Wind turbine tower dynamic load is related to the fatigue and reliability of the structure. This paper deals with the problem of tower vibration control using specially designed and built numerical and laboratory model. The regarded wind turbine tower-nacelle model consists of vertically arranged stiff rod (representing the tower), and a stiff body fixed at its top representing nacelle assembly that is equipped with horizontally aligned tuned vibration absorber (TVA) with magnetorheological (MR) damper. To model tower-nacelle dynamics, Comsol Multiphysics finite element method environment was used. For time and frequency domain numerical analyses (including first and second bending modes of vibration) of system with TVA and MR damper models, MATLAB/Simulink environment was used with Comsol Multiphysics tower-nacelle model embedded. Force excitation sources applied horizontally to the nacelle, and to the tower itself were both considered. The MR damper real-time control algorithms, including ground hook control and its modification, sliding mode control, linear and nonlinear (cubic and square root) damping, and adaptive solutions are compared to the open-loop case with various constant MR damper input current values and system without MRTVA (i.e. MRTVA in ‘locked’ state). Comprehensive numerical analyses results are presented along with Vensys 82 full-scale tower-nacelle model validation. Finally, preliminary results of laboratory tests are included.

This work covers selected control issues, including refined force tracking algorithm formulation, concerning the wind turbine tower-nacelle laboratory model equipped with a magnetorheological damper based tuned vibration absorber. The objective of the current research is a development and experimental implementation of the control algorithm that couples basic adaptive stiffness solution with stock magnetorheological damper force tracking concept to obtain a quality tower vibration reduction system. The experiments were conducted assuming monoharmonic, horizontal excitation applied to the assembly modelling the nacelle. The frequency range comprised the neighbourhood of the first bending mode of the tower-nacelle system. The results proved the effectiveness of the adopted algorithm referring to other high-performance solutions.

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The paper addresses analytical, numerical and experimental aspects of the design of magnetorheological (MR) fluid valve. Magnetic flux in valve’s cross-section is analysed with the help of finite element method (FEM) software. Based on the magnetic field intensity distribution within valve’s MR fluid annular gap, simulation model of the shock absorber equipped with newly designed MR valves is developed. Prototypes of MR valve are built and embedded in the stationary barrier of the rotary shock absorber, instead of standard, passive check valves. Simulation and preliminary experimental results comprising resistance force values as a function of angular displacement and angular velocity are presented.

This paper presents an implementation of a nonlinear optimal-based wind turbine tower vibration control method. An NREL 5.0 MW tower-nacelle model equipped with a hybrid tuned vibration absorber (HTVA) is analysed against the model equipped with a magnetorheological TVA (MRTVA). For control purposes, a 3 kN active actuator in parallel with a passive TVA is used in the HTVA system, while an MR damper is built in the MRTVA instead of a viscous damper, as in a standard TVA. All actuator force constraints are embedded in the implemented nonlinear control techniques. By employing the Pontryagin maximum principle, the nonlinear optimal HTVA control proposition was derived along with its simplified revisions to avoid a high computational load during real-time control. The advantage of HTVA over MRTVA in vibration attenuation is evident within the first tower bending frequency neighbourhood, with HTVA also requiring less working space. Using the appropriate optimisation fields enabled an 8-fold reduction of HTVA energy demand along with a (further) 29% reduction of its working space while maintaining a significant advantage of HTVA over the passive TVA. The obtained results are encouraging for the assumed mass ratio and actuator force limitations, proving the effectiveness and validity of the proposed approaches.