Fault detection method and power equipment

Abstract

The invention provides a fault detection method applied to power equipment and the power equipment. The fault detection method comprises the following steps: firstly, controlling a live wire switch and a neutral wire switch in a grid-connected switch to be switched off, and controlling a change-over switch in an insulation detection circuit to be in a first state, so as to obtain a first switch-off voltage between a neutral wire interface and a midpoint between a first bus capacitor and a second bus capacitor; if the first disconnection voltage is smaller than a first voltage threshold value, the switching switch is controlled to be switched into a second state, then second disconnection voltage between the midpoint and the neutral line interface is obtained, and if the second disconnection voltage is smaller than the first voltage threshold value, it is determined that the neutral line switch has an adhesion fault. According to the method, the adhesion fault condition of the neutral line switch of the grid-connected switch can be accurately detected, and the use safety of power equipment is facilitated.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a fault detection method and a power device. Background Art

[0002] The inverter is connected to the grid via a relay. When the relay is closed, the AC power output by the inverter can be integrated into the AC grid. A relay failure will affect the inverter's functionality. Therefore, relay fault detection is particularly important. Related technologies typically measure the voltage difference across the relay on the neutral line when the inverter output is stopped and the relay is set to open. This voltage difference is used to directly determine whether the neutral line relay has a sticking fault. However, this fault detection method is prone to misjudgment. Summary of the Invention

[0003] In view of this, the present application provides a fault detection method and power equipment, which can accurately detect the neutral line switch adhesion fault of the grid-connected switch.

[0004] The first aspect of the present application provides a fault detection method, which is applied to power equipment. The power equipment includes an inverter circuit, a grid-connected switch and a grid-connected interface, the grid-connected switch includes a live wire switch and a neutral wire switch, and the grid-connected interface includes a live wire interface and a neutral wire interface; the DC end of the inverter circuit and the insulation detection circuit are connected in parallel between the positive DC bus and the negative DC bus, and the first bus capacitor and the second bus capacitor of the inverter circuit are connected in series between the positive DC bus and the negative DC bus; the live wire output end of the inverter circuit is connected to the live wire interface through the live wire switch, and the midpoint of the first bus capacitor and the second bus capacitor is connected to the neutral wire interface through the neutral wire switch. The live wire interface is also used to connect to the live wire of the power grid, and the neutral wire interface is also used to connect to the neutral wire of the power grid. The insulation detection circuit includes a voltage divider circuit and a switching switch, the voltage divider circuit is also connected to the ground wire, and the switching switch is used to connect or shield at least one voltage divider resistor in the voltage divider circuit. Correspondingly, the fault detection method includes: controlling the live wire switch to disconnect, controlling the neutral wire switch to disconnect, and controlling the switching switch to be in the first state; obtaining the first disconnect voltage between the midpoint and the neutral wire interface; if the first disconnect voltage is less than the first voltage threshold, controlling the switching switch to switch to the second state; obtaining the second disconnect voltage between the midpoint and the neutral wire interface; if the second disconnect voltage is less than the first voltage threshold, determining that a adhesion fault has occurred in the neutral wire switch.

[0005] It is understood that when the neutral switch is stuck, the midpoint and the neutral interface remain connected. In this case, the potential of the midpoint is substantially equal to the potential of the neutral interface, so the voltage between the midpoint and the neutral interface is very low. Therefore, in the fault detection method of the present application, the live switch is first controlled to be disconnected, the neutral switch is controlled to be disconnected, and the diverter switch is controlled to be in a first state, thereby obtaining a first disconnect voltage between the midpoint and the neutral interface, and determining the relationship between the first disconnect voltage and a first voltage threshold. If the first disconnect voltage is less than the first voltage threshold, it indicates that the first disconnect voltage is very low, indicating that the neutral switch may have a sticking fault. The diverter switch is then controlled to switch to a second state, thereby obtaining a second disconnect voltage between the midpoint and the neutral interface. If the neutral switch is stuck, switching the diverter switch state will not cause a change in the voltage between the midpoint and the neutral interface. Therefore, if the second disconnect voltage is still less than the first voltage threshold, it indicates that the voltage between the midpoint and the neutral interface is not affected by switching the diverter switch state, and it can be determined that the neutral switch has a sticking fault. Through the method of the present application, secondary detection of neutral line switch adhesion faults can be achieved, which can avoid misjudgment, improve the accuracy of neutral line switch adhesion fault detection, and be beneficial to the safe use of power equipment.

[0006] In one embodiment, the method further includes: if the first disconnect voltage and / or the second disconnect voltage is not less than a first voltage threshold, determining that no sticking fault occurs in the neutral line switch.

[0007] In one embodiment, the neutral switch comprises a first sub-neutral switch and a second sub-neutral switch connected in series. Therefore, controlling the neutral switch to open includes controlling the first sub-neutral switch to open and the second sub-neutral switch to close. Accordingly, determining that a stuck fault has occurred in the neutral switch if the second disconnect voltage is less than a first voltage threshold includes determining that a stuck fault has occurred in the first sub-neutral switch if the second disconnect voltage is less than the first voltage threshold.

[0008] In one embodiment, the method further includes: when it is determined that the neutral line switch has not had a sticking fault, controlling the live line switch to be disconnected, controlling the neutral line switch to be closed, and controlling the switching switch to be in the first state or the second state; obtaining a first conduction voltage between the midpoint and the neutral line interface; if the first conduction voltage is less than a first voltage threshold, controlling the switching switch to switch to a relative state; the first state and the second state are relative states; obtaining a second conduction voltage between the midpoint and the neutral line interface; if the second conduction voltage is less than the first voltage threshold, determining that the neutral line switch has not had an open circuit fault.

[0009] In one embodiment, after controlling the live switch to be open, the neutral switch to be closed, and the transfer switch to be in the first state or the second state, the method further includes: obtaining a first ground voltage between the midpoint and the ground line. Furthermore, after controlling the transfer switch to be switched to the opposite state, the method further includes: obtaining a second ground voltage between the midpoint and the ground line; if the voltage difference between the first ground voltage and the second ground voltage is greater than a second voltage threshold, determining that a wiring fault has occurred in at least one of the neutral line and the ground line; and if the voltage difference between the first ground voltage and the second ground voltage is not greater than the second voltage threshold, determining that no wiring fault has occurred in the neutral line and the ground line.

[0010] In one embodiment, the fault detection method further includes: controlling the live wire switch to disconnect and controlling the neutral wire switch to close; obtaining a third disconnect voltage between the live wire output end and the live wire interface; if the third disconnect voltage is less than a third voltage threshold, determining that a sticking fault has occurred in the live wire switch; if the third disconnect voltage is not less than the third voltage threshold, determining that no sticking fault has occurred in the live wire switch.

[0011] In one embodiment, the live switch comprises a first sub-live switch and a second sub-live switch connected in series. Therefore, controlling the live switch to open includes controlling the first sub-live switch to open and controlling the second sub-live switch to close. Accordingly, determining whether a sticking fault has occurred in the live switch if the third disconnect voltage is not less than a third voltage threshold includes determining whether a sticking fault has occurred in the first sub-live switch if the third disconnect voltage is not less than the third voltage threshold.

[0012] In one embodiment, after determining that the live wire switch has no adhesion fault, the method further includes: controlling the live wire switch and the neutral wire switch to be closed; after the live wire switch and the neutral wire switch are closed, controlling the inverter circuit to be grid-connected and operated.

[0013] In one embodiment, the method further includes: when any type of fault is detected, outputting corresponding type of fault prompt information.

[0014] The second aspect of the present application provides a power device, including an inverter circuit, a grid-connected switch, a grid-connected interface and a controller, the grid-connected switch including a live wire switch and a neutral wire switch, and the grid-connected interface including a live wire interface and a neutral wire interface; the DC end of the inverter circuit and the insulation detection circuit are connected in parallel between the positive DC bus and the negative DC bus, and the first bus capacitor and the second bus capacitor of the inverter circuit are connected in series between the positive DC bus and the negative DC bus; the live wire output end of the inverter circuit is connected to the live wire interface through the live wire switch, and the midpoint of the first bus capacitor and the second bus capacitor is connected to the neutral wire interface through the neutral wire switch, the live wire interface is also used to connect to the live wire of the power grid, and the neutral wire interface is also used to connect to the neutral wire of the power grid; the insulation detection circuit includes a voltage divider circuit and a switching switch, the voltage divider circuit is also connected to the ground wire, and the switching switch is used to connect or shield at least one voltage divider resistor in the voltage divider circuit; the controller is used to execute the fault detection method described in the above-mentioned first aspect or any one of the embodiments of the first aspect.

[0015] The third aspect of the present application provides an electronic device, including a processor and a memory, the memory being used to store programs, instructions or codes, and the processor being used to execute the programs, instructions or codes in the memory to complete the fault detection method described in the first aspect or any one of the embodiments of the first aspect.

[0016] The fourth aspect of the present application provides a fault detection device, including a first control module, a first acquisition module, a second control module, a second acquisition module and a fault judgment module, the first control module is used to control the disconnection of the live wire switch, the disconnection of the neutral wire switch, and the control of the switching switch to be in a first state; the first acquisition module is used to obtain a first disconnection voltage between the midpoint and the neutral wire interface; the second control module is used to control the switching switch to switch to a second state when the first disconnection voltage is less than a first voltage threshold; the second acquisition module is used to obtain a second disconnection voltage between the midpoint and the neutral wire interface; the fault judgment module is used to determine that a neutral wire switch has a adhesion fault when the second disconnection voltage is less than the first voltage threshold.

[0017] A fifth aspect of the present application provides a computer-readable storage medium storing a computer program, which is loaded by a processor to execute the fault detection method described in the first aspect or any one of the embodiments of the first aspect.

[0018] In addition, the technical effects brought about by any possible implementation method in the second to fifth aspects can refer to the technical effects brought about by different embodiments in the first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is an application scenario diagram of the power device provided in one embodiment of the present application.

