A photovoltaic system and control method

Abstract

The application discloses a photovoltaic system and a control method, comprising: at least two photovoltaic strings, a power taking circuit, a trip switch, a switching power supply and a controller; the at least two photovoltaic strings are connected in parallel; the trip switch is connected between the photovoltaic strings and an input end of a converter; the power taking circuit is used for taking power from at least one photovoltaic string to supply power to the switching power supply; the switching power supply is used for supplying power to the controller and the trip switch when the power taking circuit normally supplies power; and the controller is used for controlling the trip switch to be opened when there is a wiring fault in the at least two photovoltaic strings connected in parallel. The power taking circuit is specially arranged, the power taking circuit can directly take power from the photovoltaic string to supply power to the switching power supply. When the photovoltaic string connected with the power taking circuit is reversely connected, the switching power supply cannot work, the trip switch cannot be closed, and therefore the reversely connected photovoltaic string cannot be burnt.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy power generation, in particular to a photovoltaic system and a control method. BACKGROUND

[0002] With the continuous development of new energy, the application of photovoltaic power generation is becoming more and more widespread, and generally multiple photovoltaic strings are connected in parallel. Each photovoltaic string includes multiple photovoltaic modules connected in series, and each photovoltaic module includes multiple battery pieces connected in series. A reverse-parallel diode is connected between the output positive and negative poles of the photovoltaic module and the corresponding battery piece connection point.

[0003] When multiple photovoltaic strings are connected in parallel, if one or more strings are reversely connected, when the switch is closed, the current of the normally connected photovoltaic string will all flow into the reversely connected photovoltaic string. When the reversely connected photovoltaic string appears, the switching power supply of the photovoltaic system cannot work normally, so the switch cannot be opened by issuing a command. If the reverse current is large, the battery pieces will be damaged. SUMMARY

[0004] Therefore, the present application provides a photovoltaic system, a control method and a power supply system, which can prevent the reversely connected photovoltaic string from being burned out when the photovoltaic string is reversely connected.

[0005] The present application provides a photovoltaic system, comprising: at least two photovoltaic strings, a power taking circuit, a trip switch, a switching power supply and a controller.

[0006] The at least two photovoltaic strings are connected in parallel; the trip switch is connected between the photovoltaic string and the input end of the converter.

[0007] The power taking circuit is used to take power from at least one photovoltaic string to supply power to the switching power supply.

[0008] The switching power supply is used to supply power to the controller and the trip switch when the power taking circuit normally supplies power.

[0009] The controller is used to control the trip switch to be opened when there is a wiring fault in the at least two photovoltaic strings connected in parallel.

[0010] Preferably, the power taking circuit comprises a positive power taking circuit and / or a negative power taking circuit.

[0011] The positive power taking circuit is connected to the positive pole of at least one photovoltaic string, and the negative power taking circuit is connected to the negative pole of at least one photovoltaic string.

[0012] Preferably, the photovoltaic system further comprises a bidirectional rectifier circuit.

[0013] The bidirectional rectifier circuit is connected between the power taking circuit and the switching power supply.

[0014] The bidirectional rectifier circuit is used to rectify the output voltage and output current of the power taking circuit and provide the rectified voltage and current to the switching power supply.

[0015] Preferably, the bidirectional rectifier circuit comprises a first diode, a second diode, a third diode and a fourth diode.

[0016] The cathode of the first diode and the cathode of the second diode are connected to the positive terminal of the switching power supply, and the anode of the second diode and the anode of the first diode are connected to the positive power taking circuit and the negative power taking circuit respectively.

[0017] The cathode of the third diode and the cathode of the fourth diode are connected to the anode of the first diode and the anode of the second diode respectively, and the anode of the third diode and the anode of the fourth diode are connected to the negative terminal of the switching power supply.

[0018] Preferably, the bidirectional rectifier circuit further comprises a DCDC conversion circuit, a fifth diode and a sixth diode, the DCDC conversion circuit is connected between the trip switch and the switching power supply, the positive terminal of the DCDC conversion circuit is connected to the positive terminal of the switching power supply through the fifth diode, and the negative terminal of the DCDC conversion circuit is connected to the negative terminal of the switching power supply through the sixth diode.

[0019] Preferably, when the photovoltaic string is normal, the one with higher voltage in the power taking circuit and the DCDC conversion circuit supplies power to the switching power supply.

[0020] Preferably, the power taking circuit further comprises a maintenance switch.

[0021] The maintenance switch is connected between the photovoltaic string and the bidirectional rectifier circuit.

[0022] Or,

[0023] The maintenance switch is connected between the bidirectional rectifier circuit and the switching power supply.

[0024] Before the trip switch is closed, when the maintenance switch is open, the maintenance switch is closed first, and then the trip switch is closed.

[0025] Preferably, the bidirectional rectifier circuit further comprises a seventh diode and an eighth diode.

[0026] The seventh diode is connected between the positive terminal of the maintenance switch and the positive input terminal of the bidirectional rectifier circuit, and the eighth diode is connected between the negative terminal of the maintenance switch and the negative input terminal of the bidirectional rectifier circuit.

[0027] Preferably, the controller and the switching power supply are located inside the converter.

[0028] The application also provides a photovoltaic system, which comprises at least two sets of trip switches, i.e., a first trip switch and a second trip switch, each set of trip switches comprising a plurality of contacts, each contact being connected to a corresponding photovoltaic string.

