Multilayer DFT Interpolation Correction Approach for Power System Harmonic Analysis

Discrete Fourier transformer is the most basic mathematical tool for spectrum analysis of a stable electrical signal,which is also the transformation approach recommended by International Electro-technical Commission for harmonic and interharmonic measurement.However,when the analysis window width does not correspond to the actual signal period,spectral interferences among different tones would take place by using the above method,thus making the analysis accuracy deteriorated.To address this problem,this paper proposed a multilayer interpolation correction approach based on cosine windows for power system harmonic analysis.This method uses the phase features of the spectral bins after rotation adjustment to make the interferences on the concerned tone,caused by the unconcerned tones,minimum through multilayer summation.It can further restrain the spectral interferences among different tones on the basis of windowing.The simulation case study shows that the proposed approach can achieve high-accuracy harmonic measurement even when the sampling does not exactly fit the integral signal period.It improves the traditional windowed interpolation approach from another point of view.