Photovoltaic system and method for circuit protection of a photovoltaic system

Abstract

The application provides a photovoltaic system and a circuit protection method of the photovoltaic system. The photovoltaic system comprises an active protection switch, a DC-DC conversion circuit and a controller; one end of the active protection switch is used for connecting a photovoltaic module, the other end is connected with an input end of the DC-DC conversion circuit, and an output end of the DC-DC conversion circuit is used for connecting a load; the controller is used for, when a reverse current of the photovoltaic unit is greater than or equal to a current threshold value, issuing a breaking instruction for triggering the active protection switch to be broken according to an input voltage of the DC-DC conversion circuit, and in the case that the active protection switch is not effectively broken within a preset time length after the breaking instruction is issued to the active protection switch, adjusting the input voltage of the DC-DC conversion circuit to be less than or equal to a first voltage threshold value. The scheme of the application can improve the safety and reliability of the photovoltaic system.

Description

Technical Field

[0001] This application relates to the field of photovoltaic power generation technology, and in particular to a photovoltaic system and a circuit protection method for a photovoltaic system. Background Technology

[0002] With the development of the photovoltaic industry, photovoltaic systems are constantly evolving towards higher power outputs. However, the increase in photovoltaic system power also leads to a continuous increase in safety risks. If timely and effective protection cannot be provided, it may not only cause photovoltaic modules or inverters in the photovoltaic system to burn out, but also easily cause single-point failures to spread, leading to more serious accidents.

[0003] To address this issue, a protective device can be installed in the photovoltaic system to cut off the energy input to the photovoltaic modules in the event of a fault. However, this protective device may fail to disconnect the circuit due to mechanical failure, posing a safety hazard to the photovoltaic system. Summary of the Invention

[0004] This application provides a photovoltaic system and a circuit protection method for the photovoltaic system, which can eliminate reverse current in the photovoltaic system through further protection measures when the protection device is detected to have failed to disconnect effectively, thereby preventing burnout and fault propagation in the photovoltaic system and improving the safety and reliability of the photovoltaic system.

[0005] In a first aspect, this application provides a photovoltaic system, including an active protection switch, a DC-DC converter circuit, and a controller; one end of the active protection switch is connected to a photovoltaic module, and the other end is connected to the input terminal of the DC-DC converter circuit, the output terminal of the DC-DC converter circuit is connected to a load; the controller is used to issue a disconnect command to the active protection switch to trigger the active protection switch to disconnect according to the input voltage of the DC-DC converter circuit when the reverse current of the photovoltaic module is greater than or equal to a current threshold, and if the active protection switch fails to disconnect effectively within a preset time after issuing the disconnect command, the controller adjusts the input voltage of the DC-DC converter circuit to be less than or equal to a first voltage threshold.

[0006] This photovoltaic system, upon detecting reverse current, can further determine the fault scenario by adjusting the input voltage of the DC-DC converter circuit. After identifying the fault scenario, it can activate the active protection circuit for protection. If the active protection switch fails to trip, further protection measures—reducing the input voltage of the DC-DC converter circuit—can eliminate the reverse current in the photovoltaic system, preventing burnout and fault propagation, thereby improving the safety and reliability of the photovoltaic system.

[0007] In one implementation of the first aspect, the controller detects that the active protection switch has not been effectively disconnected when the current in the DC-DC converter circuit is greater than or equal to a critical value. This solution can determine whether the active protection switch has been effectively disconnected by detecting the current in the DC-DC converter circuit. It is simple in design, easy to mass-produce, and has high reliability.

[0008] In one implementation of the first aspect, the controller is used to adjust the input voltage of the DC-DC converter circuit to be greater than 0 and less than or equal to a first voltage threshold, and detects that the active protection switch has not been effectively disconnected when the current of the DC-DC converter circuit is detected to be greater than or equal to a critical value.

[0009] In this solution, by controlling the input voltage to a level greater than 0 and less than or equal to the first voltage threshold, the DC-DC converter circuit is in a state close to a short circuit but not actually short-circuited. This not only detects whether the active protection switch is effectively disconnected, but also maintains the output voltage of the DC-DC converter circuit at a certain value, so as to supply power to the load in the photovoltaic inverter (the load may include a heat dissipation device, which can operate under electric power to maintain the heat dissipation performance of the photovoltaic inverter). This eliminates the need for an additional power supply to the photovoltaic inverter, thereby simplifying the design and reducing costs.

[0010] In one implementation of the first aspect, the controller keeps the switching devices of the DC-DC converter circuit constantly on, and detects that the active protection switch has not been effectively disconnected when the current of the DC-DC converter circuit is detected to be greater than or equal to a critical value. This solution has simple judgment logic, is easy to mass-produce, and has high reliability.

[0011] In one implementation of the first aspect, the active protection switch is used to generate a contact position feedback signal; the controller is used to detect that the active protection switch has not been effectively disconnected when the contact position feedback signal is the target signal. The circuit design and judgment logic of this solution are relatively simple, easy to mass-produce, and have high reliability.

[0012] In one implementation of the first aspect, the controller detects that the active protection switch has not been effectively disconnected when it detects that the input voltage of the DC-DC circuit is greater than or equal to a second voltage threshold. This solution can determine whether the active protection switch has been effectively disconnected by detecting the input voltage of the DC-DC converter circuit. It is simple in design, easy to mass-produce, and has high reliability.

[0013] In one implementation of the first aspect, the controller adjusts the input voltage of the DC-DC converter circuit to be greater than 0 and less than or equal to a first voltage threshold when it detects that the active protection switch has not been effectively disconnected. In this solution, by controlling the input voltage to be greater than 0 and less than or equal to the first voltage threshold, the DC-DC converter circuit is in a state close to a short circuit but not actually short-circuited. This not only reduces the reverse current flowing through the photovoltaic module but also maintains the output voltage of the DC-DC converter circuit at a certain value, facilitating the supply of power to the load within the photovoltaic inverter (the load may include a heat dissipation device that operates under electrical drive to maintain the heat dissipation performance of the photovoltaic inverter). This eliminates the need for an additional power supply to the photovoltaic inverter, thereby simplifying the design and reducing costs.

[0014] In one implementation of the first aspect, the controller is used to control the DC-DC converter circuit to generate a target output voltage, such that the input voltage of the DC-DC converter circuit is greater than 0 and less than or equal to a first voltage threshold. This solution controls the output voltage of the DC-DC converter circuit, thereby adjusting the input voltage of the DC-DC converter circuit. It is relatively simple in design and has good mass production capabilities.

[0015] In one implementation of the first aspect, the controller keeps the switching devices of the DC-DC converter circuit normally on when it detects that the active protection switch has not been effectively disconnected. In this scheme, the DC-DC converter circuit can be in a short-circuit state, and the input voltage of the DC-DC converter circuit can be reduced to 0. This scheme, by keeping the DC-DC converter circuit in a short-circuit state, can reduce the reverse current flowing through the photovoltaic unit.

