。当光伏设备和光伏组串的连接关系如图10所示时，由于所有光伏组串的PV-短接在一起，因此不能同时对两个或两个以上的光伏组串进行电压扰动，需要先后分别对各个光伏组串进行电压扰动。并且图10对应的光伏设备，由于各个光伏组串的正极或负极连接在一起，因此，只能当仅有一串存在对地故障时，可以准确获得对地故障的光伏电池板的位置，当多串发生对地故障时，仅能准确判断出对地故障的光伏组串，并不能准确获得对地故障的具体光伏电池板的位置。
对于图10所示的光伏设备，对于多路光伏组串的一端短接在一起时，即光伏阵列中的多路光伏组串的正极短接在一起，或负极短接在一起，依次对每路光伏组串进行电压扰动，可以准确判断各个光伏组串是否存在对地故障。当只有一处存在对地故障时，利用端电压与输出电压的比值关系，可以准确定位故障的光伏电池板的位置。
由于各路光伏组串的PV-短接在一起，因此，设置一路PV-对地的电压采样电路即可，节省硬件成本。
以上实施例提供的光伏设备，当仅存在一个光伏组串且光伏组串仅发生一处对地故障时，可以准确定位光伏组串中的对地故障的位置。当对应多个光伏组串，且光伏组串的正极和负极均不连接在一起时，可以识别出所有对地故障的光伏组串，并且一个光伏组串中仅存在一处对地故障时，可以精确定位故障位置。当对应多个光伏组串，且所有光伏组串的正极或负极连接在一起时，可以识别出所有对地故障的光伏组串，当只有一处存在对地故障时，利用端电压与输出电压的比值关系，可以准确定位故障的光伏电池板的位置。
系统实施例
基于以上实施例提供的一种检测光伏组串对地故障和光伏设备，本申请实施例还提供一种光伏发电系统，下面结合附图进行详细的介绍。
参见图14，该图为本申请实施例提供的一种光伏发电系统的示意图。
本申请实施例提供一种光伏发电系统，包括：光伏阵列、光伏设备和控制器；
所述光伏阵列包括m个光伏组串，所述m为大于等于1的整数；
所述光伏设备包括m个功率变换电路；所述功率变换电路与所述光伏组串一一对应，每个所述光伏组串连接对应的所述功率变换电路；
所述控制器，用于获得电压扰动前各个光伏组串的端电压，所述端电压为光伏组串的正极对地电压或负极对地电压；对各个所述光伏组串分别进行电压扰动，分别获得电压扰动后各个光伏组串的端电压；根据每个所述光伏组串电压扰动前的端电压和电压扰动后的端电压确定对地故障的光伏组串；对所述对地故障的光伏组串，利用电压扰动前光伏组串的端电压和输出电压获得对地故障的光伏电池板，或利用电压扰动后光伏组串的端电压和输出电压获得对地故障的光伏电池板。
控制器，具体用于当所述光伏组串电压扰动前的端电压与电压扰动后的端电压的差值的绝对值超过预设阈值时，确定该路光伏组串为对地故障的光伏组串。
控制器，具体用于控制被电压扰动的光伏组串的输出电压沿着电压增大的方向变化，或者沿着电压减小的方向变化。
控制器，具体用于控制被电压扰动的光伏组串的输出电压从电压扰动前的开路电压变化到电压扰动后的第一预设电压，所述第一预设电压小于所述开路电压。
控制器，具体用于控制被电压扰动的光伏组串的输出电压从电压扰动前的开路电压变化到电压扰动后的短路电压。
控制器，具体用于利用所述对地故障的光伏组串电压扰动前的端电压和输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板。
控制器，具体用于当所述端电压为正极对地电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(Upv+/Upv)；
当所述端电压为负极对地电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(1-|Upv-|/Upv)；
其中，Upv+表示电压扰动前的正极对地电压，Upv-表示电压扰动前的负极对地电压，Upv表示电压扰动前的输出电压；N表示发生对地故障的光伏组串包括的串联的光伏电池板的数量，x表示所述对地故障的光伏组串从正极开始的第x块光伏电池板。
