Load testing method and system for large-scale frequency converter system, and medium

Abstract

The invention relates to the technical field of frequency converter load testing, in particular to a load testing method and system for a large-scale frequency converter system and a medium, and the method comprises the steps: determining an output torque step length and an output frequency step length of a current working condition point; based on the output torque, the output frequency, the output torque step length, the output frequency step length and the output frequency of the current working condition point, the output torque and the output frequency of the next working condition point are determined, and when the output frequency and the output torque of the next working condition point exceed the preset output frequency and the preset output torque respectively, the current working condition point is determined. And counting all the working condition points traversed in the load test area, and carrying out load test on the test frequency converter based on the total harmonic distortion coefficient of all the working condition points. By comprehensively considering the working performance difference of the frequency converter caused by the output frequency and the load change, the efficiency and the reliability of the frequency converter load test are improved.

Description

Technical Field

[0001] The present application relates to the technical field of inverter load testing, and in particular to a load testing method, system, and medium for large-scale inverter systems. Background Art

[0002] Motors are widely used in various aspects of industrial production. Controlling motors with frequency converters not only improves motor performance but also reduces energy consumption and increases system efficiency. Furthermore, depending on the application, frequency converters with different voltage levels and control modes can be configured to achieve optimal motor drive control, ensuring optimal frequency converter system operation. During the mass production phase, load testing of frequency converter systems is a key test process for verifying frequency converter system performance before shipment.

[0003] Large-scale inverters operate under a wide range of conditions. Load testing only for specific conditions fails to fully assess the inverter's performance under different loads and frequencies. This incomplete inverter operating condition testing can lead to potential issues remaining undetected, impacting the inverter's actual performance after shipment. To address this issue, existing technologies have integrated load simulation optimization algorithms with measurement optimization algorithms to improve testing performance for different inverter models. However, this existing technology fails to account for performance differences in the inverter caused by changes in output frequency and load. Consequently, load testing of a single inverter under different operating conditions is poorly adaptable, reducing the efficiency and reliability of inverter load testing. Summary of the Invention

[0004] In a first aspect, an embodiment of the present application provides a load testing method for a large-scale inverter system, the method comprising the following steps: Obtain the total harmonic distortion coefficient of the load test area and the sub-load test process corresponding to the current working point within the load test area; The total harmonic frequencies of the operating points under all sub-load tests before the sub-load test corresponding to the current operating point are used to form a harmonic sequence; based on the change trend of all elements in the harmonic sequence of the current operating point, the harmonic change characteristic value of the current operating point is determined, and the output torque step adjustment coefficient of the current operating point is determined in combination with the difference between the output frequency at the current operating point and the preset output frequency, so as to determine the output torque step of the current operating point; Based on the difference in harmonic sequence and the difference in harmonic sequence length between the previous operating point and the next adjacent operating point in the output frequency of the current operating condition, the output frequency step adjustment coefficient of the current operating point is determined to determine the output frequency step of the current operating point; Based on the output torque, output frequency, output torque step, output frequency step and output frequency of the current operating point, the output torque and output frequency of the next operating point are determined. When the output frequency and output torque of the next operating point exceed the preset output frequency and preset output torque respectively, all operating points traversed in the load test area are counted, and based on the total harmonic distortion coefficient of all operating points, the test inverter is load tested.

[0005] Preferably, the harmonic change characteristic value of the current operating point is a normalized value of a forward fusion result of the slope of a fitting straight line obtained by fitting all elements in the harmonic sequence of the current operating point and the total harmonic distortion coefficient of the current operating point.

[0006] Preferably, the expression of the output torque step adjustment coefficient of the current operating point is: Where, Indicates the output torque step adjustment coefficient of the current operating point; Indicates the output frequency of the current operating point; Indicates the preset output frequency; Indicates the harmonic change characteristic value of the current operating point; exp[ ] represents an exponential function with a natural constant as the base.

[0007] Preferably, the output torque step of the current operating point is the result of multiplying the output torque step of the operating point in the previous load test process corresponding to the current operating point by the output torque step adjustment coefficient of the current operating point, wherein the initial value of the output torque step is a preset value.

