Turn-off device and photovoltaic system

Abstract

The invention discloses a turn-off device and a photovoltaic system, the turn-off device is used for turn-off control of a photovoltaic string, the turn-off device comprises a plurality of assembly turn-off modules and a string turn-off module, the input end of each assembly turn-off module is electrically connected with the output end of a photovoltaic module, and the output ends of the assembly turn-off modules are connected in series and then electrically connected with the input end of a bus of the photovoltaic string. The component turn-off module comprises a first switch, a current detection unit, a second switch and a control unit; the string turn-off module comprises a power supply unit and a third switch, the power supply unit is electrically connected to the bus input end of the photovoltaic string and used for outputting an electric signal to the photovoltaic string, and the third switch is electrically connected between the input end and the output end of the bus and used for controlling the on-off state between the photovoltaic string and an external circuit. According to the turn-off device, component-level turn-off can be achieved through the component turn-off module, and the safety of a photovoltaic string circuit is improved by enabling the first switch to be synchronously turned on and turned off along with the third switch.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic equipment, and in particular to a circuit breaker and a photovoltaic system. Background Art

[0002] A solar photovoltaic power generation system is a power generation system that converts solar radiation energy into electrical energy. It is widely used and is becoming more and more popular because it uses inexhaustible solar energy as energy. A solar photovoltaic power generation system usually consists of several photovoltaic strings and inverter strings, and a photovoltaic string consists of several photovoltaic modules connected in series. A photovoltaic module can consist of a single photovoltaic module or two or more photovoltaic modules connected in series.

[0003] Photovoltaic strings may generate thousands of volts of voltage during power generation. In the prior art, in order to eliminate the high voltage in the circuit from the photovoltaic module to the inverter, a switch is set at the output end of the photovoltaic module, and the operation of the switch is controlled by sending a heartbeat packet to the switch through an external controller, that is, the external controller continuously sends a heartbeat packet to the switch, and the switch remains in the on state when receiving the heartbeat packet, and disconnects the photovoltaic module from the circuit when the heartbeat packet is not received. The defect is that it is necessary to ensure that stable and reliable communication is formed between the switch and the external controller, otherwise it will affect the normal operation of the photovoltaic system, reduce the stability of the system, and the setting distance between the switch and the controller is limited by the communication distance, and the cost is relatively high. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the prior art to a certain extent. To this end, the present invention provides a circuit breaker and a photovoltaic system, which can accurately and quickly control the connection status of photovoltaic strings and photovoltaic modules, have good safety and low cost.

[0005] In a first aspect, to achieve the above-mentioned object, the present invention proposes a circuit breaker for controlling the shutdown of a photovoltaic string, the circuit breaker comprising a plurality of component shutdown modules and a group of string shutdown modules, the input end of the component shutdown module being electrically connected to the output end of the photovoltaic module, the photovoltaic module comprising at least one photovoltaic component, the output ends of the plurality of component shutdown modules being connected in series and then electrically connected to the input end of the busbar of the photovoltaic string, the component shutdown module comprising:

[0006] A first switch, the input end of the first switch is electrically connected to the first output end of the photovoltaic module, and is used to control the on / off state between the photovoltaic module and the busbar of the photovoltaic string;

[0007] a current detection unit, one end of which is electrically connected to the output end of the first switch, and the other end of which is set as the output end of the component shutdown module, for detecting the current value flowing through the line and generating a current detection signal representing the detected current value;

[0008] a second switch, one end of the second switch being electrically connected between the output end of the first switch and the input end of the current detection unit, and the other end of the second switch being electrically connected to the second output end of the photovoltaic module;

[0009] a control unit, electrically connected to the control ends of the first switch and the second switch and the current detection signal output end of the current detection unit, and configured to control the on / off state of the first switch and the second switch according to the numerical range of the detection current value represented by the current detection signal;

[0010] The string shutdown module includes a power supply unit and a third switch. The output end of the power supply unit is electrically connected to the bus input end of the photovoltaic string, and is used to output two electrical signals of different voltages to the photovoltaic string according to the on-off state of the third switch. The third switch is electrically connected between the input and output ends of the bus, and is used to control the on-off state between the photovoltaic string and the external circuit.

