Dynamic Modeling And Control Of Tethered Kite System For High Altitude Wind Power Generation

Kite power generation has the advantages of low cost,high efficiency and environmental protection,which is of great significance to the research of high altitude kite power generator and its power generation technology.In order to ensure the stable,economical and efficient operation of the high altitude kite power generation system,the methods of trajectory optimization and the design of the tracking control laws are the keys of the research in this field.In this thesis,the trajectory optimization and real-time tracking control of optimal reference trajectory are studied on a yo-yo type kite power generator.The main content includes the following aspects:1)In order to study the trajectory characteristics of the yo-yo device,space trajectory model and plane trajectory model are established respectively.The influence of the variation of the cable length on the kite trajectory is analyzed from three different conditions: the constant cable length,elongate with uniform speed and elongate with uniform acceleration.Through simulation,it is concluded that the kite power generation system is an open-loop unstable system.The flight trajectory and motion trend of the two models are consistent in the longitudinal plane,which verifies the accuracy of space trajectory modeling.2)In order to obtain the optimal reference trajectory of the high altitude kite power generation,the trajectory design and optimization of the kite open-loop and closed-loop trajectory are carried out respectively.The applicability of direct multiple shooting method(MSM)and Radau pseudospectral method(RPM)on the kite trajectory optimization is compared and analyzed from three aspects,namely,the computing time,the sensitivity to the initial value and the average power.It is concluded that RPM is more suitable for the calculation of optimal reference trajectory for the kite power system.3)In order to meet the requirements of real-time tracking control of reference trajectory,different trajectory tracking control strategies are designed for different kite devices.A cascade control strategy based on heading angle reference is designed for ship propulsion system.An explicit nonlinear model predictive controller(NMPC)is designed for tracking the specified reference trajectory of the tethered kite system.For the real time tracking case,another NMPC is applied to the on-line optimal trajectory tracking control problem of the high altitude kite generator.The real-time iteration scheme(RTI)is employed to reduce the numerical iterative calculation,which can shorten the calculation time of solving the optimal trajectory tracking control law and improve the real-time tracking performance while maintaining the trajectory tracking precision.And the robustness of the controller is verified by simulation.