Phase-Locked Loop-Based Grid Synchronization under Distorted Grid Conditions

Abstract

A grid-connected conversion power electronic converter must be grid-synchronised, specifically in the renewable energy system like integrating photovoltaic and wind power. Non ideal grid conditions (harmonic distortion, voltage unbalance, frequency variation) however are known to severely impair the synchronisation accuracy and system stability. In this paper, a grid synchronisation method based on a phase-locked loop (PLL) is provided to address the issue of working in the distorted grid conditions. The suggested structure includes the refined filtering and better control parameters aimed at the better harmonic rejection and moving performance. An elaborate mathematical model of the PLL is constructed and its performance is assessed in various disturbance conditions, such as harmonic injecting (5th and 7 th order), voltage sag (20 percent) and frequency error. The simulation outcomes are able to show the proposed PLL is able to reach a lower settling time of about 10 ms, a phase error of less than 0.6deg, an overall harmonic distortion (THD) of 2.1 as compared to the conventional SRF-PLL and SOGI-PLL methods. Moreover, the system operates reliably with regards to extreme grid perturbations that guarantee proper tracking with phase and frequencies. The suggested method offers an effective and consistent synchronisation solution to the contemporary renewable energy systems that have to operate in non-ideal grid conditions.