Grid-connected relay self-checking device

Abstract

The utility model discloses a self-checking device for a grid-connected relay, and relates to the field of power equipment detection. The device comprises a to-be-tested circuit which comprises a first relay, a third relay and a fifth relay which are sequentially connected in series on a grid-connected live wire between an inverter and a power grid side, and a second relay, a sixth relay and a fourth relay which are sequentially connected in series on a grid-connected zero wire between the inverter and the power grid side; the driving module is connected with the circuit to be tested and comprises four driving units; and a signal acquisition module connected with the circuit to be tested, wherein the signal acquisition module comprises four acquisition units. According to the device, the six relays are driven through the four driving units, and signals after the relays act are acquired through the four acquisition units, so that self-inspection of three groups of grid-connected relays is realized, and the self-inspection efficiency of the grid-connected relays can be improved.

Description

Technical Field

[0001] The utility model relates to the technical field of power equipment detection, in particular to a grid-connected relay self-detection device. Background Art

[0002] The grid-connected and off-grid inverter is used to convert the direct current generated by renewable energy power generation equipment into alternating current and connect it to the grid to achieve power supply and grid-connected operation. Relays are usually used as switching elements between the inverter and the grid. When connected to the grid, the grid-connected relay is closed, and the inverter injects renewable energy into the grid. When off-grid or a fault occurs, the grid-connected relay is disconnected. Relays can ensure the safe operation of grid-connected and off-grid systems and the reliability of power supply. As an important safety device, the reliability of the relay itself is crucial. Since the relay itself does not have a fault feedback contact, in actual applications, fault detection of the relay is required to reduce the occurrence of accidents.

[0003] Usually, the safety distance between the grid-connected and the inverter and the safety distance between the grid-connected and the off-grid require that the relays be used in series at least two stages to reduce the probability of accidents during system operation. Compared with the grid-connected system, an additional set of relays is usually added in the grid-connected and off-grid system, such as Figure 1 As shown, an off-grid interface is set after the first set of relays on the inverter side. Therefore, at least three sets of relays are usually set between the inverter and the grid in the on-grid and off-grid system. In the related art, usually only the grid-connected system using two sets of relays is self-checked, or a method of setting a separate drive signal for each relay is used for self-checking. There is a lack of efficient self-checking solutions for three sets of grid-connected relays connected in series. Utility Model Content

[0004] In view of this, the present application provides a grid-connected relay self-test device, the main purpose of which is to solve the technical problem of low self-test efficiency of three groups of series-connected grid-connected relays.

[0005] The utility model provides a grid-connected relay self-test device, which comprises:

[0006] The circuit to be tested includes a first relay, a third relay and a fifth relay connected in series in sequence on a grid-connected live line between an inverter and a grid side, and a second relay, a sixth relay and a fourth relay connected in series in sequence on a grid-connected neutral line between the inverter and the grid side, wherein the first relay and the second relay are arranged on the inverter side, and the fifth relay and the fourth relay are arranged on the grid side;

[0007] a driving module, comprising a first driving unit connected to the first relay, a second driving unit connected to the second relay, a third driving unit connected to the third relay and the fourth relay, and a fourth driving unit connected to the fifth relay and the sixth relay;

[0008] The signal acquisition module includes a first acquisition unit connected between the first end of the first relay and the first end of the second relay, a second acquisition unit connected between the second end of the first relay and the second end of the second relay, a third acquisition unit connected between the first end of the fifth relay and the first end of the fourth relay, and a fourth acquisition unit connected between the second end of the fifth relay and the second end of the fourth relay.

[0009] Optionally, the device further includes a first control module and a second control module; the first drive unit, the second drive unit, the third drive unit, and the fourth drive unit have the same drive circuit, and the drive circuit includes a first switch circuit, a second switch circuit, a third switch circuit, and a first voltage source;

[0010] The control end of the first switch circuit is connected to the first control module, the first end of the first switch circuit is connected to the first voltage source, and the second end of the first switch circuit is grounded;

[0011] The control end of the second switch circuit is connected to the first end of the first switch circuit, the first end of the second switch circuit is connected to the first control end of the relay, and the second end of the second switch circuit is grounded;

[0012] The control end of the third switch circuit is connected to the second control module, the first end of the third switch circuit is connected to the control end of the second switch circuit, and the second end of the third switch circuit is grounded.

[0013] Optionally, the first switch circuit includes: a first pull-up resistor, a first current limiting resistor, a first driving transistor, a first pull-down resistor, a first filter capacitor, a second current limiting resistor and a first parasitic diode;

[0014] A first end of the first pull-up resistor is connected to the first voltage source, and a second end of the first pull-up resistor is connected to a first end of the first current limiting resistor;

[0015] A first end of the first current limiting resistor is connected to the first control module, and a second end of the first current limiting resistor is connected to the control end of the first driving transistor;

[0016] A first end of the first pull-down resistor is connected to the control end of the first driving transistor, and a second end of the first pull-down resistor is grounded;

[0017] A first end of the first filter capacitor is connected to the control end of the first driving transistor, and a second end of the first filter capacitor is grounded;

[0018] A first terminal of the first driving transistor is connected to the first voltage source through the second current limiting resistor, and a second terminal of the first driving transistor is grounded;

[0019] An anode of the first parasitic diode is connected to the second end of the first driving transistor, and a cathode of the first parasitic diode is connected to the first end of the first driving transistor.

[0020] Optionally, the second switch circuit includes: a third current limiting resistor, a second driving transistor, a second pull-down resistor, a second parasitic diode and an absorption circuit, and the absorption circuit includes an absorption resistor and an absorption capacitor;

[0021] The control end of the second driving transistor is connected to the first end of the first switch circuit through the third current limiting resistor, the first end of the second driving transistor is connected to the first control end of the relay, and the second end of the second driving transistor is grounded;

[0022] A first end of the second pull-down resistor is connected to the control end of the second driving transistor, and a second end of the second pull-down resistor is grounded;

[0023] An anode of the second parasitic diode is connected to the second end of the second driving transistor, and a cathode of the second parasitic diode is connected to the first end of the second driving transistor;

[0024] A first end of the absorption resistor is connected to a first end of the second driving transistor, and a second end of the absorption resistor is grounded through the absorption capacitor.

