+publisher:"University of Texas – Austin" +contributor:("Chen, Dongmei, Ph. D.")

University of Texas – Austin

1. Headley, Alexander John. Dynamic subdivided relative humidity model of a polymer electrolyte membrane fuel cell.

Degree: MSin Engineering, Mechanical Engineering, 2013, University of Texas – Austin

► The development of a control-oriented dynamic relative humidity model for a polymer electrolyte membrane (PEM) fuel cell stack is presented. This model is integrated with… (more)

▼ The development of a control-oriented dynamic relative humidity model for a polymer electrolyte membrane (PEM) fuel cell stack is presented. This model is integrated with a first law based thermal model, which tracks energy flow within four defined control volumes in the fuel cell; the cathode channel, anode channel, coolant channel, and fuel cell stack body. Energy and mass conservation equations are developed for each control volume. On top of mass conservation, electro-drag and osmosis models were also implemented within the model to account for the major modes of vapor transfer through the membrane between the anode and cathode. Requisite alterations to the thermal model as well as mass flow rate calculations are also discussed. Initially, the model utilized a single lumped control volume for the calculation of all values each channel (anode and cathode). This lumped value method is computationally inexpensive, and makes the model optimal for control design. However, investigation of the mass-based Biot number showed the need for greater granularity along the length of the channels to properly capture the relative humidity dynamics. In order to improve the resolution of the model, while still minimizing the computation expense, the model was subdivided into a series of lumped value models. The cathode channel was the point of focus as it is the major concern from a controls perspective. This method captures the proper trends found in far more complex CFD models, while still maintaining a quick calculation time. Different levels are subdivision (3 and 6 submodels) are investigated, and the differences discussed. Particularly, temperature range, relative humidity range, the effect on the modeled voltage, and calculation time are compared. This control-oriented model is low order and based on lumped parameters, which makes the computational expense low. Formulation of this model enables the development of control algorithms to achieve optimal thermal and water management. Advisors/Committee Members: Chen, Dongmei, Ph. D. (advisor).

Subjects/Keywords: PEM; Fuel cell; Control-oriented; Thermodynamic; Relative humidity; Model

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APA (6^th Edition):

Headley, A. J. (2013). Dynamic subdivided relative humidity model of a polymer electrolyte membrane fuel cell. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/22264

Chicago Manual of Style (16^th Edition):

Headley, Alexander John. “Dynamic subdivided relative humidity model of a polymer electrolyte membrane fuel cell.” 2013. Masters Thesis, University of Texas – Austin. Accessed February 28, 2021. http://hdl.handle.net/2152/22264.

MLA Handbook (7^th Edition):

Headley, Alexander John. “Dynamic subdivided relative humidity model of a polymer electrolyte membrane fuel cell.” 2013. Web. 28 Feb 2021.

Vancouver:

Headley AJ. Dynamic subdivided relative humidity model of a polymer electrolyte membrane fuel cell. [Internet] [Masters thesis]. University of Texas – Austin; 2013. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/2152/22264.

Council of Science Editors:

Headley AJ. Dynamic subdivided relative humidity model of a polymer electrolyte membrane fuel cell. [Masters Thesis]. University of Texas – Austin; 2013. Available from: http://hdl.handle.net/2152/22264

University of Texas – Austin

2. Ofoegbu, Chukwunyere. Optimal sizing of gas-to-gas membrane humidifiers for proton exchange membrane fuel cell automotive systems.

Degree: MSin Engineering, Mechanical Engineering, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/1457

► External humidification using membrane humidifiers is an attractive technology used in controlling the humidity of proton-exchange membrane fuel cell (PEMFC) systems. Membrane humidifiers operate under… (more)

Subjects/Keywords: PEMFC; Membrane humidifier; Optimization; PEM fuel cell

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APA (6^th Edition):

Ofoegbu, C. (2019). Optimal sizing of gas-to-gas membrane humidifiers for proton exchange membrane fuel cell automotive systems. (Masters Thesis). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/1457

Chicago Manual of Style (16^th Edition):

Ofoegbu, Chukwunyere. “Optimal sizing of gas-to-gas membrane humidifiers for proton exchange membrane fuel cell automotive systems.” 2019. Masters Thesis, University of Texas – Austin. Accessed February 28, 2021. http://dx.doi.org/10.26153/tsw/1457.

