The Library
Modelling and load alleviation control of large and flexible wind turbines with smart rotors
Tools
Li, Juan (2021) Modelling and load alleviation control of large and flexible wind turbines with smart rotors. PhD thesis, University of Warwick.
PDF
WRAP_Theses_Li_2021.pdf - Unspecified Version Embargoed item. Restricted access to Repository staff only until 7 June 2024. Contact author directly, specifying your specific needs. - Requires a PDF viewer. Download (11Mb) |
Official URL: http://webcat.warwick.ac.uk/record=b3851681
Abstract
The present work is devoted to developing aeroservoelastic wind turbine models and alleviating the dynamic load on the wind turbine blade via controllable aps (we also call them smart rotors) under an advanced model-free adaptive control (MFAC) algorithm.
In the first stage, an aeroservoelastic wind turbine model is developed, which is the combination of a structural model for the tower and blades represented by geometrically non-linear composite beams, and an aerodynamic model for the rotors using an unsteady strip-theory airfoil model. This simplified model is used for a preliminary study of the MFAC control design. As we know that in wind energy applications, specifically large wind turbine rotors (above 5MW) operate in a challenging environment in terms of complex turbulent inflow conditions and high flexibility of the turbine structure, where unsteady effects and flow separation can significantly affect the loads, the conventional linear attached ow models could not realistically capture the aerodynamics of the turbine blades in this scenario. On the other hand, the linear aerodynamic model could cope with small trailing edge aps with limited deflection angles but not big aps with big deflection angles. Thus, in the second stage, a new aerodynamic model based on the vortex panel method (VPM) is proposed in this work to represent the aerodynamics of deforming and dynamic blade sections - airfoils - in a wide range of ow conditions, taking into account both statistic attached flow conditions and unsteady separated ow conditions with dynamic stall phenomenon. By removing some of its limitations, the updated model contributes to a higher fidelity in the modeling of large and flexible wind turbines with smart rotors without adding enormous computational costs, which is still suitable for control designs of the system. It has been implemented in an aerodynamic xvi tool for the modeling of wind turbines. And proper validation has been carried out to assess the validity of the new model. Combined with a vortex force map (VFM) and vortex moment map (VMM) method, the new model is also used to analyze the aerodynamic characteristics of the blade sections under the effect of the separating vortex. From the control perspective, the increasing size increases the susceptibility of a wind turbine to gravitational effects and to wind speed variations across the rotor disk, which in turn increases the difficulty in the control design for reducing the fluctuating loads. This work seeks new solutions for load alleviation control strategies to prolong the fatigue life of wind turbines. Specifically, this work investigates the dynamic load alleviation in large and flexible horizontal axis wind turbine rotors with trailing edge aps (TEFs), actuated through a novel proportional-derivative model-free adaptive control (PD-MFAC) system. Based on the two newly developed aeroservoelastic wind turbine models above, three independent model-free controllers are designed to actuate the TEFs mounted on three blades, using the blade root-bending moment (RBM) as the control input and the ap deflection angles as the control output. Comparison is given by a traditional H-infinity (H1) reference controller and/or a classical Gain-scheduled proportional-integral (GS-PI) controller. It is shown that the designed PD-MFAC ap controller exhibits marked reductions in RBM and blade tip deflection (BTD), in the presence of inflow turbulence. Moreover, the PD-MFAC ap controller is shown to provide more effective load alleviation performance than the H1 ap controller or the GS-PI ap controllers. The updated nonlinear wind turbine model and the novel PD-MFAC design on a 5MW NREL reference wind turbine with smart rotors push the frontier of the state of the art of wind turbine load alleviation study.
Item Type: | Thesis (PhD) | ||||
---|---|---|---|---|---|
Subjects: | T Technology > TA Engineering (General). Civil engineering (General) T Technology > TJ Mechanical engineering and machinery T Technology > TL Motor vehicles. Aeronautics. Astronautics |
||||
Library of Congress Subject Headings (LCSH): | Wind turbines, Wind turbines -- Rotors, Aeroservoelasticity, Aerofoils, Wind-pressure | ||||
Official Date: | June 2021 | ||||
Dates: |
|
||||
Institution: | University of Warwick | ||||
Theses Department: | School of Engineering | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Zhao, Xiaowei | ||||
Format of File: | |||||
Extent: | xx, 123 leaves : illustrations | ||||
Language: | eng |
Request changes or add full text files to a record
Repository staff actions (login required)
View Item |