Relay fault detection method, device and grid-connected system

Abstract

The application provides a fault detection method and device of a relay and a grid-connected system. The grid-connected system comprises a power converter, the power converter is connected with a power grid through a neutral line and at least one phase line, the neutral line comprises a first relay and a second relay connected in series, the first relay is connected with the power converter, the second relay is connected with the power grid, and each phase line is provided with a third relay. In the state that the second relay and the third relay are kept disconnected and the grid-connected system is off-grid, the method can detect whether the first relay has a fault by detecting the deviation between the size of the phase voltage between the two ends of the first relay on the neutral line and the same phase line and combining the current open or closed state of the first relay controlled. Thus, the voltage can be used to simply and quickly detect whether the relay on the neutral line has a fault, so as to improve the safety of the grid-connected system.

Description

Technical Field

[0001] This application relates to the field of power electronics, and more specifically, to a method, apparatus and grid-connected system for detecting relay faults. Background Technology

[0002] Currently, in three-phase four-wire grid-connected systems, a relay is used for the neutral line between the power converter and the grid. This relay controls the on / off state of the neutral line, thus enabling various functions. For example, it can balance the three-phase currents when they are unbalanced, or it can provide a grounding reference point for the system, reducing the risk of electric shock and improving system safety.

[0003] However, detecting whether there are faults such as sticking or abnormal engagement of the relays on the neutral line is a current technical challenge. If it is not possible to effectively detect whether there are faults in the relays installed on the neutral line, it will affect the safety of the grid-connected system. Summary of the Invention

[0004] This application provides a method, device, and grid-connected system for detecting relay faults. The various aspects involved in this application are described below.

[0005] Firstly, a fault detection method for a relay is provided, applied to a grid-connected system. The grid-connected system includes a power converter, which is connected to the power grid via a neutral line and at least one phase line. The neutral line includes a first relay and a second relay connected in series. The first relay is connected to the power converter, and the second relay is connected to the power grid. A third relay is provided on each phase line. The method includes: keeping both the second and third relays open; controlling the power converter to output an AC voltage so that a first voltage between the first line and the second line reaches a first threshold. The first line is the line between the third relay and the power converter on the first phase line of at least one phase line, and the second line is the line between the first relay and the power converter on the neutral line. Based on the control state of the first relay and the deviation between the first voltage and the second voltage, determining whether the first relay is faulty, the second voltage is the voltage between the first line and the third line, the third line is the line between the first relay and the second relay on the neutral line, and the control state is the state of the first relay, including an open state and a closed state.

[0006] In one possible implementation, determining whether the first relay is faulty based on its control state and the deviation between the first voltage and the second voltage includes: controlling the first relay to be in an open state; and determining whether the first relay has a sticking fault based on the deviation between the first voltage and the second voltage.

[0007] In one possible implementation, determining whether the first relay has a sticking fault based on the deviation between the first voltage and the second voltage includes: determining that the first relay has a sticking fault when the deviation between the first voltage and the second voltage is less than or equal to a second threshold, wherein the second threshold is less than or equal to the first threshold.

[0008] In one possible implementation, determining that the first relay has a sticking fault when the deviation between the first voltage and the second voltage is less than or equal to the second threshold includes: determining that the first relay has a sticking fault when the deviation between the first voltage and the second voltage is always less than or equal to the second threshold within a preset time period.

[0009] In one possible implementation, determining whether the first relay is faulty based on its control state and the deviation between the first voltage and the second voltage includes: controlling the first relay to be in a closed state; and determining whether the first relay has an abnormal engagement fault based on the deviation between the first voltage and the second voltage.

[0010] In one possible implementation, determining whether the first relay has an abnormal engagement fault based on the deviation between the first voltage and the second voltage includes: determining that the first relay has an engagement fault when the deviation between the first voltage and the second voltage is greater than or equal to a second threshold, wherein the second threshold is less than or equal to the first threshold.

