Grid-connected relay fault detection method, inverter and energy storage system

Abstract

The invention relates to the field of grid-connected relay detection, and discloses a grid-connected relay fault detection method, an inverter and an energy storage system, the grid-connected relay fault detection method is applied to the inverter, the inverter comprises a to-be-detected grid-connected relay group, and the method comprises the following steps: responding to a preset zero line relay fault detection instruction; first voltage information of the to-be-detected grid-connected relay set in a first turn-off state is obtained, and the first turn-off state comprises single-phase live wire conduction of the to-be-detected grid-connected relay set and zero wire conduction of the to-be-detected grid-connected relay set; second voltage information of the to-be-detected grid-connected relay set in a second turn-off state is obtained, fault detection is carried out on the to-be-detected grid-connected relay set according to the first voltage information and the second voltage information, the second turn-off state comprises that a single-phase live wire of the to-be-detected grid-connected relay set is switched on, and the single-phase live wire of the to-be-detected grid-connected relay set is switched off. And a null line relay on the to-be-detected grid-connected relay group is disconnected. According to the invention, the reliability of fault detection of the grid-connected relay is improved.

Description

Technical Field

[0001] The present invention relates to the field of grid-connected relay detection, and in particular to a grid-connected relay fault detection method, an inverter, and an energy storage system. Background Art

[0002] With the rapid development of grid-connected relays, grid-connected relay failures (generally grid-connected relay adhesion and short circuit) are becoming more and more frequent, which also makes users put forward higher requirements for grid-connected relay fault detection.

[0003] Traditional grid-connected relay fault detection methods use sampling resistors to sample signals from both sides of the relay, then determine whether the relay is short-circuited based on the sampled signals. This method has significant drawbacks. Because the neutral line lacks a standard sampling reference signal, it is unable to accurately detect a neutral line short circuit. This inability to accurately detect a neutral line short circuit results in low reliability for grid-connected relay fault detection. Summary of the Invention

[0004] The main purpose of the present invention is to propose a grid-connected relay fault detection method, an inverter and an energy storage system, aiming to solve the technical problem of how to improve the reliability of grid-connected relay fault detection.

[0005] To achieve the above object, the present invention provides a method for detecting a grid-connected relay fault. The method is applied to an inverter, wherein the inverter includes a grid-connected relay group to be detected. The method comprises the following steps:

[0006] In response to a preset neutral line relay fault detection instruction, obtaining first voltage information of the grid-connected relay group to be detected in a first off-state, wherein the first off-state includes a single-phase live wire of the grid-connected relay group to be detected being conductive and a neutral wire of the grid-connected relay group to be detected being conductive;

[0007] Obtain second voltage information of the grid-connected relay group to be detected in the second off-state, and perform fault detection on the grid-connected relay group to be detected based on the first voltage information and the second voltage information, wherein the second off-state includes that the single-phase live wire of the grid-connected relay group to be detected is turned on, and the neutral wire relay on the grid-connected relay group to be detected is disconnected.

[0008] Optionally, the step of performing fault detection on the to-be-detected grid-connected relay group according to the first voltage information and the second voltage information includes:

[0009] detecting whether there is a waveform change between a voltage waveform of the first voltage information and a voltage waveform of the second voltage information;

[0010] If there is a waveform change between the voltage waveform of the first voltage information and the voltage waveform of the second voltage information, determining that the neutral line relay of the grid-connected relay group to be detected is in a normal state;

[0011] If there is no waveform change between the voltage waveform of the first voltage information and the voltage waveform of the second voltage information, it is determined that the neutral line relay of the to-be-detected grid-connected relay group is in a sticking state.

[0012] Optionally, the inverter includes a first voltage detection unit provided on an output side of the grid-connected relay group to be detected, and the step of obtaining first voltage information of the grid-connected relay group to be detected in a first off state in response to a preset neutral line relay fault detection instruction includes:

[0013] In response to a preset neutral line relay fault detection instruction, obtaining a single-phase voltage collected by the first voltage detection unit of the grid-connected relay group to be detected in a first off state, and detecting whether the single-phase voltage is a preset input phase voltage;

[0014] If the single-phase phase voltage is the preset input phase voltage, performing the step of obtaining the second voltage information of the to-be-detected grid-connected relay group in the second off state;

[0015] If the single-phase voltage is not the preset input phase voltage, it is determined that the neutral line relay of the grid-connected relay group to be detected has a hardware control fault.

[0016] Optionally, the inverter includes a first voltage detection unit provided on the output side and a second voltage detection unit provided on the input side of the grid-connected relay group to be detected. Before the step of obtaining first voltage information of the grid-connected relay group to be detected in the first off state in response to a preset neutral line relay fault detection instruction, the grid-connected relay fault detection method further includes:

[0017] In response to a preset live wire relay fault detection instruction, obtaining the output three-phase phase voltage collected by the first voltage detection unit and the input three-phase phase voltage collected by the second voltage detection unit of the grid-connected relay group to be detected in a third off-state, wherein the third off-state includes the three-phase live wires of the grid-connected relay group to be detected being disconnected;

[0018] Determine the live wire relay fault information of the grid-connected relay group to be detected based on the output three-phase phase voltage and the input three-phase phase voltage, and after determining the live wire relay fault information, execute the step of obtaining the first voltage information of the grid-connected relay group to be detected in the first off state in response to a preset neutral wire relay fault detection instruction.

[0019] Optionally, the live wire relay fault information includes first relay fault information, second relay fault information, and third relay fault information, and the step of determining the live wire relay fault information of the to-be-detected grid-connected relay group according to the output three-phase voltage and the input three-phase voltage includes:

[0020] determining an output first phase voltage among the output three-phase voltages and an input first phase voltage among the input three-phase voltages, and determining that the first relay fault information is in a normal state when the output first phase voltage is not equal to the input first phase voltage;

[0021] When the output first phase voltage is equal to the input first phase voltage, determining that the first relay fault information is in a sticking state;

[0022] determining an output second-phase voltage among the output three-phase voltages and an input second-phase voltage among the input three-phase voltages, and determining that the second relay fault information is in a normal state when the output second-phase voltage is not equal to the input second-phase voltage;

[0023] When the output second-phase voltage is equal to the input second-phase voltage, determining that the second relay fault information is in a sticking state;

[0024] determining an output third-phase voltage among the output three-phase voltages and an input third-phase voltage among the input three-phase voltages, and determining that the third relay fault information is in a normal state when the output third-phase voltage is not equal to the input third-phase voltage;

[0025] When the output third-phase voltage is equal to the input third-phase voltage, it is determined that the third relay fault information is in a sticking state.

[0026] Optionally, the inverter includes a first voltage detection unit provided on the output side and a second voltage detection unit provided on the input side of the grid-connected relay group to be detected. Before the step of obtaining first voltage information of the grid-connected relay group to be detected in the first off state in response to a preset neutral line relay fault detection instruction, the grid-connected relay fault detection method further includes:

[0027] In response to a preset live wire relay fault detection instruction, sequentially acquiring an output single-phase voltage collected by the first voltage detection unit and an input single-phase voltage collected by the second voltage detection unit of a target phase of the grid-connected relay group to be detected in a fourth off-state, wherein the fourth off-state includes the live wire relay on the target phase being disconnected;

[0028] Determine the live wire relay fault information of the grid-connected relay group to be detected based on the output single-phase phase voltage and the input single-phase phase voltage, and after determining the live wire relay fault information, execute the step of obtaining the first voltage information of the grid-connected relay group to be detected in the first off state in response to a preset neutral wire relay fault detection instruction.

[0029] Optionally, the step of determining the live wire relay fault information of the to-be-detected grid-connected relay group according to the output single-phase voltage and the input single-phase voltage includes:

[0030] When the output single-phase voltage is not equal to the input single-phase voltage, determining that the live wire relay of the target phase is in a normal state;

[0031] When the output single-phase voltage is equal to the input single-phase voltage, determining that the live wire relay of the target phase is in a sticking state;

[0032] The states of the live wire relays on all target phases in the to-be-detected grid-connected relay group are determined as live wire relay fault information.

[0033] The present application also provides an inverter electrical appliance, the inverter comprising a grid-connected relay group to be detected and a controller, wherein a first voltage detection unit is provided on the output side of the grid-connected relay group to be detected and a second voltage detection unit is provided on the input side;

[0034] The controller is connected to the first voltage detection unit, the second voltage detection unit and the control end of the grid-connected relay group to be detected, the first voltage detection unit is also connected to the power grid, and the second voltage detection unit is connected to the inverter port, or the second voltage detection unit is also connected to the power grid, and the first voltage detection unit is connected to the inverter port;

[0035] The controller is used to execute the steps of the grid-connected relay fault detection method as described above.

