Study on application of morlet complex wavelet in digital protective relays

To overcome the disadvantages of full-wave Fourier algorithm that can not filter decaying DC component and has bad frequency characteristic, Morlet complex wavelet amplitude algorithm is studied. After analyzing the influence of parameters m, c and N to Morlet complex wavelet amplitude algorithm and the question that one-circle Morlet complex wavelet amplitude algorithm can not filter the two times harmonic component, difference filter adding one-circle Morlet complex wavelet amplitude algorithm is presented. The performance of full-wave Fourier algorithm, difference filter adding one-circle Morlet complex wavelet amplitude algorithm and three-circle Morlet complex wavelet amplitude algorithm are compared by simulation. The results of simulation indicate that Morlet complex wavelet amplitude algorithm can filter decaying DC component, has better frequency characteristic and higher calculating precision. It can acquire more precise results than the full-wave Fourier algorithm.