Abstract: The voltage source energy storage converter instantaneous reactive power support for voltage at point of common coupling under the grid voltage sag fault. In order to solve the transient problem caused by the characteristics of voltage source converter, this paper, a voltage source energy storage converter model is established to analyze the coupling effect of grid voltage sag and reactive power support, and determine the influence of key control parameters on the transient stability of voltage source energy storage converter. The proposed reactive power support control strategy, based on the dynamic voltage regulation coefficient(DVRC), aims to enhance the voltage support characteristics of the power converter system by adaptively adjusting the voltage regulation coefficient during grid voltage sag. This approach ensures a stable operating point for the energy storage system and improves its transient stability. Simulation and experiments demonstrate the effectiveness of the proposed control strategy.