Flight control of tethered kites in autonomous pumping cycles for airborne wind energy

摘要

Energy harvesting based on tethered kites benefits from exploiting higherwind speeds at higher altitudes. The setup considered in this paper is based ona pumping cycle. It generates energy by winching out at high tether forces,driving an electrical generator while flying crosswind. Then it winches in at astationary neutral position, thus leaving a net amount of generated energy. The focus of this paper is put on the flight control design, which implementsan accurate direction control towards target points and allows for a flightwith an eight-down pattern. An extended overview on the control systemapproach, as well as details of each element of the flight controller, arepresented. The control architecture is motivated by a simple, yet comprehensivemodel for the kite dynamics. In addition, winch strategies based on an optimization scheme are presented.In order to demonstrate the real world functionality of the presentedalgorithms, flight data from a fully automated pumping-cycle operation of asmall-scale prototype are given. The setup is based on a 30m$^2$ kite linked toa ground-based 50kW electrical motor/generator by a single line.