Study On Load Control Of Floating Offshore Wind Turbine

With the rapid development of offshore wind power technology and the increase of installed capacity,large scale floating wind turbine has gradually become the development trend and hot topic of research.The key components such as blade,drive train,tower,floating foundation and mooring system,they are all have flexible low-frequency modes,and the coupling vibration probability increases.The load is more complicated during the operation..In this paper,5MW Spar floating offshore wind turbine as the research object,in order to reduce the dynamic load of flexible components as the goal,the system dynamics model and load control strategy in-depth study.By adjusting the blade pitch angle and the generator torque to reduce the dynamic load,It is import to solve the problem of dynamic load control caused by uncertain factors such as floating offshore wind turbine can not be accurately modeled and external strong disturbance.Specific research work is reflected in the following aspects:The offshore wind turbine-floating foundation-mooring system dynamics model are established,water power,cabin swing,offshore wind farm wake effect on vibration and load are analysed.The analysis of the wind rotor imbalance load and flexible drive chain torsion and transverse load are the key.Based on this,the general scheme of load control for the floating wind turbine is determined.Facing to the imbalance load cused by offshore wind farm wake effect,and hydrodynamic cabin rocking vibration problem,the pitch multi-objective load control strategy is presented,in which H₂/H_∞ robust pitch control of wind turbine cabin output power stability and Cabin swing at the same time,so that the overall optimal is achieved.The problem of actuator saturation in the unbalanced load control of wind turbine is solved based on the multi step model prediction based on the prediction of the wake center.Foucs on the uncertainty of the dynamic parameters of the flexible transmission system,a kind of double loop drive load control strategy is presented in the thesis.The inner loop is used to adjust the dynamic quality of the controlled object,and the outer loop ensure the robust stability and robust performance of the system.A robust controller order reduction method based on Hankel norm and gap metric is proposed to solve the controller reduction problem.The Calman filter state estimation is used to control the torsional load of the drive train,so that the equivalent generator speed can be traced,the displacement difference between the two ends of the low speed shaft can be reduced,and the dynamic torsional load of the drive train is reduced.In order to verify the dynamic load control strategy proposed in this thesis,a kind of tese bench based on the controller hardware is built.The result shows that the load control method proposed in this paper can significantly reduce the load of the wind turbine and the transmission system.