A three-phase distorted power grid sinusoidal signal filtering method based on sub-signal frequency estimation

Abstract

The present invention discloses a three-phase distorted power grid sinusoidal signal filtering method based on sub-signal frequency estimation, which belongs to the technical field of power grid signal analysis, and is used to solve the technical problem that the current signal filtering cannot truly filter out interference components and has low processing efficiency. The method specifically includes the steps of intercepting the sampled three-phase signal, filling it with zeros and writing it into a sub-signal matrix; performing discrete Fourier transform on each row of the sub-signal matrix to construct a filter matrix; filtering the sub-signal matrix with the filter matrix; performing inverse discrete Fourier transform on the filtered sub-signal matrix to obtain the filtered result. The present invention has the advantages of accurate interference filtering and high processing efficiency.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of power grid signal analysis, and in particular to a three-phase distorted power grid sinusoidal signal filtering method based on sub-signal frequency estimation. Background Art

[0002] The ideal power grid signal is a standard sinusoidal signal. However, due to the presence of a large number of nonlinear loads in the power grid and the intermittent characteristics of wind power, photovoltaic and other new energy power generation, the power grid signal is seriously distorted. For the distorted power grid sinusoidal signal, accurate parameter estimation has always been a difficult problem faced by both China and abroad.

[0003] Using carrier technology to modulate power grid signals and achieve two-way communication is an important means to meet the continuous deepening of business applications and the expansion of multi-professional functions of power grid power consumption information collection systems. However, traditional narrowband carrier technology has obvious limitations: low communication rate, susceptibility to interference, slow networking process, insufficient business support capabilities, etc. At present, power grid broadband carrier communication has received attention. It uses modulation technologies such as spread spectrum and OFDM (orthogonal frequency division multiplexing) to improve frequency band utilization, eliminate interference between channels, reduce signal passive absorption and sudden interference, and achieve high-speed and reliable data communication to meet the growing demand for information transmission. Therefore, the analysis of complex and distorted power grid signals, especially the extraction of broadband carrier parameters, urgently needs to be broken through.

[0004] The actual modulated power grid signal contains not only abundant harmonics and modulation waves, but also strong noise interference. The traditional method directly performs spectrum analysis after processing the sampled signal with a low-pass filter, which often fails to truly filter out the interference components. Especially for phase-modulated power grid signals, the filtering process in the traditional method does not take into account the characteristics of phase modulation, resulting in a large phase estimation deviation in the filtered result. In addition, the traditional method generally processes three-phase signals phase by phase, which is inefficient. Summary of the invention

[0005] The technical problem to be solved by the present invention is: in view of the technical problems existing in the prior art, the present invention provides a three-phase distorted power grid sinusoidal signal filtering method based on sub-signal frequency estimation for accurately filtering out interference.

[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0007] A three-phase distorted power grid sinusoidal signal filtering method based on sub-signal frequency estimation comprises the following steps:

[0008] The sampled three-phase signal is intercepted, filled with zeros and written into the sub-signal matrix;

[0009] Perform discrete Fourier transform on each row of the sub-signal matrix to construct a filter matrix;

[0010] Filtering the sub-signal matrix using a filter matrix;

[0011] Perform inverse discrete Fourier transform on the filtered sub-signal matrix to obtain the filtered result.

[0012] Preferably, the specific process of intercepting the sampled three-phase signal, filling it with zeros and writing it into the sub-signal matrix is ​​as follows: intercepting the sampled three-phase signal, the length of each phase signal is L, and filling the end of the intercepted three-phase signal with zeros, and filling the length with zeros to N DFT , write the sub-signal matrix x(p,n), where p = 1, 2, 3, representing the three phases A, B, and C respectively; n = 1, 2, 3, ..., N DFT ; N DFT is the first integer power of 2 greater than or equal to L; when N DFT = L, no zero padding is required; when L <N DFT When the three-phase signal is sampled, the last bit is padded with zero.

[0013] Preferably, the specific process of performing discrete Fourier transform on each row of the sub-signal matrix is: performing discrete Fourier transform on each row of the sub-signal matrix x(p,n) to obtain a complex spectrum matrix X D (p, k), k = 1, 2, 3, ..., N DFT , find X D The index number of the maximum modulus value in each row, denoted by i p , the subscript p represents the row number of the matrix.

