High-Order Sliding Mode Control of DFIG-Based Wind Turbines - Wind Turbine Control and Monitoring - page 24

Wind Wind

Gearbox Gearbox DFIG & Converters DFIG & Converters

WT Aerodynamics WT Aerodynamics

Grid connection Grid connection

Fig. 2.1 Wind turbine global scheme

Fig. 2.2 Wind turbine power
coefficient

As is in [ 7 ], the following simplified model is adopted for the turbine (drive
train) for control purposes.

J t x mr ¼ T a K t x mr T g ð 2 : 4 Þ

Where J t is the turbine total inertia, K t is the turbine total external damping, and
T g is the generator electromagnetic torque.

2.2.2 Generator Model

The WT adopted generator is the DFIG (Fig. 2.3 ). DFIG-based WT will offer
several advantages including variable speed operation (±33 % around the syn-
chronous speed), and four-quadrant active and reactive power capabilities. Such
system also results in lower converter costs (typically 25 % of total system power)
and lower power losses compared to a system based on a fully fed synchronous
generator with full-rated converter. Moreover, the generator is robust and requires
little maintenance [ 8 ].