Design of FIR second‐degree differentiator for frequency estimation

Finite‐impulse‐response (FIR) lowpass second‐degree differentiators (with coefficients that are based on an optimal design approach) are presented. By minimising the filter variance, the differentiator rejects noise above the cut‐off frequency, with steep roll‐off in the transition‐band, and showing close‐to‐ideal magnitude response accuracy in the passband. The proposed FIR differentiators are used to estimate the principal frequency of a non‐ideal power system, based on a variant of Sarkar and Sengupta's algorithm. Use of an FIR filter, rather than an infinite‐impulse‐response (IIR) filter, for fundamental frequency estimation is shown to improve the accuracy of frequency estimation.