Inverter current normalization method based on balanced distortion

Abstract

The present application relates to the technical field of inverter output current normalization processing, and provides an inverter current normalization method based on balanced distortion, which comprises the following steps: sequentially performing filtering processing and compression processing on inverter output current to obtain current amplitude I ; determining the positive and negative directions of original phase current and generating a sign factor S ; performing weighting processing on the current amplitude I by using a preset sensitivity coefficient factor p ; and performing normalization processing on the inverter output current amplitude after weighting processing by using a nonlinear normalization function. The present application can better balance the distortion degree of different amplitude currents, and can effectively improve the sensitivity of fault characteristics, especially under light load conditions. By uniformly mapping the current value with amplitude variation to a specified interval, reliable diagnosis of inverter single tube open circuit fault under variable load conditions is realized, and misjudgment caused by load variation is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inverter output current normalization processing, and in particular, relates to an inverter current normalization method based on balanced distortion. BACKGROUND

[0002] In an inverter system, the amplitude of the output current will fluctuate with changes in the output frequency and load conditions. When the frequency changes, the current amplitude will change due to the influence of inductive or capacitive loads on impedance; and different load types and load size changes also directly affect the dynamic characteristics and stability of the inverter output current. Therefore, when studying the performance of the inverter or designing algorithms, it is difficult to accurately evaluate the control effect or system characteristics by relying solely on the original current amplitude.

[0003] In order to eliminate the influence of frequency changes and load changes on the current amplitude, normalizing the output current amplitude becomes an effective method. Through normalization, the current amplitude can be unified within a standard range, thereby focusing more on analyzing the performance of the inverter control system itself rather than the current changes disturbed by external factors. This method is of great significance in controller design, characteristic analysis, model verification, and system comparison. SUMMARY

[0004] The present application aims to at least solve one of the problems in the prior art or related art.

[0005] To this end, the present application aims to provide an inverter current normalization method based on balanced distortion.

[0006] In order to achieve the above-mentioned purpose, the technical solution of the present application provides an inverter current normalization method based on balanced distortion. The inverter is a two-level voltage source inverter; the two-level voltage source inverter is a three-phase bridge inverter circuit, and the power supply of the three-phase bridge inverter circuit is a direct current power supply V dc , the output end of the three-phase bridge inverter circuit is connected to a three-phase motor; the three-phase bridge inverter circuit is composed of three independent A-phase, B-phase and C-phase bridge arms, the A-phase bridge arm includes upper switch tube S 1 and anti-parallel diode Z 1, lower switch tube S 4 and anti-parallel diode Z 4; the B-phase bridge arm includes upper switch tube S 3 and anti-parallel diode Z 3, lower switch tube S 6 and anti-parallel diode Z 6; the C-phase bridge arm includes upper switch tube S 5 and anti-parallel diode Z 5, lower switch tubeS 2 and anti-parallel diode Z 2; midpoint of each bridge leg a , b , c as an AC output terminal, connected to a corresponding phase of the three-phase motor respectively; the midpoint a , b , c the output current is i a , i b , and i c ; the normalization method comprises: step S1: sequentially performing filtering processing and compression processing on the inverter output current to obtain a current amplitude I ; step S2: determining the positive and negative directions of the original phase current, and generating a sign factor S ; wherein the original phase current is the inverter output current after filtering processing; step S3: performing weighting processing on the current amplitude I using a preset sensitivity coefficient factor p ; wherein the preset sensitivity coefficient factor p is a variable parameter greater than 0; step S4: performing normalization processing on the inverter output current amplitude after weighting processing using a nonlinear normalization function.

[0007] Preferably, the step S1 specifically comprises: step S1.1: performing filtering operation on the inverter output current according to the mean filtering principle to reduce noise interference, so as to obtain the filtered current ; step S1.2: obtaining the inverter output current amplitude when the three-phase motor is in no-load operation as ; step S1.3: performing absolute value operation on to eliminate the influence of directionality on the calculation of the inverter output current amplitude; step S1.4: performing mean value processing on the inverter output current after absolute value operation to realize the mapping of the current value after mean value processing to a corresponding interval, and then performing compression processing on the current amplitude after mean value processing using root operation; the corresponding mathematical expression of the step S1.4 is:

[0008] (1)

[0009] wherein k is a positive integer constant. n

[0010] Preferably, the step S2 specifically comprises: step S2.1: determining the positive and negative directions of the filtered inverter output current using a sign function sgn, and generating a sign factor​S ; the mathematical expression corresponding to the step S2.1 is:

[0011] (2)

[0012] wherein the symbol factor S is combined with the inverter output current amplitude information in subsequent calculations, so as to realize the normalization of the inverter output current amplitude while completely retaining the directionality information of the input signal , so as to ensure that the processed inverter output current can correctly reflect the flow direction of the original phase current, so as to meet the control requirements of the inverter output waveform.