[0014] Preferably, the specific process of constructing the filter matrix is ​​as follows: construct a filter matrix with a size of 3*N DFT The filter matrix F, where each row of F is a low-pass filter with a passband length of w, where the first w / 2 and last w / 2 elements of each row of F are 1, and the other intermediate elements are 0:

[0015]

[0016] Among them, ceil(w / 2) is the first integer greater than or equal to w / 2, and floor(w / 2) is the first integer less than or equal to w / 2;

[0017] Circularly shift row p of F to the right by i p -1 element, defining the resulting matrix as F R , by shifting the passband of the p-th row filter to X D Near the maximum modulus value of this row.

[0018] Preferably, the filter matrix FR Pair signal matrix X D Perform filtering;

[0019] X RD =X D ⊙F R (2)

[0020] Among them, ⊙ is the corresponding multiplication of matrix elements, X RD is the spectrum of the sub-signal matrix after filtering.

[0021] Preferably, the specific process of performing inverse discrete Fourier transform on the filtered sub-signal matrix to obtain the filtered result is:

[0022] X RD Each row is inversely discrete Fourier transformed to obtain the result matrix x RD (p,n);

[0023] x RD The 0s at the end of each row are removed to form a filter sub-signal matrix x of size 3*L F (p,l), where l = 1, 2, 3, ..., L, x F The pth row of is the filtering result x of the corresponding row signal f (p,l).

[0024] Preferably, after the filtering result is obtained, the length of each subsequent phase signal is L, which is adjusted using a quasi-maximum likelihood search strategy.

[0025] Preferably, the specific process of adjusting using the quasi-maximum likelihood search strategy is:

[0026] The filtering result x F Perform phase estimation on each row of (p,l) to obtain the phase estimation result φp of the pth row;

[0027] Use the estimated phase to synthesize the time domain sub-signal I p (L) :

[0028]

[0029] Using the quasi-maximum likelihood search strategy, we select p (L) To achieve the maximum L value:

[0030]

[0031] The value L new That is, the next signal length L of the p-th row of the sub-signal.

[0032] The present invention also discloses a three-phase distorted power grid sinusoidal signal filtering system based on sub-signal frequency estimation, comprising:

[0033] The first program module is used to intercept the sampled three-phase signal, fill it with zeros and write it into the sub-signal matrix;

[0034] The second program module is used for performing discrete Fourier transform on each row of the sub-signal matrix to construct a filter matrix;

[0035] A third program module is used for filtering the sub-signal matrix using a filter matrix;

[0036] The fourth program module is used to perform inverse discrete Fourier transform on the filtered sub-signal matrix to obtain a filtered result.

[0037] The present invention further discloses a computer-readable storage medium having a computer program stored thereon, characterized in that when the computer program is executed by a processor, the computer program executes the steps of the three-phase distorted power grid sinusoidal signal filtering method based on sub-signal frequency estimation as described above.

[0038] Compared with the prior art, the advantages of the present invention are:

[0039] The three-phase distorted power grid sinusoidal signal parallel filtering method based on sub-signal frequency estimation of the present invention belongs to frequency domain filtering. In the filter construction, the center frequency of the filter corresponds to the frequency component with the maximum amplitude of each row of the signal by performing a right circular shift operation on each row of the filter matrix, thereby filtering out interference more accurately. In addition, the three-phase signal is reconstructed into a matrix, and different filters are constructed to filter each phase of the three-phase signal. This is a parallel processing solution, and filtering requires less computing time. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The present invention is a flowchart of a method according to an embodiment. DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0042] like Figure 1 As shown, the three-phase distorted power grid sinusoidal signal filtering method based on sub-signal frequency estimation of the embodiment of the present invention includes the following steps: first, the sampled three-phase signal is intercepted, zero-filled and written into the sub-signal matrix; second, each row of the sub-signal matrix is ​​discrete Fourier transformed to construct a filter matrix; then, the sub-signal matrix is ​​filtered using the filter matrix; finally, the filtered sub-signal matrix is ​​discretely inverse transformed to obtain the filtered result. The specific process steps are as follows:

[0043] Step 1: Intercept the sampled three-phase signal. The length of each phase signal is L. Pad the end of the intercepted three-phase signal with zeros to increase the length to N. DFT , write the sub-signal matrix x(p,n), where p = 1, 2, 3, representing the three phases A, B, and C respectively, and n = 1, 2, 3, ..., N DFT ; N DFT is the first integer power of 2 greater than or equal to L; when N DFT = L, no zero padding is required; when L <N DFT When , the last bit of the sampled three-phase signal is padded with zero;

[0044] Step 2: Perform discrete Fourier transform on each row of the sub-signal matrix x(p,n) to obtain the complex spectrum matrix X D (p, k), k = 1, 2, 3, ..., N DFT , find X D The index number of the maximum modulus value in each row, denoted by i p , the subscript p represents the row number corresponding to the matrix;

[0045] Step 3: Construct a size of 3*N DFT The filter matrix F, where each row of F is a low-pass filter with a passband length of w, where the first w / 2 and last w / 2 elements of each row of F are 1, and the other intermediate elements are 0:

[0046]

[0047] Among them, ceil(w / 2) is the first integer greater than or equal to w / 2, and floor(w / 2) is the first integer less than or equal to w / 2;

[0048] Step 4: Circularly shift the pth row of F to the right by i p -1 element, defining the resulting matrix as F R , by shifting the passband of the p-th row filter to X D Near the maximum modulus value of the row;

[0049] Step 5: Apply filter F R Pair signal matrix X D Perform filtering;

[0050] X RD =X D ⊙F R (2)

[0051] Among them, ⊙ is the corresponding multiplication of matrix elements, X RD is the spectrum of the sub-signal matrix after filtering;

[0052] Step 6: XRD Each row is inversely discrete Fourier transformed to obtain the result matrix x RD (p,n);

[0053] Step 7: Place the x RD The 0s at the end of each row are removed to form a filter sub-signal matrix x of size 3*L F (p,l), where l = 1, 2, 3, ..., L, x F The pth row of is the filtering result x of the corresponding row signal f (p,l).

[0054] In a specific embodiment, in step 3, in order to prevent the signal from being excessively attenuated as the bandwidth decreases, the passband length w of the filter is taken as: w = L*i p / N DFT .

[0055] In a specific embodiment, after completing the filtering of the above steps 1 to 7, the length of each subsequent phase signal is L, and the quasi-maximum likelihood search strategy is used for adjustment. The specific process is:

[0056] Step S1, the filtering result x after completing steps 1 to 7 F Perform phase estimation on each row of (p,l) to obtain the phase estimation result φp of the pth row;

[0057] Step S2, using the estimated phase to synthesize the time domain sub-signal I p (L) :

[0058]

[0059] Step S3, using the quasi-maximum likelihood search strategy, select p (L) To achieve the maximum L value:

[0060]

[0061] The value L new That is, the next signal length L of the p-th row of the sub-signal.

[0062] The three-phase distorted power grid sinusoidal signal parallel filtering method based on sub-signal frequency estimation of the present invention belongs to frequency domain filtering. In the filter construction, the center frequency of the filter corresponds to the frequency component with the maximum amplitude of each row of the signal by performing a right circular shift operation on each row of the filter matrix, thereby filtering out interference more accurately. In addition, the three-phase signal is reconstructed into a matrix, and different filters are constructed to filter each phase of the three-phase signal. This is a parallel processing solution, and filtering requires less computing time.

[0063] The above method is further described below in conjunction with a specific embodiment:

[0064] Assume that the fundamental frequency of the three-phase signal is 50 Hz and the sampling rate is 2000 Hz.

