Research Of Wavelet Analysis Application In Power System Harmonic Detection

Power is a sort of important energy sources,it is widely used in many fields of industry, agriculture and national defence.With the broad application of electric power and electron equipment,their non-linear,impulsive and unbalanced quality lead to pollution of power grid by harmonics increasingly serious.Harmonic has already become a serious public disaster to affect the power quality,in order to improve power quality,It is very important to measure harmonics effectively.Harmonic detection is the important part of harmonic issue and harmonic detection method is the key of harmonic measurement.This paper primarily studies the harmonic detection methods.Conventional Fourier transform can't localize in time-frequency field simultaneous. Wavelet Analysis is an useful time-frequency analysis method after Fourier transform because it has time-frequency localization and multi-resolution analysis ability.This article first introduces the concept of harmonic,harmonic mechanism of production, hazard of harmonic,harmonic source and deficiency of traditional harmonic detection method. Then compares harmonics detection at present then discusses wavelet transform mainly discusses several transform methods,such as continuous wavelet transform,discrete wavelet transform and wavelet packet transform of which characteristics are analyzed and contrast and analyses Wavelet Analysis and Fourier transform different time-frequency property and area of application.This article introduces application of Wavelet Analysis in harmonics detection from two points.The one part shows that wavelet transform can detect steady harmonic of power system instead of Fourier transform.The other part includes according difference of noise and singular points to extract singular points in noising signals.It uses the conventional soft and hard threshold wavelet de-noising method.Then introduces its application.Against the exiting questions about measurement of changing harmonic,it uses a method on the merits of wavelet transform combining with Fourier transform to detect them.It also figures out that this complex method has validity with lots of simulation.