Photovoltaic system

Abstract

The photovoltaic system comprises at least two photovoltaic group strings, a power taking loop, a tripping switch, a switching power supply, a controller and a maintenance switch, the at least two photovoltaic groups are connected in series and in parallel; the photovoltaic system comprises a series loop, the series loop at least comprises a tripping switch and a DCDC conversion circuit, a first direct current side of the series loop is connected with at least two photovoltaic strings, and a second direct current side of the series loop is connected with a switching power supply; the power taking loop is used for taking power from at least one photovoltaic group string to supply power to the switching power supply; the maintenance switch is arranged on a line of the power taking loop for supplying power to the switching power supply; the switching power supply is used for supplying power to the controller and the tripping switch when the power taking loop supplies power normally; the controller is used for controlling the tripping switch to be switched off when a wiring fault exists in the at least two photovoltaic group strings which are connected in parallel; before the tripping switch is closed, when the maintenance switch is disconnected, the maintenance switch is firstly closed, and then the tripping switch is closed. The reliability and the safety of the circuit can be improved.

Description

[0001] This application is a divisional application of the invention patent "A Photovoltaic System and Control Method" filed on September 2, 2022, with application number 202211071565.X. Technical Field

[0002] This application relates to the field of new energy power generation technology, specifically to a photovoltaic system. Background Technology

[0003] With the continuous development of new energy sources, photovoltaic power generation is becoming increasingly widespread, typically involving multiple photovoltaic strings connected in parallel. Each photovoltaic string includes multiple photovoltaic modules connected in series, and each photovoltaic module contains multiple solar cells connected in series. Anti-parallel diodes are connected between the positive and negative terminals of the photovoltaic module and the corresponding solar cell connection points.

[0004] When multiple photovoltaic (PV) strings are connected in parallel, if one or more strings are reverse-connected, when the switch is closed, all the current from the normally connected PV strings will flow into the reverse-connected PV strings. When a reverse-connected PV string occurs, the PV system's power supply cannot function properly, so it cannot issue a command to disconnect the switch. If the reverse current is large, it can also damage the solar cells. Summary of the Invention

[0005] In view of this, this application provides a photovoltaic system, control method and power supply system that can prevent the photovoltaic string from burning out when it is reverse-connected.

[0006] This application provides a photovoltaic system, including: at least two photovoltaic strings, a power supply circuit, a trip switch, a switching power supply, and a controller; At least two photovoltaic strings are connected in parallel; a trip switch is connected between the photovoltaic strings and the input terminal of the converter; A power supply circuit is used to draw power from at least one photovoltaic string to supply power to the switching power supply. A switching power supply is used to supply power to the controller and trip switch when the power supply circuit is normally powered. The controller is used to control the trip switch to open when a wiring fault exists in at least two photovoltaic strings connected in parallel.

[0007] Preferably, the power supply circuit includes a positive power supply circuit and / or a negative power supply circuit; The positive power supply circuit is connected to the positive terminal of at least one photovoltaic string, and the negative power supply circuit is connected to the negative terminal of at least one photovoltaic string.

[0008] Preferably, it further includes: a bidirectional rectifier circuit; The bidirectional rectifier circuit is connected between the power supply circuit and the switching power supply; A bidirectional rectifier circuit is used to rectify the output voltage and output current of the power supply circuit and then supply them to the switching power supply.

[0009] Preferably, the bidirectional rectifier circuit includes: a first diode, a second diode, a third diode, and a fourth diode; The cathodes of the first diode and the second diode are both connected to the positive terminal of the switching power supply. The anodes of the second diode and the first diode are connected to the positive power supply circuit and the negative power supply circuit, respectively. The cathodes of the third diode and the fourth diode are connected to the anodes of the first diode and the second diode, respectively. The anodes of both the third diode and the fourth diode are connected to the negative terminal of the switching power supply.

[0010] Preferably, it further includes: a DC-DC conversion circuit, 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 terminal of the DC-DC conversion circuit is connected to the positive terminal of the switching power supply through the fifth diode, and the negative terminal of the DC-DC conversion circuit is connected to the negative terminal of the switching power supply through the sixth diode.

