Inverter, photovoltaic power generation system and switch detection method

Abstract

The invention provides an inverter, a photovoltaic power generation system and a switch detection method, and the method comprises the steps: transmitting a state change instruction to one switch when two switches connected in series between a neutral line and a grounding line are in the same closed state or open state, and reporting a short-circuit fault if the NPE voltage is smaller than a set voltage value; when the two switches are in different closed states or open states, state change instructions are sent to the two switches, and if the NPE voltage is smaller than a set voltage value, a short-circuit fault is reported; and when the two switches are in different closed states or open states, a closing instruction is sent to one switch, and if the NPE voltage is greater than a set voltage value, an open fault is reported. According to the fault detection method, one-by-one troubleshooting of switch faults is carried out in the dynamic switching process of the switch, and fault detection and switching of the closed state or the open state of the switch can be completed in a short time. In addition, short-circuit faults of the two switches can be detected, and fault detection is comprehensive and efficient.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to an inverter, a photovoltaic power generation system and a switch detection method. Background Art

[0002] Relay is a mechanical switching device that can be used for on / off control of photovoltaic systems, electromechanical systems, etc. Common relay faults include contact adhesion failure that cannot be controlled to disconnect and contact open circuit failure that cannot be controlled to close. Therefore, in practical applications, it is necessary to promptly detect whether the relay has the above faults.

[0003] At present, a common method for detecting whether a relay is faulty is to detect the voltage across the contact pins of a single relay, i.e., the contact voltage, when the relay is in a steady state, to determine whether the relay is faulty. The above fault detection method can only detect whether a single relay is faulty and cannot be applied to scenarios where two relays are connected in series. Moreover, the above fault detection method can only detect one type of fault when the relay is in a certain steady state and cannot identify two faults. For example, when the relay is in the energized state, it can only detect whether the relay has an open contact fault; when the relay is in the disconnected state, it can only detect whether the relay has a contact adhesion fault. Summary of the invention

[0004] The present application provides an inverter, a photovoltaic power generation system and a switch detection method, which are used to detect the fault type of the switch.

[0005] In a first aspect, the present application provides an inverter, comprising: an inverter circuit, an off-grid switch, a neutral line, a ground line, two switches arranged in series, and a controller; wherein the neutral line is arranged between the inverter circuit and the load, and the off-grid switch is arranged on the neutral line. One end of the two switches is connected to the ground line, and the other end of the two switches is connected to the neutral line between the inverter circuit and the off-grid switch, or the other end of the two switches is connected to the neutral line between the off-grid switch and the load. The controller is used to perform one or more of the following operations: when the two switches are in the same closed state or open state, a state change instruction is sent to one of the two switches, the state change instruction is a closing instruction or an opening instruction, and if the voltage between the neutral line and the grounding line is less than the set voltage value, a short circuit fault is reported; or, when the two switches are in different closed states or open states, a state change instruction is sent to both switches, and if the voltage between the neutral line and the grounding line is less than the set voltage value, a short circuit fault is reported; or, when the two switches are in different closed states or open states, a closing instruction is sent to one switch, and if the voltage between the neutral line and the grounding line is greater than the set voltage value, a opening fault is reported.

[0006] The present application provides the above-mentioned inverter, when the two switches connected in series between the neutral line and the ground line are in the same closed state or open state, the controller sends a state change instruction to one switch, and if the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported; when the two switches are in different closed states or open states, a state change instruction is sent to both switches, and if the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported; when the two switches are in different closed states or open states, a closing instruction is sent to one switch, and if the voltage between the neutral line and the ground line is greater than the set voltage value, a disconnection fault is reported. The above-mentioned fault detection method checks the switch faults one by one in the dynamic process of switch switching, and can complete the fault detection and the switching of the switch closed state or open state in a short time. In addition, the short circuit faults of both switches can be detected, and the fault detection is comprehensive and efficient.

[0007] In some embodiments of the present application, the controller is specifically used to: when both switches are in an open state, send a closing command to one of the two switches, and if the voltage between the neutral line and the ground line is less than a set voltage value, report that the other of the two switches has a short circuit fault; or, when both switches are in a closed state, send an opening command to one of the two switches, and if the voltage between the neutral line and the ground line is less than a set voltage value, report that one of the two switches has a short circuit fault.

[0008] In some embodiments of the present application, the controller is specifically used to: when one of the two switches is in a closed state and the other switch is in an open state, send an opening command to one of the two switches and a closing command to the other switch; if the voltage between the neutral line and the ground line is less than a set voltage value, report that a short circuit fault has occurred in one of the two switches.

[0009] In some embodiments of the present application, the controller is specifically used to: when one of the two switches is in an open state and the other switch is in a closed state, send a closing instruction to one of the two switches, and if the voltage between the neutral line and the ground line is greater than a set voltage value, report a disconnection fault in either of the two switches.

[0010] In some embodiments of the present application, the controller is also used to: when both switches are in an open state, send a closing command to one of the two switches; if the voltage between the neutral line and the ground line is greater than a set voltage value, send an opening command to one of the two switches and send a closing command to the other switch; if the voltage between the neutral line and the ground line is greater than the set voltage value, send a closing command to one of the two switches.

[0011] The switch fault detection method is to check the switch faults one by one in the dynamic process of switch switching, and the detection time is short. The fault detection and the switching of the switch closed state and the open state can be completed in a short time. Moreover, in the process of switching the two switches from the open state to the closed state, the open faults and short-circuit faults of the two switches can be detected, and the fault detection is comprehensive and efficient.

[0012] In some embodiments of the present application, the controller is also used to: when both switches are in a closed state, send a disconnect command to one of the two switches; if the voltage between the neutral line and the ground line is greater than a set voltage value, send a close command to one of the two switches and send a disconnect command to the other switch; if the voltage between the neutral line and the ground line is greater than the set voltage value, send a disconnect command to one of the two switches.

[0013] The switch fault detection method is to check the switch faults one by one in the dynamic process of switch switching, and the detection time is short. The fault detection and the switching of the switch closed state and the open state can be completed in a short time. Moreover, in the process of switching the two switches from the open state to the closed state, the short circuit faults of the two switches can be detected, and the fault detection is comprehensive and efficient.

