A fast and accurate method for estimating power systems phasors using DFT with interpolation

The paper develops a method based on waveform interpolation in the discrete time-domain to counter the spectral leakage errors arising in forming, by discrete Fourier transform (DFT), the supply frequency phasors representing power system voltages and currents when there are system frequency deviations from the nominal value. The interpolation scheme allows DFT evaluation to be performed with a time window length which is exactly equal to the fundamental period of the voltage or current waveform. The applications of the method developed include numerical protection where supply frequency phasors are required and synchronized phasor measurements for control functions in power systems. Comparative studies presented in the paper confirm the improvements achieved by the method proposed over other previously-published techniques in terms of accuracy and computing time