Inverter fault diagnosis method, device and system

Abstract

The present application relates to the technical field of inverter fault diagnosis, and specifically to an inverter fault diagnosis method, device and system, the method comprising: obtaining three-phase current data at each moment of the inverter output in each cycle; obtaining the positive wave peak of any phase in each cycle; determining the wave peak abnormality coefficient of any phase current in each cycle; determining the wave peak area ratio of each positive wave peak of any phase in each cycle; determining the waveform abnormality coefficient of any phase current in each cycle; determining the current abnormality coefficient of any phase current in each cycle; determining the fault sensitivity of any phase current in each cycle; and performing fault diagnosis on the inverter based on the fault sensitivity. The present application can detect the fault of the inverter in real time, improve the sensitivity of the inverter fault diagnosis, so as to perform fault detection more accurately.

Description

Technical Field

[0001] The present application relates to the technical field of inverter fault diagnosis, and in particular to an inverter fault diagnosis method, device and system. Background Art

[0002] As a key device of modern new energy technology, the inverter is the core device for realizing the conversion between DC and AC, and plays a vital role in the photovoltaic power generation system. However, in the long-term operation process, due to the influence of various internal and external factors, the inverter will inevitably have fault problems. These faults will not only affect the stable operation of the photovoltaic power generation system, but also may lead to a decrease in energy conversion efficiency and even cause safety accidents. Therefore, it is particularly important to perform timely and accurate fault diagnosis on the inverter.

[0003] The main circuit of the inverter is mainly composed of multiple insulator bipolar transistors (IGBTs), and the high frequency of IGBT switching on and off during operation can cause the inverter to fail. The main fault type of the inverter is open circuit fault, which can cause unstable operation of the photovoltaic power generation system, output current distortion, and even interruption. However, the traditional fault diagnosis method based on signal processing has low sensitivity in the early stage of fault diagnosis of single-tube open circuit fault of the inverter power tube, and the real-time performance of fault diagnosis in actual applications is poor, and it cannot accurately reflect the operating status of the inverter in a timely manner. Summary of the invention

[0004] In order to solve the above technical problems, a method, device and system for diagnosing inverter faults are provided to solve the existing problems.

[0005] The solution to the technical problem of the present application is to provide an inverter fault diagnosis method, device and system, including the following steps:

[0006] In a first aspect, an embodiment of the present application provides a method for diagnosing an inverter fault, the method comprising the following steps:

[0007] Obtain the three-phase current data of the inverter output at each moment in each cycle;

[0008] Based on the three-phase current data, the positive peak of any phase in each cycle is obtained; according to the interval between adjacent positive peaks of any phase in each cycle, the peak abnormality coefficient of any phase current in each cycle is determined;

[0009] Determine the peak area ratio of each positive peak of any phase in each cycle according to the symmetry of the left and right integrated areas of each positive peak of any phase in each cycle; analyze the difference in the area and amplitude of the positive peak between any phase in each cycle and the standard current waveform, and determine the waveform abnormality coefficient of the current of any phase in each cycle in combination with the peak area ratio;

[0010] Based on the peak abnormality coefficient and the waveform abnormality coefficient, determine the current abnormality coefficient of any phase current in each cycle; according to the difference between each two-phase current in each cycle, combined with the current abnormality coefficient, determine the fault sensitivity of any phase current in each cycle;

[0011] Based on the fault sensitivity, fault diagnosis is performed on the inverter.

[0012] Preferably, obtaining the positive peak of any phase in each cycle includes:

[0013] Calculate the absolute value of the three-phase current at each moment in each cycle and record it as the forward current;

[0014] The peak values ​​of the forward current of any phase at all times in each cycle are obtained and recorded as forward peak values.

[0015] Preferably, determining the peak abnormality coefficient of any phase current in each cycle includes:

[0016] Calculate the time interval between the corresponding moment of each positive wave peak of any phase in each cycle and the corresponding moment of the previous positive wave peak, and record it as the interval duration of each positive wave peak;

[0017] The average of the interval durations of all positive wave peaks of any phase in each cycle is taken as the wave peak abnormality coefficient of any phase current in each cycle.