控制器，具体用于利用所述对地故障的光伏组串电压扰动后的端电压和电压扰动后输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板。
控制器，具体用于当所述端电压为正极对地电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(Uv+/Uv)；
当所述端电压为负极对地电压时，通过以下公式获得对地故障的光伏电池板：
x＝N*(1-|Uv-|/Uv)；
其中，Uv+表示电压扰动后的正极对地电压，Uv-表示电压扰动后的负极对地电压，Uv表示电压扰动后的输出电压；N表示发生对地故障的光伏组串包括的串联的光伏电池板的 数量，x表示所述对地故障的光伏组串从正极开始的第x块光伏电池板。
本实施例提供的光伏发电系统，包括：光伏阵列100和以上实施例介绍的光伏设备1000；
所述光伏阵列100包括M个光伏组串，所述M为大于等于1的整数；
所述光伏设备100包括M个所述功率变换电路。
光伏阵列100中的M个光伏组串与光伏设备1000中的M个功率变换电路是一对一的关系，即每个功率变换电路的输入端连接自身对应的一个光伏组串。
光伏设备可以为逆变器，也可以为汇流箱，本申请实施例中不错具体限定。
当光伏设备为逆变器时，逆变器可以为两级逆变器，如图6所示，可以包括DC/DC变换电路和DC/AC变换电路。逆变器也可以为单级逆变器，即仅包括DC/AC变换电路，如图13所示。
光伏发电系统中的控制器具体进行光伏组件对地故障的实现方式，可以参照方法实施例和光伏设备实施例的描述，在此不再赘述。
本申请实施例提供的光伏发电系统，包括以上实施例介绍的光伏设备，当仅存在一个光伏组串且光伏组串仅发生一处对地故障时，可以准确定位光伏组串中的对地故障的位置。当对应多个光伏组串，且光伏组串的正极和负极均不连接在一起时，可以识别出所有对地故障的光伏组串，并且一个光伏组串中仅存在一处对地故障时，可以精确定位故障位置。当对应多个光伏组串，且所有光伏组串的正极或负极连接在一起时，可以识别出所有对地故障的光伏组串，当只有一处存在对地故障时，利用端电压与输出电压的比值关系，可以准确定位故障的光伏电池板的位置。该光伏发电系统可以在逆变器并网之前，实现对光伏阵列的对地故障监测，在直流绝缘阻抗较低时，即发生对地故障时，及时根据定位的故障位置解除故障，以使光伏发电系统能够尽快正常运行，进行并网发电，提高工作效率。
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，以上实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的精神和范围。

Claims (23)

  1. 一种光伏发电系统，其特征在于，包括：光伏阵列、光伏设备和控制器；
    所述光伏阵列包括m个光伏组串，所述m为大于等于1的整数；
    所述光伏设备包括m个功率变换电路；所述功率变换电路与所述光伏组串一一对应，每个所述光伏组串连接对应的所述功率变换电路；
    所述控制器，用于获得电压扰动前各个光伏组串的端电压，所述端电压为光伏组串的正极对地电压或负极对地电压；对各个所述光伏组串分别进行电压扰动，分别获得电压扰动后各个光伏组串的端电压；根据每个所述光伏组串电压扰动前的端电压和电压扰动后的端电压确定对地故障的光伏组串；对所述对地故障的光伏组串，利用电压扰动前光伏组串的端电压和输出电压获得对地故障的光伏电池板，或利用电压扰动后光伏组串的端电压和输出电压获得对地故障的光伏电池板。
  2. 根据权利要求1所述的系统，其特征在于，所述控制器，具体用于当所述光伏组串电压扰动前的端电压与电压扰动后的端电压的差值的绝对值超过预设阈值时，确定该路光伏组串为对地故障的光伏组串。
  3. 根据权利要求1所述的系统，其特征在于，所述控制器，具体用于控制被电压扰动的光伏组串的输出电压沿着电压增大的方向变化，或者沿着电压减小的方向变化。
  4. 根据权利要求3所述的系统，其特征在于，所述控制器，具体用于控制被电压扰动的光伏组串的输出电压从电压扰动前的开路电压变化到电压扰动后的第一预设电压，所述第一预设电压小于所述开路电压。
