WO2021208658A1 - 一种光伏发电系统的保护装置、保护方法及光伏发电系统 - Google Patents

一种光伏发电系统的保护装置、保护方法及光伏发电系统 Download PDF

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Publication number
WO2021208658A1
WO2021208658A1 PCT/CN2021/081165 CN2021081165W WO2021208658A1 WO 2021208658 A1 WO2021208658 A1 WO 2021208658A1 CN 2021081165 W CN2021081165 W CN 2021081165W WO 2021208658 A1 WO2021208658 A1 WO 2021208658A1
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Prior art keywords
current
photovoltaic
bus
branch
protection
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PCT/CN2021/081165
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English (en)
French (fr)
Inventor
张秀锋
张彦忠
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华为技术有限公司
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Family has litigation
First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=78083708&utm_source=google_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=WO2021208658(A1) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
Priority to AU2021255319A priority Critical patent/AU2021255319A1/en
Priority to EP21787590.5A priority patent/EP3961854B1/en
Priority to CN202180001510.9A priority patent/CN113826302B/zh
Priority to JP2021572645A priority patent/JP7439139B2/ja
Priority to CN202211605694.2A priority patent/CN116014681B/zh
Application filed by 华为技术有限公司 filed Critical 华为技术有限公司
Priority to BR112021023381A priority patent/BR112021023381A2/pt
Priority to CN202211600353.6A priority patent/CN116073338A/zh
Publication of WO2021208658A1 publication Critical patent/WO2021208658A1/zh
Priority to US17/535,375 priority patent/US11870238B2/en
Priority to US18/521,816 priority patent/US20240097427A1/en
Priority to JP2024019655A priority patent/JP2024040384A/ja

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/18—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to reversal of direct current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
    • H02H3/087—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current for dc applications
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/06—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric generators; for synchronous capacitors
    • H02H7/062—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric generators; for synchronous capacitors for parallel connected generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/20—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for electronic equipment
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S40/00—Components or accessories in combination with PV modules, not provided for in groups H02S10/00 - H02S30/00
    • H02S40/30—Electrical components
    • H02S40/32—Electrical components comprising DC/AC inverter means associated with the PV module itself, e.g. AC modules
    • 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
    • H02S40/00—Components or accessories in combination with PV modules, not provided for in groups H02S10/00 - H02S30/00
    • H02S40/30—Electrical components
    • H02S40/36—Electrical components characterised by special electrical interconnection means between two or more PV modules, e.g. electrical module-to-module connection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/10—Parallel operation of dc sources
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • H02J2300/26—The renewable source being solar energy of photovoltaic origin involving maximum power point tracking control for photovoltaic sources
    • 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

  • This application relates to the field of photovoltaic power generation technology, and in particular to a photovoltaic power generation system protection device, short circuit protection method, and photovoltaic power generation system.
  • Photovoltaic power generation is a technology that uses the photovoltaic effect of the semiconductor interface to convert light energy into electrical energy.
  • Photovoltaic power generation systems usually include photovoltaic units, inverters, AC power distribution equipment, and so on. Among them, in order to obtain a higher output voltage or output current, a photovoltaic unit is usually formed by a plurality of photovoltaic modules in a certain series-parallel manner. In order to improve the power generation efficiency of the photovoltaic power generation system, photovoltaic units will be connected to devices with independent MPPT (Maximum Power Point Tracking) functions to improve the power generation efficiency of the photovoltaic power generation system.
  • MPPT Maximum Power Point Tracking
  • each MPPT device is connected to at least two photovoltaic units. Take a short circuit of a photovoltaic unit or a short circuit on the line where the photovoltaic unit is located as an example.
  • the short-circuit current is the sum of the output currents of the other connected photovoltaic units.
  • the number of connected photovoltaic units is only 1, the short circuit The current is small, and the photovoltaic unit and circuit can withstand this short-circuit current.
  • the number of photovoltaic units connected to other paths is 2 or more, the short-circuit current is relatively large.
  • a fuse can be connected in series with the positive output terminal and/or negative output terminal of the photovoltaic unit. The fuse is blown to protect the photovoltaic unit and wiring.
  • the fusing current of the fuse is generally high, and the output current of each photovoltaic unit is low, it is difficult for the sum of the short-circuit current of multiple photovoltaic units to reach the fusing current of the fuse, resulting in that the fuse cannot effectively protect the photovoltaic unit. And the circuit, and the fuse has a large internal resistance, which will also cause a large power loss in the photovoltaic power generation system.
  • the present application provides a protection device, a protection method and a photovoltaic power generation system for a photovoltaic power generation system, which can effectively protect photovoltaic units and lines when the photovoltaic power generation system fails, and has low power loss.
  • an embodiment of the present application provides a protection device for a photovoltaic power generation system, which is applied to a photovoltaic power generation system.
  • the device includes: an interface, a protection switch, a DC bus, and a controller; the device is connected to at least two photovoltaic power generation systems through the interface. Unit, the at least two photovoltaic units are connected in parallel with the DC bus in the device to form at least two branches, each of the branches is connected with at least one photovoltaic unit; a protection switch is used to disconnect all Or part of the photovoltaic units are connected to the DC bus, so that at most three photovoltaic units are directly connected in parallel.
  • the controller determines that the photovoltaic power generation system is faulty according to the parameter detection value of the branch or the DC bus, the control protection switch is turned off.
  • the protection switch of the device makes at most three photovoltaic units directly connected in parallel when it is off. Therefore, when a photovoltaic unit can withstand the current output by two photovoltaic units, when a photovoltaic unit fails, at most two normal photovoltaic units output current to it, and the current is within the tolerance range of the failed photovoltaic unit. In order to protect the photovoltaic modules and lines from damage. And because only the protection switch is added to the circuit, the resistance is smaller than that of the fuse, which reduces the loss rate and loss of the photovoltaic system.
  • the Y wire harness originally used for the built-in fuse does not need to be placed under the inverter or DC combiner box of the photovoltaic power generation system, but can be placed on the photovoltaic unit side, thereby reducing the cable cost.
  • the parameter detection value is the reverse current value
  • the controller is specifically used to determine that the photovoltaic power generation system is faulty when the reverse current value of the branch is greater than the first current value .
  • the device is connected to at least three photovoltaic units through the interface, wherein at most two photovoltaic units are directly connected in parallel to the DC bus, and each of the remaining photovoltaic units is directly connected to the DC bus.
  • the photovoltaic units are respectively connected in series with at least one of the protection switches and then connected in parallel to the DC bus.
  • the photovoltaic unit or line can only withstand the output current of one photovoltaic unit.
  • the photovoltaic unit When at most two photovoltaic units are directly connected in parallel to the DC bus, if there is a short-circuit fault in the photovoltaic unit, at most one normal The photovoltaic unit outputs a short-circuit current to it, and the remaining photovoltaic units can be directly disconnected. At this time, the short-circuit current is within the tolerance of the faulty photovoltaic unit, thereby protecting the photovoltaic components and lines from damage.
  • the device is connected to at least three photovoltaic units through the interface, wherein at most three photovoltaic units are directly connected in parallel to the DC bus, and each of the remaining photovoltaic units is directly connected to the DC bus.
  • the photovoltaic units are respectively connected in series with at least one of the protection switches and then connected in parallel to the DC bus.
  • the photovoltaic unit or the line can withstand the output current of two photovoltaic units. Therefore, when at most three photovoltaic units are directly connected in parallel to the DC bus, if there is a short-circuit fault in the photovoltaic unit, there will be at most two photovoltaic units. Each normal photovoltaic unit outputs a short-circuit current to it, and the rest of the photovoltaic units can be directly disconnected. At this time, the short-circuit current is within the tolerance of the faulted photovoltaic unit, thereby protecting the photovoltaic components and lines from damage.
  • the device is connected to three photovoltaic units through the interface, wherein two photovoltaic units are directly connected in parallel to the DC bus, and the other photovoltaic unit is connected to at least one photovoltaic unit.
  • the protective switches are connected in series and then connected in parallel to the DC bus.
  • the controller can control the protection switch to open when a short-circuit fault occurs, thereby protecting the photovoltaic units and lines in the photovoltaic system.
  • the device is connected to three photovoltaic units through the interface, wherein the two photovoltaic units are respectively connected in series with at least one of the protection switches and then connected in parallel to the DC bus , Another photovoltaic unit is directly connected to the DC bus in parallel.
  • the controller can control the protection switch to open when a short-circuit fault occurs, so that the current flowing into the photovoltaic unit that has the short-circuit fault is zero, thereby protecting the photovoltaic unit and the circuit in the photovoltaic system.
  • the device is connected to four photovoltaic units through the interface, wherein the two photovoltaic units are connected in parallel and then connected in series with at least one of the protection switches, and then connected in parallel to all photovoltaic units.
  • the DC bus, and the other two photovoltaic units are directly connected in parallel to the DC bus.
  • the controller can control the protection switch to open when a short-circuit fault occurs, thereby protecting the photovoltaic units and lines in the photovoltaic system.
  • the device is connected to four photovoltaic units through the interface, wherein two photovoltaic units are directly connected in parallel, and the remaining two photovoltaic units are respectively connected to at least one of the protection switches. After being connected in series, the two photovoltaic units are connected in parallel, and then connected to the DC bus in parallel.
  • the controller can control the protection switch to turn off when a short-circuit fault occurs, thereby protecting the photovoltaic units and lines in the photovoltaic system.
  • the device is connected to four photovoltaic units through the interface, wherein one photovoltaic unit is connected in series with at least one of the protection switches and then connected to the DC bus in parallel, and Three photovoltaic units are directly connected in parallel to the DC bus.
  • the photovoltaic unit or circuit can withstand the output current of the two photovoltaic units, and the controller can control the protection switch to turn off when a short-circuit fault occurs, thereby protecting the photovoltaic unit and circuit in the photovoltaic system.
  • the device is connected to four photovoltaic units through the interface, wherein the three photovoltaic units are connected in parallel and then connected in series with at least one of the protection switches, and then connected in parallel to all the photovoltaic units.
  • the DC bus is directly connected to the DC bus in parallel with another photovoltaic unit.
  • the photovoltaic unit or circuit can withstand the output current of the two photovoltaic units, and the controller can control the protection switch to turn off when a short-circuit fault occurs, thereby protecting the photovoltaic unit and circuit in the photovoltaic system.
  • the protection switch when the photovoltaic unit is connected in series with a protection switch, the protection switch is connected in series with the positive output terminal or the negative output terminal of the photovoltaic unit, and the protection switch is controlled to be turned off, It can control the circuit break of the corresponding photovoltaic unit.
  • the two protection switches are connected in series with the positive output terminal and the negative output of the photovoltaic unit, respectively end.
  • the redundant setting of the protection switch improves the fault tolerance of the system, and can completely cut off the connection between the short-circuited photovoltaic unit and the system, which is convenient for maintenance and overhaul.
  • the positive output terminals of the multiple photovoltaic units are connected in parallel with one protection switch.
  • Switches are connected in series, or the negative output terminals of multiple photovoltaic units are connected in series with another protection switch after being connected in parallel, and the protection switch is controlled to be turned off to control the line where the corresponding photovoltaic unit is located to be disconnected.
  • the controller is configured to control the protection switch to turn off when the reverse current of the branch is greater than the first current value, and specifically includes: the controller is used for when the branch exists When the absolute value of the current of the circuit is greater than the absolute value of the current of the DC bus, it is determined that the reverse current of the existing branch is greater than the first current value, and the protection switch is controlled to be turned off.
  • the device further includes: a first current sensor and a second current sensor; the first current sensor is used to obtain the absolute value of the DC bus current and send it To the controller; the second current sensor is used to obtain the absolute value of the current of the preset branch and send it to the controller.
  • the controller compares the absolute value of the current of the branch with the absolute value of the current of the DC bus to determine whether there is a photovoltaic unit or the line has a short-circuit fault.
  • the device further includes: a power circuit
  • the power circuit is a DC-DC DC-DC conversion circuit or a DC-AC DC-AC conversion circuit.
  • the device further includes: a first voltage sensor and a DC switch; the DC bus is connected to the input terminal of the power circuit through the DC switch; The first voltage sensor is used to obtain the absolute value of the voltage of the DC bus and send it to the controller.
  • the controller is configured to control the protection switch to turn off when the reverse current of the branch is greater than the first current value, which specifically includes: the controller when there is a branch When the current direction of is opposite to the preset current direction, it is determined that the reverse current of the existing branch is greater than the first current value, and the protection switch is controlled to be turned off.
  • the device further includes: a third current sensor and a fourth current sensor; the third current sensor is used to obtain the current detection direction of the first detection point and Sent to the controller, the first detection point is located in any branch; the fourth current sensor is used to obtain the current detection direction of the second detection point and send it to the controller, except where the first detection point is All other branches outside the branch converge at the second detection point.
  • the controller is specifically configured to: when the current detection direction of the first detection point is opposite to the preset current direction of the first detection point, or the second When the current detection direction of the detection point is opposite to the preset current direction of the second detection point, the protection switch is controlled to be turned off.
  • the protection device further includes: a power circuit; the power circuit is a DC-DC DC-DC conversion circuit or a DC-AC DC-AC conversion circuit.
  • the device further includes: a fifth current sensor, a second voltage sensor, and a DC switch; the DC bus is connected to the input of the power circuit through the DC switch The fifth current sensor is used to obtain the absolute value of the DC bus current and send it to the controller; the second voltage sensor is used to obtain the absolute value of the DC bus voltage and send it to the controller.
  • the controller is also used to control the DC switch to turn off when the absolute value of the DC bus current is greater than the second current value and the absolute value of the DC bus voltage is less than the first voltage value , Realize the protection of the circuit.
  • the protection switch is also used to turn off When the protection unit does not trigger the protection action.
  • the protection unit includes at least one of the following: a fuse, an optimizer, and a shutdown box.
  • the at least two protection switches are controlled by the same controller or controlled by multiple controllers .
  • the controller is specifically used when the detected value of the parameter of the branch exceeds the range of the first preset parameter value, or when the detected value of the parameter of the DC bus exceeds the second preset parameter value When the range, it is determined that the photovoltaic power generation system is faulty.
  • the parameter detection value may be at least one of a voltage value, a current value, a power value, or a temperature value.
  • the parameter detection value is abnormal, for example, when the voltage of the branch decreases, the current increases, the power increases, and the temperature increases, it can be determined that the branch has a short-circuit fault.
  • the controller is specifically configured to: when the leakage current detection value of the DC bus is greater than the third current value, or when the leakage current detection value of the existing branch is greater than the fourth current value, It is determined that the photovoltaic power generation system is malfunctioning. When the leakage current detection value is abnormal, it indicates that the photovoltaic power generation system has a leakage current fault.
  • the leakage current fault can be determined as the branch circuit where the leakage current fault occurs, or the leakage current fault can be located on the DC bus.
  • the controller is specifically configured to determine that there is an arc fault in the branch according to the current detection values of all branches, or determine that the DC bus has an arc fault according to the current detection values of the DC bus. When it is determined that the photovoltaic power generation system is faulty.
  • the controller can specifically determine whether there is an arc fault according to the degree of deviation between the current detection value and the preset standard value.
  • the controller is further configured to control the opening or closing of the protection switch according to a control instruction sent by the host computer, thereby realizing active control of the protection switch.
  • At most three photovoltaic units are directly connected in parallel and then connected to one interface, or at most three photovoltaic units are connected in parallel within the device after passing through corresponding interfaces.
  • the protection switch is a rotary DC isolating switch or a DC circuit breaker.
  • the controller is further configured to control the protection switch to close when it is determined that the fault is eliminated or after a preset time has passed.
  • the protection device further includes a DC/DC converter.
  • the DC bus is connected to the input terminal of the DC/DC converter, and the output terminal of the DC/DC converter is the output terminal of the protection device of the photovoltaic power generation system.
  • the DC/DC converter is used to convert the DC power obtained from the DC bus and output it.
  • the protection device of the photovoltaic power generation system is a boost DC combiner box.
  • the protection device further includes a DC/AC converter, the DC bus is connected to the input terminal of the DC/AC converter, and the output terminal of the DC/AC converter is a photovoltaic power generation system
  • the protection device of the photovoltaic power generation system is an inverter.
  • the present application also provides a protection method for a photovoltaic power generation system, which is applied to control a protection device.
  • the device is connected to at least two photovoltaic units through an interface, and the at least two photovoltaic units are coupled with the DC bus inside the device to form at least two Each branch is connected to at least one photovoltaic unit; the protection switch is used to disconnect all or part of the photovoltaic unit from the DC bus, so that at most three photovoltaic units are directly connected in parallel.
  • the method includes:
  • the control protection switch When it is determined that the photovoltaic power generation system is faulty according to the parameter detection value of the branch or the DC bus, the control protection switch is turned off.
  • the parameter detection value is the reverse current value
  • the fault of the photovoltaic power generation system is determined according to the parameter detection value of the branch or DC bus, which specifically includes:
  • the parameter detection value is the reverse current value
  • the fault of the photovoltaic power generation system is determined according to the parameter detection value of the branch or DC bus, which specifically includes:
  • the device further includes a power circuit
  • the DC bus is connected to the input end of the power circuit through a DC switch
  • the method further includes: when the DC bus When the absolute value of the current is greater than the second current value and the absolute value of the DC bus voltage is less than the first voltage value, the DC switch is controlled to be turned off.
  • the short circuit of the positive and negative poles inside the protection device, or the short-circuit current of the downstream busbar can be cut off in time, so as to realize the protection of the device and the downstream circuit.
  • the power circuit is a DC-DC DC-DC conversion circuit or a DC-AC DC-AC conversion circuit.
  • the parameter detection value is at least one of voltage value, current value, power value or temperature value, and the occurrence of photovoltaic power generation system is determined according to the parameter detection value of the branch or DC bus. Failure, specifically including:
  • determining that the photovoltaic power generation system is faulty according to the parameter detection value of the branch or the DC bus which specifically includes:
  • the leakage current detection value of the DC bus is greater than the third current value, or the leakage current detection value of the existing branch is greater than the fourth current value, it is determined that the photovoltaic power generation system is faulty.
  • determining that the photovoltaic power generation system is faulty according to the parameter detection value of the branch or the DC bus which specifically includes:
  • this application also provides a photovoltaic power generation system, which includes at least two photovoltaic units and the protection device described in any one of the above implementations.
  • Each photovoltaic unit includes at least one photovoltaic module. In the case of a single photovoltaic module, the photovoltaic modules can be connected in series or in series.
  • the controller of the protection device of the photovoltaic power generation system can control the protection switch to turn off when it is determined that the photovoltaic power generation system is faulty according to the parameter detection value of the branch or the DC bus, so that at most three photovoltaic units are directly connected in parallel. This further protects the photovoltaic units and circuits in the photovoltaic system, and because only a protective switch is added to the circuit, the resistance is smaller than that of the fuse, so the loss rate of the photovoltaic system is also reduced.
  • the system further includes a protection unit, and the photovoltaic unit and the protection unit are connected in series or parallel to the protection device through the interface.
  • the protection unit may be a combination of one or more of a fuse, an optimizer, and a shutdown box.
  • the protection device When the protection device includes a power circuit, the power circuit may be a DC-DC (DC-DC) conversion circuit, and when the power circuit is a DC-DC conversion circuit, the DC-DC conversion circuit may specifically be a boost circuit , Buck circuit or Buck-Boost circuit, at this time the protection device can also be the DC combiner box of the photovoltaic power generation system.
  • DC-DC DC-DC
  • the protection device can also be the DC combiner box of the photovoltaic power generation system.
  • the power circuit can also be a direct current-alternating current (DC-AC) conversion circuit, that is, an inverter (or inverter circuit), which is used to convert direct current into alternating current for output.
  • DC-AC direct current-alternating current
  • the protection device When the protection device does not include a power circuit, the protection device can be used as an independent device to be connected to the DC combiner box of the photovoltaic power generation system or the input end of the inverter.
  • the protection device of the photovoltaic power generation system provided by the embodiment of the present application can be applied to the photovoltaic power generation system.
  • the protection switch of the device When the protection switch of the device is turned off, at most three photovoltaic units are directly connected in parallel. For example, when two photovoltaic units are directly connected in parallel to the DC bus in the device, if one of the photovoltaic units has a short-circuit fault, only one normal photovoltaic unit will output a short-circuit current to it. The faulty photovoltaic unit is within the tolerance range, thereby protecting the photovoltaic components and lines from damage.