[0025] Optionally, the third switch circuit includes: a second pull-up resistor, a fourth current limiting resistor, a third driving transistor, a third pull-down resistor and a second filter capacitor;

[0026] A first end of the second pull-up resistor is connected to the first voltage source, and a second end of the second pull-up resistor is connected to a first end of the fourth current limiting resistor;

[0027] A first end of the fourth current limiting resistor is connected to the second control module, and a second end of the fourth current limiting resistor is connected to the control end of the third driving transistor;

[0028] A first terminal of the third driving transistor is connected to the control terminal of the second switch circuit, and a second terminal of the third driving transistor is grounded;

[0029] A first end of the third pull-down resistor is connected to the control end of the third driving transistor, and a second end of the third pull-down resistor is grounded;

[0030] A first end of the second filter capacitor is connected to the control end of the third driving transistor, and a second end of the second filter capacitor is grounded.

[0031] Optionally, the driving circuit further includes a second voltage source, and the second voltage source is connected to the second control terminal of the relay.

[0032] Optionally, the device further includes a first control module and a second control module; the first acquisition unit, the second acquisition unit, the third acquisition unit, and the fourth acquisition unit have the same signal acquisition circuit, and the signal acquisition circuit includes: a voltage divider circuit, an amplification circuit, and a filter circuit;

[0033] The first input end of the voltage divider circuit is connected to the grid-connected live wire, the second input end of the voltage divider circuit is connected to the grid-connected neutral wire, the first output end of the voltage divider circuit is connected to the first input end of the amplifier circuit, and the second output end of the voltage divider circuit is connected to the second input end of the amplifier circuit; the output end of the amplifier circuit is connected to the input end of the filter circuit, and the output end of the filter circuit is respectively connected to the first control module and the second control module.

[0034] Optionally, the voltage divider circuit includes a first voltage divider circuit and a second voltage divider circuit;

[0035] The first end of the first voltage divider circuit is connected to the grid live line, and the second end of the first voltage divider circuit is connected to the first input end of the amplifier circuit; the first end of the second voltage divider circuit is connected to the grid neutral line, and the second end of the second voltage divider circuit is connected to the second input end of the amplifier circuit;

[0036] The first voltage-dividing circuit includes at least one first voltage-dividing resistor connected in series, and the second voltage-dividing circuit includes at least one second voltage-dividing resistor connected in series.

[0037] Optionally, the amplifying circuit includes: a third voltage source, an operational amplifier, a bias circuit and a feedback circuit, the bias circuit includes a bias resistor and a third filter capacitor, and the feedback circuit includes a feedback resistor and a fourth filter capacitor;

[0038] The non-inverting input terminal of the operational amplifier is connected to the first output terminal of the voltage divider circuit, and the inverting input terminal of the operational amplifier is connected to the second output terminal of the voltage divider circuit;

[0039] The bias resistor and the third filter capacitor are connected in parallel between the third voltage source and the non-inverting input terminal of the operational amplifier;

[0040] The feedback resistor and the fourth filter capacitor are connected in parallel between the inverting input terminal of the operational amplifier and the output terminal of the operational amplifier.

[0041] Optionally, the filtering circuit includes: a first filtering resistor, a fifth filtering capacitor, a second filtering resistor and a sixth filtering capacitor;

[0042] A first end of the first filter resistor is connected to the output end of the amplifier circuit, and a second end of the first filter resistor is connected to the first control module;

[0043] The first end of the fifth filter capacitor is connected to the second end of the first filter resistor, and the second end of the fifth filter capacitor is grounded;

[0044] A first end of the second filter resistor is connected to the output end of the amplifier circuit, and a second end of the second filter resistor is connected to the second control module;

[0045] The first end of the sixth filter capacitor is connected to the second end of the second filter resistor, and the second end of the sixth filter capacitor is grounded.

[0046] The utility model provides a grid-connected relay self-test device, the device comprising a circuit to be tested, the circuit to be tested comprising a first relay, a third relay and a fifth relay connected in series in sequence on a grid-connected live line between an inverter and a power grid, and a second relay, a sixth relay and a fourth relay connected in series in sequence on a grid-connected neutral line between the inverter and the power grid, wherein the first relay and the second relay are arranged on the inverter side, and the fifth relay and the fourth relay are arranged on the power grid side; a driving module connected to the circuit to be tested, the driving module comprising a first driving unit connected to the first relay, a second driving unit connected to the second relay, a third driving unit connected to the third relay and the fourth relay, and a fourth driving unit connected to the fifth relay and the sixth relay; a signal acquisition module connected to the circuit to be tested, the signal acquisition module comprising a first acquisition unit connected between the inverter and a first relay group, a second acquisition unit connected between the first relay group and the second relay group, a third acquisition unit connected between the second relay group and the third relay group, and a fourth acquisition unit connected between the third relay group and the power grid, wherein the first relay group comprises a first relay and a second relay, the second relay group comprises a third relay and a sixth relay, and the third relay group comprises a fifth relay and a fourth relay. The grid-connected relay self-checking device provided by the utility model drives six relays through four driving units, and collects signals after the relays are actuated through four collecting units, thereby realizing self-checking of three groups of grid-connected relays and improving the self-checking efficiency of the relays.

[0047] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0049] Figure 1 A schematic diagram of grid connection and off-grid connection provided by an embodiment of the utility model is shown;

[0050] Figure 2 A schematic structural diagram of a grid-connected relay self-test device provided by an embodiment of the utility model is shown;

[0051] Figure 3 A schematic structural diagram of another grid-connected relay self-test device provided by an embodiment of the utility model is shown;

[0052] Figure 4 A schematic diagram of the structure of a circuit to be tested provided by an embodiment of the utility model is shown;

[0053] Figure 5 A schematic diagram of a driving signal provided by an embodiment of the utility model is shown;

[0054] Figure 6 A circuit diagram of a driving circuit provided by an embodiment of the utility model is shown;

[0055] Figure 7 A circuit diagram of a signal acquisition circuit provided by an embodiment of the utility model is shown.

[0056] Illustration Description:

[0057] RLY1-first relay; RLY2-second relay; RLY3-third relay; RLY4-fourth relay; RLY5-fifth relay; RLY6-sixth relay; Q1-first drive transistor; Q2-second drive transistor; Q3-third drive transistor; D1-first parasitic diode; D2-second parasitic diode; R1-first pull-up resistor; R2-first current limiting resistor; R3-first pull-down resistor; R4-second current limiting resistor; R5-third current limiting resistor; R6-second pull-down resistor ; R7-absorption resistor; R8-second pull-up resistor; R9-fourth current limiting resistor; R10-third pull-down resistor; R11 to R16-first voltage-dividing resistor; R17 to R22-second voltage-dividing resistor; R23-bias resistor; R24-feedback resistor; R25-first filter resistor; R26-second filter resistor; C1-first filter capacitor; C2-absorption capacitor; C3-second filter capacitor; C4-third filter capacitor; C5-fourth filter capacitor; C6-fifth filter capacitor; C7-sixth filter capacitor. DETAILED DESCRIPTION

[0058] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict.

