Photovoltaic group string turn-off device and photovoltaic system

Abstract

The invention discloses a photovoltaic string turn-off device and a photovoltaic system, the photovoltaic string 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 input end of each string turn-off module is electrically connected with the output end of the photovoltaic module. The output ends of the plurality of assembly turn-off modules are connected in series and then are electrically connected with the input end of a bus of a photovoltaic group string. Each group string turn-off module comprises a first switch, a first signal unit and a control unit. The component turn-off module comprises a third switch, a current detection unit, a second signal unit and a second control unit, and when one of the first signal unit and the second signal unit works in a sending state, the other one works in a receiving state. 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 third switch to be synchronously turned on and turned off along with the first switch.

Description

Technical Field

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

[0002] The photovoltaic system of the prior art can usually only realize group string level shutdown, and there is still DC high voltage in the circuit from the photovoltaic module to the inverter or controller, which is a huge hidden danger to personal safety.

[0003] In order to eliminate the high voltage in the circuit from the photovoltaic module to the inverter, the prior art sets a shutoff device on the output end of the photovoltaic module, and controls the operation of the shutoff device by sending a heartbeat packet to the shutoff device through an external controller, that is, the external controller continuously sends a heartbeat packet to the shutoff device, and the shutoff device 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 disadvantage is that it is necessary to ensure stable and reliable communication between the shutoff device and the external controller, otherwise it will affect the normal operation of the photovoltaic system and reduce the stability of the system. In addition, the setting distance between the shutoff device and the controller is limited by their 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 photovoltaic string shut-off device and a photovoltaic system, which can accurately and quickly control the connection status of photovoltaic strings and photovoltaic modules, has good safety and low cost.

[0005] In a first aspect, to achieve the above-mentioned purpose, the present invention proposes a photovoltaic string shut-off device for shutting down photovoltaic strings, the shut-off device comprising a plurality of component shut-off modules and a group of string shut-off modules, the input end of the component shut-off 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 shut-off modules being connected in series and then electrically connected to the input end of the busbar of the photovoltaic string,

[0006] The string shut-off module comprises:

[0007] A first switch, the first switch is electrically connected between the input end and the output end of the busbar, and is used to control the on / off state between the photovoltaic string and the external circuit;

[0008] A first signal unit, electrically connected between the bus input terminals, includes a sending state of sending an electrical signal to the component shutdown module or a receiving state of receiving an electrical signal from the component shutdown module;

[0009] a first control unit, electrically connected to the first switch control terminal and the first signal unit, and configured to control a switch state of the first switch and a transceiver state of the first signal unit;

[0010] The component shutdown module comprises:

[0011] A third switch, wherein an input end of the third 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;

[0012] a current detection unit, one end of which is electrically connected to the output end of the third 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;

[0013] A second signal unit, the second signal unit is electrically connected between the output end of the first switch and the input end of the current detection unit, and includes a sending state of sending an electrical signal to the string shutoff module and a receiving state of receiving an electrical signal from the string shutoff module;

[0014] A second control unit is electrically connected to the control end of the third switch, the current detection signal output end of the current detection unit, and the second signal unit, and is used to control the on-off state of the third switch and the transceiver state of the second signal unit according to the numerical range of the detection current value represented by the current detection signal;

[0015] When one of the first signal unit and the second signal unit operates in a sending state, the other operates in a receiving state.

[0016] In the present technical solution, the first signal unit and the second signal unit respectively work in a signal receiving state and a signal sending state, and transmit electrical signals through the internal circuit of the photovoltaic string, thereby realizing information interaction between the first signal unit and the second signal unit, so that the first control unit and the second control unit can detect each other's working state and the connection state of the photovoltaic string circuit, thereby realizing on-off control of the photovoltaic string and the photovoltaic module.

[0017] Preferably, when the first signal unit works in a receiving state, the second signal unit works in a sending state, the first signal unit receives the electrical signal sent by the second signal unit and generates a first detection signal, and the first signal unit sends the first detection signal to the first control unit.

[0018] Preferably, when the second signal unit operates in a receiving state, the first signal unit operates in a sending state, the second signal unit receives the electrical signal sent by the first signal unit and generates a second detection signal, and the second signal unit sends the second detection signal to the second control unit.