  • the specific connection mode of the photovoltaic unit and the protection switch can be configured according to actual needs.
  • the controller of the protection device can determine that when the photovoltaic power generation system fails according to the parameter detection value of the branch or the DC bus, the control protection switch is turned off, so that at most three photovoltaic units are directly connected in parallel, thereby protecting the photovoltaic system in the photovoltaic system.
  • the Y wire harness originally used for the built-in fuse does not need to be placed under the inverter or DC combiner box of the photovoltaic power generation system, but can be placed on the photovoltaic unit side, thereby reducing the cable cost.
  • Figure 1 is a schematic diagram of a protection device used in the prior art
  • Figure 2 is a second schematic diagram of a protection device used in the prior art
  • Figure 3 is the third schematic diagram of the protection device used in the prior art
  • FIG. 4 is a schematic diagram of a branch provided by an embodiment of the application.
  • FIG. 5 is a schematic diagram of another branch provided by an embodiment of the application.
  • FIG. 6A is a schematic diagram of a protection device provided by an embodiment of the application.
  • FIG. 6B is a schematic diagram of another protection device provided by an embodiment of the application.
  • 6C is a schematic diagram of another protection device provided by an embodiment of the application.
  • FIG. 7 is a schematic diagram of another protection device provided by an embodiment of the application.
  • FIG. 8 is a schematic diagram of another protection device provided by an embodiment of the application.
  • FIG. 9 is a schematic diagram of still another protection device provided by an embodiment of the application.
  • FIG. 10 is a schematic diagram of another protection device provided by an embodiment of the application.
  • FIG. 11 is a schematic diagram of another protection device provided by an embodiment of the application.
  • FIG. 12 is a schematic diagram of still another protection device provided by an embodiment of this application.
  • FIG. 13 is a schematic diagram of another protection device provided by an embodiment of the application.
  • FIG. 14 is a schematic diagram of another protection device provided by an embodiment of the application.
  • 15 is a schematic diagram of still another protection device provided by an embodiment of the application.
  • FIG. 16 is a schematic diagram of another protection device provided by an embodiment of the application.
  • FIG. 17 is a schematic diagram of another protection device provided by an embodiment of the application.
  • FIG. 18 is a schematic diagram of still another protection device provided by an embodiment of the application.
  • FIG. 19 is a schematic diagram of another protection device provided by an embodiment of the application.
  • 20A is a schematic diagram of yet another protection device provided by an embodiment of the application.
  • 20B is a schematic diagram of still another protection device provided by an embodiment of the application.
  • 20C is a schematic diagram of still another protection device provided by an embodiment of the application.
  • FIG. 21 is a schematic diagram of another protection device provided by an embodiment of the application.
  • FIG. 22 is a flowchart of a short-circuit protection method provided by an embodiment of the application.
  • FIG. 23 is a flowchart of another short-circuit protection method provided by an embodiment of the application.
  • FIG. 24 is a schematic diagram of a photovoltaic power generation system provided by an embodiment of the application.
  • each MPPT device is connected to at least two photovoltaic units or more, and in order to protect the photovoltaic unit and the line when the photovoltaic unit is short-circuited or the line is short-circuited, the positive output terminal of the photovoltaic unit And/or the negative output terminal is connected in series with a fuse (or fuse).
  • a fuse or fuse
  • Figure 1 is a schematic diagram when the positive output terminal and negative output terminal of the photovoltaic unit are both connected in series with fuses;
  • Figure 2 is a schematic diagram when the positive output terminal of the photovoltaic unit is connected in series with a fuse;
  • Figure 3 is the negative output terminal of the photovoltaic unit is blown in series Schematic diagram of the device.
  • Each branch includes a photovoltaic module 101, the three branches are connected in parallel before the switch 102, and then the MPPT device 103 is connected through the DC switch 102.
  • the fuse1-fuse6 in Fig. 1, the fuse1-fuse3 in Fig. 2, and the fuse1-fuse3 in Fig. 3 are fuses, which fuse when the current in the circuit is too large to protect the photovoltaic module and the circuit.
  • the present application provides a protection device, a short circuit protection method and a photovoltaic power generation system, which can effectively protect the photovoltaic unit and the line when the photovoltaic unit is short-circuited or the line is short-circuited, and the power loss is low.
  • first and second in the following description are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined with “first”, “second”, etc. may explicitly or implicitly include one or more of these features.
  • connection should be understood in a broad sense.
  • “connected” can be a fixed connection, a detachable connection, or a whole; it can be a direct connection, or It can be connected indirectly through an intermediary.
  • a single photovoltaic unit may include one photovoltaic module, or may be formed by multiple photovoltaic modules in series and parallel. For example, multiple photovoltaic modules are connected in series to form a photovoltaic string, and multiple photovoltaic strings are connected in parallel to form photovoltaics. unit.
  • the embodiments of the present application do not specifically limit the specific number of photovoltaic modules included in the photovoltaic unit, and those skilled in the art can set it according to actual needs, and the electrical parameters of a single photovoltaic module are not specifically limited in the embodiments of the present application.
  • the output voltages of multiple photovoltaic units connected to the same device may be the same or different, and the embodiment of the present application does not specifically limit it.
  • the protection device provided by the embodiments of the application is applied to a photovoltaic power generation system, and can be connected to at least two photovoltaic units through the interface.
  • the DC bus can be directly connected in parallel within the device or in series with the protection switch Then connect the DC bus in parallel to converge the output current of the photovoltaic unit on the DC bus, and then at least two branches are formed inside the device, and each branch is connected to at least one photovoltaic unit.
  • FIG. 4 is a schematic diagram of a branch provided by an embodiment of the application.
  • the branch includes a photovoltaic unit 101a1, the positive output terminal of the photovoltaic unit 101a1 is the positive output terminal of the branch, and the negative output terminal of the photovoltaic unit 101a1 is the negative output terminal of the branch. Distinguish again.
  • FIG. 5 is a schematic diagram of another branch provided in an embodiment of the application.
  • the branch may include multiple branches as shown in FIG. 4, and therefore includes at least two photovoltaic units, for example, 101a1, 101a2, ... 101ai in sequence.
  • a protection switch (not shown in the figure) may be included in the branch to protect the photovoltaic units and lines.
  • the branch in the embodiment of the present application is a concept in the field of electricity, and refers to the route through which the branch currents of the parallel circuit flow.
  • the line where the photovoltaic unit 101a1 is located can be called a branch
  • the line formed after the photovoltaic unit 101a1 and the photovoltaic unit 101a1 are connected in parallel may also be referred to as a branch.
  • the positive output terminals of each photovoltaic unit are combined to become the positive output terminal of the branch, and the negative output terminals of each photovoltaic unit are combined to become the negative output terminal of the branch.
  • the "branch” in the following embodiments specifically refers to all the branches shown in FIG. 4 and the general term for the branches shown in FIG. 5. That is, the general term for all the other branches except the main circuit (DC bus).
  • FIG. 6 is a schematic diagram of a protection device provided by an embodiment of the application.
  • the protection device 200 includes an interface, protection switches S 1 -S M-1 , a DC bus and a controller (not shown in the figure).
  • the device 200 can be connected to at least two photovoltaic units through an interface, and the number of connected photovoltaic units is not specifically limited in this application. At least two photovoltaic units are coupled with the DC bus inside the device to form at least two branches, and at least one photovoltaic unit is connected to each branch.
  • the DC bus specifically includes a positive DC bus and a negative DC bus.
  • the protection switches S 1 -S M-1 are used to disconnect all or part of the photovoltaic units from the DC bus, so that at most three photovoltaic units are directly connected in parallel, that is, used to make at most three photovoltaic units in the The DC bus is directly connected in parallel inside the device.
  • the protective switch S 1 -S M-1 will enable at most 2 photovoltaic units when it is off.
  • the value of i and j in the figure is 2 at this time.
  • the protection switches S 1 -S M-1 will enable at most 3 photovoltaic units when they are disconnected. Units are directly connected in parallel inside the device, and the value of i and j in the figure is 3 at this time.
  • i and j are determined by the current withstand value of the actual photovoltaic unit, which is not specifically limited in the embodiment of the present application. It should be noted that the figure shown in Fig. 6 is only for the convenience of drawing and description, and the i photovoltaic units in the figure are actually connected in parallel inside the protection device.
  • the controller is used to control the protection switch to turn off when it is determined that the photovoltaic power generation system is faulty according to the parameter detection value of the branch or the DC bus.
  • the following takes the occurrence of a short-circuit fault as an example for description.
  • the controller is specifically used to determine that the photovoltaic power generation system has a fault when the reverse current value of the branch is greater than the first current value. .
  • the current of all branches merges into the DC bus, so the absolute value of the current of the DC bus is greater than the absolute value of the current of any branch, and the direction of the current is from the positive pole of the photovoltaic unit to the positive DC bus.
  • the output current of all other normal branches will flow to the branch where the short-circuit fault occurs.
  • the voltage of the DC bus is reduced, and the current direction of the existing branch changes to the current direction.
  • the branch of the short-circuit fault that is, the reverse current of the existing branch is greater than the first current value.
  • the first current value can be determined according to the actual situation, and the embodiment of the present application does not specifically limit it.
  • the first current value can be a relatively small value, for example, 0, that is, when there is a reverse current in the branch, the controller controls the protection switch to turn off.
  • the controller determines that there is a photovoltaic unit or a short circuit fault occurs in the line, and controls the protection switch to open to realize the protection of the photovoltaic unit and the line.
  • the protection device 200 further includes a power circuit 201 for performing power conversion, and the power circuit may be a direct current/direct current (DC/DC) conversion circuit or a direct current-alternating current (DC/AC) conversion circuit .
  • DC/DC direct current/direct current
  • DC/AC direct current-alternating current
  • the DC-DC conversion circuit may specifically be a boost (Boost) circuit, a buck (Buck) circuit or a buck-boost (Buck-Boost) circuit, and the protection device It can be used as a DC combiner box of a photovoltaic power generation system, which is not specifically limited in this application.
  • Boost boost
  • Buck buck
  • Buck-Boost buck-boost
  • the power circuit 201 is a DC-AC circuit
  • the DC-AC circuit is used to convert DC power into AC power for output.
  • the protection device can be used as an inverter of the photovoltaic power generation system.
  • the protection device can also be provided as an independent device at the DC combiner box of the photovoltaic power generation system or the input end of the inverter.
  • the protection device provided by the embodiments of the present application can be connected to multiple photovoltaic units through the interface.
  • the protection switch of the device When the protection switch of the device is turned off, at most three photovoltaic units are directly connected in parallel inside the device to protect the photovoltaic modules. And the circuit will not be damaged, and the connection mode of the specific photovoltaic unit and the protection switch can be configured according to actual needs.
  • the controller of the device can control the protection switch to turn off when the reverse current of the branch circuit is greater than the first current value, thereby protecting the photovoltaic unit and the line in the photovoltaic system, and because only the protection switch is added to the circuit, the phase Compared with the fuse, the resistance is smaller, so it also reduces the loss rate of the photovoltaic system.
  • the Y wire harness originally used for the built-in fuse does not need to be placed under the inverter or DC combiner box of the photovoltaic power generation system, but can be placed on the photovoltaic unit side, thereby reducing the cable cost.
  • the faulty photovoltaic module is allowed to withstand the back-sink current from other photovoltaic modules as an example.
  • the protection switch is used to disconnect all photovoltaic units from the DC bus. Refer to Figure 6B for details. Shown.
  • FIG. 6B is a schematic diagram of another protection device provided by an embodiment of the application.
  • At most three photovoltaic units are directly connected in parallel and then connected to one interface as an example. In other embodiments, at most three photovoltaic units are connected in parallel inside the device after passing through corresponding interfaces.
  • the specific implementation manner can also be seen in FIG. 6C.
  • the controller determines that when the absolute value of the current of the existing branch is greater than the absolute value of the current of the DC bus, or when the reverse current of the existing branch is greater than the first current value, the controller determines that there is a reverse of the branch. When the direction current is greater than the first current value, the protection switch is controlled to be turned off.
  • the working principle of the controller will be described below in conjunction with a specific implementation manner.
  • FIG. 7 is a schematic diagram of another protection device provided by an embodiment of the application.
  • the protection device 200 is connected to two photovoltaic units 101a1 and 101a2 through an interface.
  • the two photovoltaic units are connected in parallel in the protection device 200, they are connected to the power circuit 201 through the DC switch 102.
  • the DC switch 102 is used for the protection circuit.
  • the setting may be canceled and short-circuited.
  • At least one photovoltaic unit is also connected in series with a protection switch S1.
  • the current of the two photovoltaic units merges into the DC bus, and the absolute value of the current of the DC bus (the absolute value of the detection current of detection point A or detection point B) is greater than the absolute value of the current of any branch (detection point) C or the absolute value of the detection current at the detection point D).
  • the controller controls the protection switch S1 to turn off.
  • the protection switch S1 when a short-circuit fault occurs in the branch where the photovoltaic unit 101a1 is located, the protection switch S1 is opened so that the photovoltaic unit 101a2 stops outputting current, thereby protecting the photovoltaic unit and the line; when a short-circuit fault occurs in the branch where the photovoltaic unit 101a2 is located, the protection switch The opening of S1 opens the short-circuited branch, and the photovoltaic unit 101a1 can continue to output current to the device 200 and maintain a normal working state.
  • a current sensor can be used to detect the magnitude and direction of the current, and the current sensor sends the detection result to the controller of the device 200.
  • the foregoing implementation manner may be implemented by detecting the absolute value of the current at point A or B by the first current sensor, and detecting the absolute value of the current at point C or D by the second current sensor.
  • the protection switch S1 can be connected in series with the positive output terminal of the photovoltaic unit 102a2, or can be connected in series with the negative output terminal of the photovoltaic unit 102a2, and can also be connected in series with the positive output terminal and the negative output terminal of the photovoltaic unit 102a2.
  • the unit implements redundant control, which is not specifically limited in the embodiment of the present application.
  • the current direction of the detection point C and the detection point D can be set to a preset direction, for example, can be set to a positive direction.
  • the output current of the photovoltaic unit 101a2 flows into the branch where the photovoltaic unit 101a1 is located, causing the current direction at the detection point C to be opposite to the preset current direction, which is a negative direction.
  • the controller The opening of the control protection switch S1 causes the photovoltaic unit 101a2 to stop outputting current, thereby protecting the photovoltaic unit and the line; and when the branch where the photovoltaic unit 101a2 is located has a short-circuit fault, the output current of the photovoltaic unit 101a1 flows into the branch where the photovoltaic unit 101a2 is located.
  • the current direction at the detection point D is opposite to the preset current direction.
  • the controller controls the protection switch S1 to open so that the short-circuited branch is opened, and the photovoltaic unit 101a1 can continue to output current to the protection device 200 normally.
  • This method can be implemented by detecting the current direction at point C by the third current sensor, and detecting the current direction at point D by the fourth current sensor.
  • the detection point C and the detection point D in the above embodiments can also be located on the negative output side of the corresponding photovoltaic unit, or one is located on the positive output side of the photovoltaic unit, and the other is located on the negative output side of the photovoltaic unit.
  • the control The working principle of the device is similar, so I won’t repeat it here.
  • the protection device when the protection device is connected to two photovoltaic units through the interface, its controller can be able to exist when the absolute value of the branch current is greater than the absolute value of the DC bus current, or there is a branch current direction and a preset current direction
  • the protection switch is controlled to open so that the current of any branch is less than the first current value, thereby protecting the photovoltaic unit and the circuit, and because only the protection switch is added in the circuit, the resistance is smaller than that of the fuse (in some In the embodiment, the internal resistance of the applied protection switch is only about 0.3 milliohm, which is smaller than the internal resistance of the fuse), so the loss rate loss is also reduced.
  • the Y terminal can also be arranged on the side of the photovoltaic unit, thereby reducing the cost of the cable.
  • the above embodiment takes the protection device connected to two photovoltaic units as an example, but in order to improve the DC ratio of the photovoltaic power generation system, usually the protection device will be connected to 3, 4... or even more photovoltaic units.
  • the protection device will be connected to 3, 4... or even more photovoltaic units.
  • FIG. 8 is a schematic diagram of another protection device provided by an embodiment of the application.
  • the positive output terminals of the three photovoltaic units are connected in parallel inside the protection device to the power circuit 201 through the DC switch 102.
  • the DC switch 102 is used for the protection circuit. In practical applications, the setting can also be cancelled and short-circuited.
  • the photovoltaic unit 101a1 is connected in series with the protection switch S1 and then connected to the DC bus in parallel, and the photovoltaic unit 101a3 is connected in series with the protection switch S2 and then connected to the DC bus in parallel.
  • the output currents of the three photovoltaic units merge into the DC bus, so the absolute value of the DC bus current (the absolute value of the detection current at detection point A or detection point B) is greater than the absolute value of the current of any branch ( The absolute value of the detection current at detection point C, detection point D, and detection point E).
  • the output current of other normal photovoltaic units will flow to the photovoltaic unit that has the short-circuit fault.
  • the absolute value of the current of the DC bus is less than the absolute value of the current of any branch.
  • the controller of the protection device controls the protection switches S1 and S2 to open so that the current flowing into the short-circuit branch is zero, thereby protecting the photovoltaic unit and the line .
  • This implementation can be achieved by the first current sensor detecting the absolute value of the current of the DC bus (ie, the detection point A or B), and the second current sensor detecting the absolute value of the current of any branch (ie, the detection point C, D, or E).
  • the current direction of point C, point D, and point E can be set to the preset current direction, for example, set to the positive direction.
  • control The device controls the protection switches S1 and S2 to open so that the current flowing into the short-circuit branch is zero, thereby protecting the photovoltaic unit and the line.
  • This method can be realized by three current sensors respectively detecting the current directions of the three first-type photovoltaic unit branches.
  • the controller can control the protection switch to turn off to protect the photovoltaic unit and the line when the current detection direction at point H and point G is opposite to the preset current direction.
  • This method can be implemented by detecting the current direction of point G by the third current sensor, and detecting the current direction of point H by the fourth current sensor, which can reduce the number of current sensors used compared with the previous implementation.
  • the protection switch S1 or the protection switch S2 may also be canceled and short-circuited. At this time, the controller controls the protection switch to be turned off so that the current flowing into the short-circuit faulted branch can be less than the first current value.
  • the controller can be able to when the absolute value of the current of the photovoltaic unit is greater than the absolute value of the DC bus current, or the current direction of the branch and the preset current
  • the protection switch is controlled to turn off so that the current of any branch is less than the first current value, thereby protecting the photovoltaic unit and the circuit, and because only the protection switch is added to the circuit, the resistance is smaller than that of the fuse. Also reduces the loss rate loss.
  • the Y terminal can also be arranged on the side of the photovoltaic unit, thereby reducing the cost of the cable.
  • FIG. 9 is a schematic diagram of still another protection device provided by an embodiment of the application.
  • the photovoltaic units 101a1 and 101a2 are directly connected in parallel inside the protection device and then connected to the DC bus, and the photovoltaic unit 101a3 is connected in parallel to the DC bus of the device after being connected in series with the protection switch S1.
  • the DC switch 102 is used to protect the circuit, and in some embodiments, the setting can also be cancelled and short-circuited.
  • the protection switch S1 is connected in series with the negative electrode of the photovoltaic unit 101a3 as an example. In some embodiments, the protection switch S1 may also be connected in series with the anode of the photovoltaic unit 101a3.
  • the current of each branch flows into the DC bus, so the absolute value of the current of the DC bus (the absolute value of the detection current at detection point A or detection point B) is greater than the absolute value of the current of any branch (detection point The absolute value of the detection current of C, D, E and F).
  • the controller of the protection device controls the protection switch S1 to turn off when the absolute value of the current of the existing branch is greater than the absolute value of the current of the DC bus.
  • the opening of the protection switch S1 can make the current flowing into the faulty branch zero, and enable the photovoltaic units 101a1 and 101a2 to also output current normally; when the photovoltaic units 101a1 and 101a2
  • the opening of the protection switch S1 can stop the branch where the photovoltaic unit 101a3 is located from outputting current to the faulty branch, thereby protecting the photovoltaic unit and the line.
  • This implementation mode can detect the absolute value of the current of the DC bus (detection point A or detection point B) through the first current sensor, and the second current sensor detects any branch (any one of detection points C, D, E, or F)
  • the absolute value of the current is achieved, that is, two current sensors are required.
  • the current direction of the detection points E and F can be set to a preset direction, for example, set to a positive direction.