[0008] Preferably, the output frequency step adjustment coefficient of the current operating point is determined as follows: the difference in harmonic sequence between the previous operating point and the next adjacent operating point in the output frequency of the current operating condition and the deviation in the length of the harmonic sequence between the previous operating point and the next adjacent operating point in the output frequency of the current operating condition are both negatively correlated with the output frequency adjustment step coefficient of the current operating point; The length of the harmonic frequency of the previous operating point adjacent to the current operating point on the output frequency is positively correlated with the output frequency step adjustment coefficient of the current operating point. Preferably, the output frequency step of the current operating point is the product of the output frequency step of the operating point in the previous load test process corresponding to the current operating point and the output frequency step adjustment coefficient of the current operating point, wherein the initial value of the output frequency step is a preset value.

[0009] Preferably, the output torque and output frequency of the next operating point are respectively the sum of the output torque and the output torque step length at the current operating point, and the sum of the output frequency and the output frequency step length.

[0010] Preferably, the load test on the test inverter includes: If the total harmonic distortion coefficient of any operating point among all operating points in the load test area is greater than the preset threshold, the tested inverter does not meet the factory standards; otherwise, the tested inverter meets the factory standards.

[0011] In the second aspect, an embodiment of the present application provides a load testing system for a large-scale inverter system, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein when the processor executes the computer program, it implements any one of the above-mentioned load testing methods for a large-scale inverter system.

[0012] In a third aspect, an embodiment of the present application further provides a load testing medium for a large inverter system, wherein the medium stores a computer program, and when the computer program is executed by a processor, the load testing method for a large inverter system described in any one of the above items is implemented.

[0013] As can be seen from the above embodiments, the load testing method for a large-scale inverter system provided by the embodiments of the present application has at least the following beneficial effects: The present application dynamically adjusts the output torque step size by analyzing the changing trend of the total harmonic distortion coefficient and the difference between the current frequency and the minimum output frequency. When the changing trend of the total harmonic distortion coefficient is detected to be increasing or the output frequency is high, the step size is automatically reduced to increase the test density, thereby more reliably discovering potential problems and improving the efficiency and reliability of load testing. Furthermore, the present application dynamically calculates the output frequency step size adjustment coefficient by analyzing the differences and length deviations of the harmonic sequences of adjacent operating points. This adaptive adjustment can intelligently optimize the test density, ensuring in-depth detection of problem areas and improving the efficiency and reliability of inverter load testing. The present application dynamically adjusts the test step size by analyzing the changing trend of the total harmonic distortion coefficient of the inverter under different frequency and torque conditions and the sequence differences of adjacent operating points. When the total harmonic distortion coefficient is detected to be increasing or the performance fluctuates greatly, the step size is automatically reduced to increase the test density to further detect potential problems. Otherwise, the step size is increased to improve efficiency, comprehensively covering the inverter operating conditions, helping to discover potential faults and improving the efficiency and reliability of inverter load testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present application or the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0015] Figure 1 A flowchart of a load testing method for a large-scale inverter system provided in one embodiment of the present application; Figure 2 A schematic diagram of the inverter load test process provided for one embodiment of the present application. DETAILED DESCRIPTION

[0016] To further illustrate the technical means and effectiveness of this application to achieve the intended purpose of the invention, the following, in conjunction with the accompanying drawings and preferred embodiments, describes in detail the load testing method, system, and medium for large-scale inverter systems proposed in this application, including their specific implementation methods, structures, features, and effectiveness. In the following description, different references to "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0017] 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.

[0018] The following describes in detail the specific solutions of the load testing method, system and medium for large-scale inverter systems provided by the present application with reference to the accompanying drawings.

[0019] See also Figure 1 , which shows a flowchart of a load testing method for a large-scale inverter system provided by an embodiment of the present application, the method comprising the following steps: S1: The binary group consisting of the output frequency of the test inverter and the output torque of the load simulation mechanism at the end of each load test is recorded as the working point, and a coordinate system is constructed with the output frequency as the horizontal coordinate and the output torque as the vertical coordinate to obtain the load test area in the coordinate system, and obtain the total harmonic distortion coefficient of the load test process corresponding to the current working point in the load test area.