[0020] Figure 2This is a circuit diagram of a power device and an insulation detection circuit provided in one embodiment of the present application.

[0021] Figure 3 This is a flow chart of a fault detection method provided in one embodiment of the present application.

[0022] Figure 4 yes Figure 2 The figure shows a control signal waveform diagram of a power device when adopting the fault detection method provided in an embodiment of the present application.

[0023] Figure 5 This is another flow chart of a fault detection method provided in one embodiment of the present application.

[0024] Figure 6 This is another flow chart of a fault detection method provided in an embodiment of the present application.

[0025] Figure 7 This is a schematic diagram of an electronic device provided by an embodiment of the present application.

[0026] Figure 8 This is a schematic diagram of a fault detection device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0027] It should be noted that the terms "first" and "second" in the description, claims and drawings of this application are used to distinguish similar objects, rather than to describe a specific order or sequence.

[0028] It should also be noted that the method disclosed in the embodiments of the present application or the method shown in the flowchart includes one or more steps for implementing the method. Without departing from the scope of the claims, the execution order of multiple steps can be interchanged with each other, and some steps can also be deleted.

[0029] The following will describe some embodiments with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features therein may be combined with each other.

[0030] The inverter needs to be connected to the grid through a relay. When the relay is closed, the AC power output by the inverter can be incorporated into the AC grid. If the relay fails, it will affect the function of the inverter. Therefore, fault detection of the relay is particularly important. In related technologies, the voltage difference between the two ends of the relay on the neutral line is usually measured when the inverter stops output and the relay is set to be disconnected, and the magnitude of the voltage difference is directly used to determine whether the neutral line relay has a sticking fault. However, because the voltage of the neutral line relative to the ground line will change with the different wiring conditions between the inverter and the grid, the voltage difference will change. Therefore, this fault detection method is prone to misjudgment.

[0031] Therefore, the embodiments of the present application provide a fault detection method and a power device, which can accurately detect the neutral line switch adhesion fault of the grid-connected switch.

[0032] The technical solution of this application is further described below with reference to the accompanying drawings.

[0033] See also Figure 1 , shows an application scenario diagram of the power device provided in an embodiment of the present application. Figure 1 It should be understood that the application scenarios of the power device in the embodiment of the present application are not limited to this, and can also be applied to household energy storage power products, etc.

[0034] like Figure 1 As shown, the scenario includes a photovoltaic power generation device 100, an energy storage device 200, a power device 300, and a grid 400. The power device 300 includes an inverter circuit 10, a grid-connected switch 20, a grid-connected interface 30, a positive DC bus BUS+, a negative DC bus BUS-, and a controller 40.

[0035] The output end of the photovoltaic power generation device 100, the positive and negative poles of the energy storage device 200, and the DC end of the inverter circuit 10 are all connected between the positive DC bus BUS+ and the negative DC bus BUS-. The photovoltaic power generation device 100 includes photovoltaic modules that can be used to transmit DC power to the positive DC bus BUS+ and the negative DC bus BUS-. The energy storage device 200 includes an energy storage battery that can be used to transmit DC power to the positive DC bus BUS+ and the negative DC bus BUS-, and / or to obtain DC power from the positive DC bus BUS+ and the negative DC bus BUS- for charging. In other embodiments, the energy storage device 100 can also be connected to a different DC bus from the photovoltaic power generation device 100. For example, the inverter circuit includes buses of different voltages, and the photovoltaic power generation device 100 and the energy storage device can be connected to buses of different voltages respectively; a DC / DC conversion circuit is provided between the buses of different voltages.

[0036] The inverter circuit 10 is further provided with a first bus capacitor 50 and a second bus capacitor 60 at the DC end. Specifically, the first bus capacitor 50 and the second bus capacitor 60 of the inverter circuit 10 are connected in series between the positive DC bus BUS+ and the negative DC bus BUS-. The midpoint BUSN between the first bus capacitor 50 and the second bus capacitor 60 serves as a reference point for the power device 300. The connection end extending from the midpoint BUSN serves as the neutral line output terminal INVN of the inverter circuit 10. The hot line output terminal INVL and the neutral line output terminal INVN of the inverter circuit 10 are connected to the grid interface 30 via the grid-connected switch 20. The grid interface 30 is also used to connect to the power grid 400.

[0037] The power grid 400 has a live line GL and a neutral line GN. Figure 2 As shown, the grid-connected switch 20 includes a live line switch and a neutral line switch, and the grid-connected interface 30 includes a live line interface and a neutral line interface.

[0038] The hot line output terminal INVL of the inverter circuit 10 is connected to the hot line interface via a hot line switch. The hot line interface is used to access the hot line GL of the power grid 400. The midpoint BUSN can be connected to the neutral line interface via a neutral line switch. The neutral line interface is used to access the neutral line GN of the power grid 400. In some embodiments, the neutral line GN is connected to the ground line PE.

[0039] It is understood that when the live switch is closed, the live output terminal INVL of the inverter circuit 10 can be electrically connected to the live line GL of the grid 400. When the neutral switch is closed, the neutral output terminal INVN of the inverter circuit 10 can be electrically connected to the neutral line GN of the grid 400.

[0040] In the embodiment of the present application, the power device 300 may be a single-phase two-wire inverter device, wherein the inverter circuit 10 corresponds to a single-phase inverter circuit and has one live wire output terminal. Alternatively, the power device 300 may be a two-phase three-wire inverter device, wherein the inverter circuit 10 corresponds to a two-phase inverter circuit and has two live wire output terminals. Alternatively, the power device 300 may be a three-phase four-wire inverter device, wherein the inverter circuit 10 corresponds to a three-phase inverter circuit and has three live wire output terminals.

[0041] It should be understood that single-phase two-wire inverter equipment, two-phase three-wire inverter equipment and three-phase four-wire inverter equipment all need to be connected to the neutral line interface with the neutral line GN, and the neutral line is connected to the ground line PE before they can be put into use.

[0042] In some scenarios, when the neutral line interface is connected to the neutral line GN and the neutral line is connected to the ground line PE, the two-phase inverter circuit and the three-phase inverter circuit can also be used as a single-phase inverter circuit.

[0043] In the embodiment of the present application, the topology of the inverter circuit 10 can be selected according to actual conditions, for example, it can be a Heric (Highly Efficient Reliable Inverter Concept) topology, a two-level topology, a three-level I-type topology or a three-level T-type topology, etc., without any special limitation here.

[0044] The power grid 400 can be a single-phase power grid, a two-phase power grid, or a three-phase power grid. A single-phase power grid has one live wire, a two-phase power grid has two live wires, and a three-phase power grid has three live wires. The number of live wires in the power grid 400 is not less than the live wire output end of the inverter circuit 10.

[0045] The grid-connected switch 20 may include one or more live switches, wherein both the live switch and the neutral switch may use corresponding types of switch elements according to actual conditions, such as relays or contactors, etc., which are not limited here.

[0046] In some embodiments, each live switch may be composed of multiple live sub-switches connected in series, and each neutral switch may be composed of multiple neutral sub-switches connected in series, to prevent failure of the circuit breaker function due to adhesion failure of a single switch.

[0047] The grid-connected interface 30 may include one or more live wire interfaces. Each live wire output terminal corresponds to a live wire interface, one or a group of live wire switches, and one phase live wire.

[0048] For better understanding, the following Figure 2 The power device 300 is shown for exemplary purposes.

[0049] Specifically, if Figure 2 As shown, taking the inverter circuit 10 as a three-phase two-level inverter circuit as an example, the inverter circuit 10 includes three bridge arms and an output filter circuit. Each bridge arm includes two switching tubes connected in series (i.e., Q11 and Q12 are a bridge arm, Q21 and Q22 are a bridge arm, and Q32 and Q32 are a bridge arm). The device type of each switching tube can be selected according to actual needs, for example, it can be an IGBT. It should be understood that in other embodiments, the above-mentioned switching tubes can also use MOSFET or other semiconductor switches according to actual conditions. The two switching tubes in the same bridge arm are complementary. Both ends of the three inverter bridge arms serve as DC ends, and are connected in series with the first bus capacitor 50 (corresponding to Figure 2 The capacitor C1 in the second bus capacitor 60 (corresponding to Figure 2 The capacitor C2 in the inverter bridge is connected in parallel between the positive DC bus BUS+ and the negative DC bus BUS-. The connection terminals extending from the midpoints of the three inverter bridge arms can serve as the three live wire output terminals INVL1, INV L2, and INVL3.

[0050] The live wire output terminals INVL1, INV L2, and INVL3 are connected to the grid-connected switch 20 via an output filter circuit. The structure of the output filter circuit is not limited. For the convenience of description, Figure 2 In the example, a three-phase T-type filter circuit consisting of filter inductors Lf1 to Lf6 and filter capacitors Cf1 to Cf3 is used to demonstrate the output filter circuit.

[0051] Assume that the power grid 400 is a three-phase power grid having a live line GL1 , a live line GL2 , a live line GL3 and a neutral line GN.

[0052] The grid-connected switch 20 has three sets of live switches and one set of neutral switches. The first set of live switches consists of a first sub-live switch K11 and a second sub-live switch K12 connected in series. The second set of live switches consists of a first sub-live switch K21 and a second sub-live switch K22 connected in series. The third set of live switches consists of a first sub-live switch K31 and a second sub-live switch K32 connected in series. The neutral switch set consists of a first sub-neutral switch K41 and a second sub-neutral switch K42 connected in series.

[0053] The grid-connected interface 30 has three live wire interfaces and one neutral wire interface.