[0029] The first trip switch connects the positive poles of all photovoltaic strings and the negative poles of part of the photovoltaic strings, and the second trip switch connects the negative poles of the rest of the photovoltaic strings.

[0030] Or,

[0031] The first trip switch connects the negative poles of all photovoltaic strings and the positive poles of part of the photovoltaic strings, and the second trip switch connects the positive poles of the rest of the photovoltaic strings.

[0032] The application also provides a photovoltaic system, which comprises a switching power supply, a converter and a trip switch, wherein the trip switch comprises a plurality of contacts, each of which is connected to a corresponding photovoltaic string.

[0033] A first end of the converter is connected to the photovoltaic strings through the trip switch, and a second end of the converter is connected to the switching power supply.

[0034] The trip switch is first connected to one photovoltaic string, and if the switching power supply is working normally, the trip switch is then connected to other photovoltaic strings; if the switching power supply is not working, the trip switch is not connected to other photovoltaic strings corresponding to the trip switch.

[0035] The application also provides a control method of a photovoltaic system, wherein the photovoltaic system comprises a converter, a power taking circuit, a trip switch and a switching power supply; an input end of the converter is connected to at least two photovoltaic strings connected in parallel through the trip switch; and the power taking circuit is used to take power from at least one photovoltaic string to supply power to the switching power supply.

[0036] The method comprises the following steps.

[0037] When the power taking circuit supplies power normally, the switching power supply supplies power to the trip switch.

[0038] The trip switch is closed, and when there is a wiring fault in the at least two photovoltaic strings connected in parallel, the trip switch is controlled to be opened.

[0039] Preferably, the photovoltaic system further comprises a maintenance switch connected between the power taking circuit and the switching power supply.

[0040] The method further comprises the following steps.

[0041] Before the trip switch is closed, the maintenance switch is closed first.

[0042] Preferably, the photovoltaic system further comprises a DCDC conversion circuit and a DCAC conversion circuit.

[0043] An input end of the DCDC conversion circuit is connected to the trip switch, and an output end of the DCDC conversion circuit is connected to the DCAC conversion circuit.

[0044] The method further comprises the following steps.

[0045] In case of a DC-AC conversion circuit failure, disconnect the maintenance switch.

[0046] This application also provides a control method for a photovoltaic system, the photovoltaic system including: the photovoltaic system includes at least two sets of trip switches: a first trip switch and a second trip switch, each set of trip switches including multiple contacts, each contact being connected to a corresponding photovoltaic string;

[0047] The method includes:

[0048] The first trip switch is connected to the positive terminal of all photovoltaic strings and the negative terminal of some photovoltaic strings, and the second trip switch is connected to the negative terminal of the remaining photovoltaic strings.

[0049] or,

[0050] The first trip switch is connected to the negative terminal of all photovoltaic strings and the positive terminal of some photovoltaic strings, while the second trip switch is connected to the positive terminal of the remaining photovoltaic strings.

[0051] This application also provides a control method for a photovoltaic system. The photovoltaic system includes: a switching power supply, a converter, and a trip switch. The trip switch includes multiple contacts, each of which is connected to a corresponding photovoltaic string. The first end of the converter is connected to the photovoltaic string through the trip switch, and the second end of the converter is connected to the switching power supply.

[0052] The method includes:

[0053] The trip switch is first connected to one photovoltaic string to determine that the switching power supply is working normally before connecting to other photovoltaic strings;

[0054] If the switching power supply is determined to be not working, then other photovoltaic strings corresponding to the trip switch will not be connected.

[0055] Therefore, this application has the following beneficial effects:

[0056] The photovoltaic system provided in this application has a dedicated power extraction circuit that can directly draw power from the photovoltaic strings to supply the switching power supply. When a photovoltaic string connected to the power extraction circuit is reverse-connected, the switching power supply will not operate; that is, the switching power supply will not supply power to the controller and the trip switch. Therefore, the trip switch will not close, and the reverse-connected photovoltaic string will not burn out. Conversely, when all photovoltaic strings connected to the power extraction circuit are functioning correctly and there is no reverse connection, the switching power supply can operate normally, supplying power to the trip switch and the controller, and the trip switch can close. If the switching power supply supplies power to the trip switch and the controller, and after the trip switch closes, if there is a wiring fault in the photovoltaic string connected to the trip switch, the controller can control the trip switch to open, thereby preventing the reverse-connected photovoltaic string from burning out. Attached Figure Description

[0057] Figure 1A schematic diagram of a photovoltaic system provided by the present application;

[0058] Figure 2 A schematic diagram of another photovoltaic system provided by the present application;

[0059] Figure 3 A schematic diagram of still another photovoltaic system provided by the present application;

[0060] Figure 4 A schematic diagram of yet another photovoltaic system provided by the present application;

[0061] Figure 5 A schematic diagram of still another photovoltaic system provided by the present application;

[0062] Figure 6 A schematic diagram of another photovoltaic system provided by the present application;

[0063] Figure 7 A schematic diagram of a connection of a photovoltaic string provided by the present application;

[0064] Figure 8 A schematic diagram of another connection of a photovoltaic string provided by the present application;

[0065] Figure 9 A flow chart of a control method of a photovoltaic system provided by the present application. DETAILED DESCRIPTION

[0066] In order to make the skilled in the art better understand the technical solutions provided by the present application, the application scenarios of the technical solutions provided by the present application are introduced first.

[0067] Referring to Figure 1 The figure is a schematic diagram of a photovoltaic system provided by the present application.

