WO2022141526A1 - 一种光伏发电系统、光伏逆变器及直流汇流箱 - Google Patents

一种光伏发电系统、光伏逆变器及直流汇流箱 Download PDF

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Publication number
WO2022141526A1
WO2022141526A1 PCT/CN2020/142425 CN2020142425W WO2022141526A1 WO 2022141526 A1 WO2022141526 A1 WO 2022141526A1 CN 2020142425 W CN2020142425 W CN 2020142425W WO 2022141526 A1 WO2022141526 A1 WO 2022141526A1
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WO
WIPO (PCT)
Prior art keywords
photovoltaic
converter
unit
trip unit
circuit
Prior art date
Application number
PCT/CN2020/142425
Other languages
English (en)
French (fr)
Inventor
张秀锋
张彦忠
Original Assignee
华为数字能源技术有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 华为数字能源技术有限公司 filed Critical 华为数字能源技术有限公司
Priority to JP2022554303A priority Critical patent/JP2023517215A/ja
Priority to KR1020237025832A priority patent/KR20230124078A/ko
Priority to PCT/CN2020/142425 priority patent/WO2022141526A1/zh
Priority to CN202211095925.XA priority patent/CN116316417A/zh
Priority to AU2020483594A priority patent/AU2020483594A1/en
Priority to CN202080012263.8A priority patent/CN113508506B/zh
Priority to EP20967864.8A priority patent/EP4084326A4/en
Publication of WO2022141526A1 publication Critical patent/WO2022141526A1/zh
Priority to US17/875,823 priority patent/US20220368126A1/en

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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
    • H02H7/20—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for electronic equipment
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • 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
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • 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
    • H02S40/34—Electrical components comprising specially adapted electrical connection means to be structurally associated with the PV module, e.g. junction boxes
    • 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
    • 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

  • the present application relates to the technical field of photovoltaic power generation, and in particular, to a photovoltaic power generation system, a photovoltaic inverter and a DC combiner box.
  • Photovoltaic power generation is a technology that uses the photovoltaic effect of the semiconductor interface to convert light energy into electrical energy.
  • a photovoltaic power generation system may generally include photovoltaic units, inverters, AC power distribution equipment, and the like. 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, the photovoltaic unit will be connected to a device with an independent Maximum Power Point Tracking (MPPT) function 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 the short circuit of one photovoltaic unit or the short circuit of the line where the photovoltaic unit is located. At this time, the short-circuit current is the sum of the output currents of the connected photovoltaic units. When the number of connected photovoltaic units is only 1, the short circuit The current is small, and the photovoltaic cells and lines can withstand this short-circuit current. However, when the number of photovoltaic units connected to other circuits is 2 or more, the short-circuit current is relatively large.
  • a fuse can be connected in series with the positive output end or the negative output end of the photovoltaic unit. Fused 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, the sum of the short-circuit currents of the multiple photovoltaic cells may not reach the fusing current of the fuse, which makes the fuse blowing take a long time, resulting in fusing.
  • the device cannot effectively protect the photovoltaic units and lines.
  • the application provides a photovoltaic power generation system, a photovoltaic inverter and a DC combiner box, which can effectively protect the photovoltaic unit and the line when the photovoltaic unit is short-circuited or the line is short-circuited.
  • the present application provides a photovoltaic power generation system
  • the photovoltaic power generation system includes a protection switch and a multi-channel direct current (Direct Current, DC)-DC converter.
  • Each DC-DC converter includes a DC bus, a DC-DC circuit and at least one input interface; the input interface is used to connect a photovoltaic unit, and the photovoltaic unit includes at least one photovoltaic module; the input interface is connected to the DC bus through a protection switch, and the DC bus is connected to the DC -The input end of the DC circuit, and the output end of the DC-DC circuit is the output end of the DC-DC converter.
  • the protection switch consists of a trip unit and a switching mechanism connected in series. The trip unit is used to control the switch mechanism to disconnect when there is a short-circuit fault in the line where it is located.
  • the trip unit controls the switch mechanism to disconnect, so that the interface is disconnected from the DC bus, and the photovoltaic unit connected to this interface is disconnected from the DC bus. Therefore, the photovoltaic units connected to other interfaces are disconnected.
  • the unit will not output current to the line where the photovoltaic unit has a short-circuit fault, thereby protecting the photovoltaic unit and the line from damage.
  • the protection action is triggered based on the release control switch mechanism, no additional control circuit is required, and the realization difficulty of the scheme is reduced.
  • the Y wire harness originally used for built-in fuses does not need to be arranged at the lower part of the PV inverter or the DC combiner box of the PV power generation system, but can be arranged on the side of the PV unit, thereby reducing the cost of electricity. cable cost.
  • the trip unit is an electromagnetic trip unit
  • the trip unit is an electromagnetic trip unit
  • the switch mechanism when the reverse current of the line where the trip unit is located is greater than the first current value, the switch mechanism is controlled to disconnect.
  • the first current value is related to an electrical parameter of the electromagnetic release.
  • the trip unit is an electromagnetic trip unit
  • the trip unit is an electromagnetic trip unit
  • the trip unit is an electromagnetic trip unit.
  • the trip unit is a thermal trip unit
  • the trip unit is a thermal trip unit
  • the switch mechanism when there is an overcurrent in the circuit where the trip unit is located, the switch mechanism is controlled to disconnect.
  • the bimetal thermal release when there is an overcurrent in the line where it is located, the bimetal heats up, thereby driving the switch mechanism to act.
  • each input interface is connected to a photovoltaic unit.
  • each photovoltaic unit can withstand the current input by one or two other photovoltaic units.
  • each photovoltaic unit can withstand the current input by two other photovoltaic units at most.
  • the photovoltaic power generation system further includes a DC-AC (Alternating Current, AC) circuit, and the DC-AC converter and the multi-channel DC-DC converter form an inverter.
  • the positive output port of the multi-channel DC-DC converter is connected in parallel with the positive input port of the DC-AC converter
  • the negative output port of the multi-channel DC-DC converter is connected in parallel with the negative input port of the DC-AC converter
  • the output port of the inverter is the output port of the inverter.
  • the multiple DC-DC converters form a DC combiner box
  • the positive output ports of the multiple DC-DC converters are connected in parallel to form the positive output port of the DC combiner box
  • the multiple DC-DC converters are connected in parallel to form a positive output port of the DC combiner box.
  • the negative output ports of the converters are connected in parallel to form the negative output ports of the DC combiner box.
  • the photovoltaic power generation system further includes a protector.
  • the protector is connected in series or in parallel with the photovoltaic unit.
  • the release is also used to prevent the protector from triggering the protective action when the control switch mechanism is disconnected.
  • the protector includes at least one of a fuse, an optimizer and a shutdown box.
  • the present application also provides a photovoltaic inverter for connecting a photovoltaic unit, the photovoltaic unit includes at least one photovoltaic component, and the photovoltaic inverter includes a protection switch, a DC-AC converter and a multi-channel DC-DC converter device.
  • Each DC-DC converter includes a DC bus, a DC-DC circuit and at least one input interface. The input interface is used to connect the photovoltaic unit, and the photovoltaic unit includes at least one photovoltaic assembly.
  • the input interface is connected to the DC bus through the protection switch, the DC bus is connected to the input end of the DC-DC circuit, and the output end of the DC-DC circuit is the output end of the DC-DC converter.
  • the protection switch consists of a trip unit and a switching mechanism connected in series.
  • the trip unit is used to control the switch mechanism to disconnect when there is a short-circuit fault in the line where it is located.
  • the trip unit controls the switch mechanism to disconnect, so that the interface is disconnected from the DC bus, and the photovoltaic unit connected to this interface is disconnected from the DC bus, so other interfaces are connected.
  • the photovoltaic unit will not output current to the line where the photovoltaic unit with short-circuit fault is located, thereby protecting the photovoltaic unit and the line from damage.
  • the protection action is triggered based on the release control switch mechanism, no additional control circuit is required, and the realization difficulty of the scheme is reduced.
  • the Y wire harness originally used for built-in fuses does not need to be arranged at the lower part of the photovoltaic inverter of the photovoltaic power generation system, but can be arranged on the photovoltaic unit side, thereby reducing the cable cost.
  • the release is an electromagnetic release, and when the reverse current of the line where the release is located is greater than the first current value, the switch mechanism is controlled to disconnect.
  • the trip unit is an electromagnetic trip unit, and when there is an overcurrent in the circuit where the trip unit is located, the switch mechanism is controlled to disconnect.
  • the trip unit is a thermal trip unit, and when the circuit where the trip unit is located has an overcurrent, the switch mechanism is controlled to disconnect.
  • the present application also provides a DC combiner box for connecting a photovoltaic unit, the photovoltaic unit includes at least one photovoltaic component, and the DC combiner box includes: a protection switch and a multi-channel DC-DC converter.
  • Each DC-DC converter includes a DC bus, a DC-DC circuit and at least one input interface. The input interface is used to connect the photovoltaic unit, and the photovoltaic unit includes at least one photovoltaic assembly.
  • the input interface is connected to the DC bus through the protection switch, the DC bus is connected to the input end of the DC-DC circuit, and the output end of the DC-DC circuit is the output end of the DC-DC converter.
  • the positive port of the output end of the multi-channel DC-DC converter is connected in parallel with the positive output port of the DC combiner box; the negative port of the output end of the multi-channel DC-DC converter is connected in parallel with the negative output port of the DC combiner box.