[0018] Preferably, determining the peak area ratio of each positive peak of any phase in each cycle includes:

[0019] The forward currents at each moment of any phase in each cycle and the corresponding forward currents are formed into a two-dimensional array; curve fitting is performed on all the two-dimensional arrays of any phase in each cycle to obtain a fitting curve;

[0020] The integral areas under the fitting curves between the corresponding moments of each positive wave peak of any phase in each cycle and the adjacent zero-point currents on its left and right are recorded as the left peak area and the right peak area of ​​each positive wave peak;

[0021] If the left peak area is greater than the right peak area, the ratio of the left peak area to the right peak area is used as the peak area ratio of each positive peak in any phase in each cycle; otherwise, the ratio of the right peak area to the left peak area is used as the peak area ratio of each positive peak in any phase in each cycle.

[0022] Preferably, the determining of the waveform abnormality coefficient of any phase current in each cycle includes:

[0023] The sum of the left peak area and the right peak area of ​​each positive peak of any phase in each cycle is taken as the waveform area of ​​each positive peak;

[0024] Based on the three-phase currents at each moment in a historical cycle when the inverter is not faulty, the positive wave peaks of the forward current of any phase at all moments in a historical cycle are obtained; the average of the waveform areas of all positive wave peaks of any phase in a historical cycle is used as the standard area;

[0025] Calculate the mean amplitude of all positive wave peaks in any phase in a historical cycle as the standard amplitude;

[0026] The difference between the waveform area of ​​each positive wave peak of any phase in each cycle and the standard area is recorded as the area difference of each positive wave peak;

[0027] The difference between the amplitude corresponding to each positive wave peak of any phase in each cycle and the standard amplitude is recorded as the amplitude difference of each positive wave peak;

[0028] The product of the peak area ratio, the amplitude difference and the area difference of each positive peak is calculated, and the sum of the products of all positive peaks of any phase in each cycle is taken as the waveform abnormality coefficient of any phase current in each cycle.

[0029] Preferably, the current anomaly coefficient of any phase current in each cycle is the product of the peak anomaly coefficient and the waveform anomaly coefficient.

[0030] Preferably, determining the fault sensitivity of any phase current in each cycle includes:

[0031] The cumulative sum of the distances between all currents of any two phases at all times in each cycle is calculated, and the product of the cumulative sum and the current anomaly coefficient is used as the fault sensitivity of any phase current in each cycle.

[0032] Preferably, the performing fault diagnosis on the inverter includes:

[0033] When there is no fault in the inverter, the average value and standard deviation of the fault sensitivity of any phase current in all historical cycles are calculated;

[0034] Based on the average value and the standard deviation, according to the Laida criterion, a threshold interval of any phase current is obtained;

[0035] If the fault sensitivity of any phase current in each cycle is not distributed in the threshold range, a single-tube open-circuit fault occurs in the inverter; otherwise, a single-tube open-circuit fault does not occur in the inverter.

[0036] In a second aspect, an embodiment of the present application further provides an inverter fault diagnosis device, wherein a computer program is stored in the device, and when the computer program is executed by a processor, the steps of any one of the above-mentioned inverter fault diagnosis methods are implemented.

[0037] In a third aspect, an embodiment of the present application further provides an inverter fault diagnosis system, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor implements the steps of any one of the above-mentioned inverter fault diagnosis methods when executing the computer program.

[0038] This application has at least the following beneficial effects:

