SYNCHRONIZATION OF GRID-CONNECTED INVERTERS: FUNDAMENTALS AND IMPLEMENTATION OF THE SOGI-PLL ALGORITHM

Abstract

This chapter presents the fundamentals and implementation of the frequency synchronization loop for grid-connected three-phase inverters, focusing on the Synchronous Reference Frame Phase-Locked Loop (SRF-PLL) architecture. Given that the classical SRF-PLL topology is vulnerable to grids with harmonic distortion, this study details the integration of a pre-filter based on a Second-Order Generalized Integrator (SOGI). The resulting structure, known as DSOGI-PLL, is capable of substantially attenuating the harmonic content of the voltage signal while simultaneously generating positive-sequence orthogonal signals for the control loop. Dynamic validation of the system confirms the approach's effectiveness, demonstrating rapid and accurate tracking in response to frequency steps, as well as high rejection of power quality disturbances. It is concluded that the DSOGI-PLL algorithm constitutes a robust and essential technical solution for ensuring stable operation and clean power injection by static converters at the point of common coupling.