  • the protection switch consists of a trip unit and a switching mechanism connected in series. The trip unit is used to control the switch mechanism to disconnect when there is a short-circuit fault in the line where it is located.
  • the trip unit controls the switch mechanism to disconnect, so that the interface is disconnected from the DC bus, and the photovoltaic unit connected to this interface is disconnected from the DC bus, so other interfaces are connected.
  • the photovoltaic unit will not output current to the line where the photovoltaic unit has a short-circuit fault, thereby protecting the photovoltaic unit and the line from damage.
  • the protection action is triggered based on the release control switch mechanism, no additional control circuit is required, and the realization difficulty of the scheme is reduced.
  • the Y wire harness used for built-in fuses does not need to be arranged at the lower part of the DC combiner box of the photovoltaic power generation system, but can be arranged on the photovoltaic unit side, thereby reducing the cable cost.
  • the release is an electromagnetic release, and when the reverse current of the line where the release is located is greater than the first current value, the switch mechanism is controlled to be disconnected.
  • the trip unit is an electromagnetic trip unit, and when the circuit where the trip unit is located has an overcurrent, the switch mechanism is controlled to disconnect.
  • the release is a thermal release, and when there is an overcurrent in the line where the release is located, the switch mechanism is controlled to disconnect.
  • FIG. 1 is a schematic diagram one of a short-circuit protection circuit adopted in the prior art
  • FIG. 2 is a schematic diagram 2 of a short-circuit protection circuit adopted in the prior art
  • FIG. 3 is a schematic diagram three of a short-circuit protection circuit adopted in the prior art
  • FIG. 4 is a schematic diagram of a branch provided by an embodiment of the present application.
  • FIG. 5 is a schematic diagram of another branch provided by an embodiment of the present application.
  • FIG. 6 is a schematic diagram of a photovoltaic power generation system provided by an embodiment of the present application.
  • FIG. 7 is a schematic diagram of another photovoltaic power generation system provided by an embodiment of the present application.
  • FIG. 8 is a schematic diagram of yet another photovoltaic power generation system provided by an embodiment of the present application.
  • FIG. 9 is a schematic diagram of still another photovoltaic power generation system provided by an embodiment of the present application.
  • FIG. 10 is a schematic diagram of another photovoltaic power generation system provided by an embodiment of the application.
  • FIG. 11 is a schematic diagram of yet another photovoltaic power generation system provided by an embodiment of the application.
  • FIG. 12 is a schematic diagram of still another photovoltaic power generation system provided by an embodiment of the application.
  • FIG. 13 is a schematic diagram of another photovoltaic power generation system provided by an embodiment of the application.
  • FIG. 14 is a schematic diagram of yet another photovoltaic power generation system provided by an embodiment of the application.
  • 15 is a schematic diagram of still another photovoltaic power generation system provided by an embodiment of the application.
  • 16 is a schematic diagram of another photovoltaic power generation system provided by an embodiment of the application.
  • FIG. 17 is a schematic diagram of yet another photovoltaic power generation system provided by an embodiment of the application.
  • FIG. 18 is a schematic diagram of still another photovoltaic power generation system provided by an embodiment of the application.
  • FIG. 19 is a schematic diagram of another photovoltaic power generation system provided by an embodiment of the application.
  • FIG. 20 is a schematic diagram of yet another photovoltaic power generation system provided by an embodiment of the present application.
  • 21 is a schematic diagram of still another photovoltaic power generation system provided by an embodiment of the application.
  • FIG. 22 is a schematic diagram of a photovoltaic inverter provided by an embodiment of the application.
  • FIG. 23 is a schematic diagram of a DC combiner box provided by an embodiment of the present 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 is connected. Or connect a fuse (or fuse) in series at the negative output.
  • a fuse or fuse
  • Figure 1 is a schematic diagram when both the positive output terminal and the negative output terminal of the photovoltaic unit are 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 a photovoltaic unit The negative output terminal is fused in series Schematic diagram of the device.
  • Each branch includes a photovoltaic module 101 , and the three branches are connected in parallel before the switch 102 , and then connected to the MPPT device 103 through the DC switch 102 .
  • fuse1-fuse6 in Figure 1 fuse1-fuse3 in Figure 2, and fuse1-fuse3 in Figure 3 are fuses, which are blown when the current in the line is too large to protect the photovoltaic modules and lines.
  • the present application provides a photovoltaic power generation system, photovoltaic inverter and DC combiner box, which can effectively protect photovoltaic cells and lines when photovoltaic cells are short-circuited or lines are short-circuited.
  • the single-channel photovoltaic unit in the following embodiments may include one photovoltaic module, or may be formed by multiple photovoltaic modules in series and parallel, for example, multiple photovoltaic modules are first connected in series to form a photovoltaic string, and multiple photovoltaic strings are then connected in parallel to form photovoltaic unit.
  • the embodiments of the present application do not specifically limit the specific number of photovoltaic components included in the photovoltaic unit, which can be set by those skilled in the art according to actual needs, and the electrical parameters of a single photovoltaic component are not specifically limited in the embodiments of the present application.
  • the output voltages of the multi-channel photovoltaic units connected to the same channel of DC-DC converters may be the same or different, which are not specifically limited in the embodiments of the present application.
  • the DC-DC converter of the photovoltaic power generation system provided in the embodiment of the present application can be connected to at least two photovoltaic units through the interface. After the photovoltaic units are connected through the interface, the DC bus can be connected in parallel inside the DC-DC converter, so as to The output current of the photovoltaic unit is collected on the DC bus to form a branch circuit, and the existence form of the branch circuit is specifically described below.
  • this figure is a schematic diagram of a branch provided by an embodiment of the present application.
  • the branch circuit includes a photovoltaic unit 101a1, the positive output terminal of the photovoltaic unit 101a1 is the positive output terminal of the branch circuit, and the negative output terminal of the photovoltaic unit 101a1 is the negative output terminal of the branch circuit. Distinguish again.
  • this figure is a schematic diagram of another branch provided by an embodiment of the present application.
  • the branch circuit may include a plurality of branch circuits shown in FIG. 4 , thus including at least two photovoltaic units, such as 101a1, 101a2, . . . 101ai in sequence.
  • the branch circuit in the embodiment of the present application is a concept in the electrical field, and refers to the route through which the branch current flowing into the DC bus passes.
  • the circuit where the photovoltaic unit 101a1 is located can be called a circuit.
  • a branch circuit, a circuit formed after the photovoltaic unit 101a1 and the photovoltaic unit 101a1 are connected in parallel may also be referred to as a branch circuit.
  • the positive output terminals of each photovoltaic unit are collected to form the positive output terminal of the branch, and the negative output terminals of each photovoltaic unit are collected to form the negative output terminal of the branch.
  • the “branch” in the following embodiments specifically refers to the general term of all the branches shown in FIG. 4 and the branches shown in FIG. 5 . That is, the general term for all other branches except the main circuit (DC bus).
  • the photovoltaic power generation system includes one channel of DC-DC converters as an example for description.
  • the photovoltaic power generation system includes multiple channels of DC-DC converters, the principle is similar, and details are not repeated in this application.
  • FIG. 6 is a schematic diagram of a photovoltaic power generation system provided by an embodiment of the present application.
  • the photovoltaic power generation system includes: photovoltaic unit 101 , protection switches S 1 -SM +N and DC-DC converter 200 .
  • the DC-DC converter 200 includes an interface, a DC bus, and a DC-DC circuit 201 .
  • the DC-DC converter 200 can be connected to photovoltaic units through an interface, and the present application does not specifically limit the number of photovoltaic units connected to the same interface.
  • the multiple photovoltaic units When an interface is connected to multiple photovoltaic units, the multiple photovoltaic units are connected in parallel to form a branch as shown in FIG. 5 , and then connected to the interface.
  • Each photovoltaic unit includes at least one photovoltaic component.
  • Each protection switch includes a trip unit and switching mechanism connected in series.
  • the trip unit is used when a short circuit fault occurs in the line where it is located and the control switch mechanism is disconnected, that is, the protection switch is disconnected at this time, and the connection between the input interface of the line where the protection switch is located and the DC bus is disconnected, and a short circuit fault will occur at this time. line cut off.
  • FIG. 6 when a single-channel photovoltaic unit has a short-circuit fault, and the faulty photovoltaic unit can withstand the output current of one other normal photovoltaic unit, i in the figure takes the value of 2.
  • i is determined by the current withstand value of the actual photovoltaic unit, which is not specifically limited in this embodiment of the present application. It should be noted that the diagram shown in FIG. 6 is only for the convenience of drawing and description.
  • the i-channel photovoltaic units in the figure can be implemented in parallel inside the DC-DC converter 200, or can be connected in parallel with the interface connecting the DC bus externally.
  • the release is mechanically connected to the switch mechanism, and is used to release the holding mechanism when the protective action is triggered, so that the switch mechanism is automatically disconnected.
  • the principle of the trip unit is to control the switch mechanism to disconnect when a reverse current or overcurrent occurs in the branch where it is located, so as to realize the protection of photovoltaic units and lines.
  • the DC-DC circuit 201 may specifically be a boost (Boost) circuit, a buck (Buck) circuit, or a buck-boost (Buck-Boost) circuit.
