Adaptive bandwidth ultra-high-order harmonic detection method

Abstract

The invention discloses a self-adaptive bandwidth ultra-high-order harmonic detection method. The method comprises the following steps: S1, filtering: carrying out band-pass filtering on an original signal to obtain an ultra-high-order harmonic signal of 2-150kHz; s2, spectral analysis: performing spectral analysis by using 0.5 ms data to obtain frequency distribution of ultra-high-order harmonics; s3, adaptive filter detection: the initial center frequency of the adaptive filter is adjusted according to the frequency distribution of the ultra-high harmonic, and the adaptive filter tracks the frequency change and bandwidth change of the ultra-high harmonic; s4, ultra-high-order harmonic amplitude demodulation: the ultra-high-order harmonic amplitude is demodulated according to the amplitude output of the adaptive filter; and S5, ultra-high-order harmonic effective value calculation: aggregating the ultra-high-order harmonic amplitude demodulated in the step S4 into an effective value of a standard time length.

Description

Technical Field

[0001] The present invention relates to the technical field of signal processing and data analysis, and in particular to an adaptive bandwidth ultra-high-order harmonic detection method. Background Art

[0002] In recent years, with the promotion of renewable energy generation and various power supply equipment, the number of power electronic converters has increased rapidly on the source and load sides of the power system. At the same time, a large number of high-frequency interferences generated by switching devices have been injected into the power system. In addition, power line communication (PLC) will also generate ultra-high harmonics in the transmission line. In the distribution network, power electronic converters will inject ultra-high harmonic currents into the common connection point of the distribution network, generating secondary emissions through the line impedance. Ultra-high harmonics of specific frequencies may also resonate due to system impedance or transformer impedance, further expanding the propagation range of ultra-high harmonics in the low-voltage distribution network, and even entering the medium-voltage power grid through the transformer. The known hazards of ultra-high harmonic propagation in the distribution network to user equipment include: (1) equipment occasionally does not operate as expected or function is reduced; (2) equipment operation fails or is damaged; (3) interference with power line communication; (4) audible noise from equipment or devices. However, in the field of ultra-high harmonic measurement, appropriate ultra-high harmonic measurement methods are still under discussion.

[0003] The relevant international standards that can be used for ultra-high harmonic measurement are IEC 61000-4-7, IEC 61000-4-30 and CISPR 16-2-2. IEC 61000-4-7 and IEC 61000-4-30 are power quality measurement standards. Both of them put forward ultra-high harmonic measurement suggestions in the appendix, but they are not clearly stipulated. CISPR 16-2-2 is an equipment electromagnetic compatibility test standard, which is of reference significance for ultra-high harmonic measurement in power systems. The frequency resolution of the CISPR 16-2-1 method and the IEC 61000-4-7 method is 200Hz, and the detection amplitude is the same in most cases. However, the amount of data processed by these two methods is more than 10 times that of the IEC 61000-4-30 method. The disadvantage of the IEC 61000-4-30 method is that the frequency resolution is 2kHz, and this method only analyzes 8% of the measurement data. Summary of the invention

[0004] The purpose of the present invention is to provide an adaptive bandwidth ultra-high harmonic detection method. The existing standard test methods have their own advantages and disadvantages, and a more suitable measurement method is still needed to further realize the standardization of ultra-high harmonic measurement.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] An adaptive bandwidth ultra-high-order harmonic detection method comprises the following steps:

[0007] S1, filtering: band-pass filter the original signal to obtain the ultra-high harmonic signal of 2-150kHz;

[0008] S2. Spectrum analysis: Use 0.5ms data to perform spectrum analysis and obtain the frequency distribution of ultra-high harmonics;

[0009] S3, adaptive filter detection: adjust the initial center frequency of the adaptive filter according to the frequency distribution of the ultra-high harmonics, and the adaptive filter tracks the frequency change and bandwidth change of the ultra-high harmonics;

[0010] S4, ultra-high harmonic amplitude demodulation: demodulate the ultra-high harmonic amplitude according to the amplitude output of the adaptive filter;

[0011] S5. Calculation of effective value of ultra-high-order harmonics: Aggregate the amplitude of ultra-high-order harmonics demodulated in S4 into effective value of standard time length.

