Frequency estimation of three-phase power systems using complex adaptive notch filters

This paper presents a new technique for adaptive estimation of the frequency of unbalanced three-phase power systems using complex coefficient first-order notch filters. The input complex sinusoid is given by a sum of sequences with positive and negative frequencies. Analytical expressions of mean square error due to an oscillating error introduced by the sequence with negative frequency and input noise have been derived. Closed form expression for frequency tracking error has been also derived. Computer simulation results are presented to validate the analysis.