  • Boost boost
  • Buck buck
  • Buck-Boost buck-boost
  • the trip unit controls the switch mechanism to disconnect, so that the interface is disconnected from the DC bus, and the photovoltaic unit connected to the interface is disconnected from the DC bus, so other
  • the photovoltaic unit connected to the interface will not output current to the line where the photovoltaic unit with the short-circuit fault is located, thereby protecting the photovoltaic unit and the line from damage.
  • the protection action is triggered based on the release control switch mechanism, no additional control circuit is required, and the realization difficulty of the scheme is reduced.
  • the Y wire harness originally used for built-in fuses does not need to be arranged at the lower part of the PV inverter or the DC combiner box of the PV power generation system, but can be arranged on the side of the PV unit, thereby reducing the cost of electricity. cable cost.
  • the release may have different implementations, for example: in some embodiments, the release is an electromagnetic release, and when the reverse current of the branch where the release is located is greater than the first current value, the switch mechanism is controlled to disconnect ; In some other embodiments, the trip unit is an electromagnetic trip unit, and when there is an overcurrent in the branch where the trip unit is located, the control switch mechanism is disconnected; in still other embodiments, the trip unit is a thermal trip When there is an overcurrent in the branch where the release is located, the control switch mechanism is disconnected.
  • this figure is a schematic diagram of another photovoltaic power generation system provided by the embodiment of the present application.
  • Each channel of DC-DC converter 200 is connected to two channels of photovoltaic units 101a1 and 101a2 through an interface.
  • the two photovoltaic units are connected to the interface of the DC-DC converter 200.
  • the DC-DC circuit 201 is connected through the DC switch 102.
  • the DC switch 102 is used to protect the circuit. In some embodiments You can also cancel the setting and short-circuit.
  • each photovoltaic unit is also connected in series with a protection switch S1.
  • the currents of the two photovoltaic units are merged into the DC bus, and the absolute value of the current of the DC bus (the absolute value of the detected current at point A or point B) is greater than the absolute value of the current in any branch (point C or point C or point B) The absolute value of the detection current of D).
  • the release can be an electromagnetic release, and when the reverse current of the branch where the release is located is greater than the first current value, the switch mechanism is controlled to disconnect.
  • 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 turned off to open the branch where the photovoltaic unit 101a1 is located, thereby protecting the photovoltaic unit and the circuit; when the branch where the photovoltaic unit 101a2 is located has a short-circuit fault, the protection switch S1 is turned off Opening the branch circuit where the photovoltaic unit 101a2 is located is disconnected, thereby protecting the photovoltaic unit and the line.
  • the protection switch may be connected in series with the positive output terminal of the photovoltaic unit, or may be connected in series with the negative output terminal of the photovoltaic unit, and a protection switch may be connected in series with both the positive output terminal and the negative output terminal of the photovoltaic unit to realize redundant
  • the remaining control is not specifically limited in this embodiment of the present application.
  • the photovoltaic unit 101a2 transmits current to the branch where the photovoltaic unit 101a1 is located, but the current is within the bearing range of the photovoltaic unit 101a1, so the photovoltaic unit 101a1 will not be damaged; when the photovoltaic unit 101a2 is short-circuited, the protection switch S2 is turned off to protect the circuit.
  • the switch mechanism of the photovoltaic power generation system disconnects the interface from the DC bus when it is disconnected, the photovoltaic unit connected to the interface is disconnected from the DC bus, so the photovoltaic units connected to other interfaces will not appear.
  • the line where the photovoltaic unit with short-circuit fault is located outputs current, thereby protecting the photovoltaic unit and line from damage.
  • the protection action is triggered based on the release control switch mechanism, no additional control circuit is required, and the realization difficulty of the scheme is reduced.
  • the Y wire harness originally used for built-in fuses does not need to be arranged at the lower part of the PV inverter or the DC combiner box of the PV power generation system, but can be arranged on the side of the PV unit, thereby reducing the cost of electricity. cable cost.
  • each DC-DC converter connected to the photovoltaic unit through two input interfaces as an example, but at present, in order to improve the DC ratio of the photovoltaic power generation system, each DC-DC converter is usually set with 3, 4 There are ... or even more input ports to connect photovoltaic units.
  • the following first describes the working principle when three input ports are set for each DC-DC converter.
  • FIG. 8 this figure is a schematic diagram of yet another photovoltaic power generation system provided by an embodiment of the present application.
  • the three-way photovoltaic units are respectively connected to the three input ports of the DC-DC converter. After the three-way photovoltaic units are respectively connected in series with a protection switch in the DC-DC converter, they are connected in parallel, and then connected to the DC-DC through the DC switch 102 .
  • the circuit 201 and the DC switch 102 are used to protect the circuit. In practical applications, the settings can also be canceled and short-circuited.
  • the photovoltaic unit 101a1 is connected in series with the protection switch S1
  • the photovoltaic unit 101a2 is connected in series with the protection switch S2
  • the photovoltaic unit 101a3 is connected in series with the protection switch S3.
  • the output current of the three-way photovoltaic unit is merged 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 point B) is greater than the absolute value of the current of any branch (point C).
  • the absolute value of the detection current at point D and point E at this time, the current direction of point C, point D and point E can be set as the preset current direction, for example, set as the positive direction.
  • the trip unit of S3 is a magnetic trip unit, and the trip unit controls the switch mechanism to disconnect when the reverse current flow of the branch where the photovoltaic unit 101a3 is located is greater than the first current value.
  • the trip unit of S2 is a magnetic trip unit, and the trip unit controls the switch mechanism to disconnect when there is an overcurrent in the branch where the photovoltaic unit 101a3 is located.
  • the trip unit is a thermal trip unit, and the trip unit controls the switch mechanism to disconnect when there is an overcurrent in the branch where the photovoltaic unit 101a3 is located.
  • One input interface can also connect two protection switches in series inside the DC-DC converter and then connect to the DC bus. At this time, the two protection switches can use different types of trip units respectively.
  • the photovoltaic unit 101a1 and the photovoltaic unit 101a2 can continue to work normally, thereby protecting the photovoltaic unit and the line.
  • each channel of DC-DC converter is provided with three input interfaces, and the principle when each channel of DC-DC converter is correspondingly provided with four input interfaces is described below.
  • this figure is a schematic diagram of yet another photovoltaic power generation system provided by an embodiment of the present application.
  • the four photovoltaic units are respectively connected to an input port of a DC-DC converter and then connected in series with the protection switch, and then connected to the DC-DC circuit 201 in parallel.
  • the positive output terminals of each photovoltaic unit are collected and connected to the protection switch S1, the negative output terminal of the photovoltaic unit 101a1 is connected to the protection switch S3, the negative output terminal of the photovoltaic unit 101a2 is connected to the protection switch S2, and the negative output terminal of the photovoltaic unit 101a3 is connected to the protection switch S2.
  • the switch S4, the negative output terminal of the photovoltaic unit 101a4 is connected to the protection switch S5.
  • the protection switch S1 in FIG. 9 can also be canceled and short-circuited.
  • the currents of the four-way photovoltaic units are merged into the DC bus, so the absolute value of the current of the DC bus (the absolute value of the detection point A or B) is greater than the absolute value of the current of any branch (detection point C). , D, E and F of the absolute value of the detection current).
  • the trip unit of the protection switch of the faulty branch controls the corresponding switch mechanism to disconnect, so that the faulty branch is disconnected, and other photovoltaic units can continue to work normally, thereby protecting the photovoltaic units and lines.
  • this figure is a schematic diagram of another photovoltaic power generation system provided by the embodiment of the present application.
  • the difference between the methods shown in FIG. 10 and FIG. 9 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 bus through the protection switch S1; the positive output terminal of the photovoltaic unit 101a3 The positive output terminal of the photovoltaic unit 101a4 is collected in the protection switch S6, and is connected to the positive DC bus through the protection switch S6.
  • FIG. 11 is a schematic diagram of yet another photovoltaic power generation system provided by an embodiment of the present application.
  • the trip unit controls the switch mechanism to disconnect, so that the interface is disconnected from the DC bus.
  • the photovoltaic unit connected to this interface is disconnected from the DC bus, so the photovoltaic unit connected to other interfaces will not output current to the line where the photovoltaic unit with short-circuit fault is located, thereby protecting the photovoltaic unit and the line from damage.
  • the protection action is triggered based on the release control switch mechanism, no additional control circuit is required, and the realization difficulty of the scheme is reduced.
  • the Y wire harness originally used for built-in fuses does not need to be arranged at the lower part of the PV inverter or the DC combiner box of the PV power generation system, but can be arranged on the side of the PV unit, thereby reducing the cost of electricity. cable cost.
  • this figure is a schematic diagram of still another photovoltaic power generation system provided by the embodiment of the present application.
  • the photovoltaic units 101a1 and 101a2 are connected in parallel inside the DC-DC converter and then connected to the DC bus of the DC-DC converter through a protection switch, and the branches where the photovoltaic units 101a3 and 101a4 are connected are connected in series with a protection switch respectively.
  • the positive output terminals of the photovoltaic units 101a1 and 101a2 are connected to the positive DC bus through the protection switch S1
  • 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 switch S2 can also be canceled and short-circuited.
  • the current of each branch is merged 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 trip unit can be an electromagnetic trip unit.
  • the trip unit of the protection switch of the faulty branch controls the corresponding switch mechanism to disconnect, so that the branch with short-circuit fault is disconnected, while other photovoltaic units can continue to work normally, and then Protect PV units and wiring.