[0016] In one implementation of the first aspect, the controller is further configured to issue a disconnection command to the active protection switch when the reverse current of the photovoltaic module is greater than or equal to a current threshold and the input voltage of the DC-DC converter circuit is less than a fourth voltage threshold; or, the controller is configured to issue a disconnection command to the active protection switch when the reverse current of the photovoltaic module is greater than or equal to a current threshold, the input voltage of the DC-DC converter circuit is greater than or equal to a fourth voltage threshold, and when it is detected that the reverse current is greater than the current threshold after a set time.

[0017] In this scheme, the controller can determine the fault scenario based on the reverse current and the input voltage. When the input voltage is less than the fourth voltage threshold, the controller determines that a polarity reversal fault has occurred. At this time, the controller sends a trip command to the active protection switch to execute the trip protection action to reduce the reverse current. When the input voltage is greater than or equal to the fourth voltage threshold, the controller determines that an open-circuit voltage inconsistency fault has occurred. At this time, the controller can determine the waiting time and continuously monitor the reverse current during the waiting time. If the controller detects that the reverse current has not disappeared after the waiting time has elapsed, it will perform the trip protection action.

[0018] This solution can identify different fault scenarios based on reverse current and input voltage, and take different protection actions for different fault scenarios.

[0019] The controller is used to adjust the input voltage of the DC-DC converter circuit to be less than or equal to the first voltage threshold when the reverse current of the photovoltaic module is greater than or equal to the current threshold and the input voltage of the DC-DC converter circuit is greater than or equal to the third voltage threshold, and to issue a disconnection command to the active protection switch, wherein the third voltage threshold is greater than the first voltage threshold.

[0020] In this scheme, when the controller determines that the input voltage is greater than or equal to the third voltage threshold, the voltage difference across the contacts of the active protection switch will be large. This may cause arcing when the active protection switch disconnects, leading to contact sticking and preventing the active protection switch from disconnecting successfully. Therefore, when the controller determines that the input voltage is greater than or equal to the third voltage threshold, the input voltage is reduced to less than or equal to the first voltage threshold. After the input voltage is reduced, a disconnection command is issued to control the active protection switch to disconnect. Reducing the input voltage to this first voltage threshold reduces the voltage difference across the contacts of the active protection switch, decreases the arcing energy, and facilitates successful disconnection of the active protection switch.

[0021] In one implementation of the first aspect, the photovoltaic system includes a current sensor for detecting the reverse current of the photovoltaic unit and sending the magnitude of the reverse current to the controller; and / or, the photovoltaic system includes a voltage sensor for detecting the input voltage of the DC-DC converter circuit and sending the detection result to the controller. In this solution, the use of sensors simplifies the circuit design.

[0022] In one implementation of the first aspect, the load includes a DC-AC converter circuit, the output of which is connected to the power grid. The photovoltaic system of this solution can be connected to the power grid, and because the photovoltaic system can reliably eliminate reverse current, it can prevent faults in the photovoltaic system from propagating to the power grid.

[0023] Secondly, this application provides a circuit protection method for a photovoltaic system. The photovoltaic system includes an active protection switch, a DC-DC converter circuit, and a controller. One end of the active protection switch is connected to the photovoltaic module, and the other end is connected to the input terminal of the DC-DC converter circuit. The output terminal of the DC-DC converter circuit is connected to a load. The circuit protection method includes: when the reverse current of the photovoltaic module is greater than or equal to a current threshold, issuing a disconnection command to the active protection switch according to the input voltage of the DC-DC converter circuit, the disconnection command being used to trigger the active protection switch to disconnect; when the active protection switch fails to disconnect effectively within a preset time after issuing the disconnection command, adjusting the input voltage of the DC-DC converter circuit to be less than or equal to a first voltage threshold.

[0024] The circuit protection method in this solution can further determine the fault scenario by checking the input voltage of the DC-DC converter circuit when reverse current is detected. After determining the fault scenario, circuit protection can be implemented by disconnecting the active protection switch. When the active protection switch fails to trip, further protection measures—reducing the input voltage of the DC-DC converter circuit—can eliminate the reverse current in the photovoltaic system, preventing burnout and fault propagation, thereby improving the safety and reliability of the photovoltaic system.

[0025] In one implementation of the second aspect, "detecting that the active protection switch has not been effectively disconnected" includes: detecting that the current in the DC-DC converter circuit is greater than or equal to a critical value. This solution can determine whether the active protection switch has been effectively disconnected by detecting the current in the DC-DC converter circuit. It is simple in design, easy to mass-produce, and has high reliability.

[0026] In one implementation of the second aspect, "detecting that the active protection switch is not effectively disconnected" includes: adjusting the input voltage of the DC-DC converter circuit to be greater than 0 and less than or equal to a first voltage threshold; and detecting that the current of the DC-DC converter circuit is greater than or equal to a critical value.

[0027] In this solution, by controlling the input voltage to a level greater than 0 and less than or equal to the first voltage threshold, the DC-DC converter circuit is in a state close to a short circuit but not actually short-circuited. This not only detects whether the active protection switch is effectively disconnected, but also maintains the output voltage of the DC-DC converter circuit at a certain value, so as to supply power to the load in the photovoltaic inverter (the load may include a heat dissipation device, which can operate under electric power to maintain the heat dissipation performance of the photovoltaic inverter). This eliminates the need for an additional power supply to the photovoltaic inverter, thereby simplifying the design and reducing costs.

[0028] In one implementation of the second aspect, "detecting that the active protection switch has not been effectively disconnected" includes: keeping the switching devices of the DC-DC converter circuit normally on; and detecting that the current of the DC-DC converter circuit is greater than or equal to a critical value. This solution has simple judgment logic, is easy to mass-produce, and has high reliability.

[0029] In one implementation of the second aspect, "detecting that the active protection switch has not been effectively disconnected" includes: detecting that the contact position feedback signal generated by the active protection switch is the target signal. The circuit design and judgment logic of this solution are relatively simple, easy to mass-produce, and have high reliability.

[0030] In one implementation of the second aspect, "detecting that the active protection switch has not been effectively disconnected" includes: detecting that the input voltage of the DC-DC circuit is greater than or equal to a second voltage threshold. This solution can determine whether the active protection switch has been effectively disconnected by detecting the input voltage of the DC-DC converter circuit. It is simple in design, easy to mass-produce, and has high reliability.

[0031] In one implementation of the second aspect, "adjusting the input voltage of the DC-DC converter circuit to be less than or equal to a first voltage threshold" includes: adjusting the input voltage of the DC-DC converter circuit to be greater than 0 and less than or equal to the first voltage threshold.

[0032] In this solution, by controlling the input voltage to a level greater than 0 and less than or equal to the first voltage threshold, the DC-DC converter circuit is in a state close to a short circuit but not actually short-circuited. This not only reduces the reverse current flowing through the photovoltaic module but also maintains the output voltage of the DC-DC converter circuit at a certain value, so as to supply power to the load in the photovoltaic inverter (the load may include a heat dissipation device that can operate under electric power to maintain the heat dissipation performance of the photovoltaic inverter). This eliminates the need for an additional power supply to the photovoltaic inverter, thereby simplifying the design and reducing costs.

