Harmonic Analyzer Based On Improved Wavelet Packet Algorithm

Power harmonic distortion of the pollution problem is serious, harmonic pollution has become the power quality. Therefore, to monitoring and researching harmonic is not only a premise to limit and eliminate harmonic, but also an important factor of protecting the power supply system, equipment operation and personal safety. Currently, the methods of harmonic analysis include fast Fourier transform and wavelet transform. Fast Fourier transform is the basis of harmonic analysis, wavelet transform has good time-frequency feature applicated widely in recent years.This paper introduces the concept of harmonic, characteristics of harmonic, and classical harmonic analysis methods. Based on wavelet and wavelet packet theory, the improved wavelet packet algorithm was applied to harmonic analysis. In the algorithm, fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) were used to process the sub-band signals, which passed each wavelet filter. According to the rule of frequency division , the low half frequency band or the high half frequency band, whose spectrum value were denoted zero, and the filter group were adjusted to cause the band in sequence to avoid the staggered band phenomenon. Analysis and simulations were given showing the selection of wavelet basis function, and proved that the improved wavelet packet transform could eliminate the frequency of confusion phenomenonwhich exited in the traditional wavelet packet transform, effectively raising the harmonic analysis of the accuracy and reliability.In this paper, the software design of virtual harmonic analysis system was completed by means of LabVIEW, is based on improved wavelet packet transform, includes landing module, basic measurement module, harmonic analysis module and data communication module.They were accomplished by applying LabVIEW and MATLAB. The simulation results proved the exactness of the method.