High-precision measuring method and device for harmonic waves / inter-harmonic waves of power broadband signals

Abstract

The invention discloses a power broadband signal harmonic / inter-harmonic high-precision measurement method and device. The method comprises the following steps: constructing a constrained N-element linear equation set for solution according to a windowed signal spectrum asymptotic expression, designing a normalized N-order W-window function with the performance of analyzing a digital frequency interpolation coefficient and a minimum sidelobe, performing double weighting on a broadband signal by using different-order W-windows, performing spectrum density detection based on an amplitude spectrum, and determining the spectrum density of the broadband signal according to the detected spectrum density. And a W window frequency interpolation factor and a correction formula are adaptively switched according to a detection spectral line difference value to measure a broadband signal. The method does not need to fit a frequency interpolation coefficient, is small in calculation amount, is high in robustness, is easy to achieve, and effectively achieves the real-time high-precision measurement of harmonic / inter-harmonic parameters in a broadband range.

Description

Technical Field

[0001] The present invention belongs to the technical field of broadband signal measurement in electric power systems, and in particular relates to a method and device for high-precision measurement of harmonics / interharmonics of broadband electric power signals. Background Art

[0002] With the increasing number of power electronic devices in new power systems, the problem of dynamic interference in power signals is increasing. Among them, harmonics and interharmonics have the most extensive impact, which has a serious impact on the stable operation of the power grid and power quality analysis, broadband oscillation monitoring and early warning. Therefore, high-precision monitoring of broadband power signals in new power systems has become particularly important to ensure the efficient and safe operation of the power system. The "double high" characteristics of the new power system have created new signal measurement technology requirements.

[0003] Traditional power signal harmonic / interharmonic measurement methods can be divided into the following categories: discrete frequency domain transformation method, signal space spectrum estimation method, least squares (RLS) state estimation method, and adaptive parameter estimation method based on artificial intelligence neural network, etc. Among them, the traditional discrete frequency domain transformation method produces fence effect and spectrum leakage during measurement due to asynchronous sampling, which greatly affects the measurement accuracy of signal parameters, and spectral interference between similar frequencies cannot be distinguished; the signal space spectrum estimation method can effectively reduce the influence of noise and has high measurement accuracy, but its calculation cost is too high and the frequency resolution ability is insufficient, making it difficult to apply in real time in broadband measurement devices; the RLS method has high requirements for the accuracy of the state space modeling of the signal, and there is an algorithm saturation phenomenon; the artificial intelligence algorithm can accurately analyze the signal, but the accuracy of its parameter estimation depends on the accuracy of the initial value and the number of components. If the frequency error is too large, the algorithm will not converge.

[0004] Therefore, it is necessary to propose a new high-performance broadband signal harmonic / interharmonic measurement algorithm that takes into account both computational efficiency, measurement accuracy, and numerical stability, and to design a corresponding broadband measurement device implementation framework. Summary of the invention

[0005] Purpose of the invention: In view of the deficiencies in the prior art, the present invention provides a method and device for high-precision measurement of harmonics / interharmonics of electric power broadband signals, so as to achieve efficient and accurate measurement of harmonic / interharmonic component parameters in broadband signals.

[0006] Technical solution: In the first aspect, a high-precision measurement method for harmonics / interharmonics of a power broadband signal comprises the following steps:

[0007] For a single frequency signal in the time domain, N sA discrete Fourier transform is performed in a weighted form of a window to obtain its discrete spectrum, and the spectrum ratio of adjacent spectral lines at the current frequency is calculated according to the discrete spectrum of the windowed signal and the asymptotic expansion of the window function; a polynomial about the digital frequency interpolation coefficient is obtained using the simplified form of the spectral line ratio expression, and a system of N-variable linear equations is constructed with the normalization of the window function as a condition and the analytical form of the digital frequency interpolation coefficient as the goal, the window function coefficient of the W window is solved, and the time domain expression of the N-order W window is obtained, and the double-spectrum analytical frequency interpolation method is used to obtain the amplitude correction corresponding to the N-order W window and the analytical form of the frequency interpolation coefficient;

[0008] Based on the obtained N-order W window, a low-order W window with a relatively narrow main lobe of the amplitude-frequency function and a high-order W window with a relatively wide main lobe are used to weight the broadband signal with a truncated window length of L, respectively, to obtain two types of windowed signals, and discrete Fourier transform is performed on the original truncated signal and the two types of windowed signals, respectively, to obtain discrete spectra, and frequency component detection is performed according to the amplitude spectrum of the original signal spectrum to obtain spectral lines at each frequency component; the frequency difference between each detected spectral line and its upper and lower spectral lines is calculated to obtain a frequency difference sequence within the entire spectrum range; according to the front and back difference sequences of each spectral line, it is judged whether the difference of the currently detected spectral line is less than a given threshold, and if so, the signal parameters are calculated using the discrete spectrum of the low-order W window with a relatively narrow main lobe width and the interpolation correction formula; otherwise, the discrete spectrum of the high-order W window with a relatively wide main lobe width and the correction formula are used for calculation.