[0036] Optionally, the grid-connected relay group to be detected includes a grid-side grid-connected relay close to the power grid and an inverter-side grid-connected relay close to the inverter port;

[0037] When the grid-side grid-connected relay is a group of relays, the first voltage detection unit and the second voltage detection unit are arranged on both sides of the grid-side grid-connected relay;

[0038] When the grid-side grid-connected relays are multiple relay groups, the first voltage detection unit and the second voltage detection unit are arranged on both sides of the multiple groups of grid-side grid-connected relays;

[0039] When the inverter-side grid-connected relay is a relay group, the first voltage detection unit and the second voltage detection unit are arranged on both sides of the inverter-side grid-connected relay;

[0040] When the inverter-side grid-connected relays are multiple relay groups, the first voltage detection unit and the second voltage detection unit are provided on both sides of the multiple groups of the inverter-side grid-connected relays.

[0041] Optionally, the controller includes a first controller and a second controller;

[0042] The first controller is connected to the control terminal of the grid-side grid-connected relay, and the second controller is connected to the control terminal of the inverter-side grid-connected relay;

[0043] The first controller is further connected to the first voltage detection unit and the second voltage detection unit, and / or the second controller is further connected to the first voltage detection unit and the second voltage detection unit.

[0044] The present application also provides an energy storage system, comprising:

[0045] An inverter, wherein the first voltage detection unit in the inverter is connected to the grid, and the second voltage detection unit in the inverter is connected to the inverter port, or the second voltage detection unit in the inverter is connected to the grid, and the first voltage detection unit in the inverter is connected to the inverter port;

[0046] The inverter is also used to execute the steps of the grid-connected relay fault detection method as described above.

[0047] The present invention provides a grid-connected relay fault detection method, which is applied to an inverter, wherein the inverter includes a grid-connected relay group to be detected, and in response to a preset neutral line relay fault detection instruction, obtains first voltage information of the grid-connected relay group to be detected in a first off-state, wherein the first off-state includes a single-phase live wire of the grid-connected relay group to be detected being conducted and a neutral line relay on the grid-connected relay group to be detected being conducted; obtains second voltage information of the grid-connected relay group to be detected in a second off-state, and performs fault detection on the grid-connected relay group to be detected based on the first voltage information and the second voltage information, wherein the second off-state includes a single-phase live wire of the grid-connected relay group to be detected being conducted and a neutral line relay on the grid-connected relay group to be detected being disconnected.

[0048] By using a preset neutral line relay fault detection instruction, first voltage information of the grid-connected relay group to be detected in a first off-state is obtained, and second voltage information of the grid-connected relay group to be detected in a second off-state is simultaneously obtained. Fault detection of the grid-connected relay group to be detected is then performed based on the first and second voltage information. The first off-state includes a single-phase live wire of the grid-connected relay group to be detected and a neutral wire of the grid-connected relay group to be detected being conductive, and the second off-state includes a single-phase live wire of the grid-connected relay group to be detected and a neutral wire relay on the grid-connected relay group to be detected being disconnected. This avoids the problem in the prior art of being unable to accurately detect a short circuit on the neutral line due to the lack of a standard sampling reference signal for the neutral line. By using the preset neutral line relay fault detection instruction, voltage information in the first and second off-states is obtained, and the voltage information in the two states is compared to obtain a fault detection result for the neutral line relay of the grid-connected relay group to be detected. This enables fault detection of the neutral line grid-connected relay, thereby improving the reliability of fault detection of the grid-connected relay. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0050] Figure 1 It is a schematic structural diagram of a grid-connected relay fault detection device in a hardware operating environment according to an embodiment of the present invention;

[0051] Figure 2 Schematic diagram of the flow of the grid-connected relay fault detection method of the present invention;

[0052] Figure 3 is a circuit connection diagram of an inverter according to a first embodiment of the present invention;

[0053] Figure 4 A schematic diagram of a module of the energy storage system of the present invention;

[0054] Figure 5 Schematic diagram of the inverter module of the present invention;

[0055] Figure 6 A control flow diagram of a grid-connected relay fault detection method according to the present invention;

[0056] Figure 7 Schematic diagram of another control flow of the grid-connected relay fault detection method of the present invention;

[0057] Figure 8 is a circuit connection diagram of an inverter according to a second embodiment of the present invention;

[0058] Figure 9 FIG. 2 is another circuit connection diagram of the inverter according to the second embodiment of the present invention.

[0059] Description of Figure Numbers:

[0060] Label name Label name 0001 Communication bus 0002 Get interface 0003 processor 0004 Processing interface 0005 Memory 600 Controller 200 Inverter port 300 Inverter 400 Power grid 500 load A Live wire phase A B Live wire phase B C Live wire phase C N Neutral 21 First voltage detection unit 22 Second voltage detection unit 23 The third voltage detection unit 11 First grid-side relay group 12 Second grid-side relay group 13 First inverter side relay group 14 Second inverter side relay group 610 Controller 1 620 Controller 2

[0061] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0062] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0063] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0064] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features specified as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0065] Reference Figure 1 , Figure 1 This is a structural diagram of a grid-connected relay fault detection device in the hardware operating environment involved in an embodiment of the present invention.

[0066] like Figure 1 As shown, the grid-connected relay fault detection device may include: a processor 0003, such as a central processing unit (CPU), a communication bus 0001, an acquisition interface 0002, a processing interface 0004, and a memory 0005. The communication bus 0001 is used to achieve connection and communication between these components. The acquisition interface 0002 may include an information acquisition device and an acquisition unit such as a computer. Optionally, the acquisition interface 0002 may also include a standard wired interface or a wireless interface. The processing interface 0004 may optionally include a standard wired interface or a wireless interface. The memory 0005 may be a high-speed random access memory (RAM) or a stable non-volatile memory (NVM), such as a disk storage device. The memory 0005 may also optionally be a storage device independent of the aforementioned processor 0003.

[0067] Those skilled in the art will understand that Figure 1 The structure shown in the figure does not constitute a limitation on the grid-connected relay fault detection device, and may include more or fewer components than shown in the figure, or combine certain components, or arrange the components differently.

[0068] like Figure 1 As shown, the memory 0005 as a computer storage medium may include an operating system, an acquisition interface module, a processing interface module and a grid-connected relay fault detection program.

[0069] exist Figure 1In the grid-connected relay fault detection device shown, the communication bus 0001 is mainly used to realize the connection communication between components; the acquisition interface 0002 is mainly used to connect to the background server and communicate data with the background server; the processing interface 0004 is mainly used to connect to the deployment end (user end) and communicate data with the deployment end; the processor 0003 and the memory 0005 in the grid-connected relay fault detection device of the present invention can be set in the grid-connected relay fault detection device, and the grid-connected relay fault detection device calls the grid-connected relay fault detection program stored in the memory 0005 through the processor 0003, and executes the grid-connected relay fault detection method provided by the embodiment of the present invention.

[0070] Based on the above hardware structure, an embodiment of a grid-connected relay fault detection method of the present invention is proposed.

[0071] In one embodiment of the present invention, Figure 2 As shown, Figure 2 : is a flow chart of a method for detecting a grid-connected relay fault according to the present invention. The method is applied to an inverter 300, which includes a grid-connected relay group to be detected. The method includes:

[0072] Step S10, in response to a preset neutral line relay fault detection instruction, obtaining first voltage information of the grid-connected relay group to be detected in a first off-state, wherein the first off-state includes a single-phase live wire of the grid-connected relay group to be detected being conductive and a neutral wire of the grid-connected relay group to be detected being conductive;

[0073] For example, with the continuous development of photovoltaic energy storage and other industries at home and abroad, inverters have become an important part of the power grid system, and the safety of inverters has become more and more important. The standard requires that the grid-connected relay needs to be controlled by two independent controllers to separately control the two relay groups connected in series in order to achieve a safe grid-connected and off-grid switching function. However, as the number of relays increases, it will become difficult to detect the state of the relays. In particular, since the N-line relay does not have a standard voltage value, it is impossible to determine whether the N-line relay is stuck by the voltage difference between the two ends of the relay. Therefore, based on the above-mentioned shortcomings of the grid-connected relay detection, the grid-connected relay fault detection method of the present application is proposed to realize the detection of the zero-line fault of the grid-connected relay, thereby improving the reliability of the fault detection of the grid-connected relay. Please refer to Figure 3 , Figure 3This is a circuit connection diagram of an inverter according to a first embodiment of the present invention. In the figure, a voltage detection unit (a first voltage detection unit 21, a second voltage detection unit 22, and a third voltage detection unit 23) is provided between two inverter-side relay groups (a first inverter-side relay group 13 and a second inverter-side relay group 13) near the inverter port 200 and two grid-side relay groups (a first grid-side relay group 11 and a second relay group 12) near the grid. The controller 600 controls the on / off states of the inverter-side relay group and the grid-side relay group. The voltage detection unit then detects the voltages across the inverter-side relay group and the grid-side relay group to determine whether a grid-connected relay fault on the neutral line exists, i.e., whether each relay group has a zero-line adhesion phenomenon. This allows for processing the situation where the neutral line does not have a standard sampling reference signal. Furthermore, the above method can be used to detect a zero-line adhesion fault, thereby improving the reliability of fault detection of the grid-connected relay.