[0012] In some embodiments, in S1 , the original signal is band-pass filtered using a high-pass filter and a low-pass filter recommended by standard IEC 61000-4-30.

[0013] In some embodiments, S2 includes the following steps:

[0014] S21, taking 0.5ms of the filtered signal and performing fast Fourier analysis, a spectrum with a frequency resolution of 2kHz can be obtained;

[0015] S22. Take 75 spectral lines in the 2-150 kHz frequency band from the spectrum obtained in S21, and compare the frequencies of the 75 spectral lines and then sort them.

[0016] In some embodiments, the filtered ultra-high harmonic signal is:

[0017]

[0018] In the formula, A sh 、f sh , are the amplitude, frequency and phase angle of ultra-high harmonics respectively; SH is the upper limit of integration; n is the time sequence number; T s is the sampling time interval; N = 0.2 × f s , f s is the signal sampling frequency; sh is the integration number.

[0019] In some embodiments, the adaptive filter includes a bandpass filter and a sensitivity filter. The notch output e(n) of the previous adaptive filter can be connected to the signal input of the next adaptive filter, so as to realize adaptive filter cascading, and track the ultra-high harmonics in the 2-150kHz frequency band by cascading the adaptive filters.

[0020] In some embodiments, the transfer function of the bandpass filter is:

[0021]

[0022] The transfer function of the sensitivity filter is:

[0023]

[0024] Where a is the center frequency factor, which determines the center frequency of the bandpass filter; ρ is the bandwidth factor, which determines the passband bandwidth of the bandpass filter; z is the Z-transform operator; y(n) is the output of the bandpass filter; x(n) is the signal input; and e(n) is the output of the notch filter.

[0025] In some embodiments, the frequency distribution obtained by spectrum analysis is converted into initial parameters of an adaptive filter according to the transfer function of the bandpass filter and the transfer function of the sensitivity filter, and the corresponding ultra-high harmonics are continuously tracked by the adaptive filter;

[0026] The frequency tracking of ultra-high harmonics is achieved by updating the parameter a1:

[0027] a(n+1)=a(n)-μe(n)s(n);

[0028] The initial value of parameter a is:

[0029] a1(1)=-2cos(2πf1 / f s );

[0030] The sensitivity function is:

[0031] s(n)=x(n-1)-ρe(n-1);

[0032] Update the bandwidth of the adaptive filter by updating the parameter ρ:

[0033] ρ(n+1)=ρ(n)+0.0001y(n) 2 / (1-s(n)) 2 ;

[0034] Where μ is the step factor, which is 0.01; ρ is the bandwidth factor, with an initial value of 2000 / f s ; f1 is the frequency of the spectral line with the maximum amplitude, fs is the signal sampling frequency.

[0035] In some embodiments, in S4, after the ultra-high harmonic frequency is identified and tracked, the bandpass output of the adaptive filter is demodulated by the following calculation expression:

[0036]

[0037] in,

[0038] y sinf (n) = y(n)sin(2πf sh1 (n)n);

[0039] y cosf (n) = y(n)cos(2πf sh1 (n)n);

[0040] In the formula, f sh1 (n) is the ultra-high harmonic tracking frequency with the largest amplitude.