[0020] The load testing system proposed in this embodiment includes a test inverter, an asynchronous motor, a load simulation mechanism, a voltage sensor, and a host computer. The test inverter is connected to the asynchronous motor to form a large-scale inverter system. The input shaft of the asynchronous motor is connected to the load simulation mechanism. The load simulation mechanism in this embodiment is an electromagnetic load simulator. The electromagnetic load simulator outputs different torque values ​​by adjusting the excitation voltage of the controller, which serves as the simulated torque load for the large-scale inverter system. The voltage sensor is used to detect the output voltage of the test inverter and evaluate its operating performance under different operating conditions. The host computer is used to analyze the collected data and further control the output frequency of the test inverter and the output torque of the load simulation mechanism, thereby achieving load and frequency adjustment for testing the large-scale inverter system.

[0021] The inverter's output frequency determines the motor's speed, while the load simulation structure's output torque determines the load size. Together, these two factors determine the inverter's operating conditions. By adjusting frequency and torque, the load test system can simulate different actual operating environments, thereby comprehensively evaluating the inverter's performance.

[0022] In this embodiment, a binary group consisting of the output frequency of the test inverter and the output torque of the load simulation mechanism during each load test process is recorded as an operating point; further, an fOM coordinate system is constructed with the output frequency as the horizontal coordinate and the output torque as the vertical coordinate, wherein f represents the output frequency and M represents the output torque; further, a load test area in the coordinate system is constructed to obtain the total harmonic distortion coefficient of the load test process corresponding to the current operating point in the load test area.

[0023] It should be noted that the specific process of obtaining the load test area in the coordinate system is as follows: setting the maximum value fmax and minimum value fmin of the test inverter output frequency to represent the output frequency range of the large inverter system; setting the maximum value Mmax and minimum value Mmin of the load simulation mechanism output torque to represent the load variation range of the large inverter system. In this embodiment, the maximum value fmax and minimum value fmin of the output frequency are set to 5Hz and 120Hz respectively, and the maximum value Mmax and minimum value Mmin of the load simulation mechanism output torque are set to 5Hz and 120Hz respectively. and 100 ; Further, the rectangular area enclosed by the straight lines f=fmax, f=fmin and the straight lines M=Mmax, M=Mmin in the fOM coordinate system is recorded as the load test area of ​​the large inverter system.

[0024] In addition, it is supplemented that the total harmonic distortion coefficient is a well-known technology. In this embodiment, the specific process of obtaining the total harmonic distortion coefficient of the sub-load test process corresponding to the current operating point in the load test area is: real-time acquisition of the output voltage of the test inverter during the sub-load test process corresponding to the current operating point, setting the output voltage acquisition frequency to k, and using the voltage data at all times during the sub-load test process corresponding to the current operating point as the input of the fast Fourier transform algorithm, outputting the frequency domain signal, counting all harmonic amplitudes and fundamental amplitudes in the frequency domain signal, calculating the ratio of the root mean square of all harmonic amplitudes to the fundamental amplitude, and multiplying the ratio by 100% as the total harmonic distortion coefficient at each operating point, specifically for each operating condition within the preset time length.

[0025] The value of the output voltage acquisition frequency k is manually set. In this embodiment, the value of the output voltage acquisition frequency k is 20 MHz. The implementer can also set it by himself according to the specific situation. This embodiment does not impose any special restrictions.

[0026] It should be understood that the fast Fourier transform algorithm and the root mean square calculation method are well-known technologies, and the specific process of converting the output voltage into a frequency domain signal using the fast Fourier transform algorithm and the specific process of calculating the root mean square will not be repeated here.

[0027] S2: Determine the output torque step and output frequency step of the current operating point respectively; determine the output torque and output frequency of the next operating point based on the output torque, output frequency, output torque step, output frequency step and output frequency of the current operating point; when the output frequency and output torque of the next operating point exceed the preset output frequency and preset output torque respectively, count all the operating points traversed in the load test area, and perform load test on the test inverter based on the total harmonic distortion coefficient of all the operating points.