[0013] Preferably, the step S3 specifically comprises: a step S3.1 of performing weighting processing on the inverter output current amplitude result processed through the above steps S1 and S2 by using a preset sensitivity coefficient factor p to construct a dimensionless input variable X ; the mathematical expression corresponding to the step S3.1 is:

[0014] (3)

[0015] wherein the preset sensitivity adjustment coefficient p is used to set the slope characteristics of the nonlinear function in different input ranges, so as to realize flexible adjustment of the response speed and sensitivity degree of the normalization process according to different motor models, load working conditions, or control requirements of the inverter output waveform.

[0016] Preferably, the step S4 specifically comprises:

[0017] a step S4.1 of bringing the signal X processed through weighting into of a nonlinear normalization function x , so as to realize amplitude compression and normalization mapping of the signal X ; wherein the nonlinear normalization function stably maps the input value X to the interval [−1, 1], so as to avoid saturation overrun of the inverter output, while making the inverter output maintain high resolution in the low amplitude interval, so as to realize gradual saturation of the inverter output in the high amplitude interval, so as to effectively improve the stability and anti-interference ability of the inverter output sinusoidal signal.

[0018] Advantages of the present application:

[0019] In order to solve the problem that the current amplitude changes significantly when the inverter is running under different load conditions, and the fault diagnosis method based on fixed threshold is difficult to effectively distinguish the fault state and the normal state, the application proposes a method of normalizing the output current of the inverter based on balanced distortion. The inverter current normalization method based on balanced distortion adopts a specific S-shaped curve mapping relationship, which can dynamically map the current amplitude under different loads to a preset standardized interval. The selection of the interval is determined through experiments and theoretical analysis to ensure that the current characteristic change when the fault occurs can be effectively amplified and distinguished under various load conditions. Compared with the traditional linear normalization method, the normalization function proposed in the application can better balance the distortion degree of different amplitude currents, especially under light load conditions, which can effectively improve the sensitivity of fault characteristics. By uniformly mapping the amplitude-changing current value to the specified interval, reliable diagnosis of the inverter single tube open circuit fault under variable load conditions is realized, and misjudgment caused by load changes is avoided.

[0020] Additional aspects and advantages of the application will become apparent from the following description, or will be learned by practice of the application. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A schematic flow chart of the inverter current normalization method based on balanced distortion of one embodiment of the application is shown.

[0022] Figure 2 A topological schematic diagram of a two-level voltage source type inverter of one embodiment of the application is shown.

[0023] Figure 3 A principle schematic diagram of the balanced distortion normalization function of one embodiment of the application is shown. DETAILED DESCRIPTION

[0024] In order to more clearly understand the above-mentioned purposes, features and advantages of the application, the application will be further described in detail below in combination with the drawings and specific embodiments. It should be noted that the embodiments of the application and the features in the embodiments can be combined with each other without conflict.

[0025] In the following description, many specific details are set forth in order to provide a thorough understanding of the application, but the application can also be implemented in other ways different from those described herein, therefore, the scope of protection of the application is not limited to the specific embodiments disclosed below.

[0026] Figure 1 A schematic flow chart of the inverter current normalization method based on balanced distortion of one embodiment of the application is shown. The inverter is a two-level voltage source type inverter; as Figure 2As shown, the two-level voltage source inverter is a three-phase bridge inverter circuit, and the power supply of the three-phase bridge inverter circuit is a direct current power supply V dc , and the output end of the three-phase bridge inverter circuit is connected to a three-phase motor; the three-phase bridge inverter circuit is composed of three independent A-phase, B-phase and C-phase bridge arms, the A-phase bridge arm includes upper switch tube S 1 and anti-parallel diode Z 1, lower switch tube S 4 and anti-parallel diode Z 4; the B-phase bridge arm includes upper switch tube S 3 and anti-parallel diode Z 3, lower switch tube S 6 and anti-parallel diode Z 6; the C-phase bridge arm includes upper switch tube S 5 and anti-parallel diode Z 5, lower switch tube S 2 and anti-parallel diode Z 2; the midpoint a , b , c of each bridge arm is connected to the corresponding phase of the three-phase motor as an alternating current output end; the current output by the midpoint a , b , c is i a , i b , and i c ;