[0011] Preferably, the string shutoff module further comprises a trigger, the trigger comprises a signal input terminal and a signal output terminal, the power supply unit comprises an enable signal input terminal, the signal output terminal of the trigger is electrically connected to the enable signal input terminal of the power supply unit and is used to output an enable signal to the power supply unit;

[0012] The trigger is used for outputting enable signals of different level states at the signal output terminal of the trigger when the third switch operates in different on-off states;

[0013] The power supply unit outputs two electrical signals with different voltages according to the level state of the enable signal.

[0014] Preferably, the string shutoff module further comprises a step-down unit and an energy storage battery unit, wherein the step-down unit input end is electrically connected to the bus input end of the photovoltaic string, the output end is electrically connected to the input end of the energy storage battery unit, and the output end of the energy storage battery unit is electrically connected to the input end of the power supply unit;

[0015] The step-down unit is used to charge the energy storage battery unit after stepping down the output voltage of the photovoltaic string;

[0016] The energy storage battery unit is used to supply power to the power supply unit.

[0017] Preferably, the string shutoff module further includes a fourth switch, the on-off state of the fourth switch is synchronized with the on-off state of the third switch, one end of the fourth switch is electrically connected to the reference ground, and the other end is electrically connected to the signal input end of the trigger;

[0018] When the fourth switch is disconnected, the signal output terminal of the trigger outputs a first trigger signal, and the power supply unit outputs a first voltage signal to the photovoltaic string circuit;

[0019] When the fourth switch is turned on, the signal output terminal of the trigger outputs a second trigger signal, and the power supply unit outputs a second voltage signal to the photovoltaic string circuit.

[0020] Preferably, when the power supply unit outputs a first voltage signal to the photovoltaic string circuit, a detection current value represented by a current detection signal output by the current detection unit is less than or equal to a first threshold value;

[0021] When the power supply unit outputs a second voltage signal to the photovoltaic string circuit, a detection current value represented by a current detection signal output by the current detection unit is greater than a first threshold value and less than or equal to a second threshold value.

[0022] Preferably, the control unit controls the first switch to be turned off and controls the second switch to be turned on when the detection current value represented by the current detection signal is less than or equal to a first threshold value;

[0023] The control unit controls the first switch to be turned on and controls the second switch to be turned off when the detection current value represented by the current detection signal is greater than a first threshold value and less than or equal to a second threshold value.

[0024] Preferably, the power supply unit is configured as a bootstrap boost power supply, and the trigger is configured as a monostable trigger.

[0025] Preferably, the current detection unit comprises a measuring resistor and an amplifier circuit whose input end is electrically connected to both ends of the measuring resistor, and the output end of the amplifier circuit is used to output the current detection signal.

[0026] Preferably, the current detection unit includes a Hall current sensor.

[0027] Preferably, a discharge unit is electrically connected between the output ends of the component shutdown module, and the discharge unit is used to quickly release the residual charge in the circuit after the first switch and the second switch are disconnected. The discharge unit includes a fifth switch and a discharge resistor.

[0028] Preferably, the first switch, the second switch and the fifth switch are configured as one of a MOS tube, an IGBT or a relay switch, the control electrode of the fifth switch is electrically connected to the control unit, and the control unit controls the fifth switch to be turned on and off within a preset time while the first switch is turned off, and when the fifth switch is turned on, the second switch is not turned on.

[0029] Preferably, a freewheeling diode is electrically connected between the output ends of the component shutdown module.

[0030] Preferably, the component shutdown module further comprises a power supply unit, the power supply unit draws power from the photovoltaic module and is used to supply power to the control unit, and the input end of the power supply unit is electrically connected to the output end of the photovoltaic module.