[0014] In a second aspect, the present application provides a photovoltaic power generation system, comprising: an inverter, a grid-connected and off-grid switching device, a neutral line, a ground line, two switches arranged in series, and a controller; wherein the inverter comprises: an inverter circuit and a grid-connected switch, and the grid-connected and off-grid switching device comprises: an inverter side switch, a grid side switch, and a load side switch connected to each other, and the grid-connected switch is connected to the inverter side switch. The neutral line is arranged between: the inverter circuit and the grid-connected switch, between the grid-connected switch and the inverter side switch, between the grid side switch and the grid, between the load side switch and the load, and between the grid side switch, the inverter side switch, and the load side switch. The two switches are arranged in the inverter, one end of the two switches is connected to the ground line, and the other end of the two switches is connected to the neutral line between the inverter circuit and the grid-connected switch, or the other end of the two switches is connected to the neutral line between the grid-connected switch and the inverter side switch. Or, two switches are arranged in the grid-connected and off-grid controller, one end of the two switches is connected to the ground wire, and the other end of the two switches is connected to the neutral wire between the inverter-side switch and the grid-connected switch, or, the other end of the two switches is connected to the neutral wire between the load-side switch and the load, or, the other end of the two switches is connected to the neutral wire between the grid-side switch, the inverter-side switch and the load-side switch. The controller is used to perform one or more of the following operations: when the two switches are in the same closed state or open state, a state change instruction is sent to one of the two switches, the state change instruction is a closing instruction or an opening instruction, and if the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported; or, when the two switches are in different closed states or open states, a state change instruction is sent to both switches, and if the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported; or, when the two switches are in different closed states or open states, a closing instruction is sent to one switch, and if the voltage between the neutral line and the ground line is greater than the set voltage value, a disconnection fault is reported.

[0015] The present application provides the above photovoltaic power generation system, when two switches connected in series between the neutral line and the ground line are in the same closed state or disconnected state, the controller sends a state change instruction to one switch, and if the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported; when the two switches are in different closed states or disconnected states, a state change instruction is sent to both switches, and if the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported; when the two switches are in different closed states or disconnected states, a closing instruction is sent to one switch, and if the voltage between the neutral line and the ground line is greater than the set voltage value, a disconnection fault is reported. The above fault detection method checks the switch faults one by one in the dynamic process of switch switching, and can complete the fault detection and the switching of the switch closed state or disconnected state in a short time. In addition, the short circuit faults of both switches can be detected, and the fault detection is comprehensive and efficient.

[0016] In some embodiments of the present application, the controller is specifically used to: when both switches are in an open state, send a closing command to one of the two switches, and if the voltage between the neutral line and the ground line is less than a set voltage value, report that the other of the two switches has a short circuit fault; or, when both switches are in a closed state, send an opening command to one of the two switches, and if the voltage between the neutral line and the ground line is less than a set voltage value, report that one of the two switches has a short circuit fault.

[0017] In some embodiments of the present application, the controller is specifically used to: when one of the two switches is in a closed state and the other switch is in an open state, send an opening command to one of the two switches and a closing command to the other switch; if the voltage between the neutral line and the ground line is less than a set voltage value, report that a short circuit fault has occurred in one of the two switches.

[0018] In some embodiments of the present application, the controller is specifically used to: when one of the two switches is in an open state and the other switch is in a closed state, send a closing instruction to one of the two switches, and if the voltage between the neutral line and the ground line is greater than a set voltage value, report a disconnection fault in either of the two switches.

[0019] In some embodiments of the present application, the controller is also used to: when both switches are in an open state, send a closing command to one of the two switches; if the voltage between the neutral line and the ground line is greater than a set voltage value, send an opening command to one of the two switches and send a closing command to the other switch; if the voltage between the neutral line and the ground line is greater than the set voltage value, send a closing command to one of the two switches.

[0020] The switch fault detection method is to check the switch faults one by one in the dynamic process of switch switching, and the detection time is short. The fault detection and the switching of the switch closed state and the open state can be completed in a short time. Moreover, in the process of switching the two switches from the open state to the closed state, the open faults and short-circuit faults of the two switches can be detected, and the fault detection is comprehensive and efficient.

[0021] In some embodiments of the present application, the controller is also used to: when both switches are in a closed state, send a disconnect command to one of the two switches; if the voltage between the neutral line and the ground line is greater than a set voltage value, send a close command to one of the two switches and send a disconnect command to the other switch; if the voltage between the neutral line and the ground line is greater than the set voltage value, send a disconnect command to one of the two switches.

[0022] The switch fault detection method is to check the switch faults one by one in the dynamic process of switch switching, and the detection time is short. The fault detection and the switching of the switch closed state and the open state can be completed in a short time. Moreover, in the process of switching the two switches from the open state to the closed state, the short circuit faults of the two switches can be detected, and the fault detection is comprehensive and efficient.

[0023] In a third aspect, the present application provides a switch detection method for performing one or more of the following operations: when two switches connected in series between a neutral line and a ground line are in the same closed state or open state, sending a state change instruction to one of the two switches, the state change instruction being a closing instruction or an opening instruction, and if the voltage between the neutral line and the ground line is less than a set voltage value, reporting a short circuit fault; or, when the two switches are in different closed states or open states, sending a state change instruction to both switches, and if the voltage between the neutral line and the ground line is less than a set voltage value, reporting a short circuit fault; or, when the two switches are in different closed states or open states, sending a closing instruction to one switch, and if the voltage between the neutral line and the ground line is greater than a set voltage value, reporting a opening fault.

[0024] The switch detection method provided in the third aspect is applicable to the inverter provided in the first aspect and the photovoltaic power generation system provided in the second aspect.

[0025] In some embodiments of the present application, when two switches connected in series between a neutral line and a ground line are in the same closed state or open state, a state change instruction is sent to one of the two switches, the state change instruction is a closing instruction or an opening instruction, and if the voltage between the neutral line and the ground line is less than a set voltage value, a short circuit fault is reported, including: when both switches are in an open state, a closing instruction is sent to one of the two switches, and if the voltage between the neutral line and the ground line is less than a set voltage value, a short circuit fault is reported in the other of the two switches; or, when both switches are in a closed state, a opening instruction is sent to one of the two switches, and if the voltage between the neutral line and the ground line is less than a set voltage value, a short circuit fault is reported in one of the two switches.