  5. 根据权利要求4所述的系统，其特征在于，所述控制器，具体用于控制被电压扰动的光伏组串的输出电压从电压扰动前的开路电压变化到电压扰动后的短路电压。
  6. 根据权利要求2-4任一项所述的系统，其特征在于，所述控制器，具体用于利用所述对地故障的光伏组串电压扰动前的端电压和输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板。
  7. 根据权利要求6所述的系统，其特征在于，所述控制器，具体用于当所述端电压为正极对地电压时，通过以下公式获得对地故障的光伏电池板：
    x＝N*(Upv+/Upv)；
    当所述端电压为负极对地电压时，通过以下公式获得对地故障的光伏电池板：
    x＝N*(1-|Upv-|/Upv)；
    其中，Upv+表示电压扰动前的正极对地电压，Upv-表示电压扰动前的负极对地电压，Upv表示电压扰动前的输出电压；N表示发生对地故障的光伏组串包括的串联的光伏电池板的数量，x表示所述对地故障的光伏组串从正极开始的第x块光伏电池板。
  8. 根据权利要求2-4任一项所述的系统，其特征在于，所述控制器，具体用于利用所述对地故障的光伏组串电压扰动后的端电压和电压扰动后输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板。
  9. 根据权利要求8所述的系统，其特征在于，所述控制器，具体用于当所述端电压为正极对地电压时，通过以下公式获得对地故障的光伏电池板：
    x＝N*(Uv+/Uv)；
    当所述端电压为负极对地电压时，通过以下公式获得对地故障的光伏电池板：
    x＝N*(1-|Uv-|/Uv)；
    其中，Uv+表示电压扰动后的正极对地电压，Uv-表示电压扰动后的负极对地电压，Uv表示电压扰动后的输出电压；N表示发生对地故障的光伏组串包括的串联的光伏电池板的数量，x表示所述对地故障的光伏组串从正极开始的第x块光伏电池板。
  10. 一种检测光伏组串对地故障的方法，其特征在于，包括：
    获得电压扰动前各个光伏组串的端电压，所述端电压为光伏组串的正极对地电压或负极对地电压；
    对各个所述光伏组串分别进行电压扰动，分别获得电压扰动后各个光伏组串的端电压；
    根据每个所述光伏组串电压扰动前的端电压和电压扰动后的端电压确定对地故障的光伏组串；
    对所述对地故障的光伏组串，利用电压扰动前光伏组串的端电压和输出电压获得对地故障的光伏电池板，或利用电压扰动后光伏组串的端电压和输出电压获得对地故障的光伏电池板。
  11. 根据权利要求10所述的方法，其特征在于，所述根据每个所述光伏组串电压扰动前的端电压和电压扰动后的端电压确定对地故障的光伏组串，具体包括：
    当所述光伏组串电压扰动前的端电压与电压扰动后的端电压的差值的绝对值超过预设阈值时，确定该路光伏组串为对地故障的光伏组串。
  12. 根据权利要求11所述的方法，其特征在于，所述对各个所述光伏组串分别进行电压扰动，具体包括：
    控制被电压扰动的光伏组串的输出电压沿着电压增大的方向变化，或者沿着电压减小的方向变化。
  13. 根据权利要求12所述的方法，其特征在于，所述控制被电压扰动的光伏组串的输出电压沿着电压减小的方向变化，具体包括：
    控制被电压扰动的光伏组串的输出电压从电压扰动前的开路电压变化到电压扰动后的第一预设电压，所述第一预设电压小于所述开路电压。
  14. 根据权利要求13所述的方法，其特征在于，所述对各个所述光伏组串分别进行电压扰动，具体包括：
    控制被电压扰动的光伏组串的输出电压从电压扰动前的开路电压变化到电压扰动后的短路电压。
  15. 根据权利要求11-13任一项所述的方法，其特征在于，所述利用电压扰动前光伏组串的端电压和输出电压获得对地故障的光伏电池板，具体包括：
