To address the challenges posed by the increasing penetration of wind power on grid frequency regulation, this paper establishes a life-cycle cost-benefit calculation model for wind farms equipped with energy storage systems participating in primary frequency regulation services. The model considers energy storage costs, real-time electricity revenue, and primary frequency regulation revenue, with energy storage capacity and power as decision variables. To tackle the difficulty of accurately evaluating primary frequency regulation actions, a frequency regulation model for the combined wind-storage system is developed using an open-loop processing method based on the closed-loop dynamic process of the power system frequency. This model incorporates wind turbine control and energy storage system state-of-charge (SOC) constraints, and proposes an open-loop calculation method for primary frequency regulation actions using annual frequency curves as inputs. By combining the wind-storage system frequency regulation simulation model with annual operational frequency and power data of the wind farm, the change rule of the annual energy storage costs and primary frequency regulation revenue are obtained. The results show that for a wind farm with an installed capacity of 30 600 kW, the optimal primary frequency regulation revenue is achieved when the energy storage power is 4 553.6 kW and the energy storage capacity is 9 822.6 kWh.