Abstract: To suppress voltage sags under extreme conditions,from the perspective of the cooperation between the super capacitor and the battery,the power margin of the system is improved by precisely controlling the voltage of the super capacitor without increasing the capacitance in this paper,so as to reduce voltage sags under extreme conditions. A microgrid model based on ultracapacitors and battery energy storage is established in PSCAD/EMTDC. In PSCAD/EMTDC, a microgrid model based on super capacitor and battery is established. The simulation results show that the proposed control strategy can effectively alleviate the voltage sag of the microgrid under heavy load,and the voltage drop amplitude is reduced by 13.7%.