  • this figure is a schematic diagram of another photovoltaic power generation system provided by the embodiment of the present application.
  • the difference between the implementation shown in FIG. 13 and FIG. 12 is that 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 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.
  • this figure is a schematic diagram of yet another photovoltaic power generation system provided by an embodiment of the present application.
  • the difference between the implementation shown in FIG. 14 and FIG. 13 is that the photovoltaic units 101a1 and 101a2 are connected in parallel, 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 through the protection 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 through the protection switch S1, and 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, The negative output terminal is connected to the negative DC bus through the protection switch S4.
  • this figure is a schematic diagram of still another photovoltaic power generation system provided by the embodiment of the present application.
  • the photovoltaic units 101a1 and 101a2 are directly connected in parallel inside the DC-DC converter, 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 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 DC-DC converter, 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 is merged 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 trip unit can be an electromagnetic trip unit.
  • the trip unit of the protection switch of the faulty branch controls the corresponding switch mechanism to disconnect, so that the branch with short-circuit fault is disconnected, while other photovoltaic units can continue to work normally, and then Protect PV units and wiring.
  • At least one of the protection switches S1 and S2 may be de-set and short-circuited, or at least one of the protection switches S3 and S4 may be de-set and short-circuited, or any of the protection switches S1 and S2 may be de-set and short-circuited.
  • One and any one of the protection switches S3 and S4 are canceled and short-circuited, thereby reducing the number of protection switches connected in series to reduce costs.
  • each channel of DC-DC converter includes three input interfaces and four input interfaces.
  • each channel of DC-DC converter can also be connected to more channels of photovoltaic units correspondingly , the working principle when the number of photovoltaic units connected to each channel of DC-DC converter is greater than 4 channels will be specifically described below.
  • FIG. 16 this figure is a schematic diagram of another photovoltaic power generation system provided by the embodiment of the present application.
  • the DC-DC converter is provided with M input interfaces to connect photovoltaic units, each interface is connected to a photovoltaic unit to form M branches of the first type photovoltaic unit.
  • M is an integer greater than or equal to 3.
  • 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 for redundant protection.
  • the M photovoltaic units are respectively connected in series with a protection switch and then connected in parallel to the DC bus of the DC-DC converter.
  • the currents of all photovoltaic units are merged into the DC bus, and 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 in any branch.
  • the trip unit of the faulty branch controls the corresponding switch mechanism to disconnect, so that the faulty branch is disconnected, and other photovoltaic units can continue to work normally.
  • this figure is a schematic diagram of yet another photovoltaic power generation system provided by an embodiment of the present application.
  • each i photovoltaic unit is directly connected in parallel inside the DC-DC converter. Then, connect at least one protection switch in series with the DC bus of the DC-DC converter, and N is an integer greater than or equal to 2.
  • this figure is a schematic diagram of still another photovoltaic power generation system provided by the embodiment of the present application.
  • the M photovoltaic units are connected to the DC bus after being connected in series with at least one switch in the DC-DC converter.
  • the i-channel photovoltaic unit is directly connected in parallel inside the DC-DC converter, and then at least one protection switch is connected in series to the DC bus of the DC-DC converter, and N is an integer greater than or equal to 2.
  • FIG. 19 is a schematic diagram of another photovoltaic power generation system provided by the embodiment of the present application.
  • the DC-DC converter supports the connection of the photovoltaic unit and the protector in series or in parallel.
  • the protector may also be in series with the photovoltaic unit.
  • the protector Q may be a combination of one or more of a fuse, an optimizer, and a shutdown box, and may also be other circuit devices that can protect the circuit when a short circuit fault occurs, which is not specifically limited in this embodiment of the present application.
  • k in the figure may be determined according to the actual situation, which is not specifically limited in this embodiment of the present application.
  • the release is also used to prevent the protector from triggering the protection action when the control switch mechanism is disconnected, that is, when the current photovoltaic power generation system using the protector is retrofitted, it is not necessary to remove the protector, and it can be directly connected to the DC- DC converter.
  • FIG. 20 this figure is a schematic diagram of yet another photovoltaic power generation system provided by an embodiment of the present application.
  • the illustrated photovoltaic power generation system includes X-channel DC-DC converters 200, and further includes a DC-AC converter 300.
  • the DC-AC converter may also be referred to as an inverter.
  • the DC-AC converter and the multi-channel DC-DC converter form an inverter 20, which is a string inverter.
  • the positive output port of the X-channel DC-DC converter 200 is connected in parallel with the positive input port of the DC-AC converter 300
  • the negative output port of the X-channel DC-DC converter 200 is connected in parallel with the negative input port of the DC-AC converter 300 .
  • the AC power output by the inverter 20 is collected after passing through the AC combiner box or the switch box, and then connected to the AC power grid after being transformed by the transformer.
  • this figure is a schematic diagram of still another photovoltaic power generation system provided by the embodiment of the present application.
  • the X-channel DC-DC converters 200 included in the photovoltaic power generation system form a DC combiner box 30, and the positive output ports of the X-channel DC-DC converters 200 are connected in parallel to form the positive output port of the DC combiner box 30; - The negative output ports of the DC converters 200 are connected in parallel to form the negative output ports of the DC combiner box 30 .
  • the DC combiner box 30 is an MPPT boost combiner box, and the positive output terminal and the negative output terminal of the DC combiner box 30 are respectively connected to the positive input terminal and the negative input terminal of the centralized inverter.
  • the centralized inverter is used to convert the single-channel or multi-channel parallel-connected DC input connected to the DC side into an AC output, generally using DC-AC single-stage power conversion.
  • the AC power output by the centralized inverter is fed into the AC power grid through the transformer.
  • the embodiments of the present application further provide a photovoltaic inverter, which will be described in detail below with reference to the accompanying drawings.
  • this figure is a schematic diagram of a photovoltaic inverter provided by an embodiment of the present application.
  • the illustrated photovoltaic inverter 20 includes: a protection switch (not shown in the figure), a DC-AC converter 300 and a multi-channel DC-DC converter 200 .
  • each DC-DC converter 200 is connected to at least two photovoltaic units 101 , and each photovoltaic unit includes at least one photovoltaic component.
  • Each DC-DC converter 200 includes a DC bus, a DC-DC circuit and at least one input interface.
  • Each input interface includes a positive input interface and a negative input interface.
  • the input interface is used to connect the photovoltaic unit, the positive input interface is connected to the positive DC bus inside the photovoltaic inverter 20, and the negative input interface is connected to the negative DC bus inside the photovoltaic inverter.
  • the positive output port of the multi-channel DC-DC converter 200 is connected in parallel with the positive input port of the DC-AC converter 300
  • the negative output port of the multi-channel DC-DC converter 200 is connected in parallel with the negative input port of the DC-AC converter 300 .
  • the protection switch includes a trip unit and a switch mechanism.
  • the trip unit is used to control the switch mechanism to disconnect when there is a short circuit fault in the line where it is located.
  • the release is an electromagnetic release, and when the reverse current of the branch where the release is located is greater than the first current value, the switch mechanism is controlled to disconnect.
  • the release is an electromagnetic release, and when the branch where the release is located has an overcurrent, the switch mechanism is controlled to disconnect.
  • the release is a thermal release, and when the branch where the release is located has an overcurrent, the switch mechanism is controlled to disconnect.
  • the trip unit controls the switch mechanism to disconnect, so that the interface is disconnected from the DC bus, and the photovoltaic unit connected to this interface is disconnected from the DC bus, so other interfaces are connected.
  • the photovoltaic unit will not output current to the line where the photovoltaic unit has a short-circuit fault, thereby protecting the photovoltaic unit and the line from damage.
  • the protection action is triggered based on the release control switch mechanism, no additional control circuit is required, and the realization difficulty of the scheme is reduced.
  • the Y wire harness originally used for built-in fuses does not need to be arranged at the lower part of the photovoltaic inverter of the photovoltaic power generation system, but can be arranged on the photovoltaic unit side, thereby reducing the cable cost.
  • the embodiment of the present application further provides a DC combiner box, which will be described in detail below with reference to the accompanying drawings.
  • this figure is a schematic diagram of a DC combiner box provided by an embodiment of the present application.
  • the DC combiner box 30 includes: a protection switch (not shown in the figure) and a multi-channel DC-DC converter 200 .
  • each DC-DC converter is connected to at least two photovoltaic units 101, and each photovoltaic unit includes at least one photovoltaic component.
  • Each DC-DC converter includes a DC bus, a DC-DC circuit and at least one input interface.
  • the input interface includes a positive input interface and a negative input interface.
  • the input interface is used to connect the photovoltaic unit, the positive input interface is connected to the positive DC bus inside the DC combiner box 30 , and the negative input interface is connected to the negative DC bus inside the DC combiner box 30 .
  • the positive output ports of the multiple DC-DC converters 200 are connected in parallel to form the positive output port of the DC combiner box 30
  • the negative output ports of the multiple DC-DC converters 200 are connected in parallel to form the negative output port of the DC combiner box 30 .
  • the protection switch includes a trip unit and a switch mechanism.
  • the trip unit is used to control the switch mechanism to disconnect when there is a short circuit fault in the line where it is located.
  • the release is an electromagnetic release, and when the reverse current of the branch where the release is located is greater than the first current value, the switch mechanism is controlled to disconnect.
