Aiming at the negative impact of island microgrid asymmetric faults on the inverter, a two-stage photovoltaic grid-connected inverter is taken as the research object. Based on traditional dual second-order generalized integrator phase-locked loop, aiming to improve phase-locked accuracy, a DSOGI-PLL optimization design method is proposed by using the fusion technology of harmonic cancellation module (HCM) and improved frequency-locked loop (SOGI-FLL). Based on this, an improved two-stage photovoltaic low voltage ride-through (LVRT) optimization control method is constructed. In this method，the DC voltage of the grid-connected inverter is stabilized and output power fluctuation is suppressed to further improve the fault ride-through capability of the inverter when a microgrid fault occurs. Finally, an RT-LAB real-time simulation platform is used to construct an island microgrid model with photovoltaic grid connection. The effectiveness of the proposed improved phase-locked loop and LVRT Optimal Control method for photovoltaic inverters is verified by simulating asymmetric faults in the microgrid lines.