[0054] Furthermore, the live line output terminal INVL1 of the inverter circuit 10 can be connected to the live line GL1 of the power grid 400 via the live line sub-switches K11 and K12 and a corresponding live line interface. The live line output terminal INVL2 of the inverter circuit 10 can be connected to the live line GL2 of the power grid 400 via the live line sub-switches K21 and K22 and a corresponding live line interface. The live line output terminal INVL3 of the inverter circuit 10 can be connected to the live line GL3 of the power grid 400 via the live line sub-switches K31 and K32 and a corresponding live line interface. The midpoint BUSN can be connected to the neutral line GN of the power grid 400 via the neutral line output terminal INVN, the neutral line sub-switches K41 and K42, and a corresponding neutral line interface. When the neutral line GN is connected to the ground line PE and the neutral line sub-switches K41 and K42 are closed, the neutral line output terminal INVN is connected to the ground line.

[0055] Based on this, the inverter circuit 10 can use three inverter bridge arms to achieve a three-phase inverter function.

[0056] In some scenarios, when the neutral line interface is connected to the neutral line GN and the neutral line GN is connected to the ground line PE, the inverter circuit 10 can also use one of the three inverter bridge arms to achieve a single-phase inverter function.

[0057] In the embodiment of the present application, the controller 40 may be a microcontroller unit (MCU) or other control circuit. In other embodiments, the controller 40 may also be independently configured or integrated into other devices in the scene.

[0058] The controller 40 is connected to the switching tube, live wire switch and neutral wire switch in the inverter circuit 10, and is used to control the on and off of the switching tube, live wire switch and neutral wire switch to control the working condition of the inverter circuit 10 and the connectivity between the inverter circuit 10 and the power grid 400.

[0059] The controller 40 can send corresponding control signals to the switching tubes, live switch, and neutral switch in the inverter circuit 10 to control the on / off states of the switching tubes, live switch, and neutral switch. The control signals can be level signals or other types of electrical signals.

[0060] In addition, the power device 300 may further include a load interface (not shown in the figure), and the live wire output end of the inverter circuit 10 may also be used to connect to an electrical load (not shown in the figure) through the load interface. The electrical load may be, for example, various household AC loads.

[0061] exist Figure 1 In the illustrated scenario, the photovoltaic power generation device 100 and / or the energy storage device 200 can be used to output DC power to the inverter circuit 10 in the power device 300 via the positive and negative DC busbars. Under the control of the controller 40, the inverter circuit 10 can be used to convert the DC power into AC power for output to the load and / or feed into the power grid. Furthermore, the controller 40 can control the inverter circuit 10 to operate in a grid-connected or off-grid state based on actual conditions.

[0062] In actual application scenarios, if the inverter circuit 10 has the function of grid-connected operation, the power device 300 should have insulation impedance protection and grid-connected switch 20 fault detection functions.

[0063] It is understood that the insulation resistance represents the insulation quality between the DC terminal of the inverter circuit 10 and the ground. When the insulation resistance is less than a preset impedance threshold, it indicates that the insulation between the DC terminal of the inverter circuit 10 and the ground has failed. In this case, the inverter circuit 10 may short-circuit and fail, posing a safety risk.

[0064] In some embodiments, as Figure 1 As shown, the power device 300 further includes an insulation detection circuit 500. The insulation detection circuit 500 is connected in parallel between the positive DC bus and the negative DC bus and can be used to detect the insulation impedance of the DC end of the inverter circuit 10 relative to the ground line PE, that is, to detect the insulation impedance of the positive and negative DC buses relative to the ground line PE.

[0065] For example, the controller 40 may detect the insulation impedance between the DC terminal of the inverter circuit 10 and the ground by an unbalanced bridge method based on the insulation detection circuit 500 .

[0066] Specifically, the insulation detection circuit 500 may include a voltage divider circuit and a switching switch. The voltage divider circuit is connected between the positive DC bus and the negative DC bus, and the voltage divider circuit is also connected to the ground line PE. The voltage divider circuit may include multiple voltage divider resistors connected in series or in series-parallel. The switching switch is connected in parallel or in series with at least one voltage divider resistor and can be used to access or shield at least one voltage divider resistor in the voltage divider circuit. It should be understood that the specific structure and connection relationship of the voltage divider circuit and the switching switch, the resistance value of the voltage divider resistor, and the device type of the switching switch can be set accordingly according to actual conditions and are not limited here.

[0067] The switch is also connected to the controller 40. Therefore, by turning the switch on and off, the controller 40 can change the equivalent impedance of the voltage divider circuit, thereby changing the voltage divider state of the voltage divider circuit and causing the voltage of the voltage divider resistor to change. This also shows that switching the switch state can actually cause a voltage disturbance.

[0068] Furthermore, the controller 40 can use the Thevenin theorem to establish a related set of equations based on the voltage dividing state of the bus voltage Vbus between the positive and negative DC buses by the voltage dividing circuit when the switching switch is opened and closed, and then solve the set of simultaneous equations to obtain the size of the insulation resistance RX / / RY of the DC end of the inverter circuit 10 to the ground.

[0069] For better understanding, the following Figure 2 The insulation detection circuit 500 is shown for exemplary purposes.

[0070] Specifically, if Figure 2 As shown, insulation detection circuit 500 includes voltage divider resistors R1, R2, and R3, and a switch S1. These resistors R1, R2, and R3 form a voltage divider circuit. Resistors R1 and R2 are connected in series between BUS+ and ground PE, while resistor R2 is connected in parallel with switch S1. Resistors R3 are connected between BUS- and ground PE.

[0071] RX represents the insulation resistance of the positive DC bus relative to the ground PE, and RY represents the insulation resistance of the negative DC bus relative to the ground PE. The insulation resistance of the DC terminal of the inverter circuit 10 to ground is RX / / RY, where “ / / ” represents a parallel symbol.

[0072] exist Figure 2 In the insulation detection circuit 500 shown, when the controller 40 controls the switch S1 to open, the voltage divider resistor R2 can be connected between BUS+ and PE. At this time, the equivalent impedance between BUS+ and PE is equal to (R1+R2) / / RX, and the equivalent impedance between BUS- and PE is equal to R3 / / RY.

[0073] When the switch S1 is turned on, the voltage dividing state of the bus voltage Vbus by the voltage dividing resistor R3 can be expressed as follows:

[0074]

[0075] When the controller 40 controls the switch S1 to be closed, the voltage divider resistor R2 is short-circuited and shielded by the switch S1. At this time, the equivalent impedance between BUS+ and PE is equal to R1 / / RX, and the equivalent impedance between BUS- and PE is equal to R3 / / RY.

[0076] When the switch S1 is closed, the voltage dividing state of the bus voltage Vbus by the voltage dividing resistor R3 can be expressed as follows:

[0077]

[0078] It can be seen that formula (1) and formula (2) are different, which means that switching the switch state can cause V R3 Changes have occurred.

[0079] Then, the controller 40 can switch the switch S1 to open or close the V R3 , the actual resistance values of R1, R2, and R3, and the simultaneous solution of equations (1) and (2) to obtain the insulation resistance RX / / RY of the DC terminal of the inverter circuit 10 to ground.

[0080] In practical applications, before the inverter circuit 10 is connected to the grid, the controller 40 may first detect the insulation impedance between the DC terminal of the inverter circuit 10 and the ground through the insulation detection circuit 500 to determine whether the insulation impedance reaches a preset impedance threshold.

[0081] If the insulation impedance reaches a preset impedance threshold, then when the power grid 400 is operating normally and the inverter circuit 10 stops working, the controller 40 can execute the fault detection method provided in the embodiment of the present application to detect the fault condition of the grid-connected switch 20. If the grid-connected switch 20 is not faulty, the grid-connected switch 20 can be controlled to close to electrically connect the inverter circuit 10 to the power grid 400, and the inverter circuit 10 can then be safely connected to the grid for operation.

[0082] During normal operation of power grid 400, the voltage of power grid 400 is within the normal voltage range of 0.8Un to 1.1Un. Un is the rated voltage of power grid 400, for example, 130V, 230V, or other voltage values. It should be understood that the rated voltages of power grids 400 of different voltage levels may vary accordingly. If the voltage of power grid 400 exceeds the normal voltage range, it indicates that the voltage of power grid 400 has deviated from the normal voltage range and an abnormality exists in power grid 400.

[0083] If the insulation impedance does not reach the preset impedance threshold or the grid 400 is abnormal, the controller 40 can control the grid-connected switch 20 to open so that the inverter circuit 10 cannot be electrically connected to the grid 400, and the inverter circuit 10 then operates off-grid.

[0084] Next, the fault detection method provided in the embodiment of the present application is described in detail.

[0085] Figure 3 A flowchart of a fault detection method provided in an embodiment of the present application. Figure 4 This is a control signal waveform diagram of the power device 300 when using the fault detection method provided by the embodiment of the present application, where the horizontal axis represents time, the vertical axis represents the switch, and the waveform represents the control signal. For ease of description, Figure 4 In the example, the control switch is closed when the control signal is at a high level, and is opened when the control signal is at a low level.

[0086] Please also refer to Figure 3 and Figure 4 , the fault detection method includes the following steps:

[0087] Step S101: Control the live wire switch to be disconnected, control the neutral wire switch to be disconnected, and control the transfer switch to be in the first state.

[0088] by Figure 2 Taking the circuit shown as an example, the controller 40 can control the three groups of live switches (i.e., switches K11, K12, K21, K22, K31, and K32) in the grid-connected switch 20 to be disconnected, and control the partial or complete disconnection of a group of neutral switches (i.e., K41 and K42). Furthermore, the open or closed state can be defined as the first state, and the switch S1 can be controlled to be in the first state.

[0089] Step S102: Acquire a first disconnection voltage between the midpoint and the neutral line interface.

[0090] by Figure 2 Taking the circuit shown as an example, the voltage between the midpoint BUSN and the neutral interface is also the voltage between the neutral output terminal INV and the neutral interface. Because the neutral output terminal INVN and the neutral interface are connected via a set of neutral switches (i.e., switches K41 and K42), the voltage between the midpoint BUSN and the neutral interface is also the voltage across the set of neutral switches.

