Adaptive control of flow over wind turbine blade

Aeroelastic flutter instability has been an issue with the trend of high-capacity wind turbine manufacture. Flutter occurs when large blades produce bending and twisting, which can affect the aerodynamic forces by changing angle of attack and make structural damping insufficient to dampen the vibrations induced by aerodynamic loads. The flutter problem has increased the need for active flow control. This work explores the opportunities for utilizing aerodynamic modeling, modal analysis, advanced controllers and effective actuators in blade flutter suppression.;An aeroelastic model of rotating blades was developed to identify flutter speed, examine control method and test various actuators. The structural model provides a pitch and plunge system with constant wind velocity. Equations of dynamic motion are expressed mathematically, simulated and implemented in Matlab/Simulink. Beddoes-Leishman(B-L) model, an aerodynamic stall model initially developed for helicopter analysis, offers periodic, time-varying, aerodynamic load estimation on rotating blades. Linearization of the B-L model produces state-space equations of the aeroelastic system with periodic time-varying coefficients for control design and stability analysis. Floquet theory is used to indicate modal properties, flutter speed and control performance.;Two different actuators with diverse aerodynamic load issues were investigated in the Adaptive Control application: A trailing-edge flap and microtabs. A stationary blade using Microtabs was first studied with steady aerodynamic load for flutter vibration control. Then, a sinusoidal function was adopted to imitate unsteady aerodynamic load with both trailing-edge flap and Microtabs to generate control forces. Flutter suppression was then examined with both actuators based on precise modeling of the Beddoes-Leishman dynamic stall model. Robustness and effectiveness of Adaptive Controller are shown by good simulation results of all aerodynamic loads and actuation cases. Actuators also perform efficient and effective actuation.;For the stability analysis, Adaptive Stability Theorem is given to conclude the feasibility of adaptive controller and its stability in periodic time-varying system(PTS). This theorem is proved theoretically in detail and also illustrated by proposed aeroelastic system cases.