Converter disturbance impedance measurement method

Abstract

The application provides a variable current transformer variable disturbance impedance measurement method. A variable-amplitude disturbance signal is injected into the variable current transformer during impedance measurement, and the impedance and phase characteristics of the variable current transformer are determined based on current responses and voltage responses under different amplitude disturbances. The difference between the current impedance and phase characteristics and the previous impedance and phase characteristics is taken as an iteration end condition, so that the influence of the nonlinear behavior of the variable current transformer can be basically overcome, the impedance detection accuracy can be effectively ensured, and accurate data reference for subsequent operation and maintenance of the variable current transformer is provided.

Description

Technical Field

[0001] This invention relates to an impedance measurement method, and more particularly to a method for measuring the variable disturbance impedance of a converter. Background Technology

[0002] Converters are widely used as electrical equipment in fields such as power systems, aerospace equipment, and rail transportation. In order to assess the operating status of converters, it is necessary to measure their impedance and thus accurately assess their operating risks.

[0003] In existing technologies, impedance measurement of converters generally uses impedance measuring instruments. A fixed disturbance signal (typically a sinusoidal voltage disturbance signal) is injected into the converter using these instruments, and then the current and voltage responses of the converter are obtained. The impedance of the converter is then calculated. This method is based on the assumption that the converter's impedance changes linearly under any conditions. However, in reality, the converter's impedance changes with operating conditions, and the injected disturbances can induce nonlinear impedance behavior, such as modulator saturation or current limiter overshooting. Therefore, existing linear measurement methods cannot accurately obtain the converter's impedance characteristics.

[0004] Therefore, in order to solve the above-mentioned technical problems, it is urgent to propose a new technical approach. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for measuring the variable disturbance impedance of a converter. During impedance measurement, a disturbance signal with varying amplitude is injected into the converter, and the impedance and phase characteristics of the converter are determined based on the current response and voltage response under different amplitude disturbance conditions. The method uses the difference between the current impedance and phase characteristics and the previous impedance and phase characteristics as the termination condition for iteration. This method can essentially overcome the influence of the nonlinear behavior of the converter, effectively ensure the accuracy of impedance detection, and provide accurate data reference for the subsequent operation and maintenance of the converter.

[0006] The present invention provides a method for measuring the variable disturbance impedance of a converter, comprising the following steps:

[0007] S1. Set the frequency f and amplitude sequence A of the disturbance signal to be injected into the converter. i , where: A i =[A0, A1, A2, ..., A i A n ], and the amplitude sequence is from A0 to A n Gradually decrease;

[0008] S2. Let i=0, and inject a frequency of f and an amplitude of V into the converter under test. pert = Ai *V base The sinusoidal disturbance signal, where V base This indicates the rated operating voltage of the converter;

[0009] S3. Obtain the inverter's operating frequency f and amplitude V. pert The current and voltage responses under a sinusoidal disturbance signal, wherein the current response includes the phase a current response I. a,f and phase b current response I b,f The voltage response includes the voltage V between phases a and b. ab,f and the voltage V between phases b and c bc,f ;

[0010] S4. Determine the impedance data set Z based on voltage and current responses. prev =(|Z prev (f)|,∠Z prev (f)), where: |Z prev (f)| represents the impedance of the converter, ∠Z prev (f) indicates that the frequency is f and the amplitude is V. pert The lower phase of the sinusoidal disturbance signal;

[0011] S5. Let i = i + 1, and inject a frequency of f and an amplitude of V into the converter under test. pert = A i *V base The sinusoidal disturbance signal is obtained, and the converter is used at a frequency of f and an amplitude of V. pert Current and voltage responses under sinusoidal disturbance signals;

[0012] S6. Calculate impedance data set Z based on current and voltage responses at i=i+1. curr =(|Z curr (f)|,∠Z curr (f)); where: |Z curr (f)| represents the impedance of the current converter, ∠Z curr (f) indicates that the frequency is f and the amplitude is V at i=i+1. pert The lower phase of the sinusoidal disturbance signal;

[0013] S7. Determine the impedance data set Z curr and Z prev Does the set condition meet? If so, then change the current converter impedance |Z. curr (f)| As a detection result, if not, let Z prev =Z curr And return to step S6;

[0014] S8. When the iteration reaches a point where i is greater than n, then the impedance data group Z at i=n is...curr The converter impedance in the test is used as the test result.

