A relay detection method, device, apparatus and storage medium

Abstract

The application discloses a relay detection method, device and equipment and a storage medium. Before each relay in a grid-connected inverter is closed, the effective value and the direct current of an inverter voltage of the relay are acquired, and the alternating current of the inverter voltage is acquired based on the effective value and the direct current of the inverter voltage. Then, the first difference operation is performed on the alternating current of the inverter voltage and the effective value of a grid voltage, and the first difference operation result is acquired. Finally, whether the relay is damaged or stuck is judged based on the absolute value of the first difference operation result. The problem that when the relay is detected, whether the relay is damaged or stuck is determined only by the difference between the effective value of the grid voltage and the effective value of the inverter voltage, and the misjudgment condition is prone to occurring is solved, and the misjudgment condition caused by the excessive direct current of the inverter voltage can be effectively avoided.

Description

Technical Field

[0001] This application relates to the field of grid-connected inverter technology, specifically to a relay detection method, device, equipment, and storage medium. Background Technology

[0002] When an inverter is connected to the grid, the relays in it need to be tested to determine if they are damaged or stuck.

[0003] Normally, when testing a relay, since the inverter voltage is 0V before the relay closes, the effective value of the inverter voltage differs significantly from the effective value of the mains voltage. Therefore, the difference between the effective values ​​of the mains voltage and the inverter voltage can be used to determine whether the relay is damaged or stuck. However, if... Figure 1 As shown, if an inverter that is already connected to the grid suddenly loses power and then reconnects to the grid, and its self-test time is short, in this case, due to the presence of the filter capacitor C, the inverter voltage ( Figure 1 The INV voltage in the circuit will generate a large DC current, and an excessive DC current can easily interfere with the detection of the relay.

[0004] Therefore, when testing a relay, relying solely on the difference between the effective value of the mains voltage and the effective value of the inverter voltage to determine whether the relay is damaged or stuck can easily lead to misjudgment. Summary of the Invention

[0005] This application provides a relay testing method, apparatus, device, and storage medium, which solves the technical problem that when testing a relay, the difference between the effective value of the mains voltage and the effective value of the inverter voltage is used to determine whether the relay is damaged or stuck, which is prone to misjudgment.

[0006] On the one hand, a relay detection method is provided, the method comprising:

[0007] Before each relay in the grid-connected inverter is closed, the effective value of the inverter voltage and the DC current of the relay are obtained;

[0008] Based on the effective value and DC quantity of the inverter voltage, the AC quantity of the inverter voltage is obtained;

[0009] Perform a first subtraction operation on the AC quantity of the inverter voltage and the effective value of the grid voltage, and obtain the result of the first subtraction operation;

[0010] Based on the absolute value of the first difference operation result, it is determined whether the relay is damaged or stuck.

[0011] In another aspect, a relay detection device is provided, the device comprising:

[0012] The grid voltage RMS value acquisition module is used to acquire the RMS value of the inverter voltage and DC value of each relay in the grid-connected inverter before the relay is closed.

[0013] An inverter voltage AC quantity acquisition module is used to acquire the AC quantity of the inverter voltage based on the effective value and DC quantity of the inverter voltage.

[0014] The first difference operation result acquisition module is used to perform a first difference operation on the AC quantity of the inverter voltage and the effective value of the grid voltage, and to acquire the first difference operation result.

[0015] The judgment module is used to determine whether the relay is damaged or stuck based on the absolute value of the first difference operation result.

[0016] In one possible implementation, the inverter voltage AC quantity acquisition module is used for:

[0017] Obtain the square of the effective value of the inverter voltage of the relay;

[0018] Obtain the square of the average value of the DC quantity of the inverter voltage;

[0019] Perform a second subtraction operation on the square of the effective value and the square of the average value, and obtain the result of the second subtraction operation;

[0020] The square root operation is performed on the second difference result to obtain the AC value of the inverter voltage of the relay.

[0021] In one possible implementation, the relay detection device further includes:

[0022] An open-loop control module is used to introduce open-loop control before the target relay closes, so as to reduce the voltage difference between the grid voltage and the inverter voltage; the target relay is the last relay to close in the grid-connected inverter.