  • the current direction at detection point E When a short-circuit fault occurs in the branch where photovoltaic unit 101a3 is located, the current direction at detection point E will be opposite to the preset current direction; when a short-circuit fault occurs in the branch where photovoltaic units 101a1 and 101a2 are located, the current direction at detection point F will be the same as the preset current direction. Suppose the current direction is opposite.
  • this implementation can be realized by detecting the current direction of point E and point F respectively by two current sensors.
  • the controller controls the protection switch S1 to turn off to protect Photovoltaic units and lines.
  • FIG. 10 is a schematic diagram of another protection device provided by an embodiment of the application.
  • protection switch S1 is connected in series with the negative output terminals of the photovoltaic units 101a1 and 101a2 (it can also be connected in series with the positive output terminals of the photovoltaic units 101a1 and 101a2).
  • the working principle of the controller is similar to the above description, and will not be repeated here in the embodiment of the present application.
  • the detection points C, D, and E described in the above embodiments can also be located on the negative output side of the corresponding photovoltaic unit.
  • the protection device when the protection device is connected to three photovoltaic units through the interface, its controller can be used when the absolute value of the current of any branch is greater than the absolute value of the current of the DC bus, or the current direction of any branch exists
  • the protection switch is controlled to open to protect the photovoltaic unit and the circuit, and because the protection switch is only added to the circuit, the resistance is smaller than that of the fuse, so the loss rate is reduced.
  • the Y terminal can also be arranged on the side of the photovoltaic unit, thereby reducing the cost of the cable.
  • the input terminal of each device includes three photovoltaic units as an example.
  • the following describes the working principle when each device is connected to four photovoltaic units.
  • FIG. 11 is a schematic diagram of another protection device provided by an embodiment of the application.
  • the positive output terminals of the 4 photovoltaic units are collected in the protection switch S1 of the positive DC bus inside the protection device, and the negative output terminals of each first-type photovoltaic unit branch are connected in series with a protection switch inside the protection device. On the negative DC bus.
  • the current of the four photovoltaic units merges into the DC bus, so the absolute value of the current of the DC bus (the absolute value of the detection current at detection point A or B) is greater than the absolute value of the current of any branch (detection point C) The absolute value of the detection current of, D, E and F).
  • the first current sensor can detect the absolute value of the current at points A and B of the DC bus
  • the second current sensor can detect any branch of the first type of photovoltaic unit (detection point C, D, E or F at any point ) The absolute value of the current is realized.
  • the current direction of point C, D, E, and F can be set to the preset direction, for example, set to the positive direction.
  • the controller The protection switch is controlled to open so that the current flowing into the faulty branch is zero, thereby protecting the photovoltaic unit and the line.
  • This implementation can be implemented by four current sensors respectively detecting the current directions of the four first-type photovoltaic unit branches.
  • the current direction of point G and H can be set to the preset direction, for example, set to the positive direction
  • the current detection direction at point H When there is a short circuit fault in the branch where the photovoltaic units 101a1, 101a3 and 101a4 are located, the current detection direction at point H will be opposite to the preset current direction.
  • the current detection direction at point G Will be opposite to the preset direction.
  • This method can be realized by detecting the current direction of point G and point H by two current sensors.
  • the protection switches S1, S2, and S3 can also be canceled and short-circuited.
  • the controller controls the protection switch to turn off so that the current flowing into the short-circuit branch is less than the first current value to protect the photovoltaic unit and line.
  • FIG. 12 is a schematic diagram of still another protection device provided by an embodiment of the application.
  • Figure 12 is another possible implementation.
  • the difference from the one shown in Figure 11 is that the positive output terminal of the photovoltaic unit 101a1 and the positive output terminal of the photovoltaic unit 101a2 are collected in the protection switch S1, and connected to the positive DC through the protection switch S1. Bus; the positive output terminal of the photovoltaic unit 101a3 and the positive output terminal of the photovoltaic unit 101a4 are collected in the protection switch S6, and the positive DC bus is connected through the protection switch S6.
  • the controller may adopt the working principle corresponding to FIG. 11, which is not repeated here in the embodiment of the present application.
  • FIG. 13 is a schematic diagram of another protection device provided by an embodiment of the application.
  • Figure 13 is another possible implementation. The difference from the one shown in Figure 11 is that the positive output terminal of each photovoltaic unit is connected in series with a protection switch and then collected on the positive DC bus, and the negative output terminal of each photovoltaic unit is connected in series. After the protection switch, it is collected on the negative DC bus. Redundant protection switches can further improve safety and ensure that the branch where the photovoltaic unit is located can be disconnected.
  • the controller may adopt the working principle corresponding to FIG. 11, which is not repeated here in the embodiment of the present application.
  • detection points C, D, E, and F described in the above embodiments may also be located on the negative output end side of the corresponding photovoltaic unit.
  • the protection device when the protection device is connected to 4 photovoltaic units through the interface, its controller can be used when the absolute value of the branch current is greater than the absolute value of the DC bus current, or the current direction of the photovoltaic unit is different from the preset value.
  • the protection switch When the current direction is reversed, the protection switch is controlled to open so that the current of any branch is less than the first current value, thereby protecting the photovoltaic unit and the circuit, and because only the protection switch is added to the circuit, the resistance is smaller than that of the fuse. Therefore, the loss rate loss is also reduced.
  • the Y terminal can also be arranged on the side of the photovoltaic unit, thereby reducing the cost of the cable.
  • FIG. 14 is a schematic diagram of another protection device provided by an embodiment of the application.
  • the photovoltaic units 101a1 and 101a2 are connected in parallel to the DC bus of the device, and the branches where the photovoltaic units 101a3 and 101a4 are connected in series with a protection switch are connected to the DC bus of the device.
  • the positive output ends of the two first-type photovoltaic unit branches are connected to the positive DC bus after being collected, and the negative output ends of the two first-type photovoltaic unit branches are respectively connected in series with a protection switch and then collectively connected to the negative DC bus.
  • the positive output terminals of the photovoltaic units 101a1 and 101a2 are connected to the positive DC bus through the protection switch S1, and the negative output terminals of the photovoltaic units 101a1 and 101a2 are connected to the negative DC bus through the protection switch S2.
  • the protection switches S1 and S2 can also be cancelled and short-circuited.
  • the current of each branch flows into the DC bus, so the absolute value of the current of the DC bus (the absolute value of the detection current of detection point A or B) is greater than the absolute value of the current of any branch (detection point C, The absolute value of the detection current of D, E, F, G and H).
  • the controller of the device controls the protection switches S1-S4 to open, so that the current flowing into the faulty branch is zero, thereby protecting the photovoltaic unit and the line .
  • This implementation can be achieved by the first current sensor detecting the absolute value of the current at point A or B of the DC bus, and the second current sensor detecting the absolute value of the current at any one of C, D, E, F, G, or H.
  • the current direction of the detection point G and the detection point H can be set to a preset direction, for example, set to a positive direction.
  • the current direction at point H When a short-circuit fault occurs in the branch where photovoltaic units 101a3 and 101a4 are located, the current direction at point H will be opposite to the preset direction; when there is a short-circuit fault in the branch where photovoltaic units 101a1 and 101a2 are located, the current direction at point G will be the same as the preset Set the direction to be opposite, so the controller can determine that there is a short-circuit fault and control the protection switches S1-S4 to open when the current detection direction at any point of H point and G point is opposite to the preset current direction, so that the The current is zero, thereby protecting the photovoltaic unit and the circuit.
  • This implementation can be implemented by detecting the current direction of point G and point H by two current sensors.
  • the switches S1, S3, and S4 can also be canceled and short-circuited.
  • the controller controls the protection switch to turn off so that the current flowing into the short-circuit branch is less than the first current value, thereby protecting the photovoltaic unit and the line.
  • FIG. 15 is a schematic diagram of still another protection device provided by an embodiment of the application.
  • the difference between the implementation shown in Fig. 15 and Fig. 14 is that the positive output terminals of the photovoltaic units 101a3 and 101a4 are collected and connected to the positive DC bus through the protection switch S3, and the negative output terminal of the photovoltaic unit 101a3 is connected to the negative DC bus through the protection switch S4. The negative output terminal of the photovoltaic unit 101a4 is connected to the negative DC bus through the protection switch S5.
  • the controller can use the working principle corresponding to FIG. 14 to realize the protection of the photovoltaic unit and the circuit, which will not be repeated in the embodiment of the present application.
  • FIG. 16 is a schematic diagram of another protection device provided by an embodiment of the application.
  • the difference between the implementation shown in Fig. 16 and Fig. 14 is that the photovoltaic units 101a1 and 101a2 are connected in parallel, and the positive output terminals of the photovoltaic units 101a1 and 101a2 are collected and connected to the positive DC bus through the protection switch S1, and the negative output terminals are collected and protected.
  • the switch S4 is connected to the negative DC bus; the positive output terminal of the photovoltaic unit 101a3 is connected to the positive DC bus, the negative output terminal is connected to the negative DC bus through the protection switch S2; the positive output terminal of the photovoltaic unit 101a4 is connected to the positive DC bus through the protection switch S3, and the negative output terminal Connect the negative DC bus through the protection switch S4.
  • the controller can use the working principle corresponding to FIG. 14 to realize the protection of the photovoltaic unit and the circuit, which will not be repeated in the embodiment of the present application.
  • the detection points C, D, E, and F described in the above embodiments can also be located on the negative output side of the corresponding photovoltaic unit.
  • the protection device when the protection device is connected to 4 photovoltaic units through the interface, its controller can be used when the absolute value of the current of any branch is greater than the absolute value of the DC bus current, or the current direction of any branch and the preset When the current direction is reversed, the protection switch is controlled to open so that the current of any branch is less than the first current value, thereby protecting the photovoltaic unit and the circuit, and because only the protection switch is added to the circuit, the resistance is smaller than that of the fuse , So it also reduces the loss rate loss.
  • the Y terminal can also be arranged on the side of the photovoltaic unit, thereby reducing the cost of the cable.
  • FIG. 17 is a schematic diagram of another protection device provided by an embodiment of the application.
  • the photovoltaic units 101a1 and 101a2 are directly connected in parallel inside the device, the positive output ends of the photovoltaic units 101a1 and 101a2 are connected to the positive DC bus through the protection switch S1, and the negative output ends are connected to the negative DC bus through the protection switch S2.
  • the photovoltaic units 101a3 and 101a4 are directly connected in parallel inside the device, the positive output terminals of the photovoltaic units 101a3 and 101a4 are connected to the positive DC bus through the protection switch S3, and the negative output terminals are connected to the negative DC bus through the protection switch S4.
  • the current of each branch flows into the DC bus, so the absolute value of the current of the DC bus (the absolute value of the detection current of detection point A or B) is greater than the absolute value of the current of any branch (detection point C, The absolute value of the detection current of D, E, F, G and H).
  • This implementation can be achieved by one current sensor detecting the absolute value of the current at point A or B of the DC bus, and another current sensor detecting the absolute value of the current at any one of C, D, E, F, G, or H.
  • the current direction of point G and H can be set to the preset direction, for example, set to the positive direction.
  • the current direction at point G When a short-circuit fault occurs in the branch where photovoltaic units 101a1 and 101a2 are located, the current direction at point G will be opposite to the preset current direction; when there is a short-circuit fault in the branch where photovoltaic units 101a3 and 101a4 are located, the current direction at point H will be the same as The preset current direction is opposite, so the controller can determine that there is a short-circuit fault and control the protection switches S1-S4 to open when the current detection direction at any point of point G and H is opposite to the preset current direction, so that the flow into the fault branch The current of the circuit is zero, thereby protecting the photovoltaic unit and the circuit.
  • At least one of the protection switches S1 and S2 can be cancelled and short-circuited, or at least one of the protection switches S3 and S4 can be cancelled and short-circuited, or any of the protection switches S1 and S2 can be short-circuited.
  • One and any one of the protection switches S3 and S4 are cancelled and short-circuited, thereby reducing the number of protection switches connected in series to reduce costs.
  • the controller controls the remaining protection switch to be turned off, the current flowing into the branch with the short-circuit fault can be less than the first current value, thereby protecting the photovoltaic unit and the line.
  • the protection device is connected to 4 photovoltaic units through the interface, and its controller can when the absolute value of the current of the branch is greater than the absolute value of the current of the DC bus, or the current direction of the branch and the preset current When the direction is reversed, the protection switch is controlled to turn off so that the current of any branch is less than the first current value, thereby protecting the photovoltaic unit and the circuit, and because only the protection switch is added to the circuit, the resistance is smaller than that of the fuse. Also reduces the loss rate loss.
  • the Y terminal can also be arranged on the side of the photovoltaic unit, thereby reducing the cost of the cable.
  • each device can also be connected to more photovoltaic units.
  • the following describes the connection of each device in detail The working principle of the controller when the number of photovoltaic units is greater than 4 circuits.
  • M is an integer greater than or equal to 3
  • at most j photovoltaic units are directly connected to the DC bus inside the device, and each of the remaining photovoltaic units is connected to the DC bus in parallel after at least one protection switch is connected in series.
  • the protection switch when the photovoltaic unit is connected in series with a protection switch, the protection switch is connected in series with the positive output terminal or the negative output terminal of the photovoltaic unit; when the photovoltaic unit is connected in series with two protection switches, the protection switch is connected in series with the positive output terminal and the negative output terminal of the photovoltaic unit. Output terminal to achieve redundant protection.
  • the value of j is 0, 1 or 2; when the faulty photovoltaic unit can withstand two other normal photovoltaics For the output current of the unit, the value of j is 0, 1, 2 or 3.
  • FIG. 18 is a schematic diagram of still another protection device provided by an embodiment of the application.
  • the current of all photovoltaic units merges into the DC bus, and the absolute value of the current of the DC bus (the absolute value of the detection current at the detection point A or the detection point B) is greater than the absolute value of the current of any branch.
  • the output current of other normal photovoltaic units will flow to the branch where the short-circuited photovoltaic unit is located.
  • the absolute value of the current of the DC bus is less than the absolute value of the current of any branch where the photovoltaic unit is located. value.
  • the controller of the device 200 controls the protection switches S 1 -S M-2 to turn off, so that the current of any branch is less than the first preset Electric current to protect photovoltaic units and lines.
  • the above implementation can be achieved by detecting the absolute value of the current at point A or B by the first current sensor, and detecting the absolute value of the current of any branch by the second current sensor.
  • the current direction of the detection point G and the detection point H can be set to a preset direction, for example, it can be set to a positive direction.
  • point G can be located at the positive or negative output end of any branch, and the positive output ends of all branches except the branch where point G is located are gathered at point H, or except for the branch where point G is located The negative output terminals of all the other branches of the group are gathered at point H.
  • the current of all other branches flows into the branch where point G is located, causing the current detection direction at point G to be opposite to the preset direction at this time; when the branch where point G is located is normal, and the other branches are normal.
  • the branch where point G is located When there is a short-circuit fault in the circuit, the branch where point G is located outputs current to the branch where the short-circuit fault occurs. At this time, the current detection direction at point H is opposite to the preset current direction.
  • the controller determines that there is a short-circuit fault, and the controller controls the protection switches S1-S M-2 to open so that the current of any branch is less than The first current value, in turn, protects the photovoltaic unit and the line.
  • This method can be implemented by detecting the current direction at point G by the third current sensor, and detecting the current direction at point H by the fourth current sensor.
  • the protection switches S 1 -S M-2 can also be connected to the negative output terminal of the corresponding photovoltaic unit, or a protection switch is connected in series to both the positive and negative output terminals of the photovoltaic unit.
  • the fault tolerance can be improved by redundantly setting the protection switch.
  • At least one protection switch may be connected in series in all the branches of the first-type photovoltaic unit. At this time, the controller controls the protection switch to turn off so that the current of any branch is zero.
  • the protection device when the protection device is connected to at least three branches of photovoltaic units through the interface, its controller can be able to exist when the absolute value of any branch current is greater than the absolute value of the DC bus current, or there is a branch current direction
  • the protection switch is controlled to open so that the current of any branch is less than the first current value, thereby protecting the photovoltaic unit and the line, and because only the protection switch is added to the circuit, it is compared with the fuse The resistance is small, so the loss rate loss is also reduced.
  • the Y terminal can also be arranged on the side of the photovoltaic unit, thereby reducing the cost of the cable.
  • FIG. 19 is a schematic diagram of another protection device provided by an embodiment of the application.
  • each i photovoltaic unit is directly connected in parallel inside the device and then connected to the DC bus of the device after at least one protection switch is connected in series, and N is an integer greater than or equal to 2.
  • the currents of all branches merge into the DC bus, and the absolute value of the current of the DC bus (the absolute value of the detection current at the detection point A or the detection point B) is greater than the absolute value of the current of any branch.
  • control protection switch S 1 -S N disconnected, so that any current less than the first preset current branch, To protect photovoltaic units and lines.
  • the above implementation can be achieved by detecting the absolute value of the current at point A or B by the first current sensor, and detecting the absolute value of the current of any branch by the second current sensor.
  • the current direction of the detection point G and the detection point H can be set to a preset direction, for example, it can be set to a positive direction.
  • point G can be located at the positive or negative output end of any branch, and the positive output ends of all branches except the branch where point G is located are gathered at point H, or except for the branch where point G is located The negative output terminals of all the other branches of the group are gathered at point H.
  • This method can be implemented by detecting the current direction at point G by the third current sensor, and detecting the current direction at point H by the fourth current sensor.
  • S 1 -S N protection switch may also be connected to the negative output terminal of the corresponding branch, or the positive and negative output terminal of the corresponding branch are connected in series with a circuit breaker, the protection provided by the redundancy The switch can improve fault tolerance.
  • the protection device when the protection device is connected to at least two photovoltaic units through the interface, its controller can be able to exist when the absolute value of any branch current is greater than the absolute value of the DC bus current, or there is a branch current direction and pre-set value.
  • the protection switch When the current direction is reversed, the protection switch is controlled to open so that the current of any branch is less than the first current value, thereby protecting the photovoltaic unit and the circuit, and because only the protection switch is added to the circuit, the resistance is smaller than that of the fuse , So it also reduces the loss rate loss.
  • the Y terminal can also be arranged on the side of the photovoltaic unit, thereby reducing the cost of the cable.
  • FIG. 20A is a schematic diagram of another protection device provided by an embodiment of the application.
  • At most j photovoltaic units are directly connected to the DC bus inside the device, and (M-j) photovoltaic units are connected to the DC bus after being connected in series with at least one switch in the device. At most i photovoltaic units are directly connected in parallel inside the device and then connected in series with at least one protection switch, and then connected to the DC bus of the device.
  • N is an integer greater than or equal to 2.
  • the value of i is 2, and the value of j can be 0, 1, or 2.
  • the value of i can be 2 or 3
  • the value of j can be 0, 1, 2 or 3.
  • the number of protection switches is required It is (M+N-2).
  • the current of all branches merges into the DC bus, so the absolute value of the current of the DC bus (the absolute value of the detected current at point A or B) is greater than the absolute value of the current of any branch.
  • the output current of all other normal branches will flow to the branch where the short-circuit fault occurs. At this time, no current flows through the DC bus, that is, the absolute value of the current of the DC bus is less than that of any branch. The absolute value of the current in the circuit.
  • the above implementation can be realized by two current sensors.
  • One current sensor detects the absolute value of the current at point A or B of the DC bus, and the other current sensor detects the current in any branch. The absolute value of.
  • the controller controls the protection switches S1- SM+N-2 to be turned off so that the current of any branch is less than the first current value.
  • the current direction of the detection point G or H can be set to a preset direction, for example, set to a positive direction.
  • the current of all other branches flows into the branch where point G is located, causing the current detection direction at point G to be opposite to the preset direction at this time; when the branch where point G is located is normal, and the other branches are normal.
  • the branch where point G is located When there is a short-circuit fault in the circuit, the branch where point G is located outputs current to the branch where the short-circuit fault occurs. At this time, the current detection direction at point H is opposite to the preset current direction.
  • the controller determines that there is a short-circuit fault, and the controller controls the protection switches S1-S M+N-2 to be opened to make the current of any branch Both are less than the first current value, thereby protecting the photovoltaic unit and the circuit.
  • point G can be located in any branch, and the positive output terminals of all branches except the branch where point G is converged at point H, or the negative outputs of all branches except the branch where point G is located The ends converge at point H.