[0011] Preferably, when the photovoltaic array string connection is normal, the higher voltage in the power supply circuit and the DC-DC conversion circuit is supplied by the switching power supply.

[0012] Preferably, the power supply circuit further includes: a maintenance switch; 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; If the maintenance switch is open before the trip switch is closed, close the maintenance switch first, and then close the trip switch.

[0013] Preferably, it further includes: a seventh diode and an eighth diode; 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.

[0014] Preferably, both the controller and the switching power supply are located inside the converter.

[0015] This application also provides a photovoltaic system, which 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; The first trip switch connects the positive terminal of all photovoltaic strings and the negative terminal of some photovoltaic strings, and the second trip switch connects the negative terminal of the remaining photovoltaic strings. or, The first trip switch connects to the negative terminal of all photovoltaic strings and the positive terminal of some photovoltaic strings, while the second trip switch connects to the positive terminal of the remaining photovoltaic strings.

[0016] This application also provides a photovoltaic system, which 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 via a trip switch, and the second end of the converter is connected to the switching power supply. The trip switch is first connected to one photovoltaic string. If the switching power supply is working normally, then other photovoltaic strings are connected. If the switching power supply is not working, then other photovoltaic strings corresponding to the trip switch are not connected.

[0017] This application also provides a control method for a photovoltaic system, the photovoltaic system including: a converter, a power supply circuit, a trip switch and a switching power supply; the input terminal of the converter is connected to at least two photovoltaic strings connected in parallel through the trip switch; the power supply circuit is used to draw power from at least one photovoltaic string to supply power to the switching power supply; The method includes: When the power supply circuit is normally powered, the switching power supply is powered by the trip switch; Close the trip switch; when a wiring fault exists in at least two photovoltaic strings connected in parallel, control the trip switch to open.

[0018] Preferably, the photovoltaic system further includes: a maintenance switch connected between the power supply circuit and the switching power supply; The method also includes: Close the maintenance switch before closing the trip switch.

[0019] Preferably, the photovoltaic system further includes: a DC-DC conversion circuit and a DC-AC conversion circuit; The input terminal of the DC-DC converter circuit is connected to a trip switch, and the output terminal of the DC-DC converter circuit is connected to a DC-AC converter circuit. The method also includes: In case of a DC-AC conversion circuit failure, disconnect the maintenance switch.

[0020] 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; The method includes: 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. or, The first trip switch connects to the negative terminal of all photovoltaic strings and the positive terminal of some photovoltaic strings, while the second trip switch connects to the positive terminal of the remaining photovoltaic strings.

[0021] 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. The method includes: 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; If the switching power supply is determined to be not working, then other photovoltaic strings corresponding to the trip switch will not be connected.

[0022] Therefore, this application has the following beneficial effects: 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

[0023] Figure 1 A schematic diagram of a photovoltaic system provided in this application; Figure 2 A schematic diagram of another photovoltaic system provided in the embodiments of this application; Figure 3 A schematic diagram of another photovoltaic system provided in the embodiments of this application; Figure 4 This is a schematic diagram of another photovoltaic system provided in the embodiments of this application.

[0024] Figure 5 A schematic diagram of another photovoltaic system provided in the embodiments of this application; Figure 6 A schematic diagram of another photovoltaic system provided in the embodiments of this application; Figure 7 This is a schematic diagram of the connection of a photovoltaic string provided in an embodiment of this application; Figure 8This is another schematic diagram of photovoltaic string connection provided in an embodiment of this application; Figure 9 This is a flowchart of a control method for a photovoltaic system provided in an embodiment of this application. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solutions provided in the embodiments of this application, the application scenarios of the technical solutions provided in this application will be introduced below.

[0026] See Figure 1 The figure is a schematic diagram of a photovoltaic system provided in this application.

[0027] In addition to photovoltaic strings, the photovoltaic system also includes: converter, trip switch 100 and switching power supply 200; Figure 1 The example described uses the trip switch 100 connected to n photovoltaic strings. The n photovoltaic strings are connected in parallel. That is, PV1+, PV2+ up to PVn+ are connected together, and PV1-, PV2- up to PVn- are connected together.