[0023] In one possible implementation, the open-loop control module is configured to:

[0024] A voltage waveform with the same frequency and phase as the grid voltage is generated at the inverter terminal of the target relay.

[0025] In one possible implementation, the open-loop control module is further configured to:

[0026] The inverter drive action is executed, and based on the inverter switch in the grid-connected inverter, a voltage waveform with the same frequency and phase as the grid voltage is generated at the inverter terminal of the target relay.

[0027] In one possible implementation, the relay detection device further includes:

[0028] A virtual resistor introduction module introduces a virtual resistor at the output terminal of the target relay to reduce the current generated under open-loop control.

[0029] In one possible implementation, the virtual resistor introduction module is used for:

[0030] Obtain sampled values ​​of the bus voltage, inverter current, and grid voltage of the grid-connected inverter;

[0031] The virtual voltage value is obtained based on the virtual resistance and the inverter current;

[0032] The sampled value of the grid voltage is subtracted from the virtual voltage value, and the difference is divided by the bus voltage to obtain the open-loop modulation ratio.

[0033] When the voltage difference between the inverter voltage and the grid voltage is less than a set value, the target relay is closed.

[0034] After the target relay is closed, the current generated under open-loop control is reduced by adjusting the open-loop modulation ratio.

[0035] In another aspect, a computer device is provided, the computer device including a processor and a memory, the memory storing at least one instruction, the at least one instruction being loaded and executed by the processor to implement a relay detection method as described above.

[0036] In another aspect, a computer-readable storage medium is provided, wherein at least one instruction is stored therein, the at least one instruction being loaded and executed by a processor to implement a relay detection method as described above.

[0037] The technical solution provided in this application may include the following beneficial effects:

[0038] Before each relay in the grid-connected inverter closes, the effective value and DC current of the inverter voltage for that relay are first obtained. Based on the effective value and DC current of the inverter voltage, the AC current of the inverter voltage is then obtained. Next, a first subtraction operation is performed between the AC current of the inverter voltage and the effective value of the grid voltage, and the result of the first subtraction operation is obtained. Finally, based on the absolute value of the first subtraction operation result, it is determined whether the relay is damaged or stuck. In the above scheme, extracting the AC current of the inverter voltage and judging whether each relay is damaged or stuck based on the difference between the AC current and the effective value of the grid voltage can effectively avoid misjudgment caused by excessive DC current of the inverter voltage. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of the basic framework of a relay, based on the background art.

[0041] Figure 2 This is a schematic diagram illustrating the ideal closing time of a relay according to an exemplary embodiment.

[0042] Figure 3 This is a schematic diagram illustrating the actual closing time of a relay according to an exemplary embodiment.

[0043] Figure 4 This is a flowchart illustrating a relay detection method according to an exemplary embodiment.

[0044] Figure 5 This is a flowchart illustrating a relay detection method according to an exemplary embodiment.

[0045] Figure 6 This is a flowchart illustrating a method for reducing open-loop control current according to an exemplary embodiment.

[0046] Figure 7 This is a basic framework diagram illustrating the introduction of a virtual resistor according to an exemplary embodiment.

[0047] Figure 8 This is a structural block diagram of a relay detection device according to an exemplary embodiment.

[0048] Figure 9 A structural block diagram of a computer device illustrated in an exemplary embodiment of this application is shown. Detailed Implementation

[0049] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0050] It should be understood that the term "instruction" mentioned in the embodiments of this application can be a direct instruction, an indirect instruction, or an indication of a relationship. For example, A instructing B can mean that A directly instructs B, such as B being able to obtain information through A; it can also mean that A indirectly instructs B, such as A instructing C, so B can obtain information through C; or it can mean that there is a relationship between A and B.

[0051] In the description of the embodiments of this application, the term "correspondence" may indicate that there is a direct or indirect correspondence between two things, or that there is an association between two things, or that there is a relationship of instruction and being instructed, configuration and being configured, etc.

[0052] Figure 1 This is a schematic diagram of the basic framework of a relay, based on the background art. For example... Figure 1 As shown, the basic framework of this relay includes INV (inverter), filter capacitor C, inductor L, and four relays, namely INV-Relay-L (relay near the inverter inductor L line), Gnd-Relay-L (relay near the grid L line), INV-Relay-N (relay near the inverter inductor N line), and Gnd-Relay-N (relay near the grid N line).