[0091] In other examples, the neutral line output terminal INVN and the neutral line interface are connected via a neutral line switch, and the voltage between the midpoint BUSN and the neutral line interface is the voltage across the neutral line switch.

[0092] Therefore, in step S102, when the controller 40 controls the neutral switch to be disconnected, the controller 40 may sample the voltage between the neutral output terminal INV and the neutral interface, or sample the voltage across the neutral switch / neutral switch group, using a voltage sampling device or a voltage sampling circuit, to obtain a first disconnection voltage between the midpoint BUSN and the neutral interface. The voltage sampling device or the voltage sampling circuit may be independently provided or integrated within the controller 40, and is not specifically limited herein.

[0093] Alternatively, the controller 40 may wait for a preset time period before acquiring the first disconnection voltage when controlling the neutral switch to disconnect. The preset time period allows time for the neutral switch to switch to the disconnected state, ensuring that the neutral switch is disconnected at the time of sampling. This reduces voltage sampling errors and improves fault detection accuracy. The preset time period can be set according to actual needs, for example, 50ms, 100ms, 200ms, etc.

[0094] Step S103: Determine whether the first disconnection voltage is less than a first voltage threshold.

[0095] If the neutral switch is closed or stuck, the neutral switch can be regarded as a section of wire. The potential of any two points on the wire is equal, and the voltage is zero or nearly zero. That is, the voltage V between the midpoint BUSN and the neutral interface is BUSN_GN Zero or nearly zero (for example, a few tenths of a volt).

[0096] Therefore, in the embodiment of the present application, a first voltage threshold may be set. The value of the first voltage threshold is close to 0 and may be set accordingly according to actual conditions, for example, may be set to 0.5V.

[0097] When the first disconnection voltage is not less than the first voltage threshold, it indicates that the neutral line switch is disconnected, and there is a certain voltage difference across the neutral line switch.

[0098] When the first disconnection voltage is less than the first voltage threshold, it indicates that the voltage difference across the neutral line switch is small, and the neutral line switch may be stuck.

[0099] It can be understood that if the neutral line switch is closed or stuck, the midpoint BUSN of the inverter circuit 10 is connected to the neutral line GN of the grid 400. Since the neutral line GN of the grid 400 is connected to the ground line PE, Figure 2 As shown by the arrowed line, the ground line PE, the voltage dividing resistor R3, the negative DC bus BUS-, the second bus capacitor C2, the midpoint BUSN, the neutral output terminal INVN, the neutral switch, the neutral interface and the neutral line GN can be connected to form a loop.

[0100] At this time, according to Kirchhoff's voltage law:

[0101] V BUSN_GN =-V GN_PE -V R3 +V BUS - (3)

[0102] Among them, V BUSN_GN Refers to the voltage between the midpoint BUSN and the neutral line interface. When the neutral line interface is connected to the neutral line GN, V BUSN_GN That is, it refers to the voltage between the midpoint BUSN and the neutral line GN, or the voltage between the neutral line output terminal INVN and the neutral line GN. GN_PE Refers to the voltage between the neutral line GN and the ground line PE.

[0103] When the neutral switch is closed or stuck, V BUSN_GN is zero or nearly zero (for example, a few tenths of a volt). Moreover, the neutral line GN is connected to the near end of the ground line PE, so V GN_PE is zero or nearly zero (e.g., a few tenths of a volt). Therefore, when the neutral switch is closed or stuck, the voltage V across the voltage divider resistor R3 R3 Clamped to the voltage V of the second bus capacitor BUS- , that is, V R3 =V BUS- .

[0104] In contrast, in V R3＝ V BUS- In this case, it will also cause V BUSN_GN Equal to V GN_PE At this time, due to V GN_PE is zero or nearly zero, so V BUSN_GN is also zero or nearly zero, which can satisfy the condition that the first disconnection voltage is less than the first voltage threshold.

[0105] Therefore, when the first disconnection voltage is not less than the first voltage threshold, it indicates that the neutral line switch is disconnected and the neutral line switch is not stuck.

[0106] However, when the first disconnect voltage is less than the first voltage threshold, it is possible that the neutral line switch is stuck, resulting in V BUSN_GN Zero or nearly zero; or, it may be V R3＝ V BUS- situation, which in this case will also cause V BUSN_GN Zero or nearly zero.

[0107] Or, when there is a wiring fault in the neutral line GN and / or the ground line PE, V GN_PE The value of V GN_PE =V BUS--V R3 situation, which in turn leads to V BUSN_GN =-V GN_PE -V R3 +V BUS- =0.

[0108] Based on this, in step S103, by comparing the first disconnection voltage with the first voltage threshold, it is possible to preliminarily determine whether the neutral line switch has the possibility of sticking. Thereafter, a secondary determination can be performed through steps S104-S107.

[0109] Step S104: If the first disconnection voltage is less than the first voltage threshold, control the switch to switch to the second state.

[0110] In step S104, when the first disconnect voltage is less than the first voltage threshold, the controller 40 may further control the switch S1 to switch to the second state. The second state is a state opposite to the first state, for example, the first state is a closed state and the second state is an open state (also referred to as a disconnected state), or the first state is an open state and the second state is a closed state.

[0111] Step S105: Acquire a second disconnection voltage between the midpoint and the neutral line interface.

[0112] In step S105, the controller 40 may obtain a second disconnection voltage between the midpoint BUSN and the neutral line interface by sampling through a voltage sampling device or a voltage sampling circuit. Detailed descriptions of step S102 may be referred to and will not be repeated here.

[0113] Step S106: Determine whether the second disconnection voltage is less than the first voltage threshold.

[0114] It can be understood that if the neutral line switch is not stuck, the voltage V R3 If the voltage is not clamped, then the voltage divider state of the voltage divider circuit will be changed after the switch is switched to the second state, thereby causing V R3 The change of V is the voltage change between BUS- and ground PE. BUSN_GN =-V GN_PE -V R3 +V BUS -, in V GN_PE and V BUS- If no change occurs, V R3 The change will cause the voltage V between the midpoint BUSN and the neutral line interface BUSN_GN is no longer less than the first voltage threshold.

[0115] On the contrary, if the neutral switch sticks, V R3 is clamped, V R3There will be no change. Moreover, since the neutral switch is stuck, the neutral switch can be regarded as a conductor, so V BUSN_GN It will still be less than the first voltage threshold.

[0116] For example, assuming that the resistance of the voltage divider resistor R1 is 236 Kohm (kilo ohms), the resistance of the voltage divider resistor R2 is 6190 Kohm, the resistance of the voltage divider resistor R3 is 5170 Kohm, Rx is 2000 Kohm, RY is 2000 Kohm, Vbus is 500V, and the first voltage threshold is 0.5V.

[0117] The voltage V across the voltage divider resistor R3 R3 In the case of not being clamped, according to the above formulas (1) and (2), it can be calculated that when the switch S1 is opened, V R3 =243V; when the switch S1 is closed, V R3 =436V. If the neutral line GN and the ground line PE of the power grid 400 are not connected, and when the switch S1 is turned on, V BUSN_GN =-V GN_PE -V R3 +V BUS- <0.5V, then after the switch S1 is closed, V R3 From 243V to 436V, if the neutral switch is not sticky, then V BUSN_GN =-V GN_PE -V R3 +V BUS- >0.5V.

[0118] It can be seen that when the neutral line switch is not stuck, V R3 The change will cause the voltage V between the midpoint and the neutral line interface BUSN_GN The change makes V BUSN_GN The relationship between the voltage and the first voltage threshold changes. In the case of neutral line switch sticking, V BUSN_GN The magnitude relationship with the first voltage threshold does not change.

[0119] Therefore, in step S106, by comparing the second disconnection voltage with the first voltage threshold, it is possible to determine again whether the neutral line switch is stuck based on the change in the magnitude of the second disconnection voltage.

[0120] Step S107: If the second disconnection voltage is less than the first voltage threshold, it is determined that a neutral line switch has a sticking fault.

[0121] That is, when the second disconnect voltage is less than the first voltage threshold, it means that V BUSN_GN Unaffected by the state of the switch, the voltage V between the midpoint and the neutral line interface BUSN_GNThe magnitude relationship to the first voltage threshold value remains unchanged, so it can be determined that the neutral switch is stuck.

[0122] In general, in the fault detection method of the embodiment of the present application, the live wire switch and the neutral wire switch in the grid-connected switch 20 are first controlled to be disconnected, and the switching switch in the insulation detection circuit 500 is controlled to be in the first state, and then the first disconnection voltage between the midpoint BUSN and the neutral line interface is obtained. If the first disconnection voltage is less than the first voltage threshold, it means that the neutral line switch may have a adhesion fault, resulting in the first disconnection voltage between the midpoint BUSN and the neutral line interface being very small.

[0123] Therefore, by controlling the switching switch to switch to the second state, a second disconnect voltage between the midpoint and the neutral interface is obtained. Since, when the neutral switch is disconnected, controlling the switching switch to switch state can actively change the voltage divider state of the voltage divider circuit in the insulation detection circuit 500, causing a change in the voltage between the midpoint BUSN and the neutral interface. If the neutral switch is stuck, then switching the switching switch state will not cause a change in the voltage between the midpoint BUSN and the neutral interface. Therefore, if the second disconnect voltage is still less than the first voltage threshold, it indicates that switching the switching switch state has not affected the voltage between the midpoint BUSN and the neutral interface, and it can be determined that the neutral switch has a stuck fault.

[0124] The fault detection method of the embodiment of the present application can achieve secondary detection of neutral line switch sticking faults, thereby avoiding misjudgments, improving the accuracy of neutral line switch sticking fault detection, and facilitating safe use of the power device 300. Furthermore, by detecting neutral line switch sticking faults, it is also beneficial to ensure that the inverter circuit 10 can normally perform power conversion functions.