[0027] As Figure 1 shown, the inverter current normalization method based on balanced distortion includes:

[0028] Step S1: sequentially performing filtering processing and compression processing on the inverter output current to obtain current amplitude I ;

[0029] Step S2: determining the positive and negative directions of the original phase current, and generating a sign factor S ; wherein the original phase current is the inverter output current after filtering processing;

[0030] Step S3: performing weighting processing on the current amplitude I using a preset sensitivity coefficient factor p ; wherein the preset sensitivity coefficient factor p is a variable parameter greater than 0;

[0031] Step S4: normalizing the weighted inverter output current amplitude by using a nonlinear normalization function.

[0032] In an embodiment of the present application, the step S1 specifically comprises: step S1.1: filtering the inverter output current according to the mean filtering principle to reduce noise interference, so as to obtain the filtered current ; step S1.2: obtaining the inverter output current amplitude when the three-phase motor is in no-load operation as ; step S1.3: performing absolute value operation on to eliminate the influence of directionality on the calculation of the inverter output current amplitude; and step S1.4: performing mean value processing on the inverter output current after the absolute value operation, so as to map the current value after the mean value processing to a corresponding interval, and then performing compression processing on the current amplitude after the mean value processing by using the root operation; the mathematical expression corresponding to the step S1.4 is:

[0033] (1)

[0034] wherein, k is a positive integer constant. n

[0035] In an embodiment of the present application, the step S2 specifically comprises: step S2.1: determining the positive and negative directions of the filtered inverter output current by using the sign function sgn, and generating a sign factor S ; the mathematical expression corresponding to the step S2.1 is:

[0036] (2)

[0037] wherein, the sign factor S is combined with the inverter output current amplitude information in subsequent calculation, so as to realize the normalization of the inverter output current amplitude while completely retaining the directionality information of the input signal , so as to ensure that the processed inverter output current can correctly reflect the flow direction of the original phase current, so as to meet the control requirements of the inverter output waveform.

[0038] In an embodiment of the present application, the step S3 specifically comprises: step S3.1: performing weighting processing on the inverter output current amplitude result processed by the above steps S1 and S2 by using a preset sensitivity coefficient factor p , so as to construct a dimensionless input variable X ; the mathematical expression corresponding to the step S3.1 is:

[0039] (3) ​

[0040] Among them, the preset sensitivity adjustment coefficient p It is used to set the slope characteristics of the nonlinear function in different input ranges, so as to flexibly adjust the response speed and sensitivity of the normalization process according to the control requirements of different motor models, load conditions or inverter output waveforms.

[0041] In one embodiment of the present invention, step S4 specifically includes:

[0042] Step S4.1: Weight the signal X Substituting the nonlinear normalization function In x In order to achieve signal X The amplitude compression and normalization mapping; whereby the nonlinear normalization function will convert the input value X The inverter output is stably mapped to the [−1,1] interval to avoid output saturation and over-limit, while maintaining high resolution in the low amplitude range. This enables the inverter output to gradually saturate in the high amplitude range, thereby effectively improving the stability and anti-interference capability of the sinusoidal signal output by the inverter.

[0043] The present invention's inverter current normalization method based on balanced distortion will be illustrated below with a specific embodiment. The inverter is a two-level voltage source inverter; the two-level voltage source inverter is a three-phase bridge inverter circuit, and the power supply for the three-phase bridge inverter circuit is a DC power supply. V dc The output of the three-phase bridge inverter circuit is connected to the three-phase motor; the three-phase full-bridge circuit consists of three independent A-phase, B-phase, and C-phase bridge arms, with the A-phase bridge arm including the upper switching transistor. S 1 and anti-parallel diode Z 1. Lower switch transistor S 4 and anti-parallel diodes Z 4; Phase B bridge arm includes the upper switch tube S 3 and anti-parallel diodes Z 3. Lower switch transistor S 6 and anti-parallel diodes Z 6; Phase C bridge arm includes the upper switch tube S 5 and anti-parallel diodes Z 5. Lower switch transistor S 2 and anti-parallel diodes Z 2; Midpoint of each bridge arm a , b , c As AC output terminals, they are respectively connected to the corresponding phases of the three-phase motor; the midpoint a , b , cThe output current is respectively i a , i b , and i c The specific implementation steps of the balanced distortion-based inverter current normalization method of the application are as follows:

[0044] (1) Step S1: sequentially performing filtering processing and compression processing on the inverter output current to obtain the current amplitude I .