[0059] In one embodiment, Figure 2 As shown, a grid-connected relay self-test device is provided, including: a driving module, a circuit to be tested and a signal acquisition module. The driving module is used to convert the received control signal into a driving signal and input it into the circuit to be tested to drive the relay in the circuit to be tested to act, and the signal acquisition module is used to collect the action signal in the circuit to be tested and convert the action signal into a sampling signal. The grid-connected relay self-test device provided in this embodiment may also include a control module, which is used to provide a control signal to the driving module and receive the sampling signal output by the signal acquisition module, so as to determine whether each relay has a fault based on the driving signal and the sampling signal according to the preset relay self-test logic. The relay self-test logic can be set as needed, which is not specifically limited in this embodiment. The control module can determine whether the relay has a fault based on the driving signal and the sampling signal through a program module in the prior art, which is not specifically limited in this embodiment.

[0060] In this embodiment, if Figure 3 and Figure 4As shown, the circuit to be tested includes a first relay RLY1, a third relay RLY3 and a fifth relay RLY5 connected in series on the grid-connected live line L between the inverter and the grid side, and a second relay RLY2, a sixth relay RLY6 and a fourth relay RLY4 connected in series on the grid-connected neutral line N between the inverter and the grid side, wherein the first relay RLY1 and the second relay RLY2 are arranged on the inverter side, and the fifth relay RLY5 and the fourth relay RLY4 are arranged on the grid side. The driving module includes a first driving unit connected to the first relay RLY1, a second driving unit connected to the second relay RLY2, a third driving unit connected to the third relay RLY3 and the fourth relay RLY4, and a fourth driving unit connected to the fifth relay RLY5 and the sixth relay RLY6.

[0061] In this embodiment, the first drive unit is used to provide a first drive signal to the first relay RLY1, the second drive unit is used to provide a second drive signal to the second relay RLY2, the third drive unit is used to provide a third drive signal to the third relay RLY3 and the fourth relay RLY4 at the same time, and the fourth drive unit is used to provide a fourth drive signal to the fifth relay RLY5 and the sixth relay RLY6 at the same time. The embodiment of the present application drives six relays through four drive units, wherein two drive units drive two relays at the same time. Compared with a device in which each drive unit drives only one relay, this embodiment can save device costs, and only needs to process four groups of control signals, which can simplify the steps of logical judgment of the self-test process and improve the efficiency of relay self-test.

[0062] In this embodiment, the signal acquisition module includes a first acquisition unit connected between the first end of the first relay RLY1 and the first end of the second relay RLY2, a second acquisition unit connected between the second end of the first relay RLY1 and the second end of the second relay RLY2, a third acquisition unit connected between the first end of the fifth relay RLY5 and the first end of the fourth relay RLY4, and a fourth acquisition unit connected between the second end of the fifth relay RLY5 and the second end of the fourth relay RLY4.

[0063] In this embodiment, the first acquisition unit is used to acquire the first voltage between the first end of the first relay RLY1 and the first end of the second relay RLY2, that is, the voltage on the inverter side, to obtain a first sampling signal. The second acquisition unit is used to acquire the second voltage between the second end of the first relay RLY1 and the second end of the second relay RLY2, to obtain a second sampling signal. The third acquisition unit is used to acquire the third voltage between the first end of the fifth relay RLY5 and the first end of the fourth relay RLY4, to obtain a third sampling signal. The fourth acquisition unit is used to acquire the fourth voltage between the second end of the fifth relay RLY5 and the second end of the fourth relay RLY4, that is, the voltage on the grid side, to obtain a fourth sampling signal. Among them, the first end of the relay is the end of the relay close to the inverter side, and the second end of the relay is the end of the relay close to the grid side. In this embodiment, according to the voltage relationship between the inverter side, the grid side and each group of relays, the action state of each relay can be obtained. By comparing the drive signal with the action state of each relay, it can be determined whether each relay acts according to the drive signal, and then it can be determined whether the relay fails and the type of the fault.

[0064] The grid-connected relay self-test device provided in this embodiment drives six relays through four driving units, and collects the signals after the relays are actuated through four collecting units, so as to realize the self-test of three groups of grid-connected relays, wherein the driving unit can raise the control signal to generate a driving signal capable of driving the relays to actuate, and the collecting unit can convert the grid-connected action signal in the circuit to be tested into a sampling signal that is easy to process, so as to realize the grid-connected relay self-test by using the preset self-test logic. Figure 5 As shown, the self-test logic of the relay can include the following:

[0065] (1) All relays have no sticking faults: see Figure 5 , from t0 to t1, the first drive signal, the second drive signal, the third drive signal and the fourth drive signal are all low level, at this time all relays should be disconnected, the inverter voltage modulation wave, when all relays are not faulty, the first voltage is equal to the inverter side voltage, the second voltage and the third voltage are equal to zero volts, and the fourth voltage is equal to the grid side voltage;

[0066] (2) Check whether the second relay RLY2 has a sticking fault: see Figure 5, from t1 to t2, the first drive signal is at a high level, and the second drive signal, the third drive signal and the fourth drive signal are all at a low level. At this time, the first relay RLY1 should be closed, and the other relays remain open. At this time, if the second relay RLY2 does not have a sticking fault, the first voltage is equal to the inverter side voltage, the second voltage and the third voltage are equal to zero volts, and the fourth voltage is equal to the grid side voltage; if the second relay RLY2 has a sticking fault, the second voltage is equal to the first voltage, which is the inverter side voltage, the third voltage is zero volts, and the fourth voltage is equal to the grid side voltage.

[0067] (3) Check whether the first relay RLY1 has a sticking fault: see Figure 5 , from t2 to t3, the second drive signal is high level, the first drive signal, the third drive signal and the fourth drive signal are all low level, at this time the second relay RLY2 should be closed, and the other relays remain open. At this time, if the first relay RLY1 has a sticking fault, the first voltage is equal to the inverter side voltage, the second voltage and the third voltage are both zero volts, and the fourth voltage is equal to the grid side voltage; if the first relay RLY1 has a sticking fault, the second voltage is equal to the first voltage, which is the inverter side voltage, the third voltage is zero volts, and the fourth voltage is equal to the grid side voltage.