[0031] In the second aspect, in order to achieve the above invention purpose, the present invention also provides a photovoltaic system, including a plurality of photovoltaic strings and an inverter, wherein the plurality of photovoltaic strings are connected in parallel to the input end of the inverter, the output end of the inverter is connected to the power grid, the photovoltaic strings include a plurality of photovoltaic modules and a circuit breaker, the circuit breaker is set as the circuit breaker described in any of the above technical solutions, the output ends of the plurality of photovoltaic modules are electrically connected to the input ends of the plurality of component shutdown modules in a one-to-one correspondence, and the photovoltaic modules include at least one photovoltaic component. The photovoltaic system provided in this application has a similar reasoning process to the beneficial effects of the circuit breaker, which will not be repeated here.

[0032] These features and advantages of the present invention will be disclosed in detail in the following specific embodiments and drawings. The best embodiments or means of the present invention will be described in detail in conjunction with the drawings, but they are not intended to limit the technical solutions of the present invention. In addition, there are multiple features, elements, and components that appear in each of the following texts and drawings, and different symbols or numbers are marked for convenience, but they all represent components with the same or similar structures or functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be further described below in conjunction with the accompanying drawings:

[0034] Figure 1 A circuit diagram of a circuit breaker according to an embodiment of the present invention;

[0035] Figure 2 A circuit diagram of another circuit breaker according to an embodiment of the present invention;

[0036] Figure 3 is a schematic diagram of a discharge unit circuit according to an embodiment of the present invention;

[0037] Figure 4 4 is a schematic diagram of a photovoltaic system circuit according to an embodiment of the present invention.

[0038] Description of reference numerals:

[0039] Among them, 10, component shutdown module; 11, control unit; 12, current detection unit; 13, discharge unit; 14, power supply unit; 20, string shutdown module; 21, power supply unit; 22, trigger; 23, step-down unit; 24, energy storage battery unit; 30, photovoltaic module; 40, inverter; K1, first switch; K2, second switch; K3, third switch; K4, fourth switch; K5, fifth switch; D1, freewheeling diode; D3, withstand voltage diode. DETAILED DESCRIPTION

[0040] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments in the implementation manner are intended to be used to explain the present invention and should not be construed as limiting the present invention.

[0041] References in this specification to "one embodiment" or "an example" or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment itself may be included in at least one embodiment of the present patent disclosure. The appearance of the phrase "in one embodiment" in various places in the specification does not necessarily refer to the same embodiment.

[0042] like Figure 1 As shown, a shut-off device is used for shut-off control of a photovoltaic string. The shut-off device includes a plurality of component shut-off modules 10 and a group of string shut-off modules 20. The input end of the component shut-off module 10 is electrically connected to the output end of a photovoltaic module 30. The photovoltaic module 30 includes at least one photovoltaic component. The output ends of the plurality of component shut-off modules 10 are connected in series and then electrically connected to the input end of a busbar of the photovoltaic string. The component shut-off module 10 includes:

[0043] A first switch K1, the input end of the first switch K1 is electrically connected to the first output end of the photovoltaic module 30, and is used to control the on / off state between the photovoltaic module 30 and the busbar of the photovoltaic string;

[0044] A current detection unit 12, one end of which is electrically connected to the output end of the first switch K1, and the other end of which is set as the output end of the component shutdown module 10, for detecting the current value flowing through the line and generating a current detection signal representing the detected current value;

[0045] a second switch K2, one end of the second switch K2 being electrically connected between the output end of the first switch K1 and the input end of the current detection unit 12, and the other end of the second switch K2 being electrically connected to the second output end of the photovoltaic module 30;

[0046] A control unit 11, electrically connected to the control ends of the first switch K1 and the second switch K2 and the current detection signal output end of the current detection unit 12, for controlling the on-off state of the first switch K1 and the second switch K2 according to the numerical range of the detection current value represented by the current detection signal;

[0047] The string shutdown module 20 includes a power supply unit 21 and a third switch K3. The power supply unit 21 is electrically connected to the bus input end of the photovoltaic string and is used to output an electrical signal to the photovoltaic string. The third switch K3 is electrically connected between the input end and the output end of the bus and is used to control the on / off state between the photovoltaic string and the external circuit.