[0068] The photovoltaic system comprises, in addition to the photovoltaic string, a converter, a trip switch 100 and a switching power supply 200. Figure 1 The input end of the trip switch 100 is connected to n photovoltaic strings, for example. The n photovoltaic strings are connected in parallel. That is, PV1+, PV2+ to PVn+ are connected together, and PV1-, PV2- to PVn- are connected together.

[0069] The converter comprises a DCDC conversion circuit 300, for example. It should be understood that the converter can comprise a DCDC conversion circuit and a DCAC conversion circuit.

[0070] In order to cut off the connection between the photovoltaic string and the subsequent circuit in time when the photovoltaic system fails, a trip switch 100 is arranged between the DCDC conversion circuit 300 and the photovoltaic string. The trip switch 100 is also called a trip switch. The controller can control the trip switch 100 to be disconnected, but the trip switch 100 needs to be manually closed, and the controller cannot control the trip switch 100 to be closed.

[0071] The switching power supply 200 is used as an auxiliary power supply of the photovoltaic system, and is used to take power from the DCDC conversion circuit 300. The switching power supply 200 is used to supply power to the trip switch 100 and a control circuit (not shown in the figure). For example, the control circuit generally includes a controller.

[0072] The switching power supply 200 can be a switching power supply inside the inverter.

[0073] The output end of the DCDC conversion circuit 300 is connected with a capacitor C1.

[0074] The embodiment of the application does not specifically limit the specific topology and working principle of the DCDC conversion circuit 300.

[0075] The controller controls the trip switch 100 to be disconnected when the trip switch 100 exists in the photovoltaic string, thereby protecting the photovoltaic string. However, the power supply of the switching power supply 200 comes from the photovoltaic string when the photovoltaic system starts to work. Therefore, when there is a reverse connection string or other wiring fault in the photovoltaic string, the switching power supply 200 will not work. Therefore, the switching power supply 200 cannot supply power to the trip switch 100 and the controller, and the controller cannot control the trip switch 100 to be disconnected, and thus cannot achieve protection against reverse connection.

[0076] In order to solve the above technical problems, the application provides a photovoltaic system. A power taking circuit is added to directly take power from the photovoltaic string for the switching power supply, without passing through the trip switch. When the power taking circuit can normally take power, the switching power supply can normally work to supply power to the trip switch and the controller. After the trip switch is closed, the controller can control the trip switch to normally trip, that is, to be disconnected. When the power taking circuit cannot normally take power, the switching power supply cannot work to supply power to the trip switch and the controller. At this time, the trip switch is also not closed, and thus reverse connection protection can be achieved. That is, whether the photovoltaic string connected to the power taking circuit is reversely connected or not, the protection of the reversely connected photovoltaic string can be achieved. The effect is more obvious when the photovoltaic system includes three or more photovoltaic strings. That is, when there are at least three photovoltaic strings, the more reversely connected photovoltaic strings, the greater the reverse current, and the photovoltaic string is more likely to be burned out.

[0077] In order to make the above-mentioned purposes, features and advantages of the application more obvious and easy to understand, the embodiments of the application will be further described in detail below with reference to the drawings and specific embodiments.

[0078] Referring to Figure 2 Fig. 2 is a schematic diagram of another photovoltaic system according to an embodiment of the present application.

[0079] The photovoltaic system according to the embodiment comprises a converter, a power taking circuit, a trip switch 100, a switching power supply 200 and a controller (not shown in the figure).

[0080] For example, the converter comprises a DC-DC conversion circuit 300, and the power taking circuit comprises a positive power taking circuit 401 and / or a negative power taking circuit 402. The embodiment of the present application does not limit the specific implementation of the power taking circuit, which can comprise only one of the two or both. Hereinafter, the positive power taking circuit 401 and the negative power taking circuit 402 are taken as examples for introduction.

[0081] The positive power taking circuit 401 is connected to the positive poles of at least one photovoltaic string, and the negative power taking circuit 402 is connected to the negative poles of at least one photovoltaic string.

[0082] The input end of the converter is connected to at least two photovoltaic strings connected in parallel through the trip switch 100. Figure 2 For example, the input end of the trip switch 100 is connected to n photovoltaic strings. The n photovoltaic strings are connected in parallel. That is, PV1+, PV2+ to PVn+ are connected together, and PV1-, PV2- to PVn- are connected together.

[0083] The power taking circuit is used to take power from at least one photovoltaic string to supply power to the switching power supply 200. In the figure, the power taking circuit takes power from n photovoltaic strings, that is, the positive power taking circuit 401 is connected to PV1+, PV2+ and PVn+, and the negative power taking circuit 402 is connected to PV1-, PV2- and PVn-. It should be understood that, under the condition of meeting the voltage requirement, the power taking circuit can be selected to take power from only part of the photovoltaic strings.

[0084] In addition, the power taking circuit can supply power to the sampling circuit and the communication circuit in addition to supplying power to the controller and the trip switch.

[0085] The switching power supply 200 is used to supply power to the controller and the trip switch 100 when the power taking circuit is normally powered.

[0086] The controller is used to control the trip switch 100 to be disconnected when there is a wiring fault in at least two photovoltaic strings connected in parallel.

[0087] The wiring fault of the photovoltaic string at least includes reverse connection of the photovoltaic string, and can also include other wiring faults, such as short circuit.