[0041] In some embodiments, in S4, since the bandpass output Y(n) obtained in S4 is an instantaneous effective value, the effective value of 200ms is calculated by the following expression:

[0042]

[0043] In the formula, f s is the signal sampling frequency.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention realizes frequency tracking and bandwidth adaptation of ultra-high-order harmonics based on an adaptive filter, and can effectively improve the measurement accuracy of broadband ultra-high-order harmonics by current ultra-high-order harmonic measurement methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic diagram of the overall process of the present invention;

[0047] Figure 2 It is a schematic diagram of the principle of the adaptive filter of the present invention;

[0048] Figure 3 It is a schematic diagram of the cascade structure of the adaptive filter of the present invention;

[0049] Figure 4 Schematic diagram of the analysis result of the steady-state ultra-high harmonic signal of the present invention; wherein (a), (b), and (c) are the detection effects of the method of the present invention on ultra-high harmonics of 10.05kHz, 75.001kHz, and 149.2kHz, respectively;

[0050] Figure 5 Schematic diagram of the broadband ultra-high-order harmonic signal analysis results of the present invention, wherein the detection effects of the method of the present invention on broadband ultra-high-order harmonics of 10.05kHz, 75.001kHz and 149.2kHz are respectively shown. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0052] Example 1

[0053] See also Figure 1-Figure 3 , an adaptive bandwidth ultra-high harmonic detection method, comprising the following steps:

[0054] S1, filtering;

[0055] The original signal is band-pass filtered to obtain an ultra-high harmonic signal of 2-150kHz; the high-pass filter and low-pass filter recommended by the standard IEC61000-4-30 are used to achieve band-pass filtering of ultra-high harmonics.

[0056] S2, spectrum analysis;

[0057] Use 0.5ms data for spectrum analysis to obtain the frequency distribution of ultra-high harmonics. The ultra-high harmonic signal after filtering is:

[0058]

[0059] In the formula, A sh 、f sh , are the amplitude, frequency and phase angle of ultra-high harmonics respectively; SH is the upper limit of integration; n is the time sequence number; T r is the sampling time interval; N = 0.2 × f s , f s is the signal sampling frequency; sh is the integration number.

[0060] After taking 0.5ms of the filtered signal for fast Fourier analysis, a spectrum with a frequency resolution of 2kHz can be obtained. Take 75 spectral lines in the 2-150kHz frequency band of the spectrum for comparison, set the frequency of the spectral line with the largest amplitude as f1, and set the frequencies of the other spectral lines as f2, f3, ..., f in order of magnitude. 75 .

[0061] S3, adaptive filter detection;

[0062] According to the frequency distribution of ultra-high harmonics f1, f2, ..., f 75 The initial center frequency of the adaptive filter is adjusted, and the adaptive filter tracks the frequency change and bandwidth change of the ultra-high harmonics.

[0063] like Figure 2 As shown, the adaptive filter includes a bandpass filter and a sensitivity filter, and the transfer function of the bandpass filter is:

[0064]

[0065] The transfer function of the sensitivity filter is:

[0066]

[0067] Where a is the center frequency factor, which determines the center frequency of the bandpass filter; ρ is the bandwidth factor, which determines the passband bandwidth of the bandpass filter; z is the Z-transform operator; y(n) is the output of the bandpass filter; x(n) is the signal input; and e(n) is the output of the notch filter.

[0068] like Figure 3 As shown, the notch signal output e(n) of the previous stage of the adaptive filter can be connected to the signal input of the next stage to achieve cascading. The ultra-high harmonic tracking of the 2-150kHz frequency band is achieved by cascading the adaptive filters. Taking the adaptive filter 1 as an example, the tracking process and how the frequency distribution in step S2 is converted into the initial parameters of the adaptive filter are explained.

[0069] Since the transfer functions of the bandpass filter and the sensitivity filter are related to the parameters, the relationship between the initial value of the parameter and the frequency distribution is:

[0070] a1(1)=-2cos(2πf1 / f s );

[0071] The frequency distribution obtained by spectrum analysis can be converted into the initial parameters of the adaptive filter, and the corresponding ultra-high harmonics can be tracked through the adaptive filter.

[0072] The frequency tracking of ultra-high harmonics is achieved by updating the parameter a1:

[0073] a(n+1)=a(n)-μe(n)s(n);

[0074] The sensitivity function is:

[0075] s(n)=x(n-1)-ρe(n-1);

[0076] Update the bandwidth of the adaptive filter by updating the parameter ρ:

[0077] ρ(n+1)=ρ(n)+0.0001y(n) 2 / (1-s(n)) 2 ;

[0078] Where μ is the step factor, which is 0.01; ρ is the bandwidth factor, with an initial value of 2000 / f s ; f1 is the frequency of the spectral line with the maximum amplitude, f s is the signal sampling frequency.