[0074] In this embodiment, the grid-connected relay fault detection method is applied to the inverter 300, which includes a grid-connected relay group to be detected. Then, the power of the inverter port 200 or the grid 400 can be used for judgment. That is, if there is power on the grid 400 side, the voltage or voltage change can be judged based on the grid 400 side. At the same time, if there is power generated on the inverter port 200 side, the inverter port 200 side can also be used for judgment. This embodiment is described in the manner of detection with power on the grid 400 side. First, the grid-connected relay group to be detected will be determined, that is, Figure 3 One of the four relay groups is selected as the grid-connected relay group to be detected, and then the zero-line relay in the grid-connected relay group to be detected (hereinafter referred to as the zero-line relay) is subjected to adhesion detection. When the zero-line relay is subjected to adhesion detection, the first voltage information of the grid-connected relay group to be detected in the first off-state is obtained by responding to the preset zero-line relay fault detection instruction, wherein the first off-state includes the single-phase live wire of the grid-connected relay group to be detected being turned on and the zero-line of the grid-connected relay group to be detected being turned on, that is, after receiving the preset zero-line relay fault detection instruction, the detection process of the zero-line relay is executed, wherein the zero-line relay fault detection instruction includes the order of detecting the zero-line relays and the instruction of controlling the zero-line relay to be in different states, such as Figure 3For example, the order of four relay detection is 12-13-14-11, that is, 12 is detected as the grid-connected relay group to be detected during detection, and 13 is detected as the grid-connected relay group to be detected after the detection is completed, and so on. Here, the situation where 12 is detected as the grid-connected relay group to be detected is explained. First, state control is performed based on the neutral line relay fault detection instruction, that is, 12 is controlled to be in the first off state, and the first voltage information in the first off state is obtained, wherein the first off state is that the single-phase live wire of the grid-connected relay group to be detected is conductive and the neutral wire of the grid-connected relay group to be detected is conductive. It is worth noting that the single-phase live wire of the grid-connected relay group to be detected here is connected to the power supply in the three phases ABC in the grid-connected relay group to be detected. For example, the single-phase live wire of 12 is connected (that is, there is electricity in the detection units on both sides of the grid-connected relay group to be detected, that is, the phase relay is closed and the power supply and the detection units on both sides of the grid-connected relay group to be detected form a conductive line. Here, phase A is taken as an example, and other phases can be the same as or different from phase A). At this time, the power grid is supplying power, that is, the A-phase electricity of the power grid needs to reach the detection units on both sides of 12 (that is, the A-phase relays in 12 and the A-phase relays in 11 are both closed. At this time, the states of the BC-phase relays in 12 and 11 and the relays in other relay groups are not limited), and then the state at this time is that the A-phase (single-phase) live wire of the grid-connected relay group to be detected is connected; the neutral line of the grid-connected relay group to be detected refers to the same as the above-mentioned A-phase conductive situation, except that the neutral line relay of the grid-connected relay group to be detected is required to be closed and form a conductive line with the power supply. It is worth noting that according to the record of the first off-state, in addition to controlling the relays in the grid-connected relay group to be detected to be closed, the first off-state will also control the relays in the relay group close to the power supply side (such as the power grid providing power) to be closed, thereby turning on the relays in the grid-connected relay group to be detected (with current). At this time, the first voltage information in the first off-state can be collected, that is, the voltage collected by the voltage detection unit in the figure. At this time, the voltage when the single-phase live wire is turned on and the neutral wire of the grid-connected relay group to be detected is collected as the first voltage information, such as the voltage between phase A and the neutral wire. Subsequent adhesion judgment is then performed based on the first voltage information.

[0075] Step S20, obtaining the second voltage information of the grid-connected relay group to be detected in the second off-state, and performing fault detection on the grid-connected relay group to be detected based on the first voltage information and the second voltage information, wherein the second off-state includes the single-phase live wire of the grid-connected relay group to be detected being turned on, and the neutral wire relay on the grid-connected relay group to be detected being disconnected.

[0076] In this embodiment, second voltage information of the grid-connected relay group to be detected in the second off-state is simultaneously obtained, and fault detection is performed on the grid-connected relay group to be detected based on the first voltage information and the second voltage information, wherein the second off-state includes that the single-phase live wire of the grid-connected relay group to be detected is turned on, and the neutral wire relay on the grid-connected relay group to be detected is turned off, that is, the second off-state and the first off-state differ at least in that: the neutral wire relay on the grid-connected relay group to be detected is turned off. On the other hand, the second off-state and the first off-state have at least the same point in that: the single-phase live wire of the grid-connected relay group to be detected is turned on. Then, the second voltage information in the second shutdown state, that is, the voltage between phase A and the neutral line, can be determined, and then the two voltages obtained are compared to determine the fault information of the neutral line relay on the grid-connected relay group to be detected. The main thing is to compare the two voltages to determine whether a non-sinusoidal change occurs (the neutral line is disconnected in the second shutdown state, and the collected voltage reference value will change. Therefore, a non-sinusoidal change should occur when the neutral line relay is not faulty). If a non-sinusoidal change occurs, it is determined that the neutral line relay on the grid-connected relay group to be detected is not stuck. Otherwise, it is determined that the neutral line relay on the grid-connected relay group to be detected is stuck. Based on the above detection method, the reliability of the grid-connected relay detection is improved.

[0077] Further, refer to Figure 6 , Figure 6The figure is a control flow diagram of the grid-connected relay fault detection method of the present invention, which is the overall detection process of the entire inverter (including the order of detection). The entire detection process is controlled by preset neutral line relay fault detection instructions (here in the order of 11-12-13-14), and there are two relay groups on the grid side and the inverter side, and the two relay groups share a group of detection units on both sides (as indicated by the numbers in the figure). When the first grid-side relay group 11 is tested as the grid-connected relay group to be tested (at this time, phase A is selected as the single-phase live wire conduction phase for example, it can also be phase BC), the preset neutral line relay fault detection instruction is used to control the A and N phases of the first and second grid-side relay groups to be closed (that is, the first off-state of the grid-connected relay group to be tested), and when the second voltage detection unit 22 (because the power supply detection is performed on the grid 400 at this time, if the power supply detection is performed on the inverter port 200, the first voltage detection unit 21 is used for detection processing) detects that the voltage is the grid phase voltage (if the second voltage detection unit 22 detects that the voltage is not the grid phase voltage, it will be determined as a neutral line hardware control failure, that is, the hardware cannot control the normal closure of the relay, resulting in it not being a grid phase voltage), then the relay on the N phase of the first grid-side relay group is disconnected separately through the neutral line relay fault detection instruction (that is, the second off-state of the grid-connected relay group to be tested), and the second voltage detection unit 22 detects whether the voltage has an abnormal non-sinusoidal voltage change, that is, whether the voltage waveform changes. When the second voltage detection unit 22 detects an abnormal non-sinusoidal voltage change in the voltage, it is determined that the relay on the N phase of the first grid-side relay group is not stuck. Conversely, if no abnormal non-sinusoidal voltage change occurs, it is determined that the relay on the N phase of the first grid-side relay group is stuck. After detecting the relay on the N phase of the first grid-side relay group, the relay on the N phase of the second grid-side relay group is judged to be stuck based on the detection sequence of the neutral line relay fault detection instruction. At this time, the second grid-side relay group serves as the grid-connected relay group to be detected, and recloses the relay on the N phase of the first grid-side group (at this time, the A and N phases of the first and second grid-side relay groups are closed, that is, the first off-state of the grid-connected relay group to be detected), and then disconnects the relay on the N phase of the second grid-side group separately (that is, the second off-state of the grid-connected relay group to be detected), and then determines whether the voltage detected by the second voltage detection unit 22 has an abnormal change of non-sinusoidal voltage. When the voltage detected by the second voltage detection unit 22 has an abnormal change of non-sinusoidal voltage, it is determined that the relay on the N phase of the second grid-side relay group has not stuck. On the contrary, if no abnormal change of non-sinusoidal voltage occurs, it is determined that the relay on the N phase of the second grid-side relay group has stuck. It is worth noting that at this time, there can also be a detection operation of whether the detection voltage is the grid phase voltage.After detecting the relays on the N phase of the second grid-side relay group and the relays on the N phase of the first grid-side relay group, the relays on the N phase of the second inverter-side relay group and the relays on the N phase of the first inverter-side relay group will be detected. At this time, the first inverter side relay group serves as the grid-connected relay group to be detected. The neutral line relay fault detection instruction controls the closure of the relays on the A and N phases of the first and second grid-side relay groups and the first and second inverter side relay groups (i.e., the first off-state of the grid-connected relay group to be detected). When the third voltage detection unit 23 detects that the voltage is the grid phase voltage, the relay on the N phase of the first inverter side relay group is disconnected separately (i.e., the second off-state of the grid-connected relay group to be detected). The third voltage detection unit 23 detects whether the voltage has an abnormal non-sinusoidal voltage change. When the third voltage detection unit 23 detects that the voltage has an abnormal non-sinusoidal voltage change, it is determined that the relay on the N phase of the first inverter side relay group is not stuck. Otherwise, if no abnormal non-sinusoidal voltage change occurs, it is determined that the relay on the N phase of the first inverter side relay group is stuck. After detecting the relay on the N phase of the first inverter-side relay group, the relay on the N phase of the second inverter-side relay group is judged to be stuck based on the detection sequence of the neutral relay fault detection instruction. At this time, the second inverter side serves as the grid-connected relay group to be detected, and the relay on the N phase of the first inverter side group is reclosed (at this time, the relays on the A and N phases of the first and second grid-side relay groups and the first and second inverter-side relay groups are closed, that is, the first off-state of the grid-connected relay group to be detected), and then the N phase relay of the second inverter side group is disconnected separately (at this time, the A and N phases of the first and second grid-side relay groups are still closed, that is, the second off-state of the grid-connected relay group to be detected), and then it is determined whether the voltage detected by the third voltage detection unit 23 has an abnormal non-sinusoidal voltage change. When the voltage detected by the third voltage detection unit 23 has an abnormal non-sinusoidal voltage change, it is determined that the relay on the N phase of the second inverter-side relay group is not stuck. Otherwise, no abnormal non-sinusoidal voltage change occurs, and it is determined that the relay on the N phase of the second inverter-side relay group is stuck. The above control process can realize relay fault detection on the neutral line of the grid-connected relay group based on the detection sequence, thereby improving the reliability of fault detection of the grid-connected relay.

