1 ESTIMATION OF TIME-VARYING MAINS FREQUENCIES

This paper discusses the estimation of mains frequencies which vary with time. The recently proposed CP function [1] is proposed as a tool which is highly suited to estimation of time-varying mains signals. It can be shown that if the mains frequency trajectory can be modeled (at least locally) as a quadratic function of time, then the frequency trajectory can be estimated with near optimal accuracy. Such accuracy is not achievable with conventional techniques such as “running Fourier transforms ” because the latter implicitly assume that the spectral content of the signal under analysis is stationary