[0045] The step S1 specifically comprises:

[0046] Step S1.1: performing filtering operation on the inverter output current according to the mean filtering principle to reduce noise interference, and obtaining the filtered current .

[0047] Step S1.2: obtaining the inverter output current amplitude when the three-phase motor is in no-load operation as .

[0048] Step S1.3: performing absolute value operation on to eliminate the influence of directionality on the calculation of the inverter output current amplitude.

[0049] Step S1.4: performing mean processing on the inverter output current after the absolute value operation to realize the mapping of the current value after the mean processing to the corresponding interval, and then performing compression processing on the current amplitude after the mean processing by using the root operation; the corresponding mathematical expression of the step S1.4 is:

[0050] (1)

[0051] wherein, k is a positive integer constant. n

[0052] (2) Step S2: determining the positive and negative directions of the original phase current and generating a sign factor S ; wherein, the original phase current is the inverter output current after the filtering processing.

[0053] The step S2 specifically comprises:

[0054] Step S2.1: determining the positive and negative directions of the inverter output current after the filtering processing by using the sign function sgn, and generating a sign factor S ; the corresponding mathematical expression of the step S2.1 is:

[0055] (2)​

[0056] Among them, the symbol factor S In subsequent calculations, this information is combined with the inverter output current amplitude to normalize the inverter output current amplitude while fully preserving the input signal. The directional information is used to ensure that the processed inverter output current can correctly reflect the direction of the original phase current, so as to meet the control requirements of the inverter output waveform.

[0057] (3) Step S3: Utilize the preset sensitivity coefficient factor p For current amplitude I Weighting is performed; where the preset sensitivity coefficient factor is... p It is a variable parameter greater than 0;

[0058] Step S3 specifically includes:

[0059] Step S3.1: Utilize the preset sensitivity coefficient factor p The inverter output current amplitude results processed in steps S1 and S2 above are weighted to construct dimensionless input variables. X The mathematical expression corresponding to step S3.1 is:

[0060] (3)

[0061] Among them, the preset sensitivity adjustment coefficient p It is used to set the slope characteristics of the nonlinear function in different input ranges, so as to flexibly adjust the response speed and sensitivity of the normalization process according to the control requirements of different motor models, load conditions or inverter output waveforms.

[0062] (4) Step S4: Normalize the amplitude of the inverter output current after weighting using a nonlinear normalization function.

[0063] Step S4 specifically includes:

[0064] Step S4.1: Weight the signal X Substituting the nonlinear normalization function In x In order to achieve signal X The amplitude compression and normalization mapping; whereby the nonlinear normalization function will convert the input value X The inverter output is stably mapped to the [−1,1] interval to avoid output saturation and over-limit, while maintaining high resolution in the low amplitude range. This enables the inverter output to gradually saturate in the high amplitude range, thereby effectively improving the stability and anti-interference capability of the sinusoidal signal output by the inverter.

[0065] The rationality and feasibility of the inverter current normalization method based on balanced distortion are demonstrated below. Different p , n Normalized current value under parameters like Figure 3 As shown, this inverter current normalization method based on balanced distortion achieves normalization of inverter currents with large amplitude variations. Normalizing to a smaller interval effectively suppressed The impact of changes in amplitude.

[0066] Furthermore, through a nonlinear normalization function Input Mapped to a fixed interval [-1, 1], and using the sign function sgn to maintain consistency between positive and negative directions, a positive integer constant. n Controlling the nonlinear amplitude, preset sensitivity coefficient factor p The steepness of the mapping is determined to achieve smooth, symmetrical normalization.

[0067] like Figure 3 As shown, under no-load conditions The value is 1, under full load conditions. When the value is 4, the normalized current amplitude range is [0.46, 0.96], when the value is 4, the normalized current amplitude range is [0.46, 0.76], and when the value is 4, the normalized current amplitude range is [0.64, 0.99].

[0068] In summary, the inverter current normalization method based on balanced distortion of this invention addresses the problem that the current amplitude of an inverter changes significantly under different load conditions, making it difficult for fixed-threshold-based fault diagnosis methods to effectively distinguish between fault and normal states. This invention proposes a method for normalizing the inverter's output current based on balanced distortion. This method employs a specific S-curve mapping relationship to dynamically map the current amplitude under different loads to a preset standardized range. The selection of this range is determined through experimental and theoretical analysis to ensure that changes in current characteristics during fault occurrence can be effectively amplified and distinguished under various load conditions. Compared to traditional linear normalization methods, the normalization function proposed in this invention can better balance the distortion degree of currents with different amplitudes, especially under light load conditions, effectively improving the sensitivity of fault characteristics. By uniformly mapping the current value with amplitude changes to a specified range, reliable diagnosis of single-tube open-circuit faults in inverters under varying load conditions is achieved, avoiding misjudgments caused by load changes.