[0039] Based on the three-phase current data, the present application obtains the positive peak of any phase in each cycle; according to the interval between adjacent positive peaks of any phase in each cycle, the peak abnormality coefficient of any phase current in each cycle is determined, which has the beneficial effect of considering the interval between adjacent peaks of the phase current, analyzing the possibility of abnormality in the corresponding phase current waveform, so as to reflect the possibility of inverter failure; according to the symmetry of the left and right integrated areas of each positive peak of any phase in each cycle, the peak area ratio of each positive peak of any phase in each cycle is determined, which has the beneficial effect of considering the symmetry of the corresponding phase current peak, and then explaining the degree of waveform asymmetry, so as to reflect the possibility of inverter failure; analyzing the difference in the area and amplitude of the positive peak between any phase and the standard current waveform in each cycle, and combining the peak area ratio, determining the waveform abnormality coefficient of any phase current in each cycle, which has The beneficial effect is that the difference between the current waveform in each cycle and the current waveform when no fault occurs is taken into account to reflect the degree of deviation of the current waveform from the sine wave in the corresponding cycle, and then reflect the fault condition of the inverter. Based on the peak abnormality coefficient and the waveform abnormality coefficient, the current abnormality coefficient of any phase current in each cycle is determined. The beneficial effect is that the abnormal degree of the inverter output current is further explained in combination with the changes in the peak and the waveform; according to the difference between each two-phase current in each cycle, combined with the current abnormality coefficient, the fault sensitivity of any phase current in each cycle is determined; based on the fault sensitivity, the inverter is diagnosed. The beneficial effect is that the difference between the three-phase currents is taken into account to reflect the possibility of a single power tube open circuit fault in the inverter, and the inverter fault can be detected in real time, thereby improving the sensitivity of the inverter fault diagnosis so as to more accurately detect the fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] An inverter fault diagnosis method of the present application is further described in detail below with reference to the accompanying drawings.

[0041] Figure 1 A flowchart of a method for diagnosing inverter faults provided in an embodiment of the present application;

[0042] Figure 2 A schematic diagram of the circuit structure of a three-phase inverter provided in an embodiment of the present application;

[0043] Figure 3 A schematic diagram of the change of the A-phase current output by the inverter provided in an embodiment of the present application;

[0044] Figure 4 A flowchart of the steps of a method for obtaining a peak abnormality coefficient of any phase current in each cycle provided in an embodiment of the present application;

[0045] Figure 5A flowchart of the steps of a method for obtaining a waveform anomaly coefficient of any phase current in each cycle provided in an embodiment of the present application. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solution and advantages of the present application more clear, the following is a further detailed description of an inverter fault diagnosis method, device and system proposed in the present application in combination with the accompanying drawings and implementation examples. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0047] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0048] See also Figure 1 , which shows a flowchart of a method for diagnosing inverter faults provided by an embodiment of the present application, the method comprising the following steps:

[0049] Step 1: Obtain the three-phase current data of the inverter output at each moment in each cycle.

[0050] The photovoltaic grid-connected inverter is the core component of the entire photovoltaic power generation system. Its main function is to convert photovoltaic cells into AC power that meets the grid connection requirements and then send it to the power grid. However, open circuit faults may occur during the operation of the inverter. Therefore, by performing fault analysis on the output current of the three-phase inverter, first, install the current sensor at the output end of the three-phase inverter, collect the three-phase current of the three-phase inverter, set the collection frequency to f, and the collection period to t, filter the collected current signal, and obtain the three-phase current data output by the inverter at each moment of each cycle.

[0051] Preferably, in this embodiment, the acquisition frequency is set to 100 Hz and the acquisition period is 1 s. As other implementation modes, the implementer can set them according to the actual situation. Secondly, median filtering is used for filtering, wherein the median filtering algorithm is a well-known technology and will not be described here. As other implementation modes, the implementer can adopt other methods of the prior art, such as, mean filtering algorithm, etc. This embodiment does not impose any special restrictions on this.

[0052] At this point, the three-phase current data at each moment in each cycle is obtained.

[0053] Step 2: based on the three-phase current data, obtain the positive peak of any phase in each cycle; and determine the peak abnormality coefficient of any phase current in each cycle according to the interval between adjacent positive peaks of any phase in each cycle.

[0054] During the operation of the inverter, abnormal operating conditions such as excessive load or short circuit may occur, which may cause the IGBT in the inverter to fail to operate normally, resulting in the performance of the IGBT component being degraded, and in severe cases, it may be burned. Since the short-circuit fault of the three-phase inverter will further transform into an open-circuit fault, the open-circuit fault caused by damage to the IBGT in the inverter is diagnosed.

