Abstract:

In order to further improve the sensitivity and reliability of short-circuit fault detection in low voltage DC microgrids,a short-circuit fault early detection method based on voltage and current multi-scale wavelet transform is proposed.Based on the least squares front filtering,fully considering the voltage and current short-circuit fault singularity, the fourth layer wavelet decomposition detail components are used to construct the short-circuit fault early detection criterion.The experimental results show that the proposed detection method is insensitive to the transition resistance. The short-circuit faults can be quickly detected within 0.5 ms when the transition resistance is small.The short-circuit faults can be reliably detected within 0.6 ms when the transition resistance is large.At the same time,it can effectively avoid the influence of disturbing conditions such as frequent load switching, and has better sensitivity and reliability.

Key words: low voltage DC microgrid, short-circuit fault, early detection, wavelet transform, least squares fitting