Development of semi-active vibration control strategy for horizontal axis wind turbine tower using multiple magneto-rheological tuned liquid column dampers

Vibration control is an essential component of safe and sustained operation of modern large wind turbine towers. As the blade-tower assembly offers time-dependent system matrices that periodically evolves with the rotational speed of the turbine, control theories (e.g. linear quadratic Gaussian) can not be directly adopted in this case. With this in view, the present study aims to develop a semi-active strategy using multiple magneto-rheological tuned liquid column dampers (MR-TLCDs) to mitigate excessive vibration of the horizontal axis wind turbine towers. The design of the controller is achieved by the multi-blade coordinate transformation that converts the system matrices into a non-rotating framework followed by time averaging to enable the application of linear control law. Parameters of the non-linear MR-TLCDs are optimally tuned to dissipate maximum energy. Aerodynamic loads are evaluated using modified blade element momentum theory. The performance of the proposed control strategy is assessed against different wind speeds. Clipping laws are employed to keep the semi-active control force in the feasible range. Two different clipping laws are compared in this paper. Finally, sensitivity analysis is carried out to demonstrate the performance envelope and robustness of the proposed controller. (C) 2019 Elsevier Ltd. All rights reserved.