To solve the problem that the wind power grid-connected system lacks sufficient frequency support during frequency fluctuation, the virtual synchronous generator (VSG) algorithm is introduced in the wind turbine main control, and the energy storage type static synchronous compensator (STATCOM/BESS) is used for the rotation of the wind turbine to enhance the virtual inertia of the system. According to the frequency deviation and frequency change rate, the STATCOM/BESS working mode is adjusted to obtain adaptive virtual inertia considering the state of charge of the battery (BESS). Through the analysis of the small signal model of the wind turbine-VSG, the setting principle of the virtual inertia is determined, the reasonable range of BESS capacity allocation is further given, and the BESS capacity configuration combined with economic description is optimized. Simulation results obtained by PACSD/EMTDC show that the proposed method can effectively improve the dynamic response of frequency and enhance the frequency support of wind power grid-connected systems. This work is supported by National Natural Science Foundation of China (No. 51507065).