[0055] During normal operation of the inverter, the three-phase inverter can realize the conversion from DC to AC and output three-phase current. The circuit structure diagram of the three-phase inverter provided in this embodiment is as shown in FIG. Figure 2 As shown, Indicates the DC side voltage; Indicates the power switch tube; Represents a freewheeling diode; represents the load resistance; Represents the filter inductance; Indicates the imaginary midpoint of the DC power supply.

[0056] Under normal circumstances, the three-phase current output maintains a sinusoidal waveform, and the phase difference between the three-phase currents is 120°. When a single-tube open-circuit fault occurs in a three-phase inverter, the three-phase current output by the three-phase inverter will change, and the change forms of the three-phase currents are different. For example, when When an open-circuit fault occurs in the power tube IGBT, the positive current of the A-phase current output by the inverter disappears, the negative current waveform changes abnormally, and the shapes of the B-phase and C-phase currents also change abnormally, but the waveforms of the three-phase currents still maintain periodic changes.

[0057] Furthermore, the schematic diagram of the change of the A-phase current output by the inverter provided in this embodiment is as follows: Figure 3 As shown, the horizontal axis is time and the vertical axis is current. Figure 3 It can be seen that after 0.2s, the current waveform becomes abnormal and the forward current disappears.

[0058] Based on the above analysis, if a single-tube open-circuit fault occurs in the inverter power tube, the forward current of a certain phase will disappear and the waveform of the negative current will change abnormally. Therefore, the waveform changes of each phase current in the inverter are analyzed to reflect the possibility of a single-phase open-circuit fault in the inverter.

[0059] Furthermore, the step flow chart of the method for obtaining the peak abnormal coefficient of any phase current in each cycle provided in the embodiment of the present application is as follows: Figure 4 shown.

[0060] First, analyze the peak of each phase current, specifically:

[0061] Calculate the absolute value of the three-phase current at each moment in each cycle and record it as the forward current;

[0062] Obtain the peak value of the forward current of any phase at all times in each cycle, and record it as each forward peak value;

[0063] Preferably, in this embodiment, an automatic multi-scale peak search algorithm is used to obtain the positive peak, wherein the automatic multi-scale peak search algorithm is a well-known technology and will not be described in detail here. As other implementation methods, the implementer may adopt other methods of the prior art, such as the differential method, etc. This embodiment does not impose any special restrictions on this.

[0064] Furthermore, after the inverter fails, due to the lack of forward current in the original current, the interval time between adjacent forward peaks in each phase current signal changes, and the number of forward peaks of the forward current at all times decreases. Therefore, the changes in adjacent forward peaks in the forward current signal of any phase in each cycle are analyzed to determine the peak abnormality coefficient, which is specifically:

[0065] Calculate the time interval between the corresponding moment of each positive wave peak of any phase in each cycle and the corresponding moment of the previous positive wave peak, and record it as the interval length of each positive wave peak;

[0066] The average of the interval durations of all positive wave peaks of any phase in each cycle is taken as the wave peak abnormality coefficient of the current of any phase in each cycle;

[0067] It should be noted that due to the open circuit fault of the inverter, the forward current disappears and the current waveform changes abnormally, so the time interval between adjacent forward peaks increases. That is, the larger the obtained peak abnormality coefficient, the greater the possibility that the waveform of the corresponding phase current is abnormal, which in turn reflects the greater possibility of inverter failure.

[0068] At this point, the peak abnormality coefficient of any phase current in each cycle is obtained.

[0069] Step 3, determine the peak area ratio of each positive peak of any phase in each cycle according to the symmetry of the left and right integrated areas of each positive peak of any phase in each cycle; analyze the difference in the area and amplitude of the positive peak between any phase in each cycle and the standard current waveform, and determine the waveform abnormality coefficient of the current of any phase in each cycle in combination with the peak area ratio.

[0070] Furthermore, since the waveform of each phase current is a sinusoidal waveform under normal conditions, the waveforms of each phase current are highly symmetrical. However, due to an open circuit fault in the inverter, the waveform of each phase current no longer maintains a sinusoidal waveform, which in turn causes the current of each phase to no longer maintain a symmetrical shape, and the area and amplitude of the sinusoidal waveform will also change.