[0011] In one possible implementation, determining that the first relay has an abnormal engagement fault when the deviation between the first voltage and the second voltage is greater than or equal to the second threshold includes: determining that the first relay has an abnormal engagement fault when the deviation between the first voltage and the second voltage is always greater than or equal to the second threshold within a preset time period.

[0012] Secondly, a relay fault detection device is provided, applied to a grid-connected system. The grid-connected system includes a power converter, which is connected to the power grid via a neutral line and at least one phase line. The neutral line includes a first relay and a second relay connected in series. The first relay is connected to the power converter, and the second relay is connected to the power grid. A third relay is provided on the phase line. The device includes: a control module for keeping both the second and third relays open, controlling the power converter to output an AC voltage so that the first voltage between the first line and the second line reaches a first threshold. The first line is the line between the third relay and the power converter on the first phase line of at least one phase line, and the second line is the line between the first relay and the power converter on the neutral line; and a detection module for determining whether the first relay is faulty based on the control state of the first relay and the deviation between the first voltage and the second voltage. The second voltage is the voltage between the first line and the third line, and the third line is the line between the first relay and the second relay on the neutral line. The control state is the state of the first relay according to the control status, including an open state and a closed state.

[0013] In one possible implementation, the detection module is specifically used to control the first relay to be in an open state; and to determine whether the first relay has a sticking fault based on the deviation between the first voltage and the second voltage.

[0014] In one possible implementation, the detection module is specifically used to determine that the first relay has an adhesion fault when the deviation between the first voltage and the second voltage is less than or equal to a second threshold, wherein the second threshold is less than or equal to the first threshold.

[0015] In one possible implementation, the detection module is specifically used to determine that the first relay has a sticking fault when the deviation between the first voltage and the second voltage is always less than or equal to the second threshold within a preset time period.

[0016] In one possible implementation, the detection module is specifically used to control the first relay to be in a closed state; and to determine whether the first relay has an abnormal engagement fault based on the deviation between the first voltage and the second voltage.

[0017] In one possible implementation, the detection module is specifically used to determine that the first relay has a pull-in fault when the deviation between the first voltage and the second voltage is greater than or equal to a second threshold, wherein the second threshold is less than or equal to the first threshold.

[0018] In one possible implementation, the detection module is specifically used to determine that the first relay has an abnormal engagement fault when the deviation between the first voltage and the second voltage is always greater than or equal to the second threshold within a preset time period.

[0019] Thirdly, a grid-connected system is provided, comprising: a power converter, the power converter being connected to the power grid via a neutral line and at least one phase line, the neutral line including a first relay and a second relay connected in series, the first relay being connected to the power converter and the second relay being connected to the power grid, a third relay being provided on the phase line, and a controller for executing the method described in the first aspect or any possible implementation thereof.

[0020] Fourthly, a computer-readable storage medium is provided having a computer program stored thereon, the computer program including program instructions that, when executed by a controller of a grid-connected system, perform the method described in the first aspect or any possible implementation thereof.

[0021] In this embodiment, in an off-grid state, the deviation between the voltage (i.e., phase voltage) between the two ends of a relay (such as a first relay) on the neutral line and the same phase line can be detected. By utilizing the fact that the phase voltage on the side disconnected from the power converter is almost zero after the relay is opened, and combining this with the current open or closed state of the relay under control, a fault in the relay can be detected. Therefore, faults in relays can be easily and quickly detected through voltage, thereby improving the safety of the grid-connected system. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the grid-connected system provided in the embodiments of this application;

[0024] Figure 2 This is one of the flowcharts illustrating the relay fault detection method provided in the embodiments of this application;

[0025] Figure 3 This is a second schematic flowchart of the relay fault detection method provided in the embodiments of this application;

[0026] Figure 4 This is a schematic diagram of the structure of the relay fault detection device provided in the embodiments of this application. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0028] Currently, in three-phase four-wire grid-connected systems, a relay is used for the neutral line between the power converter and the grid. This relay controls the on / off state of the neutral line, thus enabling various functions. For example, it can balance the three-phase currents when they are unbalanced, or it can provide a grounding reference point for the system, reducing the risk of electric shock and improving system safety.

