A new family of measurement technique for tracking voltage phasor, local system frequency, harmonics and DC offset

A series of precise digital algorithms based on discrete Fourier transforms (DFT) to calculate the frequency and phasor in real-time are proposed. These algorithms, we called the smart discrete Fourier transforms (SDFT) family, succeeded in overcoming several problems of DFT, which include frequency deviation, harmonics and DC offset. Moreover, if using smoothing windows to filter noise, the SDFT family is not affected by phase shift and amplitude decay. Factional cycle computing is allowed. Also, the advantages of DFT can still be reserved in SDFT family. These make the SDFT family more accurate than conventional DFT. Besides, SDFT family is very easy to implement, so it is very suitable for use in power systems. We provide the general form of SDFT family and simulation results compared with conventional DFT method to verify the claimed benefits of SDFT family.