MLA Handbook (7^th Edition):

Ofoegbu, Chukwunyere. “Optimal sizing of gas-to-gas membrane humidifiers for proton exchange membrane fuel cell automotive systems.” 2019. Web. 28 Feb 2021.

Vancouver:

Ofoegbu C. Optimal sizing of gas-to-gas membrane humidifiers for proton exchange membrane fuel cell automotive systems. [Internet] [Masters thesis]. University of Texas – Austin; 2019. [cited 2021 Feb 28]. Available from: http://dx.doi.org/10.26153/tsw/1457.

Council of Science Editors:

Ofoegbu C. Optimal sizing of gas-to-gas membrane humidifiers for proton exchange membrane fuel cell automotive systems. [Masters Thesis]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/1457

3. Hall, Russell Ilus. Design and analysis of a new sensing technique for casing joint validation through integrating turns measurement into a torque sensor.

Degree: MSin Engineering, Mechanical Engineering, 2012, University of Texas – Austin

URL: http://hdl.handle.net/2152/23875

► Fossil fuels and their byproducts are a vital part of our economy, and society. Until renewable energy sources and energy storage technologies advance to the… (more)

▼ Fossil fuels and their byproducts are a vital part of our economy, and society. Until renewable energy sources and energy storage technologies advance to the point where they are reliable and inexpensive, the US Economy will continue to depend upon fossil fuels. Current resources are being consumed, and the "easy to reach" reserves are becoming depleted. This leads to the requirement for more exploratory drilling, and the potential for more disasters like the recent Deepwater Horizon spill in the Gulf of Mexico. Drilling is the first of several steps in the creation of a productive oil or natural gas well. Completing a well involves casing the walls in concrete to prevent damage to the surrounding rock formations and to ensure that all of the oil or gas is captured without escaping to the surrounding environment. Ensuring the piping, which is used to case wells, is assembled correctly and to manufacturer's specifications is the focus of this study. Individual pipe sections are screwed together with a requirement for torque and number of turns. Each joint must be verified to ensure integrity, and minimize the possibility of a spill or leak. The torque measurement can be accomplished by a "torque sub", a sensor installed in-line with the drill string. The torque sub is a wireless sensor that transmits torque data to the control system for logging and display. This thesis defines the parameters required to integrate a "number of turns" measurement into an existing torque sub so that both parameters can be captured, recorded and reported using a single device. The Yost Engineering 3-Space Sensor was evaluated for use in this application. The configuration that gave the most accurate data was selected, along with the determination of some correction factors to account for site specific variation in the signals. A calibration algorithm is discussed, along with several unique methods for ensuring that the sensor output doesn't drift over the course of the joint make-up process. Advisors/Committee Members: Chen, Dongmei, Ph. D. (advisor).

Subjects/Keywords: Turns measurement; Casing running; MEMS; IMU; Design of experiments

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APA (6^th Edition):

Hall, R. I. (2012). Design and analysis of a new sensing technique for casing joint validation through integrating turns measurement into a torque sensor. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/23875

Chicago Manual of Style (16^th Edition):

Hall, Russell Ilus. “Design and analysis of a new sensing technique for casing joint validation through integrating turns measurement into a torque sensor.” 2012. Masters Thesis, University of Texas – Austin. Accessed February 28, 2021. http://hdl.handle.net/2152/23875.

MLA Handbook (7^th Edition):

Hall, Russell Ilus. “Design and analysis of a new sensing technique for casing joint validation through integrating turns measurement into a torque sensor.” 2012. Web. 28 Feb 2021.

Vancouver:

Hall RI. Design and analysis of a new sensing technique for casing joint validation through integrating turns measurement into a torque sensor. [Internet] [Masters thesis]. University of Texas – Austin; 2012. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/2152/23875.

Council of Science Editors:

Hall RI. Design and analysis of a new sensing technique for casing joint validation through integrating turns measurement into a torque sensor. [Masters Thesis]. University of Texas – Austin; 2012. Available from: http://hdl.handle.net/2152/23875

4. Chen, Kevin, M.S. in Engineering. Gear ratio optimization of one- and two-speed transmissions for fully-electric vehicles.

