Modeling and control design for a prototype lighter-than-air wind energy system

This paper presents the hardware configuration, modeling, and control design for a lighter-than-air wind power system being pioneered by Altaeros Energies. This unique design features a horizontal-axis turbine that is elevated to high altitudes via a buoyant shroud, which is tethered to a ground-based platform. Because the system is based on proven aerostat technology and is designed to remain substantially stationary, it circumvents many of the controls challenges faced by so-called aerodynamic (e.g. kite-based) wind energy systems. However, the need to generate energy introduces pointing, efficiency, and autonomy requirements that are not faced by conventional aerostats, thereby requiring a careful model-based control design. In this paper, we first provide a detailed description of the system and controls hardware for the Altaeros 2.4 kW proof-of-concept prototype. We provide a detailed 3-dimensional dynamic model for the Altaeros system, which is used in the design of a fully autonomous control system. This paper details the control system design and shows simulation results that substantiate the system's performance.