[0026] In some embodiments of the present application, when two switches are in different closed states or open states, a state change instruction is sent to both switches, and if the voltage between the neutral line and the ground line is less than a set voltage value, a short circuit fault is reported, including: when one of the two switches is in a closed state and the other switch is in an open state, a disconnect instruction is sent to one of the two switches and a close instruction is sent to the other switch, and if the voltage between the neutral line and the ground line is less than a set voltage value, a short circuit fault is reported in one of the two switches.

[0027] In some embodiments of the present application, it also includes:

[0028] When both switches are in the open state, a closing command is sent to one of the two switches. If the voltage between the neutral line and the ground line is greater than the set voltage value, an opening command is sent to one of the two switches and a closing command is sent to the other switch. If the voltage between the neutral line and the ground line is greater than the set voltage value, a closing command is sent to one of the two switches.

[0029] In some embodiments of the present application, it also includes:

[0030] When both switches are in the closed state, a disconnect command is sent to one of the two switches. If the voltage between the neutral line and the ground line is greater than the set voltage value, a close command is sent to one of the two switches and a disconnect command is sent to the other switch. If the voltage between the neutral line and the ground line is greater than the set voltage value, a disconnect command is sent to one of the two switches. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is the structural diagram of the relay;

[0032] Figure 2 A schematic diagram of the connection structure of the inverter and the switch in the photovoltaic power generation system provided in the embodiment of the present application;

[0033] Figure 3a A schematic diagram of an application scenario of the inverter provided in an embodiment of the present application;

[0034] Figure 3b A schematic diagram of another application scenario of the inverter provided in an embodiment of the present application;

[0035] Figure 4a A schematic diagram of another application scenario of the photovoltaic power generation system provided in an embodiment of the present application;

[0036] Figure 4b A schematic diagram of another application scenario of the photovoltaic power generation system provided in an embodiment of the present application;

[0037] Figure 5 This is a schematic diagram of the process of Embodiment 1;

[0038] Figure 6 This is a schematic diagram of the process of Embodiment 2. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as being limited to the embodiments described herein; on the contrary, these embodiments are provided to make the present application more comprehensive and complete, and to fully convey the concepts of the example embodiments to those skilled in the art. The same figure marks in the figures represent the same or similar structures, and thus their repeated descriptions will be omitted. The words expressing position and direction described in this application are all explained using the accompanying drawings as examples, but changes may be made as needed, and all changes are included in the scope of protection of this application. The drawings of this application are only used to illustrate the relative position relationship and do not represent the true proportions.

[0040] It should be noted that specific details are described in the following description to facilitate a full understanding of the present application. However, the present application can be implemented in a variety of other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific implementation methods disclosed below. The subsequent description of the specification is a preferred implementation method for implementing the present application, but the description is for the purpose of illustrating the general principles of the present application and is not intended to limit the scope of the present application. The scope of protection of the present application shall be determined by the definition of the attached claims.

[0041] In order to facilitate understanding of the embodiments of the present application, the relevant technologies involved in the embodiments of the present application are first introduced below.

[0042] The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to be used as limitations on the present application. As used in the specification and appended claims of the present application, the singular expressions "one", "a kind of" and "the" are intended to also include expressions such as "one or more", unless there is a clear indication to the contrary in the context. It should also be understood that in the following embodiments of the present application, "at least one" refers to one, two or more than two.

[0043] References to "one embodiment" and the like described in this specification mean that a particular feature, structure or characteristic described in conjunction with the embodiment is included in one or more embodiments of the present application. Thus, the phrases "in one embodiment", "in some embodiments", "in other embodiments", etc. that appear at different places in this specification do not necessarily all refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0044] Reference Figure 1The electrical principle of the relay is as follows: 1 and 2 are contact pins, which are set in the circuit that needs to be controlled on and off; 3 and 4 are control pins, which are set in the low-voltage control circuit. When a certain range of control voltage is applied to the control pin, the contact pin is attracted, and when the control voltage is removed from the control pin, the contact pin is disconnected.

[0045] At present, the common method for detecting whether a relay is faulty is to detect the voltage across the contact pins of a single relay, i.e., the contact voltage, when the relay is in a steady state, to determine whether the relay is faulty. If the current desired state of the relay is the energized state, the contact voltage of the relay should be a low voltage close to 0. At this time, if the contact voltage of the relay is detected to be higher than a certain set voltage, it is considered that the relay has a contact open circuit fault. If the current desired state of the relay is the disconnected state, the contact voltage of the relay should be higher than a certain set voltage. At this time, if the contact voltage of the relay is detected to be lower than a certain set voltage, it is considered that the relay has a contact adhesion fault, which can also be called a short circuit fault.

[0046] The above fault detection method can only detect whether a single relay has a fault, and cannot be applied to the scenario where two relays are connected in series. For example, in the scenario where two series relays are set on the AC output side of the photovoltaic system, specifically in the scenario where two relays are connected in series between the neutral line and the ground line to prevent safety problems caused by single-point failures, it is impossible to perform fault detection on the two relays. Moreover, the above fault detection method can only detect one type of fault when the relay is in a certain steady state, and cannot identify two faults. For example, when the relay is in the energized state, it can only detect whether the relay has an open contact fault; when the relay is in the disconnected state, it can only detect whether the relay has a contact adhesion fault.

[0047] The present application provides a method for detecting switch faults for a scenario in which two switches in series are arranged on the AC output side of an inverter and a photovoltaic power generation system, specifically a scenario in which two switches are connected in series between a neutral line and a ground line. The two switches may specifically be two relays, or two contactors, or one relay and one contactor. By applying a specific control timing to the two switches in series and adopting a specific voltage detection logic, the disconnection fault (i.e., contact open circuit fault) and short circuit fault (i.e., contact adhesion fault) detection of the two switches can be realized during the state switching process of the two switches in series, and fault detection can be realized for both switches.

[0048] The system architecture and application scenarios of the inverter and photovoltaic power generation system provided in this application are described in detail below.

