An adaptive quasi-notch filter for a biased sinusoidal signal estimation

This note presents an alternative approach to classical adaptive notch filters designed to identify the frequency, magnitude, phase and offset of a biased sinusoidal signal. The algorithm takes advantages of an adaptive law for the resonant frequency of a third-order generalized integrator as a part of an orthogonal-signals generator system. The resulting estimator presents a dynamic order equal to 4. The strength of the discussed strategy results in a fast and accurate signal tracking capability and a good rejection to noise. The properties of the algorithm are verified in simulations in a range of signal conditions, such as step and sweep changes in frequency and voltage sag confirming the effectiveness of the strategy for estimation and tracking of time-varying parameters.