Wavelet-transform-based algorithm for harmonic analysis of power system waveforms

The paper develops an approach based on wavelet transform for the evaluation of harmonic contents of power system waveforms. The new algorithm can simultaneously identify all harmonics including integer, noninteger and subharmonics. In the first step of the approach, the frequency spectrum of the waveform is decomposed into subbands using discrete wavelet packet transform filter banks. In the second step, continuous wavelet transform is applied to nonzero subbands to evaluate the harmonic contents, In the first step, there is the problem of images due to down samplings and up samplings of the waveform, A method for alleviating this image problem is developed in the paper. Methods are developed to accurately quantify harmonics frequency amplitude and phase. The approach is validated by its application to synthesised waveforms and to power system waveforms measured in the Western Australia system. It is found to be powerful and suitable for practical use.