[0009] Furthermore, according to the discrete spectrum of the windowed signal and the asymptotic expansion of the window function, the spectrum ratio of adjacent spectral lines at the current frequency is calculated, including:

[0010] A cosine window is selected for window function design. According to the discrete spectrum of the windowed signal and the asymptotic expansion of the trigonometric function of the cosine window, the approximate expression of the spectrum ratio of adjacent spectral lines at the current frequency after the weighting of the cosine window function is calculated:

[0011]

[0012] Among them, X λp (l) represents the form of the discrete spectrum at line l, expressed as H(λ p ,l,{a k}) represents the amplitude ratio between adjacent spectral lines in the discrete spectrum, λ p is the digital frequency interpolation coefficient, a k+1 is the window function coefficient.

[0013] Furthermore, the simplified form of the spectrum line ratio expression is used to obtain the polynomial about the digital frequency interpolation coefficient, and the N-variable linear equations are constructed with the normalization of the window function as the condition to obtain the analytical form of the digital frequency interpolation coefficient, including:

[0014] According to H(λp ,l,{a k}), simplify it into the following formula, and then use H(λ p ,l,{a k}) to represent the digital frequency interpolation coefficient λ p :

[0015]

[0016] About the digital frequency interpolation coefficient λ p The polynomial refers to Let all coefficients of i>0 be 0, and we get the following N-variable linear equation system:

[0017]

[0018] Among them, β i,j Represents the weight corresponding to the jth window function coefficient in the 2ith order coefficient of the polynomial, Represents the 2i-degree term in a polynomial The corresponding complete coefficient.

[0019] Furthermore, the window function coefficients of the W window are solved to obtain the time domain expression of the N-order W window, including:

[0020] Solve the N-variable linear equation system to find the unique solution of the window function coefficient of the W window N p Represents the window length truncated by discrete Fourier transform. The general form of cosine window is selected to design W window. The time domain expression of N-order cosine W window is:

[0021] Furthermore, the analytical forms of the amplitude correction and frequency interpolation coefficients corresponding to the N-order cosine W window are expressed as follows:

[0022]

[0023] Among them, A c (p) is the amplitude correction corresponding to the N-order cosine W window, λ p (N s ) is the frequency interpolation coefficient corresponding to the N-order cosine W window.

[0024] Furthermore, the formulas required for the N-order cosine W window frequency interpolation correction and phase angle correction calculation are expressed as follows:

[0025]

[0026] where f p (N s ) represents the corrected digital frequency; Φ p (λ p) represents the corrected phase angle, angle represents the complex angle function, f s Indicates the sampling frequency.

[0027] In a second aspect, a power broadband signal measuring device comprises:

[0028] The synchronous sampling module performs synchronous sampling of signals based on clock data and analog-to-digital conversion to obtain digital signals, and removes frequency components above the Nyquist sampling effective data frequency band in the input signal through low-pass analog filtering;

[0029] A data storage unit for storing signal dynamic recording, continuous recording, transient recording data, and device configuration files and log files;

[0030] A broadband signal calculation module performs spectrum analysis based on the effective signal obtained by synchronous sampling and low-pass filtering using the high-precision measurement method for harmonics / interharmonics of broadband power signals described in the first aspect of the present invention to obtain parameter measurement values ​​of harmonics / interharmonics within the full frequency range;

[0031] The data uploading module, according to the communication protocol, uses the time-division multiplexing method to upload the calculated harmonic component parameters of the previous whole second in the order of 1 to N harmonics in the phase quantity and frequency channel, and uploads a group of harmonic parameters in each frame according to the set frame number Fs; for the calculated interharmonic component parameters, the interharmonics calculated at the whole second are sent in order from high to low according to the amplitude according to the set frame number, and a group of interharmonic parameters are uploaded in each frame; the harmonic voltage, current amplitude and frequency are uploaded from the A / B / C phase channels of the device phasor and analog quantity respectively; the interharmonic voltage, current amplitude and frequency are uploaded from the A / B / C phase channels of the device phasor and analog quantity respectively.