  • the protection switches S 1 -S M-2 can also be connected to the negative output terminal of the corresponding photovoltaic unit, or a protection switch is connected in series to both the positive and negative output terminals of the photovoltaic unit.
  • the fault tolerance can be improved by redundantly setting the protection switch.
  • At least one protection switch may be connected in series in the M photovoltaic unit branches shown in the figure. At this time, the controller controls the protection switch to turn off so that the current of any branch is zero.
  • the protection switches S M-1 -S M+N-2 can also be connected to the negative output end of the corresponding branch, or both the positive and negative output ends of the second type of photovoltaic unit branch are connected in series.
  • a protection switch can improve fault tolerance by redundantly setting the protection switch.
  • the protection device when the protection device is connected to multiple photovoltaic units through the interface, it can be realized by multiple combinations when multiple photovoltaic units are connected.
  • the controller of the protection device can when the absolute value of the current of any branch is greater than The absolute value of the current of the DC bus, or when the current direction of any branch is opposite to the preset current direction, the protection switch is controlled to turn off so that the current of any branch is less than the first current value, thereby protecting the photovoltaic unit and the line, and Since only the protection switch is added to the circuit, the resistance is smaller than that of the fuse, so the loss rate loss is also reduced.
  • the Y terminal can also be arranged on the side of the photovoltaic unit, thereby reducing the cost of the cable.
  • FIG. 20B is a schematic diagram of still another protection device provided by an embodiment of the application.
  • the device supports the connection of photovoltaic units and protection units in series or in parallel.
  • i photovoltaic units are connected in parallel through the protection units at intervals as an example for illustration.
  • the protection unit may also be connected in series with the photovoltaic unit, for example, the protection unit may be arranged at the position of point G in the figure.
  • the protection unit Q can be a combination of one or more of a fuse, an optimizer, and a shut-off box, and can also be other circuit devices that can protect the circuit when a short-circuit fault occurs in the circuit, which is not specifically limited in the embodiment of the present application.
  • k in the figure can be determined according to actual conditions, which is not specifically limited in the embodiment of the present application.
  • the protection switch is also used to prevent the protection unit from triggering the protection action when it is disconnected, that is, when the current photovoltaic power generation system using the protection unit is modified, the protection unit does not need to be dismantled, so that the protection unit can be directly accessed. Device.
  • the above embodiments illustrate the working principle of the controller of the protection device when a short-circuit fault occurs in the photovoltaic unit or the line where the photovoltaic unit is located.
  • the controller has a short circuit of positive and negative poles, a short circuit of the DC bus, or a subsequent stage in the protection device.
  • the working principle of the circuit when the DC bus of the circuit is short-circuited.
  • the device further includes a power converter 2001, and some or all of the photovoltaic units are coupled to the DC bus through the power converter 2001.
  • the power converter 2001 is a DC/DC converter, such as a BOOST circuit, which is used for boosting DC power.
  • FIG. 21 is a schematic diagram of another protection device provided by an embodiment of the application.
  • FIG. 21 The difference between the implementation shown in FIG. 21 and FIG. 20 is that it further includes a DC switch 102 arranged on the positive and negative DC bus.
  • the DC bus is short-circuited, or the DC bus of the subsequent circuit is short-circuited, that is, a short-circuit occurs between the positive and negative DC bus where point A and point B are located, which will cause the voltage of the DC bus. Decrease and current increase, so point A or B can be the detection point.
  • the controller controls the DC switch 102 Disconnect to cut off the short-circuit current.
  • the controller realizes the protection function by detecting the current direction, it is necessary to add a current sensor (that is, the fifth current sensor) to measure the absolute value of the current at point A or B, and then add a voltage sensor to measure the current at point A or B.
  • a current sensor that is, the fifth current sensor
  • a voltage sensor to measure the current at point A or B. The absolute value of the voltage at a point.
  • the second current value and the first voltage value may be determined according to actual conditions, which are not specifically limited in the embodiment of the present application.
  • This embodiment takes the device shown in FIG. 20A as an example for description. It can be understood that for the devices provided in device embodiments 1 to 10, the solutions provided in this embodiment can also be used, and this embodiment will not be one by one here. Go into details.
  • the protection device provided by the embodiments of the present application can not only protect the photovoltaic unit and the line when a short-circuit fault occurs in the photovoltaic unit or the line where the photovoltaic unit is located, but also the positive and negative poles and the DC bus in the protection device. Short-circuit, or when the DC bus of the subsequent circuit is short-circuited, cut off the short-circuit current in time to protect the circuit.
  • the controller is specifically used to determine that the photovoltaic power generation system is faulty when the detected value of the parameter of the branch exceeds the first preset parameter value range, or when the detected value of the DC bus parameter exceeds the second preset parameter value range .
  • the parameter detection value may be at least one of a voltage value, a current value, a power value, or a temperature value.
  • the parameter detection value When the parameter detection value is abnormal, for example, when the voltage of the branch decreases, the current increases, the power increases, and the temperature increases, it can be determined that the branch has a short-circuit fault.
  • the embodiment of the present application does not specifically limit the first preset parameter value range and the second preset parameter value range, and the range can be pre-calibrated and stored in the controller, and called when it is to be used.
  • the controller determines that the photovoltaic power generation system is faulty when the leakage current detection value of the DC bus is greater than the third current value, or the leakage current detection value of the existing branch is greater than the fourth current value.
  • the leakage current fault can be determined as the branch circuit where the leakage current fault occurs, or the leakage current fault can be located on the DC bus.
  • the controller is specifically configured to determine that the photovoltaic power generation system is faulty when it is determined that there is an arc fault in the branch according to the current detection values of all branches, or when it is determined that the DC bus has an arc fault according to the current detection value of the DC bus. .
  • the controller can specifically determine whether there is an arc fault according to the degree of deviation between the current detection value and the preset standard value.
  • the controller is also used to control the opening or closing of the protection switch according to the control instruction sent by the host computer, thereby realizing active control of the protection switch.
  • the protection switches in the embodiments of the present application and the above embodiments may be rotary DC disconnecting switches or DC circuit breakers.
  • the controller is also used to control the protection switch to close when the fault is eliminated or a preset time has passed.
  • using the protection device of the photovoltaic power generation system provided in the embodiments of the present application can effectively protect the photovoltaic unit and the line when the photovoltaic power generation system fails, thereby improving the safety of the photovoltaic power generation system.
  • the embodiment of the present application also provides a protection method of a photovoltaic power generation system, which is used to control the protection device provided in the above embodiment, and the method can be executed by the controller of the protection device.
  • the method determines that when a photovoltaic power generation system fails according to the parameter detection value of the branch or the DC bus, the control protection switch is turned off.
  • the parameter detection value is the reverse current value
  • the fault of the photovoltaic power generation system is determined according to the parameter detection value of the branch or DC bus, which specifically includes:
  • FIG. 22 is a flowchart of a short-circuit protection method provided by an embodiment of the application.
  • the method includes the following steps:
  • the current of all branches merges into the DC bus, so the absolute value of the current of the DC bus is greater than the absolute value of the current of any branch, and the direction of the current is from the positive pole of the photovoltaic unit to the positive DC bus.
  • the output current of all other normal branches will flow to the branch where the short-circuit fault occurs.
  • the voltage of the DC bus will decrease, and the current direction of the existing branch is the direction of the short-circuit.
  • the faulty branch that is, the reverse current of the existing branch is greater than the first current value.
  • the first current value can be determined according to the actual situation, and the embodiment of the present application does not specifically limit it.
  • the first current value can be a relatively small value, for example, 0 , That is, when there is a reverse current in the branch, the protection switch is controlled to open to realize the protection of the photovoltaic unit and the line.
  • the protection function can be realized by detecting the absolute value of the current or detecting the direction of the current, which will be described in detail below.
  • the protection switch is controlled to be turned off so that the current of any branch is less than the first current value.