[0033] In one implementation of the second aspect, "adjusting the input voltage of the DC-DC converter circuit to be greater than 0 and less than or equal to a first voltage threshold" includes: controlling the DC-DC converter circuit to generate a target output voltage so that the input voltage of the DC-DC converter circuit is greater than 0 and less than or equal to the first voltage threshold. This solution adjusts the input voltage of the DC-DC converter circuit by controlling its output voltage, resulting in a relatively simple design and good mass production feasibility.

[0034] In one implementation of the second aspect, "adjusting the input voltage of the DC-DC converter circuit to be less than or equal to a first voltage threshold" includes: controlling the switching devices of the DC-DC converter circuit to remain normally on. In this scheme, the DC-DC converter circuit can be in a short-circuit state, and the input voltage of the DC-DC converter circuit can be reduced to 0. This scheme, by keeping the DC-DC converter circuit in a short-circuit state, can reduce the reverse current flowing through the photovoltaic unit.

[0035] In one implementation of the second aspect, "issuing a disconnection command to the active protection switch based on the input voltage of the DC-DC converter circuit" includes: detecting whether the input voltage of the DC-DC converter circuit is greater than or equal to a fourth voltage threshold; when the input voltage is less than the fourth voltage threshold, issuing a disconnection command to the active protection switch; when the input voltage is greater than or equal to the fourth voltage threshold, and when it is detected that the reverse current is greater than the current threshold after a set time, issuing a disconnection command to the active protection switch.

[0036] In this scheme, the fault scenario can be determined based on the reverse current and the input voltage. When the input voltage is less than the fourth voltage threshold, a polarity reversal fault is identified. In this case, a tripping command is sent to the active protection switch to execute the tripping protection action and reduce the reverse current. When the input voltage is greater than or equal to the fourth voltage threshold, an open-circuit voltage inconsistency fault is identified. In this case, a waiting time can be determined, and the reverse current is continuously monitored during the waiting time. If the reverse current persists even after the waiting time has elapsed, the tripping protection action is initiated. This scheme can identify different fault scenarios based on the reverse current and the input voltage, and take different protection actions for different fault scenarios.

[0037] In one implementation of the second aspect, "issuing a disconnection command to the active protection switch" includes: detecting whether the input voltage of the DC-DC converter circuit is greater than or equal to a third voltage threshold, wherein the third voltage threshold is greater than a first voltage threshold; when the input voltage is greater than or equal to the third voltage threshold, adjusting the input voltage of the DC-DC converter circuit to be less than or equal to the first voltage threshold, and issuing a disconnection command to the active protection switch; when the input voltage is less than the third voltage threshold, issuing a disconnection command to the active protection switch.

[0038] In this scheme, when the controller determines that the input voltage is greater than or equal to the third voltage threshold, the voltage difference across the contacts of the active protection switch will be large. This may cause arcing when the active protection switch disconnects, leading to contact sticking and preventing the active protection switch from disconnecting successfully. Therefore, when the controller determines that the input voltage is greater than or equal to the third voltage threshold, the input voltage is reduced to less than or equal to the first voltage threshold. After the input voltage is reduced, a disconnection command is issued to control the active protection switch to disconnect. Reducing the input voltage to this first voltage threshold reduces the voltage difference across the contacts of the active protection switch, decreases the arcing energy, and facilitates successful disconnection of the active protection switch. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the circuit framework structure of the photovoltaic system according to an embodiment of this application;

[0040] Figure 2 This is a schematic diagram of the circuit frame structure representing a reverse polarity connection fault;

[0041] Figure 3 This is a schematic diagram of the circuit framework structure representing an open-circuit voltage inconsistency fault;

[0042] Figure 4 This is an overall flowchart of the circuit protection method according to an embodiment of this application;

[0043] Figure 5 yes Figure 4 The flowchart of the fault detection scenario section of the circuit protection method in the paper;

[0044] Figure 6 yes Figure 4 The flowchart of the circuit protection method for disconnecting the protection section;

[0045] Figure 7 yes Figure 4 The flowchart of the redundant protection part of the circuit protection method in the image;

[0046] Figure 8 This indicates the current situation after applying the circuit protection method of the embodiments of this application to a photovoltaic system that has a reverse polarity connection fault;

[0047] Figure 9 This indicates the current situation after applying the circuit protection method of the embodiments of this application to a photovoltaic system that has an open-circuit voltage inconsistency fault. Detailed Implementation

[0048] The terms "first," "second," and various numerical designations used in the embodiments of this application are merely for descriptive convenience and are not intended to limit the scope of protection of this application. The term "and / or" in this document simply describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone.

[0049] A photovoltaic (PV) system is a power generation system that directly converts solar energy into electrical energy using photovoltaic modules. It can include PV strings, batteries, controllers, and PV inverters. A PV module is a single, indivisible assembly of photovoltaic cells capable of providing direct current (DC) output. A PV string consists of multiple PV modules connected in series and / or parallel.

[0050] Figure 1 This illustration shows the frame structure of a photovoltaic system 10 according to an embodiment of this application. For example... Figure 1 As shown, the photovoltaic system 10 may include a plurality of photovoltaic units 101 and a photovoltaic inverter 11, with the photovoltaic units 101 connected in parallel to the photovoltaic inverter 11. The photovoltaic inverter 11 may include a plurality of branch current sensors 102, an active protection switch 103, a combining current sensor 104, an input voltage sensor 105, a DC-DC converter circuit 106, an output voltage sensor 107, a DC-AC converter circuit 108, and a controller 109. In other embodiments, the photovoltaic inverter 11 may also be considered a photovoltaic system, and the photovoltaic units 101 may not be devices in the photovoltaic system 10, but the photovoltaic units 101 are connected to the photovoltaic system (referring to the photovoltaic inverter 11). The photovoltaic unit 101 may be a single component connected in series or in parallel. The photovoltaic units 101 are shown in parallel in this figure. In some embodiments, they can also be connected in series. The specific connection method of the photovoltaic units 101 is not the specific implementation method of this application. Those skilled in the art can combine multiple photovoltaic modules in series and parallel according to the input requirements of the photovoltaic inverter 11 to obtain the required input voltage.

[0051] like Figure 1 As shown, photovoltaic unit 101 can be designated as PV. Photovoltaic unit 101 can be the photovoltaic string mentioned above, or a photovoltaic array formed by several photovoltaic strings connected in parallel. In some embodiments, it can also be a single photovoltaic module. The number of photovoltaic units 101 can be configured as needed, and can be at least one. Figure 1 Multiple photovoltaic units 101 are schematically drawn, and the multiple photovoltaic units 101 are connected in parallel to form multiple branches.