[0068] (4) Check whether the first relay RLY1 and the second relay RLY2 have a failure to close: see Figure 5 , from t3 to t4, the first drive signal and the second drive signal are high level, the third drive signal and the fourth drive signal are low level, at this time, the first relay RLY1 and the second relay RLY2 should be closed, and the other relays remain open. If the first relay RLY1 and the second relay RLY2 can be closed normally, the second voltage is equal to the first voltage, which is the inverter side voltage, the third voltage is zero volts, and the fourth voltage is the grid side voltage; if at least one of the first relay RLY1 and the second relay RLY2 cannot be closed, the first voltage is equal to the inverter side voltage, the second voltage and the third voltage are equal to zero volts, and the fourth voltage is the grid side voltage.

[0069] (5) Check whether the fifth relay RLY5 and the sixth relay RLY6 have adhesion faults: see Figure 5, from t4 to t5, the first drive signal, the second drive signal and the third drive signal are high level, and the fourth drive signal is low level. At this time, the first relay RLY1, the second relay RLY2, the third relay RLY3 and the fourth relay RLY4 should be closed, and the other relays remain open. If the fifth relay RLY5 and the sixth relay RLY6 do not have adhesion faults, the first voltage is equal to the inverter side voltage, the second voltage and the third voltage are equal to zero volts, and the fourth voltage is equal to the grid side voltage; if the fifth relay RLY5 has an adhesion fault and the sixth relay RLY6 is normal, the first voltage is equal to the inverter side voltage, the second voltage is zero volts, and the third voltage is equal to the fourth voltage, which is the grid side voltage; if the sixth relay RLY6 has an adhesion fault and the fifth relay RLY5 is normal, the second voltage is equal to the first voltage, which is the inverter side voltage, the third voltage is zero volts, and the fourth voltage is equal to the grid side voltage.

[0070] (6) Check whether the third relay RLY3 and the fourth relay RLY4 have adhesion faults: see Figure 5 , from t5 to t6, the first drive signal, the second drive signal and the fourth drive signal are at a high level, and the third drive signal is at a low level. At this time, the first relay RLY1, the second relay RLY2, the fifth relay RLY5 and the sixth relay RLY6 are closed, and the other relays remain open. If neither the third relay RLY3 nor the fourth relay RLY4 has a sticking fault, the first voltage is equal to the inverter side voltage, the second voltage is equal to the third voltage and is zero volts, and the fourth voltage is equal to the grid side voltage; if the fourth relay RLY4 has a sticking fault and the third relay RLY3 is normal, the first voltage is equal to the inverter side voltage, the second voltage is zero volts, and the third voltage is equal to the fourth voltage, which is the grid side voltage; if the third relay RLY3 has a sticking fault and the fourth relay RLY4 is normal, the second voltage is equal to the first voltage, which is the inverter side voltage, the third voltage is zero volts, and the fourth voltage is equal to the grid side voltage.

[0071] (7) Check whether the third relay RLY3, the fourth relay RLY4, the fifth relay RLY5, and the sixth relay RLY6 have a failure to close: see Figure 5, from t6 to t7, the first drive signal and the second drive signal are low level, and the third drive signal and the fourth drive signal are high level. At this time, the three relays RLY3, the fourth relay RLY4, the fifth relay RLY5, and the sixth relay RLY6 should be closed, and the other relays remain open. If the third relay RLY3, the fourth relay RLY4, the fifth relay RLY5, and the sixth relay RLY6 can all be closed normally, then the first voltage is equal to the inverter side voltage, and the second voltage and the third voltage are equal to the fourth voltage, which is the grid side voltage; if at least one of the third relay RLY3 and the sixth relay RLY6 fails to close, and the fourth relay RLY4 and the fifth relay RLY5 are normal, then the first voltage is equal to the inverter side voltage, the second voltage is zero volts, and the third voltage is equal to the fourth voltage, which is the grid side voltage; if at least one of the fourth relay RLY4 and the fifth relay RLY5 fails to close, then the first voltage is equal to the inverter side voltage, the second voltage and the third voltage are zero volts, and the fourth voltage is equal to the grid side voltage.

[0072] After (1) to (7), all relays are tested for adhesion faults or inability to close faults. After determining that all active electrical appliances can be closed and disconnected normally, the phase-locked logic is used to generate waves to complete the grid connection. In this embodiment, the above relay self-test logic is only an example for facilitating the understanding of the application of the relay self-test device provided by the present application, and does not constitute a limitation on the present embodiment. The relay self-test logic can be designed as needed. The relay fault judgment during the self-test process can be implemented by the program module or function in the prior art, and does not constitute the limitation scope of the present application.

[0073] In an optional embodiment, the grid-connected relay self-test device provided in the embodiment of the present application further includes a first control module and a second control module. The first drive unit, the second drive unit, the third drive unit, and the fourth drive unit have the same drive circuit. Figure 6 As shown, the driving circuit includes a first switch circuit, a second switch circuit, a third switch circuit and a first voltage source; the control end of the first switch circuit is connected to the first control module, the first end of the first switch circuit is connected to the first voltage source, and the second end of the first switch circuit is grounded; the control end of the second switch circuit is connected to the first end of the first switch circuit, the first end of the second switch circuit is connected to the first control end of the relay, and the second end of the second switch circuit is grounded; the control end of the third switch circuit is connected to the second control module, the first end of the third switch circuit is connected to the control end of the second switch circuit, and the second end of the third switch circuit is grounded.

[0074] In the above embodiment, the first control module is used to input a first control signal to the control end of the first switch circuit, and the second control module is used to input a second control signal to the control end of the third switch circuit. The first switch circuit and the second switch circuit constitute a first drive circuit, and the third switch circuit and the second switch circuit constitute a second drive circuit. When the first switch circuit and the third switch circuit are both not conducting, the second switch circuit is conducting at this time, and the relay will be controlled to close; if any one of the first switch circuit and the third switch circuit is conducting at this time, the second switch circuit is not conducting, and the relay will be controlled to be disconnected. Among them, the functions of the first control module and the second control module can be implemented by programs in the prior art, for example, the first control module can be a first single-chip microcomputer, and the second control module can be a second single-chip microcomputer.

