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Details of Grant 

EPSRC Reference: EP/R015120/1
Title: Passive vibration control of a floating hydrostatic transmission wind turbine and theoretical extensions
Principal Investigator: Zhao, Professor X
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Friedrich-Alexander Univ of Erlangen FAU FTI Consulting Imperial College London
Institute of Systems Science University of Oxford University of Twente
Department: Sch of Engineering
Organisation: University of Warwick
Scheme: First Grant - Revised 2009
Starts: 01 June 2018 Ends: 30 June 2020 Value (£): 101,062
EPSRC Research Topic Classifications:
Control Engineering
EPSRC Industrial Sector Classifications:
Related Grants:
Panel History:
Panel DatePanel NameOutcome
06 Dec 2017 Engineering Prioritisation Panel Meeting 6 December 2017 Announced
Summary on Grant Application Form
Short summary:

This proposal will develop novel passive damping technology to dampen the vibrations of the floating platform of a new type of wind turbine employing the hydrostatic transmission drivetrain, and develop a stability theory for coupled infinite-dimensional systems with nonlinear feedback.


In order to capture the highest quality wind resources, wind turbines are getting deployed further offshore with the floating wind turbine technology. However the floating wind turbines face more severe challenges from weather and wave conditions than their fixed-bottom counterparts. The motions of the floating platform not only cause large fluctuations in the rotor speed and generator power, but also cause considerable load variations on the tower base. Known vibration reduction methods are by torque control and by blade pitch control. But these methods are effective at the expense of interfering with the power generation and the latter will increase blade pitch actuator usage. Structural control, e.g., using tuned mass damper (TMD) or tuned liquid column damper (TLCD), might offer a good alternative solution. They are free from electrical faults, but a big disadvantage of TMD/TLCD type of dampers is that they have a large mass and/or a large amount of liquid, leading to substantial extra weight, this could be prevented if they made use of existing turbine components. However, practical considerations have shown that existing components cannot be used, so this is not a realistic solution for conventional wind turbines. A new type of wind turbine called hydrostatic transmission wind turbine (HSTWT), could provide the suitable mass and liquid component.

Control Application:

The proposed project will investigate how to make use of the hydraulic reservoir of the floating barge mounted HSTWT to dampen the vibrations of the floating platform, by acting as a novel damper. This will simply give the reservoir a dual function with very small extra costs. During the project we will use existing simulation model of the floating wind turbines developed by the National Renewable Energy Laboratory for detailed simulation analysis. This model will be modified to include the HST drivetrain, coupled dynamics of the barge-reservoir system, and pitch and torque controllers. The optimal damper design will be based on two simple models obtained from the above simulation model through system identification, and Particle Swarm Optimization algorithm.

Control theory:

The above tower (including the barge) - damper system is the interconnection of two passive systems. However this does not automatically lead to stability. We abstract this problem as stability theory and look even further: assuming the tower is flexible, which is described by partial differential equations, so that it is an infinite-dimensional system. When two systems influence each other in both directions, they are known as a coupled system. Coupled systems in engineering often consist of an infinite-dimension system interacting with a finite-dimensional system, i.e., a system that can be described by ordinary differential equations. Such coupled systems have been recently the topic of intense research in the linear case. The case of a nonlinear finite-dimensional system is open and challenging. Thus it will be very interesting to develop a stability theory for the interconnection of a passive linear infinite-dimensional system and a passive nonlinear finite-dimensional system. The equations of the coupled system can be rewritten as an abstract second order differential equation in a Hilbert space, with a nonlinear damping term. We aim to investigate the stability properties of such systems using monotone operator theory and Lyapunov functions.

This work requires an in-depth understanding of fluid mechanics, structural dynamics and control theory and engineering, all of which are well represented in the PI's multi-disciplinary background.
Key Findings
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Organisation Website: http://www.warwick.ac.uk