[0052] like Figure 1As shown, each photovoltaic unit 101 is connected in series with an active protection switch 103, and the other end of the active protection switch 103 is connected in parallel to the input terminal of the DC-DC converter circuit 106, thereby enabling multiple photovoltaic units 101 to be connected to the input terminal of the DC-DC converter circuit 106 through the active protection switch 103.

[0053] Indicatively, there may be only one active protection switch 103. The active protection switch 103 has a built-in motion mechanism and multiple contacts. Each photovoltaic unit 101 is connected to a corresponding set of contacts within the active protection switch 103. The motion mechanism can control multiple contacts to operate simultaneously, enabling all photovoltaic units 101 to be connected to or disconnected from the active protection switch 103 at the same time. The active protection switch 103 has active disconnection capabilities, capable of actively disconnecting the circuit based on information such as current and voltage. The active protection switch 103 can be, for example, a DC trip switch or a DC circuit breaker.

[0054] like Figure 1 As shown, the number of branch current sensors 102 is consistent with the number of photovoltaic units 101, with one branch current sensor 102 corresponding to one photovoltaic unit 101. The branch current sensor 102 can be connected in series with the photovoltaic unit 101 and is located in the branch where the photovoltaic unit 101 is located. For example, the branch current sensor 102 can be located between the parallel connection point of the active protection switch 103 (i.e., the parallel connection position of multiple contacts of the active protection switch 103, which is connected to the input terminal of the DC-DC converter circuit 106) and the photovoltaic unit 101. The branch current sensor 102 is used to detect the current (which can be called the branch current) of the photovoltaic unit 101 connected in series with it. The branch currents detected by each branch current sensor 102 can be sequentially labeled as Idc1, Idc2…Idcn.

[0055] like Figure 1 As shown, the combining current sensor 104 can be connected in series with the parallel point of the active protection switch 103, and can be located between this parallel point and the DC-DC converter circuit 106. The combining current sensor 104 is used to detect the total current (which can be called the combining current) after all photovoltaic units 101 are connected in parallel. The combining current detected by the combining current sensor 104 can be denoted as Idc.

[0056] like Figure 1 As shown, the input voltage sensor 105 can be located at the input terminal of the DC-DC converter circuit 106, for example, between the parallel point of the active protection switch 103 and the DC-DC converter circuit 106. The input voltage sensor 105 is used to detect the input voltage of the DC-DC converter circuit 106. The input voltage detected by the input voltage sensor 105 can be denoted as Vin. This input voltage is also equal to the voltage across the photovoltaic unit 101 in each branch.

[0057] like Figure 1 As shown, the output voltage sensor 107 can be located at the output terminal of the DC-DC converter circuit 106 and is used to detect the output voltage of the DC-DC converter circuit 106. The output terminal of the DC-DC converter circuit 106 can be connected to the DC-AC converter circuit 108 through a DC bus (labeled BUS), so the output voltage detected by the output voltage sensor 107 can be labeled Vbus.

[0058] In this embodiment, the DC-DC converter circuit 106 can be a standalone device, such as a DC-DC converter. Alternatively, the DC-DC converter circuit 106 can be a circuit module in the system.

[0059] like Figure 1 As shown, the DC-AC converter circuit 108 can be connected to the output terminal of the DC-DC converter circuit 106 and the AC power grid. Thus, the photovoltaic system 10 can input the converted electrical energy into the AC power grid.

[0060] For the DC-DC converter circuit 106, both the DC-AC converter circuit 108 and the AC power grid can be referred to as AC loads, meaning the output terminal of the DC-DC converter circuit 106 is connected to an AC load. In this embodiment, the load, in addition to the AC loads mentioned above, can also be other DC-DC conversion devices, energy storage devices (such as batteries), or other DC loads. Therefore, in summary, the output terminal of the DC-DC converter circuit 106 is connected to a load, which includes, but is not limited to, AC loads such as the DC-AC converter circuit 108 and the AC power grid, as well as other DC loads such as DC-DC conversion devices and energy storage devices.

[0061] In this embodiment, the DC-AC conversion circuit 108 can be a standalone device, such as a DC-AC converter. Alternatively, the DC-AC conversion circuit 108 can be a circuit module within the system.

[0062] In this embodiment, the DC-DC converter 106 and the DC-AC converter 108 can be components of a photovoltaic inverter. This photovoltaic inverter has a two-stage architecture, with the DC-DC converter 106 as the front-end and the DC-AC converter 108 as the rear-end. In other embodiments, the photovoltaic system may not include the DC-AC converter 108. For example, when the DC-DC converter 106 is connected to a DC load, the photovoltaic system may not have the DC-AC converter 108. In such a photovoltaic system without the DC-AC converter 108, there is no photovoltaic inverter.

[0063] like Figure 1As shown, the controller 109 can be electrically connected to each branch current sensor 102, active protection switch 103, combined current sensor 104, input voltage sensor 105, DC-DC converter circuit 106, and output voltage sensor 107 to acquire their detected signals, determine their operating status, and control their operation. The controller 109 can coordinate the operation of each component according to the functional requirements of the instructions, and is the nerve center and command center of the photovoltaic system 10 (to be further described below).

[0064] In one embodiment, the controller 109 may consist of components such as an instruction register (IR), a program counter (PC), and an operation controller (OC). The controller 109 may refer to one or more devices, circuits, and / or a processing core for processing data (e.g., computer program instructions).

[0065] In other embodiments, the controller 109 may be a single processor or a collective term for multiple processing elements. The processor may be a general-purpose central processing unit (CPU) or an application-specific integrated circuit (ASIC). Alternatively, the processor may be one or more integrated circuits used to control the execution of programs according to the present application, such as one or more digital signal processors (DSPs); or one or more field-programmable gate arrays (FPGAs).

[0066] In the above embodiments, sensors such as branch current sensor 102, combiner current sensor 104, input voltage sensor 105, and output voltage sensor 107 are used. This allows for flexible selection of sensors with corresponding sampling current or sampling voltage ranges according to the PV specifications, enabling flexible deployment and construction of the photovoltaic system 10. In other embodiments, the sampling function of sensors such as branch current sensor 102, combiner current sensor 104, input voltage sensor 105, and output voltage sensor 107 can also be implemented by integrating them into the controller's sampling circuit. In this case, there is no need to additionally arrange sensors such as branch current sensor 102, combiner current sensor 104, input voltage sensor 105, and output voltage sensor 107, which simplifies the circuit.

[0067] In the above embodiment, the photovoltaic inverter 11 includes a branch current sensor 102, an active protection switch 103, a combining current sensor 104, an input voltage sensor 105, a DC-DC converter circuit 106, an output voltage sensor 107, a DC-AC converter circuit 108, and a controller 109. This is merely an example. In other embodiments, the photovoltaic inverter may include a DC-DC converter circuit and a DC-AC converter circuit, but at least one of the branch current sensor 102, active protection switch 103, combining current sensor 104, input voltage sensor 105, output voltage sensor 107, and controller 109 is not built into it. That is, at least one of the branch current sensor 102, active protection switch 103, combining current sensor 104, input voltage sensor 105, output voltage sensor 107, and controller 109 can be independent of the photovoltaic inverter.

