An investigation of PLL synchronization techniques for distributed generation sources in the grid-connected mode of operation

In recent years, the proliferation of grid-connected microgrid systems has witnessed a remarkable surge, driven by the need to enhance the availability and reliability of renewable energy sources during peak demand periods. By reducing reliance on fossil fuels, these systems offer promising avenues for sustainable energy integration. To ensure seamless synchronization of renewable energy sources with the grid, Phase-Locked Loop (PLL) controllers have emerged as a key solution. However, the information available about these PLLs is limited. In this paper, the analysis, design, and comparison of PLLs, along with the exploration of a recently developed PLL synchronization method. Specifically, we evaluate the performance of prominent PLL techniques, including PSRF-PLL, SOGI-PLL, DSOGI-PLL, E-PLL, and IPT-PLL, under diverse test scenarios such as voltage sag, swell, unbalance, and harmonics. To assess their effectiveness, hardware-in-loop virtual and real-time test-beds are employed, enabling rigorous examination of the PLL techniques for grid synchronization. The reported results demonstrate the phase tracking capability when operating in grid-connected mode. Finally, conclusions are drawn from studies conducted in the electrical grid network's healthy and unhealthy environments.