[0078] It is worth noting that the entire judgment process can be judged by the inverter port side (the inverter port side outputs electric energy and serves as the power supply end), and the core of the entire judgment process is to judge the detection unit on both sides of the grid-connected relay group, which is far away from the power supply end, as the voltage collection unit (that is, the detection unit on the output side mentioned later). The unit collects the voltage in the first off state and the second off state for judgment, that is, it is not necessary to judge in a fixed order, but each grid-connected relay group is used as the grid-connected relay group to be detected to implement voltage detection in the first off state and the second off state, and then make a judgment, wherein the voltage collection unit is ensured to be the core of the above judgment process. Therefore, this embodiment can adapt to the change detection process based on the above detection core, which is not limited here.

[0079] This embodiment provides a grid-connected relay fault detection method, which is applied to an inverter, wherein the inverter includes a grid-connected relay group to be detected, and in response to a preset neutral line relay fault detection instruction, obtains first voltage information of the grid-connected relay group to be detected in a first off-state, wherein the first off-state includes a single-phase live wire of the grid-connected relay group to be detected being conducted and a neutral line relay on the grid-connected relay group to be detected being conducted; obtains second voltage information of the grid-connected relay group to be detected in a second off-state, and performs fault detection on the grid-connected relay group to be detected based on the first voltage information and the second voltage information, wherein the second off-state includes a single-phase live wire of the grid-connected relay group to be detected being conducted and a neutral line relay on the grid-connected relay group to be detected being disconnected. By using a preset neutral line relay fault detection instruction, first voltage information of the grid-connected relay group to be detected in a first off-state is obtained, and second voltage information of the grid-connected relay group to be detected in a second off-state is simultaneously obtained. Fault detection of the grid-connected relay group to be detected is then performed based on the first and second voltage information. The first off-state includes a single-phase live wire of the grid-connected relay group to be detected and a neutral wire of the grid-connected relay group to be detected being conductive, and the second off-state includes a single-phase live wire of the grid-connected relay group to be detected and a neutral wire relay on the grid-connected relay group to be detected being disconnected. This avoids the problem in the prior art of being unable to accurately detect a short circuit on the neutral line due to the lack of a standard sampling reference signal for the neutral line. By using the preset neutral line relay fault detection instruction, voltage information in the first and second off-states is obtained, and the voltage information in the two states is compared to obtain a fault detection result for the neutral line relay of the grid-connected relay group to be detected. This enables fault detection of the neutral line grid-connected relay, thereby improving the reliability of fault detection of the grid-connected relay.

[0080] In one embodiment, based on the first embodiment of the grid-connected relay fault detection method, a second embodiment of the present application is proposed, wherein the step of performing fault detection on the grid-connected relay group to be detected based on the first voltage information and the second voltage information includes:

[0081] Step S21, detecting whether there is a waveform change between the voltage waveform of the first voltage information and the voltage waveform of the second voltage information;

[0082] Step S22: If there is a waveform change between the voltage waveform of the first voltage information and the voltage waveform of the second voltage information, determining that the neutral line relay of the grid-connected relay group to be detected is in a normal state;

[0083] Step S23: If there is no waveform change between the voltage waveform of the first voltage information and the voltage waveform of the second voltage information, it is determined that the neutral line relay of the grid-connected relay group to be detected is in a sticking state.

[0084] In this embodiment, the entire grid-connected relay fault detection method is controlled based on the original hardware structure, and the control flow of the entire method is realized by adding a voltage detection unit. It is worth noting that reference can be made to Figure 8 , Figure 8 This is a circuit connection diagram of the inverter of the present invention. The four grid-connected relay groups are controlled by controller 1 610 and controller 2 620 respectively, thereby realizing the opening and closing of the four grid-connected relay groups. At the same time, controller 1 610 and / or controller 2 620 can be connected to the voltage detection unit to detect the collected voltage to realize the grid-connected relay adhesion detection. Figure 9 , Figure 9 This is another circuit connection diagram of the inverter of the present invention. The three grid-connected relay groups (at this time, there is only one grid-connected relay group on the inverter side) are controlled by controller 1 610 and controller 2 620 respectively, so as to realize the opening and closing of the three grid-connected relay groups. At the same time, controller 1 610 and / or controller 2 620 can be connected to the voltage detection unit to detect the collected voltage to realize grid-connected relay adhesion detection. The above is only a connection diagram of the inverter and is not limited here.

[0085] In this embodiment, when detecting based on waveforms in two states, the waveform change between the voltage waveform of the first voltage information and the voltage waveform of the second voltage information is detected. The waveform change can be non-sinusoidal. Specifically, in the second off-state, the relay on the neutral line is disconnected, and the waveform reference changes, resulting in a non-sinusoidal change. If a waveform change exists between the voltage waveforms of the first voltage information and the second voltage information, the neutral line relay of the grid-connected relay group to be detected is determined to be in a normal state. In other words, the waveforms of the previous and next states have changed due to the disconnection of the neutral line relay, and therefore the neutral line relay of the grid-connected relay group to be detected is in a normal state. Conversely, if no waveform change exists between the voltage waveforms of the first voltage information and the second voltage information, the neutral line relay of the grid-connected relay group to be detected is determined to be in a stuck state. In other words, the waveforms of the previous and next states have changed due to the disconnection of the neutral line relay, and therefore the neutral line relay of the grid-connected relay group to be detected is in a stuck state. This allows for relay fault detection on the neutral line of the grid-connected relay group, thereby improving the reliability of grid-connected relay fault detection.

[0086] It is worth noting that when comparing the waveforms before and after the two states, the waveforms of the detection units on both sides of the grid-connected relay group to be tested can be directly compared. If a detection unit on one side exhibits non-sinusoidal changes between the two states, a waveform change is determined between the voltage waveform of the first voltage information and the voltage waveform of the second voltage information. Alternatively, the direction of the power supply terminal can be determined first, and then the detection unit on the side of the detection units on both sides of the grid-connected relay group that is farther from the power supply terminal can be identified as the target detection unit. The target detection unit can then be tested for any waveform change between the voltage waveforms of the first voltage information and the second voltage information collected by the target detection unit to achieve neutral relay detection.

[0087] Furthermore, the inverter includes a first voltage detection unit provided on the output side of the grid-connected relay group to be detected, and the step of obtaining first voltage information of the grid-connected relay group to be detected in the first off state in response to a preset neutral line relay fault detection instruction includes:

[0088] Step S11, in response to a preset neutral line relay fault detection instruction, obtaining a single-phase voltage collected by the first voltage detection unit of the grid-connected relay group to be detected in a first off state, and detecting whether the single-phase voltage is a preset input phase voltage;

[0089] Step S12: if the single-phase voltage is the preset input phase voltage, executing the step of obtaining the second voltage information of the to-be-detected grid-connected relay group in the second off state;

[0090] Step S13: If the single-phase voltage is not the preset input phase voltage, it is determined that the neutral relay of the grid-connected relay group to be detected has a hardware control fault.

