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Power grid harmonic detection method and device based on wavelet packet transformation and STFT fusion

A technology of wavelet packet transformation and harmonic detection, which is applied in the directions of instruments, character and pattern recognition, spectral analysis/Fourier analysis, etc., can solve the problems of poor robustness, wavelet filter aliasing, low precision, etc., and achieve improved The effect of precision

Inactive Publication Date: 2021-02-12
YANGTZE UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Although the wavelet packet algorithm solves the problem of time-frequency domain analysis and high-frequency resolution, wavelet filters almost always have aliasing phenomenon in signal analysis, resulting in low precision and poor robustness.

Method used

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  • Power grid harmonic detection method and device based on wavelet packet transformation and STFT fusion
  • Power grid harmonic detection method and device based on wavelet packet transformation and STFT fusion
  • Power grid harmonic detection method and device based on wavelet packet transformation and STFT fusion

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Experimental program
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Effect test

Embodiment 1

[0091] In this embodiment, the method of combining wavelet packet transform and short-time Fourier transform (STFT) is used to analyze and study the harmonics of the power grid. For a stable operating system, the STFT transform is used to analyze the amplitude, frequency and phase of the harmonics existing in the system. information to analyze. When a transient nonlinear disturbance occurs in the system, the time-domain properties of the transient disturbance are analyzed by combining wavelet packet transform and STFT transform, and information such as the amplitude, frequency change and phase offset of the disturbance signal is obtained at the same time .

[0092] 1. Power grid harmonic detection during steady state operation

[0093] Let the harmonic signal when the system is running stably be:

[0094]

[0095] In the formula, ω=2πf, f=50Hz.

[0096] Let n=5, the amplitudes of each harmonic are A1=1, A2=0.2, A3=0.3, A4=0.5, A5=0.3, and the phases are θ1=-π / 3, θ2=π / 6, ...

Embodiment 2

[0111] An embodiment of the present invention provides a power grid harmonic detection device based on the fusion of wavelet packet transform and STFT, including:

[0112] The STFT module is used to perform short-time Fourier transform on the time-varying harmonic signal of the power grid, obtain the spectrum diagram of the harmonic signal, and obtain the frequency information of the harmonic signal;

[0113] The number of decomposition layers determination module is used to determine the number of decomposition layers during wavelet packet decomposition and filtering according to the frequency information of the harmonic signal;

[0114] The wavelet packet transformation module is used to perform wavelet packet decomposition and filtering on the harmonic signal according to the number of decomposition layers, and decompose in sequence from low to high frequency bands to obtain wavelet packet coefficients corresponding to multiple frequency bands.

[0115] When the device perf...

Embodiment 3

[0117] An embodiment of the present invention provides an electronic device, including:

[0118] memory for storing computer software programs;

[0119] The processor is configured to read and execute the computer software program stored in the memory, and implement the grid harmonic detection method based on the fusion of wavelet packet transform and STFT described in Embodiment 1 of the present invention.

[0120] It should also be noted that when the logical instructions in the computer software program can be implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the embodiment of the present invention is essentially or the part that contributes to the prior art or the part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium , includi...

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Abstract

The invention relates to a power grid harmonic detection method and device based on wavelet packet transformation and STFT fusion. The method comprises the steps: firstly carrying out short-time Fourier transformation on a time-varying harmonic signal of a power grid, obtaining a spectrogram of the harmonic signal, and obtaining the frequency information of the harmonic signal; determining the number of decomposition layers during wavelet packet decomposition filtering according to the frequency information of the harmonic signal; and performing wavelet packet decomposition filtering on the harmonic signals according to the decomposition layer number, and obtaining wavelet packet coefficients corresponding to the multiple frequency bands through decomposition in sequence according to the frequency bands from low to high. Wavelet packet transformation can accurately analyze the time-frequency characteristics of the high-frequency disturbance signal and the low-frequency disturbance signal, and makes up for the deficiency of wavelet multi-resolution analysis in high-frequency signal time-frequency analysis. STFT transformation and wavelet packet transformation can achieve advantage complementation in the time-frequency analysis process, and thus the accuracy of power grid harmonic signal detection is greatly improved.

Description

technical field [0001] The invention relates to the technical field of power grid harmonic control, in particular to a power grid harmonic detection method and device based on the fusion of wavelet packet transform and STFT. Background technique [0002] As the power grid system becomes more and more complex, the increasingly open distributed power grid-connected strategy and the use of diverse non-linear devices have brought a series of problems to the stability of the power grid. Harmonics are one of the typical power quality problems. The existence of harmonics may not only cause the devices connected to the power grid to fail to work normally, but also seriously affect the quality of electric energy, causing huge economic losses to power companies and society. Accurate detection of harmonics can not only reduce the error of electric energy measurement, but also provide accurate reference data for harmonic control, so as to study targeted control programs to deal with th...

Claims

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Application Information

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IPC IPC(8): G01R23/16G06K9/00
CPCG01R23/16G06F2218/06
Inventor 张健宋文广
Owner YANGTZE UNIVERSITY
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