A Discrete-Time Non-Adaptive SOGI-Based Frequency-Locked Loop

Abstract

Second-order generalized integrator (SOGI)-based phase-locked loops (PLLs)/frequency-locked loops (FLLs) are the most commonly used methods for grid synchronization. While the SOGI in these standard SOGI-PLLs/FLLs is adaptive to the estimated frequency, which results in the coupling between the SOGI and PLL/FLL, and this coupling brings about difficulties in stability analysis and parameter tuning. In order to reduce this coupling between the SOGI and PLL/FLL, this letter proposes a novel discrete-time non-adaptive SOGI-FLL based on gradient descent algorithm, of which the relationship of the orthogonal signals generated by discrete-time non-adaptive SOGI is used to construct the linear model of frequency parameter. The global convergence analysis and parameter tuning are given. The proposed FLL features no discretization errors, simple convergence analysis and parameter tuning. Experimental results show that the proposed FLL has smoother dynamic performance and can be designed to have higher disturbance rejection ability or faster response speed than the commonly used methods.