[0071] Further, the step flow chart of the method for obtaining the waveform abnormality coefficient of any phase current in each cycle provided by the embodiment of the present application is as follows: Figure 5 shown.

[0072] Based on the above analysis, the waveform abnormality coefficient is determined by analyzing the difference in the area and amplitude of each phase current waveform, which is:

[0073] The forward currents at each moment of any phase in each cycle and the corresponding forward currents are formed into a two-dimensional array; curve fitting is performed on all the two-dimensional arrays of any phase in each cycle to obtain a fitting curve;

[0074] The integral areas under the fitting curves between the corresponding moments of each positive wave peak of any phase in each cycle and the adjacent zero-point currents on its left and right are recorded as the left peak area and the right peak area of ​​each positive wave peak;

[0075] The sum of the left peak area and the right peak area of ​​each positive wave peak is taken as the waveform area of ​​each positive wave peak;

[0076] If the left peak area is greater than the right peak area, the ratio of the left peak area to the right peak area is used as the peak area ratio of each positive peak; otherwise, the ratio of the right peak area to the left peak area is used as the peak area ratio of each positive peak;

[0077] The three-phase currents at each moment in a historical cycle when the inverter has no faults are collected, the absolute values ​​of the three-phase currents at each moment in a historical cycle are taken, recorded as the forward current, and the forward peaks of the forward currents of any phase at all moments in a historical cycle are obtained. The above method is used to calculate the average value of the waveform areas of all the forward peaks of any phase in a historical cycle as the standard area;

[0078] Calculate the mean amplitude of all positive wave peaks in any phase in a historical cycle as the standard amplitude;

[0079] The difference between the waveform area of ​​each positive wave peak of any phase in each cycle and the standard area is recorded as the area difference;

[0080] Preferably, in this embodiment, the absolute value of the difference between the waveform area of ​​each positive wave peak and the standard area is recorded as the area difference.

[0081] The difference between the amplitude corresponding to each positive wave peak of any phase in each cycle and the standard amplitude is recorded as the amplitude difference;

[0082] Preferably, in this embodiment, the absolute value of the difference between the amplitude corresponding to each positive wave peak of any phase in each cycle and the standard amplitude is recorded as the amplitude difference.

[0083] Calculate the product of the peak area ratio, the amplitude difference and the area difference of each positive peak of any phase in each cycle, and take the sum of the products of all positive peaks of any phase in each cycle as the waveform abnormality coefficient of the current of any phase in each cycle;

[0084] Preferably, in this embodiment, the calculation formula for the waveform abnormality coefficient of any phase current in each cycle is: ,in, For the In the cycle The waveform anomaly coefficient of the phase current, For the In the cycle Phase The peak area ratio of the positive peaks, For the In the cycle Phase The amplitude of the positive peak, For the In the cycle Phase The waveform area of ​​the positive peak, is the standard area, is the standard amplitude, For the In the cycle The number of all positive peaks in the phase; secondly, is the amplitude difference, The difference is in area.

[0085] It should be noted that the larger the peak area ratio is, the worse the waveform symmetry of the corresponding positive peak is, and the greater the possibility that the current waveform deviates from the sine wave is. Secondly, the greater the difference between the waveform area of ​​each positive peak and the standard area, and the amplitude and the standard amplitude, that is, the greater the area difference and the amplitude difference, the greater the degree of deviation of the current waveform from the sine wave, and the larger the obtained waveform anomaly coefficient, which means that the waveform of the corresponding phase current deviates more from the sine wave, reflecting the abnormal waveform of the corresponding phase current.

[0086] At this point, the waveform abnormality coefficient of any phase current in each cycle is obtained.

[0087] Step 4, based on the peak abnormality coefficient and the waveform abnormality coefficient, determine the current abnormality coefficient of any phase current in each cycle; according to the difference between each two-phase current in each cycle, combined with the current abnormality coefficient, determine the fault sensitivity of any phase current in each cycle; based on the fault sensitivity, perform fault diagnosis on the inverter.

[0088] Further, based on the peak abnormality coefficient and the waveform abnormality coefficient, the current abnormality coefficient is determined, specifically:

[0089] The product of the peak abnormality coefficient and the waveform abnormality coefficient is used as the current abnormality coefficient of any phase current in each cycle.