[0029] However, detecting whether there are faults such as sticking or abnormal engagement of the relays on the neutral line is a current technical challenge. If it is not possible to effectively detect whether there are faults in the relays installed on the neutral line, it will affect the safety of the grid-connected system.

[0030] Therefore, to address the aforementioned problems, this application provides a relay fault detection method for detecting faults in relays installed on the neutral line of a power converter in a grid-connected system. This method, in an off-grid state, detects the deviation between the voltage (i.e., phase voltage) between the two ends of a relay (such as a first relay) on the neutral line and the same phase line. It utilizes the fact that the phase voltage on the side disconnected from the power converter is almost zero after the relay is opened, combined with the current open or closed state of the relay, to detect whether a relay is faulty. Thus, it provides a simple and quick way to detect relay faults through voltage, thereby improving the safety of the grid-connected system.

[0031] In this embodiment, the relay fault detection method can be applied to a corresponding grid-connected system. This grid-connected system may include a power converter, which is connected to the power grid via a neutral line and at least one phase line. For example, the power converter may use a single-phase two-wire system, connecting to the grid using one phase line and one neutral line; or it may use a two-phase three-wire system, connecting to the grid using two phase lines and one neutral line; or it may use a three-phase four-wire system, connecting to the grid using three phase lines and one neutral line. A first relay and a second relay are connected in series on the neutral line between the power converter and the grid, thereby jointly controlling the on / off state of the neutral line. For example, the second relay controls whether the neutral line is connected to or disconnected from the grid, and the first relay controls the on / off state of the neutral line. A third relay is installed on each phase line between the power converter and the grid, which can control the on / off state of the corresponding phase line, thereby controlling whether the corresponding phase line is connected to or disconnected from the grid.

[0032] Optionally, the power converter in this grid-connected system can be an inverter, a converter, or the like. For example, when the power converter is an inverter, the grid-connected system can convert the DC power from the DC power supply into AC power and supply it to the grid. As another example, when the power converter is a converter, the grid-connected system can also convert the DC power from the energy storage battery into AC power and supply it to the grid, and it can also convert the AC power from the grid into DC power and supply it to the energy storage battery.

[0033] For example, taking a power converter connected to the power grid using a three-phase four-wire system as an example, such as Figure 1 As shown, the grid-connected system may include a power converter, which is connected to the R phase of the grid via phase line a, the S phase of the grid via phase line b, the T phase of the grid via phase line c, and the grounding line G of the grid via neutral line n.

[0034] The neutral line n can be equipped with a first relay S4 and a second relay S8 connected in series. Each phase line has a third relay. For example, phase line a has a third relay S5, phase line b has a third relay S6, and phase line c has a third relay S7.

[0035] In this embodiment, a corresponding set of relays, such as a fourth relay, can be further installed between the third relay and the power converter on each phase line. This allows the third and fourth relays to jointly control the connection between the corresponding phase line and the power grid, thereby improving the safety of the grid-connected system. For example, as... Figure 1 As shown, a fourth relay S1 can also be installed on phase line a, a fourth relay S2 can also be installed on phase line b, and a fourth relay S3 can also be installed on phase line c.

[0036] Therefore, based on the above-mentioned grid-connected system, the fault detection method of the relay provided in this application can be used to detect the fault of the relay installed on the neutral line in the grid-connected system by detecting the deviation between the voltage (i.e., phase voltage) between the two ends of the relay (such as the first relay S4) on the neutral line and the same phase line.

[0037] Therefore, in practical applications, the relay fault detection method provided in this application is combined with... Figure 1 Taking a grid-connected system as an example, corresponding voltage detection devices can be installed at both ends of the first relay S4 to detect the voltage between the two ends of the first relay S4 and the same phase line in the off-grid state of the grid-connected system. For example, to detect the voltage between phase line a and the two ends of the first relay S4, corresponding voltage detection devices V1 and V2 can be installed. When each phase line also has a corresponding fourth relay, voltage detection device V2 can also be configured to detect the voltage between the line between the fourth relay S1 and the third relay S5 on phase line a, and the line between the first relay S4 and the second relay S8 on the neutral line. Figure 1 (This is illustrated as an example).