[0032] In a third aspect, the present invention further provides a high-precision measurement system for harmonics / interharmonics of a power broadband signal, comprising:

[0033] N-order W window design module is used to design N single frequency signals in the time domain. s A discrete Fourier transform is performed in a weighted form of a window to obtain its discrete spectrum, and the spectrum ratio of adjacent spectral lines at the current frequency is calculated according to the discrete spectrum of the windowed signal and the asymptotic expansion of the window function; a polynomial about the digital frequency interpolation coefficient is obtained using the simplified form of the spectral line ratio expression, and a system of N-variable linear equations is constructed with the normalization of the window function as a condition and the analytical form of the digital frequency interpolation coefficient as the goal, the window function coefficient of the W window is solved, and the time domain expression of the N-order W window is obtained, and the double-spectrum analytical frequency interpolation method is used to obtain the amplitude correction corresponding to the N-order W window and the analytical form of the frequency interpolation coefficient;

[0034] The double weighted correction measurement module is used to weight the broadband signal with a truncated window length of L based on the obtained N-order W window, using a low-order W window with a relatively narrow main lobe of the amplitude-frequency function and a high-order W window with a relatively wide main lobe, respectively, to obtain two types of windowed signals, and to perform discrete Fourier transform on the original truncated signal and the two types of windowed signals respectively to obtain discrete spectra, perform frequency component detection according to the amplitude spectrum of the original signal spectrum, and obtain spectral lines at each frequency component; calculate the frequency difference between each detected spectral line and its upper and lower spectral lines, and obtain a frequency difference sequence within the entire spectrum range; determine whether the difference of the currently detected spectral line is less than a given threshold value according to the front and rear difference sequences of each spectral line, and if so, use the discrete spectrum of the low-order W window with a relatively narrow main lobe width and the interpolation correction formula to calculate the signal parameters; otherwise, use the discrete spectrum of the high-order W window with a relatively wide main lobe width and the correction formula to calculate.

[0035] In a fourth aspect, the present invention provides a computer device comprising: one or more processors; a memory; and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and when the programs are executed by the processors, the steps of the high-precision measurement method of harmonics / interharmonics of electric power broadband signals as described in the first aspect are implemented.

[0036] In a fifth aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the high-precision measurement method for harmonics / interharmonics of electric power broadband signals as described in the first aspect.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) According to the asymptotic expansion and the solution of the linear equations, an N-order W window function with analytical digital frequency interpolation coefficients and the maximum sidelobe attenuation rate is designed to reduce the influence of spectrum leakage after signal weighting, and analytical frequency interpolation can avoid the complex calculation of polynomial coefficient fitting, reduce the time cost of frequency interpolation, and improve the measurement efficiency of broadband signals. Since the cosine window interpolation form is simple, the invention adopts the cosine window for W window design; this construction method can also be extended to multiple non-cosine windows (Gaussian windows, etc.) according to different requirements of interpolation efficiency and performance.

[0039] (2) According to the main lobe width and side lobe attenuation properties of the window, the signal is doubly weighted using a low-order W window with a narrow main lobe and a high-order W window with a faster side lobe attenuation. The spectral line difference is detected based on the original frequency domain transform amplitude spectrum. The frequency interpolation correction method based on different order W windows is adaptively switched for frequency components of different density, thereby minimizing the influence of spectrum leakage and spectral line interference between components with similar frequencies to achieve efficient and accurate measurement of all harmonic / interharmonic parameters in a wide frequency range. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A flow chart of the broadband signal measurement method provided in the present invention;

[0041] Figure 2 Partial waveform diagram of the broadband signal used in the simulation test of the present invention;

[0042] Figure 3 Part of the harmonic / interharmonic measurement spectrum diagram of the simulation test of the present invention;

[0043] Figure 4 It is a comparison of the measurement errors of various components in the simulation test of the present invention;

[0044] Figure 5 This is the implementation system framework of the broadband signal measurement device provided by the present invention. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings.

[0046] Embodiment 1

[0047] In the present embodiment, a high-precision measurement method for harmonics / interharmonics of a wideband electric power signal is provided. The main idea of ​​the method is as follows: based on asymptotic expansion and solving a set of linear equations, an N-order W window function with analytical digital frequency interpolation coefficients and maximum sidelobe attenuation rate is designed, and according to the main lobe width and sidelobe attenuation properties of the window, different orders of W windows are used to perform doubly weighted weighting on the signal, and the spectral line difference is detected based on the original frequency domain transform amplitude spectrum, and frequency interpolation correction methods based on different orders of W windows are adaptively switched for frequency components of different densities, so as to accurately and efficiently measure all harmonic / interharmonic parameters within a wide frequency range.

[0048] Reference Figure 1 The high-precision measurement method for harmonics / interharmonics of a broadband power signal of the present invention specifically comprises the following steps:

[0049] Step S1, designing an N-order W window with analytical frequency interpolation coefficients.

