Research on phase-locked loop of photo voltaic grid-connected inverter in weak grid

Dual second-order generalized interger (DSOGI) can accurately extract the grid voltage phase-locked angle in the case of grid voltage imbalance. However, in the environment with high harmonic, due to the dependence of the double second-order generalized integrator on the frequency, which leads to large phase-locked error and unstable system. In this paper, the DSOGI-PLL is improved. The harmonic elimination module is used to eliminate the harmonic components in the grid voltage, which effectively reduces the influence of harmonics on the output phase angle. Simulation and experimental results show that the improved phase-locked loop can effectively reduce the phase-locking error in the weak grid environment.