Degree: MSin Engineering, Mechanical Engineering, 2017, University of Texas – Austin

URL: http://hdl.handle.net/2152/60449

► Currently, electric vehicles use a transmission with a single-speed fixed gear ratio optimized for performance. This work features the development of a framework to optimize… (more)

Subjects/Keywords: Electric vehicles; Transmission; Optimization; Gear ratio

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APA (6^th Edition):

Chen, Kevin, M. S. i. E. (2017). Gear ratio optimization of one- and two-speed transmissions for fully-electric vehicles. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/60449

Chicago Manual of Style (16^th Edition):

Chen, Kevin, M S in Engineering. “Gear ratio optimization of one- and two-speed transmissions for fully-electric vehicles.” 2017. Masters Thesis, University of Texas – Austin. Accessed February 28, 2021. http://hdl.handle.net/2152/60449.

MLA Handbook (7^th Edition):

Chen, Kevin, M S in Engineering. “Gear ratio optimization of one- and two-speed transmissions for fully-electric vehicles.” 2017. Web. 28 Feb 2021.

Vancouver:

Chen, Kevin MSiE. Gear ratio optimization of one- and two-speed transmissions for fully-electric vehicles. [Internet] [Masters thesis]. University of Texas – Austin; 2017. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/2152/60449.

Council of Science Editors:

Chen, Kevin MSiE. Gear ratio optimization of one- and two-speed transmissions for fully-electric vehicles. [Masters Thesis]. University of Texas – Austin; 2017. Available from: http://hdl.handle.net/2152/60449

5. -6108-5034. Control of high precision roll-to-roll manufacturing systems.

Degree: MSin Engineering, Mechanical Engineering, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/1424

► The flexible electronic industry has been growing rapidly over the past decade. One of the barriers to commercialization is the high cost of manufacturing micro-… (more)

▼ The flexible electronic industry has been growing rapidly over the past decade. One of the barriers to commercialization is the high cost of manufacturing micro- and nano-scale printed electronics using traditional methods. Roll-to-roll manufacturing has been identified as a method of achieving low cost and high throughput. A dynamic model of a roll-to-roll system is presented. In all roll-to-roll applications, tension and velocity must be accurately controlled to desired reference trajectories to ensure a quality finished product. Additionally, a registration error model is presented for the control design. Minimization of the registration is the primary objective for flexible electronics, but web tension and velocity cannot be neglected. The model is needed in order to formulate a methodology that can simultaneously control tension, velocity, and registration error in the presence of disturbances. Micro and nano-scale features are susceptible to damage from friction between the web and the roller. Therefore, tension estimation techniques is highly desired to eliminate load cells from the system. The reduced order observer, extended Kalman filter, and an unknown input observer is presented. Development of tension and velocity control strategies have historically revolved around decentralized SISO control schemes. In order to achieve higher precision, a centralized MIMO strategy is proposed and compared to decentralized SISO. The advantage of the MIMO controller improved handling of the tension velocity coupling in roll-to-roll systems. The tension observer is introduced to the control design and evaluated for overall effectiveness. In simulation, the centralized MIMO control with the unknown input observer demonstrated superior tension and velocity tracking as well as minimal registration error. Development of the proposed MIMO control strategy can enable flexible electronic fabrication using roll-to-roll manufacturing. Advisors/Committee Members: Chen, Dongmei, Ph. D. (advisor).

