Simulating Feedback Linearization control of wind turbines using high-order models



As wind turbines are becoming larger, wind turbine control must now encompass load control objectives as well as power and speed control to achieve a low cost of energy. Due to the inherent non-linearities in a wind turbine system, the use of non-linear model-based controllers has the potential to increase control performance. A non-linear feedback linearization controller with an Extended Kalman Filter is successfully used to control a FAST model of the controls advanced research turbine with active blade, tower and drive-train dynamics in above rated wind conditions. The controller exhibits reductions in low speed shaft fatigue damage equivalent loads, power regulation and speed regulation when compared to a Gain Scheduled Proportional Integral controller, designed for speed regulation alone. The feedback linearization controller shows better rotor speed regulation than a Linear Quadratic Regulator (LQR) at close to rated wind speeds, but poorer rotor speed regulation at higher wind speeds. This is due to modeling inaccuracies and the addition of unmodeled dynamics during simulation. Similar performance between the feedback linearization controller and the LQR in reducing drive-train fatigue damage and power regulation is observed. Improvements in control performance may be achieved through increasing the accuracy of the non-linear model used for controller design. Copyright © 2009 John Wiley & Sons, Ltd.