[0048] In this embodiment, the photovoltaic module 30 is set as a photovoltaic component or is composed of two or more photovoltaic components connected in series. After the third switch K3 is turned off, the photovoltaic string bus is disconnected, and the photovoltaic module 30 still has high voltage on the bus input end of the photovoltaic string. The power supply unit 21 cannot output an electrical signal to the photovoltaic string circuit, and no current flows through the current detection unit 12. The control unit 11 receives a current value represented by a current detection signal of zero, and the control unit 11 controls the first switch K1 to turn off and the second switch K2 to turn on. At this time, the photovoltaic module 30 no longer outputs voltage to the circuit, and the power supply unit 21 starts to output voltage to the photovoltaic string circuit. The string circuit outputs an electrical signal, the power supply unit 21 and several series-connected current detection units 12 and several second switches K2 form a loop, a first fixed current flows through the current detection unit 12, after the third switch K3 is turned on, the busbar of the photovoltaic string and the primary circuit of the inverter 40 are turned on, the output current of the power supply unit 21 is shunted, and the current flowing through the current detection unit 12 is less than the first fixed current, then the current detection signal received by the control unit 11 changes, the first switch K1 is controlled to be turned on, the second switch K2 is turned off, and the photovoltaic module 30 outputs direct current to the busbar of the photovoltaic string and the inverter 40. Therefore, the technical solution realizes that the first switch K1 is controlled to be turned off after the third switch K3 is turned off, and the first switch K1 is controlled to be turned on after the third switch K3 is turned on, without the need for an external communication device, so as to prevent the first switch K1 from being turned on when the third switch K3 is turned off and the internal circuit of the photovoltaic string from having continuous high voltage, thereby improving the safety of the photovoltaic system and saving costs.

[0049] Specifically, the control unit 11 controls the first switch K1 to be disconnected and the second switch K2 to be turned on when the detection current value represented by the current detection signal is less than or equal to the first threshold value; the control unit 11 controls the first switch K1 to be turned on and the second switch K2 to be disconnected when the detection current value represented by the current detection signal is greater than the first threshold value and less than or equal to the second threshold value. In some embodiments, the first threshold value can be set to zero or a value close to zero. For example, the first threshold value can be set to 0 or 0.01A. When the current value represented by the current detection signal is equal to zero, the first switch K1 is controlled to be disconnected and the second switch K2 is controlled to be turned on. If the current value represented by the current detection signal is equal to zero, it means that the circuit where the current detection unit 12 is located is broken, indicating that the photovoltaic string is broken. If possible, the third switch K3 is disconnected or a circuit is broken. In both cases, the output of the photovoltaic module 30 needs to be turned off to prevent the risk of leakage. Therefore, the control unit 11 disconnects the first switch K1 and turns on the second switch K2.

[0050] Specifically, the power supply unit 21 is set as a constant current source, and the second threshold value is set based on the current output by the power supply unit 21 to the current detection unit 12 when the power supply unit 21, the current detection unit 12 and the second switch K2 form a loop and the third switch K3 is turned on. After the first switch K1 and the third switch K3 are both disconnected and the second switch K2 is turned on, the constant current source and several second switches K2 in the photovoltaic string and several current detection units 12 form a loop. At this time, the detection current value of the current detection unit 12 is equal to the output current value of the constant current source. For example, if the output current of the constant current source is I1, then the detection current value of the current detection unit 12 at this time is also I1. If the third switch K3 is turned on at this time, the constant current source, the third switch K3 and the primary side of the inverter 40 form a second loop. When the output current of the constant current source remains unchanged, the current flowing through the current detection unit 12 is equal to the output current value of the constant current source. The current of the current detection unit 12 is shunted due to the conduction of the third switch K3. At this time, the detection current value of the current detection unit 12 will be less than I1. In an exemplary embodiment, when there is no other fault in the circuit, the detection current value of the current detection unit 12 is I2, and the second threshold is set to a value greater than I2 and less than I1, for example, set to 1.1 times I2. When the control unit 11 receives a current detection signal indicating that the current value is greater than 0 and less than 1.1·I2, the first switch K1 is controlled to be turned on and the second switch K2 is turned off.

