Improved grid synchronization algorithm for DG system using DSRF PLL under grid disturbances

Distributed Generation (DG) System is a small scale electric power generation at or near the user´s facility as opposed to the normal mode of centralized power generation. In order to ensure safe and reliable operation of power system based on DS, grid synchronization algorithm plays a very important role. This paper presents a Double Synchronous Reference Frame (DSRF) phase locked loop (PLL) based on synthesis circuit for grid synchronization of distributed generation (DG) system under grid disturbances. Due to flexible in characteristics, DSRF PLL can accurately detect the phase irrespective of the grid conditions. Further, it demonstrates how the PLLs track the phase angle during some of the major abnormal grid conditions like voltage unbalance, line to ground fault and voltage sag etc. The superiority of DSRF PLL over SRF PLL is well illustrated by the simulations results obtained from MATLAB/SIMULINK environment.