ENHANCED PERFORMANCE OF A DOUBLY FED
WIND-POWER INDUCTION GENERATOR AT WIND-
RANGE BOUNDARIES
ABSTRACT
The doubly fed induction generator (DFIG) is one of the largest generators used
with MW-class wind turbines. This paper focuses on the weak performance areas
of grid-connected DFIG-based wind turbines. Basically, the DFIG performance at
low wind speeds, close to the cut in speed, and around the full rating operation (in
the vicinity of rated wind speed) is investigated. For low wind speed region, the
causes of decreased efficiency of the DFIG-based wind turbines are discussed in
details. A modified control to extend the concept of maximum wind power tracking
to cover the low wind speed region is presented. The associated effects of the ex-
panding technique are examined. For higher wind speeds, the strategy of reactive
power flow and the converter ratings are the most significant factors affecting the
performance of the DFIG system. Different strategies for reactive power flow are
discussed and different converters ratings are considered. An optimum technique
for reactive power control is proposed to capture maximum wind power with
minimum losses. Moreover, this methodology ensures a unity power factor flow at
the generator terminals. Reasonable values for the dc page link voltage and converter
ratings are investigated. A comprehensive time-domain model for the wind turbine
with DFIG and the decoupled dq controller are implemented using Mat-
lab/Simulink software. Comparative simulation results are included to ensure the