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FFT Power Harmonic Detection Method Based on Two-way Interpolation and Synchronized Sampling Sequence

A sampling sequence and two-way interpolation technology, applied in the direction of measuring devices, measuring electrical variables, instruments, etc., can solve the problems of affecting timeliness, interference in detection, and inability to suppress spectrum leakage, so as to improve computing efficiency, facilitate engineering implementation, reduce Effect of Small Spectral Leakage

Active Publication Date: 2018-01-23
WUHAN UNIV
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Problems solved by technology

[0004] However, although fast Fourier analysis after windowing can effectively reduce spectrum leakage, due to the large number of side lobes in the frequency domain of the window function, the spectrum leakage cannot be well suppressed, and the side lobes with large amplitude-frequency response The lobes interfere with the detection of weaker frequency components in the original signal
However, the window function with excellent side lobe characteristics has the disadvantages of complex interpolation correction formula and long time-consuming process of spectral line detection, which seriously affects the timeliness.

Method used

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  • FFT Power Harmonic Detection Method Based on Two-way Interpolation and Synchronized Sampling Sequence
  • FFT Power Harmonic Detection Method Based on Two-way Interpolation and Synchronized Sampling Sequence
  • FFT Power Harmonic Detection Method Based on Two-way Interpolation and Synchronized Sampling Sequence

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Embodiment

[0065] Select the voltage signal x(t) containing higher harmonics, and use the voltage signal as an example to illustrate the method of the present invention.

[0066] Step 1, fixed sampling frequency f 0 =25600Hz sampling harmonic signal x(t) to obtain discretized signal x(n).

[0067] Step 2, filter the signal x(n), specifically: pass the signal x(n) through a second-order Butterworth low-pass filter with a cutoff frequency of 75Hz to obtain the fundamental signal x 0 (n).

[0068] Step 3, set the threshold a=0, and detect the fundamental signal x 0 (n) In the case of zero crossing, the fundamental wave signals of ten consecutive cycles under the current power grid fundamental frequency are obtained, that is, the sampling data, and the length of the sampling data is denoted as N.

[0069] Step 4, perform forward Newton interpolation on the sampled data.

[0070] The whole cycle processing is performed on the first and last ends of the sampled data, specifically: for the ...

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Abstract

The invention discloses an FFT power harmonic detection method for a bidirectional interpolation synchronization sampling sequence, comprising: step 1, a mutual inductor samples a harmonic signal, a discrete signal x(n) is obtained, and the signal x(n) is subjected to filtering processing to acquire a fundamental wave signal x0(n); step 2, fundamental wave signals of ten continuous cyclic waves are taken as sampling data; step 3, the sampling data are subjected to forward Newton interpolation, and moment positions when an amplitude value of the sampling data exceeds a threshold value a for the first time and the twenty first time are acquired, and respectively marked as tstart and tend; step 4, by taking equal diversion points between the moment positions tstart and tend as interpolation points, the sampling data are subjected to reversed Newton interpolation, thus acquiring signal amplitude values of the various interpolation points, namely acquiring the synchronization sampling sequence; step 5, the synchronization sequence is subjected to fast Fourier transform. The FFT power harmonic detection method can be used for quickly and accurately detecting signal harmonic components and continuously detecting the detected signals for a long term, and has good timeliness.

Description

technical field [0001] The invention relates to the technical field of harmonic detection in electric power systems, in particular to an FFT electric harmonic detection method of bidirectional interpolation and synchronous sampling sequences. Background technique [0002] The large increase of nonlinear loads in the power system, especially the wide application of power electronic devices, increases the harmonic components in the power grid and seriously deteriorates the power quality. The occurrence of harmonics in the distribution network may not only cause resonance in the power grid, but also increase the loss of the motor and transformer, aggravate the aging of the power cable, and shorten the life of the power cable. The rapid and accurate detection of harmonic components will be beneficial to the analysis and treatment of power quality. Fast Fourier transform has become the most important method of power grid harmonic analysis because of its mature theory and easy em...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R23/167
CPCG01R23/167
Inventor 陈文娟刘开培谭甜源熊纽
Owner WUHAN UNIV
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