[0091] In this embodiment, when determining the first voltage information, the voltage controlled in the first off-state is not directly used as the first voltage information. Instead, the collected voltage is judged and used as the first voltage information. The inverter also includes a first voltage detection unit provided on the output side of the grid-connected relay group to be detected. The output side of the grid-connected relay group to be detected is opposite to the output side of the power supply terminal. If the power supply terminal is the power grid, the output side of the grid-connected relay group to be detected is connected to the detection unit on the side away from the power grid. In other words, the entire first voltage information collection process involves, in response to a preset neutral relay fault detection instruction, obtaining a single-phase phase voltage collected by the first voltage detection unit in the first off-state of the grid-connected relay group to be detected, and detecting whether the single-phase phase voltage is a preset input phase voltage. The single-phase phase voltage is the voltage between any one of phases A, B, and C and the neutral line. However, if the voltage between phase A and the neutral line is selected, the voltage collected in the second off-state of the grid-connected relay group to be detected is also the voltage between phase A and the neutral line. The preset input phase voltage refers to the phase voltage inputted at the input end of the grid-connected relay group to be detected. If the input end of the grid-connected relay group to be detected is connected to the power grid, the preset input phase voltage is the power grid phase voltage. Then, when the single-phase phase voltage is the preset input phase voltage, the step of obtaining the second voltage information of the grid-connected relay group to be detected in the second off state is performed. In any case, it is determined that the zero-line relay of the grid-connected relay group to be detected is a hardware control fault, that is, the controller cannot control the zero-line relay of the grid-connected relay group to be detected to close, and then the detection of the zero-line relay of the grid-connected relay group to be detected is terminated. Subsequent detection processes are performed according to the zero-line relay fault detection instruction or user requirements. It can be used to detect the zero-line relays on other relay groups, or it can directly terminate this detection process, which is not limited here. Then, the hardware control fault of the zero-line relay can be identified to ensure the accuracy of subsequent adhesion detection.

[0092] In one embodiment, based on the first and / or second embodiments of the grid-connected relay fault detection method, a third embodiment of the present application is proposed, wherein the inverter includes a first voltage detection unit provided on the output side of the grid-connected relay group to be detected and a second voltage detection unit provided on the input side. Before the step of obtaining first voltage information of the grid-connected relay group to be detected in the first off state in response to a preset neutral line relay fault detection instruction, the grid-connected relay fault detection method further includes:

[0093] Step S100, in response to a preset live wire relay fault detection instruction, obtaining the output three-phase phase voltage collected by the first voltage detection unit and the input three-phase phase voltage collected by the second voltage detection unit of the grid-connected relay group to be detected in a third off-state, wherein the third off-state includes the three-phase live wires of the grid-connected relay group to be detected being disconnected;

[0094] Step S110, determining the live wire relay fault information of the grid-connected relay group to be detected based on the output three-phase phase voltage and the input three-phase phase voltage, and after determining the live wire relay fault information, executing the step of obtaining the first voltage information of the grid-connected relay group to be detected in the first off state in response to the preset neutral wire relay fault detection instruction.

[0095] In this embodiment, the inverter includes a first voltage detection unit provided on the output side of a grid-connected relay group to be detected and a second voltage detection unit provided on the input side. Before performing a sticking test on the neutral line relay, a sticking test is performed on the relays on the live lines of the grid-connected relay group to be detected. In response to a preset live line relay fault detection instruction, the inverter obtains the output three-phase phase voltage collected by the first voltage detection unit and the input three-phase phase voltage collected by the second voltage detection unit of the grid-connected relay group to be detected in a third off-state. The third off-state includes disconnected three-phase live lines of the grid-connected relay group to be detected. The output three-phase phase voltage refers to the three-phase voltage collected by the first voltage detection unit provided on the output side of the grid-connected relay group to be detected. The input three-phase phase voltage refers to the three-phase voltage collected by the second voltage detection unit provided on the input side of the grid-connected relay group to be detected. Disconnected three-phase live lines refers to disconnecting the relay on the live line of the grid-connected relay group to be detected, while the relays on the live lines of other relay groups are closed, at least the relays on the live lines of other relay groups near the input side of the grid-connected relay group to be detected are closed, and the relays on the live lines of other relay groups near the output side of the grid-connected relay group to be detected are in any state. The method includes determining the live relay fault information of the grid-connected relay group by comparing the input three-phase phase voltages with the output three-phase phase voltages, and then executing the step of obtaining first voltage information of the grid-connected relay group to be tested in the first off state in response to a preset neutral relay fault detection instruction after the live relay fault information of the grid-connected relay group is determined. The comparison of the input three-phase phase voltages with the output three-phase phase voltages can be performed by separately comparing the input and output voltages of phases A, B, and C. Furthermore, determining whether the live relay on the corresponding phase is stuck by determining whether the voltages on both sides of the relay (comparison is made for the same phase) are equal. This allows detection of the live relay, further improving the reliability of grid-connected relay fault detection.

[0096] It is worth noting that in this embodiment, the detection is performed in a manner of first detecting the live relay and then detecting the neutral relay. The live relay may also be detected after the neutral relay is detected. The detection order is not limited here.

[0097] Furthermore, the live wire relay fault information includes first relay fault information, second relay fault information, and third relay fault information. The step of determining the live wire relay fault information of the grid-connected relay group to be detected based on the output three-phase voltage and the input three-phase voltage includes:

[0098] Step S111, determining an output first phase voltage among the output three-phase voltages and an input first phase voltage among the input three-phase voltages, and determining that the first relay fault information is in a normal state when the output first phase voltage is not equal to the input first phase voltage;

[0099] Step S112: When the output first phase voltage is equal to the input first phase voltage, determining that the first relay fault information is in a sticking state;

[0100] In this embodiment, because there are three live relays to be detected, it is necessary to determine whether the live relays on each phase are stuck. At this time, the live relay fault information includes the first relay fault information of the relay on phase A, the second relay fault information of the relay on phase B, and the third relay fault information of the relay on phase C. Among them, the order of the three phases ABC and the corresponding relationship with the fault information can be reversed. The above corresponding relationship is used for explanation here. By determining the output first phase voltage (output side A phase voltage) in the output three-phase phase voltage and the input first phase voltage (input side A phase voltage) in the input three-phase phase voltage, and then when the output first phase voltage is not equal to the input first phase voltage, it is determined that the first relay fault information is in a normal state. That is, at this time, the relay on phase A of the grid-connected relay group to be detected is disconnected. At this time, the voltages on both sides are not equal, so it can be determined that the relay is actually in a disconnected state, so the first relay fault information is in a normal state, that is, the relay on phase A of the grid-connected relay group to be detected is not stuck; on the contrary, when the output first phase voltage is equal to the input first phase voltage, the first relay fault information is determined to be in a stuck state. That is, the relay on phase A of the grid-connected relay group to be tested is disconnected. Since the voltages on both sides are equal, it can be determined that the relay is actually closed. Therefore, the first relay fault information indicates a stuck state, indicating that the relay on phase A of the grid-connected relay group to be tested is stuck. This voltage comparison detection method allows relay detection on phase A of the grid-connected relay group to be tested.

[0101] Step S113, determining an output second-phase voltage among the output three-phase voltages and an input second-phase voltage among the input three-phase voltages, and determining that the second relay fault information is in a normal state when the output second-phase voltage is not equal to the input second-phase voltage;

[0102] Step S114: when the output second phase voltage is equal to the input second phase voltage, determining that the second relay fault information is in a sticking state;

[0103] Step S115, determining an output third-phase voltage among the output three-phase voltages and an input third-phase voltage among the input three-phase voltages, and determining that the third relay fault information is in a normal state when the output third-phase voltage is not equal to the input third-phase voltage;

[0104] Step S116: When the output third-phase voltage is equal to the input third-phase voltage, determine that the third relay fault information is in a sticking state.

[0105] In this embodiment, relay fault detection on the other two phases is also performed using the aforementioned detection method for phase A. Specifically, phases B and C are tested using the aforementioned detection method, thereby determining the fault detection results for each live relay on the three phases. Relay sticking detection on the live line is performed through voltage comparison, thereby avoiding the complexity of existing detection methods (which test relays at the factory) and improving the reliability of grid-connected relay fault detection.

[0106] In one embodiment, based on the first embodiment, the second embodiment, and / or the third embodiment of the grid-connected relay fault detection method, a fourth embodiment of the present application is proposed. The inverter includes a first voltage detection unit provided on the output side of the grid-connected relay group to be detected and a second voltage detection unit provided on the input side. Before the step of obtaining the first voltage information of the grid-connected relay group to be detected in the first off state in response to a preset neutral line relay fault detection instruction, the grid-connected relay fault detection method further includes:

[0107] Step S120, in response to a preset live wire relay fault detection instruction, sequentially acquiring an output single-phase voltage collected by the first voltage detection unit and an input single-phase voltage collected by the second voltage detection unit of a target phase of the grid-connected relay group to be detected in a fourth off-state, wherein the fourth off-state includes the live wire relay on the target phase being disconnected;

[0108] Step S130, determining the live wire relay fault information of the grid-connected relay group to be detected based on the output single-phase phase voltage and the input single-phase phase voltage, and after determining the live wire relay fault information, executing the step of obtaining the first voltage information of the grid-connected relay group to be detected in the first off state in response to the preset neutral wire relay fault detection instruction.

