Reactive power capability of a wind turbine with doubly fed induction generator

The aim of the work is to derive a steady state PQ-diagram for a variable speed wind turbine equipped with a Doubly Fed Induction Generator. Firstly, the dependency between optimal rotor speed and wind speed is presented Secondly, the limitations in reactive power production, caused by the rotor current, the rotor voltage and the stator current are derived Thirdly, the influence of switching from A to Y coupling of the stator is investigated Finally, a complete PQ diagram for a wind turbine is plotted It is concluded that the limiting factor regarding reactive power production will typically be the rotor current limit, and that the limit for reactive power absorption will be the stator current limit. Further, it is concluded that the rotor voltage will only have a limiting effect at high positive and negative slips, but near the limitation, the reactive power capability is very sensitive to small changes in the slip. Copyright (C) 2007 John Wiley & Sons, Ltd.