  • the current direction of the detection points G and H can be set to a preset direction, for example, set to a positive direction.
  • the protection switch when applied to a protection device, when the reverse current of the branch is greater than the first current value, the protection switch is controlled to be turned off, specifically when the absolute value of the branch current is greater than When the current of the DC bus is absolute value, or when there is a branch current direction opposite to the preset current direction, the protection switch is controlled to turn off so that the current of any branch is less than the first current value, thereby protecting the photovoltaic unit and the line.
  • the device further includes a power circuit, and the DC bus is connected to the input end of the power circuit through a DC switch.
  • an embodiment of the present application also provides another device control method, which is used in the device The protection circuit when the positive and negative poles are short-circuited inside, or the rear-stage busbar is short-circuited, will be described in detail below.
  • FIG. 23 is a flowchart of another short-circuit protection method provided by an embodiment of the application.
  • the method includes the following steps:
  • the second current value and the first voltage value may be determined according to actual conditions, which are not specifically limited in the embodiment of the present application.
  • this method can cut off the short-circuit current in time when the positive and negative poles are short-circuited inside the protection device, or the downstream busbar is short-circuited, so as to realize the protection of the device and the downstream circuit.
  • the parameter detection value is at least one of voltage value, current value, power value, or temperature value
  • determining that the photovoltaic power generation system is faulty according to the parameter detection value of the branch or DC bus which specifically includes:
  • the photovoltaic power generation system When judging the leakage current fault, it is determined that the photovoltaic power generation system is faulty according to the parameter detection value of the branch or the DC bus, which specifically includes:
  • the leakage current detection value of the DC bus is greater than the third current value, or the leakage current detection value of the existing branch is greater than the fourth current value, it is determined that the photovoltaic power generation system is faulty.
  • the photovoltaic power generation system When judging an arc fault, it is determined that the photovoltaic power generation system is faulty according to the parameter detection value of the branch or the DC bus, which specifically includes:
  • using the protection method of the photovoltaic power generation system provided by the embodiments of the present application can effectively protect the photovoltaic unit and the line when the photovoltaic power generation system fails, thereby improving the safety of the photovoltaic power generation system.
  • the embodiment of the present application also provides a photovoltaic power generation system, which will be described in detail below with reference to the accompanying drawings.
  • FIG. 24 is a schematic diagram of a photovoltaic power generation system provided by an embodiment of the application.
  • the photovoltaic power generation system 2400 includes: at least two photovoltaic units and a protection device.
  • the photovoltaic unit is at least one photovoltaic module formed through series and parallel connection.
  • the protection device can be connected to at least two photovoltaic units through an interface, and at least two photovoltaic units are connected in parallel with the DC bus within the device to form at least two branches, and each branch is connected to at least one of the Photovoltaic unit.
  • the protection switch of the protection device is used to make up to three photovoltaic units directly connect the DC bus in parallel inside the device when it is disconnected.
  • the protection device also includes a controller.
  • a controller please refer to the above embodiment, and this embodiment will not be repeated here.
  • the protection device may further include a power circuit 201, and the power circuit 201 is used for power conversion.
  • the power circuit 201 may be a DC-DC (DC-DC) conversion circuit.
  • DC-DC conversion circuit may specifically be a boost (Boost) circuit, Buck circuit or Buck-Boost circuit, this application does not specifically limit this.
  • the power circuit 201 may be a direct current-alternating current (DC-AC) conversion circuit, that is, an inverter (or inverter circuit), which is used to convert direct current into alternating current for output.
  • DC-AC direct current-alternating current
  • This embodiment uses the device shown in FIG. 20 as an example for description. It is understandable that the solutions provided in this embodiment can also be used for the devices provided in device embodiments 1 to 11, and this embodiment will not be described here. A repeat.
  • the embodiment of the present application provides a photovoltaic power generation system.
  • the controller can control all the branches when the reverse current of the branch is greater than the first current value.
  • the protection switch is turned off.
  • the controller controls the protection switch to turn off.
  • the Y wire harness originally used for the built-in fuse does not need to be placed under the inverter or DC combiner box of the photovoltaic power generation system, but can be placed on the side of the photovoltaic unit, thereby reducing photovoltaic power. Cable cost for power generation system.
  • the controller described in the embodiment of the present application may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof.
  • ASIC application-specific integrated circuit
  • PLD programmable logic device
  • the above-mentioned PLD can be a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), a general array logic (generic array logic, GAL) or any combination thereof.
  • CPLD complex programmable logic device
  • FPGA field-programmable gate array
  • GAL general array logic
  • At least one (item) refers to one or more, and “multiple” refers to two or more.
  • “And/or” is used to describe the association relationship of associated objects, indicating that there can be three types of relationships, for example, “A and/or B” can mean: only A, only B, and both A and B , Where A and B can be singular or plural.
  • the character “/” generally indicates that the associated objects before and after are in an “or” relationship.
  • the following at least one item (a) or similar expressions refers to any combination of these items, including any combination of a single item (a) or a plurality of items (a).
  • At least one 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, and c can be single or multiple.

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Abstract

本申请公开了一种光伏发电系统的保护装置、保护方法及光伏发电系统,涉及光伏发电技术领域。其中，该保护装置包括：接口、保护开关、直流母线和控制器；所述装置通过所述接口连接至少两个光伏单元，所述至少两个光伏单元在所述装置内部与所述直流母线耦合以形成至少两个支路，每个所述支路至少连接有一个所述光伏单元；所述保护开关，用于断开全部或部分所述光伏单元与所述直流母线的连接，使至多三个所述光伏单元直接并联；控制器用于当根据支路或直流母线的参数检测值确定光伏发电系统发生故障时，控制保护开关断开。。利用该装置，能够在光伏发电系统出现故障时有效保护光伏单元和线路，并且功率损耗低。

Description

一种光伏发电系统的保护装置、保护方法及光伏发电系统
本申请要求于2020年4月13日提交中国国家知识产权局、PCT国际申请号为PCT/CN2020/084500、发明名称为“一种短路保护装置、短路保护方法及光伏发电系统”的国际专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及光伏发电技术领域，尤其涉及一种光伏发电系统的保护装置、短路保护方法及光伏发电系统。
背景技术
光伏发电是利用半导体界面的光生伏特效应，将光能转变为电能的一种技术。光伏发电系统通常可以包括光伏单元、逆变器、交流配电设备等。其中，为了获得较高的输出电压或输出电流，光伏单元通常由多个光伏组件通过一定的串并联方式形成。为了提高光伏发电系统的发电效率，光伏单元会连接具有独立MPPT(Maximum Power Point Tracking，最大功率点跟踪)功能的器件以提高光伏发电系统的发电效率。
目前，为了提升光伏发电系统的直流配比(光伏单元的功率与逆变器的输入功率的比值)，通常每路MPPT器件连接至少两路光伏单元。以一路光伏单元出现短路或者光伏单元所在线路出现短路为例，此时短路电流为连接的其它路的光伏单元的输出电流之和，当连接的其它路的光伏单元数量仅为1时，由于短路电流较小，光伏单元和线路可以耐受此短路电流。但是当连接的其它路的光伏单元的数量为2或者更多时，短路电流较大，为了保护光伏单元和线路，可以在光伏单元的正输出端和/或负输出端串联熔断器，通过使熔断器熔断以保护光伏单元和线路。
但是，由于熔断器的熔断电流一般较高，而每路光伏单元的输出电流较低，因此多路光伏单元的短路电流之和难以达到熔断器熔断电流，导致熔断器并不能有效的保护光伏单元和线路，并且熔断器的内阻较大，还会导致光伏发电系统存在较大的功率损耗。
发明内容
本申请提供了一种光伏发电系统的保护装置、保护方法及光伏发电系统，能够在光伏发电系统故障时有效保护光伏单元和线路，并且功率损耗低。
第一方面，本申请实施例提供了一种光伏发电系统的保护装置，应用于光伏发电系统，该装置包括：接口、保护开关、直流母线和控制器；所述装置通过接口连接至少两个光伏单元，所述至少两个光伏单元在所述装置内部与所述直流母线并联以形成至少两个支路，每个所述支路至少连接有一个所述光伏单元；保护开关用于断开全部或部分光伏单元与直流母线的连接，以使至多三个所述光伏单元直接并联。控制器当根据支路或直流母线的参数检测值确定光伏发电系统发生故障时，控制保护开关断开。
由于该装置的保护开关在断开时使至多三个光伏单元直接并联。因此，当一个光伏单元可以承受两个光伏单元输出的电流时，当存在光伏单元出现故障时，至多有两个正常的光伏单元向其输出电流，此时电流在该故障的光伏单元的承受范围内，进而保护光伏组件和线路不会损坏。并且由于只在电路中增加了保护开关，相较于熔断器电阻小，降低了光 伏系统的损率损耗。此外，由于不再使用熔断器，原先用于内置熔断器的Y线束不需再设置于光伏发电系统的逆变器或者直流汇流箱的下部，而可以配置在光伏单元侧，从而还降低了电缆成本。
结合第一方面，在一种可能的实现方式中，参数检测值为反向电流值，控制器具体用于当存在支路的反向电流值大于第一电流值时，确定光伏发电系统存在故障。
当支路存在较大的反向电流时，表征此时其它支路输出的直流电向该支路进行反灌，即可确定该支路出现了短路故障。
结合第一方面，在第一种可能的实现方式中，所述装置通过所述接口连接至少三个光伏单元，其中，至多两个所述光伏单元直接并联连接所述直流母线，其余每个所述光伏单元分别与至少一个所述保护开关串联后再并联连接所述直流母线。
在一些实施例中，光伏单元或线路只能承受一个光伏单元的输出电流，当至多两个所述光伏单元直接并联连接所述直流母线时，若存在光伏单元出现短路故障，至多有一个正常的光伏单元向其输出短路电流，其余光伏单元均可直接断开，此时短路电流在该故障的光伏单元的承受范围内，进而保护光伏组件和线路不会损坏。
结合第一方面，在第二种可能的实现方式中，所述装置通过所述接口连接至少三个光伏单元，其中，至多三个所述光伏单元直接并联连接所述直流母线，其余每个所述光伏单元分别与至少一个所述保护开关串联后再并联连接所述直流母线。
在一些实施例中，光伏单元或线路的可以承受两个光伏单元的输出电流，因此当至多三个所述光伏单元直接并联连接所述直流母线时，若存在光伏单元出现短路故障，至多有两个个正常的光伏单元向其输出短路电流，其余光伏单元均可直接断开，此时短路电流在该故障的光伏单元的承受范围内，进而保护光伏组件和线路不会损坏。
结合第一方面，在第三种可能的实现方式中，所述装置通过所述接口连接三个光伏单元，其中，两个光伏单元直接并联连接所述直流母线，另一个光伏单元与至少一个所述保护开关串联后并联连接所述直流母线。控制器能够在出现短路故障时控制保护开关断开，进而保护了光伏系统中的光伏单元和线路。
结合第一方面，在第四种可能的实现方式中，所述装置通过所述接口连接三个光伏单元，其中，两个光伏单元分别与至少一个所述保护开关串联后并联连接所述直流母线，另一个光伏单元直接并联连接所述直流母线。控制器能够在出现短路故障时控制保护开关断开，使得流入出现短路故障的光伏单元的电流为零，进而保护了光伏系统中的光伏单元和线路。
结合第一方面，在第五种可能的实现方式中，所述装置通过所述接口连接四个光伏单元，其中，两个光伏单元先并联再与至少一个所述保护开关串联，然后并联连接所述直流母线，其它两个光伏单元直接并联连接所述直流母线。控制器能够在出现短路故障时控制保护开关断开，进而保护了光伏系统中的光伏单元和线路。
结合第一方面，在第六种可能的实现方式中，所述装置通过所述接口连接四个光伏单元，其中，两个光伏单元直接并联，其余两个光伏单元分别与至少一个所述保护开关串联后再与所述两个光伏单元并联，然后并联接入所述直流母线。控制器能够在出现短路故 障时控制保护开关断开，进而保护了光伏系统中的光伏单元和线路。
结合第一方面，在第七种可能的实现方式中，所述装置通过所述接口连接四个光伏单元，其中，一个光伏单元与至少一个所述保护开关串联后并联连接所述直流母线，另外三个光伏单元直接并联连接所述直流母线。此时光伏单元或线路的可以承受两个光伏单元的输出电流，控制器能够在出现短路故障时控制保护开关断开，进而保护了光伏系统中的光伏单元和线路。
结合第一方面，在第八种可能的实现方式中，所述装置通过所述接口连接四个光伏单元，其中，三个光伏单元先并联再与至少一个所述保护开关串联，然后并联连接所述直流母线，另一个光伏单元直接并联连接所述直流母线。此时光伏单元或线路的可以承受两个光伏单元的输出电流，控制器能够在出现短路故障时控制保护开关断开，进而保护了光伏系统中的光伏单元和线路。
结合第一方面，在第九种可能的实现方式中，当光伏单元与一个保护开关串联时，所述保护开关串联在所述光伏单元的正输出端或负输出端，控制保护开关断开，即可控制对应的光伏单元所在线路断路。
结合第一方面，在第十种可能的实现方式中，当所述光伏单元与两个所述保护开关串联时，两个所述保护开关分别串联在所述光伏单元的正输出端和负输出端。通过冗余设置保护开关，提升了系统的容错能力，并且能够彻底切断短路的光伏单元与系统的连接，便于进行维护与检修。
结合第一方面，在第十一种可能的实现方式中，当多个所述光伏单元先并联再与一个所述保护开关串联时，多个光伏单元的正输出端并联后与一个所述保护开关串联，或多个光伏单元的负输出端并联后与另一个所述保护开关串联，控制保护开关断开，即可控制对应的光伏单元所在线路断路。
结合第一方面，在第十二种可能的实现方式中，当多个所述光伏单元先并联再与两个所述保护开关串联时，多个光伏单元的正输出端并联后与一个所述保护开关串联，且多个光伏单元的负输出端并联后与另一个所述保护开关串联，通过冗余设置保护开关，提升了系统的容错能力。
结合第一方面，在第十三种可能的实现方式中，控制器用于当存在支路的反向电流大于第一电流值时控制所述保护开关断开，具体包括：控制器用于当存在支路的电流的绝对值大于所述直流母线的电流的绝对值时，确定存在支路的反向电流大于所述第一电流值，控制所述保护开关断开。