[0125] It is understandable that in step S103, the first disconnection voltage may not be less than the first voltage threshold. In step S106, the second disconnection voltage may not be less than the first voltage threshold.

[0126] Therefore, please refer again to Figure 3 , the fault detection method may further include:

[0127] Step S108: If the first disconnection voltage and / or the second disconnection voltage is not less than the first voltage threshold, it is determined that no adhesion fault occurs in the neutral line switch.

[0128] It can be understood that since the neutral line switch is equivalent to a wire in the case of adhesion, the voltage V between the midpoint BUSN and the neutral line interface will be BUSN_GNTherefore, when either the first disconnection voltage or the second disconnection voltage is not less than the first voltage threshold, it can be determined that the neutral line switch has not suffered a sticking fault.

[0129] It can be seen that the fault detection method of the embodiment of the present application can accurately diagnose whether a neutral line switch has a adhesion fault or not.

[0130] In some embodiments, the neutral switch is a switch group, and a group of neutral switches may be composed of multiple sub-neutral switches connected in series. Therefore, in practical applications, steps S101 to S108 may be performed for each sub-neutral switch to detect a sticking fault condition of the sub-neutral switch.

[0131] by Figure 2 The circuit shown is an example. Figure 4 For the first sub-neutral line switch K41, the above steps S101 to S108 can be performed to detect the adhesion fault of the first sub-neutral line switch K41, wherein:

[0132] In step S101 , the process of controlling the neutral line switch to be opened may include: controlling the first sub-neutral line switch to be opened and controlling the second sub-neutral line switch to be closed.

[0133] When the live switch is a switch group, and one live switch group includes multiple sub-live switches, the process of controlling the live switch to disconnect can include controlling all sub-live switches to disconnect. This can prevent a situation where a single sub-live switch in the same live switch group becomes stuck due to the control of disconnecting the sub-live switch, preventing the entire live switch group from disconnecting.

[0134] Accordingly, the process in step S107 may include: if the second disconnection voltage is less than the first voltage threshold, determining that a sticking fault occurs in the first sub-neutral line switch.

[0135] The process in step S108 may include: if the first disconnection voltage and / or the second disconnection voltage is not less than the first voltage threshold, determining that no sticking fault occurs in the first sub-neutral line switch.

[0136] For the second sub-neutral line switch K42, the above steps S101 to S108 may be performed again to detect the adhesion fault of the second sub-neutral line switch K42, wherein:

[0137] In step S101 , the process of controlling the neutral line switch to be disconnected may include: controlling the first sub-neutral line switch to be closed and controlling the second sub-neutral line switch to be disconnected.

[0138] Accordingly, the process in step S107 may include: if the second disconnection voltage is less than the first voltage threshold, determining that a sticking fault occurs in the second sub-neutral line switch.

[0139] The process in step S108 may include: if the first disconnection voltage and / or the second disconnection voltage is not less than the first voltage threshold, determining that no sticking fault occurs in the second sub-neutral line switch.

[0140] It can be seen that the methods for detecting whether the first sub-neutral switch is stuck and detecting whether the second sub-neutral switch is stuck are essentially the same. Both methods involve disconnecting the sub-neutral switch to be detected and closing the other sub-neutral switches to perform a sticking test on the sub-neutral switch to be detected. Moreover, which sub-neutral switch is used as the first sub-neutral switch can be defined by the user. Therefore, in actual applications, if the neutral switch contains multiple sub-neutral switches, each sub-neutral switch can be defined as the first sub-neutral switch in turn. By executing multiple fault detection methods to detect whether different sub-neutral switches are stuck, the sticking fault conditions of each neutral sub-switches in the neutral switch can be comprehensively and accurately detected, which is conducive to improving fault detection accuracy and power safety.

[0141] Since the neutral line switch may have an open circuit fault in addition to a sticking fault, in order to more comprehensively detect the fault condition of the neutral line switch, when it is determined that the neutral line switch has not suffered a sticking fault (i.e., after step S108), or before performing a sticking fault detection on the neutral line switch, the fault detection method of the embodiment of the present application may also detect the open circuit fault condition of the neutral line switch.

[0142] Specifically, see Figure 4 and Figure 5 , the fault detection method may further include:

[0143] Step S109: When it is determined that the neutral line switch does not have a sticking fault, the live line switch is controlled to be opened, the neutral line switch is controlled to be closed, and the transfer switch is controlled to be in the first state or the second state.

[0144] by Figure 2 Taking the circuit shown as an example, the controller 40 can control the neutral line switch in the grid-connected switch 20 to be closed, control the live line switches to be open, and control the switch S1 to be in an open state or a closed state.

[0145] Among them, the process of controlling the neutral line switch to be closed may include: controlling the first sub-neutral line switch K41 and the second sub-neutral line switch K42 to be closed, and controlling the live line switches to be disconnected, specifically controlling the first sub-live line switches K11, K21, K31 and the second sub-live line switches K12, K22, K32 to be disconnected.

[0146] When the live switch is a switch group, and one live switch group includes multiple sub-live switches, the process of controlling the live switch to disconnect can include controlling all sub-live switches in the same live switch group to disconnect. This can avoid the situation where a single sub-live switch in the same live switch group is controlled to disconnect and the sub-live switch becomes stuck, preventing the entire live switch group from disconnecting.

[0147] Step S110A: Acquire a first conduction voltage between the midpoint and the neutral line interface.

[0148] In step S110A, the controller 40 may control the neutral switch to be closed, wait for a preset period of time, and then sample the first conduction voltage between the midpoint BUSN and the neutral interface using a voltage sampling device or a voltage sampling circuit. This ensures that the neutral switch has completed its corresponding operation at the time of sampling, thereby reducing voltage sampling errors and improving fault detection accuracy. For details, please refer to the description of step S102 and will not be repeated here.

[0149] Step S111 , determining whether the first conduction voltage is less than a first voltage threshold.

[0150] As described in step S103 above, if the neutral switch has an open circuit fault and cannot be closed normally, the voltage between the midpoint BUSN and the neutral interface will not be less than the first voltage threshold. If the neutral switch is closed normally and no open circuit fault occurs, the voltage between the midpoint BUSN and the neutral interface will be less than the first voltage threshold.

[0151] Based on this, in step S111 , by comparing the first conduction voltage with the first voltage threshold, it can be preliminarily determined whether the neutral line switch has an open circuit fault.

[0152] Step S112: If the first conduction voltage is less than the first voltage threshold, control the switch to switch to a relative state; the first state and the second state are relative states.

[0153] As mentioned above, the voltage V between the midpoint and the neutral line interface BUSN_GN The magnitude of will vary depending on the wiring conditions of power grid 400. Therefore, in step S112, when the first conduction voltage is less than the first voltage threshold, only a preliminary determination can be made that the neutral switch may not have an open-circuit fault, but the possibility of an open-circuit fault in the neutral switch cannot be completely ruled out. Therefore, if the determination that the neutral switch does not have an open-circuit fault is based solely on the first conduction voltage being less than the first voltage threshold, a misjudgment may occur.

[0154] Therefore, in step S112 , when the first turn-on voltage is less than the first voltage threshold, the controller 40 may further control the switch S1 to switch its state.

[0155] If the switch S1 is controlled to be in the first state in step S109, the switch S1 is controlled to be in the second state in step S112. If the switch S1 is controlled to be in the second state in step S109, the switch S1 is controlled to be in the first state in step S112.

[0156] Step S113A: Acquire a second conduction voltage between the midpoint and the neutral line interface.

[0157] In step S113A, the controller 40 may obtain the second conduction voltage between the midpoint BUSN and the neutral line interface by sampling through a voltage sampling device or a voltage sampling circuit. Detailed descriptions of step S110A may be referred to and will not be repeated here.

[0158] Step S114: determine whether the second conduction voltage is less than the first voltage threshold.

[0159] In step S114A, by comparing the second conduction voltage with the first voltage threshold, a change in the magnitude of the second conduction voltage can be determined, so as to determine again whether the neutral line switch has an open circuit fault.

[0160] Step S115A: If the second conduction voltage is less than the first voltage threshold, it is determined that the neutral line switch does not have an open circuit fault.

[0161] It can be understood that if the neutral line switch can be closed normally, then even if the switch is switched, the voltage V between the midpoint and the neutral line interface BUSN_GN It is also not affected, so the voltage V between the midpoint and the neutral line interface is BUSN_GN It will still be less than the first voltage threshold.

[0162] Conversely, if the neutral switch has an open circuit fault, then according to the above formula (3), the voltage V between the midpoint and the neutral interface is BUSN_GN Will inevitably be affected by V R3 Therefore, when the second conduction voltage is less than the first voltage threshold, it can be determined that the neutral line switch can be closed normally and there is no open circuit fault.

[0163] Step S116A: If the first conduction voltage and / or the second conduction voltage is not less than the first voltage threshold, it is determined that an open circuit fault occurs in the neutral line switch.

[0164] It can be understood that if the neutral line switch can be closed normally, the neutral line switch can be regarded as a section of wire. At this time, no matter which state the switching switch S1 is in, the voltage at both ends of the wire is zero or almost zero, that is, the first conduction voltage and the second conduction voltage are both zero or almost zero.

[0165] Therefore, when either the first conduction voltage or the second conduction voltage is not less than the first voltage threshold, it can be determined that the neutral line switch is not normally closed, that is, an open circuit fault occurs in the neutral line switch.

[0166] It can be seen that the fault detection method of the embodiment of the present application can accurately diagnose whether an open circuit fault occurs in the neutral line switch or not, which is more conducive to ensuring that the inverter circuit 10 can normally realize the single-phase power conversion function.

[0167] In some embodiments of the present application, in order to ensure the normal implementation of the single-phase inverter function of the inverter circuit 10, the fault detection method can also detect wiring faults of the neutral line and the ground line.

