A simple time-domain algorithm for synchrophasor, frequency and ROCOF estimation

The proliferation of distributed energy resources and lug-in electric vehicles is expected to change present distribution systems, thus stressing the role of measurement instrumentation enabling safe and flexible smart grid operation. In this context, Phasor Measurement Units (PMUs) are required to measure amplitude, phase, frequency and rate of change of frequency (ROCOF) of AC waveforms not only in steady state, but also, and above all, under dynamic conditions, while still ensuring extremely low measurement uncertainty and high reporting rates. In this paper a lightweight signal processing algorithm based on the so-called Teager's energy operator is adopted to measure amplitude, phase, frequency and ROCOF of AC waveforms in some of the testing conditions prescribed by the IEEE Standard C37.118.1-2011 and the IEEE Amendment C37.11S.1a-2014. The reported analysis shows that the Teager's algorithm can provide high-rate and reasonably accurate measurement results under dynamic conditions. However, due to its sensitivity to wideband and narrowband disturbances, a preliminary band-pass filter is needed. In addition, instantaneous frequency and, above all, ROCOF estimates should be averaged to remove the residual effect of disturbances and to meet the limits reported in the IEEE Standards.