With the high penetration of large-scale wind farms (WFs), accurate grid-connected WF models are crucial to be developed for studying the stability of power grids. Due to the large scale of the detailed model, a grid-connected WF is usually simplified into several aggregated wind turbine generators (WTGs) with the dynamic equivalent technique. However, identifying large amounts of parameters in an aggregated WTG may result in a multi-solution issue that reduces the accuracy and robustness of the developed models. Moreover, several aggregated WTG models which need to be identified simultaneously further complicate the issue. Therefore, to solve this issue, a dynamic equivalent modeling approach that could accurately estimate the full parameter of the equivalent WF model is developed. First, a WTG clustering approach is designed to simplify the WF model into several aggregated WTGs. Then, the external system of the aggregated WTG is simplified with the hybrid dynamic simulation (HDS) technique, by which the parameters of each aggregated WTG could be identified independently. Also, the WTG parameters are grouped with the trajectory sensitivity and identified using the well-designed multistage parameter identification approach. The simulation results in the modified IEEE 39-bus system demonstrated the effectiveness of the proposed method.