Power System Harmonic Analysis Based on Hilbert-Huang Transform

To analyze harmonic accurately is significant to the stability of power system.HHT(Hilbert-Huang Transform) is adopted to analyze harmonic in order to overcome the shortcoming of FFT method and wavelet analysis method.The power quality signals are decomposed by empirical mode decomposition(EMD) method,and then a series of intrinsic mode function(IMF) are obtained.Owing to different IMFs correspond to different harmonic,all harmonic’ amplitudes,frequencies and phases can be achieved via Hilbert transform(HT) plus Least Square fitting,to realize accurate analysis of power system harmonic.During the procession of EMD,piecewise Cubic Hermite Interpolating Polynomial is employed.Furthermore,in order to alleviate edge effects the method of adding extremes is used.Simulation indicates that Hermite interpolation is superior to the cubic spline interpolation in harmonic analysis.The method has high precise and is satisfied to analysis power system harmonic.