A method of Dynamic Resampling for DFT-based harmonic analysis under time-varying frequency conditions

This paper presents a resampling method based on time-domain interpolation with applications in harmonic analysis in the time-varying frequency scenario. The method dynamically determines the resampling moments of a given signal that was originally sampled at a fixed rate. This process is based on real-time frequency tracking (fundamental component) by means of a PLL (Phase-Locked Loop) structure. Then, the values of the signal in the resampling moments are approximated by piecewise polynomials interpolation functions (Splines). This process is performed in an iterative way, so that a period of the resampled signal always contains the same integer number N of samples. The performance of the method for real-time harmonics tracking in common situations of asynchronous sampling is evaluated by applying the DFT (Discrete Fourier Transform) in the resampled signal using sliding windows. The simulation results show that the use of the method can effectively reduce the energy spreading effect (leakage) caused by asynchronous sampling and improve the estimates accuracy of the analyzed signal harmonics components significantly.