Research on Optimized Combined Cosine Windows with Maximum Side Lobe Decay for Harmonic Analysis

Because of all kinds of factors, it is very difficult to achieve coherent sampling and integrated-cycle truncation when power grid harmonics are analyzed. But there inevitably exists spectral leakage when Fourier transform is directly adopted in incoherent sampling mode, and the accuracy of harmonic analysis will be seriously affected. To reduce spectral leakage, it´s a very important measure to weight the sampling data with appropriate window, and combined cosine windows are a series of useful windows for power grid harmonic analysis. Its coefficients are worth of being optimized so as to more notably reduce spectral leakage. To aim at these things, this paper puts forward general principles to optimize combined cosine windows, and deduces the optimized combined cosine windows with maximum side lobe decay. In the incoherent sampling mode, these optimized windows can make side lobes decay with the maximum rate, so they can significantly reduce spectral leakage and can help to realize high-precision power grid harmonics measurement and analysis.