Abstract: An inertia evaluation method has been proposed that incorporates the rate of change of frequency（RoCoF）and the constraint of the minimum frequency point, considering the frequency modulation capabilities of new energy stations. The RoCoF constraint section initially takes into account the suppressive effect of static load voltage on frequency fluctuation, the impact of current source virtual inertia on system imbalance power during frequency modulation participation, and the spatial distribution characteristics throughout the dynamic frequency response process. Subsequently, in the part of considering the minimum frequency constraint, a general ASF model based on the classical average system frequency（ASF） model considering the access of new energy stations and generator speed control system is proposed. This model is derived from the classical ASF model, integrated with a low-order general model of the generator speed control system and the general frequency response model of new energy stations. The model enables to predict the time at which the system reaches its lowest frequency under a specific disturbance and provide a time-domain expression of frequency variation to assess the minimum inertia. The enhanced 3-machine 9-node and 10-machine 39-node systems are employed to simulate different disturbance types and sizes for analysis of the proposed method, thereby validating its accuracy and applicability.