[0075] In the above embodiment, in the initial state, that is, when the relay is not controlled, the first control signal output by the first control module and the second control signal output by the second control module can both be high level, at which time the first switch circuit and the third switch circuit are both turned on, and the second switch circuit is not turned on, so that the relay remains in the disconnected state. When it is necessary to drive the relay to close, the first control signal output by the first control module and the second control signal output by the second control module are simultaneously set to a low level, at which time the first switch circuit and the third switch circuit are not turned on, so that the second switch circuit is turned on to control the relay to close. Among them, the high and low levels output by the first control module and the second control module can be manually controlled each time, or a communication connection can be established between the first control module and the second control module. When a high or low level control instruction is input to one of the control modules, the control instruction is transmitted to the other control module through the communication module at the same time, so as to realize that the first control module and the second control module simultaneously output a high or low level control signal. This embodiment realizes redundant disconnection control by setting the first drive circuit and the second drive circuit to avoid the situation where the relay cannot be disconnected in time when the first control module or the second control module fails.

[0076] In an optional embodiment, the first switch circuit includes: a first pull-up resistor R1, a first current limiting resistor R2, a first driving transistor Q1, a first pull-down resistor R3, a first filter capacitor C1, a second current limiting resistor R4 and a first parasitic diode D1; a first end of the first pull-up resistor R1 is connected to the first voltage source, and a second end of the first pull-up resistor R1 is connected to a first end of the first current limiting resistor R2; a first end of the first current limiting resistor R2 is connected to the first control module, and a second end of the first current limiting resistor R2 is connected to a control end of the first driving transistor Q1; a first end of the first pull-down resistor R3 is connected to the control end of the first driving transistor Q1, and a second end of the first pull-down resistor R3 is grounded; a first end of the first filter capacitor C1 is connected to the control end of the first driving transistor Q1, and a second end of the first filter capacitor C1 is grounded; a first end of the first driving transistor Q1 is connected to the first voltage source through the second current limiting resistor R4, and a second end of the first driving transistor Q1 is grounded; an anode of the first parasitic diode D1 is connected to a second end of the first driving transistor Q1, and a cathode of the first parasitic diode D1 is connected to a first end of the first driving transistor Q1.

[0077] In the above embodiment, the first end of the first pull-up resistor R1 is connected to the first voltage source, and the second end of the first pull-up resistor R1 is connected to the control end of the first driving transistor Q1 through the first current limiting resistor R2, which is used to ensure that in the initial state, the control end voltage of the first driving transistor Q1 is stabilized at a high level, and the first driving transistor Q1 remains in the on state. At this time, the first end of the first driving transistor Q1 is connected to the second end, and the control end of the second switch circuit connected to the first end of the first driving transistor Q1 is at a low level. At this time, the second switch circuit cannot be turned on, and the relay remains in the off state. The first pull-down resistor R3 and the first filter capacitor C1 are used to release interference signals and stabilize the voltage signal of the first driving transistor Q1. The second current limiting resistor R4 is used to limit the current flowing through the first driving transistor Q1 to avoid damage to the first driving transistor Q1. The first parasitic diode D1 is used to protect the first driving transistor D1. If a large instantaneous reverse current is generated in the circuit, it will be conducted through the first parasitic diode D1 to protect the first driving transistor D1 from being burned out. When the voltage between the first end and the second end of the first driving transistor D1 is too large, the first parasitic diode D1 will be reversely broken down before the first driving transistor D1 to prevent the first driving transistor D1 from being burned out. The first control module is connected to the control end of the first driving transistor D1 through the first current limiting resistor R2, and is used to input a first control signal to the first driving transistor D1. When the first control signal is at a low level, the first driving transistor D1 is not turned on, and when the first control signal is at a high level, the first driving transistor Q1 is turned on.

[0078] In an optional embodiment, the second switch circuit includes: a third current limiting resistor R5, a second drive transistor Q2, a second pull-down resistor R6, a second parasitic diode D2 and an absorption circuit, wherein the absorption circuit includes an absorption resistor R7 and an absorption capacitor C2; the control end of the second drive transistor Q2 is connected to the first end of the first switch circuit through the third current limiting resistor R5, the first end of the second drive transistor Q2 is connected to the first control end of the relay, and the second end of the second drive transistor Q2 is grounded; the first end of the second pull-down resistor R6 is connected to the control end of the second drive transistor Q2, and the second end of the second pull-down resistor R6 is grounded; the anode of the second parasitic diode D2 is connected to the second end of the second drive transistor Q2, and the cathode of the second parasitic diode D2 is connected to the first end of the second drive transistor Q2; the first end of the absorption resistor R7 is connected to the first end of the second drive transistor Q2, and the second end of the absorption resistor R7 is grounded through the absorption capacitor C2.

[0079] In the above embodiment, the control end of the second driving transistor Q2 is connected to the first end of the first switch circuit, that is, to the first end of the first driving transistor Q1, through the third current limiting resistor R5. The third current limiting resistor R5 is used to limit the current flowing through the second driving transistor Q2 to protect the second driving transistor Q2 from being burned out. The second pull-down resistor R6 is used to release the interference signal to prevent the second driving transistor Q2 from malfunctioning due to the interference signal superimposed in the circuit. The absorption resistor R7 and the absorption capacitor C2 are used to absorb the oscillation signal generated in the circuit to prevent the second driving transistor Q2 from being broken down. The function of the second parasitic diode D2 is similar to that of the first parasitic diode, and is used to protect the second driving transistor Q2 from being burned out. When the control end voltage of the second driving transistor Q2 is at a high level, the second driving transistor Q2 is turned on, and at this time, the first end of the second driving transistor Q2 is at a low level, the first control end of the relay is connected to the first end of the second driving transistor Q2, and the control end of the relay is connected to the second voltage source. When the first end of the second driving transistor Q2 is at a low level, the relay is closed. When the control terminal of the second driving transistor Q2 is at a low level, the second driving transistor Q2 is not turned on. At this time, the first terminal of the second driving transistor Q2 is clamped to a high level, and the relay is disconnected.

[0080] In an optional embodiment, the third switch circuit includes: a second pull-up resistor R8, a fourth current limiting resistor R9, a third drive transistor Q3, a third pull-down resistor R10 and a second filter capacitor C3; the first end of the second pull-up resistor R8 is connected to the first voltage source, and the second end of the second pull-up resistor R8 is connected to the first end of the fourth current limiting resistor R9; the first end of the fourth current limiting resistor R9 is connected to the second control module, and the second end of the fourth current limiting resistor R9 is connected to the control end of the third drive transistor Q3; the first end of the third drive transistor Q3 is connected to the control end of the second switch circuit, and the second end of the third drive transistor Q3 is grounded; the first end of the third pull-down resistor R10 is connected to the control end of the third drive transistor Q3, and the second end of the third pull-down resistor R10 is grounded; the first end of the second filter capacitor C3 is connected to the control end of the third drive transistor Q3, and the second end of the second filter capacitor C3 is grounded.

