Power Quality Disturbances Identification Based on dq Conversion, Wavelet Transform and FFT

Based on the waveform characteristic of virtual value by dq conversion, Wavelet Analysis and FFT, seven types of power quality disturbances are layered-recognized. Firstly, according to the size of voltage virtual value, the disturbances will be divided into two types, the first type includes voltage sag, swell and interruption. The second type includes the rest of the disturbances. Secondly, wavelet analysis will be carried out to the second type, transient pulse and low frequency oscillation will be identified by the characteristic of high frequency coefficient and then they will be separated by the number of zero-crossing points. Finally, as far as the disturbances, which present similar distribution in high frequency coefficient, as the comparability, FFT can be used. We can identify them with spectrum characteristic. Simulation results show the effectiveness of the proposed method.