[0050] S1-1, firstly, the single frequency signal u in the time domain p (t) = A p cos(2πΔf(l+λ p )k+φ p ) s The discrete Fourier transform (DFT) with a truncated length of L is performed in the weighted form of the window, where N sRefers to the number of terms in the general form of the window function (since the designed window function has not yet been introduced here, it indicates the number of terms). The physical meaning is the number of components superimposed in the window function, which is equivalent to the window order N in the proposed window function. The discrete spectrum of the windowed signal is obtained by DFT. The general form expression at the spectral line l is It is expressed as:

[0051] Among them, A p ,φ p Represents the amplitude and phase angle of a single signal, N p represents the window length truncated by DFT, λ p is the digital frequency interpolation coefficient, a k+1 represents the window function coefficient, Δf represents the frequency resolution, and f + (λ p ,k),f - (λ p ,k) represents the conjugate component in the discrete spectrum.

[0052] S1-2, since the sampling window length L is a large integer, according to the discrete spectrum of the windowed signal and the asymptotic expansion of the trigonometric function of the cosine window, the approximate expression of the spectrum ratio of adjacent spectral lines at the current frequency after the cosine form window function is weighted is calculated:

[0053]

[0054] S1-3, using the simplified form of the spectrum line ratio expression to obtain the polynomial about the digital frequency interpolation coefficient, and taking the window function normalization as a condition, constructing an N-variable linear equation group with the goal of obtaining the analytical form of the digital frequency interpolation coefficient.

[0055] According to the amplitude ratio H(λ between adjacent spectral lines in the DFT spectrum p ,l,{a k}), it can be simplified into the following formula, so that H(λ p ,l,{a k}) to represent the digital frequency interpolation coefficient λ p :

[0056]

[0057] About the digital frequency interpolation coefficient λ p The polynomial refers to If we set all coefficients of the items i>0 to 0, we can get the following N-dimensional linear equation system:

[0058]

[0059] Among them, β i,jIt represents the weight corresponding to the j-th window function coefficient in the 2i-th order term coefficient in the polynomial, as shown in Table 2. Represents the 2i-degree term in a polynomial The corresponding complete coefficient.

[0060] S1-4, solve the unique solution of the window function coefficient of W window according to the above full rank linear equations The time domain expression of the N-order cosine W window is obtained:

[0061]

[0062] Table 1 shows the 3-7 order window function coefficients of the cosine W window solved by constructing a linear equation system. The orders used in the embodiment of the present invention are 3rd and 5th order.

[0063] Table 1 Window function coefficients of the proposed N-order cosine W window

[0064] <![CDATA[a 1 ]]> <![CDATA[a 2 ]]> <![CDATA[a 3 ]]> <![CDATA[a 4 ]]> <![CDATA[a 5 ]]> <![CDATA[a 6 ]]> <![CDATA[a 7 ]]> 3rd-order W window 3 / 8 1 / 2 1 / 8 4th-order W window 5 / 16 15 / 32 3 / 16 1 / 32 5th-order W window 35 / 128 7 / 16 7 / 32 1 / 16 1 / 128 6th-order W window 63 / 256 105 / 256 15 / 64 45 / 512 5 / 256 1 / 512 7th-order W window 231 / 1024 99 / 256 495 / 2048 55 / 512 33 / 1024 3 / 512 1 / 2048

[0065] The window function coefficient solution equations of the constructed 3rd-order and 5th-order W windows are as follows:

[0066] ·About the polynomial formula of cosine type digital frequency interpolation coefficients:

[0067]

[0068] in N s The polynomial form corresponding to the window function; λ p Represents the digital frequency interpolation coefficient, a k Represents the kth window function coefficient.

[0069] ·3rd order window function coefficient solution:

[0070]

[0071] ·5th order window function coefficient solution:

[0072]

[0073] The coefficient of the equation β i,j By polynomial The part with zero in the middle is obtained, and the coefficients of the cosine type part are shown in Table 2 (the high-order general formula is more complicated, and it is usually calculated directly after specifying the n value). By constructing a linear equation group with a unique solution for the corresponding order window, the corresponding window function coefficients can be obtained.

[0074] Table 2 Cosine window form of partial equation coefficients n+1 order general formula

[0075]

[0076]

[0077] S1-5, using the dual-spectrum analytical frequency interpolation method, calculate the analytical form of the amplitude correction, phase correction and frequency interpolation coefficients corresponding to the N-order cosine W window, where the amplitude correction coefficient is expressed as:

[0078]

[0079] The analytical digital frequency interpolation coefficients are expressed as:

[0080]

[0081] The above frequency interpolation coefficients are used for interpolation, which avoids the non-analytical method of using high-order polynomials to fit the inverse function of the spectrum ratio in the traditional cosine window double spectrum interpolation method to obtain the frequency interpolation coefficients, thereby improving the computational efficiency of frequency interpolation. In addition, this construction method can also be extended to multinomial non-cosine windows (Gaussian windows, etc.).