[0028] The following description uses a converter including a DC-DC conversion circuit 300 as an example. It should be understood that the converter may include a DC-DC conversion circuit and a DC-AC conversion circuit.

[0029] To promptly disconnect the photovoltaic string from the downstream circuit in the event of a photovoltaic system failure, a trip switch 100 is installed between the DC-DC converter circuit 300 and the photovoltaic string. The trip switch 100, also known as a tripping switch, can be opened by the controller, but it must be manually closed; the controller cannot control its closure.

[0030] The switching power supply 200 serves as an auxiliary power source for the photovoltaic system, drawing power from the DC-DC conversion circuit 300. The switching power supply 200 also powers the trip switch 100 and the control circuit (not shown in the figure). For example, the control circuit typically includes a controller.

[0031] The switching power supply 200 can be the internal switching power supply of the inverter.

[0032] A capacitor C1 is connected to the output terminal of the DC-DC converter circuit 300.

[0033] The embodiments of this application do not specifically limit the specific topology and working principle of the DC-DC conversion circuit 300.

[0034] When a reverse connection exists in the photovoltaic string, the controller controls the trip switch 100 to open, thereby protecting the photovoltaic string. However, when the photovoltaic system starts working, the power supply 200 is powered by the photovoltaic string. Therefore, when there is a wiring fault such as a reverse-connected string in the photovoltaic string, the power supply 200 will not work. Consequently, the power supply 200 cannot supply power to the trip switch 100 and the controller, and the controller cannot open the trip switch 100, thus failing to provide reverse connection protection.

[0035] To address the aforementioned technical problems, this application provides a photovoltaic system that adds a power supply circuit to directly draw power from the photovoltaic strings for the switching power supply, bypassing the trip switch. When power is available, the switching power supply operates normally, powering the trip switch and controller. Upon detection of a reverse-connected photovoltaic string after the trip switch closes, the controller can trip the switch normally, i.e., disconnect it. When the power supply circuit cannot draw power normally, the switching power supply cannot operate, failing to power the trip switch and controller. In this case, the trip switch will not close, thus achieving reverse connection protection. That is, regardless of whether the photovoltaic strings connected to the power supply circuit are reverse-connected, protection can be provided for all reverse-connected photovoltaic strings. This effect is more pronounced when the photovoltaic system includes three or more photovoltaic strings; that is, with at least three photovoltaic strings, the more reverse-connected photovoltaic strings there are, the greater the reverse current, and the more likely the photovoltaic strings will burn out.

[0036] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0037] See Figure 2 This figure is a schematic diagram of another photovoltaic system provided in an embodiment of this application.

[0038] The photovoltaic system provided in this embodiment includes: a converter, a power supply circuit, a trip switch 100, a switching power supply 200, and a controller (not shown in the figure). Taking the converter including the DC-DC conversion circuit 300 as an example, the power supply circuit includes a positive power supply circuit 401 and / or a negative power supply circuit 402. The specific implementation of the power supply circuit in this application is not limited; it may include only one or both. The following description uses an example including a positive power supply circuit 401 and a negative power supply circuit 402.

[0039] The positive electrode power supply circuit 401 is connected to the positive electrode of at least one photovoltaic string, and the negative electrode power supply circuit 402 is connected to the negative electrode of at least one photovoltaic string.

[0040] The input terminal of the converter is connected to at least two photovoltaic strings connected in parallel via a trip switch 100; Figure 2The example described uses the trip switch 100 connected to n photovoltaic strings. The n photovoltaic strings are connected in parallel. That is, PV1+, PV2+ up to PVn+ are connected together, and PV1-, PV2- up to PVn- are connected together.

[0041] The power extraction circuit is used to draw power from at least one photovoltaic (PV) string to supply power to the switching power supply 200. In the diagram, the power extraction circuit draws power from n PV strings; that is, the positive power extraction circuit 401 connects to PV1+, PV2+, and PVn+, and the negative power extraction circuit 402 connects to PV1-, PV2-, and PVn-. It should be understood that, provided the voltage requirements are met, the power extraction circuit can be selected to draw power from only a portion of the PV strings.

