Estimation of frequency and its rate of change for applications in power systems

A new method for estimation of power frequency and its rate of change is presented. Unlike conventional methods which are based on the concept of linearization, the proposed scheme accommodates the inherent nonlinearity of the frequency estimation problem. This makes the method capable of providing a fast and accurate estimate of the frequency when its deviation from the nominal value is incremental or large. The estimator is based on a newly developed quadrature phase-locked loop (QPLL) concept. The method is highly immune to noise and distortions. The estimator performance is robust with respect to the parameters of its structure. Structural simplicity and performance robustness are other salient features of the method.