[0088] The photovoltaic system provided in the embodiment is specially provided with a power taking circuit, the power taking circuit can directly take power from the photovoltaic string to supply power for the switching power supply, and the switching power supply supplies power for the controller and the trip switch 100.

[0089] When the photovoltaic string connected by the power taking circuit exists reverse connection, the switching power supply will not work, that is, the switching power supply will not supply power for the controller and the trip switch, therefore, the trip switch will not be closed, and thus the photovoltaic string in reverse connection will not be burnt. In addition, when the photovoltaic strings connected by the power taking circuit are all normal and do not exist reverse connection, the switching power supply can work normally to supply power for the trip switch and the controller, and the trip switch can be closed. If the switching power supply supplies power for the trip switch and the controller, and the trip switch is closed, and the photovoltaic string connected by the trip switch exists wiring fault, the controller can control the trip switch to be opened, and thus the photovoltaic string in reverse connection can be prevented from being burnt.

[0090] The controller is used for controlling the trip switch 100 to be opened when the photovoltaic string in reverse connection exists in the at least two photovoltaic strings connected in parallel. That is, as long as the trip switch 100 is closed, the controller can control the trip switch 100 to be tripped when the photovoltaic string in reverse connection exists.

[0091] If the switching power supply 200 cannot work normally, it indicates that the photovoltaic string exists reverse connection, the power taking circuit cannot normally supply power for the switching power supply 200, and the switching power supply 200 also cannot supply power for the controller and the trip switch 100, at this time, the trip switch 100 will not be closed, and thus the problem that the photovoltaic string in reverse connection is burnt can be avoided.

[0092] It should be understood that when the photovoltaic string is connected by the power taking circuit, if the connection of the photovoltaic string is normal, the switching power supply will work normally after a preset time period; if the photovoltaic string connected by the power taking circuit exists reverse connection, the switching power supply still cannot work normally after the preset time period.

[0093] The technical scheme provided in the embodiment of the application mainly aims at solving the problem that when the photovoltaic string is connected to the inverter for the first time, the switching power supply can normally supply power, and thus the controller can normally control the trip switch 100 to be opened when the photovoltaic string exists reverse connection, and thus the protection of the photovoltaic string in reverse connection can be realized to prevent the photovoltaic string from being burnt.

[0094] Another photovoltaic system will be introduced below in combination with the drawings, and a bidirectional rectifier circuit is added, and whether the photovoltaic string connected by the power taking circuit exists reverse connection or not, the switching power supply can be normally supplied with power.

[0095] Referring to Figure 3 The figure is a schematic diagram of still another photovoltaic system provided in the embodiment of the application.

[0096] The photovoltaic system provided in the embodiment further comprises a bidirectional rectifier circuit.

[0097] The bidirectional rectifier circuit is connected between the power taking circuit and the switching power supply 200.

[0098] The bidirectional rectifier circuit is used to rectify the output voltage and output current of the power taking circuit and provide them to the switching power supply 200.

[0099] In one possible implementation, the bidirectional rectifier circuit includes a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4.

[0100] The cathode of the second diode D2 and the cathode of the first diode D1 are both connected to the positive terminal of the switching power supply 200, and the anode of the second diode D2 and the anode of the first diode D1 are respectively connected to the positive power taking circuit 401 and the negative power taking circuit 402.

[0101] The cathode of the third diode D3 and the cathode of the fourth diode D4 are respectively connected to the anode of the first diode D1 and the anode of the second diode D2, and the anode of the third diode D3 and the anode of the fourth diode D4 are both connected to the negative terminal of the switching power supply 200.

[0102] It should be understood that the first diode D1, the second diode D2, the third diode D3, and the fourth diode D4 form a full-bridge rectifier bridge, and even if the photovoltaic module string connected to the power taking circuit is reversely connected, a reverse current can pass through the bidirectional rectifier circuit to supply power to the switching power supply 200. Thus, the switching power supply 200 can supply power to the trip switch 100 and the controller, and if the reversely connected photovoltaic module string exists, the controller can control the trip switch 100 to be disconnected, i.e., the trip switch 100 will trip, thereby protecting the reversely connected photovoltaic module string from being burned out.

[0103] In order to avoid the current output by the power taking circuit from being reversely fed to the DCDC conversion circuit 300, the photovoltaic system provided in the embodiment of the present application further includes a fifth diode D5 and a sixth diode D6, and the DCDC conversion circuit 300 is connected between the trip switch 100 and the switching power supply 200. The positive terminal of the DCDC conversion circuit 300 is connected to the positive terminal of the switching power supply 200 through the fifth diode D5, and the negative terminal of the DCDC conversion circuit 300 is connected to the negative terminal of the switching power supply 200 through the sixth diode D6.

[0104] It should be understood that, Figure 2 In the photovoltaic system shown, D5 and D6 can also be included, and the specific connection relationship is the same as that of D5 and D6 in the above embodiment, which will not be described herein again. Figure 3

[0105] In order to further ensure the safety of the photovoltaic system, the photovoltaic system provided in the embodiment of the present application further includes a maintenance switch. The following will be described in detail with reference to the accompanying drawings.

[0106] Referring to Figure 4 ​Fig. 6 is a schematic diagram of another photovoltaic system according to an embodiment of the present application.

[0107] The photovoltaic system provided by the embodiment further comprises a maintenance switch 500.

