Microgrid high-resistance fault detection method

Abstract

The invention relates to a micro-grid high-resistance fault detection method, which is specifically implemented according to the following steps of: obtaining three-phase current on each bus of a micro-grid, and constructing comprehensive current through d-q conversion and a difference principle; extracting the highest frequency component of the comprehensive current by using a normalization method and empirical wavelet transform; constructing a mutation variance value according to the maximum value and the minimum value of the highest frequency component, and judging whether the microgrid isin a normal operation state, a disturbance state or a strong fault state in the disturbance state according to the mutation variance value; and obtaining an abrupt change weighted value through the number of sampling points and the normalization energy of the highest frequency component, and further distinguishing a normal disturbance state and a high-resistance fault state in the disturbance state through different values of the abrupt change weighted value. According to the method, dq transformation and empirical wavelet transformation are combined, fault characteristic components are increased, fault components are extracted by means of the adaptive spectrum division capability of empirical wavelet transformation, and micro-grid high-resistance detection is effectively realized by proposing variance of abrupt variables and weighted values of abrupt variables.

Description

technical field [0001] The invention belongs to the technical field of micro-grid fault detection, and in particular relates to a high-impedance fault detection method for a micro-grid. Background technique [0002] In response to energy crisis and environmental problems, micro-grid technology that can effectively accommodate new energy access has received extensive attention. Microgrid is a small distribution network system, which is composed of distributed generation (distributed generation, DG), power electronic equipment and power load and other equipment. Because the microgrid is mainly connected through the inverter DG, its fault current is much smaller than that of the traditional distribution network, and its flexible operation mode makes the traditional protection method unable to be directly applied to the microgrid. [0003] On the other hand, as a part of the power distribution system, the microgrid is located in a complex environment, and the lines are easy to ...

AI Technical Summary

Problems solved by technology

Since the high-impedance ground fault current signal is a non-stationary signal, the frequency component of the current changes with time, and the short-time Fourier transform cannot achieve the optimal signal time and frequency resolution at the same time.

Existing methods such as S transform, wavelet transform, and wavelet packet transform have fixed basis functions during feature extraction, which leads to insufficient representation ability of feature extraction, and the extraction is not self-adaptive. Although the empirical mode decomposition algorithm is self-adaptive , but prone to mode aliasing and endpoint effects, resulting in unclear physical meaning of some intrinsic mode functions

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