Harmonic Detection Method Based on Windowed Double-Spectrum Interpolation FFT

Windowing and interpolation algorithms are often used to improve the accuracy of FFT calculations due to the fact that asynchronous Fourier Transform (FFT) cannot accurately analyze harmonic parameters due to non-synchronous sampling and non-integral truncation. The windowed double-spectrum interpolation algorithm determines the position of the actual spectral line by analyzing the frequency domain expression of the signal after windowing, and uses the two maximum spectral line values near the true harmonic point to perform frequency, amplitude and Parameter estimation such as phase. Since the grid frequency will fluctuate, this paper also needs to consider the impact of fluctuations when designing the specific interpolation algorithm. Simulation experiments show that the windowed double-spectrum interpolation algorithm designed in this paper can effectively improve the accuracy of harmonic detection under grid fluctuations.