[0038] Of course, the above is only an example of setting up a voltage detection device. When the relay fault detection method provided in this application detects the fault of the relay by detecting the deviation between the voltage between the two ends of the relay and phase line b or phase line c, the voltage detection device can be set to detect the voltage between the corresponding phase line and the two ends of the relay. The specific setting method can be referred to the above example, and will not be repeated here.

[0039] As an example, in this embodiment, each relay in the grid-connected system can be driven by a corresponding driver (not shown in the figure). Furthermore, the grid-connected system may include a controller (not shown in the figure), which can be connected to each driver and a voltage detection device. The controller can be a controller within a power converter or a separately configured controller; no limitation is made here.

[0040] It should be noted that in practical applications, grid-connected systems may also include other necessary or required devices besides those listed above, and no restrictions are imposed here.

[0041] In the embodiments of this application, the relay fault detection method provided in this application can be executed by the controller in the grid-connected system.

[0042] The following describes in detail, with reference to the accompanying drawings and based on the aforementioned grid-connected system, a relay fault detection method provided in the embodiments of this application.

[0043] like Figure 2 As shown in the embodiments of this application, a relay fault detection method may include the following S201-S202.

[0044] S201. Keep both the second and third relays open and control the power converter to output AC voltage so that the first voltage between the first line and the second line reaches the first threshold.

[0045] In this embodiment, the first phase line is the line between the third relay and the power converter on the first phase line of the grid-connected system, and the second line is the line between the first relay and the power converter on the neutral line. In this application embodiment, the first phase line can be any phase line in the grid-connected system; there is no limitation here. For example, taking the first phase line as... Figure 1 Taking phase line a in the grid-connected system shown as an example, the first line can be the line between the third relay S5 on phase line a and the power converter, and the second line is... Figure 1 The circuit between the first relay S4 on the neutral line n and the power converter in the grid-connected system shown.

[0046] As an example, when a fourth relay is installed on each phase line of a grid-connected system, the first voltage can be further defined as the line between the fourth relay on the first phase line and the power converter (e.g., using...). Figure 1 Taking phase line a as the first phase line as an example, the voltage between the fourth relay S1 and the power converter and the second phase line.

[0047] The first voltage can be detected by setting a corresponding voltage detection device; there are no restrictions here.

[0048] By keeping the second and third relays disconnected, each phase line and the neutral line of the power converter can be disconnected from the power grid, thus putting the grid-connected system in an off-grid state. This prevents grid voltage from interfering with the relay fault detection.

[0049] For example, the controller can control the corresponding driver to drive the second and third relays to disconnect.

[0050] As an example, in this embodiment of the application, the first threshold can be the reference voltage of the power converter, or it can be a voltage value set according to the actual situation, and there is no limitation here.

[0051] S202. Determine whether the first relay is faulty based on the control state of the first relay and the deviation between the first voltage and the second voltage.

[0052] The second voltage is the voltage between the first and third lines mentioned above, and the third line is the line between the first and second relays on the neutral line, for example... Figure 1 The circuit between the first relay S4 and the second relay S8 shown in the diagram.

[0053] The control state is determined by the state of the first relay, including the open state and the closed state. In other words, the control state is the corresponding switching state of the first relay after it is controlled.

[0054] As an example, when a fourth relay is installed on each phase line of a grid-connected system, the second voltage can be further defined as the line between the third and fourth relays on the first phase line of each phase line (e.g., using...). Figure 1 Taking phase line a as the first phase line as an example, the voltage between the line between the third relay S5 and the fourth relay S1 and the third line.

[0055] In this embodiment, the second voltage can be detected by a corresponding voltage detection device, and there is no limitation here.