[0042] In addition to supplying power to the controller and trip switch, the power supply circuit can also supply power to the sampling circuit and communication circuit.

[0043] The switching power supply 200 is used to supply power to the controller and the trip switch 100 when the power supply circuit is normally powered. The controller is used to control the trip switch 100 to open when a wiring fault exists in at least two photovoltaic strings connected in parallel.

[0044] Wiring faults in photovoltaic strings include at least reverse connection of the photovoltaic strings, and may also include other wiring faults such as short circuits.

[0045] The photovoltaic system provided in this embodiment has a dedicated power supply circuit that can directly draw power from the photovoltaic string to power the switching power supply, which in turn powers the controller and the trip switch 100.

[0046] When the photovoltaic (PV) strings connected to the power supply circuit are 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 PV strings will not burn out. Conversely, when all PV strings connected to the power supply circuit are normal and there is no reverse connection, the switching power supply can operate normally, supplying power to the trip switch and controller, and the trip switch can close. If the switching power supply supplies power to the trip switch and controller, and after the trip switch closes, if there is a wiring fault in the PV string connected to the trip switch, the controller can control the trip switch to open, thus preventing the reverse-connected PV strings from burning out.

[0047] The controller is used to control the trip switch 100 to open when at least two photovoltaic strings connected in parallel are reverse-connected. That is, as long as the trip switch 100 is closed, the controller can control the trip switch 100 to trip when there is a reverse connection in the photovoltaic strings.

[0048] If the switching power supply 200 fails to work properly, it indicates that the photovoltaic string is reverse-connected. The power supply circuit cannot supply power to the switching power supply 200 normally, and the switching power supply 200 will not supply power to the controller and trip switch 100. At this time, the trip switch 100 will not close, thus avoiding the problem of the solar panels burning out due to the reverse-connected photovoltaic string.

[0049] It should be understood that when the power supply circuit is connected to the photovoltaic string, if the photovoltaic string is connected normally, the switching power supply will work normally after a preset time period; if there is a reverse connection in the photovoltaic string connected to the power supply circuit, the switching power supply will still not work normally after the preset time period.

[0050] The technical solution provided in this application is mainly to solve the problem that when the photovoltaic string is first connected to the inverter, the switching power supply can supply power normally, so that when the photovoltaic string is reverse connected, the controller can normally control the trip switch 100 to open, thereby protecting the reverse connected photovoltaic string and preventing it from burning out.

[0051] The following section, with reference to the accompanying diagram, introduces another photovoltaic system that incorporates a bidirectional rectifier circuit. Regardless of whether the photovoltaic strings connected to the power supply circuit are reverse-connected, it can still provide normal power to the switching power supply.

[0052] See Figure 3 This figure is a schematic diagram of another photovoltaic system provided in an embodiment of this application.

[0053] The photovoltaic system provided in this embodiment also includes: a bidirectional rectifier circuit; A bidirectional rectifier circuit is connected between the power supply circuit and the switching power supply 200. The bidirectional rectifier circuit is used to rectify the output voltage and output current of the power supply circuit and then supply them to the switching power supply 200.

[0054] One possible implementation is a bidirectional rectifier circuit comprising: a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4; The cathodes of the second diode D2 and the first diode D1 are both connected to the positive terminal of the switching power supply 200. The anodes of the second diode D2 and the first diode D1 are connected to the positive power supply circuit 401 and the negative power supply circuit 402, respectively. The cathodes of the third diode D3 and the fourth diode D4 are connected to the anodes of the first diode D1 and the second diode D2, respectively. The anodes of the third diode D3 and the fourth diode D4 are both connected to the negative terminal of the switching power supply 200.

[0055] It should be understood that diodes D1, D2, D3, and D4 form a full-bridge rectifier. Even if the photovoltaic string connected to the power supply circuit is reverse-connected, the reverse current can still power the switching power supply 200 through the bidirectional rectifier circuit. Therefore, the switching power supply 200 can power the trip switch 100 and the controller. If a reverse-connected photovoltaic string exists, the controller can control the trip switch 100 to trip, protecting the reverse-connected photovoltaic string from burnout.