[0168] For details, please refer to Figure 4 and Figure 5 After controlling the live line switch to be disconnected, controlling the neutral line switch to be closed, and controlling the transfer switch to be in the first state or the second state (i.e., the above-mentioned step S109), the fault detection method further includes:

[0169] Step S110B: Obtain a first ground voltage between the midpoint and the ground line.

[0170] In step S110B, the controller 40 may control the neutral line switch to be closed, wait for a preset time, and then obtain the first ground voltage V between the midpoint BUSN and the ground line PE through a voltage sampling device or a voltage sampling circuit. BUSN_PE1 (Not shown in the figure.) In this way, the error of voltage sampling can be reduced, which is conducive to improving the accuracy of fault detection. For details, please refer to the relevant description of step S110A, which will not be repeated here.

[0171] In some embodiments, after controlling the switch to switch to the relative state (i.e., step S112 above), the method further includes:

[0172] Step S113B: Obtain a second ground voltage between the midpoint and the ground line.

[0173] In step S113B, the controller 40 can obtain the second ground voltage V between the midpoint BUSN and the ground line PE by sampling through a voltage sampling device or a voltage sampling circuit. BUSN_PE2 (Not shown in the figure).

[0174] Step S114B: determine whether the voltage difference between the first voltage-to-ground and the second voltage-to-ground is greater than a second voltage threshold.

[0175] Understandably, according to Figure 2 The loop shown yields:

[0176] V BUSN_PE =-V R3 +V BUS- (4)

[0177] Since the voltage V of the negative DC bus BUS- relative to the midpoint BUSN BUS- remains unchanged, so the first voltage to ground V BUSN_PE1 and the second ground voltage V BUSN_PE2 The voltage difference between △V=V BUSN_PE1 -V BUSN_PE2 =V R32 -V R31 Among them, V R31 (not shown) is the voltage of the voltage divider resistor R3 after step S109, V R32 (not shown in the figure) is the voltage of the voltage-dividing resistor R3 after step S112.

[0178] As mentioned above, when the neutral line GN is connected to the ground line PE, when the neutral line switch is closed, V R3 will be clamped to V BUS- Therefore, even if the switch switches state, V BUSN_PE1 =V BUSN_PE2 =0, ΔV=0, that is, ΔV is not greater than the second voltage threshold.

[0179] If the neutral line GN and the ground line PE are not properly connected (i.e., neutral line grounding fault), and / or the ground line PE is not properly grounded (i.e., ground line connection fault), then V R3 Not clamped, after the switch S1 switches state, V R3 will change. BUS- remains unchanged, resulting in V BUSN_PE Will also follow V R3 Therefore, the first voltage to ground V BUSN_PE1 and the second ground voltage V BUSN_PE2 There will be a certain voltage difference △V between them.

[0180] For example, assuming that the resistance of the voltage divider resistor R1 is 236Kohm, the resistance of the voltage divider resistor R2 is 6190Kohm, the resistance of the voltage divider resistor R3 is 5170Kohm, RX is 2000Kohm, RY is 2000Kohm, and Vbus is 500V. According to the above formulas (1) and (2), when the switch S1 is normally opened, V R31 =243V; when the switch S1 is normally closed, V R32 =436V. Therefore, the voltage difference △V=V R32 -V R31 =436V-243V=193V, which is greater than the second voltage threshold.

[0181] Therefore, in step S114B, by comparing the voltage difference with the second voltage threshold, the magnitude of the voltage difference can be determined, so as to judge whether there is a wiring fault between the neutral line and the ground line.

[0182] The second voltage threshold can be set to a relatively small value, which can be set according to the requirements of the actual application scenario and is not specifically limited here. For example, the second voltage threshold can be a voltage value close to 0, such as 1V, 2V, or 5V.

[0183] Step S115B: If the voltage difference between the first voltage-to-ground and the second voltage-to-ground is greater than the second voltage threshold, it is determined that a wiring fault occurs in at least one of the neutral line and the ground line.

[0184] That is to say, the neutral line GN and / or the ground line PE have a ground fault, which causes V R3 The first ground voltage and the second ground voltage are not clamped, so that the voltage difference between the first ground voltage and the second ground voltage is greater than the second voltage threshold. Therefore, according to the voltage difference being greater than the second voltage threshold, it can be determined that at least one of the neutral line GN and the ground line PE is abnormally connected, and a wiring fault occurs.

[0185] Step S116B: If the voltage difference between the first voltage-to-ground and the second voltage-to-ground is not greater than the second voltage threshold, it is determined that no wiring fault occurs between the neutral line and the ground line.

[0186] When the voltage difference △V is not greater than the second voltage threshold, it means V R3 is clamped, causing the switch S1 to switch state before and after, V R3 Therefore, it can be determined that the neutral line switch is closed, and the neutral line GN and ground line PE are connected normally, and there is no wiring fault.

[0187] Therefore, through the above-mentioned step S110B and steps S113B to S116B, it is possible to accurately diagnose whether a wiring fault occurs in the neutral line GN and the ground line PE, which is beneficial to ensuring the safe operation of the inverter circuit 10.

[0188] It is understood that step S110B and the above step S110A are performed independently. Steps S113B to S116B and the above steps S113A to S116A are performed independently.

[0189] In addition, since the grid-connected switch 20 includes a live wire switch in addition to a neutral wire switch, the fault detection method can also detect a sticking fault of the live wire switch through steps S117 to S121.

[0190] In an embodiment of the present application, steps S117 to S121 may be performed after determining that the neutral line switch has not had a sticking fault. More specifically, in some embodiments, steps S117 to S121 may be performed after step S108 (i.e., after completing the neutral line switch sticking fault detection). In other embodiments, steps S117 to S121 may also be performed after step 115A (i.e., after completing the neutral line switch sticking fault detection and open circuit fault detection), or after step S116B (i.e., after completing the neutral line switch sticking fault detection, open circuit fault detection, and the neutral line and ground line wiring fault).

[0191] It should be understood that in some other embodiments, steps S117 to S121 may also be performed independently, or performed before the neutral line switch fault is detected (for example, before step S101 or before step S109).

[0192] For details, please refer to Figure 4 and Figure 6 , the fault detection method may further include:

[0193] Step S117: Control the live line switch to be open, and control the neutral line switch to be closed.

[0194] by Figure 2 Taking the circuit shown as an example, the controller 40 controls the live wire switches corresponding to all live wire output terminals to be disconnected and controls the neutral wire switches to be closed.

[0195] Step S118: Acquire a third disconnection voltage between the live wire output terminal and the live wire interface.

[0196] Since the live wire switch is connected between the live wire output terminal and the live wire interface, the third disconnection voltage between the live wire output terminal and the live wire interface is the voltage across the live wire switch when the live wire switch is controlled to be disconnected.

[0197] by Figure 2Taking the circuit shown as an example, the controller 40 can control the live switches corresponding to all live output terminals to be disconnected, and then sample the voltages at both ends of each live switch / live switch group through a voltage sampling device or a voltage sampling circuit to obtain a third disconnection voltage between the live output terminal INVL1 and the corresponding live interface, between the live output terminal IINVL2 and the corresponding live interface, and between the live output terminal INVL3 and the corresponding live interface.

[0198] Step S119: determine whether the third disconnection voltage is less than a third voltage threshold.

[0199] It can be understood that if all live wire switches are normally disconnected, there should be a certain voltage difference between the live wire output terminal INVL1 and the live wire GL1, between the live wire output terminal INVL2 and the live wire GL2, and between the live wire output terminal INVL3 and the live wire GL3.

[0200] If the live wire switch corresponding to the live wire output terminal INVL1 is stuck, the live wire output terminal INVL1 of the inverter circuit 10 is directly connected to the live wire GL1. Therefore, the voltage difference between the live wire output terminal INVL1 and the live wire GL1 is very small, and the voltage difference between the live wire output terminal INVL1 and the live wire GL1 is zero or nearly zero.

[0201] If the live switch corresponding to the live output terminal INVL2 is stuck, the live output terminal INVL2 of the inverter circuit 10 is directly connected to the live line GL2, and the voltage difference between the live output terminal INVL2 and the live line GL2 is zero or nearly zero.

[0202] If the live switch corresponding to the live output terminal INVL3 is stuck, the live output terminal INVL3 of the inverter circuit 10 is directly connected to the live line GL3, and the voltage difference between the live output terminal INVL3 and the live line GL3 is zero or nearly zero.

[0203] Therefore, in step S119, by comparing the third disconnection voltage between each phase live wire and a corresponding live wire output terminal with the third voltage threshold, the magnitude of the third disconnection voltage can be determined to facilitate judging whether the live wire switch is stuck.

[0204] The third voltage threshold can be set according to actual conditions, for example, the third voltage threshold can be set to 0.5% Un or other voltage values. 0.5% Un is an empirical value.

[0205] Step S120A: If the third disconnection voltage is less than the third voltage threshold, it is determined that a sticking fault occurs in the live wire switch.

[0206] That is, when the third disconnect voltage is less than the third voltage threshold, it indicates that the hot wire switch is stuck, resulting in a small voltage difference between the hot wire output terminal and the hot wire. Therefore, based on the third disconnect voltage being less than the third voltage threshold, it can be determined that the hot wire switch has a stuck fault.

[0207] When the voltage difference between the live wire output terminal INVL1 and the live wire GL1 is less than a third voltage threshold, it can be determined that a sticking fault has occurred in the live wire switch corresponding to the live wire output terminal INVL1. When the voltage difference between the live wire output terminal INVL2 and the live wire GL2 is less than a third voltage threshold, it can be determined that a sticking fault has occurred in the live wire switch corresponding to the live wire output terminal INVL1. When the voltage difference between the live wire output terminal INVL1 and the live wire GL1 is less than a third voltage threshold, it can be determined that a sticking fault has occurred in the live wire switch corresponding to the live wire output terminal INVL1.

[0208] Step S120B: If the third disconnection voltage is not less than the third voltage threshold, it is determined that the live wire switch does not have a sticking fault.

