Research On The Detection And Denoising Of Interharmonics Based On Wavelet Analysis

With the widely using of non-linear loads,the problems of harmonics have become more complicated in power system.Interharmonic is a special kind of harmonic which is non-integer of the fundamental frequency.A mass of the interharmonics that existed may make the power quality worse,resulting in flicker and the wrong running of relay.Recently,the harms of interharmonics have been attracted extensive attention.It's important to detect and analyze them accurately.The paper described the main resources and harms of interharmonics.The shortcomings of Fourier Transform adopted in their detections was analysed and the Wavelet method was selected for interharmonics.The Wavelet Transform was inherited and developed from the Fourier Transform,it has good time-frequency features and mutli-resolutions,and has been widely used in the measurement of interharmonics.For the case of the interharmonics with Guass white-noise,a new improved wavelet threshold function was proposed for signal denoising;For the non-ideal compactly supported property of the wavelet function,the continuous wavelet transform(CWT) which is used in the detections has some limitations,while the wavelet packet transform(WPT) has more detail partitions which could split the frequency into the non-zero band.Combined with the merits of both methods,an improved method was adopted to measure the parameters of interharmonics.The results simulated by Matlab reveals that the measurements and the analysis of interharmonics based on wavelet method are valid.Wavelet analysis can be used for signal-denoising and detect frequency accurately,therefore it has supplied an effective solution for the measurement of interharmonics.