Frequency Division-Coordinated Control Of Aerodynamic Load And Structural Vibration For Large-Scale Wind Turbine

Wind power industry is one of key strategic emerging industries in China.In order to reduce the levelized cost of wind power,the trend of growing large-scale of wind turbines is inevitable.It makes the fatigue loads and structural vibrations of blade-tower system more prominent.Reducing the fatigue loads of blade-tower system through aerodynamic load and structural vibration control method has been one of the key technologies for the sustainable development of wind power industry.The individual pitch control strategy is usually employed to adjust the aerodynamic load of blade,but it is difficult to alleviate high frequency fatigue load due to slow response speed.The trailing edge flap control strategy can effectively adjust the high frequency aerodynamic load,but there are problems such as insufficient research on aerodynamic characteristics and lack of effective simulation tools.The pitch control and trailing edge flap control could complement each other in effective frequency domain,but it is lack of effective coordinated control methods.In terms of tower structural vibration control,the TMD can effectively damp a specified vibration mode of tower,but its effective frequency range is narrow.The aerodynamic damping control can increase the aerodynamic damping and reduce the exciting effect of rotor act on tower.Its effective frequency range is relatively wide;but it is difficult to apply effectively damping effect for a specified vibration mode.The TMD and aerodynamic damping control could complement each other in effective frequency domain,but it is also lack of effective coordinated control methods.With consideration of above problems,the main works in this thiese are as follow:(1)The aerodynamic characteristics of trailing edge flap were investigated through wind tunnel test.The regulating law on aerodynamic parameters and the mechanism on flow field around airfoil by trailing edge flap were discussed.It could provide reference aerodynamic data for trailing edge flap control strategy.(2)The aerodynamic-structural-control simulation environment of wind turbine was established by FAST and Matlab/Simulink,and the trailing edge flap control module was integrated with the open source code FAST by secondary development.It could provide an effective simulation tool for trailing edge flap control strategy.(3)A pitch and trailing edge flap coordinated control method based on blade aerodynamic load frequency division strategy is designed.The aerodynamic load of blade is divided into a low frequency component and a high frequency component according to the rotor revolution frequency.Then the individual pitch control loop is mainly used to regulate the low frequency load component,and the trailing edge flap control loop is mainly used to regulate the high frequency load component.The simulation results show that this method could further reduce fatigue loads of blade than the existing method.(4)A TMD and aerodynamic damping coordinated control method based on tower vibration frequency division strategy is designed.The tower vibration is divided according to its natural frequency.Then the TMD control loop is mainly used to mitigate the first-order resonance of tower,and the aerodynamic damping control loop is mainly used to increase the aerodynamic damping to reduce the structural vibration.The simulation results show that this method can not only further mitigate the fatigue load of tower than the existing method,but also significantly further reduce the fatigue load of blade.The aerodynamic load and structural vibration control method proposed in this thesis can further reduce the fatigue load of the blade-tower system compared with the existing methods.It has a broad prospect for engineering application,which can broaden the design vision and provide theoretical reference for the research and development of large-scale wind turbines.