UDE-based robust control of variable-speed wind turbines

In this paper, the UDE (uncertainty and disturbance estimator)-based robust control is investigated for a two-bladed horizontal axis variable speed wind turbine in the presence of model uncertainties and external disturbances. The UDE algorithm is based on the assumption that a signal can be approximated and estimated by using a filter with the appropriate bandwidth. The most important features of the approach are that (i) the employment of UDE makes it possible to estimate the lumped uncertain term which is non-singular with respect to the system state !r and bounded with respect to the time t; and (ii) it does not require any knowledge (e.g., bounds) about the uncertainties and disturbances, except the information about the bandwidth, during the design process. The asymptotic stability of the closed-loop system is rigorously established and the rotor speed asymptotically tracks a reference speed that maximizes the energy captured by adjusting the armature current of the DC generator. The effectiveness of the proposed approach is demonstrated through simulation studies.