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Summary This paper investigates the use of a passive tuned mass‐damper‐inerter (TMDI) for vibration control of spar‐type floating offshore wind turbine towers. The TMDI is a relatively new concept as a passive vibration control device. The configuration consists of an “inerter” attached to the tuned mass, parallel to the spring and damper of a classical tuned mass damper (TMD). The inerter provides a mass amplification effect on the classical TMD. The presence of the inerter virtually increases the mass of the damper leading to greater vibration control capabilities. This enables one to achieve improved vibration control using a lighter damper. Using a lightweight damper is particularly important for an offshore wind turbine because increasing mass on top of the tower can destabilize the overall system and increase tower vibrations, as demonstrated in this paper. The development of a passive TMDI for an offshore wind turbine tower has been proposed in detail in this work. Numerical simulations have been performed and results are presented demonstrating the impressive vibration control capabilities of this new device under various stochastic wind‐wave loads. It has been shown that the TMDI has considerable advantages over the classical TMD, achieving impressive response reductions with reductions in the stroke of the tuned mass. The TMDI has been shown to be a promising candidate for replacing the classical TMD for offshore wind applications.

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Summary Present study aims to address the design of smart vibration control scheme for horizontal axis wind turbine tower using magneto‐rheological tuned liquid column damper. With this in view, a reduced order model of the blade‐tower system is used, considering centrifugal stiffening and gravitational effects that lead to time‐dependent dynamic stiffness matrix. Aerodynamic load on the blades is modeled using blade element momentum theory. Semiactive control law in linear quadratic regulator framework is developed to mitigate the along‐wind vibration of the tower. To implement the control law, multiblade coordinate transformation is adopted that converts the system matrices in the nonrotating framework to tackle its time dependency. The performance of the proposed control algorithm is demonstrated using numerical simulations with and without controller. Clipped optimality of the control force is imposed to keep the parameters of magneto‐rheological tuned liquid column damper in the feasible range. Finally, sensitivity analysis is carried out to demonstrate the performance envelope of the proposed control algorithm for different operational scenario. Results presented in this paper clearly demonstrate that the proposed algorithm can be employed for effective along‐wind vibration control of large HWAT tower.

This paper proposes a new strategy for individual blade pitch control to regulate power production while simultaneously alleviating structural loads on spar-type floating offshore wind turbines. Individual blade pitch control types of algorithms for offshore wind turbines are sparse in the literature though there are expected benefits from experience on such types of controllers for onshore wind turbines. Wind turbine blade pitch actuators are primarily used to maintain rated power production at above-rated wind speeds and therefore, control algorithms are usually developed only to regulate power production. The scope of reducing structural loads using individual pitch control has been proved to be very promising over the last decade and numerous individual pitch control algorithms have been proposed by researchers. However, reduction in structural loads often results in a degradation in power production and regulation. Furthermore, improving power regulation often has a detrimental effect on the floating platform motion. In this paper, a new control strategy is proposed to achieve the two competing objectives. The proposed controller combines a low authority Linear Quadratic (LQ) controller with an integral action to reduce the 1P (once per revolution) aerodynamic loads while regulating power production using the same pitch actuators that are traditionally used only to optimize power production. The proposed controller is compared against the baseline controller used by state-of-the-art wind turbine simulator FAST using a high fidelity aeroelastic offshore wind turbine model. Numerical results show that the proposed controller offers improved performance in optimizing power production and reducing wind turbine and platform loads compared to the baseline controller over an envelope of windwave loading environment.Index Terms-Floating offshore wind turbines, individual blade pitch control, regulate power production, alleviate aerodynamic loads.

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