Leveraging half-cycle orthogonal signal generation approach for PLL-less tracking of single-phase grid parameters

This article presents a fast and accurate single-phase grid voltage parameter tracking scheme under distorted grid voltage conditions. The input stage of the proposed scheme consists of a half-cycle moving-window discrete Fourier transform (HC-MWDFT) based pre-filter, whose design guidelines are discussed in the viewpoint of its stability and orthogonal signal generation. Combining a positive feed-forward comb filter and a fractional complex resonator helps to attenuate odd-order harmonics and allows fast extraction of fundamental components. Unlike the phase-locked loop (PLL) techniques, the grid frequency is indirectly estimated using a simple open-loop frequency detector. The proposed method is free from tedious controller tuning aspects and can avoid external phase/frequency feedback loops. The amplitude and phase information are adaptive to the grid frequency by employing a simple linear regression-based error correction technique. The overall efficacy of the proposed algorithm is assessed using numerical and experimental methods.