High-order observers-based LQ control scheme for wind speed and uncertainties estimation in WECSs

Tip speed ratio control is a popular method in wind energy conversion systems in order to capture the maximum power. This method, however, requires wind speed information, which is difficult in practice to accurately measure it. Therefore, estimation methods are usually applied, where a high-precision estimate leads to a high-efficient system. Based on the fact that the wind speed varies in a random way, this paper proposes a generalized high-order observer to estimate the aerodynamic torque and the wind speed accordingly. This observer algorithm releases the assumption that the wind speed should be slowly varying, which is required in previous observer designs. Moreover, two other generalized high-order observers are also applied to estimate the uncertainties, which depend on state variables and cannot be considered as slow-varying disturbances. Using the outputs of these observers, a robust high-performance optimal control system is developed for the rotor speed to keep the optimal tip speed ratio. The stability analysis of the designed control system is fully presented. The effectiveness of the proposed technique is validated via simulation studies.