[0081] In the above embodiment, the first end of the second pull-up resistor R8 is connected to the first voltage source, and the second end of the second pull-up resistor R8 is connected to the control end of the third driving transistor Q3 through the fourth current limiting resistor R9, which is used to keep the control end of the third driving transistor Q3 at a high level when the second control module is not in operation, so that the third driving transistor Q3 is turned on, and the input end of the second switch circuit connected to the first end of the third driving transistor Q3 is at a low level, the second switch circuit cannot be turned on, and the relay is kept in a disconnected state. The second filter capacitor C3 and the third pull-down resistor R10 are used to filter out interference signals and stabilize the voltage of the third driving transistor Q3.

[0082] In the above embodiment, in the initial state, the first control signal input by the first control module to the first switch circuit can be maintained at a high level to turn on the first switch circuit, and the second control signal input by the second control module to the third switch circuit can also be maintained at a low level to turn off the third switch circuit. At this time, the control end of the second switch circuit is at a low level, and the second switch circuit is not turned on, so that the relay remains in an open state. When it is necessary to drive the relay to close, it is only necessary to set the first control signal of the first switch circuit to a low level. At this time, both the first switch circuit and the third switch circuit are in a non-conducting state, the control end of the second switch circuit is at a high level, and the second switch circuit is turned on to control the relay to close. Therefore, the first drive path composed of the first switch circuit and the second switch circuit can be regarded as the main drive path, and accordingly, the first control module is the main control module, and the second drive path composed of the third switch circuit and the second switch circuit can be regarded as the auxiliary drive path, and accordingly, the second control module is the auxiliary control module. The second control signal is set to a low level to turn off the third drive transistor Q3, and when controlling the relay to turn on and off, it is only necessary for the first control module to control the first switch circuit and the second switch circuit to act. If the first control module fails and cannot drive the relay to disconnect, the second control signal is set to a high level to drive the third drive transistor Q3 to turn on and disconnect the relay. That is, usually only the first drive transistor Q1 and the second drive transistor Q2 need to be operated, and the third drive transistor Q3 is usually in a non-conducting state. Therefore, the first drive transistor Q1 and the second drive transistor Q2 can select MOS tubes with faster operation, and the third drive transistor Q3 can select a triode to save costs.

[0083] In an optional embodiment, the driving circuit further includes: a second voltage source connected to the second control terminal of the relay. The second voltage source is used to provide a high level capable of driving the relay to operate for the second control terminal of the relay.

[0084] In the above embodiment, when the first control signal input by the first control module and the second control signal input by the second control module are both at a low level, the first switch circuit and the third switch circuit are not turned on. At this time, the control end of the second switch circuit is at a high level, the second switch circuit is turned on, and the control relay is closed. When any one of the first control signal input by the first control module and the second control signal input by the second control module is at a high level, the control end of the second switch circuit is at a low level, the second switch circuit cannot be turned on, and the control relay is turned off. Through the above scheme, when the first control module fails and cannot control the relay to be turned off, the relay can be controlled to be turned off by the second control module, thereby improving the safety and reliability of the grid-connected relay self-test device.

[0085] In an optional embodiment, the first acquisition unit, the second acquisition unit, the third acquisition unit, and the fourth acquisition unit have the same signal acquisition circuit. Figure 7 As shown, the signal acquisition circuit includes: a voltage divider circuit, an amplifier circuit, and a filter circuit; the first input end of the voltage divider circuit is connected to the grid-connected live wire L, the second input end of the voltage divider circuit is connected to the grid-connected neutral wire N, the first output end of the voltage divider circuit is connected to the first input end of the amplifier circuit, and the second output end of the voltage divider circuit is connected to the second input end of the amplifier circuit; the output end of the amplifier circuit is connected to the input end of the filter circuit, and the output end of the filter circuit is respectively connected to the first control module and the second control module.

[0086] In the above embodiment, the voltage divider circuit is used to convert the grid-connected 220V high-voltage signal into a low-voltage signal that can be processed by the chip, and to isolate the high-voltage signal from the low-voltage signal, wherein the high-voltage signal refers to the grid-connected 220V AC signal, and the low-voltage signal refers to a low-voltage signal that can be processed by a weak current chip, such as an operational amplifier, after being divided by the voltage divider circuit. The amplifier circuit is used to convert the low-voltage signal output by the voltage divider circuit into a signal that can be processed by a control module, such as a single-chip microcomputer. The filter circuit is used to filter the signal output by the amplifier circuit to obtain a sampling signal, and input the sampling signal to the first control module and the second control module, so that the first control module and the second control module can detect whether the relay is faulty according to the relay self-test logic.

[0087] In an optional embodiment, the voltage divider circuit includes a first voltage divider circuit and a second voltage divider circuit; the first end of the first voltage divider circuit is connected to the grid-connected live line L, and the second end of the first voltage divider circuit is connected to the first input end of the amplifier circuit; the first end of the second voltage divider circuit is connected to the grid-connected neutral line N, and the second end of the second voltage divider circuit is connected to the second input end of the amplifier circuit; the first voltage divider circuit includes at least one first voltage divider resistor connected in series, and the second voltage divider circuit includes at least one second voltage divider resistor connected in series.

[0088] In the above embodiment, the first voltage-dividing resistor and the second voltage-dividing resistor may be one or more plug-in resistors connected in series, or may be multiple chip resistors connected in series, so as to meet the safety requirements for isolating the high-voltage circuit and the low-voltage circuit. Figure 7As shown, the first voltage-dividing resistor may include first voltage-dividing resistors R11 to R16 connected in series, and the second voltage-dividing resistor may include second voltage-dividing resistors R17 to R22 connected in series. By using multiple first voltage-dividing resistors connected in series and multiple second voltage-dividing resistors connected in series, while meeting the requirements of safety distance, multiple voltage-dividing resistors can also be used to share power loss and extend the service life of the components. The resistance value of the voltage-dividing resistor can be set as needed.

[0089] In an optional embodiment, the amplification circuit includes: a third voltage source, an operational amplifier U1, a bias circuit and a feedback circuit, the bias circuit includes a bias resistor R23 and a third filter capacitor C4, and the feedback circuit includes a feedback resistor R24 ​​and a fourth filter capacitor C5; the non-inverting input terminal of the operational amplifier U1 is connected to the first output terminal of the voltage divider circuit, and the inverting input terminal of the operational amplifier U1 is connected to the second output terminal of the voltage divider circuit; the bias resistor R23 and the third filter capacitor C4 are connected in parallel between the third voltage source and the non-inverting input terminal of the operational amplifier U1; the feedback resistor R24 ​​and the fourth filter capacitor C5 are connected in parallel between the inverting input terminal of the operational amplifier U1 and the output terminal of the operational amplifier U1.