这是因为当无短路故障时，所有光伏单元的输出电流汇入直流母线，直流母线的电流绝对值大于任意支路的电流的绝对值。当存在一个光伏单元出现短路故障时，其它正常的光伏单元的输出电流会流向该短路的光伏单元，此时直流母线的电流的绝对值小于任意支路的电流的绝对值。
结合第一方面，在第十四种可能的实现方式中，所述装置还包括：第一电流传感器和第二电流传感器；第一电流传感器用于获取所述直流母线的电流的绝对值并发送至所述控制器；第二电流传感器用于获取预设支路的电流的绝对值并发送至所述控制器。
控制器通过比较支路的电流的绝对值大小和直流母线的电流的绝对值大小，以确定是否存在光伏单元或线路出现短路故障。
结合第一方面，在第十五种可能的实现方式中，所述装置还包括：功率电路；
所述功率电路为直流-直流DC-DC变换电路或直流-交流DC-AC变换电路。
结合第一方面，在第十六种可能的实现方式中，所述装置还包括：第一电压传感器和直流开关；所述直流母线通过所述直流开关连接所述功率电路的输入端；所述第一电压传感器用于获取所述直流母线的电压的绝对值并发送至所述控制器。
结合第一方面，在第十七种可能的实现方式中，控制器用于当存在支路的反向电流大于第一电流值时控制所述保护开关断开，具体包括：控制器当存在支路的电流方向与预设电流方向相反时，确定存在支路的反向电流大于所述第一电流值，控制所述保护开关断开。
这是因为当光伏单元出现短路故障时，其它所有正常的光伏单元所在支路的电流流入该故障光伏单元所在支路，导致此时故障光伏单元所在支路的电流检测方向与正常时的预设方向相反；而当该光伏单元所在支路正常，其它支路中存在短路故障时，光伏单元所在支路向出现短路故障的支路输出电流，此时其它支路中存在电流检测方向与预设电流方向相反。
结合第一方面，在第十八种可能的实现方式中，所述装置还包括：第三电流传感器和第四电流传感器；所述第三电流传感器用于获取第一检测点的电流检测方向并发送至所述控制器，所述第一检测点位于任意一个支路；所述第四电流传感器用于获取第二检测点的电流检测方向并发送至所述控制器，除第一检测点所在支路外的其它所有支路汇集于所述第二检测点。
结合第一方面，在第十九种可能的实现方式中，所述控制器具体用于：当所述第一检测点的电流检测方向和第一检测点的预设电流方向相反，或第二检测点的电流检测方向和第二检测点的预设电流方向相反时，控制所述保护开关断开。
结合第一方面，在第二十种可能的实现方式中，该保护装置还包括：功率电路；功率电路为直流-直流DC-DC变换电路或直流-交流DC-AC变换电路。
结合第一方面，在第二十一种可能的实现方式中，所述装置还包括：第五电流传感器、第二电压传感器和直流开关；直流母线通过所述直流开关连接所述功率电路的输入端；第五电流传感器用于获取所述直流母线的电流的绝对值并发送至所述控制器；第二电压传感器用于获取所述直流母线的电压的绝对值并发送至所述控制器。
结合第一方面，在第二十二种可能的实现方式中，当保护装置内部出现正负极短路、直流母线短路，或者后级电路的直流母线出现短路时，会导致直流母线的电压降低以及电流增大，因此控制器还用于：当所述直流母线的电流的绝对值大于第二电流值且所述直流母线的电压的绝对值小于第一电压值时，控制所述直流开关断开，实现对电路的保护。
结合第一方面，在第二十三种可能的实现方式中，当所述光伏单元和保护单元串联或者并联后通过所述接口连接所述装置时，所述保护开关，还用于在断开时使所述保护单元不触发保护动作。
即对于目前采用保护单元的光伏发电系统进行改造时，可以无需对保护单元进行拆除处理，以便于直接入所述断路保护装置。
结合第一方面，在第二十四种可能的实现方式中，所述保护单元至少包括以下中的一项：熔断器、优化器和关断盒。
结合第一方面，在第二十五种可能的实现方式中，当所述装置包括至少两个保护开关时，所述至少两个保护开关由同一个控制器控制，或由多个控制器控制。
结合第一方面，在一种可能的实现方式中，控制器具体用于当支路的参数检测值超过第一预设参数值范围，或当直流母线的参数检测值超过第二预设参数值范围时，确定光伏发电系统发生故障。该参数检测值可以为电压值、电流值、功率值或温度值中的至少一种。
当参数检测值异常时，例如支路的电压降低、电流增大、功率增大以及温度升高时，即可确定该支路出现了短路故障。
结合第一方面，在一种可能的实现方式中，控制器具体用于当直流母线的漏电流检测值大于第三电流值时，或存在支路的漏电流检测值大于第四电流值时，确定光伏发电系统发生故障。当出现漏电流检测值异常时，表明光伏发电系统出现了漏电流故障。利用本申请的方案，可以将漏电流故障进行定为，确定漏电流故障出现的支路，或者将漏电流故障定位在直流母线。
结合第一方面，在一种可能的实现方式中，控制器具体用于当根据所有支路的电流检测值确定存在支路出现电弧故障，或根据直流母线的电流检测值确定直流母线出现电弧故障时，确定光伏发电系统出现故障。控制器具体可以根据电流检测值和预设标准值的偏移程度来确定是否存在电弧故障。
结合第一方面，在一种可能的实现方式中，控制器还用于根据上位机发送的控制指令控制所述保护开关断开或闭合，进而实现保护开关的主动控制。
结合第一方面，在一种可能的实现方式中，至多三个光伏单元直接并联后连接一个接口，或至多三个光伏单元分别通过对应的接口后在装置内部并联。
结合第一方面，在一种可能的实现方式中，保护开关为旋转式直流隔离开关或直流断路器。
结合第一方面，在一种可能的实现方式中，控制器还用于当确定故障排除后或经过预设时间后控制保护开关闭合。
结合第一方面，在一种可能的实现方式中，该保护装置还包括直流/直流变换器。直流母线连接直流/直流变换器的输入端，直流/直流变换器的输出端为光伏发电系统的保护装置的输出端。直流/直流变换器，用于将从直流母线获取的直流电进行直流变换后输出。此时该光伏发电系统的保护装置为升压直流汇流箱。
结合第一方面，在一种可能的实现方式中，该保护装置还包括直流/交流变换器，直流母线连接直流/交流变换器的输入端，直流/交流变换器的输出端为光伏发电系统的保护装置的输出端；直流/交流变换器，用于将从直流母线获取的直流电转换为交流电后输出。此时该光伏发电系统的保护装置为逆变器。
第二方面，本申请还提供了一种光伏发电系统的保护方法，应用于控制保护装置，装 置通过接口连接至少两个光伏单元，至少两个光伏单元在装置内部与直流母线耦合以形成至少两个支路，每个支路至少连接有一个光伏单元；保护开关用于断开全部或部分光伏单元与直流母线的连接，使至多三个光伏单元直接并联。该方法包括：
根据支路或直流母线的参数检测值确定光伏发电系统发生故障时，控制保护开关断开。
结合第二方面，在一种可能的实现方式中，参数检测值为反向电流值，根据支路或直流母线的参数检测值确定光伏发电系统发生故障，具体包括：
当存在支路的反向电流值大于第一电流值时，确定光伏发电系统存在故障。
利用该方法，保护开关在断开时使至多三个光伏单元直接并联。因此，当一个光伏单元可以承受两个光伏单元输出的电流时，当存在光伏单元出现故障时，至多有两个正常的光伏单元向其输出电流，此时电流在该故障的光伏单元的承受范围内，进而保护光伏组件和线路不会损坏。
结合第二方面，在一种可能的实现方式中，参数检测值为反向电流值，根据支路或直流母线的参数检测值确定光伏发电系统发生故障，具体包括：
当存在支路的反向电流值大于第一电流值时，确定光伏发电系统存在故障。
结合第二方面，在第一种可能的实现方式中，所述装置还包括功率电路，所述直流母线通过直流开关连接所述功率电路的输入端，所述方法还包括：当所述直流母线的电流的绝对值大于第二电流值且所述直流母线的电压的绝对值小于第一电压值时，控制所述直流开关断开。
利用该方法，能够在该保护装置内部出现正负极短路，或者后级母线出现短路时及时切除短路电流，实现对装置以及后级电路的保护。
结合第二方面，在第二种可能的实现方式中，所述功率电路为直流-直流DC-DC变换电路或直流-交流DC-AC变换电路。
结合第二方面，在一种可能的实现方式中，参数检测值为电压值、电流值、功率值或温度值中的至少一项，根据支路或直流母线的参数检测值确定光伏发电系统发生故障，具体包括：
当支路的参数检测值超过第一预设参数值范围，或当直流母线的参数检测值超过第二预设参数值范围时，确定光伏发电系统发生故障。
结合第二方面，在一种可能的实现方式中，根据支路或直流母线的参数检测值确定光伏发电系统发生故障，具体包括：
当直流母线的漏电流检测值大于第三电流值时，或存在支路的漏电流检测值大于第四电流值时，确定光伏发电系统发生故障。
结合第二方面，在一种可能的实现方式中，根据支路或直流母线的参数检测值确定光伏发电系统发生故障，具体包括：
当根据所有支路的电流检测值确定存在支路出现电弧故障，或根据直流母线的电流检测值确定直流母线出现电弧故障时，确定光伏发电系统出现故障。第三方面，本申请还提供了一种光伏发电系统，包括至少两个光伏单元和以上任意一种实现方式所述的保护装置，每个光伏单元包括至少一个光伏组件，当光伏单元中包括多个光伏组件时，光 伏组件可以通过串联或者混联的方式连接。
该光伏发电系统的保护装置的控制器，能够当根据支路或直流母线的参数检测值确定光伏发电系统发生故障时，控制保护开关断开，以使至多三个所述光伏单元直接并联。进而保护了光伏系统中的光伏单元和线路，并且由于只在电路中增加了保护开关，相较于熔断器电阻小，因此还降低了光伏系统的损率损耗。
结合第三方面，在第一种可能的实现方式中，系统还包括：保护单元，光伏单元和所述保护单元串联或者并联后通过所述接口接入所述保护装置。
因此对于目前采用保护单元的光伏发电系统进行改造时，可以无需对保护单元进行拆除处理，以便于直接入所述断路保护装置。
结合第三方面，在第二种可能的实现方式中，该保护单元可以为熔断器、优化器和关断盒中的一项或多项的组合。
当该保护装置包括功率电路时，功率电路可以为直流-直流(DC-DC)变换电路，当功率电路为直流-直流变换电路时，该直流-直流变换电路具体可以为升压(Boost)电路、降压(Buck)电路或升降压(Buck-Boost)电路，此时该保护装置还可以为光伏发电系统的直流汇流箱。
功率电路还可以为直流-交流(DC-AC)变换电路，即逆变器(或称逆变电路)，用于将直流电变换为交流电后进行输出。
当保护装置不包括功率电路时，保护装置可以作为独立的设备接入光伏发电系统的直流汇流箱或者逆变器的输入端。
从以上技术方案可以看出，本申请提供的方案至少具有以下优点：
本申请实施例提供的光伏发电系统的保护装置可以应用于光伏发电系统，该装置的保护开关在断开时使至多三个光伏单元直接并联。例如，当使两个光伏单元在所述装置内部直接并联连接直流母线时，若其中一个光伏单元出现短路故障，则只会有一个正常的光伏单元向其输出短路电流，此时短路电流在该故障的光伏单元的承受范围内，进而保护光伏组件和线路不会损坏。具体的光伏单元和保护开关的连接方式可以根据实际需求进行配置。该保护装置的控制器能够根据支路或直流母线的参数检测值确定光伏发电系统发生故障时，控制保护开关断开，使至多三个所述光伏单元直接并联，进而保护了光伏系统中的光伏单元和线路，并且由于只在电路中增加了保护开关，相较于熔断器电阻小，降低了光伏系统的损率损耗。此外，由于不再使用熔断器，原先用于内置熔断器的Y线束不需再设置于光伏发电系统的逆变器或者直流汇流箱的下部，而可以配置在光伏单元侧，从而还降低了电缆成本。
附图说明
图1为现有技术采用的保护装置的示意图一；
图2为现有技术采用的保护装置的示意图二；
图3为现有技术采用的保护装置的示意图三；
图4为本申请实施例提供的一种支路的示意图；
图5为本申请实施例提供的另一种支路的示意图；
图6A为本申请实施例提供的一种保护装置的示意图；
图6B为本申请实施例提供的另一种保护装置的示意图；
图6C为本申请实施例提供的又一种保护装置的示意图；
图7为本申请实施例提供的另一种保护装置的示意图；
图8为本申请实施例提供的又一种保护装置的示意图；
图9为本申请实施例提供的再一种保护装置的示意图；
图10为本申请实施例提供的另一种保护装置的示意图；
图11为本申请实施例提供的又一种保护装置的示意图；
图12为本申请实施例提供的再一种保护装置的示意图；
图13为本申请实施例提供的另一种保护装置的示意图；
图14为本申请实施例提供的又一种保护装置的示意图；
图15为本申请实施例提供的再一种保护装置的示意图；
图16为本申请实施例提供的另一种保护装置的示意图；
图17为本申请实施例提供的又一种保护装置的示意图；
图18为本申请实施例提供的再一种保护装置的示意图；
图19为本申请实施例提供的另一种保护装置的示意图；
图20A为本申请实施例提供的又一种保护装置的示意图；
图20B为本申请实施例提供的再一种保护装置的示意图；
图20C为本申请实施例提供的再一种保护装置的示意图；
图21为本申请实施例提供的另一种保护装置的示意图；
图22为本申请实施例提供的一种短路保护方法的流程图；
图23为本申请实施例提供的另一种短路保护方法的流程图；
图24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
为了提升光伏发电系统的直流配比，通常每路MPPT器件连接至少两路光伏单元或者更多，并且为了在光伏单元出现短路或者线路出现短路时保护光伏单元和线路，在光伏单元的正输出端和/或负输出端串联熔断器(或称熔丝)。下面以每路MPPT器件连接三条支路为例进行说明。当每路MPPT器件连接更多条支路时的原理类似，本申请在此不再赘述。
一并参见图1至图3。其中，图1为光伏单元的正输出端和负输出端均串联熔断器时的示意图；图2为光伏单元的正输出端串联熔断器时的示意图；图3为光伏单元的负输出端串联熔断器时的示意图。
每路支路包括一个光伏组件101，三条支路在开关102前完成并联，然后通过直流开关102连接MPPT器件103。图1中的fuse1-fuse6、图2中的fuse1-fuse3以及图3中的fuse1-fuse3为熔断器，在线路中的电流过大时熔断以保护光伏组件和线路。
但是由于光伏单元的实际输出电流较小，因而使得熔断器难以熔断。以额定电流为15A的熔断器为例，基于熔断器的标准规定，熔断器不熔断时允许的电流可以达1.13 ×15＝16.95A，在一小时内熔断需要的电流为1.35×15＝20.25A，而短路电流难以满足熔断器熔断所需电流，因此熔断器可能不会熔断，导致并不能有效的保护光伏单元和线路。此外，每个熔断器的内阻可达9毫欧姆，因此存在较大的功率损耗与发热问题。在一些实施例中，由于需要考虑对电缆的保护，还需要将内置熔断器的Y线束设置在装置的下部，进而还导致了电缆成本上升。
为了解决上述技术问题，本申请提供了一种保护装置、短路保护方法及光伏发电系统，能够在光伏单元出现短路或者线路出现短路时有效保护光伏单元和线路，并且功率损耗低，下面结合附图具体说明。
以下说明中“第一”、“第二”等用语仅用于描述目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”等的特征可以明示或者隐含地包括一个或者更多个该特征。
在本申请中，除非另有明确的规定和限定，术语“连接”应做广义理解，例如，“连接”可以是固定连接，也可以是可拆卸连接，或成一体；可以是直接连接，也可以通过中间媒介间接连接。
为了使本技术领域的人员更好地理解本发明方案，下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚地描述。
装置实施例一：
以下实施例中的单个光伏单元可以包括一个光伏组件，还可以由多个光伏组件串并联形成，例如多个光伏组件先串联在一起形成光伏组串，多个光伏组串再并联在一起形成光伏单元。本申请实施例不具体限定光伏单元包括的光伏组件的具体数量，本领域技术人员可以根据实际需要来设置，而且本申请实施例中对单个光伏组件的电参数不做具体限定。连接同一个装置的多个光伏单元的输出电压可以相同，也可以不同，本申请实施例不作具体限定。
本申请实施例提供的保护装置应用于光伏发电系统，能够通过接口接入至少两个光伏单元，光伏单元通过接口接入后，能够在该装置的内部直接并联连接直流母线，或与保护开关串联后再并联连接直流母线，以将光伏单元的输出电流汇集于直流母线，进而在该装置内部形成至少两个支路，每个支路至少连接有一个光伏单元，下面首先具体说明支路的存在形式。
参见图4，该图为本申请实施例提供的一种支路的示意图。
其中，该支路包括一个光伏单元101a1，光伏单元101a1的正输出端为该支路的正输出端，光伏单元101a1的负输出端为该支路的负输出端，以下实施例的说明中不再区分。
参见图5，该图为本申请实施例提供的另一种支路的示意图。
其中，该支路可以包括多条图4所示的支路，因此包括了至少两个光伏单元，例如依次为101a1、101a2、…101ai。在一些实施例中，当支路中包括多个光伏单元时，支路中还可以包括保护开关(图中未示出)以实现对光伏单元和线路的保护。
可以理解的时，本申请实施例中的支路是电学领域的概念，指并联电路的分支电流流过的路线，继续以图5为例，则光伏单元101a1所在的线路可以称为一个支路，光伏单元 101a1和光伏单元101a1并联后形成的线路也可以称为一个支路。
各光伏单元的正输出端汇集后为该支路的正输出端，各光伏单元的负输出端汇集后为该支路的负输出端。
以下实施例中的“支路”具体指所有图4所示的支路以及图5所示的支路的总称。即除去干路(直流母线)外其余所有支路的总称。
下面结合附图具体说明该保护装置的工作原理。
参见图6，该图为本申请实施例提供的一种保护装置的示意图。
该保护装置200包括接口、保护开关S 1-S M-1、直流母线和控制器(图中未示出)。
该装置200可以通过接口连接至少两个光伏单元，本申请对接入的光伏单元的数量不作具体限定。至少两个光伏单元在装置内部与直流母线耦合以形成至少两个支路，每个支路至少连接有一个光伏单元。
该保护装置应用于光伏发电系统时，直流母线具体包括正直流母线和负直流母线。
其中，保护开关S 1-S M-1，用于断开全部或部分光伏单元与直流母线的连接，使至多三个光伏单元直接并联，即用于在断开时使至多三个光伏单元在装置内部直接并联连接直流母线。
例如，当单个光伏单元出现短路故障时，该故障的光伏单元可以承受1个其它正常的光伏单元的输出电流时，则保护开关S 1-S M-1在断开时使至多2个光伏单元在装置内部直接并联，此时图中的i和j的取值为2。
又例如，当单个光伏单元出现短路故障时，该故障的光伏单元可以承受2个其它正常的光伏单元的输出电流时，则保护开关S 1-S M-1在断开时使至多3个光伏单元在装置内部直接并联，此时图中的i和j的取值为3。
i和j的具体由实际的光伏单元的电流耐受值确定，本申请实施例在此不作具体限定。需要注意的是，图6中所示仅为便于作图以及说明，图中的i个光伏单元实际上在保护装置内部实现并联。
为了方便说明，以下以i和j的取值为2为例进行说明，在另一些实施例中，当i和j的取值为3时的原理类似，本申请在此不再赘述。
控制器用于当根据支路或直流母线的参数检测值确定光伏发电系统发生故障时，控制所述保护开关断开。下面以出现短路故障为例进行说明，具体的，当参数检测值为反向电流值，控制器具体用于当存在支路的反向电流值大于第一电流值时，确定光伏发电系统存在故障。
下面说明控制器实现保护功能的原理。
当无短路故障时，所有支路的电流汇入直流母线，因此直流母线的电流绝对值大于任意支路的电流的绝对值，电流的方向为由光伏单元的正极流向正直流母线。而当任意支路出现短路故障时，其它所有的正常支路的输出电流会流向该出现短路故障的支路，此时导致直流母线的电压降低，并且存在支路的电流方向变化为流向该出现短路故障的支路，即存在支路的反向电流大于第一电流值。其中第一电流值可以根据实际情况确定，本申请实施例不作具体限定，优选的，为了能够尽早发现短路故障并触发保护开关的保护动作，该 第一电流值可以为较小的值，例如为0，即当存在支路出现反向电流时，控制器控制保护开关断开。
此时控制器确定存在光伏单元或线路出现短路故障，控制保护开关断开以实现对于光伏单元和线路的保护。
在一些实施例中，该保护装置200还包括功率电路201，功率电路用于进行功率变换，该功率电路可以为直流/直流(DC/DC)变换电路或直流-交流(DC/AC)变换电路。
当功率电路201为直流-直流变换电路时，该直流-直流变换电路具体可以为升压(Boost)电路、降压(Buck)电路或升降压(Buck-Boost)电路，此时该保护装置可以作为光伏发电系统的直流汇流箱，本申请对此不作具体限定。
当功率电路201为直流-交流电路时，该直流-交流电路用于将直流电变换为交流电进行输出，此时该保护装置可以作为光伏发电系统的逆变器。
在另一些实施例中，该保护装置也可以作为独立的装置设置于光伏发电系统的直流汇流箱或者逆变器的输入端。
综上所述，本申请实施例提供的保护装置可以通过接口接入多个光伏单元，该装置的保护开关在断开时使至多三个光伏单元在所述装置内部直接并联，以保护光伏组件和线路不会损坏，具体的光伏单元和保护开关的连接方式可以根据实际需求进行配置。该装置的控制器能够当存在支路的反向电流大于第一电流值时控制保护开关断开，进而保护了光伏系统中的光伏单元和线路，并且由于只在电路中增加了保护开关，相较于熔断器电阻小，因此还降低了光伏系统的损率损耗。此外，由于不再使用熔断器，原先用于内置熔断器的Y线束不需再设置于光伏发电系统的逆变器或者直流汇流箱的下部，而可以配置在光伏单元侧，从而还降低了电缆成本。
以上说明中以允许故障光伏组件承受来自其他光伏组件的反灌电流为例，实际应用中，为了更加符合安全规范要求，保护开关用于断开全部光伏单元与直流母线的连接，具体参见图6B所示。
参见图6B，该图为本申请实施例提供的另一种保护装置的示意图。
图6B和图6A的区别在于，还包括了保护开关S01和S02，进而使得所有保护开关断开时，断开全部光伏单元与直流母线的连接，即断开所有接口与直流母线间的连通线路。
此外，以上说明中均以至多三个光伏单元直接并联后连接一个接口为例。在另一些实施例中，至多三个光伏单元分别通过对应的接口后在装置内部并联，具体实现方式还可以参见图6C所示。
在一些实施例中，控制器具体当存在支路的电流的绝对值大于直流母线的电流的绝对值时，或者当存在支路的反向电流大于第一电流值时，确定存在支路的反向电流大于第一电流值，控制保护开关断开，下面结合具体的实现方式说明控制器的工作原理。
装置实施例二：
下面首先以该保护装置连接两路光伏单元为例进行说明。
参见图7，该图为本申请实施例提供的另一种保护装置的示意图。
该保护装置200通过接口接入两个光伏单元101a1和101a2。
两个光伏单元在该保护装置200内并联后通过直流开关102连接功率电路201，直流开关102用于保护电路，在一些实施例中也可以取消设置而短接。
其中，至少一个光伏单元还串联有保护开关S1。
下面说明控制器利用检测电流绝对值大小实现保护功能的原理。
当无短路故障时，两个光伏单元的电流汇入直流母线，直流母线的电流绝对值(检测点A或检测点B的检测电流的绝对值)大于任意支路的电流的绝对值(检测点C或检测点D的检测电流的绝对值)。
当存在一个光伏单元出现短路故障时，另一个正常的光伏单元的输出电流会流向该短路的光伏单元，此时直流母线的电流的绝对值小于任意支路的电流的绝对值。
控制器当存在支路的电流的绝对值大于直流母线的电流的绝对值时，控制保护开关S1断开。
具体的，当光伏单元101a1所在支路出现短路故障时，保护开关S1断开使得光伏单元101a2停止输出电流，进而保护了光伏单元和线路；当光伏单元101a2所在支路出现短路故障时，保护开关S1断开使得短路的支路断路，光伏单元101a1可以继续向装置200输出电流，维持正常工作状态。
在一些实施例中，可以通过电流传感器实现检测电流的大小与方向，电流传感器将检测结果发送给装置200的控制器。
以上实现方式可以通过第一电流传感器检测A点或B点的电流的绝对值，通过第二电流传感器检测C点或D点的电流的绝对值实现。
在一些实施例中，保护开关S1可以与光伏单元102a2的正输出端串联，也可以与光伏单元102a2的负输出端串联，还可以在光伏单元102a2的正输出端和负输出端均串联一个光伏单元以实现冗余控制，本申请实施例对此不作具体限定。
下面说明控制器利用检测电流方向实现保护功能的原理。
当无短路故障时，可以将检测点C和检测点D的电流方向设定为预设方向，例如可以设定为正方向。
当光伏单元101a1所在支路出现短路故障时，此时光伏单元101a2的输出电流流入光伏单元101a1所在支路，导致检测点C的电流方向与预设电流方向相反，为负方向，此时控制器控制保护开关S1断开使得光伏单元101a2停止输出电流，进而保护了光伏单元和线路；而当光伏单元101a2所在支路出现短路故障时，此时光伏单元101a1的输出电流流入光伏单元101a2所在支路，导致检测点D的电流方向与预设电流方向相反，此时控制器控制保护开关S1断开使得短路的支路断路，而光伏单元101a1可以继续正常向保护装置200输出电流。
该方式可以通过第三电流传感器检测C点的电流方向，并通过第四电流传感器检测D点的电流方向实现。
以上实施例中的检测点C和检测点D也可以位于对应的光伏单元的负输出端侧，或一个位于光伏单元的正输出端侧，另一个位于光伏单元的负输出端侧，此时控制器的工作原理类似，在此不再赘述。
综上所述，当保护装置通过接口连接两路光伏单元时，其控制器能够当存在支路电流的绝对值大于直流母线的电流的绝对值时，或存在支路电流方向与预设电流方向相反时，控制保护开关断开以使任意支路的电流小于第一电流值，进而保护了光伏单元和线路，并且由于只在电路中增加了保护开关，相较于熔断器电阻小(在一些实施例中，应用的保护开关的内阻仅0.3毫欧姆左右，小于熔断器的内阻)，因此还降低了损率损耗。此外，还可以将Y端子配置在光伏单元侧，从而降低了电缆成本。