  • the release is an electromagnetic release, and when the branch where the release is located has an overcurrent, the switch mechanism is controlled to disconnect.
  • the release is a thermal release, and when the branch where the release is located has an overcurrent, the switch mechanism is controlled to disconnect.
  • At least one of the positive input interface or the negative input interface of each group of input interfaces is connected in series with a protection switch inside the DC combiner box 30.
  • the trip unit controls the switch mechanism to disconnect, so that the interface is disconnected from the DC bus, and the photovoltaic unit connected to this interface is disconnected from the DC bus. Therefore, the photovoltaic units connected to other interfaces are disconnected.
  • the unit will not output current to the line where the photovoltaic unit has a short-circuit fault, thereby protecting the photovoltaic unit and the line from damage.
  • the protection action is triggered based on the release control switch mechanism, no additional control circuit is required, and the realization difficulty of the scheme is reduced.
  • the Y wire harness used for built-in fuses does not need to be arranged at the lower part of the DC combiner box of the photovoltaic power generation system, but can be arranged on the photovoltaic unit side, thereby reducing the cable cost.
  • At least one (item) refers to one or more, and "a plurality” refers to two or more.
  • “And/or” is used to describe the relationship between related objects, indicating that there can be three kinds of relationships, for example, “A and/or B” can mean: only A, only B, and both A and B exist , where A and B can be singular or plural.
  • the character “/” generally indicates that the associated objects are an “or” relationship.
  • At least one item(s) below” or similar expressions thereof refer to any combination of these items, including any combination of single item(s) or plural items(s).
  • At least one (a) of a, b or c can mean: a, b, c, "a and b", “a and c", “b and c", or "a and b and c" ", where a, b, c can be single or multiple.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Photovoltaic Devices (AREA)
  • Emergency Protection Circuit Devices (AREA)
  • Protection Of Static Devices (AREA)
  • Supply And Distribution Of Alternating Current (AREA)
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Abstract

一种光伏发电系统、光伏逆变器（20）及直流汇流箱（30），涉及光伏发电技术领域。其中，光伏发电系统包括保护开关（S1-S M+N）和多路DC-DC变换器（200）。每路DC-DC变换器（200）包括直流母线、DC-DC电路（201）和至少一个输入接口；输入接口用于连接光伏单元（101），光伏单元（101）包括至少一个光伏组件；输入接口通过保护开关（S1-S M+N）连接直流母线，直流母线连接DC-DC电路（201）的输入端，DC-DC电路（201）的输出端为DC-DC变换器（200）的输出端；保护开关（S1-S M+N）包括串联连接的脱扣器和开关机构。脱扣器用于当所在线路存在短路故障时控制所述开关机构断开。利用该光伏发电系统，能够在光伏单元（101）出现短路或者线路出现短路时有效保护光伏单元（101）和线路。

Description

一种光伏发电系统、光伏逆变器及直流汇流箱 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、光伏逆变器及直流汇流箱。
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最大功率点跟踪(Maximum Power Point Tracking，MPPT)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(光伏单元的功率与光伏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可能难以达到熔断器熔断电流，使得熔断器熔断耗时长，导致熔断器并不能有效的保护光伏单元和线路。
发明内容
本申请提供了一种光伏发电系统、光伏逆变器及直流汇流箱，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。
第一方面，本申请提供了一种光伏发电系统，该光伏发电系统包括保护开关和多路直流(Direct Current，DC)-直流变换器。每路DC-DC变换器包括直流母线、DC-DC电路和至少一个输入接口；输入接口用于连接光伏单元，光伏单元包括至少一个光伏组件；输入接口通过保护开关连接直流母线，直流母线连接DC-DC电路的输入端，DC-DC电路的输出端为DC-DC变换器的输出端。保护开关包括串联连接的脱扣器和开关机构。脱扣器用于当所在线路存在短路故障时控制开关机构断开。
该光伏发电系统当存在光伏单元出现短路故障时，脱扣器控制开关机构断开，使接口与直流母线断开连接，该接口连接的光伏单元与直流母线断开连接，因此其它接口连接的光伏单元不会向出现短路故障的光伏单元所在线路输出电流，进而保护光伏单元和线路不会损坏。基于脱扣器控制开关机构触发保护动作，不需要额外的控制电路，降低了方案的实现难度。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光伏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。
在一种可能的实现方式中，脱扣器为电磁脱扣器，脱扣器为电磁脱扣器，脱扣器当所在线路的反向电流大于第一电流值时，控制开关机构断开。第一电流值与电磁脱扣器的电参数相关。
在一种可能的实现方式中，脱扣器为电磁脱扣器，脱扣器为电磁脱扣器，脱扣器为电磁脱扣器，所述脱扣器当所在线路的存在过流时，控制开关机构断开。
在一种可能的实现方式中，脱扣器为热脱扣器，脱扣器为热脱扣器，脱扣器当所在线路存在过流时，控制开关机构断开。例如对于双金属片热脱扣器，当所在线路存在过流时，双金属片发热，从而驱动开关机构动作。
在一种可能的实现方式中，每个输入接口与一个光伏单元连接。
在一种可能的实现方式中，至多两路光伏单元先并联，然后连接输入接口。此时，每路光伏单元可以承受一路或两路其他路光伏单元输入的电流。
在一种可能的实现方式中，至多三路所述光伏单元先并联，然后连接输入接口。此时，每路光伏单元最多可以承受两路其他路光伏单元输入的电流。
在一种可能的实现方式中，光伏发电系统还包括直流-交流(Alternating Current，AC)电路，DC-AC变换器与多路DC-DC变换器形成逆变器。多路DC-DC变换器的正输出端口并联连接DC-AC变换器的正输入端口，多路DC-DC变换器的负输出端口并联连接DC-AC变换器的负输入端口，DC-AC变换器的输出端口为逆变器的输出端口。
在一种可能的实现方式中，所述多路DC-DC变换器形成直流汇流箱，多路DC-DC变换器的正输出端口并联以形成直流汇流箱的正输出端口，多路DC-DC变换器的负输出端口并联以形成直流汇流箱的负输出端口。
在一种可能的实现方式中，光伏发电系统还包括保护器。保护器与光伏单元串联或并联。脱扣器还用于在控制开关机构断开时使保护器不触发保护动作。
即对于目前采用保护器的光伏发电系统进行改造时，可以无需对保护器进行拆除处理，以便于改造。
在一种可能的实现方式中，保护器至少包括熔断器、优化器和关断盒中的一项。
第二方面，本申请还提供了一种光伏逆变器，用于连接光伏单元，光伏单元包括至少一个光伏组件，光伏逆变器包括保护开关、DC-AC变换器和多路DC-DC变换器。每路DC-DC变换器包括直流母线、DC-DC电路和至少一个输入接口。输入接口用于连接光伏单元，光伏单元包括至少一个光伏组件。输入接口通过保护开关连接直流母线，直流母线连接DC-DC电路的输入端，DC-DC电路的输出端为DC-DC变换器的输出端。多路DC-DC变换器的输出端的正端口并联连接DC-AC变换器的正输入端口，多路DC-DC变换器的输出端的负端口并联连接DC-AC变换器的负输入端口。保护开关包括串联连接的脱扣器和开关机构。脱扣器用于当所在线路存在短路故障时控制开关机构断开。
