Challenges for generator circuit-breakers connected with doubly-fed induction generators

Abstract

Variable-speed turbines have gained increasing importance in pump-storage power stations since they present big advantages compared to the classical topology with a synchronous generator. Within the variable-speed solutions, the one employing a doubly-fed induction generator (DFIG) has become the preferred solution for large installations since it provides the advantages of variable-speed operation and four-quadrant active and reactive power capabilities using converters rated only a small fraction of the rated power. A deep understanding of the characteristics of the fault current fed by a DFIG after a three-phase short-circuit at its terminals is of utmost importance to define the requirements of the generator circuit-breaker (GenCB) to be installed between the generator and the step-up transformer. The only standard which covers the requirements for GenCBs is IEEE Std C37.013-1997 (R2008) with its amendment IEEE Std C37.013a-2007; which will be soon replaced by the IEC/IEEE Joint Development IEC/IEEE 62271-37-013. The requirements laid down in this standard are based upon applications employing synchronous generators. The question whether these requirements are adequate for the application of GenCBs in pump-storage power stations employing DFIGs is considered in the present work.