[0049] The photovoltaic power generation system provided by the present application includes: a maximum power point voltage (MPPT) circuit, an inverter (INV) circuit and a switch assembly. Among them, the input end of the MPPT circuit is connected to a single or multiple photovoltaic cell assemblies, and the MPPT circuit is used to convert the voltage of the photovoltaic cell assembly into a DC bus voltage output. The function of the MPPT circuit is to track the voltage and current of the photovoltaic cell assembly so that it can generate electricity at maximum power, and secondly, to control the DC bus voltage at the highest efficiency point of the INV circuit. The INV circuit is used to convert the DC bus voltage into an AC output, and the AC power can be connected to the grid for power generation, and the AC power can also be used to supply power to household loads when off-grid. In addition, the MPPT circuit and the INV circuit can exist independently of each other, or they can be combined into one circuit, that is, the MPPT function is realized by using an inverter circuit. The switch assembly can specifically include a grid-connected switch, an off-grid switch, a grid-side switch, an inverter-side switch, a load-side switch, etc. Each switch assembly is composed of one or more groups of switches connected in series, and the types of switches are usually relays and contactors, etc. The above-mentioned switch assembly can be composed of a single type of switch, or it can be composed of a combination of different types of switches.

[0050] Reference Figure 2 , the inverter and photovoltaic power generation system connect two switches in series between the neutral line (N) and the ground line on the AC output side, which are recorded as the first switch K1 and the second switch K2, and the positions of the two switches can be interchanged. The two switches can be two relays, two contactors, or one relay and one contactor. The controller can control the on-off state of the first switch K1 and the second switch K2 to meet the on-off requirements of the neutral line and the ground line in different scenarios. Specifically, in order to ensure the safety of electricity use, when the photovoltaic system is off-grid, the neutral line and the ground line of the inverter and the photovoltaic power generation system need to be connected, that is, the controller needs to control the first switch K1 and the second switch K2 to switch from the open state to the closed state; when the photovoltaic system is on-grid, the neutral line and the ground line of the inverter and the photovoltaic power generation system need to be disconnected, that is, the controller needs to control the first switch K1 and the second switch K2 to switch from the closed state to the open state. In the inverter and photovoltaic power generation system, the ground line (PE) is the grounding point of the equipment. In actual application, the ground wire can be connected to the device housing through a cable, and the housing is connected to the PE bar of the distribution box. Alternatively, the ground wire can be directly connected to the PE bar of the distribution box through a separate cable. The neutral line can be located at different positions in the inverter and photovoltaic power generation system, which is explained in detail below through different scenarios.

[0051] Reference Figure 3aThe inverter provided in the embodiment of the present application can be a three-phase inverter with an off-grid port, and the three-phase inverter includes: an MPPT circuit, an INV circuit, an off-grid switch and a grid-connected switch. Among them, the input end of the MPPT circuit is connected to the photovoltaic cell assembly, the output end of the MPPT circuit is connected to the DC bus, the input end of the INV circuit is connected to the DC bus, the output end of the INV circuit is a three-phase output port, the INV circuit is connected to the off-grid port through the off-grid switch, and the INV circuit is connected to the grid-connected port through the grid-connected switch at the same time. The off-grid port is used to connect the household load, and the grid-connected port is used to connect the power grid. The neutral line is set between the INV circuit and the load, the off-grid switch is set on the neutral line, one end of the two switches K1 and K2 is connected to the grounding line PE, and the other end of the two switches K1 and K2 can be connected to the neutral line between the INV circuit and the off-grid switch, that is, the N position, or, the other end of the two switches K1 and K2 can also be connected to the neutral line between the off-grid switch and the load, that is, the N1 position. Figure 3a Only two switches K1 and K2 are shown as being set in the N position.

[0052] Reference Figure 3b The inverter provided in the embodiment of the present application may also be a single-phase inverter with an off-grid port, and the single-phase inverter includes: an MPPT circuit, an INV circuit, an off-grid switch and a grid-connected switch. Among them, the input end of the MPPT circuit is connected to the photovoltaic cell assembly, the output end of the MPPT circuit is connected to the DC bus, the input end of the INV circuit is connected to the DC bus, the output end of the INV circuit is a single-phase output port, the INV circuit is connected to the off-grid port through the off-grid switch, and the INV circuit is connected to the grid-connected port through the grid-connected switch at the same time. The off-grid port is used to connect the household load, and the grid-connected port is used to connect the power grid. The neutral line is set between the INV circuit and the load, the off-grid switch is set on the neutral line, one end of the two switches K1 and K2 is connected to the grounding line PE, and the other end of the two switches K1 and K2 can be connected to the neutral line between the INV circuit and the off-grid switch, that is, the N position, or, the other end of the two switches K1 and K2 can also be connected to the neutral line between the off-grid switch and the load, that is, the N1 position. Figure 3b Only two switches K1 and K2 are shown as being set in the N position.

[0053] Reference Figure 4aThe photovoltaic power generation system provided in the embodiment of the present application may include: a three-phase inverter without an off-grid port and an on-grid switching device, and the on-grid switching device is independent of the three-phase inverter and is used to realize the off-grid function. The three-phase inverter includes: an MPPT circuit, an INV circuit and a grid-connected switch. Among them, the input end of the MPPT circuit is connected to the photovoltaic cell assembly, the output end of the MPPT circuit is connected to the DC bus, the input end of the INV circuit is connected to the DC bus, the output end of the INV circuit is a three-phase output port, and the INV circuit is connected to the inverter port of the on-grid switching device through the grid-connected switch. The on-grid switching device includes: an inverter side switch, a grid side switch and a load side switch that are interconnected. Among them, the inverter side switch is connected to the inverter port, the grid side switch is connected to the grid-connected port, and the load side switch is connected to the off-grid port. The off-grid port is used to connect a household load, and the grid-connected port is used to connect to the grid. The neutral line is set between: the INV circuit and the grid-connected switch, between the grid-connected switch and the inverter-side switch, between the grid-side switch and the grid, between the load-side switch and the load, and between the grid-side switch, the inverter-side switch and the load-side switch. The two switches K1 and K2 can be set in the inverter, one end of the two switches K1 and K2 is connected to the ground line PE, and the other end of the two switches K1 and K2 is connected to the neutral line between the INV circuit and the grid-connected switch, that is, the N position, or the other end of the two switches K1 and K2 is connected to the neutral line between the grid-connected switch and the inverter-side switch, that is, the N1 position. The two switches K1 and K2 can also be arranged in the grid-connected and off-grid controller, one end of the two switches K1 and K2 is connected to the ground wire PE, and the other end of the two switches K1 and K2 is connected to the neutral line between the inverter side switch and the grid-connected switch, that is, the N2 position, or the other end of the two switches K1 and K2 is connected to the neutral line between the load side switch and the load, that is, the N4 position, or the other end of the two switches K1 and K2 is connected to the neutral line between the grid side switch, the inverter side switch and the load side switch, that is, the N3 position. Figure 4a Only two switches K1 and K2 are shown as being set in the N position.

