Research On The Methods Of Wavelet Transform Of The Power System Harmonic Detection

With the development of modern industry,all kinds of power electronic devices have been widely used,the power system is also having a significant increase in non-linear loads,making the power system harmonic pollution more and more serious.It has so serious deterioration of power quality,endangering the power system security,and impacting the user's normal work.So the harmonic problem became the focus of study.At the same time,Harmonic measurement is an important branch of the problem.It is the basis and also the starting point of the harmonic research,so the power system harmonic measurement is of great significance. Presently the main method to harmonics measure is the Fourier transforms and the wavelet transforms.Fourier transforms is the basic of modern harmonics measure; Wavelet transforms is the new method which has being researched nowadays.With this new method,the local characters of signals can be analyzed exactly,transient signals can be analyzed correctly,and the real-time and precision of harmonics measure can be improved too.This paper introduces the basic concept of harmonic,harmonic source and harmonic hazards,the methods of harmonic suppression,analyzed and reviewed the traditional power system harmonic measurement methods,discussed the transforms of wavelet theory such as continuous wavelet transform,discrete wavelet transform and wavelet packet transform and so on.In the analysis based on wavelet theory, from the perspective of signal analysis by Fourier transform and describes the wavelet transform in time-frequency analysis of the advantages of wavelet transform,we confirm that wavelet transform will be applied to the harmonic detection of this paper. Finally,simulation analysis show that the selections of wavelet functions and the wavelet function used in the selection of scale are of great importance of harmonic detection.Through simulation experiments,as compared with wavelet transform and FFT transform and wavelet transform analysis of mutations in the signal processing simulation results,we confirmed that wavelet transform can bring a more exact analysis of the local characteristics of signals,the transient signal can be analyzed correctly,so as the real-time and precision of harmonic measurement can be improved too.Finally,the use of wavelet packet decomposition coefficient reconstruction algorithm illustrated its valuable application in harmonic detection.