[0090] In the above embodiment, the third voltage source and the bias resistor R23 are used to provide a bias voltage for the operational amplifier, so that the operational amplifier U1 and the feedback resistor R24 ​​amplify the low-voltage small signal output by the voltage divider circuit and add the bias voltage to obtain a signal that can be processed by the control module. For example, assuming that the operational amplifier U1 amplifies the small signal output by the voltage divider circuit to obtain a voltage of -1.5 volts to 1.5 volts, the third voltage source can be set to 1.5 volts, so that the signal output by the operational amplifier U1 remains between 0 and 3 volts, so that the control module can process it. The third filter capacitor C4 and the fourth filter capacitor C5 are used to filter out interference signals in the circuit.

[0091] In an optional embodiment, the filtering circuit includes: a first filter resistor R25, a fifth filter capacitor C6, a second filter resistor R26 and a sixth filter capacitor C7; the first end of the first filter resistor R25 is connected to the output end of the amplifier circuit, and the second end of the first filter resistor R25 is connected to the first control module; the first end of the fifth filter capacitor C6 is connected to the second end of the first filter resistor R25, and the second end of the fifth filter capacitor C6 is grounded; the first end of the second filter resistor R26 is connected to the output end of the amplifier circuit, and the second end of the second filter resistor R26 is connected to the second control module; the first end of the sixth filter capacitor C7 is connected to the second end of the second filter resistor R26, and the second end of the sixth filter capacitor C7 is grounded.

[0092] In the above embodiment, the first filter resistor R25 and the fifth filter capacitor C6 form a first filter path, the signal output by the operational amplifier U1 is filtered by the first filter resistor R25 to obtain a first sampling signal, and the first sampling signal is output to the first control module; the second filter resistor R26 and the sixth filter capacitor C7 form a second filter path, the signal output by the operational amplifier U1 is filtered by the second filter resistor R26 to obtain a second sampling signal, and the second sampling signal is output to the second control module. So that the first control module performs self-test on the relay according to the first control signal, the second control signal and the first sampling signal, and / or the second control module performs self-test on the relay according to the first control signal, the second control signal and the second sampling signal. In this embodiment, the purpose of setting two filter paths is to output the acquisition signal to the first control module and the second control module respectively, wherein the first control module and the second control module can also send the respective received acquisition signals to each other through their respective communication modules. If one of the control modules fails, the relay self-test can be realized through the other control module, thereby improving the stability of the relay self-test device.

[0093] In the above embodiment, the first control module and the second control module input the first control signal and the second control signal to the drive circuit respectively. When the first control signal and the second control signal are both at low levels, the drive unit drives the relay to close. When any one of the first control signal and the second control signal is at a high level, the drive unit drives the relay to disconnect. In the embodiment of the present application, six relays are controlled by four drive units. When performing relay fault detection, the self-check logic of the relay can be designed as needed, and the combination of different control signals input to the drive unit drives the relay to act. Then, the acquisition unit collects multiple action signals between the relays at different positions of the grid respectively, and converts the multiple action signals into multiple sampling signals and inputs them into the first control module and / or the second control module. The first control module and / or the second control module detect whether the relay has a fault and the type of fault based on the first control signal, the second control signal and the multiple sampling signals according to the preset relay self-check logic. Among them, the first control module and the second control module can design the self-check logic of the relay according to the needs, and the self-check process can be realized by using the program module in the prior art. The control of the first drive signal and the second drive signal can be realized by human control or by the program function in the prior art. The embodiment of the present application does not limit the first control module and the second control module.

[0094] By applying the technical solution of the present application, six relays can be driven by four driving units, and the signals after the relays are operated can be acquired by four acquisition units, so as to realize self-inspection of three groups of grid-connected relays, wherein the driving unit can raise the control signal of the control module to generate a driving signal capable of driving the relays to operate, and the acquisition unit can convert the grid-connected action signal in the circuit to be tested into a sampling signal that is easy to process, so as to realize self-inspection of the grid-connected relays by utilizing the preset self-inspection logic and improve the efficiency of self-inspection.

[0095] It is understandable that the selection of resistors, capacitors, amplifiers, transistors and other devices in the embodiments of the present application, as well as the numerical values ​​and signal types of control signals, can be selected and set according to the actual scenario of production design, and this embodiment does not make specific restrictions. In addition, the relay self-test logic set in the first control module and the second control module can also be implemented by the program module in the prior art, and this embodiment does not make specific restrictions.

[0096] It should be noted that the functions of the relay self-test device provided in this embodiment are mainly realized by the circuit connection relationship between the various circuit modules, and do not rely on the program module in a certain circuit module. In addition, for the circuit module that can be implanted with the program module, the realization of its module function can be realized by the program module provided by the prior art.

[0097] Those skilled in the art will appreciate that the accompanying drawings are only schematic diagrams of a preferred implementation scenario, and the modules or processes in the accompanying drawings are not necessarily necessary for implementing the present application. Those skilled in the art will appreciate that the modules in the devices in the implementation scenario can be distributed in the devices of the implementation scenario according to the description of the implementation scenario, or can be changed accordingly and located in one or more devices different from the present implementation scenario. The modules of the above-mentioned implementation scenario can be combined into one module, or can be further split into multiple submodules.

[0098] The above serial numbers of this application are only for description and do not represent the advantages and disadvantages of the implementation scenarios. The above disclosure is only a few specific implementation scenarios of this application, but this application is not limited to them, and any changes that can be thought of by technicians in this field should fall within the scope of protection of this application.

Claims

1. A grid-connected relay self-test device, characterized in that: The device comprises: The circuit to be tested includes a first relay, a third relay and a fifth relay connected in series in sequence on a grid-connected live line between an inverter and a grid side, and a second relay, a sixth relay and a fourth relay connected in series in sequence on a grid-connected neutral line between the inverter and the grid side, wherein the first relay and the second relay are arranged on the inverter side, and the fifth relay and the fourth relay are arranged on the grid side; a driving module, comprising a first driving unit connected to the first relay, a second driving unit connected to the second relay, a third driving unit connected to the third relay and the fourth relay, and a fourth driving unit connected to the fifth relay and the sixth relay; The signal acquisition module includes a first acquisition unit connected between the first end of the first relay and the first end of the second relay, a second acquisition unit connected between the second end of the first relay and the second end of the second relay, a third acquisition unit connected between the first end of the fifth relay and the first end of the fourth relay, and a fourth acquisition unit connected between the second end of the fifth relay and the second end of the fourth relay.