[0068] The circuit framework structure of photovoltaic system 10 has been described above. The working principle of photovoltaic system 10 will be explained in detail below.

[0069] When the photovoltaic units 101 in the photovoltaic system 10 are operating, if a photovoltaic unit 101 in one branch fails, the current from the photovoltaic units 101 in the other normal branches will flow to the photovoltaic units 101 in the faulty branch, causing a reverse current in the faulty branch. If the reverse current does not exceed the current threshold, no protection action is required because the photovoltaic unit 101 has a certain current tolerance capability. If the reverse current is greater than or equal to the current threshold, protection action is required to prevent the photovoltaic unit 101 from burning out.

[0070] refer to Figure 1 As shown, the branch current sensor 102 can detect the current of the photovoltaic unit 101 and send the detection result to the controller 109. The controller 109 judges the detection result and can determine whether the reverse current is greater than or equal to the current threshold.

[0071] Typically, two types of faults can cause large reverse currents: one is reversed polarity of photovoltaic unit 101, and the other is inconsistent open-circuit voltage of photovoltaic unit 101. These will be explained separately below.

[0072] Figure 2 This illustrates a fault scenario where a large reverse current occurs due to reverse polarity connection of photovoltaic unit 101. The diagram schematically shows the circuit connections of five photovoltaic units 101 to the photovoltaic inverter 11. Figure 2As shown, five photovoltaic (PV) units 101 are connected in parallel to a PV inverter 11. The polarities of the first four PV units 101 are correctly connected to the polarities of the PV inverter 11 (positive to positive, negative to negative). The polarities of the fifth PV unit 101 are reversed (negative to positive, positive to negative). Let the current in each of the first four PV units 101 be denoted as Idc. Because the polarity of the fifth PV unit 101 is reversed, it is short-circuited. Therefore, the current from the first four PV units 101 flows into the fifth PV unit 101 (this current is called reverse current, which can be 4 * Idc), and does not flow into the PV inverter 11 (this phenomenon is called reverse current). Thus, the current direction in the fifth PV unit 101 is opposite to that of the first four PV units 101, and the current in the fifth PV unit 101 is larger. This is the reverse current fault caused by the reverse polarity connection.

[0073] For reverse current faults caused by reverse polarity connection, combined with Figure 1 As shown, the input voltage detected by the input voltage sensor 105 is relatively small.

[0074] Figure 3 This illustrates a fault scenario where inconsistent open-circuit voltages of photovoltaic units 101 lead to a large reverse current. The diagram schematically shows the circuit connections between the five photovoltaic units 101 and the photovoltaic inverter 11. Figure 3 As shown, five photovoltaic units 101 are connected in parallel to the photovoltaic inverter 11, and the polarity of each photovoltaic unit 101 is correctly connected to the polarity of the photovoltaic inverter 11. However, the number of photovoltaic units connected in series in the first four photovoltaic units 101 is the same, making the open-circuit voltage of the first four photovoltaic units 101 the same (open-circuit voltage is the voltage when the branch is open and no current is output); the number of photovoltaic units connected in series in the fifth photovoltaic unit 101 is less than the number of photovoltaic units connected in series in the other photovoltaic units 101, that is, the fifth photovoltaic unit 101 has the fewest photovoltaic units connected in series. This causes the current of the photovoltaic units 101 in the first four branches to flow into the fifth photovoltaic unit 101 (this current is called reverse current, and the reverse current can depend on the difference between the open-circuit voltage of the photovoltaic units 101 in the first four branches and the fifth photovoltaic unit 101), and will not flow into the photovoltaic inverter 11 (current backflow phenomenon occurs). Therefore, the current direction of the fifth photovoltaic unit 101 is opposite to that of the first four photovoltaic units 101, and the current of the fifth photovoltaic unit 101 is larger. This is the reverse current fault caused by the inconsistent open circuit voltage.

[0075] For reverse current faults caused by inconsistent open-circuit voltages, combined with Figure 1As shown, the input voltage detected by the input voltage sensor 105 is relatively large. Therefore, for a reverse current fault with reverse polarity and a reverse current fault with inconsistent open circuit voltage, the input voltage corresponding to the former fault is less than the input voltage corresponding to the latter fault.

[0076] The photovoltaic system 10 of this embodiment can detect reverse current, determine the fault scenario corresponding to the reverse current, and take corresponding actions for different fault scenarios, thereby reducing or eliminating the reverse current, preventing the faulty photovoltaic unit 101 from being burned out, preventing the fault from spreading, and ultimately improving the safety and reliability of the photovoltaic system. A detailed description will follow.

[0077] like Figure 4 As shown, this embodiment provides a circuit protection method 20 for a photovoltaic system, which can be applied to a photovoltaic system 10. The circuit protection method 20 may include the following functional parts: detecting fault scenarios, performing disconnection protection, and performing redundancy protection. These will be described in detail below.

[0078] Figure 5 A flowchart illustrating the fault detection scenario can be provided. For example... Figure 5 As shown, the fault detection scenario section may include the following steps:

[0079] 201: Detect whether the reverse current is greater than or equal to the current threshold;

[0080] If the reverse current is less than the current threshold, return to step 201; if the reverse current is greater than or equal to the current threshold, proceed to step 202.

[0081] 202: Detect whether the input voltage of the DC-DC converter circuit is greater than or equal to the fourth voltage threshold;

[0082] When the input voltage is less than the fourth voltage threshold, proceed to step 203; when the input voltage is greater than or equal to the fourth voltage threshold, proceed to step 204.

[0083] 203: Perform disconnection protection;

[0084] 204: Determine the waiting time and check whether the reverse current is greater than or equal to the current threshold after the waiting time has elapsed;

[0085] If the reverse current is less than the current threshold after the waiting period, proceed to step 201; if the reverse current is greater than or equal to the current threshold after the waiting period, proceed to step 203.

[0086] In step 201, combined Figure 1As shown, the controller 109 can control the current sensors 102 of each branch to detect the current in each branch, and determine whether a reverse current greater than or equal to a current threshold appears in each branch based on the detection results of the current sensors 102. The current threshold can be determined according to the current withstand capability of the photovoltaic unit 101; for example, the current threshold can be less than or equal to the current withstand value of the photovoltaic unit 101. Figure 5 As shown, when the judgment result of step 201 is YES, it indicates that a fault has occurred in a branch that requires protection action. When the judgment result of step 201 is NO, it indicates that there is no reverse current or the reverse current does not exceed the current withstand value, and there is no need to immediately perform protection action.

