Airborne wind energy systems flying optimal trajectories in turbulent wind using flight path tracking

Abstract

Airborne Wind Energy Systems (AWES) consist of tethered wings harvesting power from the wind. Rigid-wing (aircraft) pumping-mode AWES are considered here: they generate power during the reel-out phase and consume a fraction of this power during the reel-in phase. Those devices fly complex trajectories that require advanced control strategies. In the present work, we aim to develop a Large Eddy Simulation (LES) framework and improve the fidelity of existing models. The toolbox AWEbox is used for reference trajectories generation and control. Here the device is operated with a closed-loop control using a 6-DOF aircraft model. The aircraft is modeled using an actuator line (AL) for the wing, and the effects of the control surface are incorporated using their geometry and lift slope. The AL-based model is used to assess the robustness of the nonlinear model predictive controller against turbulence and to compare the performance between idealized conditions in AWEbox and turbulent wind conditions in the LES. The controller demonstrates high efficiency in tracking the reference trajectory and extracting the maximum power, even at high turbulence levels.