[0051] In some embodiments, the control unit 11 controls the first switch K1 to be disconnected and the second switch K2 to be turned on when the detection current value represented by the current detection signal is equal to 0; the control unit 11 controls the first switch K1 to be turned on and the second switch K2 to be turned off when the detection current value represented by the current detection signal is within a preset current threshold range. The preset current threshold range is set based on the second threshold value based on the current I2 output by the power supply unit 21 to the current detection unit 12 when the power supply unit 21, the current detection unit 12 and the second switch K2 form a loop and the third switch K3 is turned on. For example, the preset current threshold range is set to [0.9·I2, 1.1·I2].

[0052] In this embodiment, if Figure 2 As shown, the string shutdown module 20 also includes a trigger 22, the trigger 22 includes a signal input terminal and a signal output terminal, the power supply unit 21 includes an enable signal input terminal, the signal output terminal of the trigger 22 is electrically connected to the enable signal input terminal of the power supply unit 21 and is used to output an enable signal to the power supply unit 21; the trigger 22 is used to output enable signals of different level states at the signal output terminal of the trigger 22 when the third switch K3 operates in different on-off states; the power supply unit 21 outputs two electrical signals of different voltages according to the level state of the enable signal. The trigger 22 is set as a monostable trigger 22, for example, a monostable trigger 22 composed of a 555 timer, which outputs an enable signal of a high level or a level signal according to the on-off state of the third switch K3. In this embodiment, the power supply unit 21 is set as a bootstrap boost power supply, which can output a first voltage signal or a second voltage signal according to the level state of the enable signal. For example, when the enable signal is a low level signal, the power supply unit 21 outputs a fixed voltage of 12V DC, and when the enable signal is a high level signal, the power supply unit 21 outputs a fixed voltage of 24V DC. When the power supply unit 21 and the current detection unit 12 form a loop, the current flowing through the power detection unit is different.

[0053] Specifically, Figure 2, the string shut-off module 20 further includes a step-down unit 23 and an energy storage battery unit 24, the input end of the step-down unit 23 is electrically connected to the bus input end of the photovoltaic string, the output end is electrically connected to the input end of the energy storage battery unit 24, and the output end of the energy storage battery unit 24 is electrically connected to the input end of the power supply unit 21; the step-down unit 23 is used to charge the energy storage battery unit 24 after stepping down the output voltage of the photovoltaic string; the energy storage battery unit 24 is used to supply power to the power supply unit 21. In some embodiments, the step-down unit 23 is set as a wide voltage step-down unit 23, which is used to convert the 8-1500V voltage input of the photovoltaic string into a fixed voltage and used to charge the energy storage battery unit 24, and the energy storage battery unit 24 is used to supply power to the power supply unit 21.