[0015] Furthermore, the converter impedance |Z is determined using the following method. prev (f)|:

[0016] ;

[0017] Where: Re[] represents the real part of the converter impedance, Im[] represents the imaginary part of the converter impedance, e represents the natural constant, and π represents pi.

[0018] Furthermore, the converter impedance |Z is determined using the following method. curr (f)|:

[0019] ;

[0020] Where: Re[] represents the real part of the converter impedance, Im[] represents the imaginary part of the converter impedance, e represents the natural constant, and π represents pi.

[0021] Furthermore, the phase ∠Z is determined using the following method. prev (f):

[0022] .

[0023] Furthermore, in step S7, the conditions set include:

[0024] ||Z prev (f)|-|Z curr (f)||<α and|∠Z prev (f)-∠Z curr (f)|<β;

[0025] Where α and β represent the set threshold values.

[0026] The beneficial effects of this invention are as follows: By injecting a disturbance signal with varying amplitude into the converter during impedance measurement, and determining the impedance and phase characteristics of the converter based on the current and voltage responses under different amplitude disturbance conditions, and using the difference between the current impedance and phase characteristics and the previous impedance and phase characteristics as the iteration termination condition, the influence caused by the nonlinear behavior of the converter can be largely overcome, effectively ensuring the accuracy of impedance detection and providing accurate data reference for the subsequent operation and maintenance of the converter. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0028] Figure 1 This is a schematic diagram of the process of the present invention.

[0029] Figure 2 This is a schematic diagram of the measurement results using existing technology.

[0030] Figure 3 The waveforms show modulator saturation and nonlinear behavior in existing measurement methods.

[0031] Figure 4 This is a schematic diagram of the measurement results of the method of the present invention.

[0032] Figure 5 The waveform diagram of the modulator used in this invention to avoid nonlinear behavior. Detailed Implementation

[0033] The present invention will be further described in detail below:

[0034] The present invention provides a method for measuring the variable disturbance impedance of a converter, comprising the following steps:

[0035] S1. Set the frequency f and amplitude sequence A of the disturbance signal to be injected into the converter. i , where: A i =[A0, A1, A2, ..., A i A n ], and the amplitude sequence is from A0 to A n The amplitude gradually decreases. Generally, the maximum amplitude of the disturbance signal is 10% of the rated operating voltage of the converter, i.e., A0 = 0.1. Then the amplitudes of the remaining signals decrease sequentially. The specific decrease is set according to actual needs. For example, if the decrease is 0.01, then A1 is 0.09, A2 is 0.08, and so on until it reaches 0.01. At this point, n is 10. If the decrease is 0.005, and the process is repeated, then the value of n is 20.

[0036] S2. Let i=0, and inject a frequency of f and an amplitude of V into the converter under test. pert = A i *V base The sinusoidal disturbance signal, where V base This indicates the rated operating voltage of the converter;

[0037] S3. Obtain the inverter's operating frequency f and amplitude V. pert The current and voltage responses under a sinusoidal disturbance signal, wherein the current response includes the phase a current response I. a,f and phase b current response I b,f The voltage response includes the voltage V between phases a and b. ab,f and the voltage V between phases b and c bc,f ;

[0038] S4. Determine the impedance data set Z based on voltage and current responses. prev =(|Z prev (f)|,∠Z prev (f)), where: |Z prev (f)| represents the impedance of the converter, ∠Z prev (f) indicates that the frequency is f and the amplitude is V. pert The lower phase of the sinusoidal disturbance signal;

