Benchmarking of phase locked loop based synchronization techniques for grid-connected inverter systems

Grid-connected renewables are increasingly developed in recent years, e.g. wind turbine systems and photovoltaic systems. Synchronization of the injected current with the grid is mandatory. However, grid disturbances like voltage sags, harmonics, and frequency deviations may occur during operation, becoming inevitable challenges to the synchronization of the grid-connected renewable energy systems. In order to ensure the quality of the power generation from the renewables, robust and reliable synchronization methods are in demand. Among the prior-art solutions, Phase Locked Loop (PLL) based synchronization methods have gained much popularity in grid-connected applications. However, an appropriate selection and thus a proper design of the selected PLL synchronization remain of interest in practice, especially for single-phase systems. Therefore, in this paper, a benchmarking of the main PLL synchronization methods for single-phase grid-connected inverter systems in terms of accuracy, dynamic response, harmonic immunity, etc., has been conducted. Experiments on a 1-kW single-phase grid-connected system, suffering from different grid disturbances, are performed for the benchmarking. The experimental results have verified the discussions.