1.Department of Electrical Engineering, Tsinghua University, Beijing 10084, China;2.State Key Laboratory of Control and Simulation of Power System and Generation Equipments;(Tsinghua University), Beijing 100084, China;3.Yunnan Power Dispatching and Control Center, Kunming 650011, China

Frequency oscillation is a small disturbance stability problem in the active frequency control process. Previous studies have focused on the analysis of generator governors and prime movers. Power system stabilizers can also be used to suppress frequency oscillations. The effect mechanism of the generator excitation system on the frequency oscillation is analyzed. When the load has the voltage regulation effect, the generator excitation system affects the load power by the load voltage, thus affecting the frequency oscillation. The process of frequency deviation affecting electromagnetic power through power system stabilizer, excitation, network and load is given. The damping torque theory is used to calculate the electromagnetic power damping coefficient and the influence of power system stabilizer is analyzed. The evaluation method of the effect of different generator power system stabilizers on frequency oscillation damping in multi-machine system is proposed. It is more effective to improve the frequency oscillation damping by selecting the generator with large influence to optimize the parameters. The analysis results are verified by the simulation on IEEE 4-machine 2-area system.