Subjects/Keywords: Roll-to-roll manufacturing; MIMO control; Tension observer

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APA (6^th Edition):

-6108-5034. (2019). Control of high precision roll-to-roll manufacturing systems. (Masters Thesis). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/1424

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Chicago Manual of Style (16^th Edition):

-6108-5034. “Control of high precision roll-to-roll manufacturing systems.” 2019. Masters Thesis, University of Texas – Austin. Accessed February 28, 2021. http://dx.doi.org/10.26153/tsw/1424.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-6108-5034. “Control of high precision roll-to-roll manufacturing systems.” 2019. Web. 28 Feb 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-6108-5034. Control of high precision roll-to-roll manufacturing systems. [Internet] [Masters thesis]. University of Texas – Austin; 2019. [cited 2021 Feb 28]. Available from: http://dx.doi.org/10.26153/tsw/1424.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-6108-5034. Control of high precision roll-to-roll manufacturing systems. [Masters Thesis]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/1424

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

University of Texas – Austin

6. Refai, Rehan. Hybrid neural net and physics based model of a lithium ion battery.

Degree: MSin Engineering, Mechanical Engineering, 2011, University of Texas – Austin

URL: http://hdl.handle.net/2152/ETD-UT-2011-05-3612

► Lithium ion batteries have become one of the most popular types of battery in consumer electronics as well as aerospace and automotive applications. The efficient… (more)

▼ Lithium ion batteries have become one of the most popular types of battery in consumer electronics as well as aerospace and automotive applications. The efficient use of Li-ion batteries in automotive applications requires well designed battery management systems. Low order Li-ion battery models that are fast and accurate are key to well- designed BMS. The control oriented low order physics based model developed previously cannot predict the temperature and predicts inaccurate voltage dynamics. This thesis focuses on two things: (1) the development of a thermal component to the isothermal model and (2) the development of a hybrid neural net and physics based battery model that corrects the output of the physics based model. A simple first law based thermal component to predict the temperature model is implemented. The thermal model offers a reasonable approximation of the temperature dynamics of the battery discharge over a wide operating range, for both a well-ventilated battery as well as an insulated battery. The model gives an accurate prediction of temperature at higher SOC, but the accuracy drops sharply at lower SOCs. This possibly is due to a local heat generation term that dominates heat generation at lower SOCs. A neural net based modeling approach is used to compensate for the lack of knowledge of material parameters of the battery cell in the existing physics based model. This model implements a neural net that corrects the voltage output of the model and adds a temperature prediction sub-network. Given the knowledge of the physics of the battery, sparse neural nets are used. Multiple types of standalone neural nets as well as hybrid neural net and physics based battery models are developed and tested to determine the appropriate configuration for optimal performance. The prediction of the neural nets in ventilated, insulated and stressed conditions was compared to the actual outputs of the batteries. The modeling approach presented here is able to accurately predict voltage output of the battery for multiple current profiles. The temperature prediction of the neural nets in the case of the ventilated batteries was harder to predict since the environment of the battery was not controlled. The temperature predictions in the insulated cases were quite accurate. The neural nets are trained, tested and validated using test data from a 4.4Ah Boston Power lithium ion battery cell. Advisors/Committee Members: Chen, Dongmei, Ph. D. (advisor), Fernandez, Benito R. (committee member).

Subjects/Keywords: Lithium ion batteries; Neural nets; Thermal modeling; Hybrid neural net; Battery simulation

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APA (6^th Edition):

Refai, R. (2011). Hybrid neural net and physics based model of a lithium ion battery. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/ETD-UT-2011-05-3612

Chicago Manual of Style (16^th Edition):

Refai, Rehan. “Hybrid neural net and physics based model of a lithium ion battery.” 2011. Masters Thesis, University of Texas – Austin. Accessed February 28, 2021. http://hdl.handle.net/2152/ETD-UT-2011-05-3612.

MLA Handbook (7^th Edition):

Refai, Rehan. “Hybrid neural net and physics based model of a lithium ion battery.” 2011. Web. 28 Feb 2021.

Vancouver:

Refai R. Hybrid neural net and physics based model of a lithium ion battery. [Internet] [Masters thesis]. University of Texas – Austin; 2011. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/2152/ETD-UT-2011-05-3612.

