Ensuring maximum energy capture by wind turbines during below rated operation

The operational strategy in below rated operation of a variable speed wind turbine is frequently chosen to maximise the energy capture. To do so the operating state of the wind turbine is caused to track the maximum aerodynamic efficiency curve, the so-called Cp-max curve. Whether it does so accurately, depends on the wind turbine controller. It is sometimes claimed that the energy capture can be increased by better design of this controller. The purpose of this paper is to examine this claim. The results suggest that the energy capture is very weakly dependent on the control algorithm. There is more dependence on the choice of control strategy but even here the potential gains are limited.