Optimal Altitude Control of an Integrated Airborne Wind Energy System with Globalized Lyapunov-based Switched Extremum Seeking

Airborne wind energy (AWE) systems replace the tower and foundation of contemporary wind turbines with tethers and a lifting body. This enables AWE systems to adjust their operating altitudes to deliver the greatest amount of net energy possible. However, determining the optimal operating altitude requires knowledge of the wind speed vs. altitude (wind shear) profile, leading to a tradeoff between exploration and exploitation. In this work, we consider an integrated AWE-battery-generator system in which it is possible to explore the domain of admissible altitudes during periods of low load demand and exploit the best altitude at other times. Specifically, we propose and evaluate four candidate hierarchical structures, based on a globalized Lyapunov-based switched extremum seeking (G-LSES) control structure, for control of the integrated system. We present simulation-based results that are based on actual wind speed and load demand data.