[0054] Specifically, Figure 2 As shown, the string shutoff module 20 also includes a fourth switch K4, the on-off state of the fourth switch K4 is synchronized with the on-off state of the third switch K3, one end of the fourth switch K4 is electrically connected to the reference ground, and the other end is electrically connected to the signal input end of the trigger 22; when the fourth switch K4 is disconnected, the signal output end of the trigger 22 outputs a first trigger signal, and the power supply unit 21 outputs a first voltage signal to the photovoltaic string circuit; when the fourth switch K4 is turned on, the signal output end of the trigger 22 outputs a second trigger signal, and the power supply unit 21 outputs a second voltage signal to the photovoltaic string circuit. When the power supply unit 21 outputs the first voltage signal to the photovoltaic string circuit, the detection current value represented by the current detection signal output by the current detection unit 12 is less than or equal to the first threshold; when the power supply unit 21 outputs the second voltage signal to the photovoltaic string circuit, the detection current value represented by the current detection signal output by the current detection unit 12 is greater than the first threshold and less than or equal to the second threshold. The on-off state of the third switch K3 is detected by the fourth switch K4 that acts synchronously with the third switch K3, and the trigger 22 is made to output the first trigger signal or the second trigger signal of different level states according to the on-off state of the fourth switch K4, so as to control the power supply unit 21 to output the first voltage signal or the second voltage signal, thereby generating currents of different amplitudes in the loop formed by the power supply unit 21 and the current detection unit 12, so that the control unit 11 can judge the on-off state of the third switch K3 through the current detection signal output by the current detection unit 12. It should be noted that the present embodiment does not specifically limit the corresponding relationship between the output level signal and the output voltage signal of the trigger 22 and the power supply unit 21, and only needs to differentiate the output level state of the trigger 22 and the output voltage value of the power supply unit 21 to ensure that the control unit 11 can detect the on-off state of the third switch K3.

[0055] Specifically, Figure 2As shown, a withstand voltage diode D3 is also connected in series to the positive electrode of the output end of the power supply unit 21. Since the power supply unit 21 is always in the output state, the withstand voltage diode connected in series to the output end of the power supply 21 can prevent the high voltage output of the photovoltaic string from acting on the power supply unit 21 and causing damage to the power supply unit 21.

[0056] As an implementation, the current detection unit 12 includes a measuring resistor and an amplifier circuit whose input end is electrically connected to both ends of the measuring resistor, and the output end of the amplifier circuit is used to output the current detection signal.

[0057] As another implementation, the current detection unit 12 includes a Hall current sensor.

[0058] like Figure 3 As shown, a discharge unit 13 is electrically connected between the output ends of the component shutdown module 10. The discharge unit 13 is used to quickly release the residual charge in the circuit after the first switch K1 and the second switch K2 are disconnected. The discharge unit 13 includes a fifth switch K5 and a discharge resistor R1.

[0059] As an implementation, the first switch K1, the second switch K2 and the fifth switch K5 are set to be one of a MOS tube, an IGBT or a relay switch, the control electrode of the fifth switch K5 is electrically connected to the control unit 11, and the control unit 11 controls the fifth switch K5 to be turned on and then turned off within a preset time while the first switch K1 is turned off, and when the fifth switch K5 is turned on, the second switch K2 is not turned on. The discharge circuit only needs to be turned on briefly to release the residual charge in the circuit. After the fourth switch of the discharge circuit is turned off, the control unit 11 controls the second switch K2 to be turned on, so that the control unit 11 can determine the on-off state of the third switch K3.

[0060] Specifically, Figure 1 As shown, a freewheeling diode D1 is electrically connected between the output ends of the component shutdown module 10. The freewheeling diode D1 is used to enable the photovoltaic string to work normally when any photovoltaic module 30 or the component shutdown module 10 of the photovoltaic string is disconnected.

[0061] Specifically, Figure 1 As shown, the component shutdown module 10 further includes a power supply unit 14, which takes power from the photovoltaic module 30 and is used to power the control unit 11, and the input end of the power supply unit 14 is electrically connected to the output end of the photovoltaic module 30. Specifically, the power supply unit 14 is configured as a DC-DC voltage converter.

