A Precise Calculation of Power System Frequency

A precise digital algorithm based on discrete Fourier transforms (DFT) to estimate the frequency of a sinusoid with harmonics in real time is proposed. This algorithm, which we call the smart discrete Fourier transform (SDFT), smartly avoids the errors that arise when frequency deviates from the nominal frequency, and keeps all the advantages of the DFT (e.g., immune to harmonics and the recursive computing can be used in SDFT). These make the SDFT more accurate than conventional DFT-based techniques. In addition, this method is recursive and easy to implement, so it is suitable for use in real time. We provide the simulation results compared with a conventional DFT method and second-order Prony method to validate the claimed benefits of SDFT.