[0053] Optionally, before all inverters are connected to the grid, each of the relays must be tested to determine if the relays are damaged or stuck. After testing, the relays are then closed.

[0054] Therefore, when testing a relay to determine if it is damaged or stuck, the presence of the filter capacitor C can cause excessive DC current to interfere with the relay testing. Relying solely on the difference between the effective value of the mains voltage and the effective value of the inverter voltage to determine if the relay is damaged or stuck can easily lead to misjudgment. In this case, the difference between the AC value of the inverter voltage and the effective value of the mains voltage can be extracted as a basis for determining whether the relay is damaged or stuck.

[0055] Optionally, after completing the test, when performing a closing operation on the relay, in order to minimize the inrush current at the moment of relay closing, the existing practice is to control the relay to close at the power grid zero point. However, as... Figure 2 As shown, ideally, if a closing command is triggered at point T2, the relay closing will require a certain amount of time (i.e., Figure 2 In the case of ΔT1), the relay will close at point T1.

[0056] However, the closing delay time of each relay is not fixed and is uncontrollable. For example... Figure 3As shown, since the closing time is uncontrollable, the relay may close at time T3. At this time, the voltage difference across the relay is large, and a large inrush current will be generated when the relay is closed. Therefore, when the relay closes, open-loop control of the relay in the single-phase inverter can be introduced to effectively prevent damage to the circuit caused by excessive inrush current.

[0057] Figure 4 This is a flowchart illustrating a relay detection method according to an exemplary embodiment. Figure 4 As shown, the relay detection method may include the following steps:

[0058] Step S401: Before closing each relay in the grid-connected inverter, obtain the effective value of the inverter voltage and the DC current of that relay.

[0059] In one possible implementation, before the inverter is connected to the grid, each of the relays needs to be tested to determine if the relays are damaged or stuck. During the test, the effective value of the inverter voltage and the DC current corresponding to each relay in the grid-connected inverter are obtained.

[0060] Step S402: Based on the effective value and DC quantity of the inverter voltage, obtain the AC quantity of the inverter voltage.

[0061] In one possible implementation, if an inverter already connected to the grid suddenly loses power and then reconnects, and its self-test time is short, the inverter voltage will generate a large DC current due to the presence of the filter capacitor C. This excessive DC current can easily interfere with the relay detection. To avoid this situation, the AC current of the inverter voltage can be obtained for each relay in the grid-connected inverter, based on the effective value of the inverter voltage and the DC current.

[0062] Step S403: Perform a first difference operation on the AC quantity of the inverter voltage and the effective value of the grid voltage, and obtain the result of the first difference operation.

[0063] In one possible implementation, for each relay in the grid-connected inverter, after obtaining the effective value of the grid voltage corresponding to the relay and the AC quantity of its inverter voltage, a first subtraction operation can be performed on the AC quantity of the inverter voltage and the effective value of the grid voltage, that is, the AC quantity of the inverter voltage is subtracted from the effective value of the grid voltage, and the result (the result of the first subtraction operation) is obtained.

[0064] Step S404: Based on the absolute value of the first difference operation result, determine whether the relay is damaged or stuck.

[0065] In one possible implementation, for each relay in the grid-connected inverter, after obtaining the first difference operation result corresponding to the relay, based on the absolute value of the first difference operation result, it is determined whether the relay corresponding to the first difference operation result is damaged or stuck, so as to realize the determination of damage or sticking of each relay.

[0066] Optionally, when determining whether a relay is damaged or stuck, the determination can be based on a target threshold. For example, if the absolute value of the first difference operation result is less than the target threshold, the corresponding relay is determined to be damaged or stuck. If the absolute value of the first difference operation result is greater than or equal to the target threshold, the corresponding relay is determined not to be damaged or stuck.