[0090] It should be noted that, the larger the current abnormality coefficient is, the greater the possibility of an open circuit fault occurring in the inverter power tube is.

[0091] Furthermore, in normal operation of the inverter, the amplitudes and frequencies of the currents of each phase are equal, and the phases are 120 degrees apart, so the variation trends of the three-phase currents in each cycle are slightly different; however, when an open circuit fault occurs in the inverter, the amplitudes, frequencies, and phases of the three-phase currents change, resulting in large differences in the variation trends of the three-phase currents. Therefore, the differences between the two-phase currents are analyzed to determine the fault sensitivity, specifically:

[0092] Calculate the cumulative sum of the distances between all the currents of any two phases at all times in each cycle, and use the product of the cumulative sum and the current anomaly coefficient as the fault sensitivity of any phase current in each cycle;

[0093] Preferably, in this embodiment, the cumulative sum of the DTW distances of the currents of all two arbitrary phases at all times in each cycle is calculated. As other implementation methods, the implementer may adopt other methods of the prior art, such as Euclidean distance, etc., and this embodiment does not impose any special restrictions on this.

[0094] Preferably, in this embodiment, the calculation formula for the fault sensitivity of any phase current in each cycle is: ,in, For the In the cycle Fault sensitivity of phase current, For the In the cycle The current anomaly coefficient of the phase current, For the In the cycle The current of each phase at all times, For the In the cycle The current of each phase at all times, Indicates the calculated distance.

[0095] It should be noted that when an open circuit fault occurs in the inverter, the current anomaly coefficient will increase abnormally; secondly, the greater the distance between any two phase currents, the greater the resulting fault sensitivity, indicating that the possibility of inverter failure in the corresponding period is greater.

[0096] Further, based on the fault sensitivity, the inverter is diagnosed with a fault, specifically:

[0097] When there is no fault in the inverter, the mean and standard deviation of the fault sensitivity of any phase current in all historical cycles are calculated;

[0098] Based on the mean value and the standard deviation, and according to the Laida criterion, a threshold interval of any phase current is obtained;

[0099] It should be noted that the Laida criterion, i.e., the 3σ criterion, is a well-known technology. For ease of understanding, it is assumed that the mean value of the fault sensitivity of the r-th phase current in all historical cycles is , the standard deviation of the fault sensitivity of the rth phase current in all historical cycles is , then the threshold interval of the rth phase current is .

[0100] If the fault sensitivity of any phase current in each cycle is not distributed within the threshold interval, a single-tube open circuit fault occurs in the inverter; if the fault sensitivity of all phase currents in each cycle is distributed within the threshold interval of the corresponding phase current, no single-tube open circuit fault occurs in the inverter.

[0101] When a single-tube open-circuit fault occurs in the inverter, a fault alarm signal is promptly issued to enable timely maintenance of the inverter.

[0102] An embodiment of the present application further provides an inverter fault diagnosis device, wherein a computer program is stored in the device, and when the computer program is executed by a processor, the steps of any one of the above-mentioned inverter fault diagnosis methods are implemented.

[0103] Based on the same inventive concept as the above method, an embodiment of the present application also provides an inverter fault diagnosis system, including a memory, a processor, and a computer program stored in the memory and running on the processor, and when the processor executes the computer program, the steps of any one of the above-mentioned inverter fault diagnosis methods are implemented.

[0104] It should be understood that although Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0105] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0106] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the present application. It should be pointed out that, for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application without departing from the content of the technical solution of the present application, shall fall within the protection scope of the technical solution of the present application.

