M.Khederzadeh; M.B.Soltani

ABSTRACT
Fast and accurate estimation of frequency and its rate of change is essential for control and protection of
power systems. Most digital algorithms for measuring frequency have acceptable accuracy if voltage
waveforms are not distored. However, due to non-linear devices the voltage waveforms can include higher
harmonics. The frequency estimation is inherently a nonlinear problem.Thus, those methods which are
based on linearization cannot accurately deal with large deviations of frequency. This paper presents a
technique for frequency estimation that provides accurate estimates in asynchronous sampling and requires
modest computations. Theoretical basis and practical implementation of the technique are described. These
techniques are adversely affected by the presence of harmonics in the signals.