[0039] S5. Let i = i + 1, and inject a frequency of f and an amplitude of V into the converter under test. pert = A i *V base The sinusoidal disturbance signal is obtained, and the converter is used at a frequency of f and an amplitude of V. pert The current and voltage responses under a sinusoidal disturbance signal, specifically: the current response includes the phase a current response I. a,f，curr and phase b current response I b,f，curr The voltage response includes the voltage V between phases a and b. ab,f，curr and the voltage V between phases b and c bc,f，curr ;

[0040] S6. Calculate impedance data set Z based on current and voltage responses at i=i+1. curr =(|Z curr (f)|,∠Z curr (f)); where: |Z curr (f)| represents the impedance of the current converter, ∠Z curr (f) indicates that the frequency is f and the amplitude is V at i=i+1. pert The lower phase of the sinusoidal disturbance signal;

[0041] S7. Determine the impedance data set Z curr and Z prev Does the set condition meet? If so, then change the current converter impedance |Z. curr (f)| As a detection result, if not, let Z prev =Z curr And return to step S6;

[0042] S8. When the iteration reaches a point where i is greater than n, then the impedance data group Z at i=n is... curr The converter impedance in the circuit is used as the detection result. In the above process, if Z is determined when i=0... prev Z is determined when i=1 curr If the set conditions are met, then Z, which was determined when i=1, will be... curr |Z curr(f)|The impedance detection result of the converter is output. If the set conditions are not met, the Z value determined when i=1 will be used. curr As the previous impedance data set for the next calculation (i.e., when i=2), i.e., Z prev At this point, the impedance and phase at i=2 are calculated again. The impedance and phase at i=2 are subtracted from the impedance and phase at i=1, and the absolute values ​​are taken. Then, it is determined whether they are less than the set thresholds. If not, the iteration is performed. If the thresholds are met, the Z-axis at i=2 is set. curr |Z curr (f)|The impedance detection result of the converter is output. If it does not meet the requirements, iteration is required. If the value of i is greater than n during iteration, then the Z at i=n is... curr |Z curr (f)|The impedance detection result of the converter is output.

[0043] In this embodiment, the converter impedance |Z is determined by the following method. prev (f)|:

[0044] ;

[0045] Where: Re[] represents the real part of the converter impedance, Im[] represents the imaginary part of the converter impedance, e represents the natural constant, and π represents pi.

[0046] The converter impedance |Z is determined using the following method. curr (f)|:

[0047] ;

[0048] Where: Re[] represents the real part of the converter impedance, Im[] represents the imaginary part of the converter impedance, e represents the natural constant, and π represents pi.

[0049] The phase ∠Z is determined using the following method. prev (f):

[0050] Of course, phase ∠Z curr The structural form of the calculation formula for (f) and the phase ∠Z prev (f) is completely identical, except that the corresponding current response parameters and voltage response parameters are replaced accordingly.

[0051] In step S7, the conditions are set as follows:

[0052] ||Z prev (f)|-|Z curr (f)||<α and|∠Z prev (f)-∠Z curr(f)|<β;

[0053] Here, α and β represent the set threshold values. Using the above method, a disturbance signal with varying amplitude is injected into the converter during impedance measurement. Under different amplitude disturbance conditions, the impedance and phase characteristics of the converter are determined based on the current and voltage responses. The difference between the current and previous impedance and phase characteristics is used as the termination condition for the iteration. This effectively overcomes the influence of the converter's nonlinear behavior, ensuring the accuracy of impedance detection and providing accurate data references for subsequent converter operation and maintenance.

[0054] The following is a specific example to further illustrate this:

[0055] Figure 2 The Bode plot results for measuring converter impedance using the existing method described in the background art are shown. The solid line represents the analytical value of the mathematical model (obtained by experimentally modeling the converter, which is the prior art), and the dots represent the measurement results of the existing method. It can be seen from the figure that the measurement results deviate at certain frequencies. Figure 3 The waveform diagram shows the modulator saturation nonlinear behavior observed by existing measurement methods.