[0079] S4, ultra-high harmonic amplitude demodulation;

[0080] The ultra-high harmonic amplitude is demodulated according to the amplitude output of the adaptive filter. After the ultra-high harmonic frequency is identified and tracked, the bandpass output of the adaptive filter is demodulated by the following calculation expression:

[0081]

[0082] in,

[0083] y sinf (n) = y(n)sin(2πf sh1 (n)n);

[0084] y cosf (n) = y(n)cos(2πfs sh1 (n)n);

[0085] In the formula, f sh1 (n) is the ultra-high harmonic tracking frequency with the largest amplitude.

[0086] S5. Calculation of effective value of ultra-high harmonics;

[0087] Aggregate the amplitude of the ultra-high harmonics demodulated in S4 into the effective value of the standard time length. Since the bandpass output Y(n) obtained in S4 is an instantaneous effective value, the effective value of 200ms is calculated by the following expression:

[0088]

[0089] In the formula, f s is the signal sampling frequency.

[0090] Example 2

[0091] This embodiment verifies the measurement effect of the present invention on steady-state signals.

[0092] Steady-state signal frequency f sh1 、f sh2 and fsh3 Set to 10.05kHz, 75.001kHz and 149.2kHz respectively, amplitude A sh1 , A sh2 and A sh3 Set to 100mV, 80mV and 50mV respectively.

[0093] Figure 4 (a), (b), (c) respectively show the ultra-high harmonic detection effect of the present invention on 10.05kHz, 75.001kHz and 149.2kHz. The present invention starts to output the frequency detection results of 10050Hz, 75001Hz and 149200Hz at 0.073s, 0.088s and 0.087s respectively, and the effective value instantaneous output at 3s is 100.2mV, 80.2mV and 50.1mV respectively. The effective values ​​in the first 200ms cycle are 83.4mV, 66.4mV and 41.7mV respectively, and the effective values ​​in the subsequent 200ms cycle are 100mV, 80mV and 50mV respectively.

[0094] Example 3

[0095] This embodiment verifies the measurement effect of the present invention on broadband ultra-high-order harmonic signals.

[0096] Signal center frequency f sh1 、f sh2 and f sh3 The signal bandwidth is set to 10 Hz, 50 Hz and 100 Hz respectively, and the amplitude is set to 10.05 kHz, 75.001 kHz and 149.2 kHz respectively. sh1 , A sh2 and A sh3 Set to 100mV, 80mV and 50mV respectively.

[0097] Figure 5 (a), (b), (c) respectively show the broadband ultra-high harmonic detection effect of the present invention on 10.05kHz, 75.001kHz and 149.2kHz. The present invention starts to output the frequency detection results of 10050Hz, 75001Hz and 149200Hz at 0.075s, 0.089s and 0.093s respectively, and the effective value instantaneous output at 3s is 105.1mV, 84.0mV and 52.5mV respectively. The effective values ​​in the first 200ms cycle are 87.2mV, 69.7mV and 43.6mV respectively, and the effective values ​​in the subsequent 200ms cycle are 105mV, 84mV and 52.5mV respectively.

[0098] It can be seen that the present invention effectively detects broadband ultra-high-order harmonic signals.

[0099] The technical means disclosed in the scheme of the present invention are not limited to the technical means disclosed in the above-mentioned implementation mode, but also include technical schemes composed of any combination of the above-mentioned technical features. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also regarded as the protection scope of the present invention.

