Traveling wave time-frequency analysis method based on variational mode decomposition and Wigner-ville distribution

Abstract

The invention discloses a traveling wave time-frequency analysis method based on variational mode decomposition and Wigner-ville distribution. The method includes the following steps that: fault traveling wave signals are detected, and Karebauer phase-mode transformation is performed on three-phase voltage traveling wave signals, so that a traveling wave aerial mode component is obtained; variational mode decomposition is performed on the traveling wave aerial mode component, so that K intrinsic mode components are generated; Wigner-Ville analysis is performed on each intrinsic mode component;and the Wigner-Ville distribution of each intrinsic mode component is linearly superimposed, so that the time-frequency domain distribution of original traveling wave aerial mode signals is obtained.With the method of the invention adopted, the interference of cross terms in Wigner-Ville distribution can be effectively suppressed; a good noise suppression effect enabling good VMD (Variational Mode Decomposition) is preserved; time-frequency resolution enabling high Wigner-Ville distribution and good time-frequency aggregation are preserved; traveling wave time-frequency domain information characteristics are truly and accurately represented; and fault traveling waves can be completely observed. The method is of important theoretical and practical significance for the practical application of fault traveling wave protection and positioning.

Description

technical field [0001] The present invention relates to the field of power systems, in particular to a traveling wave time-frequency analysis method based on variational mode decomposition (Variational ModeDecomposition, VMD) and Wigner-Ville Distribution (Wigner-Ville Distribution, WVD). Background technique [0002] With the continuous expansion of the scale of the power system, the load of the transmission line is increasing year by year, and the requirements of the power customers for the safe maintenance and operation of the power grid are getting higher and higher. How to quickly cut off the fault line and accurately find the location of the fault point has become an important guarantee for the safe and stable operation of the power system. [0003] Fault traveling wave has fast response speed and is not affected by distributed capacitance, system oscillation, transformer saturation and other factors, and has obvious technical advantages. Fault traveling wave protectio...

AI Technical Summary

Problems solved by technology

At present, fault traveling wave protection and location methods are mainly divided into the following two types: based on time domain information and based on frequency domain information; traveling wave protection and location methods based on time domain information need to accurately detect the amplitude and polarity of the initial traveling wave head and arrival time, and to correctly identify the nature of subsequent refraction and reflection waveforms, the sampling rate is high, especially in high-impedance ground faults or voltage zero-crossing faults, it is difficult to detect wave head information; traveling wave protection based on frequency domain information and The positioning method, according to the impedance characteristics of the line boundary, and according to the ratio of the local high-frequency and low-frequency bands of the traveling wave signal inside and outside the area, constitutes the protection criterion; this method only uses certain two frequency band signals in the traveling wave signal, and the fault information contained Insufficient, and when the fault location is far away from the detection point, the high-frequency signal attenuation is serious, which may make it difficult for the protection to correctly distinguish the fault at the end of the line from the fault at the opposite end of the bus

Existing traveling wave protection and positioning methods are only based on time domain information or certain two frequency band information in the frequency domain, resulting in low reliability of traveling wave protection and positioning. Traveling wave positioning method, the positioning error is relatively large in actual application, or even fails

[0004] The fault traveling wave is a wide-band signal, which includes high-frequency components and low-frequency components, especially the power frequency component. Fault traveling wave time-frequency domain panoramic information is integrated to realize protection and positioning based on traveling wave time-frequency domain panoramic information method, which is expected to solve the problems of low reliability and accuracy in existing methods

But so far, there is no complete time-frequency analysis method for traveling waves

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