[0054] Reference Figure 4bThe photovoltaic power generation system provided in the embodiment of the present application may include: a single-phase inverter without an off-grid port and an on-grid switching device, and the on-grid switching device is independent of the single-phase inverter and is used to realize the off-grid function. The single-phase inverter includes: an MPPT circuit, an INV circuit and a grid-connected switch. Among them, the input end of the MPPT circuit is connected to the photovoltaic cell assembly, the output end of the MPPT circuit is connected to the DC bus, the input end of the INV circuit is connected to the DC bus, the output end of the INV circuit is a single-phase output port, and the INV circuit is connected to the inverter port of the on-grid switching device through the grid-connected switch. The on-grid switching device includes: an inverter side switch, a grid side switch and a load side switch that are interconnected. Among them, the inverter side switch is connected to the inverter port, the grid side switch is connected to the grid-connected port, and the load side switch is connected to the off-grid port. The off-grid port is used to connect a household load, and the grid-connected port is used to connect to the grid. The neutral line is set between: the INV circuit and the grid-connected switch, between the grid-connected switch and the inverter-side switch, between the grid-side switch and the grid, between the load-side switch and the load, and between the grid-side switch, the inverter-side switch and the load-side switch. The two switches K1 and K2 can be set in the inverter, one end of the two switches K1 and K2 is connected to the ground line PE, and the other end of the two switches K1 and K2 is connected to the neutral line between the INV circuit and the grid-connected switch, that is, the N position, or the other end of the two switches K1 and K2 is connected to the neutral line between the grid-connected switch and the inverter-side switch, that is, the N1 position. The two switches K1 and K2 can also be arranged in the grid-connected and off-grid controller, one end of the two switches K1 and K2 is connected to the ground wire PE, and the other end of the two switches K1 and K2 is connected to the neutral line between the inverter side switch and the grid-connected switch, that is, the N2 position, or the other end of the two switches K1 and K2 is connected to the neutral line between the load side switch and the load, that is, the N4 position, or the other end of the two switches K1 and K2 is connected to the neutral line between the grid side switch, the inverter side switch and the load side switch, that is, the N3 position. Figure 4a Only two switches K1 and K2 are shown as being set in the N position.

[0055] In the present application, the controller can detect the fault of the switch during the process of dynamically switching the closed state and the open state of the two switches when it is necessary to switch the conduction state and the open state between the neutral line and the ground line. When the neutral line and the ground line are in the initial state, the two switches are in the same closed state or open state. At this time, the controller can send a state change instruction to one of the two switches, and the state change instruction is a closing instruction or a disconnecting instruction. After changing the on-off state of one switch, it is determined whether the voltage between the neutral line and the ground line is less than the set voltage value. If the voltage between the neutral line and the ground line is less than the set voltage value, it means that one of the two switches has a short circuit fault, and the short circuit fault is reported. Specifically, when the initial state between the neutral line and the ground line is the disconnected state, the initial states of the two switches are both in the disconnected state, and a closing instruction is sent to one of the two switches to determine whether the voltage between the neutral line and the ground line is less than the set voltage value. If the voltage between the neutral line and the ground line is less than the set voltage value, it means that the other switch of the two switches has a short circuit fault, and the short circuit fault is reported. When the initial state between the neutral line and the ground line is the connection state, the initial state of the two switches is in the closed state, and a disconnection command is sent to one of the two switches to determine whether the voltage between the neutral line and the ground line is less than the set voltage value. If the voltage between the neutral line and the ground line is less than the set voltage value, it means that one of the two switches has a short circuit fault, and a short circuit fault is reported in one of the two switches.

[0056] After the controller sends a state change instruction to one of the two switches for the first time to change the closed state or open state of one switch, and determines that the voltage between the neutral line and the ground line is greater than the set voltage value, it means that one of the two switches has not had a short circuit fault, and at this time, the two switches are in different closed states or open states. Afterwards, the controller can send a state change instruction to both switches, and after changing the closed state or open state of the two switches, determine whether the voltage between the neutral line and the ground line is less than the set voltage value. If the voltage between the neutral line and the ground line is less than the set voltage value, it means that the other of the two switches has a short circuit fault, and report the occurrence of a short circuit fault. Specifically, when one of the two switches is in a closed state and the other switch is in an open state, the controller sends an open instruction to one of the two switches and a close instruction to the other switch, and determines whether the voltage between the neutral line and the ground line is less than the set voltage value. If the voltage between the neutral line and the ground line is less than the set voltage value, it means that one of the two switches has a short circuit fault, and report the occurrence of a short circuit fault in one of the two switches.

[0057] After the controller changes the closed state or open state of the two switches for the first time at the same time, and determines that the voltage between the neutral line and the ground line is greater than the set voltage value, it means that the other switch of the two switches has not had a short circuit fault. At this time, the two switches are in different closed states or open states, that is, one switch is in an open state and the other switch is in a closed state. After that, the controller can send a closing instruction to one of the two switches to determine whether the voltage between the neutral line and the ground line is greater than the set voltage value. If the voltage between the neutral line and the ground line is less than the set voltage value, it means that any one of the two switches has a disconnection fault, and a disconnection fault is reported in any one of the two switches; if the voltage between the neutral line and the ground line is greater than the set voltage value, it means that the two switches have not had a disconnection fault, and the process of switching the two switches from the open state to the closed state is completed, so that the neutral line and the ground line are switched to the connected state.

[0058] Alternatively, after the controller changes the closed state or open state of the two switches for the first time at the same time, and determines that the voltage between the neutral line and the ground line is greater than the set voltage value, it means that the other switch of the two switches has not had a short circuit fault. At this time, the two switches are in different closed states or open states, that is, one switch is in the open state and the other switch is in the closed state. After that, the controller can send a disconnect instruction to one of the two switches, completing the process of switching the two switches from the closed state to the open state, so that the neutral line and the ground line are switched to the open state.