Claims

1. An adaptive bandwidth ultra-high harmonic detection method, characterized in that: The following steps are involved: S1, band-pass filter the original signal to obtain an ultra-high harmonic signal of 2-150kHz; S2. Use 0.5ms data to perform spectrum analysis and obtain the frequency distribution of ultra-high harmonics; S3, adjusting the initial center frequency of the adaptive filter according to the frequency distribution of the ultra-high harmonics, and the adaptive filter tracks the frequency change and bandwidth change of the ultra-high harmonics; S4, demodulating the amplitude of the ultra-high harmonics according to the amplitude output of the adaptive filter; S5. Aggregate the amplitude of the ultra-high harmonics demodulated in S4 into an effective value of a standard time length.

2. The adaptive bandwidth ultra-high harmonic detection method according to claim 1, characterized in that: In S1, the original signal is bandpass filtered using a high-pass filter and a low-pass filter.

3. The adaptive bandwidth ultra-high harmonic detection method according to claim 1, characterized in that: S2 includes the following steps: S21, take 0.5ms of the filtered signal and perform fast Fourier analysis to obtain a spectrum with a frequency resolution of 2kHz: S22. Take 75 spectral lines in the 2-150 kHz frequency band from the spectrum obtained in S21, and compare the frequencies of the 75 spectral lines and then sort them.

4. The adaptive bandwidth ultra-high harmonic detection method according to claim 2, characterized in that: The ultra-high harmonic signal after filtering is: In the formula, A sh 、f sh , are the amplitude, frequency and phase angle of ultra-high harmonics respectively; SH is the upper limit of integration; n is the time sequence number; T s is the sampling time interval; N = 0.2 × f s , f s is the signal sampling frequency; sh is the integration number.

5. The adaptive bandwidth ultra-high harmonic detection method according to claim 1, characterized in that: The adaptive filter comprises a bandpass filter and a sensitivity filter, and tracks ultra-high harmonics in the 2150kHz frequency band by cascading the adaptive filters.

6. The adaptive bandwidth ultra-high harmonic detection method according to claim 5, characterized in that: The transfer function of the bandpass filter is: The transfer function of the sensitivity filter is: Where a is the center frequency factor, which determines the center frequency of the bandpass filter; ρ is the bandwidth factor, which determines the passband bandwidth of the bandpass filter; z is the Z-transform operator; y(n) is the output of the bandpass filter; x(n) is the signal input; and e(n) is the output of the notch filter.

7. The adaptive bandwidth ultra-high harmonic detection method according to claim 6, characterized in that: According to the transfer function of the bandpass filter and the transfer function of the sensitivity filter, the frequency distribution obtained by the spectrum analysis is converted into the initial parameters of the adaptive filter, and the corresponding ultra-high harmonics are continuously tracked through the adaptive filter; The frequency tracking of ultra-high harmonics is achieved by updating the parameter a1: a(n+1)=a(n)-μe(n)s(n); The initial value of parameter a is: a1(1)=-2cos(2πf1 / f s ); The sensitivity function is: s(n)=x(n-1)-ρe(n-1); Update the bandwidth of the adaptive filter by updating the parameter ρ: p(n+1)=p(n)+0.0001y(n) 2 / (1-s(n)) 2 ; Where μ is the step factor, which is 0.01; ρ is the bandwidth factor, with an initial value of 2000 / f s ; f1 is the frequency of the spectral line with the maximum amplitude, f s is the signal sampling frequency.

8. The adaptive bandwidth ultra-high harmonic detection method according to claim 1, characterized in that: In S4, after the ultra-high harmonic frequency is identified and tracked, the bandpass output of the adaptive filter is demodulated by the following calculation expression: in, y sinf (n)=y(n)sin(2πf sh1 (n)n); y cosf (n)=y(n)cos(2πf sh1 (n)n)? In the formula, f sh1 (n) is the ultra-high harmonic tracking frequency with the largest amplitude.

9. The adaptive bandwidth ultra-high harmonic detection method according to claim 8, characterized in that: In S4, since the bandpass output Y(n) obtained in S4 is an instantaneous effective value, the effective value of 200ms is calculated by the following expression: In the formula, f s is the signal sampling frequency.

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