[0108] The maintenance switch 500 is connected between the power taking circuit and the bidirectional rectifier circuit, i.e., the positive input end of the maintenance switch 500 is connected to the positive power taking circuit 401, and the negative input end of the maintenance switch is connected to the negative power taking circuit 402. The positive output end of the maintenance switch 500 is connected to the positive input end of the bidirectional rectifier circuit, and the negative output end of the maintenance switch 500 is connected to the negative input end of the bidirectional rectifier circuit.

[0109] Before the trip switch 100 is closed, when the maintenance switch 500 is open, the maintenance switch 500 is closed first, and then the trip switch 100 is closed. If the maintenance switch 500 is closed before the trip switch 100 is closed, the trip switch 100 is directly closed. The maintenance switch 500 is a manual switch, which needs to be manually closed and opened.

[0110] The maintenance switch 500 is arranged on the path for supplying power to the switching power supply 200 by the power taking circuit. After the photovoltaic strings are connected, the maintenance switch 500 is closed first, and after a preset time period, if the switching power supply 200 is normal, the trip switch 100 is closed. After the trip switch 100 is closed, if the photovoltaic strings are reversely connected, the controller can control the trip switch 100 to normally trip.

[0111] When the DCAC conversion circuit at the rear stage needs to be maintained, the maintenance switch 500 can be manually opened to meet the requirements of safety regulations.

[0112] The embodiment of the present application does not specifically limit the implementation type of the maintenance switch 500, which can be a normally open switch or a normally closed switch.

[0113] In order to further prevent the reverse flow of current, two diodes can be further included between the maintenance switch 500 and the bidirectional rectifier circuit.

[0114] Referring to Fig. 6, Figure 5 Fig. 6 is a schematic diagram of another photovoltaic system according to an embodiment of the present application.

[0115] The photovoltaic system provided by the embodiment further comprises a seventh diode D7 and an eighth diode D8.

[0116] The seventh diode D7 is connected between the positive end of the maintenance switch 500 and the positive input end of the bidirectional rectifier circuit, and the eighth diode D8 is connected between the negative end of the maintenance switch 500 and the negative input end of the bidirectional rectifier circuit.

[0117] It should be understood that when the photovoltaic string is connected to the inverter for the first time, the switching power supply can take power from the photovoltaic string or from the DCDC conversion circuit 300. The specific power taking mode can adopt a voltage comparison mode. Due to the presence of D5 and D7, the side with higher voltage supplies power to the switching power supply 200. For example, if the output voltage of D7 is higher than that of D5, the photovoltaic string is used to supply power to the switching power supply 200. If the output voltage of D5 is higher than that of D7, the DCDC conversion circuit 300 is used to supply power to the switching power supply 200. Compared with the DCDC conversion circuit 300, the power supply of the photovoltaic string is more stable and is prone to fluctuate with the natural environment.

[0118] Figure 4 The photovoltaic system includes a bidirectional rectifier circuit and a maintenance switch. It should be understood that the photovoltaic system provided by the embodiments of the present application can also include a maintenance switch but does not include a bidirectional rectifier circuit. The following will be described with reference to the accompanying drawings.

[0119] It should be understood that the above Figure 4 and Figure 5 are described by taking the maintenance switch connected to the input end of the bidirectional rectifier circuit as an example. In addition, the maintenance switch can also be connected to the output end of the bidirectional rectifier circuit, that is, connected between the bidirectional rectifier circuit and the switching power supply.

[0120] Referring to Figure 6 , the figure is a schematic diagram of another photovoltaic system provided by the embodiments of the present application.

[0121] In the photovoltaic system provided by the embodiments of the present application, the maintenance switch 500 is connected between the power taking circuit and the switching power supply 200. That is, the positive input end of the maintenance switch 500 is connected to the positive power taking circuit 401, and the negative input end of the maintenance switch is connected to the negative power taking circuit 402. The positive output end of the maintenance switch 500 is connected to the positive end of the switching power supply 200, and the negative output end of the maintenance switch is connected to the negative end of the switching power supply 200.

[0122] The photovoltaic system provided by the above embodiments of the present application, wherein the switching power supply is not specifically limited in position, for example, can be located inside the inverter as a switching power supply in the inverter. Since the switching power supply can normally supply power and work, the reliability of the inverter working can be provided.

[0123] In addition to the above photovoltaic system which can avoid burning of the photovoltaic string, the embodiments of the present application also provide other implementation manners, which will be described below with reference to the accompanying drawings.

[0124] Referring to Figure 7 , the figure is a connection schematic diagram of a photovoltaic string provided by the embodiments of the present application.

[0125] The embodiment provides a photovoltaic system, the photovoltaic system comprises at least two sets of trip switches, a first trip switch and a second trip switch, each set of trip switches comprises a plurality of contacts, and each contact is connected to a corresponding photovoltaic string;

[0126] The first trip switch is connected to the positive poles of all photovoltaic strings and the negative poles of part of the photovoltaic strings, and the second trip switch is connected to the negative poles of the remaining photovoltaic strings;

[0127] Or,

[0128] The first trip switch is connected to the negative poles of all photovoltaic strings and the positive poles of part of the photovoltaic strings, and the second trip switch is connected to the positive poles of the remaining photovoltaic strings.

