Influence of the variable speed wind generators in transient stability margin of the conventional generators integrated in electrical grids

Summary form only given. This work demonstrates that the integration of variable speed wind systems with doubly fed induction generators and a four quadrant AC-to-AC converter connected to the rotor windings (DFIG), increases the transient stability margin of the electrical grids, when compared with the case where the fixed speed wind systems with cage generators are used. The results clearly show that the DFIG improves the short-term postfault stability of the conventional synchronous generators in the network. It is due to the influence of the two dedicated rotor current regulators of the DFIG on the dynamic behavior of the other generators in the system. The reduction in dynamic reactive compensation demands was also observed when using the DFIG, which helps to avoid other problems as voltage collapse in the power system. Besides, adequate models to represent the behavior of the DFIG in transient stability studies are presented. From the simulation results some important conclusions can be extracted to guide the integration of the wind farms on weak or strong grids.