[0087] Combination Figure 1 As shown, when the controller 109 detects a reverse current greater than or equal to the current threshold, the controller 109 can control the input voltage sensor 105 to detect the input voltage of the DC-DC converter circuit 106, and determine whether the input voltage is greater than or equal to the fourth voltage threshold based on the detection result of the input voltage sensor 105. The fourth voltage threshold can be determined according to the configuration of the photovoltaic unit 101, and it can be equal to the upper limit of the voltage exhibited by the photovoltaic unit 101 when it generates reverse current. As explained above, the input voltage corresponding to inconsistent open-circuit voltage is larger, and the input voltage corresponding to reverse polarity is smaller. Therefore, if the judgment result of step 202 is YES, indicating that the fault is inconsistent open-circuit voltage, then step 204 is executed; if the judgment result of step 202 is NO, indicating that the fault is reverse polarity, then step 203 is executed.

[0088] In step 203, combined Figure 1 As shown, when the controller 109 determines that the fault scenario is a reverse polarity connection, the controller 109 can perform a disconnection protection action. The execution of the disconnection protection action will be further explained below.

[0089] In step 204, combined Figure 1As shown, when controller 109 determines that the fault scenario is an open-circuit voltage inconsistency, controller 109 can determine the waiting time and continuously detect the reverse current within the waiting time. Controller 109 can calculate this waiting time based on a built-in strategy. Based on this strategy, a larger reverse current corresponds to a shorter waiting time, and a smaller reverse current corresponds to a longer waiting time. If controller 109 detects that the reverse current has not disappeared after the waiting time, it performs a trip protection action; if controller 109 detects that the reverse current has disappeared after the waiting time, it returns to step 201. Specifically, the reverse current may disappear when the voltage of the photovoltaic system 10 during grid-connected operation drops to within the maximum power point tracking (MPPT) window (in the PV curve, the voltage range corresponding to the maximum power point is determined, which can be called the MPPT window), or when the shadow of the shading photovoltaic unit 101 disappears.

[0090] As described above, the fault scenario detection part of the circuit protection method 20 can identify different fault scenarios based on the reverse current and input voltage, and take different protection actions for different fault scenarios.

[0091] Figure 6 A flowchart illustrating the segmentation and protection process can be provided. For example... Figure 6 As shown, the disconnection protection section may include the following steps:

[0092] 301: Detect whether the input voltage of the DC-DC converter circuit is greater than or equal to the third voltage threshold, and the third voltage threshold is greater than the first voltage threshold;

[0093] When the input voltage is greater than or equal to the third voltage threshold, step 302 is executed, and then step 303 is executed; when the input voltage is less than the third voltage threshold, step 303 is executed.

[0094] Step 302: Reduce the input voltage to less than or equal to the first voltage threshold. Step 303: Issue a disconnect command.

[0095] If the input voltage of the DC-DC converter circuit 106 is too high, the voltage difference across the contacts of the active protection switch 103 will be large, potentially causing arcing when the active protection switch 103 disconnects. The arcing energy may cause the contacts of the active protection switch 103 to stick together, preventing the active protection switch 103 from successfully disconnecting. Therefore, the solution in this embodiment detects the input voltage and performs corresponding protection actions based on the detection results. This will be explained below.

[0096] In step 301, combined Figure 1As shown, the controller 109 can control the input voltage sensor 105 to detect the input voltage of the DC-DC converter circuit 106, and determine whether the input voltage is greater than or equal to a third voltage threshold based on the detection result of the input voltage sensor 105. The third voltage threshold is related to the specifications of the active protection switch 103 and can be determined according to the breaking capacity of the active protection switch 103. For example, the third voltage threshold can be equal to the upper limit of the operating voltage of the active protection switch 103. The third voltage threshold is independent of the fourth voltage threshold mentioned above, and the third voltage threshold can be greater than the first voltage threshold described below.

[0097] Combination Figure 1 As shown, when the controller 109 determines that the input voltage is greater than or equal to the third voltage threshold, the controller 109 reduces the input voltage to less than or equal to the first voltage threshold, and after the input voltage is reduced, issues a disconnection command to control the active protection switch 103 to disconnect. The first voltage threshold can be determined according to the configuration of the photovoltaic unit 101. For example, the first voltage threshold can be less than, equal to, or greater than the lower limit of the voltage exhibited externally when the photovoltaic unit 101 generates reverse current. Schematic, the first voltage threshold and this lower limit can differ slightly. The first voltage threshold is less than the third voltage threshold. In this embodiment, reducing the input voltage to the first voltage threshold can reduce the voltage difference across the contacts of the active protection switch 103, reduce arcing energy, and facilitate the smooth disconnection of the active protection switch 103.

[0098] Combination Figure 1 As shown, when the controller 109 determines that the input voltage is less than the third voltage threshold, the controller 109 can directly issue a disconnection command to control the active protection switch 103 to disconnect.

[0099] As described above, the disconnection protection section in circuit protection method 20 can control the active protection switch 103 to disconnect after determining the fault scenario, thereby cutting off the DC energy input, eliminating reverse current, preventing fault propagation, and ultimately improving the safety and reliability of the photovoltaic system.

[0100] In this embodiment, if the active protection switch 103 fails to disconnect the circuit due to mechanical failure or other reasons, the circuit protection method 20 can continue to provide redundant protection to ensure that the fault is eliminated.

[0101] Figure 7 A flowchart illustrating the redundancy protection process can be provided. For example... Figure 7 As shown, the redundancy protection section may include the following steps:

[0102] 304: After a preset time has elapsed since the disconnection command was issued, the status of the active protection switch is checked;

[0103] 305: Determine whether the active protection switch has been effectively disconnected;

[0104] 306: When the active protection switch fails to disconnect effectively, the input voltage of the DC-DC converter circuit will be reduced to less than or equal to the first voltage threshold.

[0105] The active protection switch 103 requires a certain amount of time to perform its disconnection action; therefore, in steps 304 and 305, in combination with... Figure 1 As shown, the controller 109 can determine whether the active protection switch 103 has been effectively disconnected based on the state of the active protection switch 103 after a preset time. Indicatively, this embodiment can achieve the state determination of the active protection switch 103 through the following implementation method.

[0106] In Embodiment 1, the controller 109 can send a current control signal to the DC-DC converter circuit 106, causing the DC-DC converter circuit 106 to generate current. This current can be continuous for a certain duration (i.e., the current value is never zero) or intermittent for a certain duration (i.e., the current is intermittent, similar to a pulse). The current value can be fixed or variable. The controller 109 can also detect this current in the DC-DC converter circuit 106 through the combining current sensor 104. When the controller 109 detects that the current is greater than or equal to a threshold value, the controller 109 determines that the active protection switch 103 has not been effectively disconnected. This threshold value can be determined according to actual conditions; for example, the threshold value can be a small non-zero value determined considering the drift of current detection accuracy.

[0107] The detection principle of Implementation Method 1 is as follows: If the active protection switch 103 is effectively disconnected, the circuit is open, the combining current sensor 104 cannot respond to the current control signal of the controller 109, and the current detected by the combining current sensor 104 is 0. Conversely, if the active protection switch 103 is not effectively disconnected, the circuit is closed, the combining current sensor 104 can respond to the current control signal of the controller 109, and the current detected by the combining current sensor 104 is positive. Therefore, when the controller 109 detects that the current is greater than or equal to the critical value, it indicates that the active protection switch 103 has not been effectively disconnected.