[0059] The switch fault detection method provided by the present application is to check the switch faults one by one in the dynamic process of switch switching. The detection time is short, and the fault detection and the switching of the switch closed state and the open state can be completed within 1s. In addition, in the process of switching the two switches from the open state to the closed state, the short-circuit faults of the two switches can be detected, and the fault detection is comprehensive and efficient. In the process of switching the two switches from the open state to the closed state, the short-circuit faults of the two switches can be detected, and the fault detection is comprehensive and efficient.

[0060] Based on the same inventive concept, the embodiment of the present application also provides a switch detection method, comprising the following steps:

[0061] When the neutral line and the ground line are in the initial state, the two switches connected in series between the neutral line and the ground line are in the same closed state or open state. At this time, a state change instruction can be sent to one of the two switches, and the state change instruction is a closing instruction or an opening instruction. After changing the closed state or the open state of one switch, it is determined whether the voltage between the neutral line and the ground line is less than the set voltage value. If the voltage between the neutral line and the ground line is less than the set voltage value, it means that one of the two switches has a short circuit fault, and the short circuit fault is reported. Specifically, when the initial state between the neutral line and the ground line is the open state, the initial states of the two switches are both in the open state, and a closing instruction is sent to one of the two switches to determine whether the voltage between the neutral line and the ground line is less than the set voltage value. If the voltage between the neutral line and the ground line is less than the set voltage value, it means that the other switch of the two switches has a short circuit fault, and the other switch of the two switches has a short circuit fault. When the initial state between the neutral line and the ground line is the connection state, the initial state of the two switches is in the closed state, and a disconnection command is sent to one of the two switches to determine whether the voltage between the neutral line and the ground line is less than the set voltage value. If the voltage between the neutral line and the ground line is less than the set voltage value, it means that one of the two switches has a short circuit fault, and a short circuit fault is reported in one of the two switches.

[0062] After sending a state change instruction to one of the two switches for the first time to change the closed state or open state of one switch, and judging that the voltage between the neutral line and the ground line is greater than the set voltage value, it means that one of the two switches has not had a short circuit fault, and at this time, the two switches are in different closed states or open states. Afterwards, a state change instruction can be sent to both switches, and after changing the closed state or open state of the two switches, it is judged whether the voltage between the neutral line and the ground line is less than the set voltage value. If the voltage between the neutral line and the ground line is less than the set voltage value, it means that the other of the two switches has a short circuit fault, and the short circuit fault is reported. Specifically, when one of the two switches is in a closed state and the other switch is in an open state, a disconnect instruction is sent to one of the two switches and a close instruction is sent to the other switch, and it is judged whether the voltage between the neutral line and the ground line is less than the set voltage value. If the voltage between the neutral line and the ground line is less than the set voltage value, it means that one of the two switches has a short circuit fault, and the short circuit fault is reported.

[0063] After the closed state or open state of the two switches is changed at the same time for the first time, and it is determined that the voltage between the neutral line and the grounding line is greater than the set voltage value, it means that the other switch of the two switches has not had a short circuit fault. At this time, the two switches are in different closed states or open states, that is, one switch is in an open state and the other switch is in a closed state. Afterwards, a closing instruction can be sent to one of the two switches to determine whether the voltage between the neutral line and the grounding line is greater than the set voltage value. If the voltage between the neutral line and the grounding line is less than the set voltage value, it means that any one of the two switches has a disconnection fault, and a disconnection fault of any one of the two switches is reported; if the voltage between the neutral line and the grounding line is greater than the set voltage value, it means that the two switches have not had a disconnection fault, and the two switches are switched to a closed state, so that the neutral line and the grounding line are switched to a connected state.

[0064] Alternatively, after the closed state or open state of the two switches is changed simultaneously for the first time, and it is determined that the voltage between the neutral line and the ground line is greater than the set voltage value, it means that the other switch of the two switches has not had a short circuit fault. At this time, the two switches are in different closed states or open states, that is, one switch is in the open state and the other switch is in the closed state. After that, a disconnection instruction can be sent to one of the two switches to complete the switching of the two switches to the open state, so that the neutral line and the ground line are switched to the open state.

[0065] The present application provides the above-mentioned inverter, photovoltaic power generation system and switch detection method. When two switches connected in series between the neutral line and the ground line are in the same closed state or disconnected state, a state change instruction is sent to one switch. If the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported; when the two switches are in different closed states or disconnected states, a state change instruction is sent to both switches. If the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported; when the two switches are in different closed states or disconnected states, a closing instruction is sent to one switch. If the voltage between the neutral line and the ground line is greater than the set voltage value, a disconnection fault is reported. The above-mentioned fault detection method checks the switch faults one by one in the dynamic process of switch switching, and can complete the fault detection and the switching of the switch closed state or disconnected state in a short time. In addition, the short circuit faults of both switches can be detected, and the fault detection is comprehensive and efficient.

[0066] Below Figure 2 Taking the example of connecting the first switch K1 and the second switch K2 in series between the neutral line and the grounding line, the dynamic switching process and fault detection method of the two switches during the switching process between the closed state or the open state between the neutral line and the grounding line are described in detail through specific embodiments.

[0067] Embodiment 1:

[0068] Reference Figure 5 When the neutral line and the ground line are switched from disconnected state to connected state, the controller performs the following steps:

[0069] S51, the initial states of the first switch K1 and the second switch K2 are both in the disconnected state, so that the neutral line and the grounding line are in the disconnected state. At this time, the voltage between the neutral line and the grounding line (NPE voltage) is greater than the set voltage value, which may be 50V, for example.

[0070] S52: Send a closing instruction to the first switch K1. After a delay of a set time, such as 50 ms, it can be considered that the first switch K1 is completely switched from the open state to the closed state.

[0071] S53, determine whether the voltage between the neutral line and the ground line (NPE voltage) is less than the set voltage value. If yes, it means that the second switch K2 has a short circuit fault, and the short circuit fault needs to be reported, and the inverter circuit can be further controlled to shut down; if no, it means that the second switch K2 has no short circuit fault.

[0072] S54, sending an opening instruction to the first switch K1, and sending a closing instruction to the second switch K2. After a delay of a set time, such as 50ms, it can be considered that the first switch K1 is completely switched from the closed state to the open state, and the second switch K2 is completely switched from the open state to the closed state.

