The Harmonic Detection In Power Grid Based On Fourier And Wavelet Transform

Through the establishment of the harmonic signal model, The Harmonic detection method based on combining Fourier transform and Wavelet transform、 Fourier transform、Wavelet transform、Wavelet threshold denoising is using to analysis the model. The simulation results are described bellow.The amplitudes and frequency of harmonics can be obtain from the two neighboring spectral lines in the Fourier transform bimodal spectral correction algorithm which use weighted average of two lines to correct the amplitude.In Wavelet transform, The signal is divided into high frequency and low frequency by low-pass filter and high-pass filter. Through multiple decomposition, All the the time domain and frequency domain approximate information of harmonics can be obtain.In Harmonic detection method based on combining Fourier transform and Wavelet transform, the reconstructed steady-state component and damping component can be obtain by Wavelet transform, then by using Fourier transform bimodal spectral correction algorithm to analyze the signal of which has steady-state component to extract the harmonic amplitude and frequency.In Harmonic detection method based on combining Wavelet denoising and Fourier transform, the noises of signals can be reduced by Wavelet threshold denoising, then by using Fourier transform bimodal spectral correction algorithm to analyze the signal of which has been reduced noises to extract the harmonic amplitude and frequency.The results show that the Fourier transform can reflect the signal in the frequency domain information, and time-frequency localization characteristics of Wavelet transform can extract the signal time frequency characteristics at the same time. It has very good ability to analyze the mutation point of signal and reduce the noise in the signal. The Combination of these two algorithms. First, the mutation point of signal can be detected and the noise of signal can be reduced by Wavelet transform, then by using Fourier transform to analyze the steady-state signal to extract the harmonic amplitude and frequency.