[0062] like Figure 4As shown, this embodiment also provides a photovoltaic system, including a plurality of photovoltaic strings and an inverter 40, wherein the plurality of photovoltaic strings are connected in parallel to the input end of the inverter 40, and the output end of the inverter 40 is connected to the power grid, and the photovoltaic string includes a plurality of photovoltaic modules 30 and a circuit breaker, wherein the circuit breaker is configured as a circuit breaker as described in any of the above technical solutions, and the output ends of the plurality of photovoltaic modules 30 are electrically connected to the input ends of the plurality of component shutdown modules 10 in a one-to-one correspondence, and the photovoltaic module 30 includes at least one photovoltaic component. The beneficial effects of the photovoltaic system described in this embodiment are similar to the reasoning process of the beneficial effects of the circuit breaker described in the above embodiment, and will not be repeated here.

[0063] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes but is not limited to the contents described in the drawings and the above specific embodiments. Any modification that does not deviate from the functional and structural principles of the present invention will be included in the scope of the claims.

Claims

1. A circuit breaker for controlling the shutdown of a photovoltaic string, the circuit breaker comprising a plurality of component shutdown modules (10) and a group of string shutdown modules (20), the input end of the component shutdown module (10) being electrically connected to the output end of a photovoltaic module (30), the photovoltaic module (30) comprising at least one photovoltaic component, the output ends of the plurality of component shutdown modules (10) being connected in series and then electrically connected to the input end of a busbar of the photovoltaic string, characterized in that: The component shut-down module (10) comprises: A first switch (K1), the input end of the first switch (K1) being electrically connected to the first output end of the photovoltaic module (30), and being used to control the on / off state between the photovoltaic module (30) and the busbar of the photovoltaic string; a current detection unit (12), one end of the current detection unit (12) being electrically connected to the output end of the first switch (K1), and the other end of the current detection unit (12) being set as the output end of the component shutdown module (10), and being used for detecting the current value flowing on the line and generating a current detection signal representing the detected current value; a second switch (K2), one end of the second switch (K2) being electrically connected between the output end of the first switch (K1) and the input end of the current detection unit (12), and the other end of the second switch (K2) being electrically connected to the second output end of the photovoltaic module (30); A control unit (11), electrically connected to control ends of the first switch (K1) and the second switch (K2) and a current detection signal output end of the current detection unit (12), and used for controlling the on / off state of the first switch (K1) and the second switch (K2) according to a numerical range of a detection current value represented by the current detection signal; The string shutoff module (20) comprises a power supply unit (21) and a third switch (K3); the output end of the power supply unit (21) is electrically connected to the bus input end of the photovoltaic string, and is used to output two electrical signals of different voltages to the photovoltaic string according to the on-off state of the third switch (K3); the third switch (K3) is electrically connected between the input end and the output end of the bus, and is used to control the on-off state between the photovoltaic string and an external circuit.

2. The circuit breaker according to claim 1, characterized in that: The string shutoff module (20) further comprises a trigger (22), the trigger (22) comprising a signal input end and a signal output end, the power supply unit (21) comprising an enable signal input end, the signal output end of the trigger (22) being electrically connected to the enable signal input end of the power supply unit (21) and being used to output an enable signal to the power supply unit (21); The trigger (22) is used for outputting enable signals of different level states at a signal output end of the trigger (22) when the third switch (K3) operates in different on-off states; The power supply unit (21) outputs two electrical signals with different voltages according to the level state of the enable signal.

3. The circuit breaker according to claim 2, characterized in that: The string shutoff module (20) further comprises a voltage reduction unit (23) and an energy storage battery unit (24); the voltage reduction unit (23) has an input end electrically connected to the busbar input end of the photovoltaic string, an output end electrically connected to the input end of the energy storage battery unit (24), and the output end of the energy storage battery unit (24) is electrically connected to the input end of the power supply unit (21); The voltage reduction unit (23) is used to reduce the output voltage of the photovoltaic string and then charge the energy storage battery unit (24); The energy storage battery unit (24) is used to supply power to the power supply unit (21).