Claims

1. A method for diagnosing inverter faults, characterized in that: The method comprises the following steps: Obtain the three-phase current data of the inverter output at each moment in each cycle; Based on the three-phase current data, the forward current and the forward peak of any phase in each cycle are obtained; the time interval difference between all the forward peaks of any phase in each cycle and the previous forward peak is averaged as the peak abnormality coefficient of the current of any phase in each cycle; Fit all the moments of any phase in each cycle and their corresponding currents to obtain a fitting curve, and obtain the left peak area and the right peak area of ​​each positive wave peak according to the fitting curve; the ratio of the larger area to the smaller area is taken as the peak area ratio of the positive wave peak; the average of the sum of the left peak area and the right peak area of ​​all positive wave peaks in a historical cycle when no fault occurs is taken as the standard area, and the average of the amplitudes of all positive wave peaks in the historical cycle is taken as the standard amplitude; the difference between the peak area of ​​all wave peaks in any phase in each cycle and the standard area, the difference between the corresponding amplitude of the positive wave peak and the standard amplitude, and the product of the peak area ratio are taken as the waveform abnormality coefficient of the current of any phase; Based on the product of the peak abnormality coefficient and the waveform abnormality coefficient, the current abnormality coefficient of any phase current in each cycle is used; the cumulative sum of the distances between all the currents of any two phases at all times in each cycle is calculated, and the product of the cumulative sum and the current abnormality coefficient is used as the fault sensitivity of any phase current in each cycle; Based on the fault sensitivity, performing fault diagnosis on the inverter; The performing fault diagnosis on the inverter includes: When there is no fault in the inverter, the average value and standard deviation of the fault sensitivity of any phase current in all historical cycles are calculated; Based on the average value and the standard deviation, according to the Laida criterion, a threshold interval of any phase current is obtained; If the fault sensitivity of any phase current in each cycle is not distributed in the threshold range, a single-tube open-circuit fault occurs in the inverter; otherwise, a single-tube open-circuit fault does not occur in the inverter.

2. The inverter fault diagnosis method according to claim 1, characterized in that: The obtaining of the forward current and the forward peak of any phase in each cycle comprises: Calculate the absolute value of the three-phase current at each moment in each cycle and record it as the forward current; The peak values ​​of the forward current of any phase at all times in each cycle are obtained and recorded as forward peak values.

3. The inverter fault diagnosis method according to claim 2, characterized in that: The method for obtaining the peak area ratio comprises: The forward currents at each moment of any phase in each cycle and the corresponding forward currents are formed into a two-dimensional array; curve fitting is performed on all the two-dimensional arrays of any phase in each cycle to obtain a fitting curve; The integral areas under the fitting curves between the corresponding moments of each positive wave peak of any phase in each cycle and the adjacent zero-point currents on its left and right are recorded as the left peak area and the right peak area of ​​each positive wave peak; If the left peak area is greater than the right peak area, the ratio of the left peak area to the right peak area is used as the peak area ratio of each positive peak in any phase in each cycle; otherwise, the ratio of the right peak area to the left peak area is used as the peak area ratio of each positive peak in any phase in each cycle.

4. The inverter fault diagnosis method according to claim 3, characterized in that: The method for obtaining the waveform abnormality coefficient of any phase current includes: The sum of the left peak area and the right peak area of ​​each positive peak of any phase in each cycle is taken as the waveform area of ​​each positive peak; Based on the three-phase currents at each moment in a historical cycle when the inverter is not faulty, the positive wave peaks of the forward current of any phase at all moments in a historical cycle are obtained; the average of the waveform areas of all positive wave peaks of any phase in a historical cycle is used as the standard area; Calculate the mean amplitude of all positive wave peaks in any phase in a historical cycle as the standard amplitude; The difference between the waveform area of ​​each positive wave peak of any phase in each cycle and the standard area is recorded as the area difference of each positive wave peak; The difference between the amplitude corresponding to each positive wave peak of any phase in each cycle and the standard amplitude is recorded as the amplitude difference of each positive wave peak; The product of the peak area ratio, the amplitude difference and the area difference of each positive peak is calculated, and the sum of the products of all positive peaks of any phase in each cycle is taken as the waveform abnormality coefficient of any phase current in each cycle.

5. An inverter fault diagnosis device, wherein a computer program is stored in the device, characterized in that: When the computer program is executed by a processor, the steps of an inverter fault diagnosis method as described in any one of claims 1 to 4 are implemented.

6. An inverter fault diagnosis system, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the inverter fault diagnosis method as described in any one of claims 1 to 4 are implemented.

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