A wind farm typically consists of a large number of wind turbines with relatively small size generators. In order to reduce computation time and complexity in power system stability studies, it is therefore desirable to aggregate wind turbines in the wind farm into a reduced number of equivalent units. The aggregation should be made without missing important properties or behaviors of wind power generation systems for the associated studies. Models of single and aggregated wind turbines are presented in the paper. The importance of induction generator and mechanical drive train models of wind turbines is examined. Simulation results of the models are then compared with field measurement data. Copyright © 2007 John Wiley & Sons, Ltd.