Comparative study of single-phase fundamental component frequency estimation schemes under time-varying harmonic distortion operation

This paper presents an adaptation of a fundamental frequency estimation scheme based on a fast-tracking PLL-based structure. The approach is based on a modification of the Adaptive Quadratic Signals Generator Phase-Locked Loop, adding a pre-filtering stage in order to attenuate the influence of the time-varying harmonics. The time-domain discretization of the proposed scheme is also presented. A comparison between the proposed scheme and a highly accurate Zero-Crossing scheme is performed under time-varying harmonic operation conditions through experimental measurements. While the later is able to provide only the frequency value, the proposed scheme is able to provide both the frequency value, the fundamental component wave form, and its quadratic companion signal, keeping the same fast-tracking characteristic and presenting a smoother behavior.