[0056] In some possible embodiments of this application, when determining whether the first relay is faulty based on its control state and the deviation between the first voltage and the second voltage, the first relay may be controlled to be in an open state, and then the sticking fault of the first relay may be determined based on the deviation between the first voltage and the second voltage. Alternatively, the first relay may be controlled to be in a closed state, and then the abnormal engagement fault of the first relay may be determined based on the deviation between the first voltage and the second voltage.

[0057] The processes for determining whether the first relay has a sticking fault and whether it has a pulling abnormality fault can both be executed to detect both. Alternatively, only one of them can be executed to detect either sticking or pulling abnormality faults in the first relay; there is no restriction on this.

[0058] Furthermore, when both the process of determining whether the first relay has a sticking fault and the process of determining whether the first relay has a pulling abnormal fault are executed, the order in which the two faults are judged is not limited in this embodiment. It is possible to judge whether the first relay has a sticking fault first, or to judge whether the first relay has a pulling abnormal fault first.

[0059] As an example, when controlling the first relay to be in an open state and then determining whether the first relay has a sticking fault based on the deviation between the first voltage and the second voltage, this can be achieved by determining whether the deviation between the first voltage and the second voltage is less than or equal to a second threshold. The second threshold can be set to a value less than or equal to the aforementioned first threshold. The difference between the second threshold and the first threshold can be determined based on the required detection accuracy. For example, when a high detection accuracy is required to detect whether the first relay has a fault, the second threshold can be set to a value closer to the first threshold; when a lower detection accuracy is required, the second threshold can be set to a value significantly different from the first threshold. For instance, when the first threshold is the reference voltage of the power converter, the second threshold can be the minimum reference voltage value of the power converter.

[0060] In the grid-connected system of this application, when the second relay remains open and the first relay is in the open state, the line between the first and second relays on the neutral line is disconnected from both the power converter and the power grid. At this time, the voltage between the line between the first and second relays on the neutral line and the corresponding phase line, i.e., the second voltage, should be close to zero, and the deviation between the second voltage and the aforementioned first voltage will be close to the first voltage (i.e., the first threshold). Conversely, when the second relay remains open and the first relay is in the closed state, the line between the first and second relays on the neutral line is connected to the power converter, and the potentials are equal. At this time, the voltage between the line between the first and second relays on the neutral line and the corresponding phase line, i.e., the second voltage, should be close to the aforementioned first voltage, and the deviation between the second voltage and the aforementioned first voltage will be close to zero.

[0061] Therefore, after controlling the first relay to be in the open state, if the deviation between the first voltage and the second voltage is less than or equal to the second threshold, it indicates that the first relay is actually in the closed state, and it can be determined that the first relay has an adhesion fault.

[0062] In one possible implementation of this application, after controlling the first relay to be in the off state, the sticking fault of the first relay can be determined based on the duration during which the deviation between the first voltage and the second voltage is less than or equal to a second threshold. When the duration meets a preset time limit, the sticking fault of the first relay can be determined. That is, the sticking fault of the first relay can be determined if the deviation between the first voltage and the second voltage is always less than or equal to the second threshold within a preset time limit. Therefore, the preset time limit can be used to avoid intermittent occurrences, thereby improving the accuracy of determining whether the first relay has a sticking fault.

[0063] As an example, when controlling the first relay to be in a closed state and then determining whether the first relay has an abnormal engagement fault based on the deviation between the first voltage and the second voltage, this can be achieved by determining whether the deviation between the first voltage and the second voltage is greater than or equal to a second threshold. The second threshold can be set to a value less than or equal to the aforementioned first threshold. The difference between the second threshold and the first threshold can be determined according to the required detection accuracy. For example, when a high detection accuracy is required to detect whether the first relay has a fault, the second threshold can be set to a value closer to the first threshold; when a lower detection accuracy is required, the second threshold can be set to a value significantly different from the first threshold. For example, when the first threshold is the reference voltage of the power converter, the second threshold can be the minimum reference voltage value of the power converter.

