Comparative Study of Two Phase Locked Loop Algorithms for Grid-Connected Inverter Synchronization

Abstract

This research paper conducts an assessment of the Phase-Locked Loop (PLL) algorithm's performance in synchronizing voltage source inverters with the utility grid. Although two primary synchronization techniques, namely αß and dq PLLs, are commonly used, specific conditions suitable for each technique have not been thoroughly documented. The evaluation process involves both theoretical testing and simulation in the MATLAB/Simulink environment. The results demonstrate that the αß PLL technique exhibits robust performance, achieving precise grid voltage synchronization under both normal and abnormal grid conditions. Furthermore, it demonstrates effective harmonic filtering capabilities, achieving a Total Harmonic Distortion (THD) of 1.73% and 1.71% when faced with phase and frequency jump distortions in the grid voltage, respectively. Importantly, these THD results for the αß PLL technique adhere to the IEEE Standard 929-2000's specified limits. In contrast, the dq PLL technique does not perform effectively, particularly under abnormal grid conditions. It struggles with synchronization and harmonic filtering, resulting in THD values that exceed the specified limits. The findings indicate that αß PLL synchronization is a promising technique, capable of facilitating successful inverter-grid power synchronization even in adverse grid conditions. This proficiency in grid integration enhances the potential for injecting more renewable energy into the grid, contributing to increased power availability for distribution to households.