[0028] In the load test area, that is, the rectangular area enclosed by the straight lines f=fmax, f=fmin and the straight lines M=Mmax, M=Mmin in the coordinate system, all possible operating points are obtained by gradually adjusting the frequency and torque to comprehensively evaluate the performance of the frequency converter. Specifically: this embodiment adjusts the operating conditions of the large frequency converter system starting from the minimum value fmin of the output frequency of the test frequency converter and the minimum value Mmin of the output torque of the load simulation mechanism. First, the output frequency of the test frequency converter is fixed, and the output torque of the load simulation mechanism is adjusted to obtain different operating points until the output torque reaches the maximum value Mmax from the minimum value Mmin at the output frequency; secondly, the output torque of the load simulation mechanism is fixed, and the output frequency of the test frequency converter is adjusted to obtain different operating points until the output frequency reaches the maximum value fmax from the minimum value fmin at the output torque. Based on the above process, all operating points in the load test area are obtained. The specific process is as follows: S201: The total harmonic frequencies of the operating points under all sub-load tests before the sub-load test corresponding to the current operating point are combined to form a harmonic sequence; based on the change trend of all elements in the harmonic sequence of the current operating point, the harmonic change characteristic value of the current operating point is determined, and the output torque step adjustment coefficient of the current operating point is determined in combination with the difference between the output frequency at the current operating point and the preset output frequency to determine the output torque step of the current operating point, specifically: As a real-time method, in this embodiment, the total harmonic frequencies of the operating points under all the sub-load tests before the sub-load test corresponding to the current operating point are combined into a harmonic sequence.

[0029] Furthermore, this embodiment determines the harmonic change characteristic value of the current operating point based on the change trend of all elements in the harmonic sequence of the current operating point, specifically: In this embodiment, the normalized value of the forward fusion result of the slope of the fitting straight line obtained by fitting all elements in the harmonic sequence of the current operating point and multiplying the total harmonic distortion coefficient of the current operating point is used as the harmonic change characteristic value of the current operating point.

[0030] It should be understood that forward fusion refers to combining two or more indicators through addition or multiplication to obtain a comprehensive indicator, thereby more comprehensively and accurately evaluating a phenomenon or problem. This fusion method is not limited to simple arithmetic operations and can also include more complex statistical models and analysis methods. Implementers can choose according to their specific circumstances and this embodiment does not impose any special restrictions.

[0031] Preferably, as a specific implementation method, in this embodiment, the normalized value of the slope of the fitting straight line obtained by fitting all elements in the harmonic sequence of the current operating point and the multiplication result of the total harmonic distortion coefficient of the current operating point is used as the harmonic change characteristic value of the current operating point. In particular, if there is only one load test before the corresponding load test of the current operating point, the harmonic change characteristic value of the current operating point is 0; in actual application, as other implementation methods, the implementer may also choose other forward fusion methods based on specific circumstances, and this embodiment does not impose any special restrictions.

[0032] It should be noted that the specific process of the above fitting is: all elements in the harmonic sequence are used as inputs of the least squares method, wherein the output frequency in each element in the harmonic sequence is used as the independent variable in the least squares fitting method, and the output torque is used as the dependent variable in the least squares fitting method, and the output is a fitting straight line of output frequency-output torque. In actual application, as other implementation methods, the implementer may also adopt other linear fitting methods such as linear regression in combination with specific circumstances. Regarding the selection of the fitting method, this embodiment does not impose any special restrictions.

[0033] Among them, the least square method is a well-known technology, and its specific fitting process is not described in detail.

[0034] According to the harmonic change characteristic value of the current operating point, it can be understood that if the harmonic change characteristic value of the current operating point is larger, the total harmonic distortion coefficient of the test inverter is larger, and the probability that the total harmonic distortion coefficient is on an upward trend is greater, it indicates that the test inverter is more likely to have performance problems near the current operating point, and more intensive operating point tests are required in the future.

[0035] Furthermore, this embodiment determines the output torque step adjustment coefficient of the current operating point based on the harmonic change characteristic value of the current operating point and the difference between the output frequency at the current operating point and the preset output frequency, so as to determine the output torque step of the current operating point, specifically: As an implementation method, in this embodiment, the output torque step adjustment coefficient of the current operating point is The expression is: Where, Indicates the output frequency of the current operating point; Indicates the preset output frequency; Indicates the harmonic change characteristic value of the current operating point; exp[ ] represents an exponential function with a natural constant as the base.

[0036] It should be noted that, in this embodiment, the value of the preset output frequency is the same as the value of the minimum output frequency fmin, that is, 5 Hz.

[0037] According to the output torque step adjustment coefficient of the current operating point, it can be understood that if the output torque step adjustment coefficient of the current operating point is smaller, it reflects that the output frequency of the test inverter under the current operating point test is larger, indicating that the output power under the same torque load is larger, and there is a possibility of excessive harmonic interference. Therefore, the torque step size needs to decrease with the output frequency of the test inverter to increase its test density in working conditions prone to performance failures and improve the reliability of load testing.

