  We discuss non-ideal torque control in wind turbine systems (WTS). Most
high-level controllers generate a reference torque which is then send to the
underlying electrical drive system (generator+inverter) of the WTS to steer the
turbine/generator to its optimal operation point (depending on the wind speed).
The energy production heavily depends on the mechanical power (i.e. the product
of rotational speed and generator torque). However, since torque sensors in the
MW range are not available or extremely expensive, the torque controllers are
implemented as feedforward controllers and, therefore, are inherently sensitive
to parameter variations/uncertainties. Based on real wind data and a dynamical
WTS model, we discuss causes and impacts of non-ideal (feedforward) torque
control on the energy production and the gross earnings.