[0056] To prevent the current output from the power extraction circuit from flowing back into the DC-DC converter circuit 300, the photovoltaic system provided in this application embodiment further includes: a fifth diode D5 and a sixth diode D6; the DC-DC converter circuit 300 is connected between the trip switch 100 and the switching power supply 200, the positive terminal of the DC-DC converter 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 DC-DC converter circuit 300 is connected to the negative terminal of the switching power supply 200 through the sixth diode D6.

[0057] It should be understood that Figure 2 The photovoltaic system shown may also include D5 and D6, and the specific connection relationship is as follows: Figure 3 D5 and D6 are the same, so I won't go into details here.

[0058] To further ensure the safety of the photovoltaic system, the photovoltaic system provided in this application embodiment also includes a maintenance switch. A detailed description is provided below with reference to the accompanying drawings.

[0059] See Figure 4 This figure is a schematic diagram of another photovoltaic system provided in an embodiment of this application.

[0060] The photovoltaic system provided in this embodiment also includes: a maintenance switch 500; Maintenance switch 500 is connected between the power supply circuit and the bidirectional rectifier circuit; that is, the positive input terminal of maintenance switch 500 is connected to the positive power supply circuit 401, and the negative input terminal of maintenance switch 500 is connected to the negative power supply circuit 402. The positive output terminal of maintenance switch 500 is connected to the positive input terminal of the bidirectional rectifier circuit, and the negative output terminal of maintenance switch 500 is connected to the negative input terminal of the bidirectional rectifier circuit.

[0061] If the maintenance switch 500 is open before closing the trip switch 100, close the maintenance switch 500 first, then close the trip switch 100. If the maintenance switch 500 is already closed before closing the trip switch 100, then close the trip switch 100 directly. The maintenance switch 500 is a manual switch and needs to be closed and opened manually.

[0062] Maintenance switch 500 is set on the power supply circuit that supplies power to switching power supply 200. After all the photovoltaic strings are connected, maintenance switch 500 is closed first. After a preset time period, if switching power supply 200 is normal, trip switch 100 is closed. After trip switch 100 is closed, if there is a reverse connection of photovoltaic strings, the controller can control trip switch 100 to trip normally.

[0063] When the downstream DC-AC conversion circuit requires maintenance, the maintenance switch 500 can be manually disconnected to meet safety requirements.

[0064] The embodiments of this application do not specifically limit the implementation type of the maintenance switch 500; it can be a normally open switch or a normally closed switch.

[0065] To further prevent backflow of current, two diodes may be included between the maintenance switch 500 and the bidirectional rectifier circuit.

[0066] See Figure 5 This figure is a schematic diagram of another photovoltaic system provided in an embodiment of this application.

[0067] The photovoltaic system provided in this embodiment also includes: a seventh diode D7 and an eighth diode D8; The seventh diode D7 is connected between the positive terminal of the maintenance switch 500 and the positive input terminal of the bidirectional rectifier circuit, and the eighth diode D8 is connected between the negative terminal of the maintenance switch 500 and the negative input terminal of the bidirectional rectifier circuit.

[0068] It should be understood that when the photovoltaic (PV) string is first connected to the inverter, the switching power supply can draw power from either the PV string or the DC-DC converter 300. The specific power draw method can be a voltage comparison. Due to the presence of D5 and D7, the side with the higher voltage supplies power to the switching power supply 200. For example, if the output voltage of D7 is higher than the output voltage of D5, then the PV string will supply power to the switching power supply 200. If the output voltage of D5 is higher than the output voltage of D7, then the DC-DC converter 300 will supply power to the switching power supply 200. Comparatively, the power supply from the DC-DC converter 300 is more stable. The voltage of the PV string is prone to fluctuations due to environmental factors.

[0069] Figure 4 The photovoltaic system described herein includes a bidirectional rectifier circuit and a maintenance switch as an example. It should be understood that the photovoltaic system provided in this embodiment may also include a maintenance switch, but not a bidirectional rectifier circuit. The following description is in conjunction with the accompanying drawings.