该光伏逆变器当连接的光伏单元出现短路故障时，脱扣器控制开关机构断开，使接口与直流母线断开连接，该接口连接的光伏单元与直流母线断开连接，因此其它接口连接的光伏单元不会向出现短路故障的光伏单元所在线路输出电流，进而保护光伏单元和线路不会损坏。基于脱扣器控制开关机构触发保护动作，不需要额外的控制电路，降低了方案 的实现难度。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光伏逆变器的下部，而可以配置在光伏单元侧，从而还降低了电缆成本。
结合第二方面，在一种可能的实现方式中，脱扣器为电磁脱扣器，脱扣器当所在线路的反向电流大于第一电流值时，控制开关机构断开。
结合第二方面，在一种可能的实现方式中，脱扣器为电磁脱扣器，脱扣器当所在线路存在过流时，控制开关机构断开。
结合第二方面，在一种可能的实现方式中，脱扣器为热脱扣器，脱扣器当所在线路存在过流时，控制开关机构断开。
第三方面，本申请还提供了一种直流汇流箱，用于连接光伏单元，光伏单元包括至少一个光伏组件，直流汇流箱包括：保护开关和多路DC-DC变换器。每路DC-DC变换器包括直流母线、DC-DC电路和至少一个输入接口。输入接口用于连接光伏单元，光伏单元包括至少一个光伏组件。输入接口通过保护开关连接直流母线，直流母线连接DC-DC电路的输入端，DC-DC电路的输出端为DC-DC变换器的输出端。多路DC-DC变换器的输出端的正端口并联所述直流汇流箱的正输出端口；多路DC-DC变换器的输出端的负端口并联连接直流汇流箱的负输出端口。保护开关包括串联连接的脱扣器和开关机构。脱扣器用于当所在线路存在短路故障时控制开关机构断开。
该直流汇流箱当连接的光伏单元出现短路故障时，脱扣器控制开关机构断开，使接口与直流母线断开连接，该接口连接的光伏单元与直流母线断开连接，因此其它接口连接的光伏单元不会向出现短路故障的光伏单元所在线路输出电流，进而保护光伏单元和线路不会损坏。基于脱扣器控制开关机构触发保护动作，不需要额外的控制电路，降低了方案的实现难度。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。
结合第三方面，在一种可能的实现方式中，脱扣器为电磁脱扣器，脱扣器当所在线路的反向电流大于第一电流值时，控制开关机构断开。
结合第三方面，在一种可能的实现方式中，脱扣器为电磁脱扣器，脱扣器当所在线路存在过流时，控制开关机构断开。
结合第三方面，在一种可能的实现方式中，脱扣器为热脱扣器，脱扣器当所在线路存在过流时，控制开关机构断开。
附图说明
图1为现有技术采用的短路保护电路的示意图一；
图2为现有技术采用的短路保护电路的示意图二；
图3为现有技术采用的短路保护电路的示意图三；
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6为本申请实施例提供的一种光伏发电系统的示意图；
图7为本申请实施例提供的另一种光伏发电系统的示意图；
图8为本申请实施例提供的又一种光伏发电系统的示意图；
图9为本申请实施例提供的再一种光伏发电系统的示意图；
图10为本申请实施例提供的另一种光伏发电系统的示意图；
图11为本申请实施例提供的又一种光伏发电系统的示意图；
图12为本申请实施例提供的再一种光伏发电系统的示意图；
图13为本申请实施例提供的另一种光伏发电系统的示意图；
图14为本申请实施例提供的又一种光伏发电系统的示意图；
图15为本申请实施例提供的再一种光伏发电系统的示意图；
图16为本申请实施例提供的另一种光伏发电系统的示意图；
图17为本申请实施例提供的又一种光伏发电系统的示意图；
图18为本申请实施例提供的再一种光伏发电系统的示意图；
图19为本申请实施例提供的另一种光伏发电系统的示意图；
图20为本申请实施例提供的又一种光伏发电系统的示意图；
图21为本申请实施例提供的再一种光伏发电系统的示意图；
图22为本申请实施例提供的一种光伏逆变器的示意图；
图23为本申请实施例提供的一种直流汇流箱的示意图。
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快速熔断。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快速熔断所需电流，因此熔断器可能不会熔断或需要较长的时间才能熔断，导致并不能有效的保护光伏单元和线路。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DC-DC变换器侧，而DC-DC变换器可能的光伏单元通过较长的电缆连接，进而还导致了电缆成本上升。
为了解决上述技术问题，本申请提供了一种光伏发电系统、光伏逆变器及直流汇流箱，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，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。
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。
以下实施例中的单路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。
连接同一路DC-DC变换器的多路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光伏发电系统的DC-DC变换器，能够通过接口接入至少两路光伏单元，光伏单元通过接口接入后，能够在DC-DC变换器的内部并联连接直流母线，以将光伏单元的输出电流汇集于直流母线，进而形成支路，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，该支路包括一路光伏单元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，因此包括了至少两路光伏单元，例如依次为101a1、101a2、…101ai。
可以理解的是，本申请实施例中的支路是电学领域的概念，指汇入直流母线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。
下面以光伏发电系统包括一路DC-DC变换器为例进行说明，当光伏发电系统包括多路DC-DC变换器时的原理类似，本申请不再赘述。
参见图6，该图为本申请实施例提供的一种光伏发电系统的示意图。
光伏发电系统包括：光伏单元101、保护开关S 1-S M+N和DC-DC变换器200。
其中，DC-DC变换器200包括接口、直流母线和DC-DC电路201。
DC-DC变换器200可以通过接口连接光伏单元，本申请对接入同一个接口的光伏单元的数量不作具体限定。
当一个接口连接多个光伏单元时，多个光伏单元并联形成图5所示的支路后，再与该接口连接。
每个光伏单元包括至少一个光伏组件。
每个保护开关包括串联连接的脱扣器和开关机构。脱扣器用于当所在线路出现短路故障时，控制开关机构断开时，即此时保护开关断开，保护开关所在线路的输入接口与直流母线之间的连接断开，此时将出现短路故障的线路切除。
以图6为例，当单路光伏单元出现短路故障，且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，图中的i取值为2。
又例如，当单路光伏单元出现短路故障，且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，图中的i取值为3。
i的具体取值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路光伏单元可以在DC-DC变换器200内部实现并联，也可以在外部先并联在连接直流母线的接口。
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。
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，并且存在短路故障的支路出现反向电流，当M+N的值大于2时，存在短路故障的支路还存在过流。
脱扣器与开关机构机械相连，用于在触发保护动作时释放保持机构，以使开关机构自动断开。脱扣器的原理为：当所在支路出现反向电流或过流时控制开关机构断开，以实现对于光伏单元和线路的保护。
DC-DC电路201具体可以为升压(Boost)电路、降压(Buck)电路或升降压(Buck-Boost)电路。
综上所述，光伏发电系统当存在光伏单元出现短路故障时，脱扣器控制开关机构断开，使接口与直流母线断开连接，该接口连接的光伏单元与直流母线断开连接，因此其它接口连接的光伏单元不会向出现短路故障的光伏单元所在线路输出电流，进而保护光伏单元和线路不会损坏。基于脱扣器控制开关机构触发保护动作，不需要额外的控制电路，降低了方案的实现难度。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光伏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。
脱扣器可以有不同的实现方式，例如：在一些实施例中，脱扣器为电磁脱扣器，脱扣器当所在支路的反向电流大于第一电流值时，控制开关机构断开；在另一些实施例中，脱扣器为电磁脱扣器，脱扣器当所在支路的存在过流时，控制开关机构断开；在又一些实施例中，脱扣器为热脱扣器，脱扣器当所在支路存在过流时，控制开关机构断开。
下面具体说明光伏发电系统的实现方式。
下面首先以DC-DC变换器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光伏发电系统的示意图。
每路DC-DC变换器200通过接口接入两路光伏单元101a1和101a2。
两路光伏单元接入DC-DC变换器200的接口，在DC-DC变换器200的内部并联后通 过直流开关102连接DC-DC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，每路光伏单元还串联有保护开关S1。
当无短路故障时，两路光伏单元的电流汇入直流母线，直流母线的电流绝对值(点A或点B的检测电流的绝对值)大于任意支路的电流的绝对值(点C或点D的检测电流的绝对值)。
当存在一路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，导致出现短路故障的光伏单元所在的支路出现反向电流。
此时脱扣器可以采用电磁脱扣器，脱扣器当所在支路的反向电流大于第一电流值时，控制开关机构断开。
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101a1所在支路断路，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断开使得光伏单元101a2所在的支路断路，进而保护了光伏单元和线路。
在一些实施例中，保护开关可以与光伏单元的正输出端串联，也可以与光伏单元的负输出端串联，还可以在光伏单元的正输出端和负输出端均串联一路保护开关以实现冗余控制，本申请实施例对此不作具体限定。
在另一些实施例中，当一路DC-DC电路仅连接两路光伏单元时，也可以仅取消设置S1或S2中的任意一个保护开关，例如当S1取消设置后，当光伏单元101a1短路时，光伏单元101a2向光伏单元101a1所在支路传输电流，但该电流在光伏单元101a1的承受范围内，因此光伏单元101a1不会损坏；当光伏单元101a2短路时，保护开关S2断开，以保护电路。