[0073] S55, determine whether the voltage between the neutral line and the ground line (NPE voltage) is less than the set voltage value. If yes, it means that the first switch K1 has a short circuit fault, and the short circuit fault needs to be reported, and the inverter circuit can be further controlled to shut down; if no, it means that the first switch K1 has no short circuit fault.

[0074] S56: Send a closing instruction to the first switch K1. After a delay of a set time, such as 50 ms, it can be considered that the first switch K1 is completely switched from the open state to the closed state.

[0075] S57, determine whether the voltage between the neutral line and the ground line (NPE voltage) is greater than the set voltage value. If so, it means that the first switch K1 or the second switch K2 has a disconnection fault, and the disconnection fault needs to be reported, and the inverter circuit can be further controlled to shut down; if not, it means that neither the first switch K1 nor the second switch K2 has a disconnection fault, and the first switch K1 and the second switch K2 have been switched to a closed state, so that the neutral line and the ground line are switched to a connected state.

[0076] The switch fault detection method is to check the switch faults one by one in the dynamic process of switch switching, and the detection time is short. The fault detection and the switching of the switch closed state and the open state can be completed within 1 second. Moreover, in the process of switching the two switches from the open state to the closed state, the open faults and short-circuit faults of the two switches can be detected, and the fault detection is comprehensive and efficient.

[0077] Embodiment 2:

[0078] Reference Figure 6 When the neutral line and the ground line are switched from the connected state to the disconnected state, the controller performs the following steps:

[0079] S61, the initial states of the first switch K1 and the second switch K2 are both in a closed state, so that the neutral line and the ground line are in a connected state. At this time, the voltage between the neutral line and the ground line (NPE voltage) is less than the set voltage value, which may be 50V, for example.

[0080] S62: Send an opening instruction to the second switch K2. After a delay of a set time, such as 50 ms, it can be considered that the second switch K2 is completely switched from the closed state to the open state.

[0081] S63, determine whether the voltage between the neutral line and the ground line (NPE voltage) is less than the set voltage value. If yes, it means that the second switch K2 has a short circuit fault, and the short circuit fault needs to be reported, and the inverter circuit can be further controlled to shut down; if no, it means that the second switch K2 has no short circuit fault.

[0082] S64, sending an opening instruction to the first switch K1, and sending a closing instruction to the second switch K2. After a delay of a set time, such as 50ms, it can be considered that the first switch K1 is completely switched from the closed state to the open state, and the second switch K2 is completely switched from the open state to the closed state.

[0083] S65, determine whether the voltage between the neutral line and the ground line (NPE voltage) is less than the set voltage value. If yes, it means that the first switch K1 has a short circuit fault, and the short circuit fault needs to be reported, and the inverter circuit can be further controlled to shut down; if no, it means that the first switch K1 has no short circuit fault.

[0084] S66, sending a disconnection instruction to the second switch K2. After a delay of a set time, such as 50ms, it can be considered that the second switch K2 is completely switched from the closed state to the open state, completing the switching of the first switch K1 and the second switch K2 to the open state, so that the neutral line and the grounding line are switched to the open state.

[0085] The switch fault detection method is to check the switch faults one by one in the dynamic process of switch switching, and the detection time is short. The fault detection and the switching of the switch closed state and the open state can be completed within 1 second. Moreover, in the process of switching the two switches from the open state to the closed state, the short circuit faults of the two switches can be detected, and the fault detection is comprehensive and efficient.

[0086] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. An inverter, characterized in that: include: An inverter circuit, an off-grid switch, a neutral line, a ground line, two switches connected in series, and a controller; wherein the neutral line is arranged between the inverter circuit and the load, and the off-grid switch is arranged on the neutral line; One end of the two switches is connected to the ground line, and the other end of the two switches is connected to the neutral line between the inverter circuit and the off-grid switch, or the other end of the two switches is connected to the neutral line between the off-grid switch and the load; The controller is used to perform one or more of the following operations: When the two switches are in the same closed state or open state, a state change instruction is sent to one of the two switches, wherein the state change instruction is a closing instruction or an opening instruction, and if the voltage between the neutral line and the grounding line is less than a set voltage value, a short circuit fault is reported; or, When the two switches are in different closed states or open states, a state change instruction is sent to both switches, and if the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported; or, When the two switches are in different closed states or open states, a closing instruction is sent to one switch, and if the voltage between the neutral line and the grounding line is greater than the set voltage value, a disconnection fault is reported.

2. The inverter according to claim 1, characterized in that: The controller is specifically used for: When both switches are in an open state, a closing instruction is sent to one of the two switches, and if the voltage between the neutral line and the ground line is less than a set voltage value, a short circuit fault is reported to the other of the two switches; or, When the two switches are both in a closed state, a disconnection instruction is sent to one of the two switches, and if the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported in one of the two switches.

3. The inverter according to claim 1 or 2, characterized in that: The controller is specifically used for: When one of the two switches is in a closed state and the other switch is in an open state, an opening instruction is sent to one of the two switches and a closing instruction is sent to the other switch. If the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported in one of the two switches.

4. The inverter according to any one of claims 1 to 3, characterized in that: The controller is also used for: When both switches are in an open state, a closing command is sent to one of the two switches. If the voltage between the neutral line and the ground line is greater than a set voltage value, an opening command is sent to one of the two switches and a closing command is sent to the other switch. If the voltage between the neutral line and the ground line is greater than a set voltage value, a closing command is sent to one of the two switches.

5. The inverter according to any one of claims 1 to 4, characterized in that: The controller is also used for: When both switches are in a closed state, a disconnect command is sent to one of the two switches. If the voltage between the neutral line and the ground line is greater than a set voltage value, a close command is sent to one of the two switches and a disconnect command is sent to the other switch. If the voltage between the neutral line and the ground line is greater than a set voltage value, a disconnect command is sent to one of the two switches.

