Abstract: The low-voltage ride-through in photovoltaic power generation is a key problem for photovoltaic inverters connected to grid. Aiming at the frequency- and phase-locking of low-voltage ride-through on the photovoltaic inverter during asymmetric fault on the grid and using positive and negative sequence separation, a dual second-order generalized integral frequency- and phase-locking algorithm (DSOGI-FLL-PLL) is proposed, and a simple FLL is used so that positive and negative sequence separation can be performed for various frequencies. The conventional phase-lock- loop (PLL) is also used to capture the grid-side voltage, which greatly reduces response time and error of PLL during asymmetric faults on the grid. Simulation results show that this method, when applied to track low-voltage ride-through on photovoltaic inverter connected to grid, can save about two third of the frequency-lock and phase-lock response time.

Key words: photovoltaic power, fast phase lock, second-order generalized integrator (DSOGI), low voltage ride-through (LVRT)