[0109] In this embodiment, the inverter includes a first voltage detection unit set on the output side of the grid-connected relay group to be detected and a second voltage detection unit set on the input side. Before performing adhesion detection on the relay on the neutral line, adhesion detection will be performed on the relay on the live line in the grid-connected relay group to be detected. By responding to a preset live wire relay fault detection instruction, the output single-phase phase voltage collected by the first voltage detection unit and the input single-phase phase voltage collected by the second voltage detection unit of the target phase of the grid-connected relay group to be detected are obtained in the third off-state, wherein the third off-state includes the live wire of the live wire relay on the target phase of the grid-connected relay group to be detected being disconnected, the output single-phase phase voltage refers to the target phase voltage collected by the first voltage detection unit set on the output side of the grid-connected relay group to be detected, the input single-phase phase voltage refers to the target phase voltage collected by the second voltage detection unit set on the input side of the grid-connected relay group to be detected, the live wire disconnection of the live wire relay on the target phase refers to the disconnection of the relay on the target phase of the grid-connected relay group to be detected, and the closing of the relays on the target phases of other relay groups, at least the closing of the relays on the target phases of other relay groups close to the input side of the grid-connected relay group to be detected, and the arbitrary state of the relays on the target phases of other relay groups close to the output side of the grid-connected relay group to be detected. The live relay fault information (actually, the fault information of the live relay on the target phase) of the grid-connected relay group is determined by comparing the input single-phase voltage and the output single-phase voltage. After determining the live relay fault information of the grid-connected relay group, the step of obtaining first voltage information of the grid-connected relay group to be tested in the first off state in response to a preset neutral relay fault detection instruction is executed. The comparison of the input single-phase voltage and the output single-phase voltage can be performed by comparing the input and output voltages of the target phase, and then determining whether the live relay on the target phase is stuck by determining whether the voltages on both sides of the relay are equal. This allows detection of the live relay, further improving the reliability of grid-connected relay fault detection.

[0110] It is worth noting that in this embodiment, the detection is performed in a manner of first detecting the live relay and then detecting the neutral relay. The live relay may also be detected after the neutral relay is detected. The detection order is not limited here.

[0111] Furthermore, the step of determining the live wire relay fault information of the to-be-detected grid-connected relay group according to the output single-phase voltage and the input single-phase voltage includes:

[0112] Step S131, when the output single-phase voltage is not equal to the input single-phase voltage, determining that the live wire relay of the target phase is in a normal state;

[0113] Step S132, when the output single-phase voltage is equal to the input single-phase voltage, determining that the live wire relay of the target phase is in a sticking state;

[0114] Step S133 : determining the status of the live wire relays on all target phases in the grid-connected relay group to be detected as live wire relay fault information.

[0115] In this embodiment, taking the target phase as phase A as an example, when the output single-phase phase voltage is not equal to the input single-phase phase voltage, the live wire relay of the target phase is determined to be in a normal state. That is, at this time, the relay on phase A of the grid-connected relay group to be detected is disconnected, and the voltages on both sides are not equal. It can be determined that the relay is actually in a disconnected state, so the relay on phase A is in a normal state, that is, the relay on phase A of the grid-connected relay group to be detected is not stuck; conversely, when the output single-phase phase voltage is equal to the input single-phase phase voltage, the live wire relay of the target phase is determined to be in a stuck state. That is, at this time, the relay on phase A of the grid-connected relay group to be detected is disconnected, and the voltages on both sides are equal. It can be determined that the relay is actually in a closed state, so the live wire relay of the target phase is in a stuck state, that is, the relay on phase A of the grid-connected relay group to be detected is stuck. The relay detection on phase A of the grid-connected relay group to be detected is then achieved through the above voltage comparison detection method. Based on the above method, other phases are detected as target phases, and the status of the live wire relays on all target phases in the grid-connected relay group to be detected is determined as the live wire relay fault information to realize the adhesion detection of the live wire relays in the grid-connected relay group to be detected.

[0116] In one embodiment, referring to Figure 7 , Figure 7This is another control flow diagram of the grid-connected relay fault detection method of the present invention. The figure shows the detection process of the entire judgment process (the detection sequence of the live wire relay fault detection instruction is 12-11-14-13, and this embodiment is described by taking the three-phase simultaneous detection as an example). At the same time, the entire detection process is described by taking the situation where the grid side provides electric energy. First, the second grid-side relay group is used as the grid-connected relay group to be detected. The preset live wire relay fault detection instruction is used to control the closing of the relays on the three-phase live wire and neutral wire of the first grid-side relay group, and the disconnection of the relays on the three-phase live wire and neutral wire of the second grid-side relay group (that is, the grid-connected relay group to be detected is in the third off state). Then, the voltages of the first voltage detection unit and the second voltage detection unit (that is, the detection units on the input and output sides of the grid-connected relay group to be detected) are compared to see if they are equal. At this time, the three-phase voltages collected by the voltage detection units on both sides of the second grid-side relay group are determined. The corresponding phases in the three-phase voltage (phase A on one side corresponds to phase A on the other side) are compared. If each phase is not equal, it is determined that the relays on the three phases are in a normal state, that is, the relays on the three phases ABC in the second grid-side relay group are not stuck (controlled to be disconnected, and the actual detection is also in a disconnected state); on the contrary, if the voltages of the corresponding phases are equal, it will be determined that the second grid-side relay group is actually in a stuck state, and then it will be determined which phase's relay is stuck, that is, it will be determined which phase's voltage is equal, and then it will be determined which phase's relay is stuck. Then, based on the detection sequence of the live wire relay fault detection instruction, the first grid-side relay group is detected. At this time, the relays on the three-phase live wire and neutral wire of the second grid-side relay group are controlled to close, and the relays on the three-phase live wire and neutral wire of the first grid-side relay group are disconnected (that is, the grid-connected relay group to be detected is in the third off-state). Then, the voltages of the first voltage detection unit and the second voltage detection unit (that is, the detection units on the input and output sides of the grid-connected relay group to be detected) are compared to see if they are equal. At this time, the three-phase voltages collected by the voltage detection units on both sides of the first grid-side relay group are determined, and the three-phase voltages are then The corresponding phases in the phase voltages (Phase A on one side versus Phase A on the other side) are compared. If all phases are unequal, the relays on the three phases are determined to be normal, meaning that none of the relays on phases A, B, C, and D in the first grid-side relay group are stuck (controlled as disconnected, and detected as disconnected). Conversely, if the voltages on the corresponding phases are equal, the first grid-side relay group is determined to be stuck, and the specific phase on which the relay is stuck is determined. Specifically, the order of the two determinations can be reversed.Then, based on the detection sequence of the live wire relay fault detection instruction, the second inverter side relay group is detected. At this time, the relays on the three-phase live wire and neutral wire of the second grid side relay group, the first grid side relay group and the first inverter side relay group are controlled to be closed, and the relays on the three-phase live wire and neutral wire of the second inverter side relay group are disconnected (that is, the grid-connected relay group to be detected is in the third off state). The voltages of the second voltage detection unit and the third voltage detection unit (that is, the detection units on the input and output sides of the grid-connected relay group to be detected) are compared to see whether they are equal. When the two (the third voltage detection unit and the second voltage detection power supply voltage) are equal, it can be determined that the second inverter side relay group is stuck, and then it can be accurately determined which phase is equal to determine which phase the relay is stuck on; otherwise, if the two are not equal, it will be determined that the second inverter side relay group is actually in the disconnected state, and the grid-connected relay on the live wire is not stuck, and then subsequent sequence judgments are performed. Then, based on the detection sequence of the live wire relay fault detection instruction, the first inverter side relay group is detected. At this time, the relays on the three-phase live wire and neutral wire of the second grid side relay group, the first grid side relay group, and the second inverter side relay group are controlled to be closed, and the relays on the three-phase live wire and neutral wire of the first inverter side relay group are disconnected (that is, the grid-connected relay group to be detected is in the third off state). The voltages of the second voltage detection unit and the third voltage detection unit (that is, the detection units on the input and output sides of the grid-connected relay group to be detected) are compared to see whether they are equal. If the two (the third voltage detection unit and the second voltage detection power supply voltage) are equal, it can be determined that the first inverter side relay group is stuck, and then the specific phase on which they are equal can be accurately determined to determine which phase the relay is stuck on; otherwise, if the two are not equal, it will be determined that the first inverter side relay group is actually in the off state, and the grid-connected relay on the live wire has not stuck. Then, based on the above detection method, the live wire relay sticking state is determined, thereby ensuring the accuracy of grid-connected relay fault detection.

[0117] In one embodiment, based on the first, second, third and / or fourth embodiments of the grid-connected relay fault detection method, a fifth embodiment of the inverter of the present application is proposed, wherein the inverter includes a grid-connected relay group to be detected and a controller, wherein a first voltage detection unit is provided on the output side of the grid-connected relay group to be detected and a second voltage detection unit is provided on the input side;

[0118] The controller is connected to the first voltage detection unit, the second voltage detection unit and the control end of the grid-connected relay group to be detected, the first voltage detection unit is also connected to the power grid, and the second voltage detection unit is connected to the inverter port, or the second voltage detection unit is also connected to the power grid, and the first voltage detection unit is connected to the inverter port;

[0119] The controller is used to execute the steps of any of the above embodiments of the method for detecting a grid-connected relay fault.

