Abstract: Focusing on wind farms consisting of squirrel-cage induction wind turbines, equivalent models of wind farm performances were established by capacity-weighted, improved capacity-weighted and parameters transformation stand-alone turbine equivalent methods and multi-machine equivalent methods with variable-scale and reduced-order, in which parameters of electrical collection systems and transformers in wind farms were considered. Through the P-V analysis, the above equivalent models were compared to the real and comprehensive models in terms of approximations of static voltage stability margins. It was concluded that multi-machine equivalent method performs better when wind turbine parameters in a wind farm are the same; while parameter transformation method is suitable to the situation of different parameters.

Key words: wind farm, squirrel squirrel-cage induction wind turbines unit, electrical collection system, voltage stability, equivalent model