Abstract
Aiming at the fault line selection problem in the single-phase grounding system of the distribution network, a new fault line selection method based on VMD and permutation entropy feature extraction combined with K-means clustering algorithm is proposed. This method is a hybrid algorithm that can effectively identify fault line selection. Firstly, a simulation model is built and its zero sequence current is collected. The variational modal decomposition method is used to decompose the collected zero-sequence current into multiple intrinsic modal functions, which can not only effectively reduce the influence of harmonic components and noise in the characteristic signal but also facilitate the calculation. The extracted intrinsic mode function is calculated by permutation entropy (PE), and the calculated entropy value is constructed into a matrix to highlight the fault characteristics of the line; then, the matrix is subjected to K-means cluster analysis through the preprocessing algorithm and the faulty line is correctly distinguished. Then, regression verification is performed. Finally, it is verified by the recorded wave data of the real test site and then analyzed and compared with other algorithms. The proposed method shows that when a single-phase ground fault occurs, the ground fault line selection can be effectively identified under different transition resistances, grounding resistances, and fault distances. Therefore, this method can accurately identify the fault line selection, and the accuracy rate is 100%, which has a certain use value.
Highlights
Algorithm PrincipleIn order to determine the appropriate decomposition modal value K in Variational Mode Decomposition (VMD), according to the description in [38], this paper constructs a fault signal containing high and intermediate frequency components and noise as an example for analysis
Introduction e power system constructed inChina is mainly based on ungrounded and grounded arc suppression coils, which are called small current grounding [1, 2]
According to the above research description, this paper proposes a method of line selection by combining Variational Mode Decomposition (VMD)-permutation entropy (PE) and K-means clustering algorithm when a single-phase grounding fault occurs in a neutral point grounding system with a small resistance. e main contributions of this paper are as follows: (1) A new hybrid algorithm is proposed. is method avoids modal mixing caused by harmonics and interference caused by noise, improves the characteristic accuracy of the signal, and can better identify fault lines under different transition resistances, grounding resistances, and fault distances. (2) is method can accurately identify fault line selection, classify the extracted fault characteristic signals, and perform regression verification, with an accuracy rate of 100%, which has a certain use value
Summary
In order to determine the appropriate decomposition modal value K in VMD, according to the description in [38], this paper constructs a fault signal containing high and intermediate frequency components and noise as an example for analysis. Reference [40] introduced that the selection of delay time has little effect on the value of permutation entropy, but when it is greater than 5, it is difficult to extract small changes in the fault signal; usually 1 can be used. At this time, an AM/FM signal (formula (12)) is randomly selected for permutation entropy calculation, and the N value is selected and discussed. (3) Continue to update calculation (16) until convergence, and get a new cluster center point
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