[0082] Step S2: performing double-weighted adaptive spectrum correction of the signal based on an N-order W window.

[0083] S2-1, using the designed W window, the signal is subjected to window function weighted processing;

[0084] The present invention adopts different order W windows to perform double weighting on the signal according to the main lobe width and side lobe attenuation properties of the window, wherein a low order W window (the third order is selected in the embodiment) with a narrow main lobe of the amplitude-frequency function and a high order W window (the fifth order is selected in the embodiment) with a wide main lobe are used to respectively truncate the broadband signal U with a window length of L. L (t) is weighted to obtain the windowed signal and

[0085] S2-2, respectively, the original truncated signal U L (t), and the windowed signal and Perform DFT calculation to obtain the discrete spectrum X L (k) and

[0086] S2-3, according to the original signal spectrum X L The amplitude spectrum of (k) is used to detect the frequency components, and the spectrum line l at the kth frequency component is obtained. k ,k=1,2,...,N h , where N h is the number of harmonic / interharmonic components in the broadband signal;

[0087] S2-4, calculate the frequency difference between each detected spectrum line and its upper and lower spectrum lines, and obtain the frequency difference sequence e(l k )=max{f(l k+i )-f(l k+i-1 )},i=0,1, where f(l k ) represents the spectrum line l k The frequency corresponding to i = 0 corresponds to l k-1 ,l k The frequency difference between the two spectral lines, i = 1 corresponds to l k ,l k+1 The frequency difference between the two spectral lines, e(l k ) indicates the current detection spectrum line l k The maximum frequency difference on both sides of the

[0088] S2-5, according to the sequence of the previous and next differences of each spectral line, a threshold η is set to determine whether the difference of the currently detected kth spectral line is less than a given threshold, that is, to determine whether e(l k )<η, if so, it indicates that the frequency distribution of the current frequency band is dense, the spectral line interference is large, and the 3rd order W window with narrow main lobe width is used to discrete the spectrum The signal parameters are calculated with the interpolation correction formula; otherwise, it indicates that the frequency distribution of the current frequency band is relatively dispersed, the spectral line interference is small, and the 5th-order W window discrete spectrum with a wide main lobe width and a faster side lobe attenuation rate is used. Calculate with the correction formula;

[0089] Specifically, after the threshold is determined, the spectrum obtained by double weighting of the signal is calculated according to the amplitude correction calculation formula composed of the 3rd order W window and the 5th order W window. The calculation formula of frequency interpolation coefficient Perform spectrum correction, where the frequency correction calculation formula is: The phase angle correction calculation formula is: where f p (N s ) represents the corrected digital frequency; Φ p (λ p ) represents the corrected phase angle, angle represents the complex angle function, f s Indicates the sampling frequency.

[0090] Step S2-6, determine whether k is the last frequency component detected, if so, end the loop and output all component parameters; otherwise, continue with step S2-3 until all frequency components are detected.

[0091] In order to verify the performance of the proposed method, a simulation test was carried out in the embodiment. Figure 2Part of the waveform diagram of the broadband signal used in the simulation test. The set test broadband signal superimposed 40 components, including 1 fundamental wave and 39 harmonics / interharmonics. The frequency intervals between components other than the fundamental wave were randomly switched at 1.5Hz, 5Hz and 100Hz, and the phase angle and amplitude were randomly assigned, so as to achieve a more complete simulation algorithm to measure the performance under different signal conditions.

[0092] Figure 3 The following is a partial harmonic / interharmonic measurement spectrum diagram of the simulation test using the method of the present invention. The sliding window sampling calculation is performed using the sampling frequency Fs = 12.8k and the window length L = 2^15, and each sliding window collects 2.56s of data. It can be seen that the method proposed in the present invention overcomes the amplitude averaging effect caused by the spectrum leakage of the original signal, as well as the influence of signal windowing on the resolution of similar frequencies, and accurately estimates the parameters of each component in the original signal through the double weighted adaptive switching spectrum correction method.