[0067] In summary, before each relay in the grid-connected inverter closes, the effective value and DC current of the inverter voltage for that relay are first obtained. Based on the effective value and DC current of the inverter voltage, the AC current of the inverter voltage is then obtained. Next, a first subtraction operation is performed between the AC current of the inverter voltage and the effective value of the grid voltage, and the result of the first subtraction operation is obtained. Finally, based on the absolute value of the result of the first subtraction operation, it is determined whether the relay is damaged or stuck. In the above scheme, extracting the AC current of the inverter voltage and judging whether each relay is damaged or stuck based on the difference between the AC current and the effective value of the grid voltage can effectively avoid misjudgment caused by excessive DC current of the inverter voltage.

[0068] Figure 5 This is a flowchart illustrating a relay detection method according to an exemplary embodiment. Figure 5 As shown, the relay detection method may include the following steps:

[0069] Step S501: Before closing each relay in the grid-connected inverter, obtain the effective value of the inverter voltage and the DC current of that relay.

[0070] Furthermore, under normal circumstances, the voltage and direction of alternating current (AC) change with time. If the heating effect of this AC is equal to that of a DC at a certain voltage, then the DC voltage can be considered the effective value of the AC voltage. Based on this, during testing, the effective value of the inverter voltage and the DC current corresponding to each relay in the grid-connected inverter are first obtained.

[0071] Step S502: Based on the effective value and DC quantity of the inverter voltage, obtain the AC quantity of the inverter voltage.

[0072] In one possible implementation, the square of the effective value of the inverter voltage of the relay is obtained;

[0073] Obtain the square of the average value of the DC quantity of the inverter voltage;

[0074] Perform a second subtraction operation on the square of the effective value and the square of the average value, and obtain the result of the second subtraction operation;

[0075] The square root of the second difference result is then taken to obtain the AC value of the inverter voltage of the relay.

[0076] Furthermore, when testing each relay in the grid-connected inverter, it is necessary not only to obtain the effective value of the grid voltage corresponding to the relay, but also to obtain the AC quantity of the inverter voltage based on the effective value of the inverter voltage and the DC quantity.

[0077] Optionally, the AC value of the relay's inverter voltage can be extracted using the following formula:

[0078]

[0079] Among them, U Inv_AC U represents the AC quantity of the relay's inverter voltage. InvRam U represents the effective value of the inverter voltage. Inv_DC This represents the average value of the DC quantity of the inverter voltage.

[0080] Step S503: Perform a first difference operation on the AC quantity of the inverter voltage and the effective value of the grid voltage, and obtain the result of the first difference operation.

[0081] In one possible implementation, the square root of the square of the effective value of the inverter voltage minus the square of the average value of the DC quantity of the inverter voltage can be used to extract the AC quantity of the inverter voltage. Then, the effective value of the grid voltage is subtracted from the AC quantity of the inverter voltage, and the absolute value of the calculation result (i.e., the first difference operation result mentioned above) can be used as a basis for judging whether the relay is damaged or stuck.

[0082] Step S504: Based on the absolute value of the first difference operation result, determine whether the relay is damaged or stuck.

[0083] In one possible implementation, each relay in the grid-connected inverter is tested using the above method to obtain the absolute value of the first difference operation result corresponding to each relay. Then, based on the absolute value of each first difference operation result, it is determined whether the corresponding relay is damaged or stuck.

[0084] Step S505: Before the target relay closes, open-loop control is introduced to reduce the voltage difference between the grid voltage and the inverter voltage; the target relay is the last relay to close in the grid-connected inverter.

[0085] In one possible implementation, a voltage waveform that is in phase and frequency with the grid voltage is generated at the inverter terminal of the target relay.

[0086] In one possible implementation, an inverter drive action is performed, and based on the inverter switch in the grid-connected inverter, a voltage waveform that is in phase and frequency with the grid voltage is generated at the inverter terminal of the target relay.

[0087] Optionally, after performing damage and sticking detection on each relay in the grid-connected inverter and determining that no relay is damaged or stuck (or after eliminating damaged or stuck relays), to address the issue of excessive inrush current that may be generated when each relay is closed, open-loop control can be implemented on each relay to generate a voltage waveform at the inverter terminal of the target relay that is in phase and frequency with the grid voltage. This voltage waveform reduces the voltage difference between the grid voltage and the inverter voltage, thereby solving the problem of excessive inrush current.