[0129] As shown in the figure, all positive poles of the photovoltaic strings and the negative poles of part of the photovoltaic strings are connected to one set of trip switches, and the negative poles of the remaining photovoltaic strings are connected to another set of trip switches. Figure 7

[0130] The single-path DCDC conversion circuit corresponds to n photovoltaic strings, wherein the positive and negative poles (PV1+, PV1-, PV2+, PV2-) of the photovoltaic string PV1 and the photovoltaic string PV2 are connected to the first set of trip switches 101, the positive poles of the remaining photovoltaic strings PV3-PVn are connected to the first set of trip switches 101, and the negative poles of the remaining photovoltaic strings PV3-PVn are connected to the second set of trip switches 102.

[0131] In the embodiment, the inverter comprises a DCDC conversion circuit 300 and a DCAC conversion circuit 600.

[0132] When all photovoltaic strings of the inverter are connected, the first set of trip switches 101 is closed first, for example, waiting for a preset time t, if the switching power supply of the inverter works, then the other switches are closed, if the switching power supply cannot work normally, it is indicated that PV1 or PV2 is reversely connected, since at most two photovoltaic strings are reversely connected, the reverse current is not too large, so as to not cause damage to the battery panel, and the remaining trip switches do not need to be closed.

[0133] In addition to the connection mode shown in the figure, the negative poles of all photovoltaic strings and the positive poles of part of the photovoltaic strings can be connected to the same set of trip switches, and the positive poles of the remaining photovoltaic strings are connected to another set of trip switches. Figure 7

[0134] Referring to the figure, the figure is another connection diagram of a photovoltaic string provided by the embodiment of the application. Figure 8

[0135] ​​​The single-path DCDC conversion circuit corresponds to n photovoltaic strings, wherein the positive and negative poles (PV1+, PV1-, PV2+, PV2-) of the photovoltaic string PV1 and the photovoltaic string PV2 are connected to the first set of trip switches 101, the negative poles of the remaining photovoltaic strings PV3-PVn are connected to the first set of trip switches 101, and the positive poles of the remaining photovoltaic strings PV3-PVn are connected to the second set of trip switches 102.

[0136] Figure 8 The connection mode shown can also protect the left and right sides, and since a large reverse connection current is not generated when reverse connection occurs, the photovoltaic strings are not burned.

[0137] In the prior art, the photovoltaic strings corresponding to the same DCDC conversion circuit are all connected to the same trip switch, and when one or more photovoltaic strings are reversely connected, the current of the normal photovoltaic strings will all flow into the reversely connected photovoltaic strings, which can damage the solar panels in the reversely connected photovoltaic strings.

[0138] In the embodiment, the positive and negative poles of one or two photovoltaic strings corresponding to the same DCDC conversion circuit are all connected to the first set of trip switches, and the other poles of the remaining photovoltaic strings are connected to the second set of trip switches, so that only one or two photovoltaic strings are connected to the inverter when the first set of trip switches is connected, and the reverse connection current of the one or two photovoltaic strings is not too large, and the reverse flow current in the reversely connected solar panels does not damage the solar panels, so that the photovoltaic strings are not burned.

[0139] In addition, the embodiment of the application also provides another scheme for avoiding burning of the photovoltaic strings due to reverse connection, which will be described in detail below.

[0140] The photovoltaic system provided in the embodiment includes a switching power supply, a converter, and trip switches, the trip switches include a plurality of contacts, and each contact is connected to a corresponding photovoltaic string.

[0141] A first end of the converter is connected to the photovoltaic strings through the trip switches, and a second end of the converter is connected to the switching power supply.

[0142] The trip switches are first connected to one photovoltaic string, and if the switching power supply is in normal operation, other photovoltaic strings are connected, and if the switching power supply is not in operation, other photovoltaic strings corresponding to the trip switches are not connected.

[0143] Since the reverse connection current of a single photovoltaic string is very small even if reverse connection exists, if the single photovoltaic string is in normal operation, the single photovoltaic string is used to supply power to the switching power supply, and if the single photovoltaic string is reversely connected, the single photovoltaic string does not supply power and other photovoltaic strings are not connected, so that the safety of the system is ensured.

[0144] Based on the photovoltaic system provided in the above embodiments, the embodiment of the present application further provides a control method of the photovoltaic system, which will be described in detail below with reference to the accompanying drawings.

[0145] Referring to Figure 9 The figure is a flow chart of a control method of a photovoltaic system provided by the embodiment of the present application.

[0146] The control method of the photovoltaic system provided by the embodiment includes: the photovoltaic system includes a converter, a power taking circuit, a trip switch and a switching power supply; the input end of the converter is connected to at least two photovoltaic strings in parallel through the trip switch; the power taking circuit is used to take power from at least one photovoltaic string to supply power to the switching power supply.

[0147] The method includes:

[0148] S701: when the power taking circuit normally supplies power, the switching power supply supplies power to the trip switch;

[0149] When the power taking circuit is connected to the photovoltaic string, if the connection of the photovoltaic string is normal, the switching power supply will work normally after a preset time period; if there is a reverse connection in the photovoltaic string connected by the power taking circuit, the switching power supply still cannot work normally after the preset time period. At this time, the trip switch will not be closed, and therefore the photovoltaic string will not be burned due to the reverse connection.

[0150] S702: control the trip switch to be closed; when there is a wiring fault in the at least two photovoltaic strings connected in parallel, control the trip switch to be opened.

[0151] That is, as long as the controller and the trip switch 100 are powered by the switching power supply, when the trip switch 100 is closed, the controller can control the trip switch 100 to trip, i.e., to be opened, when there is a reverse connection or other wiring fault in the photovoltaic string.

[0152] Since the photovoltaic system is specially provided with the power taking circuit, the power taking circuit can directly take power from the photovoltaic string to supply power to the switching power supply.