以上实施例以该保护装置接入两路光伏单元为例说明，但目前为了提升光伏发电系统的直流配比，通常保护装置会对应连接3路、4路…甚至更多路光伏单元，下面首先说明每路装置对应连接3路光伏单元时的工作原理。
装置实施例三：
参见图8，该图为本申请实施例提供的又一种保护装置的示意图。
三个光伏单元的正输出端在保护装置内部并联后通过直流开关102连接功率电路201，直流开关102用于保护电路，实际应用中也可以取消设置而短接。
光伏单元101a1串联保护开关S1后并联连接直流母线，光伏单元101a3串联保护开关S2后并联连接直流母线。
下面说明控制器利用检测电流绝对值大小实现保护功能的原理。
当无短路故障时，三个光伏单元的输出电流汇入直流母线，因此直流母线的电流绝对值(检测点A或检测点B的检测电流的绝对值)大于任意支路的电流的绝对值(检测点C、检测点D和检测点E的检测电流的绝对值)。
当存在一个光伏单元出现短路故障时，其它正常的光伏单元的输出电流会流向出现短路故障的光伏单元，此时导致直流母线的电流的绝对值小于任意支路的电流的绝对值。
保护装置的控制器当直流母线的电流的绝对值小于任意支路的电流的绝对值时，控制保护开关S1和S2断开以使流入短路支路的电流为零，进而保护了光伏单元与线路。
该实现方式可以通过第一电流传感器检测直流母线(即检测点A或B)电流的绝对值，第二电流传感器检测任意支路(即检测点C、D或E)的电流的绝对值实现。
下面说明控制器利用检测电流方向实现保护功能的原理。
当无短路故障时，可以将C点、D点和E点的电流方向设定为预设电流方向，例如设定为正方向。
当存在光伏单元出现短路故障时，此时其它正常的光伏单元的输出电流会流向该出现短路故障的光伏单元，导致该出现短路故障的光伏单元中的电流方向与预设方向相反，此时控制器控制所述保护开关S1和S2断开以使流入短路支路的电流为零，进而保护了光伏单元与线路。
该方式可以通过三个电流传感器分别检测三个第一类光伏单元支路的电流方向实现。
在另一种可能的实现方式中，为了减少使用的电流传感器的数量，还可以通过检测G点和F点的电流方向确定是否存在短路故障，当光伏单元101a1和101a3所在的支路存在短路故障时，H点的电流检测方向会与预设电流方向相反，当光伏单元101a2所在的支路存在短路故障时，G点的电流检测方向会与预设电流方向相反。控制器可以当H点和G点中存在电流检测方向与预设电流方向相反时，控制保护开关断开以保护光伏单元和线路。
该方式可以通过第三电流传感器检测G点的电流方向，通过第四电流传感器检测H点的电流方向实现，相较于前一种实现方式能够减少使用的电流传感器的数量。
在一些实施例中，保护开关S1或保护开关S2也可以取消设置而短接，此时控制器控制保护开关断开后可以使流进短路故障的支路的电流小于第一电流值。
综上所述，当该保护装置通过接口连接3路光伏单元时，控制器能够当存在光伏单元的电流的绝对值大于直流母线电流的绝对值时，或存在支路的电流方向与预设电流方向相反时，控制保护开关断开以使任意支路的电流小于第一电流值，进而保护了光伏单元和线路，并且由于只在电路中增加了保护开关，相较于熔断器电阻小，因此还降低了损率损耗。此外，还可以将Y端子配置在光伏单元侧，从而降低了电缆成本。
装置实施例四：
参见图9，该图为本申请实施例提供的再一种保护装置的示意图。
其中，光伏单元101a1和101a2在所述保护装置的内部直接并联后连接直流母线，光伏单元101a3与保护开关S1串联后再并联接入装置的直流母线。
直流开关102用于保护电路，在一些实施例中也可以取消设置而短接。其中，以保护开关S1串联在光伏单元101a3的负极为例说明。在一些实施例中，保护开关S1也可以串联在光伏单元101a3的正极。
下面说明控制器利用检测电流绝对值大小实现保护功能的原理。
当无短路故障时，各个支路的电流汇入直流母线，因此直流母线的电流绝对值(检测点A或检测点B的检测电流的绝对值)大于任意支路的电流的绝对值(检测点C、D、E和F的检测电流的绝对值)。
当存在支路出现短路故障时，正常的支路的输出电流会流向该出现短路故障的支路，此时导致直流母线的电流的绝对值小于任意支路的电流的绝对值。
因此，保护装置的控制器当存在支路的电流的绝对值大于直流母线的电流的绝对值时，控制保护开关S1断开。具体的，当光伏单元101a3所在的支路出现短路故障时，保护开关S1断开能够使得流入故障支路电流为零，并使得光伏单元101a1和101a2还能够正常输出电流；当光伏单元101a1和101a2所在支路出现短路故障时，保护开关S1断开能够使光伏单元101a3所在的支路停止向故障支路输出电流，进而保护了光伏单元与线路。
该实现方式可以通过第一电流传感器检测直流母线(检测点A或检测点B)的电流的绝对值，第二电流传感器检测任意支路(检测点C、D、E或F中任意一处)的电流的绝对值实现，即需要两个电流传感器。
下面说明控制器利用检测电流方向实现保护功能的原理。
当无短路故障时，可以将检测点E和F的电流方向设定为预设方向，例如设定为正方向。
当光伏单元101a3所在的支路出现短路故障时，检测点E的电流方向会与预设电流方向相反；当光伏单元101a1和101a2所在支路出现短路故障时，检测点F的电流方向会与预设电流方向相反。
因此该实现方式可以通过两个电流传感器分别检测E点和F点的电流方向实现，当检测的电流方向中存在与预设电流方向相反的检测结果时，控制器控制保护开关S1断开以保护光伏单元与线路。
参见图10，该图为本申请实施例提供的另一种保护装置的示意图。
图10所示保护装置与图9的区别在于，保护开关S1串联在光伏单元101a1和101a2的负输出端(也可以串联在光伏单元101a1和101a2的正输出端)。此时控制器的工作原理与以上说明类似，本申请实施例在此不再赘述。
以上实施例中所述的检测点C、D和E也可以位于对应的光伏单元的负输出端侧。
综上所述，当该保护装置通过接口连接3路光伏单元时，其控制器能够当存在任意支路的电流的绝对值大于直流母线的电流的绝对值时，或存在任意支路的电流方向与预设电流方向相反时，控制保护开关断开以保护光伏单元和线路，并且由于只在电路中增加了保护开关，相较于熔断器电阻小，因此还降低了损率损耗。此外，还可以将Y端子配置在光伏单元侧，从而降低了电缆成本。
以上实施例以每路装置的输入端包括3路光伏单元为例说明，下面说明每路装置对应连接4路光伏单元时的工作原理。
装置实施例五：参见图11，该图为本申请实施例提供的又一种保护装置的示意图。
其中，4个光伏单元的正输出端在所述保护装置内部汇集于正直流母线的保护开关S1，每个第一类光伏单元支路的负输出端在保护装置内部均串联一个保护开关后汇集于负直流母线。
下面说明控制器利用检测电流绝对值大小实现保护功能的原理。
当无短路故障时，四个光伏单元的电流汇入直流母线，因此直流母线的电流绝对值(检测点A或B的检测电流的绝对值)大于任意支路的电流的绝对值(检测C点、D、E和F的检测电流的绝对值)。
当存在一个光伏单元出现短路故障时，其它正常的光伏单元的输出电流会流向该出现短路故障的光伏单元，此时导致直流母线的电流的绝对值小于任意支路的电流的绝对值，控制器控制保护开关断开以使的入短路支路的电流为0。
该实现方式可以通过第一电流传感器检测直流母线A和B点处的电流的绝对值，第二电流传感器检测任意第一类光伏单元支路(检测点C、D、E或F中的任意一点)的电流的绝对值实现。
下面说明控制器利用检测电流方向实现保护功能的原理。
当无短路故障时，可以将C点、D点、E点和F点的电流方向设定为预设方向，例如设定为正方向。
当存在光伏单元出现短路故障时，此时其它正常的光伏单元的输出电流会流向该短路的光伏单元，导致该短路的光伏单元所在支路中的电流方向与预设方向相反，此时控制器控制保护开关断开以使流入该故障支路的电流为零，进而保护了光伏单元与线路。
该实现方式可以通过四个电流传感器分别检测四个第一类光伏单元支路的电流方向实现。
在另一种可能的实现方式中，为了减少使用的电流传感器的数量，还可以通过检测G点和F点的电流方向确定是否存在短路故障。
当无短路故障时，可以将G点和H点的电流方向设定为预设方向，例如设定为正方向
当光伏单元101a1、101a3和101a4所在的支路存在短路故障时，H点的电流检测方向会与预设电流方向相反，当光伏单元101a2所在的支路存在短路故障时，G点的电流检测方向会与预设方向相反。
该方式可以通过两个电流传感器分别检测G点和H点的电流方向实现。
其中，在一些实施例中，保护开关S1、S2和S3也可以取消设置而短接，此时控制器控制保护开关断开可以使得流入短路支路的电流小于第一电流值以保护光伏单元和线路。
参见图12，该图为本申请实施例提供的再一种保护装置的示意图。
图12为另一种可能的实现方式，与图11所示方式的区别在于：光伏单元101a1的正输出端与光伏单元101a2的正输出端汇集于保护开关S1，并通过保护开关S1连接正直流母线；光伏单元101a3的正输出端与光伏单元101a4的正输出端汇集于保护开关S6，并通过保护开关S6连接正直流母线。
此时控制器可以采用图11所对应的工作原理，本申请实施例在此不再赘述。
参见图13，该图为本申请实施例提供的另一种保护装置的示意图。
图13为另一种可能的实现方式，与图11所示方式的区别在于：每个光伏单元的正输出端串联一个保护开关后汇集于正直流母线，每个光伏单元的负输出端串联一个保护开关后汇集于负直流母线。冗余设置保护开关能够进一步提升安全性，确保光伏单元所在支路能够被断开。
此时控制器可以采用图11所对应的工作原理，本申请实施例在此不再赘述。
可以理解的是，以上实施例中所述的检测点C、D、E和F也可以位于对应的光伏单元的负输出端侧。
综上所述，当该保护装置通过接口连接4路光伏单元时，其控制器能够在存在支路电流的绝对值大于直流母线的电流的绝对值时，或存在光伏单元的电流方向与预设电流方向相反时，控制保护开关断开以使任意支路的电流小于第一电流值，进而保护了光伏单元和线路，并且由于只在电路中增加了保护开关，相较于熔断器电阻小，因此还降低了损率损耗。此外，还可以将Y端子配置在光伏单元侧，从而降低了电缆成本。
装置实施例六：
参见图14，该图为本申请实施例提供的又一种保护装置的示意图。
其中，光伏单元101a1和101a2并联后接入所述装置的直流母线，光伏单元101a3和101a4所在的支路分别串联一个保护开关后接入所述装置的直流母线。
具体的，两个第一类光伏单元支路的正输出端汇集后连接正直流母线，两个第一类光伏单元支路的负输出端分别串联一个保护开关后汇集连接负直流母线。
光伏单元101a1和101a2的正输出端通过保护开关S1连接正直流母线，光伏单元101a1和101a2的负输出端通过保护开关S2连接负直流母线。
在一些实施例中，保护开关S1和S2也可以取消设置而短接。
下面说明控制器利用检测电流绝对值大小实现保护功能的原理。
当无短路故障时，各个支路的电流汇入直流母线，因此直流母线的电流绝对值(检测点A或B的检测电流的绝对值)大于任意支路的电流的绝对值(检测点C、D、E、F、G和H的检测电流的绝对值)。
当存在支路出现短路故障时，正常的支路的输出电流会流向该短路的支路，此时导致直流母线的电流的绝对值小于任意支路的电流的绝对值。
因此，装置的控制器当存在支路的电流的绝对值大于直流母线的电流的绝对值时，控制保护开关S1-S4断开，使得流入故障支路的电流为零，进而保护光伏单元和线路。
该实现方式可以通过第一电流传感器检测直流母线A点或B点电流的绝对值，第二电流传感器检测C、D、E、F、G或H中任意一处的电流的绝对值实现。
下面说明控制器利用检测电流方向实现保护功能的原理。
当无短路故障时，可以将检测点G和检测点H的电流方向设定为预设方向，例如设定为正方向。
当光伏单元101a3和101a4所在的支路出现短路故障时，H点的电流方向会与预设方向相反；当光伏单元101a1和101a2所在支路中存在短路故障时，G点的电流方向会与预设方向相反，因此控制器可以当H点和G点中的任意一点的电流检测方向与预设电流方向相反时，确定存在短路故障并控制保护开关S1-S4断开，使得流入故障支路的电流为零，进而保护光伏单元和线路。
该实现方式可以通过两个电流传感器分别检测G点和H点的电流方向实现。
在一些实施例中，开关S1、S3和S4也可以取消设置而短接，此时控制器控制保护开关断开能够使得流入短路支路的电流小于第一电流值，进而保护光伏单元和线路。
参见图15，该图为本申请实施例提供的再一种保护装置的示意图。
图15所示的实现方式与图14的区别在于：光伏单元101a3和101a4的正输出端汇集后通过保护开关S3连接正直流母线，光伏单元101a3的负输出端通过保护开关S4连接负直流母线，光伏单元101a4的负输出端通过保护开关S5连接负直流母线。
此时控制器可以采用图14所对应的工作原理实现对光伏单元和线路的保护，本申请实施例在此不再赘述。
参见图16，该图为本申请实施例提供的另一种保护装置的示意图。
图16所示的实现方式与图14的区别在于：包括光伏单元101a1和101a2并联， 包括光伏单元101a1和101a2的正输出端汇集后通过保护开关S1连接正直流母线，负输出端汇集后通过保护开关S4连接负直流母线；光伏单元101a3的正输出端连接正直流母线，负输出端通过保护开关S2连接负直流母线；光伏单元101a4的正输出端通过保护开关S3连接正直流母线，负输出端通过保护开关S4连接负直流母线。
此时控制器可以采用图14所对应的工作原理实现对光伏单元和线路的保护，本申请实施例在此不再赘述。
以上实施例中所述的检测点C、D、E和F也可以位于对应的光伏单元的负输出端侧。
综上所述，当该保护装置通过接口连接4路光伏单元，其控制器能够当存在任意支路的电流的绝对值大于直流母线的电流的绝对值，或存在任意支路的电流方向与预设电流方向相反时，控制保护开关断开以使任意支路的电流小于第一电流值，进而保护了光伏单元和线路，并且由于只在电路中增加了保护开关，相较于熔断器电阻小，因此还降低了损率损耗。此外，还可以将Y端子配置在光伏单元侧，从而降低了电缆成本。
装置实施例七：
参见图17，该图为本申请实施例提供的又一种保护装置的示意图。
其中，光伏单元101a1和101a2在所述装置内部直接并联，光伏单元101a1和101a2的正输出端通过保护开关S1连接正直流母线，负输出端通过保护开关S2连接负直流母线。光伏单元101a3和101a4在所述装置内部直接并联，光伏单元101a3和101a4的正输出端通过保护开关S3连接正直流母线，负输出端通过保护开关S4连接负直流母线。
下面说明控制器利用检测电流绝对值大小实现保护功能的原理。
当无短路故障时，各个支路的电流汇入直流母线，因此直流母线的电流绝对值(检测点A或B的检测电流的绝对值)大于任意支路的电流的绝对值(检测点C、D、E、F、G和H的检测电流的绝对值)。
当存在支路出现短路故障时，正常的支路的输出电流会流向该出现短路故障的支路，此时导致直流母线的电流的绝对值小于任意支路的电流的绝对值。
该实现方式可以通过一个电流传感器检测直流母线A点或B点电流的绝对值，另一个电流传感器检测C、D、E、F、G或H中任意一处的电流的绝对值实现。
下面说明控制器利用检测电流方向实现保护功能的原理。
当无短路故障时，可以将G点和H点的电流方向设定为预设方向，例如设定为正方向。
当光伏单元101a1和101a2所在的支路出现短路故障时，G点的电流方向会与预设电流方向相反；当光伏单元101a3和101a4所在的支路存在短路故障时，H点的电流方向会与预设电流方向相反，因此控制器可以当G点和H点中的任意一点的电流检测方向与预设电流方向相反时，确定存在短路故障并控制保护开关S1-S4断开，使得流入故障支路的电流为零，进而保护光伏单元和线路。
在一些实施例中，可以将保护开关S1和S2中的至少一个取消设置而短接，或者将保护开关S3和S4中的至少一个取消设置而短接，或者将保护开关S1和S2中的任 意一个以及保护开关S3和S4中的任意一个取消设置而短接，进而减少串联的保护开关的数量，以降低成本。此时控制器控制剩余保护开关断开后能够使得流入存在短路故障的支路的电流小于第一电流值，进而保护光伏单元和线路。
综上所述，该保护装置通过接口连接4路光伏单元，其控制器能够当存在支路的电流的绝对值大于直流母线的电流的绝对值时，或存在支路的电流方向与预设电流方向相反时，控制保护开关断开以使任意支路的电流小于第一电流值，进而保护了光伏单元和线路，并且由于只在电路中增加了保护开关，相较于熔断器电阻小，因此还降低了损率损耗。此外，还可以将Y端子配置在光伏单元侧，从而降低了电缆成本。
以上各实施例说明了该保护装置连接3路和4路光伏单元时控制器的工作原理，在一些实时例中，每路装置还可以对应连接更多路光伏单元，下面具体说明每路装置连接的光伏单元的数量大于4路时控制器的工作原理。
装置实施例八：
以保护装置通过接口并联接入M个第一类光伏单元支路为例。其中，M为大于或等于3的整数，至多j个光伏单元在所述装置内部直接连接直流母线，其余每个光伏单元分别至少串联一个保护开关后并联接入所述直流母线。
其中，当光伏单元与一个保护开关串联时，保护开关串联在光伏单元的正输出端或负输出端；当光伏单元与两个保护开关串联时，保护开关串联在光伏单元的正输出端和负输出端，以实现冗余保护。
单个光伏单元出现短路故障时，当该故障光伏单元可以承受一个其它正常的光伏单元的输出电流时，j的取值为0、1或2；当该故障光伏单元可以承受两个其它正常的光伏单元的输出电流时，j的取值为0、1、2或3。
以下说明以j为2为例进行说明。
参见图18，该图为本申请实施例提供的再一种保护装置的示意图。
其中，两个光伏单元直接并联连接直流母线，其余(M-2)个光伏单元分别串联一个保护开关后并联接入所述直流母线。
下面说明控制器利用检测电流绝对值大小实现保护功能的原理。
当无短路故障时，所有光伏单元的电流汇入直流母线，直流母线的电流绝对值(检测点A或检测点B的检测电流的绝对值)大于任意支路的电流的绝对值。
当存在一个光伏单元出现短路故障时，其它正常的光伏单元的输出电流会流向该短路的光伏单元所在的支路，此时直流母线的电流的绝对值小于任意光伏单元所在支路的电流的绝对值。
装置200的控制器当存在支路的电流的绝对值大于直流母线的电流的绝对值时，控制保护开关S 1-S M-2断开，以使的任意支路的电流小于第一预设电流，以保护光伏单元和线路。
以上实现方式可以通过第一电流传感器检测A点或B点的电流的绝对值，通过第二电流传感器检测任意支路的电流的绝对值实现。
下面说明控制器利用检测电流方向实现保护功能的原理。
当无短路故障时，可以将检测点G和检测点H的电流方向设定为预设方向，例如可以设定为正方向。
其中，G点可以位于任意一个支路的正输出端或负输出端，除G点所在支路之外的其它所有支路的正输出端汇集于H点，或除G点所在支路之外的其它所有支路的负输出端汇集于H点。
当G点所在支路存在短路故障时，其它所有支路的电流流入G点所在支路，导致此时G点的电流检测方向与预设方向相反；当G点所在支路正常，而其它支路中存在短路故障时，G点所在支路向出现短路故障的支路输出电流，此时H点的电流检测方向与预设电流方向相反。因此，控制器当G点或H点的电流检测方向与预设方向相反时，确定出现短路故障，控制器控制保护开关S1-S M-2均断开，以使任意支路的电流均小于第一电流值，进而保护光伏单元以及线路。
该方式可以通过第三电流传感器检测G点的电流方向，并通过第四电流传感器检测H点的电流方向实现。
在一些实施例中，保护开关S 1-S M-2还可以连接在对应的光伏单元的负输出端，或在光伏单元的正、负输出端均串联连接一个保护开关。通过冗余设置保护开关能够提升容错性。
在一些实施例中，也可以在所有的第一类光伏单元支路中均串联至少一个保护开关。此时控制器控制保护开关断开后使得任意支路的电流为零。
综上所述，当该保护装置通过接口连接至少三路光伏单元支路时，其控制器能够当存在任意支路电流的绝对值大于直流母线的电流的绝对值时，或存在支路电流方向与预设电流方向相反时，控制保护开关断开以使任意支路的电流小于第一电流值，进而保护了光伏单元和线路，并且由于只在电路中增加了保护开关，相较于熔断器电阻小，因此还降低了损率损耗。此外，还可以将Y端子配置在光伏单元侧，从而降低了电缆成本。
装置实施例九：
参见图19，该图为本申请实施例提供的另一种保护装置的示意图。
其中，每i个光伏单元在所述装置的内部直接并联后通过串联至少一个保护开关后连接装置的直流母线，N为大于或等于2的整数。
单个光伏单元出现短路故障时，当该故障光伏单元可以承受一个其它正常的光伏单元的输出电流时，i的取值为2；当该故障光伏单元可以承受两个其它正常的光伏单元的输出电流时，i的取值为2或3。
下面说明控制器利用检测电流绝对值大小实现保护功能的原理。
当无短路故障时，所有支路的电流汇入直流母线，直流母线的电流绝对值(检测点A或检测点B的检测电流的绝对值)大于任意支路的电流的绝对值。
当存在光伏单元出现短路故障时，其它正常的光伏单元的输出电流会流向该短路的第光伏单元所在的支路，此时直流母线的电流的绝对值小于任意支路的电流的绝对值。
保护装置的控制器当存在支路的电流的绝对值大于直流母线的电流的绝对值时，控制保护开关S 1-S N断开，以使的任意支路的电流小于第一预设电流，以保护光伏单元和线路。
以上实现方式可以通过第一电流传感器检测A点或B点的电流的绝对值，通过第二电流传感器检测任意支路的电流的绝对值实现。
下面说明控制器利用检测电流方向实现保护功能的原理。
当无短路故障时，可以将检测点G和检测点H的电流方向设定为预设方向，例如可以设定为正方向。
其中，G点可以位于任意一个支路的正输出端或负输出端，除G点所在支路之外的其它所有支路的正输出端汇集于H点，或除G点所在支路之外的其它所有支路的负输出端汇集于H点。
当G点所在支路存在短路故障时，其它所有支路的电流流入G点所在支路，导致此时G点的电流检测方向与预设方向相反；当G点所在支路正常，而其它支路中存在短路故障时，G点所在支路向出现短路故障的支路输出电流，此时H点的电流检测方向与预设电流方向相反。因此，控制器当G点或H点的电流检测方向与预设方向相反时，确定出现短路故障，控制器控制保护开关S 1-S N均断开，进而保护光伏单元以及线路。
该方式可以通过第三电流传感器检测G点的电流方向，并通过第四电流传感器检测H点的电流方向实现。
在一些实施例中，保护开关S 1-S N还可以连接在对应的支路的负输出端，或在对应的支路的正、负输出端均串联连接一个保护开关,通过冗余设置保护开关能够提升容错性。
综上所述，当该保护装置通过接口连接至少两路光伏单元时，其控制器能够当存在任意支路电流的绝对值大于直流母线的电流的绝对值时，或存在支路电流方向与预设电流方向相反时，控制保护开关断开以使任意支路的电流小于第一电流值，进而保护了光伏单元和线路，并且由于只在电路中增加了保护开关，相较于熔断器电阻小，因此还降低了损率损耗。此外，还可以将Y端子配置在光伏单元侧，从而降低了电缆成本。
装置实施例十：
参见图20A，该图为本申请实施例提供的又一种保护装置的示意图
其中，至多j个光伏单元直接在装置内部接入直流母线，(M-j)个光伏单元在装置内与至少一个开关串联后接入直流母线。至多i个光伏单元在装置的内部直接并联后再串联至少一个保护开关后接入装置的直流母线，N为大于或等于2的整数。
单个光伏单元出现短路故障时，当该故障光伏单元可以承受一个其它正常的光伏单元的输出电流时，i的取值为2，j的取值可以为0、1或2；当该故障光伏单元可以承受两个其它正常的光伏单元的输出电流时，i的取值为2或3，j的取值可以为0、1、2或3。
此时，为了使出现短路故障时，任意支路的电流能够小于光伏单元和线路可以耐受的最大电流值，以使任意支路的短路电流不会损坏光伏单元和线路，需要保护开关的数量为(M+N-2)个。
下面说明控制器利用检测电流绝对值大小实现保护功能的原理。
当无短路故障时，所有支路的电流汇入直流母线，因此直流母线的电流绝对值(A点或 B点的检测电流的绝对值)大于任意支路的电流的绝对值。而当任意支路出现短路故障时，其它所有的正常支路的输出电流会流向该出现短路故障的支路，此时导致直流母线无电流流过，即直流母线的电流的绝对值小于任意支路的电流的绝对值。
为了减少使用的电流传感器的数量，以上实现方式可以通过两个电流传感器实现，其中一个电流传感器检测直流母线的A点或B点的电流的绝对值，另一个电流传感器检测任意支路中的电流的绝对值。
控制器当直流母线的电流的绝对值小于支路电流的绝对值时，控制保护开关S1-S M+N-2均断开，以使任意支路的电流均小于第一电流值。
下面说明控制器利用检测电流方向实现保护功能的原理。
当无短路故障时，可以将检测点G或H的电流方向设定为预设方向，例如设定为正方向。
当G点所在支路存在短路故障时，其它所有支路的电流流入G点所在支路，导致此时G点的电流检测方向与预设方向相反；当G点所在支路正常，而其它支路中存在短路故障时，G点所在支路向出现短路故障的支路输出电流，此时H点的电流检测方向与预设电流方向相反。因此，控制器当G点或H点的电流检测方向与预设方向相反时，确定出现短路故障，控制器控制保护开关S1-S M+N-2均断开，以使任意支路的电流均小于第一电流值，进而保护光伏单元以及线路。
其中，G点可以位于任意一个支路，除G点所在支路之外的其它所有支路的正输出端汇集于H点，或除G点所在支路之外的其它所有支路的负输出端汇集于H点。
在一些实施例中，保护开关S 1-S M-2还可以连接在对应的光伏单元的负输出端，或在光伏单元的正、负输出端均串联连接一个保护开关。通过冗余设置保护开关能够提升容错性。