[0038] Furthermore, in this embodiment, the output torque step of the working condition point in the previous load test process corresponding to the current working condition point is multiplied by the output torque step adjustment coefficient of the current working condition point as the output torque step of the current working condition point, wherein the initial value of the output torque step is a preset value, and the preset value in this embodiment is In actual application, as other implementation methods, the implementer can also set them according to the specific situation, and this embodiment does not impose any special restrictions.

[0039] At this point, this embodiment dynamically adjusts the output torque step size by analyzing the changing trend of the total harmonic distortion coefficient and the difference between the current frequency and the minimum output frequency. When it is detected that the changing trend of the total harmonic distortion coefficient is an upward trend or the output frequency is high, the step size is automatically reduced to increase the test density, thereby more reliably discovering potential problems and improving the efficiency and reliability of load testing.

[0040] S202: Based on the difference in harmonic sequence and the difference in harmonic sequence length between the previous operating point and the next adjacent operating point in output frequency at the current operating point, determine the output frequency step adjustment coefficient of the current operating point to determine the output frequency step of the current operating point, specifically: The difference in harmonic sequence between the previous operating point and the next adjacent operating point on the output frequency of the current operating condition and the deviation in the length of the harmonic sequence between the previous operating point and the next adjacent operating point on the output frequency of the current operating condition are both negatively correlated with the output frequency adjustment step coefficient of the current operating point; The length of the harmonic frequency of the current operating condition at the adjacent previous operating condition point on the output frequency is positively correlated with the output frequency step adjustment coefficient of the current operating condition point.

[0041] It should be understood that a positive correlation means that the dependent variable will increase as the independent variable increases, and the dependent variable will decrease as the independent variable decreases. The specific relationship can be an additive relationship or a multiplicative relationship, etc., which is determined by actual application and this application does not impose any special restrictions; a negative correlation means that the dependent variable will decrease as the independent variable increases, and the dependent variable will increase as the independent variable decreases. It can be a subtractive relationship or a division relationship, etc., which is determined by actual application.

[0042] Preferably, as a specific implementation method, in this embodiment, the output frequency step adjustment coefficient of the current operating point is The expression is: Where, Indicates the difference in harmonic sequence between the previous operating point and the next adjacent operating point in output frequency under the current operating condition; Indicates the deviation in the length of the harmonic sequence between the previous operating point and the next adjacent operating point on the output frequency of the current operating condition; represents the length of the harmonic frequency of the current operating condition at the adjacent previous operating condition point on the output frequency; norm( ) and norm{} both represent normalization functions; ln[ ] represents a logarithmic function with a natural constant as the base; in actual application, the implementer may also choose a method to represent the positive and negative correlation relationship based on the specific situation, and this embodiment does not impose any special restrictions.

[0043] It should be noted that there are many methods for measuring the difference between sequences. In this embodiment, the DTW distance of the harmonic sequence between the previous operating point and the next adjacent operating point in the output frequency of the current operating condition is used as the difference in the harmonic sequence between the previous operating point and the next adjacent operating point in the output frequency of the current operating condition. In actual application, as other implementation methods, implementers may also select other methods for measuring sequence differences such as Euclidean distance or Manhattan distance based on specific circumstances. This embodiment does not impose any special restrictions on the selection of methods for measuring differences between sequences.

[0044] The calculation method of the DTW distance is a well-known technology, and its specific calculation process is not repeated here.

[0045] It should be noted that, in this embodiment, the absolute value of the difference in the length of the harmonic sequence between the previous operating point and the next adjacent operating point in the output frequency of the current operating condition is used as the deviation in the length of the harmonic sequence between the previous operating point and the next adjacent operating point in the output frequency of the current operating condition.

