Semi-active vibration control of a semi-submersible offshore wind turbine using a tuned liquid multi-column damper
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RESEARCH ARTICLE
Semi‑active vibration control of a semi‑submersible offshore wind turbine using a tuned liquid multi‑column damper Alireza Fath1 · Ehsan Azadi Yazdi1 · Mohammad Eghtesad1 Received: 29 November 2019 / Accepted: 18 July 2020 © Springer Nature Switzerland AG 2020
Abstract In this paper, a control system is proposed for the vibration suppression of a semi-submersible offshore wind turbine equipped with a tuned liquid multi-column damper (TLMCD). The TLMCD consists of three columns of liquid integrated into the superstructure of the semi-submersible platform. To improve the vibration suppression performance of the TLMCD, unlike previous works, the TLMCD is operated in a semi-active mode by introducing three flow control valves that allow liquid to transfer between columns. Since the rotor dynamics may greatly affect the platform vibrations, it has been included in the derived nonlinear dynamic model. In the proposed control loop, the closed-loop performance objectives of platform stabilization and rotor speed regulation are accomplished by two distinct controllers. For the platform stabilization purpose, three controller design methods of displacement-based ground-hook, velocity-based ground-hook, and bang–bang are investigated. Meanwhile, to achieve the rated rotor speed, two methods of the H∞ and gain-scheduling control schemes are attempted. The closed-loop performance is investigated through numerical simulations. Realistic wind profiles along with a wave disturbance are implemented in the numerical simulations. The results show that the gain-scheduling control scheme for the rotor speed regulation and the velocity-based ground-hook method for the platform stabilization outperform other methods. Furthermore, to study the effect of the design parameters of the TLMCD on the closed-loop performance, several cases with different values of the design parameters are examined and compared. Keywords Semi-submersible offshore wind turbine · Tuned liquid column damper · Gain-scheduled control · VBG control · DBG control · Bang–bang control
1 Introduction Nowadays, with the crisis of global warming, renewable energy has become the primary focus of the energy production industry. Wind energy reached nearly 487 GW capacity in 2016 (Sawin et al. 2017). Despite the benefits of the onshore wind turbines, the high and steady wind speed at sea motivates the use of offshore wind turbines (OWT) (Musial and Butterfield 2004). In deep water, the mechanisms that stabilize the platform of offshore turbines * Ehsan Azadi Yazdi [email protected] Alireza Fath [email protected] Mohammad Eghtesad [email protected] 1
School of Mechanical Engineering, Shiraz University, Molasadra Street, Shiraz, Iran
are: ballast, mooring lines, and buoyancy (Butterfield et al. 2007). The ballast-type platforms (e.g., spar-buoy platform) introduce extra weights to locate the center of mass of the OWT below its center of buoyancy. On the other hand, the mooring lines mechanism consists of a set of pre-tensioned cables u
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