在一些实施例中，也可以在图示的M个光伏单元支路中均串联至少一个保护开关。此时控制器控制保护开关断开后使得任意支路的电流为零。
在一些实施例中，保护开关S M-1-S M+N-2还可以连接在对应的支路的负输出端，或在第二类光伏单元支路的正、负输出端均串联连接一个保护开关,通过冗余设置保护开关能够提升容错性。
综上所述，当该保护装置通过接口连接多路光伏单元，多路光伏单元接入时可以由多种组合方式实现，该保护装置的控制器能够当存在任意支路的电流的绝对值大于直流母线的电流的绝对值，或存在任意支路电流方向与预设电流方向相反时，控制保护开关断开以使任意支路的电流小于第一电流值，进而保护了光伏单元和线路，并且由于只在电路中增加了保护开关，相较于熔断器电阻小，因此还降低了损率损耗。此外，还可以将Y端子配置在光伏单元侧，从而降低了电缆成本。
进一步的，还可以参见图20B，该图为本申请实施例提供的再一种保护装置的示意图。
其中，装置支持光伏单元和保护单元串联或者并联后接入，图中以i个光伏单元依次间隔通过保护单元并联为例进行说明。在一些实施例中，保护单元也可以与光伏单元串联，例如保护单元可以设置在图中G点的位置。
保护单元Q可以为熔断器、优化器和关断盒中的一项或多项的组合，还可以为其它可 以在电路出现短路故障时保护电路器件，本申请实施例对此不作具体限定。
图中k的取值可以根据实际情况确定，本申请实施例对此不作具体限定。
此时保护开关还用于在断开时使保护单元不触发保护动作，即对于目前采用保护单元的光伏发电系统进行改造时，可以无需对保护单元进行拆除处理，以便于直接入所述断路保护装置。
需要注意的是，单个光伏单元出现短路故障时，当该故障光伏单元可以承受一个其它正常的光伏单元的输出电流时，为了不触发保护单元的保护动作，i的取值为2；当该故障光伏单元可以承受两个其它正常的光伏单元的输出电流时，为了不触发保护单元的保护动作，i的取值为2或3。
以上实施例说明了该保护装置的控制器在光伏单元或光伏单元所在线路出现短路故障时的工作原理，下面说明控制器在该保护装置的内部出现正负极短路、直流母线短路，或者后级电路的直流母线出现短路时的工作原理。
在另一些实施例中，还可以参见图20C，此时置还包括功率变换器2001，部分或全部所述光伏单元通过功率变换器2001与所述直流母线耦合。功率变换器2001为直流/直流变换器，例如为BOOST电路，用于对直流电进行升压变换。
装置实施例十一：
参见图21，该图为本申请实施例提供的另一种保护装置的示意图。
图21所示实现方式与图20的区别在于还包括设置在正负直流母线上的直流开关102。
当该保护装置内部出现正负极短路、直流母线短路，或者后级电路的直流母线出现短路时，即点A与点B所在的正、负直流母线之间出现短路，会导致直流母线的电压降低以及电流增大，因此可以以A点或B点为检测点，当检测点的电压的绝对值低于第一电压值且电流的绝对值大于第二电流值时，控制器控制直流开关102断开，以切除短路电流。
当控制器利用检测电流绝对值大小实现保护功能时，直流支路中已经存在电流传感器可以测量A点或B点的电流的绝对值，此时只需增加一个电压传感器测量以A点或B点的电压的绝对值。
当控制器利用检测电流方向实现保护功能时，此时需要通过增加一个电流传感器(即第五电流传感器)测量A点或B点的电流的绝对值，再增加一个电压传感器测量以A点或B点的电压的绝对值。
其中，第二电流值和第一电压值可以根据实际情况确定，本申请实施例对此不作具体限定。
本实施例以图20A所示装置为例进行说明，可以理解的是，对于装置实施例一至十中所提供的装置，同样可以采用本实施例提供的方案，本实施例在此不再一一赘述。
综上所述，利用本申请实施例提供的保护装置，不仅能够在在光伏单元或光伏单元所在线路出现短路故障时保护光伏单元和线路，还能在保护装置内部出现正负极短路、直流母线短路，或者后级电路的直流母线出现短路时及时切除短路电流，实现对电路的保护。
装置实施例十二：
以上说明中以利用反向电流值检测短路故障为例进行说明，下面说明利用其它的参数检测值实现故障检测的原理。
继续参见图6，控制器具体用于当支路的参数检测值超过第一预设参数值范围，或当直流母线的参数检测值超过第二预设参数值范围时，确定光伏发电系统发生故障。该参数检测值可以为电压值、电流值、功率值或温度值中的至少一种。
当参数检测值异常时，例如支路的电压降低、电流增大、功率增大以及温度升高时，即可确定该支路出现了短路故障。本申请实施例对第一预设参数值范围和第二预设参数值范围不作具体限定，该范围可以预先标定并存储在控制器中，待使用时进行调用。
在一些实施例中，控制器当直流母线的漏电流检测值大于第三电流值时，或存在支路的漏电流检测值大于第四电流值时，确定光伏发电系统发生故障。
当出现漏电流检测值异常时，表明光伏发电系统出现了漏电流故障。利用本申请的方案，可以将漏电流故障进行定为，确定漏电流故障出现的支路，或者将漏电流故障定位在直流母线。在一些实施例中，控制器具体用于当根据所有支路的电流检测值确定存在支路出现电弧故障，或根据直流母线的电流检测值确定直流母线出现电弧故障时，确定光伏发电系统出现故障。控制器具体可以根据电流检测值和预设标准值的偏移程度来确定是否存在电弧故障。
控制器还用于根据上位机发送的控制指令控制所述保护开关断开或闭合，进而实现对保护开关的主动控制。
本申请实施例及以上实施例中的保护开关可以为旋转式直流隔离开关或直流断路器。控制器还用于当确定故障排除后或经过预设时间后控制保护开关闭合。
综上所述，利用本申请实施例提供的光伏发电系统的保护装置，能够在光伏发电系统故障时有效保护光伏单元和线路，提升了光伏发电系统的安全性。
方法实施例
本申请实施例还提供了一种光伏发电系统的保护方法，用于控制以上实施例提供的保护装置，该方法可由该保护装置的控制器执行。
该方法根据支路或直流母线的参数检测值确定光伏发电系统发生故障时，控制保护开关断开。
具体的，参数检测值为反向电流值，根据支路或直流母线的参数检测值确定光伏发电系统发生故障，具体包括：
当存在支路的反向电流值大于第一电流值时，确定光伏发电系统存在故障。
下面具体说明。
参见图22，该图为本申请实施例提供的一种短路保护方法的流程图。
该方法包括以下步骤：
S2201：获取电流检测结果。
S2202：当存在支路的反向电流大于第一电流值时控制保护开关断开，支路包括至少一 个所述光伏单元。
下面说明实现保护功能的原理。
当无短路故障时，所有支路的电流汇入直流母线，因此直流母线的电流绝对值大于任意支路的电流的绝对值，电流的方向为由光伏单元的正极流向正直流母线。而当任意支路出现短路故障时，其它所有的正常支路的输出电流会流向该出现短路故障的支路，此时导致直流母线的电压降低，并且存在支路的电流方向为流向该出现短路故障的支路，即存在支路的反向电流大于第一电流值。其中第一电流值可以根据实际情况确定，本申请实施例不作具体限定，优选的，为了尽早发现短路故障并触发保护开关的保护动作，该第一电流值可以为较小的值，例如为0，即当存在支路出现反向电流时，控制保护开关断开以实现对于光伏单元和线路的保护。
具体的，可以通过检测电流绝对值大小或检测电流方向实现保护功能，下面具体说明。
下面说明利用检测电流绝对值大小实现保护功能的原理。
当无短路故障时，所有支路的电流汇入直流母线，因此直流母线的电流绝对值大于任意支路的电流的绝对值。而当任意支路出现短路故障时，其它所有的正常支路的输出电流会流向该出现短路故障的支路，此时导致直流母线无电流流过，即直流母线的电流的绝对值小于任意支路的电流的绝对值。
因此当直流母线的电流的绝对值小于支路电流的绝对值时，控制保护开关断开以使任意支路的电流均小于第一电流值。
下面说明利用检测电流方向实现保护功能的原理。
在任意一个支路上选择第一检测点G，除G点所在支路之外的其它所有支路的正输出端汇集于第二检测点H，或除G点所在支路之外的其它所有支路的负输出端汇集于第二检测点H。
当无短路故障时，可以将检测点G和H的电流方向设定为预设方向，例如设定为正方向。
当G点所在支路存在短路故障时，其它所有支路的电流流入G点所在支路，导致此时G点的电流检测方向与预设方向相反；当G点所在支路正常，而其它支路存在短路故障时，G点所在支路向出现短路故障的支路输出电流，此时H点的电流检测方向与预设电流方向相反。因此，当G点或H点的电流检测方向与预设方向相反时，确定出现短路故障，控制保护开关断开，以使任意支路的电流均小于第一电流值，进而保护光伏单元以及线路。
综上所述，利用本申请实施例提供的方法，应用于保护装置时，当存在支路的反向电流大于第一电流值时控制保护开关断开，具体当存在支路电流的绝对值大于直流母线的电流的绝对值时，或存在支路电流方向与预设电流方向相反时，控制保护开关断开以使任意支路的电流小于第一电流值，进而保护了光伏单元和线路。
继续参见图21，在一些实施例中，装置还包括功率电路，直流母线通过直流开关连接功率电路的输入端，此时本申请实施例还提供了另一种装置的控制方法，用于在装置内部出现正负极短路，或者后级母线出现短路时保护电路，下面具体说明。
参见图23，该图为本申请实施例提供的另一种短路保护方法的流程图。
该方法包括以下步骤：
S2301：获取当前直流母线的电流的绝对值以及直流母线的电压的绝对值。
S2302：当直流母线的电流的绝对值大于第二电流值且直流母线的电压的绝对值小于第一电压值时，控制直流开关断开。
当该保护装置的内部出现正负极短路，或者后级电路中的直流母线出现短路时，即点A与点B所在的正、负直流母线之间出现短路，会导致直流母线的电压降低以及电流增大，因此可以以A点或B点为检测点，当检测点的电压的绝对值低于第一电压值且电流的绝对值大于第二电流值时，控制器控制直流开关断开，以切除短路电流。
其中，第二电流值和第一电压值可以根据实际情况确定，本申请实施例对此不作具体限定。
综上所述，利用该方法，能够在该保护装置内部出现正负极短路，或者后级母线出现短路时及时切除短路电流，实现对装置以及后级电路的保护。
下面说明利用其它参数检测值进行故障判断的方法。
当参数检测值为电压值、电流值、功率值或温度值中的至少一项，根据支路或直流母线的参数检测值确定所述光伏发电系统发生故障，具体包括：
当支路的参数检测值超过第一预设参数值范围，或当直流母线的参数检测值超过第二预设参数值范围时，确定光伏发电系统发生故障。
当进行漏电流故障判断时，根据支路或直流母线的参数检测值确定光伏发电系统发生故障，具体包括：
当直流母线的漏电流检测值大于第三电流值时，或存在支路的漏电流检测值大于第四电流值时，确定光伏发电系统发生故障。
当进行电弧故障判断时，根据支路或直流母线的参数检测值确定光伏发电系统发生故障，具体包括：
当根据所有支路的电流检测值确定存在支路出现电弧故障，或根据直流母线的电流检测值确定直流母线出现电弧故障时，确定光伏发电系统出现故障。
综上所述，利用本申请实施例提供的光伏发电系统的保护方法，能够在光伏发电系统故障时有效保护光伏单元和线路，提升了光伏发电系统的安全性。
光伏发电系统实施例：
基于以上实施例提供的用于光伏发电系统的保护装置，本申请实施例还提供了一种光伏发电系统，下面结合附图具体说明。
参见图24，该图为本申请实施例提供的一种光伏发电系统的示意图。
该光伏发电系统2400包括：至少两个光伏单元和保护装置。
其中，光伏单元为至少一个光伏组件通过串并联形成。
该保护装置可以通过接口接入至少两个光伏单元，至少两个光伏单元在所述装置内部与所述直流母线并联以形成至少两个支路，每个所述支路至少连接有一个所述光伏单元。
该保护装置的保护开关用于在断开时使至多三个光伏单元在装置内部直接并联连接直 流母线。
该保护装置还包括控制器，关于控制器的说明可以参见以上实施例，本实施例在此不再赘述。
进一步的，该保护装置还可以包括功率电路201，功率电路201用于进行功率变换。
在一些实施例中，功率电路201可以为直流-直流(DC-DC)变换电路，当功率电路201为直流-直流变换电路时，该直流-直流变换电路具体可以为升压(Boost)电路、降压(Buck)电路或升降压(Buck-Boost)电路，本申请对此不作具体限定。
在一些实施例中，功率电路201可以为直流-交流(DC-AC)变换电路，即逆变器(或称逆变电路)，用于将直流电变换为交流电后进行输出。
本实施例以图20所示装置为例进行说明，可以理解的是，对于装置实施例一至十一中所提供的装置，同样可以采用本实施例提供的方案，本实施例在此不再一一赘述。
综上所述，利用本申请实施例提供光伏发电系统，当光伏发电系统的保护装置通过接口连接多个光伏单元时，控制器能够当存在支路的反向电流大于第一电流值时控制所述保护开关断开，具体的，控制器当存在任意支路的电流的绝对值大于直流母线的电流的绝对值，或存在任意支路电流方向与预设电流方向相反时，控制保护开关断开以使任意支路的电流小于第一电流值，进而保护了光伏系统中的光伏单元和线路，并且由于只在电路中增加了保护开关，相较于熔断器电阻小，因此还降低了光伏系统的损率损耗。此外，由于不再使用熔断器，原先用于内置熔断器的Y线束不需再设置于光伏发电系统的逆变器或者直流汇流箱的下部，而可以配置在光伏单元侧，从而还降低了光伏发电系统的电缆成本。
本申请实施例所述的控制器可以为专用集成电路(application-specific integrated circuit，ASIC)，可编程逻辑器件(programmable logic device，PLD)或其组合。上述PLD可以是复杂可编程逻辑器件(complex programmable logic device，CPLD)，现场可编程逻辑门阵列(field-programmable gate array，FPGA)，通用阵列逻辑(generic array logic,GAL)或其任意组合，本申请实施例不作具体限定。
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 (45)

  1. 一种光伏发电系统的保护装置，其特征在于，应用于光伏发电系统，所述装置包括：接口、保护开关、直流母线和控制器；
    所述装置通过所述接口连接至少两个光伏单元，所述至少两个光伏单元在所述装置内部与所述直流母线耦合以形成至少两个支路，每个所述支路至少连接有一个所述光伏单元；
    所述保护开关，用于断开全部或部分所述光伏单元与所述直流母线的连接，使至多三个所述光伏单元直接并联；
    所述控制器，用于当根据所述支路或直流母线的参数检测值确定所述光伏发电系统发生故障时，控制所述保护开关断开。
  2. 根据权利要求1所述的装置，其特征在于，所述参数检测值为反向电流值，所述控制器，具体用于当存在支路的反向电流值大于第一电流值时，确定所述光伏发电系统存在故障。
  3. 根据权利要求2所述的装置，其特征在于，所述装置通过所述接口连接至少三个光伏单元，其中，至多两个所述光伏单元直接并联连接所述直流母线，其余每个所述光伏单元分别与至少一个所述保护开关串联后再并联连接所述直流母线。
  4. 根据权利要求2所述的装置，其特征在于，所述装置通过所述接口连接至少三个光伏单元，其中，至多三个所述光伏单元直接并联连接所述直流母线，其余每个所述光伏单元分别与至少一个所述保护开关串联后再并联连接所述直流母线。
  5. 根据权利要求2所述的装置，其特征在于，所述装置通过所述接口连接三个光伏单元，其中，两个光伏单元直接并联连接所述直流母线，另一个光伏单元与至少一个所述保护开关串联后并联连接所述直流母线。
  6. 根据权利要求2所述的装置，其特征在于，所述装置通过所述接口连接三个光伏单元，其中，两个光伏单元分别与至少一个所述保护开关串联后并联连接所述直流母线，另一个光伏单元直接并联连接所述直流母线。
  7. 根据权利要求2所述的装置，其特征在于，所述装置通过所述接口连接四个光伏单元，其中，两个光伏单元先并联再与至少一个所述保护开关串联，然后并联连接所述直流母线，其它两个光伏单元直接并联连接所述直流母线。
  8. 根据权利要求2所述的装置，其特征在于，所述装置通过所述接口连接四个光伏单元，其中，两个光伏单元直接并联，其余两个光伏单元分别与至少一个所述保护开关串联后再与所述两个光伏单元并联，然后并联接入所述直流母线。
  9. 根据权利要求2所述的装置，其特征在于，所述装置通过所述接口连接四个光伏单元，其中，一个光伏单元与至少一个所述保护开关串联后并联连接所述直流母线，另外三个光伏单元直接并联连接所述直流母线。
  10. 根据权利要求2所述的装置，其特征在于，所述装置通过所述接口连接四个光伏单元，其中，三个光伏单元先并联再与至少一个所述保护开关串联，然后并联连接所述直流母线，另一个光伏单元直接并联连接所述直流母线。
  11. 根据权利要求3-6、8-9中任意一项所述的装置，其特征在于，当所述光伏单元与 一个所述保护开关串联时，所述保护开关串联在所述光伏单元的正输出端或负输出端。
  12. 根据权利要求3-6、8-9中任意一项所述的装置，其特征在于，当所述光伏单元与两个所述保护开关串联时，两个所述保护开关分别串联在所述光伏单元的正输出端和负输出端。
  13. 根据权利要求7或10所述的装置，其特征在于，当多个所述光伏单元先并联再与一个所述保护开关串联时，多个光伏单元的正输出端并联后与一个所述保护开关串联，或多个光伏单元的负输出端并联后与另一个所述保护开关串联。
  14. 根据权利要求7或10所述的装置，其特征在于，当多个所述光伏单元先并联再与两个所述保护开关串联时，多个光伏单元的正输出端并联后与一个所述保护开关串联，且多个光伏单元的负输出端并联后与另一个所述保护开关串联。
  15. 根据权利要求2-14所述的装置，其特征在于，所述控制器，具体用于当存在支路的电流的绝对值大于所述直流母线的电流的绝对值时，确定存在支路的反向电流大于所述第一电流值。
  16. 根据权利要求15所述的装置，其特征在于，所述装置还包括：第一电流传感器和第二电流传感器；
    所述第一电流传感器用于获取所述直流母线的电流的绝对值并发送至所述控制器；
    所述第二电流传感器用于获取预设支路的电流的绝对值并发送至所述控制器。
  17. 根据权利要求16所述的装置，其特征在于，所述装置还包括：功率电路；
    所述功率电路为直流-直流DC-DC变换电路或直流-交流DC-AC变换电路。
  18. 根据权利要求17所述的装置，其特征在于，所述装置还包括：第一电压传感器和直流开关；
    所述直流母线通过所述直流开关连接所述功率电路的输入端；
    所述第一电压传感器用于获取所述直流母线的电压的绝对值并发送至所述控制器。
  19. 根据权利要求2-14中任意一项所述的装置，其特征在于，所述控制器，具体用于当存在支路的电流方向与预设电流方向相反时，确定存在支路的反向电流大于所述第一电流值。
  20. 根据权利要求19所述的装置，其特征在于，所述装置还包括：第三电流传感器和第四电流传感器；
    所述第三电流传感器用于获取第一检测点的电流检测方向并发送至所述控制器，所述第一检测点位于任意一个支路；
    所述第四电流传感器用于获取第二检测点的电流检测方向并发送至所述控制器，除第一检测点所在支路外的其它所有支路汇集于所述第二检测点。
  21. 根据权利要求20所述的装置，其特征在于，所述控制器，具体用于当所述第一检测点的电流检测方向和第一检测点的预设电流方向相反，或第二检测点的电流检测方向和第二检测点的预设电流方向相反时，控制所述保护开关断开。
  22. 根据权利要求21所述的装置，其特征在于，还包括：功率电路；
    所述功率电路为直流-直流DC-DC变换电路或直流-交流DC-AC变换电路。
  23. 根据权利要求22所述的装置，其特征在于，所述装置还包括：第五电流传感器、第二电压传感器和直流开关；
    所述直流母线通过所述直流开关连接所述功率电路的输入端；
    所述第五电流传感器用于获取所述直流母线的电流的绝对值并发送至所述控制器；
    所述第二电压传感器用于获取所述直流母线的电压的绝对值并发送至所述控制器。
  24. 根据权利要求18或23所述的装置，其特征在于，所述控制器，还用于当所述直流母线的电流的绝对值大于第二电流值且所述直流母线的电压的绝对值小于第一电压值时，控制所述直流开关断开。
  25. 根据权利要求1所述的装置，其特征在于，所述控制器，具体用于当所述支路的参数检测值超过第一预设参数值范围，或当所述直流母线的参数检测值超过第二预设参数值范围时，确定所述光伏发电系统发生故障。
  26. 根据权利要求25所述的装置，其特征在于，所述参数检测值为以下中的至少一项：
    电压值、电流值、功率值或温度值。
  27. 根据权利要求1所述的装置，其特征在于，所述控制器，具体用于当所述直流母线的漏电流检测值大于第三电流值时，或存在所述支路的漏电流检测值大于第四电流值时，确定所述光伏发电系统发生故障。
  28. 根据权利要求1所述的装置，其特征在于，所述控制器，具体用于当根据所有所述支路的电流检测值确定存在支路出现电弧故障，或根据所述直流母线的电流检测值确定所述直流母线出现电弧故障时，确定所述光伏发电系统出现故障。
  29. 根据权利要求1所述的装置，其特征在于，所述控制器，还用于当确定存在支路出现电弧故障时，控制所述保护开关断开故障支路与所述直流母线的连接，或控制全部保护开关断开。
  30. 根据权利要求1-29中任一项所述的装置，其特征在于，所述控制器，还用于根据上位机发送的控制指令控制所述保护开关断开或闭合。
  31. 根据权利要求1-29中任一项所述的装置，其特征在于，至多三个所述光伏单元直接并联后连接一个所述接口，或至多三个所述光伏单元分别通过对应的所述接口后在所述装置内部并联。
  32. 根据权利要求1-29中任意一项所述的装置，其特征在于，当所述光伏单元和保护单元串联或者并联后通过所述接口连接所述装置时，所述保护开关，还用于在断开时使所述保护单元不触发保护动作。
  33. 根据权利要求32所述的装置，其特征在于，所述保护单元至少包括以下中的一项：
    熔断器、优化器和关断盒。
  34. 根据权利要求1-33中任一项所述的装置，其特征在于，所述保护开关为旋转式直流隔离开关或直流断路器。
  35. 根据权利要求34所述的装置，其特征在于，所述控制器，还用于当确定故障排除后或经过预设时间后控制所述保护开关闭合。
  36. 根据权利要求1-35中任一项所述的装置，其特征在于，所述装置还包括功率变换 器，部分或全部所述光伏单元通过所述功率变换器与所述直流母线耦合。
  37. 根据权利要求1-34中任一项所述的装置，其特征在于，所述装置还包括直流/直流变换器；
    所述直流母线连接所述直流/直流变换器的输入端，所述直流/直流变换器的输出端为所述光伏发电系统的保护装置的输出端；
    所述直流/直流变换器，用于将从所述直流母线获取的直流电进行直流变换后输出。
  38. 根据权利要求1-34中任一项所述的装置，其特征在于，所述装置还包括直流/交流变换器，
    所述直流母线连接所述直流/交流变换器的输入端，所述直流/交流变换器的输出端为所述光伏发电系统的保护装置的输出端；
    所述直流/交流变换器，用于将从所述直流母线获取的直流电转换为交流电后输出。
  39. 一种光伏发电系统的保护方法，其特征在于，应用于光伏发电系统的保护装置，所述保护装置通过接口连接至少两个光伏单元，所述至少两个光伏单元在所述装置内部与直流母线耦合以形成至少两个支路，每个所述支路至少连接一个所述光伏单元；所述保护开关，用于断开全部或部分所述光伏单元与所述直流母线的连接，使至多三个所述光伏单元直接并联，所述方法包括：
    根据所述支路或直流母线的参数检测值确定所述光伏发电系统发生故障时，控制所述保护开关断开。
  40. 根据权利要求39所述的方法，其特征在于，所述参数检测值为反向电流值，所述根据所述支路或直流母线的参数检测值确定所述光伏发电系统发生故障，具体包括：
    当存在支路的反向电流值大于第一电流值时，确定所述光伏发电系统存在故障。
  41. 根据权利要求40所述的方法，其特征在于，所述装置还包括功率电路，所述直流母线通过直流开关连接所述功率电路的输入端，所述方法还包括：
    当所述直流母线的电流的绝对值大于第二电流值且所述直流母线的电压的绝对值小于第一电压值时，控制所述直流开关断开。
  42. 根据权利要求39所述的方法，其特征在于，所述参数检测值为电压值、电流值、功率值或温度值中的至少一项，所述根据所述支路或直流母线的参数检测值确定所述光伏发电系统发生故障，具体包括：
    当所述支路的参数检测值超过第一预设参数值范围，或当所述直流母线的参数检测值超过第二预设参数值范围时，确定所述光伏发电系统发生故障。
  43. 根据权利要求39所述的方法，其特征在于，所述根据所述支路或直流母线的参数检测值确定所述光伏发电系统发生故障，具体包括：
    当所述直流母线的漏电流检测值大于第三电流值时，或存在所述支路的漏电流检测值大于第四电流值时，确定所述光伏发电系统发生故障。
  44. 根据权利要求39所述的方法，其特征在于，所述根据所述支路或直流母线的参数检测值确定所述光伏发电系统发生故障，具体包括：
    当根据所有所述支路的电流检测值确定存在支路出现电弧故障，或根据所述直流母线 的电流检测值确定所述直流母线出现电弧故障时，确定所述光伏发电系统出现故障。
  45. 一种光伏发电系统，其特征在于，包括至少两个光伏单元和权利要求1-32中任一项所述的保护装置，每个所述光伏单元包括一个或多个光伏组件；
    所述光伏组件，用于利用光能产生直流电。
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