A Comparative Study of Grid Synchronization Techniques SRF-PLL and DSRF-PLL Under Unbalanced Grid Voltage Condition

This paper presents a comparative study of two grid synchronization techniques, synchronous reference frame phase-locked loop (SRF-PLL) and double synchronous reference frame phase-locked loop (DSRF-PLL) that could be used in grid integration of distributed generation systems. As PLL is playing a vital role in the operation of grid-connected power electronic converters, it is very much important to study their behavior in grid voltage fluctuating condition. It is shown that SRF-PLL gives suitable response when the grid voltage is balanced, but during fluctuating condition of voltage its performance gets deteriorated. But DSRF-PLL is able to track grid voltage phase properly in both conditions as it is having two components separated and decoupled from each other using decoupling network. Performance comparison is verified by MATLAB simulation, and the results are presented.