The Individual Pitch Control Of Floating Wind Turbine Based On Adaptive PI Control

With the increasing demand for energy, the renewable energy developing rapidly with each passing day. Offshore wind energy became relatively new and challenging area of research, because of its advantages are obvious, such as rich resources, less pollution of visual and noise, do not take up of land resources and suitable for large scale utilized. Floating wind turbine received considerable attention as it is suitable for the development of deep sea wind resources. However, due to the environment complexity, system parameters uncertainties, and the coupling effect of wind, wave and structure of floating wind turbine, the advanced control methods are urgently needed to maintain the stability of output power and reduce the load of the turbine. The individual pitch control(IPC) technology came into being. This method can reduce the loads of the turbine effectively, solve the uneven distribution of the loads on the blade in time domain and space domain, which are caused by external disturbances such as tower shadow effect, wind shear effect and so on, while maintain the output power stable. In addition, because of the complexity of the work environment and the inconvenience of maintenance and repair of the floating wind turbine, there has important theoretical significance and application value for the design of reliable and advanced fault tolerance control method. In this thesis, the problem of IPC of offshore floating wind turbine is studied in depth. The main work of this thesis are summarized as follows:(1) The wind energy conversion principle, wind speed characters, hydrodynamic characters, and the blade pitch control principle of the controller design for floating wind turbine are studied. By analyzing the impact of tower shadow effect and wind shear effect on wind speed, the control strategies of wind turbine working in different wind speed range are given. The impact and significance of the IPC for the stable operation of the system are indicated.(2) More accurate non-linear dynamic model of the system is established, based on the force analyze of each blade combined with dynamic load shedding problem of axial unbalanced aerodynamic loads. The uncertainty of the parameters and non-linear characteristics of the system are considered here.(3) Based on the dynamic load shedding problem of axial unbalanced aerodynamic loads, design robust adaptive PI tracing control method which is suitable for multi-input multi-output non-linear dynamic system. This method is used to control the blade pitch control system reliably, to achieve the ultimate uniformly bounded stable tracing control, while ensure the stability of the output power. Then a simulation analysis is made based on NREL FAST simulation platform. The 5 MW tension leg platform(TLP) floating wind turbine is used to verify the effectiveness of the method proposed.(4) The failure model of the system under the actuator fault and external disturbance is established. A robust adaptive fault tolerance PI tracing controller is designed to achieve the ultimate uniformly bounded stable tracing control of the system under actuator failure, keeping the stability of the system and improve the quality of the output power at the same time. The good control performance and effective fault tolerance ability of the method proposed is verified based on FAST simulation platform.