[0093] Figure 4 In order to compare the measurement errors of each component in the simulation test, the 4-term 5th-order Nuttall window interpolation FFT algorithm with high spectrum correction accuracy is used in the experiment to compare the measurement effects. It can be seen from the measurement results that in the frequency band where the frequencies between components are far apart, due to the absence of spectral line interference, the measurement accuracy of the proposed method and the comparison method is high, but the measurement accuracy of the proposed method is still higher than that of the comparison method; in the frequency band where the components are densely distributed, the measurement accuracy of the proposed method is much higher than that of the comparison method. This is because although the 4-term 5th-order Nuttall window has a fast sidelobe attenuation rate and can effectively suppress spectrum leakage, its amplitude-frequency main lobe is too wide, resulting in a reduction in the resolution of similar frequencies after windowing; the proposed method can switch the correction method between the 3rd-order W window with a narrower main lobe and the 5th-order W window with a wider main lobe through double weighting and spectral line difference judgment, realizing the adaptive measurement of broadband components.

[0094] Table 3 shows the harmonic / interharmonic setting values ​​and corresponding measurement errors used in the proposed method for simulation testing. The amplitude error is represented by the proportion of the measured harmonic / interharmonic amplitude, while the phase angle and frequency measurement errors are represented by the original units of the measured data. According to the measurement results, the maximum frequency error is 0.00338Hz, the amplitude error accounts for 0.288% of the current component amplitude, and the maximum phase angle error is 1.556 degrees, which are lower than the relevant industry standards.

[0095] Table 3. Setting values ​​of harmonic / interharmonic parameters of broadband signal and measurement error of the proposed method

[0096]

[0097]

[0098] Embodiment 2

[0099] Reference Figure 5 This embodiment provides a power broadband signal measuring device, comprising:

[0100] The synchronous sampling module performs synchronous sampling of signals based on clock data and ADC (analog-to-digital conversion) to obtain digital signals, and filters out frequency components above the Nyquist sampling effective data frequency band in the input signal through preprocessing means such as low-pass analog filtering to prevent frequency aliasing;

[0101] A data storage unit (not shown in the figure) stores signal dynamic recording, continuous recording, transient recording data, device configuration files, log files, etc.;

[0102] The broadband signal calculation module performs spectrum analysis based on the effective signal obtained by synchronous sampling and data preprocessing using the high-precision measurement method for harmonics / interharmonics of broadband power signals described in Example 1 to obtain parameter measurement values ​​of harmonics / interharmonics within the full frequency range;

[0103] The data uploading module, according to the GBT 26865.2-2011 communication protocol, uses the time-division multiplexing method to upload the calculated harmonic component parameters of the previous whole second in phase quantities and frequency channels in the order of 1 to N harmonics, and uploads a group of harmonic parameters in each frame according to the set frame number Fs; for the calculated interharmonic component parameters, the interharmonics calculated at the whole second are sent in order from high to low according to the amplitude according to the set frame number, and a group of interharmonic parameters are uploaded in each frame; the three-phase harmonics, interharmonic voltage, current amplitude, and frequency are uploaded from the A\B\C phase channel of the device phase quantity and the A\B\C phase channel of the analog quantity respectively.

[0104] Embodiment 3

[0105] This embodiment provides a high-precision measurement system for harmonics / interharmonics of a power broadband signal, including:

[0106] N-order W window design module is used to design N single frequency signals in the time domain. s A discrete Fourier transform is performed in a weighted form of a window to obtain its discrete spectrum, and the spectrum ratio of adjacent spectral lines at the current frequency is calculated according to the discrete spectrum of the windowed signal and the asymptotic expansion of the window function; a polynomial about the digital frequency interpolation coefficient is obtained using the simplified form of the spectral line ratio expression, and a system of N-variable linear equations is constructed with the normalization of the window function as a condition and the analytical form of the digital frequency interpolation coefficient as the goal, the window function coefficient of the W window is solved, and the time domain expression of the N-order W window is obtained, and the double-spectrum analytical frequency interpolation method is used to obtain the amplitude correction corresponding to the N-order W window and the analytical form of the frequency interpolation coefficient;

[0107] The double weighted correction measurement module is used to weight the broadband signal with a truncated window length of L based on the obtained N-order W window, using a low-order W window with a relatively narrow main lobe of the amplitude-frequency function and a high-order W window with a relatively wide main lobe, respectively, to obtain two types of windowed signals, and to perform discrete Fourier transform on the original truncated signal and the two types of windowed signals respectively to obtain discrete spectra, perform frequency component detection according to the amplitude spectrum of the original signal spectrum, and obtain spectral lines at each frequency component; calculate the frequency difference between each detected spectral line and its upper and lower spectral lines, and obtain a frequency difference sequence within the entire spectrum range; determine whether the difference of the currently detected spectral line is less than a given threshold value according to the front and rear difference sequences of each spectral line, and if so, use the discrete spectrum of the low-order W window with a relatively narrow main lobe width and the interpolation correction formula to calculate the signal parameters; otherwise, use the discrete spectrum of the high-order W window with a relatively wide main lobe width and the correction formula to calculate.

