Estimation of power system frequency using adaptive notch filters

A new approach for frequency relaying in power system is presented in this paper. The approach consists of passing the power system voltage signal through a two stage adaptive notch filter, which produces an estimate of the fundamental frequency of the voltage waveform and its enhanced amplitude. The adaptive of the notch filter coefficients are obtained by a recursive least mean squares algorithm. The performance of the proposed algorithm is computationally efficient and it produces an accurate estimate of the fundamental frequency in the presence of harmonics and noise, which is a prerequisite to frequency relaying in power systems. Several computer simulation results are presented in the paper to show the effectiveness of the algorithm. The algorithm is simple and suitable for real time implementation. Further the accuracy of this approach in presence of harmonics and noise is improved considerably.