[0120] In this embodiment, the inverter includes a grid-connected relay group to be detected and a controller. A first voltage detection unit is set on the output side of the grid-connected relay group to be detected and a second voltage detection unit is set on the input side. The controller is connected to the first voltage detection unit, the second voltage detection unit and the control end of the grid-connected relay group to be detected respectively. The first voltage detection unit is also connected to the power grid, and the second voltage detection unit is connected to the inverter port, or the second voltage detection unit is also connected to the power grid, and the first voltage detection unit is connected to the inverter port. According to an embodiment of the present invention, a controller 600 implements the aforementioned grid-connected relay fault detection method when a processor executes a program. Based on the aforementioned grid-connected relay fault detection method, the controller 600, in response to a preset neutral line relay fault detection instruction, obtains first voltage information of the grid-connected relay group to be detected in a first off-state, wherein the first off-state includes the single-phase live wire of the grid-connected relay group to be detected being conductive and the neutral line of the grid-connected relay group to be detected being conductive; obtains second voltage information of the grid-connected relay group to be detected in a second off-state, and performs fault detection on the grid-connected relay group to be detected based on the first and second voltage information, wherein the second off-state includes the single-phase live wire of the grid-connected relay group to be detected being conductive and the neutral line relay of the grid-connected relay group to be detected being disconnected. Thus, by using the preset neutral line relay fault detection instruction, voltage information in the first and second off-states is obtained, and the voltage information in the two states is then compared to obtain a fault detection result for the neutral line relay of the grid-connected relay group to be detected, thereby achieving fault detection of the neutral line grid-connected relay, thereby improving the reliability of grid-connected relay fault detection.

[0121] Furthermore, the grid-connected relay group to be detected includes a grid-side grid-connected relay close to the power grid and an inverter-side grid-connected relay close to the inverter port;

[0122] When the grid-side grid-connected relay is a group of relays, the first voltage detection unit and the second voltage detection unit are arranged on both sides of the grid-side grid-connected relay;

[0123] When the grid-side grid-connected relays are multiple relay groups, the first voltage detection unit and the second voltage detection unit are arranged on both sides of the multiple groups of grid-side grid-connected relays;

[0124] When the inverter-side grid-connected relay is a relay group, the first voltage detection unit and the second voltage detection unit are arranged on both sides of the inverter-side grid-connected relay;

[0125] When the inverter-side grid-connected relays are multiple relay groups, the first voltage detection unit and the second voltage detection unit are provided on both sides of the multiple groups of the inverter-side grid-connected relays.

[0126] In this embodiment, the grid-connected relay group to be detected includes a grid-side grid-connected relay close to the power grid and an inverter-side grid-connected relay close to the inverter port, wherein there may be one or more grid-side grid-connected relays and inverter-side grid-connected relays, and there may also be one or more first voltage detection units and second voltage detection units, which are arranged on both sides of the grid-side grid-connected relay and / or the inverter-side grid-connected relay. That is, there may be one first voltage detection unit and one second voltage detection unit, and then when the grid-connected relay fault detection method is executed, the input and output sides of all grid-connected relay groups to be detected are the same first voltage detection unit and second voltage detection unit; there may be multiple first voltage detection units and second voltage detection units, and then when the grid-connected relay fault detection method is executed, the input and output sides of all grid-connected relay groups to be detected are different first voltage detection units and second voltage detection units; there may be one first voltage detection unit and one second voltage detection unit, and there is also a shared function of the first voltage detection unit and the second voltage detection unit, such as Figure 8 As shown, when executing the grid-connected relay fault detection method, the input and output sides of the grid-side grid-connected relay and the inverter-side grid-connected relay are different first voltage detection units and second voltage detection units, but there is a common situation.

[0127] Further, the controller includes a first controller and a second controller;

[0128] The first controller is connected to the control terminal of the grid-side grid-connected relay, and the second controller is connected to the control terminal of the inverter-side grid-connected relay;

[0129] The first controller is further connected to the first voltage detection unit and the second voltage detection unit, and / or the second controller is further connected to the first voltage detection unit and the second voltage detection unit.

[0130] In this embodiment, the controller includes a first controller and a second controller. The first controller is connected to the control terminal of the grid-side grid-connected relay to control the shutdown of the grid-side grid-connected relay. The second controller is connected to the control terminal of the inverter-side grid-connected relay to control the shutdown of the inverter-side grid-connected relay. Other connection methods are also possible and are not limited here. The first controller is also connected to the first voltage detection unit and the second voltage detection unit, and / or the second controller is also connected to the first voltage detection unit and the second voltage detection unit, and the first controller and the second controller are in communication with each other. This allows the controller to control the shutdown and collect voltage information from the voltage detection unit for fault detection. The preset neutral line relay fault detection instruction is used to obtain voltage information in the first and second off states. The voltage information in the two states is then compared to obtain a fault detection result for the neutral line relay of the grid-connected relay group to be tested, thereby detecting faults in the neutral line grid-connected relay and improving the reliability of grid-connected relay fault detection. The above is only one feasible connection method for the inverter; other connection methods are also possible and are not limited here.

[0131] Corresponding to the above embodiment, the present invention also proposes an energy storage system.

[0132] like Figure 4 As shown, the energy storage system of the embodiment of the present invention may include:

[0133] The inverter 300 has a first voltage detection unit connected to the grid, and a second voltage detection unit connected to the inverter port 200; or the second voltage detection unit connected to the grid, and the first voltage detection unit connected to the inverter port 200.

[0134] The inverter 300 is further configured to execute the steps of any of the above embodiments of the method for detecting a grid-connected relay fault.

[0135] In this embodiment, the inverter in the energy storage system may be applicable to a photovoltaic energy storage system. This embodiment is described using the photovoltaic energy storage system as an example. The photovoltaic energy storage system includes a photovoltaic module, an inverter port 200 and an inverter 300 .

[0136] The photovoltaic energy storage system, also known as a solar photovoltaic energy storage power generation system, is a power generation system consisting of photovoltaic equipment and energy storage equipment. The photovoltaic module 100, also known as a solar panel, is the core component of the photovoltaic energy storage system, converting solar energy into electrical energy. The inverter 300 (the inverter port 200 is used to connect the inverter 300 to the photovoltaic module 100) is a converter that converts DC power into constant-frequency, constant-voltage, or frequency- and voltage-regulated AC power. The power grid 400 is a system consisting of substations and transmission and distribution lines of various voltages in the power system. It includes three units: substation, transmission, and distribution, responsible for transmitting and distributing electrical energy and changing voltage. The output of the inverter 300 can also be connected to a load 500, which is a device used to convert electrical energy into other forms of energy. It can include resistors, motors, etc. The filter can be an LC filter, an LCL filter, etc., and the specific filter selection can be based on actual conditions.

[0137] According to the energy storage system of an embodiment of the present invention, the first voltage detection unit in the inverter 300 is connected to the power grid, and the second voltage detection unit in the inverter 300 is connected to the inverter port 200, or the second voltage detection unit in the inverter 300 is connected to the power grid, and the first voltage detection unit in the inverter 300 is connected to the inverter port 200. The inverter 300 is used to convert the direct current of the photovoltaic module into alternating current, and after filtering through a filter, feed it to the power grid 400 and / or power the load 500. The inverter 300 also includes a grid-connected relay group to be detected. The inverter 300 is further configured to, in response to a preset neutral line relay fault detection instruction, obtain first voltage information of the grid-connected relay group to be detected in a first off-state, wherein the first off-state includes the single-phase live wire of the grid-connected relay group to be detected being conductive and the neutral line of the grid-connected relay group to be detected being conductive; obtain second voltage information of the grid-connected relay group to be detected in a second off-state, and perform fault detection on the grid-connected relay group to be detected based on the first and second voltage information, wherein the second off-state includes the single-phase live wire of the grid-connected relay group to be detected being conductive and the neutral line relay of the grid-connected relay group to be detected being disconnected. Thus, the system obtains voltage information in the first and second off-states via the preset neutral line relay fault detection instruction, and then compares the voltage information in the two states to obtain a fault detection result for the neutral line relay of the grid-connected relay group to be detected, thereby achieving fault detection of the neutral line grid-connected relay, thereby improving the reliability of grid-connected relay fault detection.

[0138] The present invention also provides an inverter, referring to Figure 5 , Figure 5 This is a schematic diagram of an inverter module of the present invention, wherein the inverter comprises:

[0139] The voltage acquisition module A01 is configured to obtain, in response to a preset neutral line relay fault detection instruction, first voltage information of the grid-connected relay group to be detected in a first off-state, wherein the first off-state includes a single-phase live wire of the grid-connected relay group to be detected being conductive and a neutral wire of the grid-connected relay group to be detected being conductive;

[0140] The neutral line detection module A02 is used to obtain the second voltage information of the grid-connected relay group to be detected in the second off-state, and perform fault detection on the grid-connected relay group to be detected based on the first voltage information and the second voltage information, wherein the second off-state includes the single-phase live wire of the grid-connected relay group to be detected being turned on, and the neutral line relay on the grid-connected relay group to be detected being disconnected.