[0019] Preferably, a second switch is further connected in series between the busbar input ends of the photovoltaic component, the first signal unit is electrically connected to the source electrode of the second switch, the first control unit is electrically connected to the control electrode of the second switch, and the first control unit controls the second switch to be turned on when controlling the first switch to be turned off, and the first signal unit works in a sending state or a receiving state;

[0020] The component shutdown module also includes a fourth switch, a drain of the fourth switch electrically connected to the second output end of the photovoltaic module, a source electrically connected to the second signal unit and electrically connected between the first switch and the current detection unit, and a control electrode electrically connected to the second control unit. When the detection current value represented by the current detection signal is less than the first current threshold, the second control unit controls the third switch to be disconnected and the fourth switch to be turned on, and the second signal unit operates in a receiving state or a sending state corresponding to the first signal unit.

[0021] Preferably, the first control unit controls the second switch to be turned off when controlling the first switch to be turned on;

[0022] The second control unit controls the third switch to be turned on and the fourth switch to be turned off when the second detection signal indicates that the first signal unit has no signal output or receives a preset control signal.

[0023] 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.

[0024] Preferably, the current detection unit includes a Hall current sensor.

[0025] 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 third switch are disconnected. The discharge unit includes a fifth switch and a discharge resistor.

[0026] Preferably, a freewheeling diode is electrically connected between the output ends of the component shutdown module.

[0027] In the second aspect, in order to achieve the above invention purpose, the present application also proposes 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 string includes a plurality of photovoltaic modules and a shut-off device, the shut-off device is set as the shut-off device 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 shut-off modules in a one-to-one correspondence, and the photovoltaic module includes at least one photovoltaic component. The photovoltaic system provided by the present application is similar to the reasoning process of the beneficial effects of the aforementioned photovoltaic string shut-off device, which will not be repeated here.

[0028] 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

[0029] The present invention will be further described below in conjunction with the accompanying drawings:

[0030] Figure 1 is a circuit diagram of a shutdown device according to an embodiment of the present invention;

[0031] Figure 2 is a schematic diagram of a second signal unit circuit according to an embodiment of the present invention;

[0032] Figure 3 is a schematic diagram of a first signal unit circuit according to an embodiment of the present invention;

[0033] Figure 4 is a schematic diagram of a discharge unit circuit according to an embodiment of the present invention;

[0034] Figure 5 4 is a schematic diagram of a photovoltaic system circuit according to an embodiment of the present invention.

[0035] Description of reference numerals:

[0036] Among them, 10, component shutdown module; 11, first control unit; 12, first signal unit; 13, main control switch; 14, communication unit; 20, string shutdown module; 21, second control unit; 22, current detection unit; 23, second signal unit; 24, discharge unit; 25, power supply unit; 30, photovoltaic module; 40, inverter; K1, first switch; K2, second switch; K3, third switch; K4, fourth switch; K5, fifth switch; D1, freewheeling diode. DETAILED DESCRIPTION

[0037] 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.

[0038] 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.

[0039] like Figure 1 As shown, a photovoltaic string shut-off device is used for shut-off control of photovoltaic strings, the shut-off device includes a plurality of component shut-off modules 10 and a group of string shut-off modules 20, the component shut-off module 10 has an input end electrically connected to an output end of a photovoltaic module 30, the photovoltaic module 30 includes at least one photovoltaic component, and 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,

[0040] The string shut-off module 20 includes:

[0041] A first switch K1, the first switch K1 is electrically connected between the input end and the output end of the busbar, and is used to control the on-off state between the photovoltaic string and the external circuit;

[0042] The first signal unit 12 is electrically connected between the bus input terminals, and includes a sending state of sending an electrical signal to the component shutdown module 10 or a receiving state of receiving an electrical signal from the component shutdown module 10;

[0043] A first control unit 11, electrically connected to the control end of the first switch K1 and the first signal unit 12, and configured to control the switch state of the first switch K1 and the transceiver state of the first signal unit 12;

[0044] The component shutdown module 10 includes:

[0045] A third switch K3, the input end of the third switch K3 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;

[0046] A current detection unit 22, one end of which is electrically connected to the output end of the third switch K3, and the other end is set as the output end of the component shutdown module 10, which is used to detect the current value flowing through the line and generate a current detection signal representing the detected current value;