[0065] Step 1: intercept the sampled three-phase signal, the length of each phase signal is L=40, and fill the intercepted three-phase signal with zeros at the end, and fill the length with 24 zeros to N DFT =64, write the sub-signal matrix x(p,n), where p=1, 2, 3 represent the three phases A, B, and C respectively, and n=1, 2, 3, ..., 64;

[0066] Step 2: Perform discrete Fourier transform on each row of the sub-signal matrix x(p,n) to obtain the complex spectrum matrix X D (p, k), k = 1, 2, 3, ..., 64, find X D The index number of the maximum modulus value in each row, denoted by i p =3, the subscript p represents the row number corresponding to the matrix;

[0067] Step 3: Construct a filter matrix F of size 3*64, where each row of F is a low-pass filter with a passband length of w, w = 1.5:

[0068]

[0069] Step 4: Circularly shift each row of F to the right by 2 elements and define the resulting matrix as F R , by shifting the passband of the p-th row filter to X D Near the maximum modulus value of the row;

[0070] Step 5: Apply filter F R Pair signal matrix X D Filtering

[0071] X RD =X D ⊙F R (6)

[0072] Among them, ⊙ is the corresponding multiplication of matrix elements, X RD is the spectrum of the sub-signal matrix after filtering;

[0073] Step 6: X RD Each row is inversely discrete Fourier transformed to obtain the result matrix x RD (p,n);

[0074] Step 7: Place the x RD The 0s at the end of each row are removed to form a filter sub-signal matrix x of size 3*40 F(p,l), where l = 1, 2, 3, ..., L, x F The pth row of is the corresponding row signal, that is, the filtering result corresponding to a certain phase in the three phases.

[0075] After completing the filtering from step 1 to step 7, the length of each subsequent phase signal is L, which can be adjusted using the quasi-maximum likelihood search strategy:

[0076] First, for x F Phase estimation is performed on each row of (p, l), and the phase estimation results of the p-th row are obtained as φ1=0, φ2=π / 3 and φ1=2π / 3;

[0077] Secondly, the obtained phase estimation result is used to synthesize the time domain sub-signal I p (L) :

[0078]

[0079] Then, using the quasi-maximum likelihood search strategy, we select p (L) To reach the maximum L value L new =36, the value of L new That is, the next signal length L of the p-th row of the sub-signal.

[0080] The embodiment of the present invention further discloses a three-phase distorted power grid sinusoidal signal filtering system based on sub-signal frequency estimation, comprising:

[0081] The first program module is used to intercept the sampled three-phase signal, fill it with zeros and write it into the sub-signal matrix;

[0082] The second program module is used for performing discrete Fourier transform on each row of the sub-signal matrix to construct a filter matrix;

[0083] A third program module is used for filtering the sub-signal matrix using a filter matrix;

[0084] The fourth program module is used to perform inverse discrete Fourier transform on the filtered sub-signal matrix to obtain a filtered result.

[0085] The filtering system of the present invention corresponds to the above filtering method and also has the advantages described in the above method.

[0086] The embodiment of the present invention further discloses a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the three-phase distorted power grid sinusoidal signal filtering method based on sub-signal frequency estimation as described above are performed. The embodiment of the present invention also discloses a computer device, including a memory and a processor, on which a computer program is stored, and when the computer program is executed by the processor, the steps of the three-phase distorted power grid sinusoidal signal filtering method based on sub-signal frequency estimation as described above are performed. The present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing related hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and when the computer program is executed by the processor, the steps of each of the above-mentioned method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form, etc. Computer readable media may include: any entity or device capable of carrying computer program code, recording media, USB flash drives, mobile hard disks, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signals, telecommunication signals, and software distribution media, etc. The memory may be used to store computer programs and / or modules, and the processor implements various functions by running or executing the computer programs and / or modules stored in the memory, and calling the data stored in the memory. The memory may include high-speed random access memory, and may also include non-volatile memory, such as a hard disk, memory, plug-in hard disk, smart memory card (Smart Media Card, SMC), secure digital (Secure Digital, SD) card, flash card (Flash Card), at least one disk storage device, flash memory device, or other volatile solid-state storage device, etc.

