Wei, Xing (2020) Vibration suppression of large and flexible offshore wind turbine. PhD thesis, University of Warwick.

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Abstract

Passive control schemes are proposed to suppress the blade flapwise vibration of offshore wind turbine and platform rotational motions of floating wind turbine.

Firstly, the mechanical networks are designed to control the trailing edge flaps passively as the flap dynamics has been incorporated into the National Renewable Energy Laboratory (NREL) 5MW offshore wind turbine model. The optimal parameters of mechanical networks are optimised by H2 and H∞ optimisation schemes for the given forms of the admittance function of mechanical networks. We run the simulation on full wind turbine model with the mechanical network installed on each blade. It demonstrates good performance on suppressing the blade flapwise vibration with flap angles in a reasonable range.

Secondly, we implement the magnetorheological (MR) damper, on a 20MW wind turbine model to suppress the blade flapwise vibration. The 20MW wind turbine model was obtained by upscaling the NREL 5MW offshore wind turbine model presented in Chapter 2. Then, a simple and concise model of MR damper is adopted for optimisation and simulation. The five parameters of the MR damper model are optimised by MATLAB command FMINCON to minimise the blade root bending moment (RBM). A mechanical network is also designed for performance comparison. The simulation results show that MR damper outperforms the mechanical network on blade out-of-plane vibration suppression.

Thirdly, we further develop the bidirectional tuned liquid column damper (BTLCD) into the bidirectional tuned liquid column mass damper (BTLCMD) to mitigate the barge pitch and roll motions. The parameters of BTLCMD are optimised on two simplified models describing the pitch and roll responses of the turbine-reservoir system. The simulation results indicate that the BTLCMD achieve greater reduction on barge rotations than BTLCD does. The BTLCMD also reduces more tower base fatigue load as it combines the advantages of the tuned mass damper (TMD) and the BTLCD.

Item Type:	Thesis (PhD)
Subjects:	T Technology > TH Building construction T Technology > TJ Mechanical engineering and machinery
Library of Congress Subject Headings (LCSH):	Wind turbines -- Vibration, Wind turbines -- Design and construction, Offshore wind power plants, Tuned mass dampers
Official Date:	July 2020
Dates:	Date Event July 2020 UNSPECIFIED
Institution:	University of Warwick
Theses Department:	School of Engineering
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Zhao, Xiaowei
Format of File:	pdf
Extent:	xvi, 117 leaves : illustrations (some colour)
Language:	eng

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