[0141] The present invention also provides a storage medium, which is a computer storage medium.

[0142] The storage medium of the present invention stores a grid-connected relay fault detection program, which implements the steps of the grid-connected relay fault detection method described above when executed by a processor.

[0143] The method implemented when the grid-connected relay fault detection program running on the processor is executed can refer to the various embodiments of the grid-connected relay fault detection method of the present invention, and will not be described in detail here.

[0144] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or system comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or system. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or system comprising the element.

[0145] The serial numbers of the above embodiments of the present invention are for description only and do not represent the advantages or disadvantages of the embodiments.

[0146] The above descriptions are merely optional embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present description and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for detecting a grid-connected relay fault, characterized in that: The grid-connected relay fault detection method is applied to an inverter, wherein the inverter includes a grid-connected relay group to be detected, and the grid-connected relay fault detection method includes the following steps: In response to a preset neutral line relay fault detection instruction, obtaining first voltage information of the grid-connected relay group to be detected in a first off-state, wherein the first off-state includes a single-phase live wire of the grid-connected relay group to be detected being conductive and a neutral wire of the grid-connected relay group to be detected being conductive; Obtain second voltage information of the grid-connected relay group to be detected in the second off-state, and perform fault detection on the grid-connected relay group to be detected based on the first voltage information and the second voltage information, wherein the second off-state includes that the single-phase live wire of the grid-connected relay group to be detected is turned on, and the neutral wire relay on the grid-connected relay group to be detected is disconnected.

2. The grid-connected relay fault detection method according to claim 1, wherein: The step of performing fault detection on the grid-connected relay group to be detected according to the first voltage information and the second voltage information includes: detecting whether there is a waveform change between a voltage waveform of the first voltage information and a voltage waveform of the second voltage information; If there is a waveform change between the voltage waveform of the first voltage information and the voltage waveform of the second voltage information, determining that the neutral line relay of the grid-connected relay group to be detected is in a normal state; If there is no waveform change between the voltage waveform of the first voltage information and the voltage waveform of the second voltage information, it is determined that the neutral line relay of the to-be-detected grid-connected relay group is in a sticking state.

3. The grid-connected relay fault detection method according to claim 1, wherein: The inverter includes a first voltage detection unit provided at an output side of the grid-connected relay group to be detected, and the step of obtaining first voltage information of the grid-connected relay group to be detected in a first off state in response to a preset neutral line relay fault detection instruction includes: In response to a preset neutral line relay fault detection instruction, obtaining a single-phase voltage collected by the first voltage detection unit of the grid-connected relay group to be detected in a first off state, and detecting whether the single-phase voltage is a preset input phase voltage; If the single-phase phase voltage is the preset input phase voltage, performing the step of obtaining the second voltage information of the to-be-detected grid-connected relay group in the second off state; If the single-phase voltage is not the preset input phase voltage, it is determined that the neutral line relay of the grid-connected relay group to be detected has a hardware control fault.

4. The grid-connected relay fault detection method according to claim 1, wherein: The inverter includes a first voltage detection unit provided on the output side and a second voltage detection unit provided on the input side of the grid-connected relay group to be detected. Before the step of obtaining first voltage information of the grid-connected relay group to be detected in a first off state in response to a preset neutral line relay fault detection instruction, the grid-connected relay fault detection method further includes: In response to a preset live wire relay fault detection instruction, obtaining the output three-phase phase voltage collected by the first voltage detection unit and the input three-phase phase voltage collected by the second voltage detection unit of the grid-connected relay group to be detected in a third off-state, wherein the third off-state includes the three-phase live wires of the grid-connected relay group to be detected being disconnected; Determine the live wire relay fault information of the grid-connected relay group to be detected based on the output three-phase phase voltage and the input three-phase phase voltage, and after determining the live wire relay fault information, execute the step of obtaining the first voltage information of the grid-connected relay group to be detected in the first off state in response to a preset neutral wire relay fault detection instruction.

5. The grid-connected relay fault detection method according to claim 4, characterized in that: The live wire relay fault information includes first relay fault information, second relay fault information, and third relay fault information. The step of determining the live wire relay fault information of the to-be-detected grid-connected relay group according to the output three-phase voltage and the input three-phase voltage includes: determining an output first phase voltage among the output three-phase voltages and an input first phase voltage among the input three-phase voltages, and determining that the first relay fault information is in a normal state when the output first phase voltage is not equal to the input first phase voltage; When the output first phase voltage is equal to the input first phase voltage, determining that the first relay fault information is in a sticking state; determining an output second-phase voltage among the output three-phase voltages and an input second-phase voltage among the input three-phase voltages, and determining that the second relay fault information is in a normal state when the output second-phase voltage is not equal to the input second-phase voltage; When the output second-phase voltage is equal to the input second-phase voltage, determining that the second relay fault information is in a sticking state; determining an output third-phase voltage among the output three-phase voltages and an input third-phase voltage among the input three-phase voltages, and determining that the third relay fault information is in a normal state when the output third-phase voltage is not equal to the input third-phase voltage; When the output third-phase voltage is equal to the input third-phase voltage, it is determined that the third relay fault information is in a sticking state.

6. The grid-connected relay fault detection method according to claim 1, wherein: The inverter includes a first voltage detection unit provided on the output side and a second voltage detection unit provided on the input side of the grid-connected relay group to be detected. Before the step of obtaining first voltage information of the grid-connected relay group to be detected in a first off state in response to a preset neutral line relay fault detection instruction, the grid-connected relay fault detection method further includes: In response to a preset live wire relay fault detection instruction, sequentially acquiring an output single-phase voltage collected by the first voltage detection unit and an input single-phase voltage collected by the second voltage detection unit of a target phase of the grid-connected relay group to be detected in a fourth off-state, wherein the fourth off-state includes the live wire relay on the target phase being disconnected; Determine the live wire relay fault information of the grid-connected relay group to be detected based on the output single-phase phase voltage and the input single-phase phase voltage, and after determining the live wire relay fault information, execute the step of obtaining the first voltage information of the grid-connected relay group to be detected in the first off state in response to a preset neutral wire relay fault detection instruction.

7. The grid-connected relay fault detection method according to claim 6, wherein: The step of determining the live wire relay fault information of the to-be-detected grid-connected relay group according to the output single-phase voltage and the input single-phase voltage comprises: When the output single-phase voltage is not equal to the input single-phase voltage, determining that the live wire relay of the target phase is in a normal state; When the output single-phase voltage is equal to the input single-phase voltage, determining that the live wire relay of the target phase is in a sticking state; The states of the live wire relays on all target phases in the to-be-detected grid-connected relay group are determined as live wire relay fault information.

8. An inverter, characterized in that: The inverter comprises a grid-connected relay group to be detected and a controller, wherein a first voltage detection unit is provided on the output side of the grid-connected relay group to be detected and a second voltage detection unit is provided on the input side; The controller is connected to the first voltage detection unit, the second voltage detection unit and the control end of the grid-connected relay group to be detected, the first voltage detection unit is also connected to the power grid, and the second voltage detection unit is connected to the inverter port, or the second voltage detection unit is also connected to the power grid, and the first voltage detection unit is connected to the inverter port; The controller is used to execute the steps of the grid-connected relay fault detection method according to any one of claims 1 to 7.

9. The inverter according to claim 8, characterized in that: The grid-connected relay group to be detected includes a grid-side grid-connected relay close to the power grid and an inverter-side grid-connected relay close to the inverter port; When the grid-side grid-connected relay is a group of relays, the first voltage detection unit and the second voltage detection unit are arranged on both sides of the grid-side grid-connected relay; When the grid-side grid-connected relays are multiple relay groups, the first voltage detection unit and the second voltage detection unit are arranged on both sides of the multiple groups of grid-side grid-connected relays; When the inverter-side grid-connected relay is a relay group, the first voltage detection unit and the second voltage detection unit are arranged on both sides of the inverter-side grid-connected relay; When the inverter-side grid-connected relays are multiple relay groups, the first voltage detection unit and the second voltage detection unit are provided on both sides of the multiple groups of the inverter-side grid-connected relays.

10. The inverter according to claim 9, wherein: The controller includes a first controller and a second controller; The first controller is connected to the control terminal of the grid-side grid-connected relay, and the second controller is connected to the control terminal of the inverter-side grid-connected relay; The first controller is further connected to the first voltage detection unit and the second voltage detection unit, and / or the second controller is further connected to the first voltage detection unit and the second voltage detection unit.

11. An energy storage system, characterized in that: The energy storage system comprises: An inverter, wherein the first voltage detection unit in the inverter is connected to the grid, and the second voltage detection unit in the inverter is connected to the inverter port, or the second voltage detection unit in the inverter is connected to the grid, and the first voltage detection unit in the inverter is connected to the inverter port; The inverter is further configured to execute the steps of the grid-connected relay fault detection method according to any one of claims 1 to 7.

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