[0047] A second signal unit 23, the second signal unit 23 is electrically connected between the output end of the first switch K1 and the input end of the current detection unit 22, including a sending state of sending an electrical signal to the string shutoff module 20 and a receiving state of receiving an electrical signal from the string shutoff module 20;

[0048] A second control unit 21 is electrically connected to the control end of the third switch K3, the current detection signal output end of the current detection unit 22, and the second signal unit 23, and is used to control the on-off state of the third switch K3 and the transceiver state of the second signal unit 23 according to the numerical range of the detection current value represented by the current detection signal;

[0049] When one of the first signal unit 12 and the second signal unit 23 operates in a sending state, the other operates in a receiving state.

[0050] In this embodiment, the photovoltaic module 30 is set as a photovoltaic assembly or a string of two or more photovoltaic assemblies connected in series. After the first control unit 11 controls the first switch K1 to be turned off, the busbar of the photovoltaic string is disconnected. The line between the photovoltaic module 30 and the busbar input end of the photovoltaic string still has high voltage, which is easy to cause electric shock or line failure. The current detection unit 22 detects the current in the internal line of the photovoltaic string to determine whether the first switch K1 is disconnected. When the first switch K1 is disconnected, the detection current value represented by the current detection signal of the current detection unit 22 is zero. When the second control unit 21 receives the detection current value represented by the current detection signal sent by the signal detection unit 22 and the detection current value is zero, the second control unit 21 controls the third switch K3 to be disconnected. In order for the second control unit 21 to control the third switch K3 to be turned on accordingly after the first switch K1 is turned on again, the first signal unit 12 and the second signal unit 23 are respectively set in the circuit to work in the electrical signal receiving state and the sending state, and the first signal unit 12 and the second signal unit 23 can switch the sending and receiving states. When one of them works in the electrical signal sending state, the other works in the receiving state. When the first signal unit 12 works in the state of sending electric signals and the second signal unit 23 works in the state of receiving signals, the second control unit 21 can detect the conduction action of the first switch K1 through the electrical parameters of the electrical signals sent by the first signal unit 12. When the second signal unit 23 works in the state of sending electric signals and the first signal unit 12 works in the state of receiving signals, the first control unit 11 can judge whether the internal circuit of the photovoltaic string is correctly connected through the electrical parameters of the electrical signals received by the first signal unit 12. That is, the working state perception between the component shutdown module and the string shutdown module is realized through the transmission of electrical signals between the first signal unit 12 and the second signal unit 23, so that the connection state of the photovoltaic string and the photovoltaic module can be accurately and quickly controlled.

[0051] Specifically, when the first signal unit 12 works in a receiving state, the second signal unit 23 works in a sending state, the first signal unit 12 receives the electrical signal sent by the second signal unit 23 and generates a first detection signal, and the first signal unit 12 sends the first detection signal to the first control unit 11.

[0052] Specifically, when the second signal unit 23 works in a receiving state, the first signal unit 12 works in a sending state, the second signal unit 23 receives the electrical signal sent by the first signal unit 12 and generates a second detection signal, and the second signal unit sends the second detection signal to the second control unit 21.

[0053] Specifically, a second switch K2 is further connected in series between the busbar input ends of the photovoltaic component. In this embodiment, the second switch K2 is set to an NMOS tube, the first signal unit 12 is electrically connected to the source of the second switch K2, and the first control unit 11 is electrically connected to the control electrode of the second switch K2. When the first control unit 11 controls the first switch K1 to be disconnected, the second switch K2 is controlled to be turned on, and the first signal unit 12 works in a sending state or a receiving state;

[0054] The component shutdown module 10 also includes a fourth switch K4, which is set to an NMOS tube. The drain of the fourth switch K4 is electrically connected to the second output end of the photovoltaic module, the source is electrically connected to the second signal unit 23 and is electrically connected between the first switch 23 and the current detection unit 22, and the control electrode is electrically connected to the second control unit 21. When the detection current value represented by the current detection signal is less than the first current threshold, the second control unit 21 controls the third switch K3 to be disconnected and the fourth switch K4 to be turned on, and the second signal unit 23 operates in a receiving state or a sending state corresponding to the first signal unit 12.