[0108] It should be understood that the high-precision measurement system for harmonics / interharmonics of electric power broadband signals provided in this embodiment can implement all the technical solutions in the above-mentioned method embodiments, and the functions of its various functional modules can be specifically implemented according to the methods in the above-mentioned method embodiments. The specific implementation process can refer to the relevant description in the above-mentioned embodiments, which will not be repeated here.

[0109] Embodiment 4

[0110] This embodiment provides a computer device, which includes one or more processors; a memory; and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and when the programs are executed by the processors, the steps of a high-precision measurement method for harmonics / interharmonics of a wide-band power signal are implemented as described in Embodiment 1.

[0111] Embodiment 5

[0112] This embodiment provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the high-precision measurement method for harmonics / interharmonics of a power broadband signal as described in the first embodiment are implemented.

[0113] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, devices (systems), computer equipment or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0114] The present invention is described with reference to a flowchart of a method according to an embodiment of the present invention. It should be understood that each process in the flowchart and a combination of processes in the flowchart can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the process in the flowchart. Figure 1 A device that specifies functions in a process or multiple processes.

[0115] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A function specified in a process or multiple processes.

[0116] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 The steps of a specified function in a process or multiple processes.

Claims

1. A high-precision measurement method for harmonics / interharmonics of power broadband signals, characterized in that: The following steps are involved: For a single frequency signal in the time domain, N s The discrete Fourier transform is performed in the weighted form of the window to obtain its discrete spectrum. According to the discrete spectrum of the windowed signal and the asymptotic expansion of the window function, the spectrum ratio of adjacent spectral lines at the current frequency is calculated; The simplified form of the spectrum line ratio expression is used to obtain the polynomial of the digital frequency interpolation coefficient, and the window function normalization is used as a condition to construct an N-variable linear equation system with the goal of obtaining the analytical form of the digital frequency interpolation coefficient. The window function coefficient of the W window is solved to obtain the time domain expression of the N-order W window. The double spectrum line analytical frequency interpolation method is used to obtain the analytical form of the amplitude correction and frequency interpolation coefficient corresponding to the N-order W window. Based on the obtained N-order W window, a low-order W window with a relatively narrow main lobe of the amplitude-frequency function and a high-order W window with a relatively wide main lobe are used to weight the broadband signal with a truncated window length of L, respectively, to obtain two types of windowed signals, and discrete Fourier transform is performed on the original truncated signal and the two types of windowed signals, respectively, to obtain discrete spectra, and frequency component detection is performed according to the amplitude spectrum of the original signal spectrum to obtain spectral lines at each frequency component; The frequency difference between each detected spectral line and its upper and lower spectral lines is calculated to obtain the frequency difference sequence in the entire spectrum range; according to the previous and next difference sequences of each spectral line, it is judged whether the difference of the currently detected spectral line is less than a given threshold. If so, the signal parameters are calculated using the discrete spectrum of a low-order W window with a relatively narrow main lobe width and the interpolation correction formula; otherwise, the discrete spectrum of a high-order W window with a relatively wide main lobe width and the correction formula are used for calculation.

2. The method according to claim 1, characterized in that According to the discrete spectrum of the windowed signal and the asymptotic expansion of the window function, the spectrum ratio of adjacent spectral lines at the current frequency is calculated, including: A cosine window is selected for window function design. According to the discrete spectrum of the windowed signal and the asymptotic expansion of the trigonometric function of the cosine window, the approximate expression of the spectrum ratio of adjacent spectral lines at the current frequency after the weighting of the cosine window function is calculated: in, Represents the discrete spectrum at line l in the form of H(λ p ,l,{a k }) represents the amplitude ratio between adjacent spectral lines in the discrete spectrum, λ p is the digital frequency interpolation coefficient, a k+1 is the window function coefficient.

3. The method according to claim 2, characterized in that The simplified form of the spectrum line ratio expression is used to obtain the polynomial of the digital frequency interpolation coefficient, and the N-variable linear equations are constructed with the normalization of the window function as the condition to obtain the analytical form of the digital frequency interpolation coefficient, including: According to H(λ p ,l,{a k }), simplify it into the following formula, and then use H(λ p ,l,{a k }) to represent the digital frequency interpolation coefficient λ p : About the digital frequency interpolation coefficient λ p The polynomial refers to Let all coefficients of i>0 be 0, and we get the following N-variable linear equation system: Among them, β i,j Represents the weight corresponding to the jth window function coefficient in the 2ith order coefficient of the polynomial, Represents the 2i-degree term in a polynomial The corresponding complete coefficient.