[0209] That is, when the third disconnect voltage is not less than the third voltage threshold, it indicates that the hot wire switch is not stuck, resulting in a certain voltage difference between the hot wire output terminal and the hot wire. Therefore, based on the third disconnect voltage being not less than the third voltage threshold, it can be determined that the hot wire switch is not stuck.

[0210] When the voltage difference between the live wire output terminal INVL1 and the live wire GL1 is not less than a third voltage threshold, it can be determined that the live wire switch corresponding to the live wire output terminal INVL1 has not experienced a sticking fault. When the voltage difference between the live wire output terminal INVL2 and the live wire GL2 is not less than a third voltage threshold, it can be determined that the live wire switch corresponding to the live wire output terminal INVL1 has not experienced a sticking fault. When the voltage difference between the live wire output terminal INVL1 and the live wire GL1 is not less than the third voltage threshold, it can be determined that the live wire switch corresponding to the live wire output terminal INVL1 has experienced a non-sticking fault.

[0211] It can be seen that the fault detection method of the embodiment of the present application can not only detect the fault of the neutral line switch, but also detect the adhesion fault of the live line switch, thereby achieving comprehensive detection of the fault of the grid-connected switch 20, which is more conducive to ensuring the safe grid connection of the inverter circuit 10.

[0212] In some embodiments, the live switch is a switch group, and a group of live switches may be composed of multiple sub-live switches connected in series. Therefore, in actual applications, the above steps S117 to S120B may be performed for each sub-live switch to detect the sticking fault of the sub-live switch.

[0213] by Figure 2 The circuit shown is an example. Figure 4For the first sub-live switches K11, K21, and K31, the above steps S117 to S120B may be performed to detect the adhesion fault of the first sub-live switches K11, K21, and K31, wherein:

[0214] In step S117 , the process of controlling the live switch to be disconnected may include: controlling the first sub-live switch to be disconnected, and controlling the second sub-live switch to be closed.

[0215] Accordingly, the process in step S120A may include: if the third disconnection voltage is less than the third voltage threshold, determining that a sticking fault occurs in the first sub-live wire switch.

[0216] The process in step S120B may include: if the third disconnection voltage is not less than a third voltage threshold, determining that no sticking fault occurs in the first sub-live wire switch.

[0217] For the second sub-live switches K12, K22, and K32, the above steps S117 to S120B may be performed again to detect the adhesion fault of the second sub-live switches K12, K22, and K32, wherein:

[0218] In step S117 , the process of controlling the live switch to be disconnected may include: controlling the second sub-live switch to be disconnected, and controlling the first sub-live switch to be closed.

[0219] Accordingly, the process in step S120A may include: if the third disconnection voltage is less than the third voltage threshold, determining that a sticking fault occurs in the second sub-live wire switch.

[0220] The process in step S120B may include: if the third disconnection voltage is not less than the third voltage threshold, determining that no sticking fault occurs in the second sub-live wire switch.

[0221] Thus, the methods for detecting whether the first sub-live switch is stuck and detecting whether the second sub-live switch is stuck are essentially the same. Both methods involve disconnecting the sub-live switch to be tested and closing the other sub-live switches to perform a separate sticking test on the sub-live switch to be tested. Furthermore, the sub-live switch to be used as the first sub-live switch can be defined independently. Therefore, in actual applications, if the live switch contains multiple sub-live switches, each sub-live switch can be defined as the first sub-live switch in turn. By executing multiple fault detection methods to detect whether different sub-live switches are stuck, it is possible to comprehensively and precisely detect the sticking fault conditions of each live sub-switch in the live switch, which is beneficial for improving fault detection accuracy and electrical safety.

[0222] In some embodiments of the present application, after determining that a live switch has a sticking fault, and / or a neutral switch has a sticking fault, and / or an open circuit fault occurs in the neutral switch, and / or a wiring fault occurs in at least one of the neutral line and the ground line (i.e., after step S120A), reference may be made to Figure 6 , the fault detection method may further include the following steps:

[0223] S121A, control the inverter circuit to stop running.

[0224] In some embodiments of the present application, after determining that the live wire switch has no adhesion fault (ie, after step S120B), the inverter circuit 10 can be put into use. Figure 6 , the fault detection method may further include the following steps:

[0225] S121B, control the live wire switch and neutral wire switch to close.

[0226] S122B. After the live wire switch and the neutral wire switch are closed, the inverter circuit is controlled to operate in grid connection.

[0227] It can be understood that before determining that the live wire switch has no sticking fault, it has been determined that the neutral wire switch has no sticking fault and no open circuit fault, and that at least one of the neutral wire and the ground wire has no wiring fault.

[0228] In some embodiments, when a fault is detected, the fault detection method may further include:

[0229] When any type of fault is detected, the corresponding type of fault prompt information is output.

[0230] The fault prompt information may be used to indicate the type of fault.

[0231] For example, if a neutral switch sticking fault is detected, the controller 40 may output neutral switch sticking fault prompt information to alert the power device 300 of the presence of a neutral switch sticking fault. If a neutral switch open circuit fault is detected, the controller 40 may output neutral switch open circuit fault prompt information to alert the power device 300 of the presence of a neutral switch open circuit fault. If a wiring fault is detected in at least one of the neutral and ground wires, the controller 40 may output wiring fault prompt information to alert the power device 300 of the presence of a wiring fault. If a hot wire switch sticking fault is detected, the controller 40 may output hot wire switch sticking fault prompt information to alert the power device 300 of the presence of a hot wire switch sticking fault.

[0232] The above fault prompt information can be prompted through any one or more combinations of sound, light, vibration, text and other forms of expression.

[0233] For example, in one embodiment, Figure 1 The illustrated scene may further include an independent display screen, or any device in the scene may be provided with a display screen. The controller 40 may output the fault prompt information to the display screen to visually display the fault prompt information.

[0234] In another embodiment, the controller 40 may also output the fault prompt information to the device side or the APP side via wireless communication. In this way, it is convenient for the user or relevant personnel to know the fault of the current power device 300 and then take corresponding maintenance measures to eliminate the fault.

[0235] It should be noted that, for the aforementioned method embodiments, for the sake of simplicity of description, they are all expressed as a series of action combinations, but those skilled in the art should know that this application is not limited to the described order of actions, because according to this application, certain steps can be performed in other orders or simultaneously.

[0236] See also Figure 2 and Figure 4 , the following will be combined Figure 2 The circuit structure shown and Figure 4 The control signal shown is used to exemplify the fault detection method provided in the embodiment of the present application.

[0237] In this example scenario, the open state of the switch S1 is the first state, and the closed state of the switch S1 is the second state.

[0238] At time T1, a control signal is sent to the first sub-neutral line switch K41 to control the first sub-neutral line switch K41 to be closed, and a first disconnection voltage between the midpoint BUSN and the neutral line interface is detected.

[0239] At time T2, a control signal is sent to the switch S1 to control the switch S1 to close, and a second disconnection voltage between the midpoint BUSN and the neutral line interface is detected.

[0240] When the first disconnection voltage and / or the second disconnection voltage is not less than the first voltage threshold, it is determined that no sticking fault occurs in the second sub-neutral line switch K42.

[0241] At time T3, the control signal is stopped from being sent to the first sub-neutral line switch K41, and the control signal is stopped from being sent to the switch S1, so that the first sub-neutral line switch K41 and the switch S1 are disconnected.

[0242] At time T4, a control signal is sent to the second sub-neutral line switch K42 to control the second sub-neutral line switch K42 to be closed, and a first disconnection voltage between the midpoint BUSN and the neutral line interface is detected.

[0243] At time T5, a control signal is sent to the switch S1 to control the switch S1 to close, and a second disconnection voltage between the midpoint BUSN and the neutral line interface is detected.

[0244] When the first disconnection voltage and / or the second disconnection voltage is not less than the first voltage threshold, it is determined that no sticking fault occurs in the first sub-neutral line switch K41.

[0245] At time T6, stop sending the control signal to the switching switch S1, send the control signal to the first sub-neutral line switch K41, control the first sub-neutral line switch K41 to close, detect the first conduction voltage between the midpoint BUSN and the neutral line interface, and detect the first ground voltage between the midpoint BUSN and the ground line.

[0246] At time T7, a control signal is sent to the switch S1 to control the switch S1 to close, detect the second conduction voltage between the midpoint BUSN and the neutral line interface, and detect the second ground voltage between the midpoint BUSN and the ground line.

[0247] When both the first conduction voltage and the second conduction voltage are less than the first voltage threshold, it is determined that the first sub-neutral line switch K41 and the second sub-neutral line switch K42 do not have an open circuit fault.

[0248] A voltage difference between the first voltage to ground and the second voltage to ground is calculated, and when the voltage difference between the first voltage to ground and the second voltage to ground is not greater than a second voltage threshold, it is determined that no wiring fault occurs between the neutral line and the ground line.

[0249] At time T8, the control signal to the switch S1 is stopped, and the control signals are sent to the second live wire switches K12, K22, and K32 to close. The third disconnection voltage between each live wire output terminal and the corresponding live wire interface is detected respectively.

[0250] When the third disconnection voltages between each live wire output terminal and the corresponding live wire interface are all less than the third voltage threshold, it is confirmed that no adhesion failure occurs in the first live wire sub-switches K11 , K21 and K31 .

[0251] At time T9, the control signals sent to the second sub-live switches K12, K22 and K32 are stopped, and the second sub-live switches K12, K22 and K32 are controlled to be disconnected.

[0252] At time T10, a control signal is sent to the first live wire switches K11, K21 and K31 to control the first live wire switches K11, K21 and K31 to be closed. A third disconnection voltage is detected between each live wire output terminal and the corresponding live wire interface.

[0253] When the third disconnection voltage between each live wire output terminal and the corresponding live wire interface is less than the third voltage threshold, it is confirmed that no adhesion failure occurs in the second live wire sub-switches K12, K22 and K32.