[0046] According to the output frequency step adjustment coefficient of the current operating point, it can be understood that if the difference in the harmonic sequence between the adjacent previous operating point and the next adjacent operating point is greater, it means that the working performance of the test inverter at the output frequency corresponding to the current operating point has changed significantly, and the load test density near the operating point needs to be increased, and the corresponding output frequency step adjustment coefficient is smaller; at the same time, if the length deviation of the harmonic sequence between the adjacent previous operating point and the next adjacent operating point is greater, it means that the working performance of the test inverter fluctuates more strongly with the load torque, and the probability of performance failure is greater. Therefore, it is necessary to increase the subsequent load test density, and the corresponding output frequency step adjustment coefficient is smaller; On the contrary, if the difference in the harmonic sequence between the adjacent previous operating point and the next adjacent operating point is smaller, it means that the working performance of the test inverter at the output frequency corresponding to the current operating point changes less, indicating that the performance in this area is relatively stable, and the load test density near the operating point can be appropriately reduced to improve the test efficiency, and the corresponding output frequency step adjustment coefficient is larger; at the same time, if the length deviation of the harmonic sequence between the adjacent previous operating point and the next adjacent operating point is smaller, it means that the working performance of the test inverter fluctuates weaker with the load torque, the performance is more stable, and the probability of performance failure is smaller, so the subsequent load test density can be appropriately reduced, and the corresponding output frequency step adjustment coefficient is larger.

[0047] Furthermore, in this embodiment, the output frequency step of the working condition point in the previous load test process corresponding to the current working condition point is multiplied by the output frequency step adjustment coefficient of the current working condition point as the output frequency step of the current working condition point, wherein the initial value of the output frequency step is a preset value, wherein the initial value of the output torque step is a preset value, and the preset value in this embodiment is In actual application, as other implementation methods, the implementer can also set them according to the specific situation, and this embodiment does not impose any special restrictions.

[0048] At this point, this embodiment dynamically calculates the output frequency step adjustment coefficient by analyzing the differences and length deviations of the harmonic sequences at adjacent operating points. This adaptive adjustment can intelligently optimize the test density, ensuring in-depth detection of problem areas and improving the efficiency and reliability of the inverter load test.

[0049] S203: Based on the output torque, output frequency, output torque step, output frequency step, and output frequency at the current operating point, determine the output torque and output frequency at the next operating point. When the output frequency and output torque at the next operating point exceed the preset output frequency and preset output torque, respectively, count all operating points traversed within the load test area and perform a load test on the test inverter based on the total harmonic distortion coefficient of all operating points. Specifically, Based on S201 and S202, the output torque step and the output frequency step are obtained. Further, based on the output torque, output frequency, output torque step, output frequency step, and output frequency of the current operating point, the output torque and output frequency of the next operating point are determined. Specifically: In this embodiment, the result of adding the output torque of the current operating point to the output torque step is used as the output torque of the next operating point, and the result of adding the output frequency of the current operating point to the output frequency step is used as the output frequency of the next operating point.

[0050] Furthermore, if the output frequency of the next operating point is greater than the preset output frequency or the output torque is greater than the preset output torque, the search for subsequent operating points is stopped, and all operating points traversed in the load test area are counted. If the total harmonic distortion coefficient of any operating point among all the operating points in the load test area is greater than the preset threshold, the test inverter does not meet the factory standards. Otherwise, the test inverter meets the factory standards.

[0051] It should be noted that the preset threshold, i.e., the total harmonic distortion (THD) limit, can be obtained by the total harmonic distortion (THD) limit calculation formula in the national standard GB / T 12668.2-2002. In this embodiment, as an implementation method, the preset threshold value is 5%. In actual application, the implementer needs to adopt the national standard GB / T 12668.2-2002 according to the inverter specifications to obtain the total harmonic distortion (THD) limit under the relevant inverter specifications.

[0052] Preferably, the inverter load test process diagram provided in this embodiment is as follows Figure 2 shown.

[0053] Thus, this embodiment dynamically adjusts the test step size by analyzing the changing trend of the total harmonic distortion coefficient of the inverter under different frequency and torque conditions and the sequence differences between adjacent operating points. When an increase in THD or large performance fluctuations are detected, the step size is automatically reduced to increase the test density to further detect potential problems; otherwise, the step size is increased to improve efficiency. This method can comprehensively cover the inverter operating conditions, effectively discover potential faults, significantly improve the targetedness and reliability of load testing, and ensure that the inverter's factory performance meets the standards.

[0054] Based on the same inventive concept as the above method, an embodiment of the present application also provides a load testing system for a large-scale inverter system, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements any one of the above-mentioned load testing methods for large-scale inverter systems.