[0088] Furthermore, before closing the last relay, the inverter drive operates, generating a waveform in INV (inverter) that is in phase and frequency with the grid voltage. Since the voltage difference between the grid voltage and the inverter voltage is small, the inrush current will also be relatively small when the relay is closed.

[0089] Step S506: Introduce a virtual resistor at the output terminal of the target relay to reduce the current generated under open-loop control.

[0090] In one possible implementation, sampled values ​​of the bus voltage, inverter current, and grid voltage of the grid-connected inverter are obtained;

[0091] The virtual voltage value is obtained based on the virtual resistance and the inverter current;

[0092] The sampled value of the grid voltage is subtracted from the virtual voltage value, and the difference is divided by the bus voltage to obtain the open-loop modulation ratio.

[0093] When the voltage difference between the inverter voltage and the grid voltage is less than a set value, the target relay is closed.

[0094] After the target relay is closed, the current generated under open-loop control is reduced by adjusting the open-loop modulation ratio.

[0095] Optional, please refer to Figure 6 The flowchart of the method for reducing open-loop control current is shown below. Figure 6 As shown, before the relay (i.e., the target relay mentioned above) closes, an open-loop mode is entered. After entering the open-loop mode, the bus voltage of the grid-connected inverter (i.e., Figure 6The sampled values ​​of the bus voltage, inverter current, and grid voltage are used to calculate the open-loop modulation ratio. This is done when the voltage difference between the inverter voltage and the grid voltage (i.e., the voltage across the grid) is... Figure 6 The Urelay value is less than the set value (i.e., Figure 6 When the Ulimit is reached, a 20ms delay is made to perform a closing operation on the target relay, ending the open-loop mode and the process; when the voltage difference between the inverter voltage and the grid voltage (i.e., Figure 6 The Urelay value is greater than or equal to the set value (i.e., ...). Figure 6 When the Ulimit is called, an error message is displayed after a 2-second delay, and the process ends.

[0096] Furthermore, since an inverter is essentially a Buck circuit, the calculation method for the open-loop INV modulation ratio (i.e., the aforementioned open-loop modulation ratio) can be adopted using the calculation method for a buck circuit.

[0097] Optionally, the open-loop modulation ratio can be obtained using the following formula:

[0098] Duty = U gridRam / U bus ;

[0099] Where Duty represents the open-loop modulation ratio, U gridRam U represents the effective value of the grid voltage. bus This indicates the bus voltage of the grid-connected inverter;

[0100] However, in reality, there may be cases where the grid voltage is not a standard sinusoidal waveform. Therefore, simply dividing the effective value of the grid voltage by U is not sufficient. bus The voltage method can obtain the open-loop modulation ratio using the following formula:

[0101] Duty = U gird / U bus ;

[0102] Among them, U gird This represents the sampled value of the grid voltage.

[0103] Furthermore, in practical applications, after the relay closes, the open-loop control needs to be stopped. However, since the relay is already closed, the INV (inverter) is still operating, and a loop still exists in the circuit, the circuit will continue to perform open-loop control. In this situation, open-loop control will generate current. To suppress this current, a virtual resistor can be introduced.

[0104] Please refer to Figure 7 The basic framework diagram of the virtual resistor shown is as follows: Figure 7As shown, by introducing a virtual resistor, the open-loop modulation ratio is adjusted in real time according to the inverter current, thereby reducing the current introduced by the open loop. This open-loop modulation ratio can be adjusted in real time using the following formula:

[0105] Duty=(U gird -R virctual *I inv ) / U Bus ;

[0106] Among them, R virctual This represents the virtual resistance, I. inv R represents the inverter current of the relay. virctual *I inv This is the virtual voltage value mentioned above.

[0107] In summary, before each relay in the grid-connected inverter closes, the effective value and DC current of the inverter voltage for that relay are first obtained. Based on the effective value and DC current of the inverter voltage, the AC current of the inverter voltage is then obtained. Next, a first subtraction operation is performed between the AC current of the inverter voltage and the effective value of the grid voltage, and the result of the first subtraction operation is obtained. Finally, based on the absolute value of the result of the first subtraction operation, it is determined whether the relay is damaged or stuck. In the above scheme, extracting the AC current of the inverter voltage and judging whether each relay is damaged or stuck based on the difference between the AC current and the effective value of the grid voltage can effectively avoid misjudgment caused by excessive DC current of the inverter voltage.