Council of Science Editors:

Refai R. Hybrid neural net and physics based model of a lithium ion battery. [Masters Thesis]. University of Texas – Austin; 2011. Available from: http://hdl.handle.net/2152/ETD-UT-2011-05-3612

University of Texas – Austin

7. Varala, Vinod Kumar. Modeling of horizontal drilling.

Degree: MSin Engineering, Mechanical engineering, 2016, University of Texas – Austin

URL: http://hdl.handle.net/2152/43683

► While majority of today’s oil wells employ directional drilling technology (deviated, extended reach and horizontal wells), a thorough understanding of the drill string dynamics is… (more)

Subjects/Keywords: Oil and gas industry; Directional drilling; Drill string; Stick-slip; Bit-bounce; Lumped mass

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APA (6^th Edition):

Varala, V. K. (2016). Modeling of horizontal drilling. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/43683

Chicago Manual of Style (16^th Edition):

Varala, Vinod Kumar. “Modeling of horizontal drilling.” 2016. Masters Thesis, University of Texas – Austin. Accessed February 28, 2021. http://hdl.handle.net/2152/43683.

MLA Handbook (7^th Edition):

Varala, Vinod Kumar. “Modeling of horizontal drilling.” 2016. Web. 28 Feb 2021.

Vancouver:

Varala VK. Modeling of horizontal drilling. [Internet] [Masters thesis]. University of Texas – Austin; 2016. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/2152/43683.

Council of Science Editors:

Varala VK. Modeling of horizontal drilling. [Masters Thesis]. University of Texas – Austin; 2016. Available from: http://hdl.handle.net/2152/43683

8. Anyaegbunam, Ifedioranma. The development of a battery management system with special focus on capacity estimation and thermal management.

Degree: MSin Engineering, Mechanical engineering, 2016, University of Texas – Austin

URL: http://hdl.handle.net/2152/41245

► Lithium ion batteries are instrumental in tackling the challenges of global warming. They have shown great utility in electric and hybrid vehicles. However, challenges with… (more)

▼ Lithium ion batteries are instrumental in tackling the challenges of global warming. They have shown great utility in electric and hybrid vehicles. However, challenges with regard to performance and safety such as capacity fade and thermal runaway need to be accounted for in the implementation of these battery systems. One way is through battery management systems that monitor and control various aspects of the battery’s operation. At the heart of the battery management system is an analytical model of the battery. This thesis proposes a battery management system which uses a “lowuses a “low-order” physics- based battery model that estimates capacity and optimally manages the temperature of the battery. A capacity estimation methodology is proposed that uses the state of charge estimate from an extended kalman filter and the inverse of the coulomb counting equation to estimates the “instant” capacity of the battery. This instant value is then used in an averaging calculation that uses saturation limits and a time delay to obtain a value for the capacity that is representative of the battery. This value is then feedback into the kalman filter. The capacity estimate obtained through this method was between 2 and 8 % off of the true value. A thermal management system is also proposed that optimally controls a fan to cool a lithium ion battery. The thermal management system was developed and tested in a simulated environment. First, the fan model was integrated with the battery model and simulations were run to test the open loop temperature response of the battery to the fan cooling while varying the input voltage of the fan the current demanded of the battery. From this data an operating point was chosen, the system was linearized, and a linear quadratic controller was designed and implemented. The controller was sluggish when faced with a temperature perturbation in the absence of a current demand increase but drove the temperature change to zero. In the presence of a current change controller drove the state to a nonzero steady state value. The same result occurred when a disturbance rejection mechanism was applied to the controller. Advisors/Committee Members: Chen, Dongmei, Ph. D. (advisor), Beaman, Joseph (committee member).

Subjects/Keywords: Capacity fade; Optimal control; Thermal management; Li-ion battery

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APA (6^th Edition):

Anyaegbunam, I. (2016). The development of a battery management system with special focus on capacity estimation and thermal management. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/41245

Chicago Manual of Style (16^th Edition):

Anyaegbunam, Ifedioranma. “The development of a battery management system with special focus on capacity estimation and thermal management.” 2016. Masters Thesis, University of Texas – Austin. Accessed February 28, 2021. http://hdl.handle.net/2152/41245.

MLA Handbook (7^th Edition):

Anyaegbunam, Ifedioranma. “The development of a battery management system with special focus on capacity estimation and thermal management.” 2016. Web. 28 Feb 2021.

Vancouver:

Anyaegbunam I. The development of a battery management system with special focus on capacity estimation and thermal management. [Internet] [Masters thesis]. University of Texas – Austin; 2016. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/2152/41245.