4. The circuit breaker according to claim 2, characterized in that: The string shutoff module (20) further comprises a fourth switch (K4), the on-off state of the fourth switch (K4) being synchronized with the on-off state of the third switch (K3), one end of the fourth switch (K4) being electrically connected to a reference ground, and the other end of the fourth switch (K4) being electrically connected to a signal input end of a trigger (22); When the fourth switch (K4) is disconnected, the signal output end of the trigger (22) outputs a first trigger signal, and the power supply unit (21) outputs a first voltage signal to the photovoltaic string circuit; When the fourth switch (K4) is turned on, the signal output end of the trigger (22) outputs a second trigger signal, and the power supply unit (21) outputs a second voltage signal to the photovoltaic string circuit.

5. The circuit breaker according to claim 4, characterized in that: When the power supply unit (21) outputs a first voltage signal to the photovoltaic string circuit, a detection current value represented by a current detection signal output by the current detection unit (12) is less than or equal to a first threshold value; When the power supply unit (21) outputs a second voltage signal to the photovoltaic string circuit, the detection current value represented by the current detection signal output by the current detection unit (12) is greater than a first threshold value and less than or equal to a second threshold value.

6. The circuit breaker according to any one of claims 1 to 5, characterized in that: The control unit (11) controls the first switch (K1) to be disconnected and controls the second switch (K2) to be turned on when the detection current value represented by the current detection signal is less than or equal to a first threshold value; The control unit (11) controls the first switch (K1) to be turned on and controls the second switch (K2) to be turned off when the detection current value represented by the current detection signal is greater than a first threshold value and less than or equal to a second threshold value.

7. The circuit breaker according to any one of claims 2 to 5, characterized in that: The power supply unit (21) is configured as a bootstrap boost power supply, and the trigger (22) is configured as a monostable trigger (22).

8. The circuit breaker according to any one of claims 1 to 5, characterized in that: The current detection unit (12) comprises a measuring resistor and an amplifier circuit whose input end is electrically connected to both ends of the measuring resistor, and whose output end is used to output the current detection signal.

9. The circuit breaker according to any one of claims 1 to 5, characterized in that: The current detection unit (12) includes a Hall current sensor.

10. The circuit breaker according to any one of claims 1 to 5, characterized in that: A discharge unit (13) is also electrically connected between the output ends of the component shutdown module (10), and the discharge unit (13) is used to quickly release the residual charge in the circuit after the first switch (K1) and the second switch (K2) are disconnected, and the discharge unit (13) comprises a fifth switch (K5) and a discharge resistor.

11. The circuit breaker according to claim 10, characterized in that: The first switch (K1), the second switch (K2) and the fifth switch (K5) are configured as one of a MOS tube, an IGBT or a relay switch; the control electrode of the fifth switch (K5) is electrically connected to the control unit (11); the control unit (11) controls the fifth switch (K5) to be turned on within a preset time and then turned off when the first switch (K1) is turned off; and when the fifth switch (K5) is turned on, the second switch (K2) is not turned on.

12. The circuit breaker according to any one of claims 1 to 5, characterized in that: A freewheeling diode (D1) is also electrically connected between the output ends of the component shutdown module (10).

13. The circuit breaker according to any one of claims 1 to 5, characterized in that: The component shutdown module (10) further comprises a power supply unit (14), the power supply unit (14) taking power from the photovoltaic module (30) and used to supply power to the control unit (11), the input end of the power supply unit (14) being electrically connected to the output end of the photovoltaic module (30).

14. A photovoltaic system, comprising a plurality of photovoltaic strings and an inverter (40), wherein the plurality of photovoltaic strings are connected in parallel to the input end of the inverter (40), and the output end of the inverter (40) is connected to a power grid, characterized in that: The photovoltaic string comprises a plurality of photovoltaic modules (30) and a circuit breaker, wherein the circuit breaker is configured as a circuit breaker as described in any one of claims 1 to 13, wherein the output ends of the plurality of photovoltaic modules (30) are electrically connected to the input ends of the plurality of component shutdown modules (10) in a one-to-one correspondence, and the photovoltaic module (30) comprises at least one photovoltaic component.

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