With the rapid growth of grid-connected wind power penetration level, it is necessary to study the impacts of wind power on power system stability. The small-signal stability of power systems with large-scale wind power is explored using the eigenvalue analysis method. A prototype sample system, the two-synchronous-generator system with awind farm, is proposed for the oretical analysis. Then, simplified models of wind turbines (WTs) and the corresponding equivalent models of wind farms are analyzed. Three kinds oftypical WT models, i.e., squirrel cage induction generator,doublyfed induction generator, and permanent magnet synchronous generator are used. Furthermore, based on thesimplified equivalent models, effects of large-scale windfarms on the electromechanical oscillation modes (EOMs) of synchronous systems are discussed. Simulation results indicatethat wind farms of the three kinds of WTs have positive effects on EOMs. However, long transmission lines connecting wind farmto the system may produce negative effectson the small-signal stability of the system.