[0087] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A three-phase distorted power grid sinusoidal signal filtering method based on sub-signal frequency estimation, characterized in that: Includes steps: The sampled three-phase signal is intercepted, filled with zeros and written into the sub-signal matrix; Perform discrete Fourier transform on each row of the sub-signal matrix to construct a filter matrix; Filtering the sub-signal matrix using a filter matrix; Perform inverse discrete Fourier transform on the filtered sub-signal matrix to obtain the filtered result; The specific process of performing discrete Fourier transform on each row of the sub-signal matrix is ​​as follows: Perform discrete Fourier transform on each row of the sub-signal matrix x(p, n) to obtain the complex spectrum matrix X D (p, k), k = 1, 2, 3, ..., N DFT , find X D The index number of the maximum modulus value in each row, denoted by i p , the subscript p indicates the row number of the matrix; N DFT is the first integer power of 2 that is greater than or equal to L; L is the length of each phase signal; The specific process of constructing the filter matrix is ​​as follows: DFT The filter matrix F, where each row of F is a low-pass filter with a passband length of w, where the first w / 2 and last w / 2 elements of each row of F are 1, and the other intermediate elements are 0: Among them, ceil(w / 2) is the first integer greater than or equal to w / 2, and floor(w / 2) is the first integer less than or equal to w / 2; Circularly shift row p of F to the right by i p -1 element, defining the resulting matrix as F R , by shifting the passband of the p-th row filter to X D Near the maximum modulus value of this row.

2. The three-phase distorted power grid sinusoidal signal filtering method based on sub-signal frequency estimation according to claim 1 is characterized in that: The specific process of intercepting the sampled three-phase signal, filling it with zeros and writing it into the sub-signal matrix is ​​as follows: intercept the sampled three-phase signal, the length of each phase signal is L, and fill the end of the intercepted three-phase signal with zeros to fill the length to N DFT , write the sub-signal matrix x(p, n), where p=1, 2, 3, representing phases A, B, and C respectively; n=1, 2, 3, …, N DFT ; N DFT is the first integer power of 2 greater than or equal to L; when N DFT =L, no zero padding is required; when L< N DFT When the three-phase signal is sampled, the last bit is padded with zero.

3. The three-phase distorted power grid sinusoidal signal filtering method based on sub-signal frequency estimation according to claim 1 is characterized in that: The filter matrix F R Pair signal matrix X D Perform filtering; （2） in, is the corresponding multiplication of matrix elements, X RD is the spectrum of the sub-signal matrix after filtering.

4. The three-phase distorted power grid sinusoidal signal filtering method based on sub-signal frequency estimation according to claim 3 is characterized in that: The specific process of performing inverse discrete Fourier transform on the filtered sub-signal matrix to obtain the filtered result is: X RD Each row is inversely discrete Fourier transformed to obtain the result matrix x RD (p, n); x RD The 0s at the end of each row are removed to form a filter sub-signal matrix x of size 3*L F (p, l), where l=1, 2, 3, …, L, x F The pth row of is the filtering result x of the corresponding row signal f (p, l).

5. The three-phase distorted power grid sinusoidal signal filtering method based on sub-signal frequency estimation according to claim 4 is characterized in that: After the filtering result is obtained, the length of each subsequent phase signal is L, which is adjusted using the quasi-maximum likelihood search strategy.

6. The three-phase distorted power grid sinusoidal signal filtering method based on sub-signal frequency estimation according to claim 5, characterized in that: The specific process of adjustment using the quasi-maximum likelihood search strategy is: The filtering result x F Perform phase estimation on each row of (p, l) to obtain the phase estimation result φp of the p-th row; Use the estimated phase to synthesize the time domain sub-signal : (3) Using the quasi-maximum likelihood search strategy, we select To achieve the maximum L value: (4) The value L new That is, the next signal length L of the p-th row of the sub-signal.

7. A three-phase distorted power grid sinusoidal signal filtering system based on sub-signal frequency estimation, used to execute the steps of the three-phase distorted power grid sinusoidal signal filtering method based on sub-signal frequency estimation as claimed in any one of claims 1 to 6, characterized in that: include: The first program module is used to intercept the sampled three-phase signal, fill it with zeros and write it into the sub-signal matrix; The second program module is used for performing discrete Fourier transform on each row of the sub-signal matrix to construct a filter matrix; A third program module is used for filtering the sub-signal matrix using a filter matrix; The fourth program module is used to perform inverse discrete Fourier transform on the filtered sub-signal matrix to obtain a filtered result.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the computer program executes the steps of the three-phase distorted power grid sinusoidal signal filtering method based on sub-signal frequency estimation as claimed in any one of claims 1 to 6.

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