[0055] like Figure 2As shown, the second signal unit 23 includes a photocoupler Q1 and a transistor Q2, MCU2_TXD is electrically connected to the signal output end of the second control unit 21 and is used to receive the control signal sent by the second control unit 21, MCU2_RXD is electrically connected to the signal receiving end of the second control unit 21 and is used to send a first detection signal to the second control unit 21, and 2_PWR_LINE is used to output an electrical signal to the string shutdown module 20. In the present embodiment, the transistor Q2 is set as a PNP transistor. When the signal output end of the second control unit 21 outputs a square wave signal, the second signal unit 23 works in the sending state. The transistor Q2 works alternately between the on and off states under the control of the square wave signal, and 2_PWR_LINE outputs a square wave signal. The light-emitting diode on the primary side of the photocoupler Q1 flashes due to the alternating operation between the on and off states, and the photosensitive diode on its secondary side also works alternately between the on and off states. When the photosensitive diode is turned on, MCU2_RXD outputs a high-level signal. When the photosensitive diode is turned off, MCU2_RXD outputs a low-level signal. When the photosensitive diode works alternately between the on and off states, MCU2_RXD outputs a square wave signal to the second control unit. Therefore, in the present embodiment, when the second signal unit 23 works in the sending state, MCU2_RXD can receive the square wave signal output by its 2_PWR_LINE and monitor whether the output signal is normal; the signal output end of the second control unit 21 outputs a low-level signal Under the condition that the second signal unit 23 works in the receiving state, the transistor Q2 is continuously turned on under the control of the low-level signal output by MCU2_TXD. If a high-level signal is input to 2_PWR_LINE, both ends of the light-emitting diode of the photoelectric coupler Q1 are high-level signals, the light-emitting diode does not work, and the photosensitive diode is cut off. If a low-level signal is input to 2_PWR_LINE, the light-emitting diode of the photoelectric coupler Q1 is turned on and works, and the photosensitive diode is also turned on at the same time. Therefore, when the second signal unit 23 works in the receiving state and there is a square wave signal input on 2_PWR_LINE, MCU2_RXD can output a square wave signal opposite to the level state of the square wave signal input by 2_PWR_LINE to the second control unit 21, that is, when the second control unit 21 controls the second signal unit 23 to work in the receiving state, the second signal unit 23 receives the external input square wave signal through 2_PWR_LINE to generate a second detection signal and sends it to the second control unit 21 through MCU2_RXD.

[0056] like Figure 3As shown, the first signal unit 12 includes a transistor Q3 and a photocoupler Q4, MCU1_TXD is electrically connected to the signal output end of the first control unit 11 and is used to receive the control signal sent by the first control unit 11, MCU1_RXD is electrically connected to the signal receiving end of the first control unit 12 and is used to send a first detection signal to the first control unit 12, and 1_PWR_LINE is used to output an electrical signal to the component shutdown module 10. Its specific working process and working principle are similar to Figure 2 The second signal unit 23 is the same as shown in FIG. Figure 1 In the shutdown device circuit shown, when the first switch K1 and the third switch K3 are disconnected and the second switch K2 and the fourth switch K4 are turned on, 1_PWR_LINE of the first signal unit 12 and 2_PWR_LINE of the second signal unit 23 are electrically connected, one of the first signal unit 12 and the second signal unit 23 works in the sending state, and the other works in the conducting state, and the two transmit signals in the circuit of the photovoltaic string and judge each other's working state and connection state according to the waveform of the signal.

[0057] In some embodiments, the shutdown device includes several component shutdown modules 10, that is, it includes several second signal units 23. The component shutdown module 10 is set as a slave, the string shutdown module 20 is set as a master, the second signal units 23 are all set to the receiving state at the initial time, the first signal unit 12 is set to the sending state at the initial time, and address codes are set for several second signal units 23. The first signal unit 12 sends (sends at intervals, waiting for response) the address code of each slave one by one through a waveform signal, and the slave that receives its set address code sends a response signal to the master. After the master and slave complete the information exchange in turn and confirm that the status is correct, all the slaves are in the receiving state again. When the first control unit 11 receives the start signal of the main switch 13, it uses a broadcast method to send a preset control signal to notify all slaves to turn on the second switch K3 and turn off the fourth switch K4 (delayed after receiving the confirmation feedback information from all slaves). Specifically, the branch where the first signal unit 12 is located is connected in series with a second switch K2. When the first control unit controls the first switch K1 to be disconnected, the second switch K2 is controlled to be turned on, and the first signal unit 12 works in a sending state or a receiving state. A fourth switch K4 is connected in series with the branch where the second signal unit 23 is located. When the detection current value represented by the current detection signal is less than the first current threshold, the second control unit 21 controls the third switch K3 to be turned off and the fourth switch K4 to be turned on, and the second signal unit 23 works in a receiving state or a sending state corresponding to the first signal unit 12. When the first control unit 11 controls the first switch K1 to be turned on, the second switch K2 is controlled to be turned off. When the second detection signal represents that the first signal unit 12 has no output or receives a preset control signal, the second control unit 21 controls the third switch K3 to be turned on and the fourth switch K4 to be turned off. That is, the conduction state of the third switch K3 follows the conduction state of the first switch K1.