综上所述，由于该光伏发电系统的开关机构在断开时使接口与直流母线断开连接，该接口连接的光伏单元与直流母线断开连接，因此其它接口连接的光伏单元不会向出现短路故障的光伏单元所在线路输出电流，进而保护光伏单元和线路不会损坏。基于脱扣器控制开关机构触发保护动作，不需要额外的控制电路，降低了方案的实现难度。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光伏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。
以上实施例以每路DC-DC变换器通过两个输入接口连接光伏单元为例说明，但目前为了提升光伏发电系统的直流配比，通常每路DC-DC变换器会设置有3个、4个…甚至更多个输入接口以连接光伏单元，下面首先说明每路DC-DC变换器设置三个输入接口时的工作原理。
参见图8，该图为本申请实施例提供的又一种光伏发电系统的示意图。
三路光伏单元分别连接DC-DC变换器的三个输入接口，三路光伏单元在DC-DC变换器的内分别与一个保护开关串联后，在并联连接，然后通过直流开关102连接DC-DC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。
其中，光伏单元101a1串联保护开关S1，光伏单元101a2串联保护开关S2，光伏单元101a3串联保护开关S3。
当无短路故障时，三路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(点A或点B的检测电流的绝对值)大于任意支路的电流的绝对值(点C、点D和点E的检测电流的绝对值)，此时可以将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。
当存在一路光伏单元出现短路故障时，不妨假设光伏单元101a3所在线路出现短路故障，且单个光伏单元只能承受1路其他支路传输的反向电流。
此时其它两路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101a3，使得光伏单元101a3所在支路出现过流，并且出现反向电流(E点电流方向相反)。
在一种可能的实现方式中，S3的脱扣器为磁脱扣器，脱扣器当光伏单元101a3所在支路的反向电流流大于第一电流值时，控制开关机构断开。
在另一种可能的实现方式中，S2的脱扣器为磁脱扣器，脱扣器当光伏单元101a3所在支路存在过流时，控制开关机构断开。
在又一种可能的实现方式中，脱扣器为热脱扣器，脱扣器当光伏单元101a3所在支路存在过流时，控制开关机构断开。
一个输入接口在DC-DC变换器内部也可以串联两个保护开关后再连接直流母线，此时两个保护开关可以分别采用不同类型的脱扣器。
当S3断开后，光伏单元101a1和光伏单元101a2可以继续正常工作，进而保护了光伏单元与线路。
以上实施例以每路DC-DC变换器设置三个输入接口为例进行说明，下面说明每路DC-DC变换器对应设置四个输入接口时的原理。
参见图9，该图为本申请实施例提供的再一种光伏发电系统的示意图。
其中，4路光伏单元分别连接一个DC-DC变换器的输入端口后与保护开关进行串联，然后并联连接DC-DC电路201。
具体的，各光伏单元的正输出端汇集后连接保护开关S1，光伏单元101a1的负输出端连接保护开关S3，光伏单元101a2的负输出端连接保护开关S2，光伏单元101a3的负输出端连接保护开关S4，光伏单元101a4的负输出端连接保护开关S5。
在一些实施例中，图9中的保护开关S1也可以取消设置而短接。
当无短路故障时，四路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)。
当存在一路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，导致该故障支路出现过流以及反向电流。
继续以单个光伏单元只能承受1路其他支路反灌的电流为例。此时，该故障支路的保护开关的脱扣器控制对应的开关机构断开，使得故障支路断路，其他的光伏单元可以继续正常工作，进而保护了光伏单元与线路。
参见图10，该图为本申请实施例提供的另一种光伏发电系统的示意图。
图10与图9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。
此时原理与图9类似，本申请实施例在此不再赘述。
参见图11，该图为本申请实施例提供的又一种光伏发电系统的示意图。
图11与图9所示方式的区别在于：每路光伏单元的正输出端在DC-DC变换器的内部串联一个保护开关后汇集于正直流母线，每路光伏单元的负输出端在DC-DC变换器的内部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。具体原理与图9类似，本申请实施例在此不再赘述。
综上所述，当该光伏发电系统的DC-DC变换器通过接口连接4路光伏单元时，在存在支路出现短路故障时，脱扣器控制开关机构断开，使接口与直流母线断开连接，该接口连接的光伏单元与直流母线断开连接，因此其它接口连接的光伏单元不会向出现短路故障的光伏单元所在线路输出电流，进而保护光伏单元和线路不会损坏。基于脱扣器控制开关机构触发保护动作，不需要额外的控制电路，降低了方案的实现难度。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光伏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。
参见图12，该图为本申请实施例提供的再一种光伏发电系统的示意图。
其中，光伏单元101a1和101a2在DC-DC变换器的内部并联后通过保护开关接入所述DC-DC变换器的直流母线，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DC-DC变换器的直流母线。
具体的，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S2也可以取消设置而短接。
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，导致该存在短路故障的支路出现反向电流。
脱扣器可以采用电磁脱扣器，此时该故障支路的保护开关的脱扣器控制对应的开关机构断开，使得存在短路故障的支路断路，而其他光伏单元可以继续正常工作，进而保护光伏单元和线路。
结合图12的具体说明如下：
当光伏单元101a3所在支路出现短路故障时，S3断开，此时光伏单元101a3被切除，光伏单元101a1、101a2和101a4可以正常工作；
当光伏单元101a4所在支路出现短路故障时，S4断开，此时光伏单元101a4被切除，光伏单元101a1、101a2和101a3可以正常工作；
当光伏单元101a1所在支路出现短路故障时，S1和S2断开，此时光伏单元101a2输 入的电流在光伏单元101a1的耐受范围内，光伏单元101a3和101a4可以正常工作；
当光伏单元101a2所在支路出现短路故障时，S1和S2断开，此时光伏单元101a1输入的电流在光伏单元101a2的耐受范围内，光伏单元101a3和101a4可以正常工作。
参见图13，该图为本申请实施例提供的另一种光伏发电系统的示意图。
图13所示的实现方式与图12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。
工作原理与图12对应的说明类似，本申请实施例在此不再赘述。
参见图14，该图为本申请实施例提供的又一种光伏发电系统的示意图。
图14所示的实现方式与图13的区别在于：包括光伏单元101a1和101a2并联，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。
工作原理与图12对应的说明类似，本申请实施例在此不再赘述。
参见图15，该图为本申请实施例提供的再一种光伏发电系统的示意图。
其中，光伏单元101a1和101a2在DC-DC变换器内部直接并联，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DC-DC变换器内部直接并联，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。
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，导致该存在短路故障的支路出现反向电流。
脱扣器可以采用电磁脱扣器，此时该故障支路的保护开关的脱扣器控制对应的开关机构断开，使得存在短路故障的支路断路，而其他光伏单元可以继续正常工作，进而保护光伏单元和线路。
结合图15的具体说明如下：
当光伏单元101a1所在支路出现短路故障时，S1和S2断开，此时光伏单元101a2输入的电流在光伏单元101a1的耐受范围内，光伏单元101a3和101a4可以正常工作；
当光伏单元101a2所在支路出现短路故障时，S1和S2断开，此时光伏单元101a1输入的电流在光伏单元101a2的耐受范围内，光伏单元101a3和101a4可以正常工作
当光伏单元101a3所在支路出现短路故障时，S3和S4断开，此时光伏单元101a4输入的电流在光伏单元101a3的耐受范围内，光伏单元101a1和101a2可以正常工作；
当光伏单元101a4所在支路出现短路故障时，S3和S4断开，此时光伏单元101a3输 入的电流在光伏单元101a4的耐受范围内，光伏单元101a1和101a2可以正常工作。
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。
以上各实施例说明了每路DC-DC变换器包括三个输入接口以及四个输入接口时的工作原理，在一些实时例中，每路DC-DC变换器还可以对应连接更多路光伏单元，下面具体说明每路DC-DC变换器连接的光伏单元的数量大于4路时的工作原理。
参见图16，该图为本申请实施例提供的另一种光伏发电系统的示意图。
DC-DC变换器设置有M个输入接口以连接光伏单元，每个接口连接一个光伏单元以形成M个第一类光伏单元支路。其中，M为大于或等于3的整数。
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。
M路光伏单元分别串联一个保护开关后并联接入DC-DC变换器的直流母线。
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。
当存在一路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，导致该故障支路出现过流以及反向电流。
此时该故障支路的脱扣器控制对应的开关机构断开，以使故障支路断路，而其他光伏单元可以继续正常工作。
参见图17，该图为本申请实施例提供的又一种光伏发电系统的示意图。
其中，每i路光伏单元在DC-DC变换器的内部直接并联。然后通过串联至少一个保护开关后连接DC-DC变换器的直流母线，N为大于或等于2的整数。
单路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。
参见图18，该图为本申请实施例提供的再一种光伏发电系统的示意图。
其中，M路光伏单元在DC-DC变换器内与至少一个开关串联后接入直流母线。
i路光伏单元在DC-DC变换器的内部直接并联，再串联至少一个保护开关后接入DC-DC变换器的直流母线，N为大于或等于2的整数。
单路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。
还可以参见图19，该图为本申请实施例提供的另一种光伏发电系统的示意图。
