Impact of fixed and variable speed wind generators on the transient stability of a power system network

This paper compares the effect of fixed speed and variable speed grid-connected wind generators on the transient stability of a power system network. The wind generators considered are the squirrel cage induction generator (SCIG), which is a fixed speed, the doubly-fed induction generator (DFIG) and the converter driven synchronous generator (CDSG) which are variable speed. Two scenarios are investigated. Under the first scenario, the conventional synchronous generator is not equipped with an automatic voltage regulator (AVR) when the system is subjected to a three-phase fault. The penetration level of the wind generators is increased until instability is reached or the stability margin of the network is significantly reduced. Under the second scenario, the conventional synchronous generator is equipped with an AVR, and the wind generator with the worse performance under the first scenario is used to investigate the effect of the AVR on the transient stability. Simulation results show that the squirrel cage induction generator performs poorly and contributes negatively to the transient stability of the power system´s network as compared to both the doubly-fed induction generator and the converter driven synchronous generator. When the AVR was included the transient stability of the system improved and the system was able to tolerate a further increase in the level of penetration of the squirrel cage induction generator without loosing its stability.