[0058] Specifically, the first control unit 21 is also electrically connected to a main control switch 13, and the main control switch 13 is used to generate a start signal and a shutdown signal for controlling the first switch K1 to be turned on and off. When the first control unit 21 receives the start signal, it controls the first switch K1 to be turned on. When the first switch unit 21 receives the shutdown signal, it controls the first switch K1 to be turned off.

[0059] In some embodiments, the current detection unit 22 includes a measuring resistor and an amplifier circuit whose input terminal is electrically connected to both ends of the measuring resistor, and the output terminal of the amplifier circuit is used to output the current detection signal. In addition, in other embodiments, the current detection unit 22 includes a Hall current sensor.

[0060] Specifically, Figure 2As shown, a discharge unit 24 is also electrically connected between the output ends of the component shutdown module 20, and the discharge unit 24 is used to quickly release the residual charge in the circuit after the first switch K1 and the third switch K3 are disconnected, and the discharge unit 24 includes a fifth switch K5 and a discharge resistor. The discharge unit only needs to be turned on briefly to release the residual charge in the circuit, and the second control unit 21 briefly turns on the fifth switch K5 after the third switch K3 is turned off to release the charge in the circuit. After the fifth switch K5 is turned off, the second control unit 21 controls the fourth switch K4 to turn on, so that the second signal unit 23 can receive the electrical signal sent by the first signal unit 12 or the second signal unit 23 can send an electrical signal to the first signal unit 12.

[0061] As an implementation method, the first switch K1, the second switch K2, the third switch K3, the fourth switch K4 and the fifth switch K5 are set to be one of a MOS tube, an IGBT or a relay switch, and the control electrodes of the first switch K1 and the second switch K2 are electrically connected to the first control unit 11, and the control electrodes of the third switch K3, the fourth switch K4 and the fifth switch K5 are electrically connected to the second control unit 21.

[0062] Specifically, Figure 1 As shown, a freewheeling diode D1 is electrically connected between the output ends of the component shutdown module 20. The freewheeling diode D1 is used to enable the photovoltaic string to work normally when any photovoltaic module 30 or the component shutdown module 20 of the photovoltaic string is disconnected.

[0063] Specifically, Figure 1 As shown, the component shutdown module 20 further includes a power supply unit 14, which takes power from the photovoltaic module 30 and is used to power the second control unit 21, 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.

[0064] like Figure 3 As 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 strings include a plurality of photovoltaic modules 30 and a shutoff device, wherein the shutoff device is configured as a shutoff device 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 shutoff modules 20 in a one-to-one correspondence, and the photovoltaic modules 30 include 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 shutoff device described in the above embodiment, and will not be repeated here.

