Abstract: To improve the response of the rectifier side when the inverter side of voltage sag generator（VSG） simulates that voltage sags, a novel high-performance control strategy based on nonlinear control was proposed. In the proposal an energy function which relative degree is two and reactive current component were considered as outputs. Then a full feedback linearization of the under-actuated three-phase pulse width modulation（PWM） rectifier was obtained without model simplifications, thus avoiding zero dynamics of the system. The feedback regulation based on the energy function was used to improve the robustness against model parameter uncertainties. In addition, a simple open loop controller which can realize balanced and partial unbalanced voltage sags was designed for the inverter side of VSG according to the vector relationship of three-phase voltages. Digital simulation and practical experimental results show that the proposed control strategy has good performance in improving dynamic response when the VSG system voltage sags, guaranteeing fast regulation and stability of dc-bus voltage and achieving unity power factor control for input AC voltage.