[0153] When the photovoltaic string connected by the power taking circuit has a reverse connection, the switching power supply will not work, i.e., the switching power supply will not supply power to the controller and the trip switch, and therefore the trip switch will not be closed, so that the photovoltaic string with the reverse connection will not be burned. In addition, when the photovoltaic strings connected by the power taking circuit are all normal and do not have a reverse connection, the switching power supply can work normally to supply power to the trip switch and the controller, and the trip switch can be closed. If the switching power supply supplies power to the trip switch and the controller, and the trip switch is closed after the trip switch is closed, the photovoltaic string connected by the trip switch has a wiring fault, and the trip switch can be controlled to be opened, so that the photovoltaic string with the reverse connection is prevented from being burned.

[0154] The photovoltaic system further includes a maintenance switch connected between the power taking circuit and the switching power supply;

[0155] The method further comprises:

[0156] Before closing the trip switch, if the maintenance switch is off, first close the maintenance switch, and then close the trip switch.

[0157] The photovoltaic system further comprises: a DC-DC conversion circuit and a DC-AC conversion circuit;

[0158] An input end of the DC-DC conversion circuit is connected to the trip switch, and an output end of the DC-DC conversion circuit is connected to the DC-AC conversion circuit;

[0159] The method further comprises:

[0160] When the DC-AC conversion circuit fails, the maintenance switch is turned off.

[0161] The maintenance switch is provided to ensure that the photovoltaic system meets the safety requirements during maintenance, and the maintenance switch is turned off to perform maintenance in a non-electric state.

[0162] The above description of disclosed embodiments enables one of ordinary skill in the art to make or use the application. Various modifications to these embodiments will be readily apparent to those of ordinary skill in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Therefore, the application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A photovoltaic system, characterized by, The photovoltaic system comprises at least two photovoltaic strings, a power taking circuit, a trip switch, a switching power supply, a controller and a maintenance switch. The at least two photovoltaic strings are connected in parallel; the trip switch is connected between the photovoltaic strings and the input end of a converter. The power taking circuit is used to take power from one photovoltaic string to supply power to the switching power supply; the maintenance switch is arranged on the line through which the power taking circuit supplies power to the switching power supply. The switching power supply is used to supply power to the controller and the trip switch when the power taking circuit normally supplies power. The controller is used to control the trip switch to be turned off when there is a wiring fault in the at least two photovoltaic strings connected in parallel; before the trip switch is turned on, the maintenance switch is turned on first and then the trip switch is turned on when the maintenance switch is turned off. The power taking circuit comprises a positive power taking circuit and / or a negative power taking circuit.

2. The photovoltaic system of claim 1, wherein, The positive power taking circuit is connected to the positive pole of the one photovoltaic string, and the negative power taking circuit is connected to the negative pole of the one photovoltaic string. The photovoltaic system further comprises a bidirectional rectifier circuit.

3. The photovoltaic system of claim 2, wherein, The bidirectional rectifier circuit is connected between the power taking circuit and the switching power supply. The bidirectional rectifier circuit is used to rectify the output voltage and output current of the power taking circuit and then provide the rectified output voltage and output current to the switching power supply. The bidirectional rectifier circuit comprises a first diode, a second diode, a third diode and a fourth diode. The cathode of the first diode and the cathode of the second diode are both connected to the positive end of the switching power supply; the anode of the second diode and the anode of the first diode are respectively connected to the positive power taking circuit and the negative power taking circuit.

4. The photovoltaic system of claim 3, wherein, The cathode of the third diode and the cathode of the fourth diode are respectively connected to the anode of the first diode and the anode of the second diode; the anode of the third diode and the anode of the fourth diode are both connected to the negative end of the switching power supply. The converter comprises a DC / DC conversion circuit; the photovoltaic system further comprises a fifth diode and a sixth diode; the DC / DC conversion circuit is connected between the trip switch and the switching power supply; the positive end of the DC / DC conversion circuit is connected to the positive end of the switching power supply through the fifth diode; and the negative end of the DC / DC conversion circuit is connected to the negative end of the switching power supply through the sixth diode. When the wiring of the photovoltaic string is normal, the one with higher voltage between the power taking circuit and the DC / DC conversion circuit supplies power to the switching power supply.

5. The photovoltaic system according to any of claims 1-4, characterized in that, 7. The photovoltaic system according to claim 3, wherein 6. The photovoltaic system of claim 5, wherein, The maintenance switch is connected between the photovoltaic string and the bidirectional rectifier circuit; or The maintenance switch is connected between the bidirectional rectifier circuit and the switching power supply. The photovoltaic system further comprises a seventh diode and an eighth diode. The seventh diode is connected between the positive end of the maintenance switch and the positive input end of the bidirectional rectifier circuit; and the eighth diode is connected between the negative end of the maintenance switch and the negative input end of the bidirectional rectifier circuit. The photovoltaic system further comprises a seventh diode and an eighth diode.

8. The photovoltaic system of claim 3, wherein, ​ ​ ​ 9. The photovoltaic system of claim 1, wherein, ​ A seventh diode and an eighth diode; the seventh diode and the eighth diode are connected in series on a positive line and a negative line between the maintenance switch and the switching power supply respectively, and the seventh diode and the eighth diode have anti-reverse functions.

10. The photovoltaic system according to any of claims 1-4, characterized in that, The controller and the switching power supply are located inside the converter.