[0064] In the grid-connected system of this application, when the second relay remains open and the first relay is in the open state, the line between the first and second relays on the neutral line is disconnected from both the power converter and the power grid. At this time, the voltage between the line between the first and second relays on the neutral line and the corresponding phase line, i.e., the second voltage, should be close to zero, and the deviation between the second voltage and the aforementioned first voltage will be close to the first voltage (i.e., the first threshold). Conversely, when the second relay remains open and the first relay is in the closed state, the line between the first and second relays on the neutral line is connected to the power converter, and the potentials are equal. At this time, the voltage between the line between the first and second relays on the neutral line and the corresponding phase line, i.e., the second voltage, should be close to the aforementioned first voltage, and the deviation between the second voltage and the aforementioned first voltage will be close to zero.

[0065] Therefore, after controlling the first relay to be in the closed state, if the deviation between the first voltage and the second voltage is greater than or equal to the second threshold, it indicates that the first relay is actually in the open state, and it can be determined that the first relay has an abnormal engagement fault.

[0066] In one possible implementation of this application, after controlling the first relay to be in a closed state, the first relay can be determined to have a pull-in abnormality fault based on the duration for which the deviation between the first voltage and the second voltage is greater than or equal to a second threshold. When the duration meets a preset time limit, the first relay can be determined to have a pull-in abnormality fault. That is, the first relay can be determined to have a pull-in abnormality fault if the deviation between the first voltage and the second voltage is consistently greater than or equal to the second threshold within a preset time limit. Therefore, the preset time limit can be used to avoid sporadic occurrences, thereby improving the accuracy of determining whether the first relay has a pull-in abnormality fault.

[0067] It should be noted that the aforementioned preset duration can be set according to the actual situation, and there are no restrictions here.

[0068] Based on the aforementioned implementation methods, in practical applications, the control of each relay in the grid-connected system can be combined with the detection of adhesion faults and abnormal engagement faults of the first relay on the neutral line to determine whether the first relay can open and close normally. For example, with Figure 1 Taking the grid-connected system shown as an example, if the second relay S8 and the third relays S5, S6, and S7 are kept disconnected, then... Figure 3 As shown, the power converter can be controlled to output AC voltage first, and then the first voltage Van between the first relay S4 and the power converter, and between the fourth relay S1 and the power converter, can be detected. It is determined whether the first voltage Van is less than or equal to the first threshold Vref; otherwise, the fourth relays S1, S2, and S3 can be activated. Then, the second voltage VAN between the first relay S4 and the second relay S8, and between the third relay S5 and the fourth relay S1, can be detected. It is determined whether the absolute value of the difference between the first voltage Van and the second voltage VAN is less than or equal to the second threshold Vref_min, and the duration is Ts. If yes, the first relay S4 is confirmed to be stuck. If not, the first relay S4 can be activated. Then, it is determined whether the absolute value of the difference between the first voltage Van and the second voltage VAN is less than or equal to the second threshold Vref_min, and the duration is Ts. If not, the first relay S4 is confirmed to be malfunctioning. If yes, the first relay S4 is confirmed to be working normally. Of course, it can also be based on... Figure 3 The process shown, combined with the aforementioned relay fault detection method, first checks for abnormal engagement of the first relay on the neutral line, and then checks for sticking faults. No restrictions are placed here; for specific implementation details, please refer to [reference needed]. Figure 3 The process shown is not elaborated here.

[0069] In one possible implementation of this application, the second relay on the neutral line of the grid-connected system provided in this application can also be fault-detected in the same way. The implementation method is similar to that for detecting the fault of the first relay, except that when detecting the second relay, the first and third relays are kept disconnected. Then, based on the control state of the second relay and the deviation between the aforementioned first and second voltages, it is determined whether the second relay is faulty. Specifically, the implementation method for fault detection of the first relay described in the foregoing example can be referred to by analogy, and will not be repeated here.

[0070] Based on the aforementioned relay fault detection method, in an off-grid state, the deviation between the voltage (i.e., phase voltage) between the two ends of a relay (such as the first relay) on the neutral line and the same phase line can be detected. By utilizing the fact that the phase voltage on the side disconnected from the power converter is almost zero after the relay is opened, and combining this with the current open or closed state of the relay under control, the presence of a relay fault can be detected. Therefore, it is possible to easily and quickly detect relay faults through voltage, thereby improving the safety of the grid-connected system.

