Nonlinear MPC of kites under varying wind conditions for a new class of large-scale wind power generators

In this paper we investigate nonlinear model predictive control (NMPC) for control of power generating kites under changing wind conditions. We derive a realistic nonlinear model for a kite and compute energy optimal loops for different wind speeds. We formulate the optimal control problem used by NMPC with an adaptive periodic reference orbit. Under changing wind conditions we use the corresponding energy optimal orbit as reference. To assure that the references do not unnecessarily depend on the wind conditions, we added extra constraints. We solve this NMPC problem numerically with the real-time iteration scheme using direct multiple shooting. Finally, we present numerical simulations which show how this approach can handle even large disturbances of the wind direction and speed with negligible energy losses. Copyright (c) 2007 John Wiley & Sons, Ltd.