Improved off-nominal operation of phasor measurement units using discrete fourier transformation

This paper presented a novel phasor estimator having less computational complexity and would be suitable for implementation in a digital signal processor (DSP). A discrete fourier transformation (DFT) using a fixed window and variable sampling time had been used to calculate phasor and frequency of the signal. The adjustment of the sampling time with the system frequency ensured a minimum leakage effect and accurate DFT computation. The phasor and frequency estimation was made at discrete intervals determined by the internal clock, which was synchronized with the 1 pulse per second (PPS) clock from the Global Positioning System (GPS). The bias corrected Jacobsen method was utilized for calculating the system frequency and its efficiency was compared with other three point DFT based frequency estimators. The proposed architecture of the DFT based phasor measurement unit was tested with signal corrupted with noise and harmonics, step and ramp variation of frequency and finally the amplitude jump conditions. The simulation results illustrated that the proposed system was able to capture the phasor at both steady state and dynamic conditions of the signal. IEEE standard C37.118.1-2011 was used as the benchmark for evaluating the proposed Phasor measurement unit (PMU).