Power system harmonic analysis based on improved 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, Improved Extremum field Mean Mode Decomposition (IEMMD) and the piecewise Sinusoidal Interpolating are employed to reduce the end effect. In this way, only one Sine Interpolating is required rather than two. HHT not only can get accurate harmonic component and time characteristic, but also have very strong adaptability and practicability to analyze real-time temporary signal.