[0108] Figure 8 This is a structural block diagram illustrating a relay detection device according to an exemplary embodiment. The relay detection device includes:

[0109] The grid voltage RMS value acquisition module 801 is used to acquire the RMS value of the inverter voltage and DC value of each relay in the grid-connected inverter before the relay is closed.

[0110] The inverter voltage AC quantity acquisition module 802 is used to acquire the AC quantity of the inverter voltage based on the effective value and DC quantity of the inverter voltage.

[0111] The first difference operation result acquisition module 803 is used to perform a first difference operation on the AC quantity of the inverter voltage and the effective value of the grid voltage, and to acquire the first difference operation result.

[0112] The judgment module 804 is used to determine whether the relay is damaged or stuck based on the absolute value of the first difference operation result.

[0113] In one possible implementation, the inverter voltage AC quantity acquisition module 802 is further configured to:

[0114] Obtain the square of the effective value of the inverter voltage of the relay;

[0115] Obtain the square of the average value of the DC quantity of the inverter voltage;

[0116] Perform a second subtraction operation on the square of the effective value and the square of the average value, and obtain the result of the second subtraction operation;

[0117] The square root of the second difference result is performed to obtain the AC value of the relay's inverter voltage. In one possible implementation, the relay detection device further includes:

[0118] An open-loop control module is used to introduce open-loop control before the target relay closes, in order to reduce the voltage difference between the grid voltage and the inverter voltage; the target relay is the last relay to close in the grid-connected inverter.

[0119] In one possible implementation, the open-loop control module is used for:

[0120] A voltage waveform with the same frequency and phase as the grid voltage is generated at the inverter terminal of the target relay.

[0121] In one possible implementation, the open-loop control module is further configured to:

[0122] The inverter drive action is executed, and based on the inverter switch in the grid-connected inverter, a voltage waveform with the same frequency and phase as the grid voltage is generated at the inverter terminal of the target relay.

[0123] In one possible implementation, the relay detection device further includes:

[0124] A virtual resistor introduction module introduces a virtual resistor at the output of the target relay to reduce the current generated under open-loop control.

[0125] In one possible implementation, the virtual resistor is introduced into the module for:

[0126] Obtain sampled values ​​of the bus voltage, inverter current, and grid voltage of the grid-connected inverter;

[0127] The virtual voltage value is obtained based on the virtual resistance and the inverter current;

[0128] The sampled value of the grid voltage is subtracted from the virtual voltage value, and the difference is divided by the bus voltage to obtain the open-loop modulation ratio.

[0129] When the voltage difference between the inverter voltage and the grid voltage is less than a set value, the target relay is closed.

[0130] After the target relay is closed, the current generated under open-loop control is reduced by adjusting the open-loop modulation ratio.

[0131] In summary, before each relay in the grid-connected inverter closes, the effective value and DC current of the inverter voltage for that relay are first obtained. Based on the effective value and DC current of the inverter voltage, the AC current of the inverter voltage is then obtained. Next, a first subtraction operation is performed between the AC current of the inverter voltage and the effective value of the grid voltage, and the result of the first subtraction operation is obtained. Finally, based on the absolute value of the result of the first subtraction operation, it is determined whether the relay is damaged or stuck. In the above scheme, extracting the AC current of the inverter voltage and judging whether each relay is damaged or stuck based on the difference between the AC current and the effective value of the grid voltage can effectively avoid misjudgment caused by excessive DC current of the inverter voltage.

[0132] Figure 9 A structural block diagram of a computer device according to an exemplary embodiment of this application is shown. The computer device includes a memory and a processor. The memory stores a computer program, which, when executed by the processor, implements a relay detection method as described above.

[0133] The processor can be a central processing unit (CPU). It can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or combinations thereof.

[0134] Memory, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs, non-transitory computer-executable programs, and modules, such as the program instructions / modules corresponding to the methods in the embodiments of this invention. The processor executes various functional applications and data processing by running the non-transitory software programs, instructions, and modules stored in the memory, thereby implementing the methods described in the above embodiments.