[0056] Figure 4 This is a Bode plot of the measurement results from this invention. The solid line represents the analytical values ​​of the mathematical model, i.e., the values ​​obtained by analyzing the impedance changes of the converter using the mathematical model obtained through experimental modeling of the converter using existing methods. The dots represent the measurement results of the method of this invention. Figure 4 It can be seen that the results obtained by the present invention and the analytical process agree well with the measurement results, thus proving the effectiveness of the present invention. Figure 5 The waveform diagram of the modulator in the measurement method of this invention shows that the modulation waveform is not greater than the carrier wave, and no waveform appears as shown in the diagram. Figure 3 The modulator saturation nonlinearity phenomenon in the medium.

[0057] It should also be noted that the methods described above are not only applicable to converters, but also to other three-phase electronic power equipment.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for measuring the variable disturbance impedance of a converter, characterized in that: Includes the following steps: S1. Set the frequency f and amplitude sequence A of the disturbance signal to be injected into the converter. i , where: A i =[A0, A1, A2, ..., A i A n ], and the amplitude sequence is from A0 to A n Gradually decrease; S2. Let i=0, and inject a frequency of f and an amplitude of V into the converter under test. pert = A i *V base The sinusoidal disturbance signal, where V base This indicates the rated operating voltage of the converter; S3. Obtain the inverter's operating frequency f and amplitude V. pert The current and voltage responses under a sinusoidal disturbance signal, wherein the current response includes the phase a current response I. a,f and phase b current response I b,f The voltage response includes the voltage V between phases a and b. ab,f and the voltage V between phases b and c bc,f ; S4. Determine the impedance data set Z based on voltage and current responses. prev =(|Z prev (f)|,∠Z prev (f)), where: |Z prev (f)| represents the impedance of the converter, ∠Z prev (f) indicates that the frequency is f and the amplitude is V. pert The lower phase of the sinusoidal disturbance signal; S5. Let i = i + 1, and inject a frequency of f and an amplitude of V into the converter under test. pert = A i *V base The sinusoidal disturbance signal is obtained, and the converter is used at a frequency of f and an amplitude of V. pert Current and voltage responses under sinusoidal disturbance signals; S6. Calculate impedance data set Z based on current and voltage responses at i=i+1. curr =(|Z curr (f)|,∠Z curr (f)); where: |Z curr (f)| represents the impedance of the current converter, ∠Z curr (f) indicates that the frequency is f and the amplitude is V at i=i+1. pert The lower phase of the sinusoidal disturbance signal; S7. Determine the impedance data set Z curr and Z prev Does the set condition meet? If so, then change the current converter impedance |Z. curr (f)| As a detection result, if not, let Z prev =Z curr And return to step S6; S8. When the iteration reaches a point where i is greater than n, then the impedance data group Z at i=n is... curr The converter impedance in the test is used as the test result.

2. The method for measuring the variable disturbance impedance of a converter according to claim 1, characterized in that: The converter impedance |Z is determined using the following method. prev (f)|: ； Where: Re[] represents the real part of the converter impedance, Im[] represents the imaginary part of the converter impedance, e represents the natural constant, and π represents pi.

3. The method for measuring the variable disturbance impedance of a converter according to claim 1, characterized in that: The converter impedance |Z is determined using the following method. curr (f)|: ； Where: Re[] represents the real part of the converter impedance, Im[] represents the imaginary part of the converter impedance, e represents the natural constant, and π represents pi.

4. The method for measuring the variable disturbance impedance of a converter according to claim 2, characterized in that: The phase ∠Z is determined using the following method. prev (f): 。 5. The method for measuring the variable disturbance impedance of a converter according to claim 1, characterized in that: In step S7, the conditions are set as follows: ||Z prev (f)|-|Z curr (f)||<α and |∠Z prev (f)-∠Z curr (f)|<β; Where α and β represent the set threshold values.

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