| Wei, Nathaniel James (2023) Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/d9wh-pj98. Wind energy is poised to play a considerable role in the global transition to clean-energy technologies within the next few decades. Modern wind turbines, like aircraft and other aerodynamic structures, are typically designed with the assumption that the flows they encounter will be uniform and steady. However, atmospheric flows are highly unsteady, and systems operating within them must contend with gust disturbances that can lead to performance losses and structural damage. Therefore, the next generation of wind-energy systems requires physics-informed design principles that effectively account for and even leverage these unsteady flow phenomena for enhanced power generation, robustness, and operational longevity. Accordingly, this work details experimental and analytical efforts to characterize unsteady aerodynamics in wind-turbine contexts. First, the effects of unsteady streamwise motion on turbine performance are studied, as recent work has suggested that these dynamics may enable time-averaged efficiencies that exceed the steady-flow Betz limit on turbine efficiency. The power production of and flow around a periodically surging wind turbine are thus investigated using wind-tunnel experiments, which suggest that turbines in these flow conditions could leverage unsteady surge motions for power-extraction gains of up to 6.4% over the stationary case. Linearized and nonlinear dynamical models of the response of the turbine to these time-varying flows are derived and validated against the experimental data. These models are also coupled with a potential-flow model of the upstream induction zone of the turbine in order to predict temporal variations in the flow velocities and pressures in this region. Unsteady contributions to the time-averaged efficiency are also considered through theoretical potential-flow derivations. Additionally, a novel three-dimensional particle-tracking velocimetry approach using artificial snow as seeding particles is deployed to obtain volumetric flow measurements in the wakes of full-scale vertical-axis wind turbines in field conditions. These measurements yield insights into the effects of unsteady vortex dynamics on the structure of the near wake, with implications for the performance of turbines in wind-farm arrays. These investigations provide the analytical and experimental foundations for future studies of unsteady atmospheric flows, and will lead to the development of principles and techniques for wind-farm siting, control, and optimization. | Item Type: | Thesis (Dissertation (Ph.D.)) |
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| Subject Keywords: | Aerodynamics, experimental fluid mechanics, unsteady flows, renewable energy, wind turbine, floating offshore wind turbine, vertical-axis wind turbine |
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| Degree Grantor: | California Institute of Technology |
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| Division: | Engineering and Applied Science |
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| Major Option: | Aeronautics |
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| Awards: | Demetriades-Tsafka-Kokkalis Prize in Environmentally Benign Renewable Energy Sources or Related Fields, 2023.
Hans G. Hornung Prize, 2023.
Richard Bruce Chapman Memorial Award, 2023. |
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| Thesis Availability: | Public (worldwide access) |
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| Research Advisor(s): | |
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| Group: | GALCIT |
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| Thesis Committee: | |
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| Defense Date: | 26 May 2023 |
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| Funders: | | Funding Agency | Grant Number |
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| NSF Graduate Research Fellowship | UNSPECIFIED | | Stanford Graduate Fellowship | UNSPECIFIED | | NSF | CBET-2038071 | | Caltech Center for Autonomous Systems and Technologies | UNSPECIFIED | | Gordon and Betty Moore Foundation | 2645 | | NSF | FD-1802476 | | Stanford University TomKat Center for Energy Sustainability | UNSPECIFIED |
| URL | URL Type | Description |
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| | DOI | Article adapted for Ch. 2 (published in the Journal of Renewable and Sustainable Energy) | | | arXiv | Article adapted for Ch. 3 (accepted for publication in the Journal of Fluid Mechanics) | | | DOI | Article adapted for Ch. 4 (published in the Journal of Fluid Mechanics) |
| Author | ORCID |
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| Wei, Nathaniel James | |
 Thesis FilesRepository Staff Only: item control page Modelling and control of wind turbines with aeroelastically tailoring bladesDownloadable content.  - Hussain, Rohaida Binti
- Strathclyde Thesis Copyright
- University of Strathclyde
- Doctoral (Postgraduate)
- Doctor of Philosophy (PhD)
- Department of Electronic and Electrical Engineering
- Centre for Doctoral Training in Wind and Marine Energy Systems and Structures
- The increased size of wind turbines (WTs) improves power generation efficiency but also imposes larger loading effects on the turbine system. A wind turbine with an aeroelastic tailoring blade (ATB) is proposed to alleviate the loading effect in wind turbine blades. A turbine with ATB is designed to respond to the incoming wind forces by deforming the shape of the blade and then reforming to its initial formation. The blade is manufactured with composite materials, incorporated with pre-twist angle and bend twist coupling (BTC) characteristics. Wind turbines with ATB are a new development that needs a better understanding of their operational performance and their potential when properly controlled. This PhD project aims to investigate the modelling and control of industrial-scale ATB WTs and assess the control performance with systematic studies. The thesis work includes two connected parts, model development, and control system design. A set of models has been developed for system analysis and controller design. To start with, a baseline model is revisited that covers key modelling elements of a 5MW standard HAWT wind turbine. This model is indexed as Model 0 in this thesis, it is the basis for other ATB WTs. To characterise ATB features, firstly the static BTC distribution is added to the turbine aerodynamics to account for the blade’s pre-bend-twist design. This static ATB model is integrated to the baseline model giving the fullnonlinear turbine model, called Model 1, which will be used for the gain-schedulingbaseline controller. Next, the ATB dynamics is approximated by a spring dampermodel to describe the blade structural dynamic response to wind speed variations.The developed turbine model combining the static ATB and dynamic ATB is calledModel 2, based on which a linearised and discretised state-space model is developed for adaptive model predictive control (MPC). Additionally, a composite ATB model is established, in which the power coefficient values are generated from physical laboratory experiments for a composite materials blade. This model is referred to as Model 3, will also be used for adaptive MPC. Two controllers are investigated for the above-rated ATB WT operational control. The first controller is the gain scheduling baseline controller developed by the Wind Energy and Control Centre, initially for full envelope WT control of a standard machine without ATB. This baseline controller is redeveloped for the ATB WT using Model 1. The second controller is the adaptive MPC proposed and developed in this thesis work, which includes a general predictive controller enhanced by the use of a Kalman filterand online model update. This adaptive MPC is applied to Model 2 and Model 3 toexamine the control performance. Several tools are used to support model development and controller design. Model 0 (including the baseline controller) is a nonlinear full-envelope model developed in Simulink (Chapter 3). Model 1 is developed by introducing the pre-twist angle and BTC in GL Bladed software, the generated power coefficients are then imported to the Simulink model. The simulation of Model 1 and the adapted baseline controller is made in Simulink (Chapter 3). Model 2 is developed by combining the data generated for static ATB in Model 1 and the dynamic ATB model. The full model for baseline control (Chapter 4) and the simplified state-space model for adaptive MPC (Chapter5) are implemented in Matlab and Simulink. Model 3 is used for adaptive MPC, also realised in Matlab and Simulink (Chapter 6). Based on the comprehensive investigation, it is concluded that the ATB WT models developed in this work are suitable for controller design. Both the adapted gain scheduling baseline controller and the proposed adaptive MPC can be applied to achieve satisfactory control performance, that is, to mitigate fatigue load without compromising the power generation of the turbine system. With adaptive MPC, the system demonstratesimprovement in reducing pitch activity, tower acceleration and blade root bending moment.
- Yue, Hong, 1970-
- Doctoral thesis
- 10.48730/9m5m-9226
| Thumbnail | Title | Date Uploaded | Visibility | Actions | | | | 2023-12-20 | Public | | |
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