[0071] The method embodiments of this application have been described in detail above with reference to the accompanying drawings. The apparatus embodiments of this application will now be described in detail. It should be understood that the descriptions of the apparatus embodiments correspond to the descriptions of the method embodiments; therefore, any parts not described in detail can be referred to the foregoing method embodiments.

[0072] This application also provides a relay fault detection device. Applied to a grid-connected system, the grid-connected system includes a power converter, which is connected to the power grid via a neutral line and at least one phase line. The neutral line includes a first relay and a second relay connected in series. The first relay is connected to the power converter, and the second relay is connected to the power grid. A third relay is provided on the phase line. (See reference...) Figure 4 As shown, the device includes: a control module 401, used to keep both the second and third relays open, and control the power converter to output AC voltage so that the first voltage between the first line and the second line reaches a first threshold. The first line is the line between the third relay and the power converter on the first phase line of at least one phase line, and the second line is the line between the first relay and the power converter on the neutral line. A detection module 402 is used to determine whether the first relay is faulty based on the control state of the first relay and the deviation between the first voltage and the second voltage. The second voltage is the voltage between the first line and the third line, the third line is the line between the first relay and the second relay on the neutral line, and the control state is the state of the first relay according to the control status, including an open state and a closed state.

[0073] In one possible implementation, the detection module 402 is specifically used to control the first relay to be in an open state; and to determine whether the first relay has a sticking fault based on the deviation between the first voltage and the second voltage.

[0074] In one possible implementation, the detection module 402 is specifically used to determine that the first relay has a sticking fault when the deviation between the first voltage and the second voltage is less than or equal to a second threshold, and the second threshold is less than or equal to the first threshold.

[0075] In one possible implementation, the detection module 402 is specifically used to determine that the first relay has a sticking fault when the deviation between the first voltage and the second voltage is always less than or equal to the second threshold within a preset time period.

[0076] In one possible implementation, the detection module 402 is specifically used to control the first relay to be in a closed state; and to determine whether the first relay has an abnormal engagement fault based on the deviation between the first voltage and the second voltage.

[0077] In one possible implementation, the detection module 402 is specifically used to determine that the first relay has a pull-in fault when the deviation between the first voltage and the second voltage is greater than or equal to a second threshold, and the second threshold is less than or equal to the first threshold.

[0078] In one possible implementation, the detection module 402 is specifically used to determine that the first relay has an abnormal engagement fault when the deviation between the first voltage and the second voltage is always greater than or equal to the second threshold within a preset time period.

[0079] This application embodiment also provides a grid-connected system, including: a power converter, the power converter being connected to the power grid via a neutral line and at least one phase line, the neutral line including a first relay and a second relay connected in series, the first relay being connected to the power converter, the second relay being connected to the power grid, a third relay being provided on the phase line, and a controller, the controller being used to execute the method described in any of the preceding embodiments.

[0080] This application also provides a computer-readable storage medium storing a computer program thereon. The computer program includes program instructions, which, when executed by the controller of the grid-connected system, perform the methods described in any of the preceding embodiments.

[0081] It should be understood that, in the embodiments of this application, determining B based on A does not mean determining B solely based on A; B can also be determined based on A and / or other information.

[0082] It should be understood that in the embodiments of this application, "B corresponding to A" means that B is associated with A, and B can be determined based on A. However, it should also be understood that determining B based on A does not mean that B is determined solely based on A; B can also be determined based on A and / or other information.

[0083] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0084] It should be understood that in the various embodiments of this application, the order of the above-mentioned processes does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0085] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0086] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0087] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0088] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can read or a data storage device such as a server or data center that integrates one or more available media. The available media can be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., digital video discs, DVDs) or semiconductor media (e.g., solid-state disks, SSDs) etc.