2. The device according to claim 1, characterized in that The device further comprises a first control module and a second control module; the first drive unit, the second drive unit, the third drive unit and the fourth drive unit have the same drive circuit, and the drive circuit comprises a first switch circuit, a second switch circuit, a third switch circuit and a first voltage source; The control end of the first switch circuit is connected to the first control module, the first end of the first switch circuit is connected to the first voltage source, and the second end of the first switch circuit is grounded; The control end of the second switch circuit is connected to the first end of the first switch circuit, the first end of the second switch circuit is connected to the first control end of the relay, and the second end of the second switch circuit is grounded; The control end of the third switch circuit is connected to the second control module, the first end of the third switch circuit is connected to the control end of the second switch circuit, and the second end of the third switch circuit is grounded.

3. The device according to claim 2, characterized in that The first switch circuit includes: a first pull-up resistor, a first current limiting resistor, a first driving transistor, a first pull-down resistor, a first filter capacitor, a second current limiting resistor and a first parasitic diode; A first end of the first pull-up resistor is connected to the first voltage source, and a second end of the first pull-up resistor is connected to a first end of the first current limiting resistor; A first end of the first current limiting resistor is connected to the first control module, and a second end of the first current limiting resistor is connected to the control end of the first driving transistor; A first end of the first pull-down resistor is connected to the control end of the first driving transistor, and a second end of the first pull-down resistor is grounded; A first end of the first filter capacitor is connected to the control end of the first driving transistor, and a second end of the first filter capacitor is grounded; A first terminal of the first driving transistor is connected to the first voltage source through the second current limiting resistor, and a second terminal of the first driving transistor is grounded; An anode of the first parasitic diode is connected to the second end of the first driving transistor, and a cathode of the first parasitic diode is connected to the first end of the first driving transistor.

4. The device according to claim 2, characterized in that The second switch circuit includes: a third current limiting resistor, a second driving transistor, a second pull-down resistor, a second parasitic diode and an absorption circuit, wherein the absorption circuit includes an absorption resistor and an absorption capacitor; The control end of the second driving transistor is connected to the first end of the first switch circuit through the third current limiting resistor, the first end of the second driving transistor is connected to the first control end of the relay, and the second end of the second driving transistor is grounded; A first end of the second pull-down resistor is connected to the control end of the second driving transistor, and a second end of the second pull-down resistor is grounded; An anode of the second parasitic diode is connected to the second end of the second driving transistor, and a cathode of the second parasitic diode is connected to the first end of the second driving transistor; A first end of the absorption resistor is connected to a first end of the second driving transistor, and a second end of the absorption resistor is grounded through the absorption capacitor.

5. The device according to claim 2, characterized in that The third switch circuit comprises: a second pull-up resistor, a fourth current limiting resistor, a third driving transistor, a third pull-down resistor and a second filter capacitor; A first end of the second pull-up resistor is connected to the first voltage source, and a second end of the second pull-up resistor is connected to a first end of the fourth current limiting resistor; A first end of the fourth current limiting resistor is connected to the second control module, and a second end of the fourth current limiting resistor is connected to the control end of the third driving transistor; A first terminal of the third driving transistor is connected to the control terminal of the second switch circuit, and a second terminal of the third driving transistor is grounded; A first end of the third pull-down resistor is connected to the control end of the third driving transistor, and a second end of the third pull-down resistor is grounded; A first end of the second filter capacitor is connected to the control end of the third driving transistor, and a second end of the second filter capacitor is grounded.

6. The device according to claim 2, characterized in that The driving circuit further includes: A second voltage source is connected to a second control terminal of the relay.

7. The device according to claim 1, characterized in that The device further includes a first control module and a second control module; the first acquisition unit, the second acquisition unit, the third acquisition unit, and the fourth acquisition unit have the same signal acquisition circuit, and the signal acquisition circuit includes: a voltage divider circuit, an amplification circuit, and a filter circuit; The first input end of the voltage divider circuit is connected to the grid-connected live wire, the second input end of the voltage divider circuit is connected to the grid-connected neutral wire, the first output end of the voltage divider circuit is connected to the first input end of the amplifier circuit, and the second output end of the voltage divider circuit is connected to the second input end of the amplifier circuit; the output end of the amplifier circuit is connected to the input end of the filter circuit, and the output end of the filter circuit is respectively connected to the first control module and the second control module.

8. The device according to claim 7, characterized in that The voltage dividing circuit comprises a first voltage dividing circuit and a second voltage dividing circuit; The first end of the first voltage divider circuit is connected to the grid live line, and the second end of the first voltage divider circuit is connected to the first input end of the amplifier circuit; the first end of the second voltage divider circuit is connected to the grid neutral line, and the second end of the second voltage divider circuit is connected to the second input end of the amplifier circuit; The first voltage-dividing circuit includes at least one first voltage-dividing resistor connected in series, and the second voltage-dividing circuit includes at least one second voltage-dividing resistor connected in series.

9. The device according to claim 7, characterized in that The amplifying circuit comprises: a third voltage source, an operational amplifier, a bias circuit and a feedback circuit, wherein the bias circuit comprises a bias resistor and a third filter capacitor, and the feedback circuit comprises a feedback resistor and a fourth filter capacitor; The non-inverting input terminal of the operational amplifier is connected to the first output terminal of the voltage divider circuit, and the inverting input terminal of the operational amplifier is connected to the second output terminal of the voltage divider circuit; The bias resistor and the third filter capacitor are connected in parallel between the third voltage source and the non-inverting input terminal of the operational amplifier; The feedback resistor and the fourth filter capacitor are connected in parallel between the inverting input terminal of the operational amplifier and the output terminal of the operational amplifier.

10. The device according to claim 7, characterized in that The filter circuit comprises: a first filter resistor, a fifth filter capacitor, a second filter resistor and a sixth filter capacitor; A first end of the first filter resistor is connected to the output end of the amplifier circuit, and a second end of the first filter resistor is connected to the first control module; The first end of the fifth filter capacitor is connected to the second end of the first filter resistor, and the second end of the fifth filter capacitor is grounded; A first end of the second filter resistor is connected to the output end of the amplifier circuit, and a second end of the second filter resistor is connected to the second control module; The first end of the sixth filter capacitor is connected to the second end of the second filter resistor, and the second end of the sixth filter capacitor is grounded.

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