6. A photovoltaic power generation system, characterized in that: include: An inverter, an on-grid and off-grid switching device, a neutral line, a ground line, two switches arranged in series, and a controller; wherein the inverter comprises: an inverter circuit and a grid-connected switch, the on-grid and off-grid switching device comprises: an inverter-side switch, a grid-side switch, and a load-side switch connected to each other, and the grid-connected switch is connected to the inverter-side switch; The neutral line is arranged between: the inverter circuit and the grid-connected switch, between the grid-connected switch and the inverter-side switch, between the grid-side switch and the grid, between the load-side switch and the load, and between the grid-side switch, the inverter-side switch and the load-side switch; The two switches are arranged in the inverter, one end of the two switches is connected to the ground line, and the other end of the two switches is connected to the neutral line between the inverter circuit and the grid-connected switch, or the other end of the two switches is connected to the neutral line between the grid-connected switch and the inverter-side switch; Or, the two switches are arranged in the grid-connected and off-grid controller, one end of the two switches is connected to the ground line, and the other end of the two switches is connected to the neutral line between the inverter-side switch and the grid-connected switch, or, the other end of the two switches is connected to the neutral line between the load-side switch and the load, or, the other end of the two switches is connected to the neutral line between the grid-side switch, the inverter-side switch and the load-side switch; The controller is used to perform one or more of the following operations: When the two switches are in the same closed state or open state, a state change instruction is sent to one of the two switches, wherein the state change instruction is a closing instruction or an opening instruction, and if the voltage between the neutral line and the grounding line is less than a set voltage value, a short circuit fault is reported; or, When the two switches are in different closed states or open states, a state change instruction is sent to both switches, and if the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported; or, When the two switches are in different closed states or open states, a closing instruction is sent to one switch, and if the voltage between the neutral line and the grounding line is greater than the set voltage value, a disconnection fault is reported.

7. The photovoltaic power generation system according to claim 6, characterized in that: The controller is specifically used for: When both switches are in an open state, a closing instruction is sent to one of the two switches, and if the voltage between the neutral line and the ground line is less than a set voltage value, a short circuit fault is reported to the other of the two switches; or, When the two switches are both in a closed state, a disconnection instruction is sent to one of the two switches, and if the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported in one of the two switches.

8. The photovoltaic power generation system according to claim 6 or 7, characterized in that: The controller is specifically used for: When one of the two switches is in a closed state and the other switch is in an open state, an opening instruction is sent to one of the two switches and a closing instruction is sent to the other switch. If the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported in one of the two switches.

9. The photovoltaic power generation system according to any one of claims 6 to 8, characterized in that: The controller is also used for: When both switches are in an open state, a closing command is sent to one of the two switches. If the voltage between the neutral line and the ground line is greater than a set voltage value, an opening command is sent to one of the two switches and a closing command is sent to the other switch. If the voltage between the neutral line and the ground line is greater than a set voltage value, a closing command is sent to one of the two switches.

10. The photovoltaic power generation system according to any one of claims 6 to 9, characterized in that: The controller is also used for: When both switches are in a closed state, a disconnect command is sent to one of the two switches. If the voltage between the neutral line and the ground line is greater than a set voltage value, a close command is sent to one of the two switches and a disconnect command is sent to the other switch. If the voltage between the neutral line and the ground line is greater than a set voltage value, a disconnect command is sent to one of the two switches.

11. A switch detection method, characterized in that: Used to perform one or more of the following operations: When two switches connected in series between the neutral line and the ground line are in the same closed state or open state, a state change instruction is sent to one of the two switches, wherein the state change instruction is a closing instruction or an opening instruction, and if the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported; or, When the two switches are in different closed states or open states, a state change instruction is sent to both switches, and if the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported; or, When the two switches are in different closed states or open states, a closing instruction is sent to one switch, and if the voltage between the neutral line and the ground line is greater than the set voltage value, a disconnection fault is reported; The inverter includes: an inverter circuit and a grid-connected switch, and the grid-connected and off-grid switching device includes: an inverter-side switch, a grid-side switch and a load-side switch connected to each other, and the grid-connected switch is connected to the inverter-side switch; The neutral line is arranged between: the inverter circuit and the grid-connected switch, between the grid-connected switch and the inverter-side switch, between the grid-side switch and the grid, between the load-side switch and the load, and between the grid-side switch, the inverter-side switch and the load-side switch; The two switches are arranged in the inverter, one end of the two switches is connected to the ground line, and the other end of the two switches is connected to the neutral line between the inverter circuit and the grid-connected switch, or the other end of the two switches is connected to the neutral line between the grid-connected switch and the inverter-side switch; Or, the two switches are arranged in the grid-connected and off-grid controller, one end of the two switches is connected to the ground line, and the other end of the two switches is connected to the neutral line between the inverter-side switch and the grid-connected switch, or, the other end of the two switches is connected to the neutral line between the load-side switch and the load, or, the other end of the two switches is connected to the neutral line between the grid-side switch, the inverter-side switch and the load-side switch.

12. The switch detection method according to claim 11, characterized in that: When two switches connected in series between a neutral line and a ground line are in the same closed state or open state, a state change instruction is sent to one of the two switches, wherein the state change instruction is a closing instruction or an opening instruction, and if the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported, including: When both switches are in an open state, a closing instruction is sent to one of the two switches, and if the voltage between the neutral line and the ground line is less than a set voltage value, a short circuit fault is reported to the other of the two switches; or, When the two switches are both in a closed state, a disconnection instruction is sent to one of the two switches, and if the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported in one of the two switches.

13. The switch detection method according to claim 11 or 12, characterized in that: When the two switches are in different closed states or open states, a state change instruction is sent to both switches, and if the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported, including: When one of the two switches is in a closed state and the other switch is in an open state, an opening instruction is sent to one of the two switches and a closing instruction is sent to the other switch. If the voltage between the neutral line and the ground line is less than the set voltage value, a short circuit fault is reported in one of the two switches.

14. The switch detection method according to any one of claims 11 to 13, characterized in that: Also includes: When both switches are in an open state, a closing command is sent to one of the two switches. If the voltage between the neutral line and the ground line is greater than a set voltage value, an opening command is sent to one of the two switches and a closing command is sent to the other switch. If the voltage between the neutral line and the ground line is greater than a set voltage value, a closing command is sent to one of the two switches.

15. The switch detection method according to any one of claims 11 to 14, characterized in that: Also includes: When both switches are in a closed state, a disconnect command is sent to one of the two switches. If the voltage between the neutral line and the ground line is greater than a set voltage value, a close command is sent to one of the two switches and a disconnect command is sent to the other switch. If the voltage between the neutral line and the ground line is greater than a set voltage value, a disconnect command is sent to one of the two switches.

Images