[0135] The memory may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created by the processor, etc. Furthermore, the memory may include high-speed random access memory and non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, the memory may optionally include memory remotely located relative to the processor, which can be connected to the processor via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0136] One embodiment of this application also provides a computer storage medium for storing a computer program, which, when executed by a processor, implements a relay detection method as described above.

[0137] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0138] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A relay detection method, characterized in that, The method includes: Before each relay in the grid-connected inverter is closed, the effective value of the inverter voltage and the DC current of the relay are obtained. Based on the effective value and DC quantity of the inverter voltage, the AC quantity of the inverter voltage is obtained; Perform a first subtraction operation on the AC quantity of the inverter voltage and the effective value of the grid voltage, and obtain the result of the first subtraction operation; Based on the absolute value of the first difference operation result, determine whether the relay is damaged or stuck. The step of obtaining the AC quantity of the inverter voltage based on the effective value and DC quantity of the inverter voltage includes: Obtain the square of the effective value of the inverter voltage of the relay; Obtain the square of the average value of the DC quantity of the inverter voltage; Perform a second subtraction operation on the square of the effective value and the square of the average value, and obtain the result of the second subtraction operation; The square root operation is performed on the second difference result to obtain the AC value of the inverter voltage of the relay.

2. The method according to claim 1, characterized in that, After determining whether the relay is damaged or stuck, the method further includes: Before the target relay closes, open-loop control is introduced to reduce the voltage difference between the grid voltage and the inverter voltage; the target relay is the last relay to close in the grid-connected inverter.

3. The method according to claim 2, characterized in that, The imported open-loop control includes: A voltage waveform with the same frequency and phase as the grid voltage is generated at the inverter terminal of the target relay.

4. The method according to claim 3, characterized in that, The step of generating a voltage waveform with the same frequency and phase as the grid voltage at the inverter terminal of the target relay includes: The inverter drive action is executed, and based on the inverter switch in the grid-connected inverter, a voltage waveform with the same frequency and phase as the grid voltage is generated at the inverter terminal of the target relay.

5. The method according to claim 4, characterized in that, Before the target relay closes, the method further includes: A virtual resistor is introduced at the output of the target relay to reduce the current generated under open-loop control.

6. The method according to claim 5, characterized in that, The method of reducing the current generated under open-loop control includes: Obtain sampled values ​​of the bus voltage, inverter current, and grid voltage of the grid-connected inverter; The virtual voltage value is obtained based on the virtual resistance and the inverter current; The sampled value of the grid voltage is subtracted from the virtual voltage value, and the difference is divided by the bus voltage to obtain the open-loop modulation ratio. When the voltage difference between the inverter voltage and the grid voltage is less than a set value, the target relay is closed. After the target relay is closed, the current generated under open-loop control is reduced by adjusting the open-loop modulation ratio.

7. A relay detection device, characterized in that, The device includes: The grid voltage RMS value acquisition module is used to acquire the RMS value of the inverter voltage and DC value of each relay in the grid-connected inverter before the relay is closed. An inverter voltage AC quantity acquisition module is used to acquire the AC quantity of the inverter voltage based on the effective value and DC quantity of the inverter voltage. The acquisition of the AC quantity of the inverter voltage based on the effective value and DC quantity includes: acquiring the square of the effective value of the inverter voltage of the relay; acquiring the square of the average value of the DC quantity of the inverter voltage; performing a second subtraction operation on the square of the effective value and the square of the average value, and acquiring the result of the second subtraction operation; and performing a square root operation on the result of the second subtraction operation to acquire the AC quantity of the inverter voltage of the relay. The first difference operation result acquisition module is used to perform a first difference operation on the AC quantity of the inverter voltage and the effective value of the grid voltage, and to acquire the first difference operation result. The judgment module is used to determine whether the relay is damaged or stuck based on the absolute value of the first difference operation result.

8. A computer device, characterized in that, The computer device includes a processor and a memory, the memory storing at least one instruction, which is loaded and executed by the processor to implement a relay detection method as described in any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that, The storage medium stores at least one instruction, which is loaded and executed by a processor to implement a relay detection method as described in any one of claims 1 to 6.

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