11. A photovoltaic system characterized by, The photovoltaic system comprises a controller, a maintenance switch, a switching power supply, a power taking circuit and at least two sets of tripping switches, a first set of tripping switches and a second set of tripping switches for single-path DC-DC conversion circuit, each set of tripping switches comprises a plurality of contacts, and each contact is connected to a corresponding photovoltaic string. The power taking circuit is used to take power from one photovoltaic string to supply power to the switching power supply; the maintenance switch is arranged on the line through which the power taking circuit supplies power to the switching power supply; The switching power supply is used to supply power to the controller and the at least two sets of tripping switches when the power taking circuit is normally powered; The first set of tripping switches is connected to the positive poles of all photovoltaic strings and the negative poles of part of the photovoltaic strings, and the second set of tripping switches is connected to the negative poles of the remaining photovoltaic strings. Or, The first set of tripping switches is connected to the negative poles of all photovoltaic strings and the positive poles of part of the photovoltaic strings, and the second set of tripping switches is connected to the positive poles of the remaining photovoltaic strings. The controller is used to close the maintenance switch first and then close the tripping switch when the tripping switch is closed and the maintenance switch is opened.

12. A photovoltaic system characterized by, The photovoltaic system comprises a controller, a switching power supply, a power taking circuit, a maintenance switch, a converter and a tripping switch, and the tripping switch comprises a plurality of contacts, and each contact is connected to a corresponding photovoltaic string. The power taking circuit is used to take power from one photovoltaic string to supply power to the switching power supply; the maintenance switch is arranged on the line through which the power taking circuit supplies power to the switching power supply; when the tripping switch is closed and the maintenance switch is opened, the maintenance switch is closed first and then the tripping switch is closed; The switching power supply is used to supply power to the controller and the tripping switch when the power taking circuit is normally powered; A first end of the converter is connected to a photovoltaic string through the tripping switch, and a second end of the converter is connected to the switching power supply; The tripping switch is first connected to one photovoltaic string, and if the switching power supply is working normally, other photovoltaic strings are connected, and if the switching power supply is not working, other photovoltaic strings corresponding to the tripping switch are not connected.

13. A method of controlling a photovoltaic system, characterized by, The photovoltaic system comprises a converter, a power taking circuit, a tripping switch, a switching power supply and a maintenance switch; an input end of the converter is connected to at least two photovoltaic strings connected in parallel through the tripping switch; the power taking circuit is used to take power from one photovoltaic string to supply power to the switching power supply; the maintenance switch is arranged on the line through which the power taking circuit supplies power to the switching power supply; The method comprises: The switching power supply supplies power to the tripping switch when the power taking circuit is normally powered; Close the trip switch; control the trip switch to open when there is a wiring fault in the at least two photovoltaic strings connected in parallel; close the maintenance switch first and then close the trip switch when the maintenance switch is open before the trip switch is closed.

14. The control method according to claim 13, characterized by, The converter comprises a DC-DC conversion circuit and a DC-AC conversion circuit; An input end of the DC-DC conversion circuit is connected to the trip switch, and an output end of the DC-DC conversion circuit is connected to the DC-AC conversion circuit. The method further comprises: The maintenance switch is opened when the DC-AC conversion circuit fails.

15. A method of controlling a photovoltaic system, characterized by, The photovoltaic system comprises a controller, a maintenance switch, a switching power supply, a power taking circuit, and at least two sets of trip switches, wherein a first set of trip switches and a second set of trip switches are provided for a single-path DC-DC conversion circuit, each set of trip switches comprises a plurality of contacts, and each contact is connected to a corresponding photovoltaic string; the power taking circuit is configured to take power from one photovoltaic string to supply power to the switching power supply; and the maintenance switch is arranged on a line through which the power taking circuit supplies power to the switching power supply. The switching power supply is configured to supply power to the controller and the at least two sets of trip switches when the power taking circuit normally supplies power. The method comprises: The first set of trip switches is controlled to connect the positive poles of all photovoltaic strings and the negative poles of part of the photovoltaic strings, and the second set of trip switches is controlled to connect the negative poles of the remaining photovoltaic strings. Alternatively, The first set of trip switches is controlled to connect the negative poles of all photovoltaic strings and the positive poles of part of the photovoltaic strings, and the second set of trip switches is controlled to connect the positive poles of the remaining photovoltaic strings. The maintenance switch is closed first and then the trip switch is closed when the maintenance switch is open before the trip switch is closed.

16. A method of controlling a photovoltaic system, characterized by, The photovoltaic system comprises a controller, a switching power supply, a power taking circuit, a maintenance switch, a converter, and a trip switch, wherein the trip switch comprises a plurality of contacts, each contact is connected to a corresponding photovoltaic string; a first end of the converter is connected to the photovoltaic strings through the trip switch, and a second end of the converter is connected to the switching power supply; the power taking circuit is configured to take power from one photovoltaic string to supply power to the switching power supply; the maintenance switch is arranged on a line through which the power taking circuit supplies power to the switching power supply; and the switching power supply is configured to supply power to the controller and the trip switch when the power taking circuit normally supplies power. The method comprises: The trip switch is connected to one photovoltaic string first; It is determined whether the switching power supply normally works, and then other photovoltaic strings are connected; If it is determined that the switching power supply does not work, other photovoltaic strings corresponding to the trip switch are not connected; The maintenance switch is closed first and then the trip switch is closed when the maintenance switch is open before the trip switch is closed.

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