Application of constructed complex wavelet in power quality disturbances detection

The traditional real wavelet transform can not provide signal phase information, so there is a big limitation in transient power quality disturbances detection. Based on the orthogonal and compact support set db4 real wavelet, corresponding complex wavelet is constructed in this paper. The detailed solving process of high-pass and low pass filter coefficients is given. Analyzing the phase characteristics of complex wavelet transform, the practical criteria for disturbances detection by using constructed db4 complex wavelet are put forward. For three typical disturbances signal, i.e. pulse interferences, voltage sag, oscillatory transient, MATLAB simulation experiments are carried out. Results show that when traditional real wavelet can not discover disturbances, the method proposed in this paper is still valid and detection accuracy is independent of the size of disturbances.