An enhanced virtual synchronous generator strategy for suppressing grid voltage sag

When a severe grid voltage sag has happened, the transient rush current caused by grid voltage sag can not be effectively suppressed by the voltage controlled grid tied inverter based on the conventional virtual synchronous generator(VSG) control. In order to improve the capacity of voltage controlled grid tied inverter to withstand power grid voltage sag, the paper proposes an enhanced robust strategy. A coordinated VSG control combined with direct current control based on PQ mode is introduced to rapidly restrain current. For better voltage adjustment performance, power grid voltage sag compensation, feedforward control and reactive power support strategy are added. By the enhanced VSG control, the rush current can be effectively restrained. The effectiveness of the proposed strategy is verified by PSCAD/EMTDC simulation.