[0108] Alternatively, in Embodiment 2, the controller 109 can reduce the input voltage of the DC-DC converter circuit 106 to a level greater than 0 and less than or equal to the first voltage threshold. At this level, the input voltage can be relatively small, making the DC-DC converter circuit 106 nearly short-circuited (but not actually short-circuited). Illustratively, the controller 109 can control the DC-DC converter circuit 106 to generate a target output voltage such that the input voltage is greater than 0 and less than or equal to the first voltage threshold. The target output voltage can have any suitable constant voltage value. Then, the controller 109 can also detect the current in the DC-DC converter circuit 106 using the combining current sensor 104. When the controller 109 detects that the current in the DC-DC converter circuit 106 is greater than or equal to a threshold value, the controller 109 determines that the active protection switch 103 has not been effectively disconnected. This threshold value can be determined based on actual conditions; for example, it can be a small non-zero value determined considering the drift in current detection accuracy. The threshold value in Embodiment 2 can be the same as the threshold value in Embodiment 1.

[0109] The detection principle of Implementation Method Two is as follows: If the active protection switch 103 is effectively disconnected, the circuit is open, the combining current sensor 104 cannot respond to the control signal of the controller 109, and the current detected by the combining current sensor 104 is 0. Conversely, if the active protection switch 103 is not effectively disconnected, the circuit is closed, the combining current sensor 104 can respond to the control signal of the controller 109, and the current detected by the combining current sensor 104 is positive. Therefore, when the controller 109 detects that the current is greater than or equal to the critical value, it indicates that the active protection switch 103 has not been effectively disconnected.

[0110] Implementation method two can be considered an alternative to implementation method one, the difference being that implementation method one achieves detection by controlling the current of the DC-DC converter circuit 106, while implementation method two achieves detection by controlling the input voltage of the DC-DC converter circuit 106. Implementation method two controls the input voltage to a level greater than 0 and less than or equal to the first voltage threshold, so that the DC-DC converter circuit 106 is in a state close to a short circuit but not actually short-circuited. This not only detects whether the active protection switch 103 is effectively disconnected, but also maintains the output voltage of the DC-DC converter circuit 106 at a certain value to supply power to the load within the photovoltaic inverter 11 (the load may include a heat dissipation device that can operate under electrical drive to maintain the heat dissipation performance of the photovoltaic inverter 11). This eliminates the need for an additional power supply to the photovoltaic inverter 11, thereby simplifying the design and reducing costs.

[0111] Alternatively, in Embodiment 3, the controller 109 can keep the switching devices in the DC-DC converter circuit 106 constantly on, at which point the DC-DC converter circuit 106 can be in a short-circuit state. Then, the controller 109 can detect the current in the DC-DC converter circuit 106 through the combining current sensor 104. When the controller 109 detects that the current in the DC-DC converter circuit 106 is greater than or equal to a threshold value, the controller 109 determines that the active protection switch 103 has not been effectively disconnected. This threshold value can be determined according to the actual situation; for example, the threshold value can be a small positive value determined considering the drift of the current detection accuracy. The threshold value in Embodiment 3 can be the same as the threshold value in Embodiment 1.

[0112] The detection principle of Implementation Method 3 is as follows: If the active protection switch 103 is effectively disconnected, the circuit is open, and the current detected by the combining current sensor 104 is 0. Conversely, if the active protection switch 103 is not effectively disconnected, the circuit is closed, and the combining current sensor 104 can detect reverse current. Therefore, when the controller 109 detects that the current of the DC-DC converter circuit 106 is greater than or equal to the critical value, it indicates that the active protection switch 103 has not been effectively disconnected.

[0113] Alternatively, in embodiment four, the active protection switch 103 may have a contact position feedback function, and the active protection switch 103 can output a contact position feedback signal. Illustratively, the contact position feedback signal can be a level signal, indicating the position of the contacts in the active protection switch 103, so as to determine whether the active protection switch 103 is open. The controller 109 can detect the contact position feedback signal sent by the active protection switch 103, and determine whether the active protection switch 103 is effectively open based on the contact position feedback signal. Illustratively, when the contact position feedback signal is high (or low), the controller 109 can determine that the active protection switch 103 is in a closed state; when the contact position feedback signal is low (or high), the controller 109 can determine that the active protection switch 103 is in an open state. Alternatively, when the voltage of the contact position feedback signal is in the first interval, the controller 109 can determine that the active protection switch 103 is in the closed state; when the voltage of the contact position feedback signal is in the second interval, the controller 109 can determine that the active protection switch 103 is in the open state. Implementation method four can directly read the operating state of the active protection switch 103, making detection relatively simple.

[0114] Alternatively, in embodiment five, the controller 109 can detect the input voltage of the DC-DC converter circuit 106, and determine that the active protection switch 103 has not been effectively disconnected when the input voltage is greater than or equal to a second voltage threshold. The second voltage threshold can be determined according to the configuration of the photovoltaic unit 101, for example, it can be the minimum voltage required to start the DC-DC converter circuit 106. The second voltage threshold is related to the DC-DC converter circuit 106, but is not related to the aforementioned voltage thresholds.

[0115] The detection principle of Embodiment 5 is as follows: the DC-DC converter 106 can only operate normally when its input voltage reaches the minimum voltage. In other words, when the DC-DC converter 106 is working, it indicates that it has reached the minimum voltage. If the input voltage of the DC-DC converter 106 is detected to be greater than or equal to the second voltage threshold, it indicates that the DC-DC converter 106 has started normally, which further indicates that a photovoltaic unit 101 is connected to the input side of the DC-DC converter 106, and therefore the active protection switch 103 has not been effectively disconnected.

[0116] In step 306, when the controller 109 determines that the active protection switch 103 has not been effectively disconnected, the controller 109 can reduce the input voltage of the DC-DC converter circuit 106 to no higher than the first voltage threshold. At this time, the input voltage can be relatively small, and the reverse current will flow into the DC-DC converter circuit 106, thereby shunting the reverse current, reducing or eliminating the reverse current flowing through the photovoltaic unit 101, and preventing the photovoltaic unit 101 from being burned out.

[0117] Step 306 can be implemented illustratively through the following implementation method, which will be described below.