[0254] At time T11, after determining that the first neutral line switch K41 and the second neutral line switch K42 have no adhesion fault and circuit breakage fault, the first sub-live line switches K11, K21 and K31 and the second sub-live line switches K12, K22 and K32 have no adhesion fault, and the neutral line and the ground line have no wiring fault, a control signal is sent to the second sub-live line switches K12, K22 and K32 to control the second sub-live line switches K12, K22 and K32 to be closed, thereby allowing the inverter circuit to operate in grid connection.

[0255] See also Figure 7 , shows a structural diagram of an electronic device 600 provided in an embodiment of the present application.

[0256] like Figure 7 As shown, the electronic device 600 may include a processor 601 and a memory 602 .

[0257] The processor 601 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0258] The memory 602 may be a read-only memory (ROM) or other type of static storage device that can store static information and instructions, a random access memory (RAM) or other type of dynamic storage device that can store information and instructions, or an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, an optical disc storage (including a compact disc, laser disc, optical disc, digital versatile disc, Blu-ray disc, etc.), a magnetic disk storage medium or other magnetic storage device, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited thereto. The memory 602 may exist independently and be connected to the processor 601 via a bus. The memory 602 may also be integrated with the processor 601.

[0259] The memory 602 is used to store programs, instructions, or codes for executing the above fault detection method. The processor 601 is used to execute the programs, instructions, or codes stored in the memory 602. The programs, instructions, or codes stored in the memory 602 can execute some or all of the steps of the fault detection method in the above embodiment.

[0260] See also Figure 8 , shows a schematic diagram of a fault detection device 700 provided in an embodiment of the present application. The fault detection device 700 can be applied to power equipment and can be used to implement the above-mentioned fault detection method.

[0261] Specifically, if Figure 8 As shown, the fault detection device 700 includes a first control module 701 , a first acquisition module 702 , a second control module 703 , a second acquisition module 704 and a fault judgment module 705 .

[0262] The first control module 701 is used to control the live wire switch to be disconnected, control the neutral wire switch to be disconnected, and control the switching switch to be in the first state.

[0263] The first acquisition module 702 is configured to acquire a first disconnection voltage between the midpoint and the neutral line interface.

[0264] The second control module 703 is configured to control the switch to switch to the second state when the first disconnection voltage is less than the first voltage threshold.

[0265] The second acquisition module 704 is configured to acquire a second disconnection voltage between the midpoint and the neutral line interface.

[0266] The fault judgment module 705 is configured to determine that a neutral line switch has a sticking fault when the second disconnection voltage is less than a first voltage threshold.

[0267] It is understandable that the division of the various modules in the above-mentioned fault detection device 700 is only for illustration. In other embodiments, the fault detection device 700 can be divided into different modules as needed to complete all or part of the functions of the above-mentioned fault detection device 700.

[0268] The specific implementation of each module in the embodiment of the present application can also refer to the corresponding description of the above-mentioned fault detection method embodiment, so it will not be described in detail here.

[0269] The functional modules in the embodiments of the present application may all be integrated into one processing module / unit, or each module may be a separate module, or two or more modules may be integrated into one module; the above-mentioned integrated modules may be implemented in the form of hardware or in the form of hardware plus software functional modules.

[0270] If the above-mentioned integrated module of the present application is implemented in the form of a software function module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the embodiment of the present application is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium and includes a number of instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the methods described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as mobile storage devices, ROM, RAM, magnetic disks or optical disks.

[0271] The present application also provides a computer-readable storage medium for storing a computer program or code, which, when loaded and executed by a processor, implements all or part of the steps in the above-mentioned fault detection method embodiment. The computer-readable storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules or other data). For a specific embodiment of the computer-readable storage medium, see Figure 7 The description of the memory 602 in will not be repeated here.

[0272] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A fault detection method, characterized in that: Applied to a power device, the power device includes an inverter circuit, a grid-connected switch, and a grid-connected interface, the grid-connected switch includes a live wire switch and a neutral wire switch, and the grid-connected interface includes a live wire interface and a neutral wire interface; the DC end of the inverter circuit and the insulation detection circuit are connected in parallel between a positive DC bus and a negative DC bus, and a first bus capacitor and a second bus capacitor of the inverter circuit are connected in series between the positive DC bus and the negative DC bus; the live wire output end of the inverter circuit is connected to the live wire interface via the live wire switch, and the midpoint of the first bus capacitor and the second bus capacitor is connected to the neutral wire interface via the neutral wire switch; the live wire interface is also used to connect to the live wire of the power grid, and the neutral wire interface is also used to connect to the neutral wire of the power grid; the insulation detection circuit includes a voltage divider circuit and a switching switch, the voltage divider circuit is also connected to the ground wire, and the switching switch is used to connect or shield at least one voltage divider resistor in the voltage divider circuit; the fault detection method includes: Controlling the live wire switch to be disconnected, controlling the neutral wire switch to be disconnected, and controlling the switching switch to be in a first state; Acquiring a first disconnection voltage between the midpoint and the neutral line interface; If the first disconnect voltage is less than a first voltage threshold, controlling the switch to switch to a second state; Acquiring a second disconnection voltage between the midpoint and the neutral line interface; If the second disconnect voltage is less than the first voltage threshold, it is determined that a sticking fault occurs in the neutral line switch.

2. The fault detection method according to claim 1, wherein: The method further comprises: If the first disconnection voltage and / or the second disconnection voltage is not less than the first voltage threshold, it is determined that no sticking fault occurs in the neutral line switch.

3. The fault detection method according to claim 1, wherein: The neutral line switch is composed of a first sub-neutral line switch and a second sub-neutral line switch connected in series; The controlling the neutral line switch to be disconnected includes: controlling the first sub-neutral line switch to be opened and controlling the second sub-neutral line switch to be closed; Correspondingly, if the second disconnect voltage is less than the first voltage threshold, determining that a sticking fault occurs in the neutral line switch includes: If the second disconnect voltage is less than the first voltage threshold, it is determined that a sticking fault occurs in the first sub-neutral line switch.

4. The fault detection method according to claim 2, wherein: The method further comprises: When it is determined that the neutral line switch does not have a sticking fault, controlling the live line switch to be opened, controlling the neutral line switch to be closed, and controlling the transfer switch to be in the first state or the second state; Acquiring a first conduction voltage between the midpoint and the neutral line interface; If the first conduction voltage is less than the first voltage threshold, the switch is controlled to switch to a relative state; the first state and the second state are relative states; Acquiring a second conduction voltage between the midpoint and the neutral line interface; If the second conduction voltage is less than the first voltage threshold, it is determined that no open circuit fault occurs in the neutral line switch.

5. The fault detection method according to claim 4, wherein: After controlling the live switch to be open, controlling the neutral switch to be closed, and controlling the transfer switch to be in the first state or the second state, the method further includes: Obtaining a first ground voltage between the midpoint and the ground line; After controlling the switch to switch to the relative state, the method further includes: Obtaining a second ground voltage between the midpoint and the ground line; If a voltage difference between the first voltage-to-ground and the second voltage-to-ground is greater than a second voltage threshold, determining that a wiring fault occurs in at least one of the neutral line and the ground line; If the voltage difference between the first voltage-to-ground and the second voltage-to-ground is not greater than the second voltage threshold, it is determined that no wiring fault occurs between the neutral line and the ground line.

6. The fault detection method according to claim 1, wherein: The fault detection method further includes: Controlling the live wire switch to be disconnected and controlling the neutral wire switch to be closed; obtaining a third disconnection voltage between the live wire output terminal and the live wire interface; If the third disconnect voltage is less than a third voltage threshold, it is determined that a sticking fault occurs in the live wire switch; If the third disconnection voltage is not less than the third voltage threshold, it is determined that no sticking fault occurs on the live wire switch.

7. The fault detection method according to claim 6, wherein: The live wire switch is composed of a first sub-live wire switch and a second sub-live wire switch connected in series; The controlling the live wire switch to be disconnected comprises: Controlling the first sub-live wire switch to be disconnected, and controlling the second sub-live wire switch to be closed; Correspondingly, if the third disconnection voltage is not less than a third voltage threshold, determining whether a sticking fault occurs on the live wire switch includes: If the third disconnection voltage is not less than the third voltage threshold, it is determined that no adhesion fault occurs in the first sub-live wire switch.

8. The fault detection method according to claim 6, wherein: After determining that the live wire switch does not have a sticking fault, the method further includes: Controlling the live wire switch and the neutral wire switch to be closed; After the live line switch and the neutral line switch are closed, the inverter circuit is controlled to operate in parallel with the grid.

9. The fault detection method according to any one of claims 1 to 8, characterized in that: The method further comprises: When any type of fault is detected, the corresponding type of fault prompt information is output.

10. A power device, characterized in that: The invention comprises an inverter circuit, a grid-connected switch, a grid-connected interface, and a controller, wherein the grid-connected switch comprises a live wire switch and a neutral wire switch, and the grid-connected interface comprises a live wire interface and a neutral wire interface; the DC end of the inverter circuit and the insulation detection circuit are connected in parallel between a positive DC bus and a negative DC bus, and a first bus capacitor and a second bus capacitor of the inverter circuit are connected in series between the positive DC bus and the negative DC bus; the live wire output end of the inverter circuit is connected to the live wire interface via the live wire switch, and the midpoint of the first bus capacitor and the second bus capacitor is connected to the neutral wire interface via the neutral wire switch; the live wire interface is further used to connect to the live wire of a power grid, and the neutral wire interface is further used to connect to the neutral wire of the power grid; the insulation detection circuit comprises a voltage divider circuit and a switching switch, the voltage divider circuit is further connected to the ground wire, and the switching switch is used to connect or shield at least one voltage divider resistor in the voltage divider circuit; and the controller is used to execute the fault detection method according to any one of claims 1 to 9.

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