AN IMPROVED ALGORITHM FOR HARMONIC ANALYSIS OF POWER SYSTEM USING FFT TECHNIQUE
PANG Hao, LI Dong-xia, ZU Yun-xiao, WANG Zan-ji (Department of Electrical Engineering, Tsinghua University, Beijing 100084, China)
There are difficulties in performing synch-ronized sampling and integral period truncation in the harmonic analysis of power system with the fast Fourier transform (FFT) technique. However, not to satisfy these conditions, the results will be disturbed by the frequency leakage. Some efforts have been made including the utilization of window functions and interpolation algorithms to correct the measured frequency, phase and amplitude by FFT. In order to overcome some shortcomings of existing correction methods, an improved algorithm is present in this paper, with which the amplitudes of harmonics can be estimated from the two neighboring spectral lines. The polynomial approximation method is also employed to obtain simple formulas for frequency and amplitude correction. By these methods, the disturbance of the frequency leakage and the noise can be reduced and the accuracy of the harmonic analysis can be improved. Based on the proposed algorithm, the practical correction formulas for some typical window functions are developed. The simulation results have verified the effectiveness and practicability of the algorithm.
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