Abstract: Wind power output has characteristics of fluctuation so that the largescale gridconnected wind farm affects the stability of power system operation. The appropriate capacity energy storage systems used in largescale wind farm not only can smooth power output but also can improve the power controllability, so that power quality and stability can be effectively improved. The advantages and working principle of VRB are analyzed in detail. The equivalent circuit model of VRB is established and chargedischarge characteristics are analyzed by simulation. The advantages and broad market of VRB used in wind power system are illustrated. In the end, the research status of VRB in China is introduced.