[0070] It should be understood that the above Figure 4 and Figure 5The examples all use the maintenance switch connected to the input terminal of the bidirectional rectifier circuit as an example. In addition, the maintenance switch can also be connected to the output terminal of the bidirectional rectifier circuit, that is, connected between the bidirectional rectifier circuit and the switching power supply.

[0071] See Figure 6 This figure is a schematic diagram of another photovoltaic system provided in an embodiment of this application.

[0072] In the photovoltaic system provided in this embodiment, the maintenance switch 500 is connected between the power supply circuit 401 and the switching power supply 200. Specifically, the positive input terminal of the maintenance switch 500 is connected to the positive power supply circuit 401, and the negative input terminal is connected to the negative power supply circuit 402. The positive output terminal of the maintenance switch 500 is connected to the positive terminal of the switching power supply 200, and the negative output terminal is connected to the negative terminal of the switching power supply 200.

[0073] In the photovoltaic system provided in the above embodiments of this application, the location of the switching power supply is not specifically limited; for example, it can be located inside the inverter, serving as the switching power supply within the inverter. Since this switching power supply can operate normally, it can provide reliability for the inverter's operation.

[0074] In addition to the photovoltaic system described above that can prevent photovoltaic string burnout, this application also provides other implementation methods, which will be described below with reference to the accompanying drawings.

[0075] See Figure 7 The figure is a schematic diagram of the connection of a photovoltaic string provided in an embodiment of this application.

[0076] This embodiment provides a photovoltaic system, which includes at least two sets of trip switches: a first trip switch and a second trip switch. Each set of trip switches includes multiple contacts, and each contact is connected to a corresponding photovoltaic string. The first trip switch connects the positive terminal of all photovoltaic strings and the negative terminal of some photovoltaic strings, and the second trip switch connects the negative terminal of the remaining photovoltaic strings. or, The first trip switch connects to the negative terminal of all photovoltaic strings and the positive terminal of some photovoltaic strings, while the second trip switch connects to the positive terminal of the remaining photovoltaic strings.

[0077] like Figure 7 As shown, a set of trip switches is connected to all the positive terminals of the photovoltaic strings and some of the negative terminals of the photovoltaic strings, while another set of trip switches is connected to the negative terminals of the remaining photovoltaic strings.

[0078] A single-channel DC-DC conversion circuit corresponds to n photovoltaic strings. The positive and negative terminals (PV1+, PV1-, PV2+, PV2-) of photovoltaic strings PV1 and PV2 are connected to the first set of trip switches 101. The positive terminals of the remaining photovoltaic strings PV3-PVn are connected to the first set of trip switches 101, and the negative terminals of the remaining photovoltaic strings PV3-PVn are connected to the second set of trip switches 102.

[0079] This embodiment uses an inverter including a DC-DC conversion circuit 300 and a DC-AC conversion circuit 600 as an example for description.

[0080] After all the photovoltaic strings of the inverter are connected, the first set of trip switches 101 is closed first. For example, wait for a preset time t. If the inverter's switching power supply works, then close the other switches. If the switching power supply cannot work normally, it means that PV1 or PV2 is reverse connected. Since only at most two photovoltaic strings are reverse connected, the reverse current will not be too large and will not cause damage to the solar panels. The remaining trip switches do not need to be closed.

[0081] Apart from Figure 7 Alternatively, the negative terminals of all photovoltaic strings and the positive terminals of some photovoltaic strings can be connected to the same set of trip switches, while the positive terminals of the remaining photovoltaic strings can be connected to another set of trip switches.

[0082] See Figure 8 This figure is a schematic diagram of another photovoltaic string connection provided in an embodiment of this application.

[0083] A single-channel DC-DC conversion circuit corresponds to n photovoltaic strings. The positive and negative terminals (PV1+, PV1-, PV2+, PV2-) of photovoltaic strings PV1 and PV2 are connected to the first set of trip switches 101. The negative terminals of the remaining photovoltaic strings PV3-PVn are connected to the first set of trip switches 101, and the positive terminals of the remaining photovoltaic strings PV3-PVn are connected to the second set of trip switches 102.

