The VPF Harmonic Analysis Algorithm Based on Quasi-Synchronous DFT

Abstract

Background: The main source of spectral leakage in Quasi-synchronous DFT (QSDFT) harmonic analysis is the short-range leakage resulting from the fluctuating signals. Objective: The QSDFT discrete spectrum stretching theorem, as is demonstrated in this paper, shows that the peak in frequency domain changes synchronously with the signal frequency drift. Based on QSDFT, an improved algorithm—Variable Picket Fence (VPF) is proposed. Method: The VPF means the sampling position in the frequency domain will synchronously change with the signal frequency drift. In this way, we can accurately capture the spectrum peak, thereby inhibiting short-range spectral leakage. Hence signal frequency drift can be obtained by measuring the fundamental phase difference between the adjacent sample points. Results: Simulation and application results prove that this proposed algorithm increases the accuracy of harmonic analysis by inhibiting short-range spectral leakage efficiently in the range of 45 to 55HZ.