Nonlinear control of wind energy conversion system based on Control-Lyapunov function

Wind Energy Conversion Systems (WECS) require a control system which is able to maintain the stability of the power conditioning system under a wide range of operating conditions. Conventional PI-based dq-controllers are very difficult to stabilize, especially under a wide range of operating conditions and in the presence of un-modeled dynamics and uncertainties. This paper introduces a novel nonlinear controller based on Control-Lyapunov Functions (CLF) providing robust and reliable closed-loop control. The proposed CLF-based controller offers some attractive features for this particular application. The controller is able to track the reference point with less effort due to the fact that it does not remove the inherent self-stabilizing terms. Also, due to the inclusion of integral terms in the control system, the sensitivity to parameter variations is vastly reduced since the Lyapunov function compensates itself by accumulating errors. Lastly, the stability of the closed-loop is also guaranteed for all operating conditions. Experimental results show good performance of the closed-loop control system even under severe load changes.