[0084] Figure 8 The connection method shown can also provide protection, as it will not generate a large reverse current when reversed, thus preventing the photovoltaic string from burning out.

[0085] Traditionally, all photovoltaic strings corresponding to the same DC-DC conversion circuit are connected to the same trip switch. When one or more photovoltaic strings are reverse-connected, the current of the normal photovoltaic string will all flow into the reverse-connected photovoltaic string, which will damage the solar panels in the reverse-connected photovoltaic string.

[0086] The method provided in this embodiment involves connecting all or part of the positive and negative terminals of one or two photovoltaic strings in the same DC-DC conversion circuit to the first set of trip switches, while connecting the other terminal of the remaining photovoltaic strings to the second set of trip switches. This ensures that when the first set of trip switches is closed, only one or two strings are connected to the inverter. If one or two strings are reverse-connected, the reverse current will not be too large, and the reverse current in the reverse-connected solar panels will not damage the panels or cause them to burn out.

[0087] In addition, this application also provides another solution to avoid photovoltaic string burnout due to reverse connection, which will be described in detail below.

[0088] The photovoltaic system provided in this embodiment includes: a switching power supply, a converter, and a trip switch. The trip switch includes multiple contacts, and each contact is connected to a corresponding photovoltaic string. The first end of the converter is connected to the photovoltaic string via a trip switch, and the second end of the converter is connected to the switching power supply. The trip switch is first connected to one photovoltaic string. If the switching power supply is working normally, then other photovoltaic strings are connected. If the switching power supply is not working, then other photovoltaic strings corresponding to the trip switch are not connected.

[0089] Even if a single photovoltaic string is reverse-connected, the reverse current is very small. If it is normal, the single photovoltaic string will be used to power the switching power supply. If it is reverse-connected, it will not supply power and will not be connected to other photovoltaic strings, thus ensuring the safety of the system.

[0090] Based on the photovoltaic system provided in the above embodiments, this application also provides a control method for the photovoltaic system, which will be described in detail below with reference to the accompanying drawings.

[0091] See Figure 9 The figure is a flowchart of a control method for a photovoltaic system provided in an embodiment of this application.

[0092] The photovoltaic system control method provided in this embodiment includes a photovoltaic system comprising: a converter, a power supply circuit, a trip switch, and a switching power supply; the input terminal of the converter is connected to at least two photovoltaic strings connected in parallel via the trip switch; the power supply circuit is used to draw power from at least one photovoltaic string to supply power to the switching power supply. The method includes: S701: When the power supply circuit is normally powered, the switching power supply is powered by the trip switch; When the power supply circuit is connected to the photovoltaic string, if the photovoltaic string is connected normally, the switching power supply will work normally after a preset time period. If there is a reverse connection in the photovoltaic string connected to the power supply circuit, the switching power supply will still not work normally after the preset time period. In this case, the trip switch will not close, so the photovoltaic string will not burn out due to the reverse connection.

[0093] S702: Controls the trip switch to close; controls the trip switch to open when a wiring fault exists in at least two photovoltaic strings connected in parallel.

[0094] 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. disconnect, when there is a wiring fault such as reverse connection in the photovoltaic string.

[0095] Because of the photovoltaic system, a dedicated power extraction circuit is set up, which can directly draw power from the photovoltaic string to supply power to the switching power supply.

[0096] When the photovoltaic (PV) strings connected to the power supply circuit are 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 PV strings will not burn out. Conversely, when all PV strings connected to the power supply circuit are normal and there is no reverse connection, the switching power supply can operate normally, supplying power to the trip switch and controller, and the trip switch can close. If the switching power supply supplies power to the trip switch and controller, and after the trip switch closes, if there is a wiring fault in the PV string connected to the trip switch, it can control the trip switch to open, thus preventing the reverse-connected PV strings from burning out.

[0097] The photovoltaic system also includes: a maintenance switch connected between the power supply circuit and the switching power supply; The method also includes: If the maintenance switch is open before closing the trip switch, close the maintenance switch first, and then close the trip switch.