[0118] In one embodiment, when the controller 109 determines that the active protection switch 103 has not been effectively disconnected, the controller 109 can control the input voltage of the DC-DC converter circuit 106 to be greater than 0 and less than or equal to the first voltage threshold. For example, the controller 109 can control the DC-DC converter circuit 106 to generate a target output voltage so that the input voltage of the DC-DC converter circuit 106 is greater than 0 and less than or equal to the first voltage threshold. The target output voltage can have any suitable constant voltage value. In this embodiment, by controlling the input voltage to be greater than 0 and less than or equal to the first voltage threshold, the DC-DC converter circuit 106 is in a state close to a short circuit but not actually short-circuited. This not only reduces the reverse current flowing through the photovoltaic unit 101 but also maintains the output voltage of the DC-DC converter circuit 106 at a certain value, facilitating the supply of power to the load within the photovoltaic inverter 11 (the load may include a heat dissipation device that operates under electrical drive to maintain the heat dissipation performance of the photovoltaic inverter 11). This eliminates the need for an additional power supply to the photovoltaic inverter 11, thereby simplifying the design and reducing costs.

[0119] In another embodiment, when the controller 109 determines that the active protection switch 103 has not been effectively disconnected, the controller 109 can control the switching devices in the DC-DC converter circuit 106 to remain normally open. At this time, the DC-DC converter circuit 106 can be in a short-circuit state, and the input voltage of the DC-DC converter circuit 106 can be reduced to 0. This embodiment makes the DC-DC converter circuit 106 in a short-circuit state, which can reduce the reverse current flowing through the photovoltaic unit 101.

[0120] Figure 8 This indicates the current status of the photovoltaic system 10 after the circuit protection method 20 is executed in response to a reverse polarity connection fault. For example... Figure 8 As shown, after the redundant protection portion of circuit protection method 20 is executed, most of the reverse current flows into the photovoltaic inverter 11, while only a small amount of reverse current flows through the fifth photovoltaic unit 101 with reversed polarity. (Comparison) Figure 8 and Figure 2 It can be seen that the reverse current in the fifth photovoltaic unit 101 is greatly reduced, and the risk of it being burned out is greatly reduced.

[0121] Figure 9 This indicates the current status of the photovoltaic system 10 after executing circuit protection method 20 in response to an open-circuit voltage inconsistency fault. For example... Figure 9 As shown, after the redundant protection portion of circuit protection method 20 is executed, reverse current flows into photovoltaic inverter 11, and there may be no reverse current in the fifth photovoltaic unit 101. This prevents the fifth photovoltaic unit 101 from burning out.

[0122] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A photovoltaic system, characterized in that, Includes active protection switches, DC-DC converter circuits, and controllers; One end of the active protection switch is used to connect to the photovoltaic module, and the other end is connected to the input terminal of the DC-DC converter circuit. The output terminal of the DC-DC converter circuit is used to connect to the load. The controller is used to issue a disconnection command to the active protection switch to trigger the active protection switch to open when the reverse current of the photovoltaic module is greater than or equal to a current threshold and the input voltage of the DC-DC converter circuit is less than a fourth voltage threshold. If the active protection switch fails to open effectively within a preset time after the disconnection command is issued, the controller adjusts the input voltage of the DC-DC converter circuit to be less than or equal to a first voltage threshold.

2. The photovoltaic system according to claim 1, characterized in that, The controller is used to adjust the input voltage of the DC-DC converter circuit to be greater than 0 and less than or equal to the first voltage threshold when it detects that the active protection switch has not been effectively disconnected.

3. The photovoltaic system according to claim 2, characterized in that, The controller is used to control the DC-DC converter circuit to generate a target output voltage so that the input voltage of the DC-DC converter circuit is greater than 0 and less than or equal to the first voltage threshold.

4. The photovoltaic system according to any one of claims 1-3, characterized in that, The controller is used to keep the switching devices of the DC-DC converter circuit constantly on when it is detected that the active protection switch has not been effectively disconnected.

5. The photovoltaic system according to any one of claims 1-3, characterized in that, The controller is also configured to issue a disconnection command to the active protection switch when the reverse current of the photovoltaic module is greater than or equal to the current threshold, the input voltage of the DC-DC converter circuit is greater than or equal to the fourth voltage threshold, and when it is detected that the reverse current is greater than the current threshold after a set time.

6. The photovoltaic system according to any one of claims 1-3, characterized in that, The controller is configured to adjust the input voltage of the DC-DC converter to be less than or equal to the first voltage threshold when the reverse current of the photovoltaic module is greater than or equal to the current threshold and the input voltage of the DC-DC converter is greater than or equal to the third voltage threshold, and to issue a disconnection command to the active protection switch, wherein the third voltage threshold is greater than the first voltage threshold.

7. The photovoltaic system according to any one of claims 1-3, characterized in that, The load includes a DC-AC converter circuit, and the output terminal of the DC-DC converter circuit is connected to the power grid.

8. A circuit protection method for a photovoltaic system, characterized in that, The photovoltaic system includes an active protection switch, a DC-DC converter circuit, and a controller; one end of the active protection switch is connected to the photovoltaic module, and the other end is connected to the input terminal of the DC-DC converter circuit, the output terminal of the DC-DC converter circuit is connected to the load; the circuit protection method includes: When the reverse current of the photovoltaic module is greater than or equal to the current threshold and the input voltage of the DC-DC converter circuit is less than the fourth voltage threshold, a disconnection command is sent to the active protection switch. The disconnection command is used to trigger the active protection switch to disconnect. If the active protection switch fails to disconnect effectively within a preset time after a disconnection command is issued to it, the input voltage of the DC-DC converter circuit is adjusted to be less than or equal to a first voltage threshold.

9. The circuit protection method according to claim 8, characterized in that, The phrase "adjusting the input voltage of the DC-DC converter circuit to be less than or equal to a first voltage threshold" includes: Adjust the input voltage of the DC-DC converter circuit to be greater than 0 and less than or equal to the first voltage threshold.

10. The circuit protection method according to claim 9, characterized in that, The phrase "adjusting the input voltage of the DC-DC converter circuit to be greater than 0 and less than or equal to the first voltage threshold" includes: The DC-DC converter circuit is controlled to generate a target output voltage so that the input voltage of the DC-DC converter circuit is greater than 0 and less than or equal to the first voltage threshold.

11. The circuit protection method according to any one of claims 8-10, characterized in that, The phrase "adjusting the input voltage of the DC-DC converter circuit to be less than or equal to a first voltage threshold" includes: The switching devices of the DC-DC converter circuit are kept normally on.

12. The circuit protection method according to any one of claims 8-10, characterized in that, The circuit protection method further includes: When the reverse current of the photovoltaic module is greater than or equal to the current threshold, and the input voltage is greater than or equal to the fourth voltage threshold, and when it is detected that the reverse current is greater than the current threshold after a set time, a disconnection command is sent to the active protection switch.

13. The circuit protection method according to any one of claims 8-10, characterized in that, The phrase "issuing a disconnect command to the active protection switch" includes: Detect whether the input voltage of the DC-DC converter circuit is greater than or equal to a third voltage threshold, wherein the third voltage threshold is greater than the first voltage threshold; When the input voltage is greater than or equal to the third voltage threshold, the input voltage of the DC-DC converter circuit is adjusted to be less than or equal to the first voltage threshold, and a disconnection command is sent to the active protection switch; When the input voltage is less than the third voltage threshold, a disconnection command is sent to the active protection switch.

Images