[0055] Based on the same inventive concept as the above-mentioned method, an embodiment of the present application also provides a load testing medium for a large-scale inverter system, wherein a computer program is stored in the medium, and when the computer program is executed by the processor, the load testing method for a large-scale inverter system described in any one of the above-mentioned items is implemented. It should be noted that the above-mentioned sequence of the embodiments of the present application is only for description and does not represent the advantages and disadvantages of the embodiments. And the above-mentioned specific embodiments of this specification are described. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0056] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0057] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A load testing method for a large-scale inverter system, characterized in that: The method comprises the following steps: Obtain the total harmonic distortion coefficient of the load test area and the sub-load test process corresponding to the current working point within the load test area; The total harmonic frequencies of the operating points under all sub-load tests before the sub-load test corresponding to the current operating point are used to form a harmonic sequence; based on the change trend of all elements in the harmonic sequence of the current operating point, the harmonic change characteristic value of the current operating point is determined, and the output torque step adjustment coefficient of the current operating point is determined in combination with the difference between the output frequency at the current operating point and the preset output frequency, so as to determine the output torque step of the current operating point; Based on the difference in harmonic sequence and the difference in harmonic sequence length between the previous operating point and the next adjacent operating point in the output frequency of the current operating point, the output frequency step adjustment coefficient of the current operating point is determined to determine the output frequency step of the current operating point; Based on the output torque, output frequency, output torque step, output frequency step and output frequency of the current operating point, the output torque and output frequency of the next operating point are determined. When the output frequency and output torque of the next operating point exceed the preset output frequency and preset output torque respectively, all operating points traversed in the load test area are counted, and based on the total harmonic distortion coefficient of all operating points, the test inverter is load tested.

2. The load testing method for a large-scale inverter system according to claim 1, characterized in that: The harmonic change characteristic value of the current operating point is a normalized value of a forward fusion result of the slope of a fitting straight line obtained by fitting all elements in the harmonic sequence of the current operating point and the total harmonic distortion coefficient of the current operating point.

3. The load testing method for a large-scale inverter system according to claim 1, characterized in that: The expression of the output torque step adjustment coefficient of the current operating point is: Where, Indicates the output torque step adjustment coefficient of the current operating point; Indicates the output frequency of the current operating point; Indicates the preset output frequency; Indicates the harmonic change characteristic value of the current operating point; exp[ ] represents an exponential function with a natural constant as the base.

4. The load testing method for a large-scale inverter system according to claim 1, wherein: The output torque step of the current operating point is the result of multiplying the output torque step of the operating point in the previous load test process corresponding to the current operating point by the output torque step adjustment coefficient of the current operating point, wherein the initial value of the output torque step is a preset value.

5. The load testing method for a large-scale inverter system according to claim 1, characterized in that: The method for determining the output frequency step adjustment coefficient of the current operating point is: The difference in harmonic sequence between the previous operating point and the next adjacent operating point on the output frequency of the current operating condition and the deviation in the length of the harmonic sequence between the previous operating point and the next adjacent operating point on the output frequency of the current operating condition are both negatively correlated with the output frequency adjustment step coefficient of the current operating point; The length of the harmonic frequency of the current operating condition at the adjacent previous operating condition point on the output frequency is positively correlated with the output frequency step adjustment coefficient of the current operating condition point.

6. The load testing method for a large-scale inverter system according to claim 1, wherein: The output frequency step of the current operating point is the result of multiplying the output frequency step of the operating point in the previous load test process corresponding to the current operating point by the output frequency step adjustment coefficient of the current operating point, wherein the initial value of the output frequency step is a preset value.

7. The load testing method for a large-scale inverter system according to claim 1, wherein: The output torque and output frequency of the next operating point are respectively the sum of the output torque and the output torque step length at the current operating point, and the sum of the output frequency and the output frequency step length.

8. The load testing method for a large-scale inverter system according to claim 1, wherein: The load test on the test inverter includes: If the total harmonic distortion coefficient of any operating point among all operating points in the load test area is greater than the preset threshold, the tested inverter does not meet the factory standards; otherwise, the tested inverter meets the factory standards.

9. A load testing system for a large-scale inverter 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 load testing method for a large-scale inverter system as described in any one of claims 1 to 8 is implemented.

10. A load test medium for a large-scale inverter system, wherein a computer program is stored in the medium, characterized in that: When the computer program is executed by a processor, the load testing method for a large-scale inverter system according to any one of claims 1 to 8 is implemented.

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