4. The method according to claim 3, characterized in that Solve the window function coefficients of the W window and obtain the time domain expression of the N-order W window, including: Solve the N-variable linear equation system to find the unique solution of the window function coefficient of the W window N p Represents the window length truncated by discrete Fourier transform. The general form of cosine window is selected to design W window. The time domain expression of N-order cosine W window is:

5. The method according to claim 2, characterized in that: The analytical forms of the amplitude correction and frequency interpolation coefficients corresponding to the N-order cosine W window are expressed as: Among them, A c (p) is the amplitude correction corresponding to the N-order cosine W window, λ p (N s ) is the frequency interpolation coefficient corresponding to the N-order cosine W window.

6. The method according to claim 2, characterized in that The formulas required for the N-order cosine W window frequency interpolation correction and phase angle correction calculation are expressed as follows: where f p (N s ) represents the corrected digital frequency; Φ p (λ p ) represents the corrected phase angle, angle represents the complex angle function, f s Indicates the sampling frequency.

7. A power broadband signal measuring device, characterized in that: include: The synchronous sampling module performs synchronous sampling of signals based on clock data and analog-to-digital conversion to obtain digital signals, and removes frequency components above the Nyquist sampling effective data frequency band in the input signal through low-pass analog filtering; A data storage unit for storing signal dynamic recording, continuous recording, transient recording data, and device configuration files and log files; A broadband signal calculation module, based on the effective signal obtained by synchronous sampling and low-pass filtering, uses the high-precision measurement method for harmonics / interharmonics of power broadband signals according to any one of claims 1 to 6 to perform spectrum analysis to obtain parameter measurement values ​​of harmonics / interharmonics within the full frequency range; The data uploading module, according to the communication protocol, uses the time-division multiplexing method to upload the calculated harmonic component parameters of the previous whole second in the order of 1 to N harmonics in the phase quantity and frequency channel, and uploads a group of harmonic parameters in each frame according to the set frame number Fs; for the calculated interharmonic component parameters, the interharmonics calculated at the whole second are sent in order from high to low according to the amplitude according to the set frame number, and a group of interharmonic parameters are uploaded in each frame; the harmonic voltage, current amplitude and frequency are uploaded from the A / B / C phase channels of the device phasor and analog quantity respectively; the interharmonic voltage, current amplitude and frequency are uploaded from the A / B / C phase channels of the device phasor and analog quantity respectively.

8. A high-precision measurement system for harmonics and interharmonics of power broadband signals, characterized in that: include: N-order W window design module is used to design N single frequency signals in the time domain. s The discrete Fourier transform is performed in the weighted form of the window to obtain its discrete spectrum. According to the discrete spectrum of the windowed signal and the asymptotic expansion of the window function, the spectrum ratio of adjacent spectral lines at the current frequency is calculated; The simplified form of the spectrum line ratio expression is used to obtain the polynomial of the digital frequency interpolation coefficient, and the window function normalization is used as a condition to construct an N-variable linear equation system with the goal of obtaining the analytical form of the digital frequency interpolation coefficient. The window function coefficient of the W window is solved to obtain the time domain expression of the N-order W window. The double spectrum line analytical frequency interpolation method is used to obtain the analytical form of the amplitude correction and frequency interpolation coefficient corresponding to the N-order W window. A double-weighted correction measurement module is used to weight the broadband signal with a truncated window length of L based on the obtained N-order W window, using a low-order W window with a relatively narrow main lobe of the amplitude-frequency function and a high-order W window with a relatively wide main lobe, to obtain two types of windowed signals, and to perform discrete Fourier transform on the original truncated signal and the two types of windowed signals, to obtain discrete spectra, and to perform frequency component detection according to the amplitude spectrum of the original signal spectrum to obtain spectral lines at each frequency component; The frequency difference between each detected spectral line and its upper and lower spectral lines is calculated to obtain the frequency difference sequence in the entire spectrum range; according to the previous and next difference sequences of each spectral line, it is judged whether the difference of the currently detected spectral line is less than a given threshold. If so, the signal parameters are calculated using the discrete spectrum of a low-order W window with a relatively narrow main lobe width and the interpolation correction formula; otherwise, the discrete spectrum of a high-order W window with a relatively wide main lobe width and the correction formula are used for calculation.

9. A computer device, characterized in that: include: one or more processors; Memory; And one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and when the programs are executed by the processors, the steps of the high-precision measurement method of harmonics / interharmonics of electric power broadband signals as described in any one of claims 1-6 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the high-precision measurement method for harmonics / interharmonics of a power broadband signal according to any one of claims 1 to 6 are implemented.

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