1.School of Automation, Nanjing University of Science and Technology, Nanjing 210094, China;2.Jiangsu Frontier Electric Technology Co., Ltd., Nanjing 211102, China;3.Jiangsu Electric Power Test Research Institute Co., Ltd., Nanjing 211103, China;4.School of Electrical and Electronic Engineering, North China Electric Power University, Baoding 071003, China

In recent years, frequency oscillations have taken place multiple times in actual power grids. Research shows that this phenomenon is closely related to the dynamic frequency regulation process of power systems, including the primary frequency regulation (PFR) mode and the automatic generation control (AGC) mode. In order to analyze the dynamic effects of different frequency regulation processes on the frequency oscillation and clarify the intrinsic differences between different oscillation modes and oscillation performance, the theory of damping torque analysis (DTA) is extended, and a DTA method suitable for frequency stability analysis of power systems is established, which can reveal the generation, distribution, and transmission mechanism of damping torque in the frequency regulation control process. Meanwhile, a method for identifying the frequency oscillation modes of power systems is proposed based on this method, and an index for identifying the damping torque modes is defined. The index can effectively reflect the damping contribution and influence of frequency regulation link to the oscillation mode, and accurately identify the frequency oscillation modes of the system. The effectiveness and feasibility of the proposed method are verified by the simulation examples, and the oscillation behavior and influence mechanism of different modes are analyzed.