    利用所述对地故障的光伏组串电压扰动前的端电压和输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板。
  16. 根据权利要求15所述的方法，其特征在于，利用所述对地故障的光伏组串电压扰动前的端电压和电压扰动前的输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板，具体包括：
    当所述端电压为正极对地电压时，通过以下公式获得对地故障的光伏电池板：
    x＝N*(Upv+/Upv)；
    当所述端电压为负极对地电压时，通过以下公式获得对地故障的光伏电池板：
    x＝N*(1-|Upv-|/Upv)；
    其中，Upv+表示电压扰动前的正极对地电压，Upv-表示电压扰动前的负极对地电压，Upv表示电压扰动前的输出电压；N表示发生对地故障的光伏组串包括的串联的光伏电池板的数量，x表示所述对地故障的光伏组串从正极开始的第x块光伏电池板。
  17. 根据权利要求11-13任一项所述的方法，其特征在于，所述利用电压扰动后光伏组串的端电压和电压扰动后的输出电压获得对地故障的光伏电池板，具体包括：
    利用所述对地故障的光伏组串电压扰动后的端电压和电压扰动后输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板。
  18. 根据权利要求17所述的方法，其特征在于，利用所述对地故障的光伏组串电压扰动后的端电压和电压扰动后输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板，具体包括：
    当所述端电压为正极对地电压时，通过以下公式获得对地故障的光伏电池板：
    x＝N*(Uv+/Uv)；
    当所述端电压为负极对地电压时，通过以下公式获得对地故障的光伏电池板：
    x＝N*(1-|Uv-|/Uv)；
    其中，Uv+表示电压扰动后的正极对地电压，Uv-表示电压扰动后的负极对地电压，Uv表示电压扰动后的输出电压；N表示发生对地故障的光伏组串包括的串联的光伏电池板的数量，x表示所述对地故障的光伏组串从正极开始的第x块光伏电池板。
  19. 一种检测对地故障的光伏设备，其特征在于，包括：功率变换电路、控制器和电压检测电路；
    所述功率变换电路与光伏组串一一对应，每个所述光伏组串连接对应的所述功率变换电路；
    所述电压检测电路，用于获得电压扰动前各个光伏组串的端电压，所述端电压为光伏组串的正极对地电压或负极对地电压；
    所述控制器，用于对各个所述光伏组串分别进行电压扰动；
    所述电压检测电路，还用于分别获得电压扰动后各个光伏组串的端电压；
    所述控制器，还用于根据每个所述光伏组串电压扰动前的端电压和电压扰动后的端电压确定对地故障的光伏组串；对所述对地故障的光伏组串，利用电压扰动前光伏组串的端电压和输出电压获得对地故障的光伏电池板，或利用电压扰动后光伏组串的端电压和输出电压获得对地故障的光伏电池板。
  20. 根据权利要求19所述的光伏设备，其特征在于，所述控制器，具体用于当所述光伏组串电压扰动前的端电压与电压扰动后的端电压的差值的绝对值超过预设阈值时，确定该路光伏组串为对地故障的光伏组串。
  21. 根据权利要求19所述的光伏设备，其特征在于，所述控制器，具体用于控制被电压扰动的光伏组串的输出电压沿着电压增大的方向变化，或者沿着电压减小的方向变化。
  22. 根据权利要求21所述的光伏设备，其特征在于，所述控制器，具体用于控制被电压扰动的光伏组串的输出电压从电压扰动前的开路电压变化到电压扰动后的第一预设电压，所述第一预设电压小于所述开路电压。
  23. 根据权利要求20-22任一项所述的光伏设备，其特征在于，所述控制器，具体用于利用所述对地故障的光伏组串电压扰动前的端电压和输出电压的比例，及包括串联的光伏电池板数量N获得对地故障的光伏电池板。
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