Operational restrictions with maximum power extraction of DFIG connected wind farms

Doubly Fed Induction Generator (DFIG) based wind farms are one of the major contributors to wind power generation. The capability of generating active power over an extended range of speed has made it attractive to maximize the power extraction from wind. This has also facilitated reduction of mechanical stress in the turbine. However recently it has been reported that achieving the maximum power extraction at high wind speeds is a major issue for large wind farms while satisfying grid code requirements. This paper discusses the limitations of the DFIG on the maximum power exaction control and a study is presented to improve its performance. The DFIG model is briefly discussed. Difficulty on achieving reactive power control at higher rotor speeds is explained in detail with variation of stability margin along the maximum power extraction curve. A controller is proposed to validate the steady state results. The effects of DFIG machine parameters on the stability and performance also have been studied.