Study on applying wavelet transform to the protection algorithm of microgrid dominated by inverter -interfaced DGs

The fault characteristics of the microgrid, dominated by the inverter interfaced DGs,are quite different from that of traditional power grid. It has the properties such as small fault current, non-integer harmonics, frequency fluctuations. Currently, the most widely used algorithm is Fourier algorithm, which uses the fixed-length data window and has unsatisfactory filtering effect on non-integer harmonics or non-stationary signals. This paper introduces the wavelet analysis into the filter algorithm, by constructing a suitable wavelet function to obtain the required filtering effect. It proposes a construction formula based on the Chaari complex wavelet, selects the corresponding mother wavelet, and shows the effectiveness of filtering by simulation.