Aiming at the difference between conventional power electronic interface converter and traditional synchronous generator in microgrid, it cannot provide inertial support and damping effect for microgrid. In this paper, a converter based on virtual synchronous generator technology is used to design the power outer loop and the electromagnetic equation, so that the power electronic converter has some external characteristics of the synchronous generator while providing some damping and inertia for the microgrid, It is clarified that sag control is essentially a kind of virtual synchronous generator control. Finally, the feasibility and correctness of the method are verified by MATLAB simulation.