[0089] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for detecting relay faults, characterized in that, The method is applied to a grid-connected system, the grid-connected system including a power converter, the power converter being connected to the power grid via a neutral line and at least one phase line, the neutral line including a first relay and a second relay connected in series, the first relay being connected to the power converter, the second relay being connected to the power grid, and a third relay being provided on the phase line. The method includes: Keeping both the second and third relays disconnected, the power converter is controlled to output AC voltage so that the first voltage between the first line and the second line reaches a first threshold. The first line is the line between the third relay and the power converter on the first phase line of the at least one phase line, and the second line is the line between the first relay and the power converter on the neutral line. Based on the control state of the first relay and the deviation between the first voltage and the second voltage, it is determined whether the first relay is faulty. The second voltage is the voltage between the first line and the third line. The third line is the line between the first relay and the second relay on the neutral line. The control state is the state of the first relay according to the control, including the open state and the closed state.

2. The method according to claim 1, characterized in that, The step of determining whether the first relay is faulty based on the control state of the first relay and the deviation between the first voltage and the second voltage includes: Control the first relay to be in the off state; Based on the deviation between the first voltage and the second voltage, determine whether the first relay has a sticking fault.

3. The method according to claim 2, characterized in that, The step of determining whether the first relay has a sticking fault based on the deviation between the first voltage and the second voltage includes: When the deviation between the first voltage and the second voltage is less than or equal to a second threshold, it is determined that the first relay has an adhesion fault, and the second threshold is less than or equal to the first threshold.

4. The method according to claim 3, characterized in that, The step of determining that the first relay has a sticking fault when the deviation between the first voltage and the second voltage is less than or equal to the second threshold includes: If the deviation between the first voltage and the second voltage is always less than or equal to the second threshold within a preset time period, it is determined that the first relay has an adhesion fault.

5. The method according to any one of claims 1-4, characterized in that, The step of determining whether the first relay is faulty based on the control state of the first relay and the deviation between the first voltage and the second voltage includes: Control the first relay to be in the closed state; Based on the deviation between the first voltage and the second voltage, determine whether the first relay has an abnormal engagement fault.

6. The method according to claim 5, characterized in that, The step of determining whether the first relay has an abnormal engagement fault based on the deviation between the first voltage and the second voltage includes: When the deviation between the first voltage and the second voltage is greater than or equal to the second threshold, it is determined that the first relay has a failure to engage, and the second threshold is less than or equal to the first threshold.

7. The method according to claim 6, characterized in that, The step of determining that the first relay has a malfunction in engaging when the deviation between the first voltage and the second voltage is greater than or equal to a second threshold includes: If the deviation between the first voltage and the second voltage is always greater than or equal to the second threshold within a preset time period, it is determined that the first relay has an abnormal engagement fault.

8. A fault detection device for a relay, characterized in that, An application in a grid-connected system, the grid-connected system including a power converter, the power converter being connected to the power grid via a neutral line and at least one phase line, the neutral line including a first relay and a second relay connected in series, the first relay being connected to the power converter, the second relay being connected to the power grid, and a third relay being provided on the phase line, the device comprising: The control module is used to keep both the second relay and the third relay disconnected, and to control the power converter to output AC voltage so that the first voltage between the first line and the second line reaches a first threshold. The first line is the line between the third relay and the power converter on the first phase line of the at least one phase line, and the second line is the line between the first relay and the power converter on the neutral line. The detection module is used to determine whether the first relay is faulty based on the control state of the first relay and the deviation between the first voltage and the second voltage. The second voltage is the voltage between the first line and the third line. The third line is the line between the first relay and the second relay on the neutral line. The control state is the state of the first relay according to the control, including the open state and the closed state.

9. A grid-connected system, characterized in that, The device includes a power converter connected to the power grid via a neutral line and at least one phase line. The neutral line includes a first relay and a second relay connected in series. The first relay is connected to the power converter, and the second relay is connected to the power grid. A third relay is provided on the phase line. The device also includes a controller for performing the method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, It stores a computer program, which includes program instructions that, when executed by the controller of the grid-connected system, perform the method as described in any one of claims 1 to 7.

Images