[0065] 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 photovoltaic string shutoff device, used for shutoff control of a photovoltaic string, the shutoff device comprising a plurality of component shutoff modules (20) and a group of string shutoff modules (10), the input end of the component shutoff module (20) 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 shutoff modules (20) being connected in series and then electrically connected to the input end of a busbar of the photovoltaic string, characterized in that: The string shutoff module (10) comprises: A first switch (K1), the first switch (K1) is electrically connected between the input end and the output end of the busbar, and is used to control the on / off state between the photovoltaic string and the external circuit; A first signal unit (12) is electrically connected between the positive and negative input terminals of the busbar, and includes a sending state of sending an electrical signal to the component shutdown module (20) or a receiving state of receiving an electrical signal from the component shutdown module (20); A first control unit (11), electrically connected to a control end of the first switch (K1) and a first signal unit (12), and used for controlling a switch state of the first switch (K1) and a transceiver state of the first signal unit (12); The component shut-off module (20) comprises: a third switch (K3), the input end of the third switch (K3) 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 (22), one end of the current detection unit (22) being electrically connected to the output end of the third switch (K3), and the other end of the current detection unit (22) being set as the output end of the component shutdown module (20), 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 signal unit (23), the second signal unit (23) being electrically connected between the output end of the first switch (K1) and the input end of the current detection unit (22), and comprising a sending state of sending an electrical signal to the string shutoff module (10) and a receiving state of receiving an electrical signal from the string shutoff module (10); A second control unit (21) is electrically connected to a control end of the third switch (K3), a current detection signal output end of the current detection unit (22), and a second signal unit (23), and is used to control an on / off state of the third switch (K3) and a transceiver state of the second signal unit (23) according to a numerical range of a detection current value represented by the current detection signal; When one of the first signal unit (12) and the second signal unit (23) operates in a sending state, the other operates in a receiving state.

2. The shutoff device according to claim 1, characterized in that: When the first signal unit (12) works in a receiving state, the second signal unit (23) works in a sending state, the first signal unit (12) receives the electrical signal sent by the second signal unit (23) and generates a first detection signal, and the first signal unit (12) sends the first detection signal to the first control unit (11).

3. The shutoff device according to claim 2, characterized in that: When the second signal unit (23) works in a receiving state, the first signal unit (12) works in a sending state, the second signal unit (23) receives the electrical signal sent by the first signal unit (12) and generates a second detection signal, and the second signal unit (23) sends the second detection signal to the second control unit (21).

4. The shutoff device according to claim 3, characterized in that: A second switch (K2) is also connected in series between the busbar input ends of the photovoltaic component, the first signal unit (12) is electrically connected to the source electrode of the second switch (K2), the first control unit (11) is electrically connected to the control electrode of the second switch (K2), and the first control unit (11) controls the second switch (K2) to be turned on when the first switch (K1) is controlled to be turned off, and the first signal unit (12) operates in a sending state or a receiving state; The component shutdown module (10) further comprises a fourth switch (K4), a drain of the fourth switch (K4) being electrically connected to the second output terminal of the photovoltaic module, a source of the fourth switch (K4) being electrically connected to the second signal unit (23) and being electrically connected between the first switch (23) and the current detection unit (22), and a control of the fourth switch (K4) being electrically connected to the second control unit (21), and the second control unit (21) controlling the third switch (K3) to be disconnected and the fourth switch (K4) to be turned on when the detection current value represented by the current detection signal is less than a first current threshold, and the second signal unit (23) to operate in a receiving state or a sending state corresponding to the first signal unit (12).

5. The shutoff device according to claim 4, characterized in that: The first control unit (11) controls the second switch (K2) to be turned off when controlling the first switch (K1) to be turned on; The second control unit (21) controls the third switch (K3) to be turned on and the fourth switch (K4) to be turned off when the second detection signal indicates that the first signal unit (12) has no signal output or receives a preset control signal.

6. The shutoff device according to any one of claims 1 to 5, characterized in that: The current detection unit (22) 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.

7. The shutoff device according to any one of claims 1 to 5, characterized in that: The current detection unit (22) includes a Hall current sensor.

8. The shutoff device according to any one of claims 1 to 5, characterized in that: A discharge unit (24) is also electrically connected between the output ends of the component shutdown module (20), and the discharge unit (24) is used to quickly release the residual charge in the circuit after the first switch (K1) and the third switch (K3) are disconnected, and the discharge unit (24) comprises a fifth switch (K5) and a discharge resistor (R1).

9. The shutoff device 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 shutoff module (20).

10. A photovoltaic system, comprising a plurality of photovoltaic strings and an inverter (40), wherein the plurality of photovoltaic strings are connected in parallel to an input end of the inverter (40), and an 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 shut-off device, wherein the shut-off device is configured as a shut-off device as described in any one of claims 1 to 9, wherein the output ends of the plurality of photovoltaic modules (30) are electrically connected to the input ends of the plurality of component shut-off modules (20) in a one-to-one correspondence, and the photovoltaic module (30) comprises at least one photovoltaic component.

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