[0098] Photovoltaic systems also include: DC-DC conversion circuits and DC-AC conversion circuits; The input terminal of the DC-DC converter circuit is connected to a trip switch, and the output terminal of the DC-DC converter circuit is connected to a DC-AC converter circuit. The method also includes: In case of a DC-AC conversion circuit failure, disconnect the maintenance switch.

[0099] Setting up a maintenance switch ensures that the photovoltaic system meets safety regulations during maintenance. When the maintenance switch is off, maintenance can be performed in a power-off state.

[0100] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not 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 application relates to a photovoltaic system. 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 photovoltaic system comprises a string circuit, the string circuit at least comprising the trip switch and a DC / DC conversion circuit, a first direct current side of the string circuit being connected to the at least two photovoltaic strings, and a second direct current side of the string circuit being connected to the switching power supply. The trip switch is connected between the photovoltaic string and an input end of the DC / DC conversion circuit. The power taking circuit is used for taking power from at least 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. The switching power supply is used for supplying power to the controller and the trip switch when the power taking circuit normally supplies power. The controller is used for controlling 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.

2. The photovoltaic system of claim 1, wherein, The string circuit is connected in parallel with a line through which the power taking circuit supplies power to the switching power supply.

3. The photovoltaic system of claim 1, wherein, The string circuit comprises a first part connected in parallel with a line through which the power taking circuit supplies power to the switching power supply, and the first part is provided with the trip switch.

4. The photovoltaic system of claim 3, wherein, The trip switch is connected in parallel with the power taking circuit.

5. The photovoltaic system of claim 3, wherein, The string circuit comprises a second part connected in parallel with a line through which the power taking circuit supplies power to the switching power supply, and the second part is provided with the trip switch and the DC / DC conversion circuit.

6. A photovoltaic system according to any one of claims 1 to 5, characterised in that, The power taking circuit takes power from part of the at least one photovoltaic string.

7. The photovoltaic system of claim 6, wherein, The power taking circuit takes power from one photovoltaic string in the at least one photovoltaic string.

8. A photovoltaic system according to any one of claims 1 to 5, characterised in that, The power taking circuit comprises a positive electrode power taking circuit and a negative electrode power taking circuit; the positive electrode power taking circuit is connected to a positive electrode of the one photovoltaic string, the negative electrode power taking circuit is connected to a negative electrode of the one photovoltaic string, a seventh diode is arranged between the positive electrode power taking circuit and the switching power supply, an eighth diode is arranged between the negative electrode power taking circuit and the switching power supply, and the seventh diode and the eighth diode are both anti-reverse diodes.

9. The photovoltaic system of claim 1 or 2, wherein, Further comprising: A bidirectional rectifier circuit is connected between the power taking circuit and the switching power supply, and is used for rectifying output voltage and output current of the power taking circuit and then providing the rectified output voltage and output current to the switching power supply.

10. The photovoltaic system of claim 9, wherein, The bidirectional rectifier circuit comprises a first diode, a second diode, a third diode and a fourth diode. A cathode of the first diode and a cathode of the second diode are both connected to a positive terminal of the switching power supply, an anode of the second diode and an anode of the first diode are respectively connected to the positive electrode power taking circuit and the negative electrode power taking circuit. A cathode of the third diode and a cathode of the fourth diode are respectively connected to the anode of the first diode and the anode of the second diode, and an anode of the third diode and an anode of the fourth diode are both connected to a negative terminal of the switching power supply.

11. The photovoltaic system of claim 9, wherein, Further comprising: 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.

12. The photovoltaic system of claim 9, 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.

13. The photovoltaic system of any of claims 1-5, wherein, The photovoltaic system further comprises a fifth diode and a sixth diode. The DCDC conversion circuit is connected between the trip switch and the switching power supply, the positive end of the DCDC conversion circuit is connected to the positive end of the switching power supply through the fifth diode, and the negative end of the DCDC conversion circuit is connected to the negative end of the switching power supply through the sixth diode.

14. The photovoltaic system of claim 13, wherein, When the photovoltaic string is connected normally, the one with higher voltage in the power taking circuit and the DCDC conversion circuit supplies power to the switching power supply.

15. The photovoltaic system of any of claims 1-14, wherein, The controller and the switching power supply are both located inside the converter.

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