其中，DC-DC变换器支持光伏单元和保护器串联或者并联后接入，图中以i路光伏单元依次间隔通过保护器并联为例进行说明。在一些实施例中，保护器也可以与光伏单元串 联。
保护器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。
此时脱扣器还用于在控制开关机构断开时使保护器不触发保护动作，即对于目前采用保护器的光伏发电系统进行改造时，可以无需对保护器进行拆除，可以直接入DC-DC变换器。
需要注意的是，单路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，为了不触发保护器的保护动作，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，为了不触发保护器的保护动作，i的取值为2或3。
参见图20，该图为本申请实施例提供的又一种光伏发电系统的示意图。
图示光伏发电系统包括X路DC-DC变换器200，还包括DC-AC变换器300，DC-AC变换器也可以称为逆变器。
DC-AC变换器与多路DC-DC变换器形成逆变器20，该逆变器为组串式逆变器。
X路DC-DC变换器200的正输出端口并联连接DC-AC变换器300的正输入端口，X路DC-DC变换器200的负输出端口并联连接DC-AC变换器300的负输入端口。
逆变器20输出的交流电经过交流汇流箱或开关盒后汇集，再通过变压器变压后接入交流电网。
参见图21，该图为本申请实施例提供的再一种光伏发电系统的示意图。
图示光伏发电系统包括的X路DC-DC变换器200形成直流汇流箱30，X路DC-DC变换器200的正输出端口并联以形成直流汇流箱30的正输出端口；X路多路DC-DC变换器200的负输出端口并联以形成直流汇流箱30的负输出端口。
在一些实施例中，直流汇流箱30为MPPT升压汇流箱，直流汇流箱30的正输出端和负输出端分别与集中式逆变器的正输入端和负输入端连接。
集中式逆变器用于将直流侧接入的单路或多路彼此并联的直流输入转换为交流输出，一般采用DC-AC单级功率变换。集中式逆变器输出的交流电经变压器后汇入交流电网。
基于以上实施例提供的光伏发电系统，本申请实施例还提供了一种光伏逆变器，下面结合附图具体说明。
参见图22，该图为本申请实施例提供的一种光伏逆变器的示意图。
图示光伏逆变器20包括：保护开关(图中未示出)、DC-AC变换器300和多路DC-DC变换器200。
每路DC-DC变换器200的输入端连接至少两路光伏单元101，每路光伏单元包括至少一个光伏组件。
每路DC-DC变换器200包括直流母线、DC-DC电路和至少一个输入接口。
每个输入接口包括正输入接口和负输入接口。
输入接口用于连接光伏单元，正输入接口在光伏逆变器20内部连接正直流母线，负输 入接口在光伏逆变器内部连接负直流母线。
多路DC-DC变换器200的正输出端口并联连接DC-AC变换器300的正输入端口，多路DC-DC变换器200的负输出端口并联连接DC-AC变换器300的负输入端口。
保护开关包括脱扣器和开关机构。其中，脱扣器用于当所在线路存在短路故障时控制所述开关机构断开。
在一种可能的实现方式中，脱扣器为电磁脱扣器，脱扣器当所在支路的反向电流大于第一电流值时，控制开关机构断开。
在另一种可能的实现方式中，脱扣器为电磁脱扣器，脱扣器当所在支路存在过流时，控制开关机构断开。
在又一种可能的实现方式中，脱扣器为热脱扣器，脱扣器当所在支路存在过流时，控制开关机构断开。
该光伏逆变器当存在光伏单元出现短路故障时，脱扣器控制开关机构断开，使接口与直流母线断开连接，该接口连接的光伏单元与直流母线断开连接，因此其它接口连接的光伏单元不会向出现短路故障的光伏单元所在线路输出电流，进而保护光伏单元和线路不会损坏。基于脱扣器控制开关机构触发保护动作，不需要额外的控制电路，降低了方案的实现难度。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光伏逆变器的下部，而可以配置在光伏单元侧，从而还降低了电缆成本。
基于以上实施例提供的光伏发电系统，本申请实施例还提供了一种直流汇流箱，下面结合附图具体说明。
参见图23，该图为本申请实施例提供的一种直流汇流箱的示意图。
直流汇流箱30包括：保护开关(图中未示出)和多路DC-DC变换器200。
每路DC-DC变换器的输入端连接至少两路光伏单元101，每路光伏单元包括至少一个光伏组件。
每路DC-DC变换器包括直流母线、DC-DC电路和至少一个输入接口。输入接口包括正输入接口和负输入接口。输入接口用于连接光伏单元，正输入接口在直流汇流箱30内部连接正直流母线，负输入接口在直流汇流箱30内部连接负直流母线。
多路DC-DC变换器200的正输出端口并联以形成直流汇流箱30的正输出端口，多路DC-DC变换器200的负输出端口并联以形成直流汇流箱30的负输出端口。
保护开关包括脱扣器和开关机构。其中，脱扣器用于当所在线路存在短路故障时控制所述开关机构断开。
在一种可能的实现方式中，脱扣器为电磁脱扣器，脱扣器当所在支路的反向电流大于第一电流值时，控制开关机构断开。
在另一种可能的实现方式中，脱扣器为电磁脱扣器，脱扣器当所在支路存在过流时，控制开关机构断开。
在又一种可能的实现方式中，脱扣器为热脱扣器，脱扣器当所在支路存在过流时，控制开关机构断开。
在一些实施例中，每组输入接口的正输入接口或负输入接口中的至少一个在直流汇流 箱30内部串联保护开关。
该直流汇流箱当存在光伏单元出现短路故障时，脱扣器控制开关机构断开，使接口与直流母线断开连接，该接口连接的光伏单元与直流母线断开连接，因此其它接口连接的光伏单元不会向出现短路故障的光伏单元所在线路输出电流，进而保护光伏单元和线路不会损坏。基于脱扣器控制开关机构触发保护动作，不需要额外的控制电路，降低了方案的实现难度。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。
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 (19)

  1. 一种光伏发电系统，其特征在于，所述光伏发电系统包括保护开关和多路DC-DC变换器；
    每路所述DC-DC变换器包括直流母线、DC-DC电路和至少一个输入接口；
    所述输入接口用于连接光伏单元，所述光伏单元包括至少一个光伏组件；
    所述输入接口通过至少一个所述保护开关连接所述直流母线，所述直流母线连接所述DC-DC电路的输入端，所述DC-DC电路的输出端为所述DC-DC变换器的输出端；
    所述保护开关包括串联连接的脱扣器和开关机构；
    所述脱扣器，用于当所在线路存在短路故障时控制所述开关机构断开。
  2. 根据权利要求1所述的光伏发电系统，其特征在于，所述脱扣器为电磁脱扣器，所述脱扣器当所在线路的反向电流大于第一电流值时，控制所述开关机构断开。
  3. 根据权利要求1所述的光伏发电系统，其特征在于，所述脱扣器为电磁脱扣器，所述脱扣器当所在线路的存在过流时，控制所述开关机构断开。
  4. 根据权利要求1所述的光伏发电系统，其特征在于，所述脱扣器为热脱扣器，所述脱扣器当所在线路存在过流时，控制所述开关机构断开。
  5. 根据权利要求1-4中任一项所述的光伏发电系统，其特征在于，每个所述输入接口与一个所述光伏单元连接。
  6. 根据权利要求1-4中任一项所述的光伏发电系统，其特征在于，至多两路所述光伏单元先并联，然后连接所述输入接口。
  7. 根据权利要求1-4中任一项所述的光伏发电系统，其特征在于，至多三路所述光伏单元先并联，然后连接所述输入接口。
  8. 根据权利要求1-7中任一项所述的光伏发电系统，其特征在于，所述光伏发电系统还包括DC-AC变换器，所述DC-AC变换器与所述多路DC-DC变换器形成逆变器；
    所述多路DC-DC变换器的正输出端口并联连接所述DC-AC变换器的正输入端口，所述多路DC-DC变换器的负输出端口并联连接所述DC-AC变换器的负输入端口。
  9. 根据权利要求1-7中任意一项所述的光伏发电系统，其特征在于，所述多路DC-DC变换器形成直流汇流箱；
    所述多路DC-DC变换器的正输出端口并联以形成所述直流汇流箱的正输出端口；
    所述多路DC-DC变换器的负输出端口并联以形成所述直流汇流箱的负输出端口。
  10. 根据权利要求1-9中任意一项所述的光伏发电系统，其特征在于，所述光伏发电系统还包括保护器；
    所述保护器与所述光伏单元串联或并联；
    所述脱扣器，还用于在控制所述开关机构断开时使所述保护器不触发保护动作。
  11. 根据权利要求10所述的光伏发电系统，其特征在于，所述保护器至少包括以下中的一项：
    熔断器、优化器和关断盒。
  12. 一种光伏逆变器，其特征在于，用于连接光伏单元，所述光伏单元包括至少一个 光伏组件，所述光伏逆变器包括：保护开关、DC-AC变换器和多路DC-DC变换器；
    每路所述DC-DC变换器包括直流母线、DC-DC电路和至少一个输入接口；
    所述输入接口用于连接光伏单元，所述光伏单元包括至少一个光伏组件；
    所述输入接口通过所述保护开关连接所述直流母线，所述直流母线连接所述DC-DC电路的输入端，所述DC-DC电路的输出端为所述DC-DC变换器的输出端；
    所述多路DC-DC变换器的输出端的正端口并联连接所述DC-AC变换器的正输入端口，所述多路DC-DC变换器的输出端的负端口并联连接所述DC-AC变换器的负输入端口；
    所述保护开关包括串联连接的脱扣器和开关机构；
    所述脱扣器，用于当所在线路存在短路故障时控制所述开关机构断开。
  13. 根据权利要求12所述的光伏逆变器，其特征在于，所述脱扣器为电磁脱扣器，所述脱扣器当所在线路的反向电流大于第一电流值时，控制所述开关机构断开。
  14. 根据权利要求12所述的光伏逆变器，其特征在于，所述脱扣器为电磁脱扣器，所述脱扣器当所在线路存在过流时，控制所述开关机构断开。
  15. 根据权利要求14所述的光伏逆变器，其特征在于，所述脱扣器为热脱扣器，所述脱扣器当所在线路存在过流时，控制所述开关机构断开。
  16. 一种直流汇流箱，其特征在于，用于连接光伏单元，所述光伏单元包括至少一个光伏组件，所述直流汇流箱包括：保护开关和多路DC-DC变换器；
    每路所述DC-DC变换器包括直流母线、DC-DC电路和至少一个输入接口；
    所述输入接口用于连接光伏单元，所述光伏单元包括至少一个光伏组件；
    所述输入接口通过所述保护开关连接所述直流母线，所述直流母线连接所述DC-DC电路的输入端，所述DC-DC电路的输出端为所述DC-DC变换器的输出端；
    所述多路DC-DC变换器的输出端的正端口并联连接所述直流汇流箱的正输出端口；
    所述多路DC-DC变换器的输出端的负端口并联连接所述直流汇流箱的负输出端口；
    所述保护开关包括串联连接的脱扣器和开关机构；
    所述脱扣器，用于当所在线路存在短路故障时控制所述开关机构断开。
  17. 根据权利要求16所述的直流汇流箱，其特征在于，所述脱扣器为电磁脱扣器，所述脱扣器当所在线路的反向电流大于第一电流值时，控制所述开关机构断开。
  18. 根据权利要求16所述的直流汇流箱，其特征在于，所述脱扣器为电磁脱扣器，所述脱扣器当所在线路存在过流时，控制所述开关机构断开。
  19. 根据权利要求16所述的直流汇流箱，其特征在于，所述脱扣器为热脱扣器，所述脱扣器当所在线路存在过流时，控制所述开关机构断开。
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