A Detection Method of Dense Harmonics/Inter-harmonics Based on Improved All-phase Time-shifting Method and ZoomFFT

Abstract

Aiming at the complex situation of intensive harmonics/inter-harmonics in power signals, this paper proposes an analysis method based on improved all phase time shift phase difference method and ZoomFFT. Firstly, the Hankel matrix of the input signal is constructed, and the TLS-ESPRIT algorithm is used to obtain the frequency components in the signal. The relationship between the peak spectral line and the frequency offset in the all phase time shift method is derived. The amplitude information of the input signal is calculated. The phase information of the input signal is obtained by analyzing the “phase invariant” characteristic of the all phase FFT spectrum. The frequency interval of adjacent frequencies is used to judge whether there is density. If there are intensive harmonics/inter-harmonics, TLS-ESPRIT method is used to calculate the center frequency of the dense spectrum and construct a complex analytic band-pass filter to improve the ZoomFFT method to extract the frequency and amplitude information of the signal at the dense spectrum; If there is no intensive harmonic/inter-harmonic, the improved all phase time shift method is used to extract the parameters of the input signal. Simulation results show that the proposed algorithm can effectively and accurately extract the frequency, amplitude and phase parameters of dense harmonics/inter-harmonics under the conditions of multiple dense spectrum, fluctuation of fundamental frequency and noise interference.