[0069] The above merely provides the preferred embodiments of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the principles and technical scope of the present application shall fall into the scope of the present application.

Claims

1. A method for inverter current normalization based on balanced distortion, wherein the inverter is a two-level voltage source inverter; the two-level voltage source inverter is a three-phase bridge inverter circuit, and the power supply of the three-phase bridge inverter circuit is a DC power supply. V dc The output of the three-phase bridge inverter circuit is connected to a three-phase motor; the three-phase bridge inverter circuit consists of three independent A-phase, B-phase, and C-phase bridge arms, with the A-phase bridge arm including an upper switching transistor. S 1 and anti-parallel diode Z 1. Lower switch transistor S 4 and anti-parallel diodes Z 4; Phase B bridge arm includes the upper switch tube S 3 and anti-parallel diodes Z 3. Lower switch transistor S 6 and anti-parallel diodes Z 6; Phase C bridge arm includes the upper switch tube S 5 and anti-parallel diodes Z 5. Lower switch transistor S 2 and anti-parallel diodes Z 2; Midpoint of each bridge arm a , b , c As AC output terminals, they are respectively connected to the corresponding phases of the three-phase motor; the midpoint a , b , c The output currents are respectively i a , i b ,and i c Its characteristics are, The normalization method includes: Step S1: The inverter output current is sequentially filtered and compressed to obtain the current amplitude as... I ; Step S2: Determine the positive and negative directions of the original phase current and generate a sign factor. S Wherein, the original phase current is the inverter output current after filtering; Step S3: Utilize the preset sensitivity coefficient factor p For current amplitude I Weighting is performed; where the preset sensitivity coefficient factor is... p It is a variable parameter greater than 0; Step S4: Normalize the amplitude of the weighted inverter output current using a nonlinear normalization function; Step S2 specifically includes: Step S2.1: Use the sign function sgn to measure the filtered inverter output current. The positive and negative directions are determined, and a sign factor is generated. S The mathematical expression corresponding to step S2.1 is: （2） Among them, the symbol factor S In subsequent calculations, this information is combined with the inverter output current amplitude to normalize the inverter output current amplitude while fully preserving the input signal. The directional information is used to ensure that the processed inverter output current can correctly reflect the direction of the original phase current, so as to meet the control requirements of the inverter output waveform. Step S3 specifically includes: Step S3.1: Utilize the preset sensitivity coefficient factor p The inverter output current amplitude results processed in steps S1 and S2 above are weighted to construct dimensionless input variables. X The mathematical expression corresponding to step S3.1 is: （3） Among them, the preset sensitivity adjustment coefficient p It is used to set the slope characteristics of the nonlinear function in different input ranges, so as to flexibly adjust the response speed and sensitivity of the normalization process according to the control requirements of different motor models, load conditions or inverter output waveforms.

2. The inverter current normalization method based on balanced distortion according to claim 1, characterized in that, Step S1 specifically includes: Step S1.1: The inverter output current is filtered according to the mean filtering principle to reduce noise interference, resulting in the filtered current. ; Step S1.2: When the three-phase motor is running under no-load, obtain the inverter output current amplitude when the three-phase motor is running under no-load. ; Step S1.3: For Perform absolute value calculations to eliminate the influence of directionality on the calculation of inverter output current amplitude; Step S1.4: The inverter output current after absolute value calculation is averaged to map the averaged current value to the corresponding interval, and then the amplitude of the averaged current is compressed using radical calculation; the mathematical expression corresponding to step S1.4 is: （1） in, n It is a positive integer constant.

3. The inverter current normalization method based on balanced distortion according to claim 1, characterized in that, Step S4 specifically includes: Step S4.1: Weight the signal X Substituting the nonlinear normalization function In x In order to achieve signal X The amplitude compression and normalization mapping; whereby the nonlinear normalization function will convert the input value X The inverter output is stably mapped to the [−1,1] interval to avoid output saturation and over-limit, while maintaining high resolution in the low amplitude range. This enables the inverter output to gradually saturate in the high amplitude range, thereby effectively improving the stability and anti-interference capability of the sinusoidal signal output by the inverter.

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