Abstract: Virtual synchronous generator（VSG）provides a friendly grid-connected method for renewable energy. However,the conventional VSG is prone to be overcurrent and out of use when grid voltage sag happens. In this paper,the static and transient characteristic of the VSG during symmetrical grid fault is analyzed based on its basic model and a modified low voltage ride-through（LVRT）control method is proposed. The proposed method cuts off the reactive power-voltage control loop of the VSG in grid-connected mode,and protects the VSG from overcurrent in steady state by the coordination control of active and reactive power,at the same time,provides reactive power support to the grid. Besides,an adaptive virtual impedance according to the maximum phase current is introduced to suppress the amplitude of transient fault current. Simulation results based on Matlab/Simulink have proved that the characteristic analysis and the proposed LVRT control method are effective.