Spectral estimation technique for nonstationary signals of power systems

In this paper a method for estimating the spectral content of frequency modulated waveforms is presented. The method is intended to estimate harmonics and interharmonics of power line signals where, as known, the frequency of the fundamental component (50 Hz or 60 Hz) slightly changes over time. It is based on the non-uniform resampling of the harmonic functions that are usually used in the DFT as a base to analyze signals. The non-uniform sample period is provided by an instantaneous phase detector.