Now existing voltage sag simulation method only considers normal and various fault situations of the infinite power grid so that the voltage drop on the load does not match the actual power grid. In this paper, voltage sag simulation method based on Thevenin equivalent model is proposed. Thevenin equivalent parameters on voltage sag based on impedance switching method is proposed in this paper to identify voltage value before and after sag. H-bridge cascaded inverter is chosen as voltage sag simulation device in this paper. To simulate external characteristics of actual grid voltage sag, virtual impedance control strategy which is feasible to H-bridge cascaded inverter is proposed. Setting of voltage reference and virtual impedance can realize simulation of voltage sag Thevenin equivalent external characteristics. Finally, effectiveness and feasibility of proposed voltage sag Thevenin equivalent parameters identification method and voltage sag simulation device control strategy are testified.
