The basic mathematical model of doubly-fed induction generator (DFIG) participating in grid frequency regulation is presented. The relationship between wind power penetration, the proportion of wind turbines with adjustable frequency ability, the frequency regulation coefficient of wind turbines, and wind power utilization is derived under different operating modes (such as inertia control or maximum power tracking) after large-scale wind power is connected to the grid. The control strategies for wind turbines to participate in grid frequency regulation under different operating modes are proposed. Taking a grid in southern China as an example, the impact characteristics of wind power injection ratio on grid frequency regulation under changing wind speed and load conditions are analyzed, and the effectiveness of renewable energy generation with adjustable frequency ability in grid frequency regulation is verified. By connecting wind turbines with adjustable frequency ability to a 4-machine 2-area grid model, the minimum proportion of required wind turbines and the comprehensive carrying capacity of the grid for renewable energy under different wind power injection ratios are presented. Simulation results show that when large-scale wind farms participate in frequency regulation, it is advisable to involve turbines operating near rated wind speed to minimize grid frequency deviation and maintain frequency within the safe operating range.