Optimal Torque Curve Tracking for Wind Turbine Generators Using Adaptive Extremum Seeking

Optimal torque control is a common technique for tracking the maximum power point of wind energy systems without direct wind measurements. However, it relies on the precise knowledge of the turbine's aerodynamic characteristics and air density. Since these parameters can significantly differ from their nominal value due to variable ambient conditions and turbine aging, suboptimal operation of the wind generator can occur. In this paper, a sensorless and model-free Adaptive Extremum Seeking (ES) parameter optimization is considered to track in real-time the optimal torque trajectory and achieve maximum wind energy harvesting. Differently from the conventional approach, adaptive ES is here used to drive the generator torque toward its optimal trajectory rather than to define a variable speed setpoint for the turbine. By doing so, maximum power operation can be reached with reduced oscillations of electrical power. Simulations on a 1.5 MW wind energy system are reported to demonstrate the effectiveness of the technique.