A comparison and trade-offs between induction generator control options for variable speed wind turbine applications

This paper compares wind turbine driven doubly-fed induction generator (DFIG) cascade, one of today´s state of the art variable speed solutions, and squirrel cage IG with full-scale converter in the light of incoming stricter regulations for grid connection and converter sizing. Direct grid connection of the stator winding in DFIG cascade suggests that this concept would be more critical to comply with the regulations and the power rating of the converter (2×30%) likely would have to be increased. Also, in normal operation, employing thermal analysis of the power electronics switching components conducting low frequency rotor current, the issue of over-sizing of the DFIG cascade is addressed.