Harmonic Detection Algorithm Based on Four-spectrum-line Interpolation of Nuttall Dual-window All-phase FFT

When using conventional Fourier transform for harmonic analysis, problems such as spectrum leakage and fence effect may occur, which affect the accuracy of harmonic detection. This work proposed a harmonic detection algorithm based on Nuttall dual-window all-phase FFT four-spectrum-line interpolation. The Nuttall dual window in this algorithm has better main lobe and side lobe characteristics. Four adjacent spectral lines at the peak frequency point are selected to derive the correction formula of the typical window function through polynomial fitting, achieving interpolation correction of frequency and amplitude. Moreover, by utilizing the phase invariance of apFFT, the phase value of the main spectrum line can be directly taken as the initial phase of the signal without further correction. The research results indicate that compared with other algorithms, the proposed algorithm can effectively reduce the detection error of complex harmonic and interharmonic signal parameters, and suppress the interference of frequency fluctuations and white noise on harmonic detection.