Large-scale grid-connected wind farms based on doubly fed induction generators (DFIGs) would reduce system equivalent inertia, and the ability of primary frequency control would deteriorate. In order to make the wind turbine can participate in the frequency adjustment of power grid, this paper proposes the frequency control strategy that adds the virtual inertia control and over-speed control on the rotor side, so that DFIGs have similar static frequency regulation performance of the synchronous generator. The virtual inertia control can release the kinetic energy of the rotor and provide short-term support for the frequency; the over-speed control can gain reserve capacity, compensate the secondary drop in the frequency caused by the inertia control, and reduce the steady-state error. Finally, this paper simulates and analyzes the influence of wind power participating in the frequency adjustment on the Shanghai power grid frequency during the large-scale wind farm access to the Shanghai power grid.