Robust estimation of real-time single-phase grid voltage frequency under distorted conditions

This paper proposes a robust estimation technique of the real-time single-phase grid voltage fundamental frequency under distorted conditions. The proposed technique consists of a demodulation method and a finite-impulse-response based differentiation filter. A frequency domain analysis is presented for designing the differentiation filter relying on a modulating function strategy. The differentiation filter is used to estimate the time-varying fundamental frequency from the instantaneous phase angle obtained by the demodulation method. The proposed technique is capable of providing accurate estimation of fundamental frequency and can also reject the negative effects caused by the presence of the DC offset, harmonics and noise. Moreover, there are no stability issues in the open loop system of the proposed technique. The effective application of the proposed technique is confirmed by real-time experimental results.