Council of Science Editors:

Anyaegbunam I. The development of a battery management system with special focus on capacity estimation and thermal management. [Masters Thesis]. University of Texas – Austin; 2016. Available from: http://hdl.handle.net/2152/41245

9. Michael, Philip Henry. A multicomponent membrane model for the vanadium redox flow battery.

Degree: MSin Engineering, Mechanical Engineering, 2012, University of Texas – Austin

URL: http://hdl.handle.net/2152/ETD-UT-2012-08-6261

► With its long cycle life and scalable design, the vanadium redox flow battery (VRB) is a promising technology for grid energy storage. However, high materials… (more)

Subjects/Keywords: Concentrated-solution theory; Redox flow batteries; Vanadium redox flow battery; Cation-exchange membranes; Computational modeling; Electrical energy storage

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APA (6^th Edition):

Michael, P. H. (2012). A multicomponent membrane model for the vanadium redox flow battery. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/ETD-UT-2012-08-6261

Chicago Manual of Style (16^th Edition):

Michael, Philip Henry. “A multicomponent membrane model for the vanadium redox flow battery.” 2012. Masters Thesis, University of Texas – Austin. Accessed February 28, 2021. http://hdl.handle.net/2152/ETD-UT-2012-08-6261.

MLA Handbook (7^th Edition):

Michael, Philip Henry. “A multicomponent membrane model for the vanadium redox flow battery.” 2012. Web. 28 Feb 2021.

Vancouver:

Michael PH. A multicomponent membrane model for the vanadium redox flow battery. [Internet] [Masters thesis]. University of Texas – Austin; 2012. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/2152/ETD-UT-2012-08-6261.

Council of Science Editors:

Michael PH. A multicomponent membrane model for the vanadium redox flow battery. [Masters Thesis]. University of Texas – Austin; 2012. Available from: http://hdl.handle.net/2152/ETD-UT-2012-08-6261

10. Hearn, Clay Stephen. Design methodologies for advanced flywheel energy storage.

Degree: PhD, Mechanical Engineering, 2013, University of Texas – Austin

URL: http://hdl.handle.net/2152/23032

► Higher penetration of volatile renewable sources and increasing load demand are putting a strain on the current utility grid structure. Energy storage solutions are required… (more)

▼ Higher penetration of volatile renewable sources and increasing load demand are putting a strain on the current utility grid structure. Energy storage solutions are required to maintain grid stability and are vital components to future smart grid designs. Flywheel energy storage can be a strong part of the solution due to high cycle life capabilities and flexible design configurations that balance power and energy capacity. This dissertation focuses on developing design methodologies for advanced flywheel energy storage, with an emphasis on sizing flywheel energy storage and developing lumped parameter modeling techniques for low loss, high temperature superconducting. The first contribution of this dissertation presents a method for using an optimal control law to size flywheel energy storage and develops a design space for potential power and energy storage combinations. This method is a data driven technique, that utilizes power consumption and renewable generation data from a particular location where the storage may be placed. The model for this sizing technique includes the spinning losses, that are unique to flywheel energy storage systems and have limited this technology to short term storage applications, such as frequency and voltage regulation. For longer term storage solutions, the spinning losses for flywheels must be significantly reduced. One potential solution is to use high temperature superconducting bearings, that work by the stable levitation of permanent magnet materials over bulk superconductors. These advanced bearing systems can reduce losses to less than 0.1% stored energy per hour. In order to integrate high temperature superconducting bearings into flywheel system designs, accurate and reduced order models are needed, that include the losses and emulate the hysteretic, non-linear behavior of superconducting levitation. The next two contributions of this dissertation present a lumped parameter axissymmetric model and a 3-D lumped parameter transverse model, which can be used to evaluate bearing lifting capabilities and transverse stiffness for flywheel rotor designs. These models greatly reduce computational time, and were validated against high level finite element analysis, and dynamic experimental tests. The validation experiments are described in detail. Advisors/Committee Members: Chen, Dongmei, Ph. D. (advisor), Longoria, Raul G. (advisor).

Subjects/Keywords: Flywheel energy storage; Sizing energy storage; Grid storage; High temperature superconducting bearings; Electromechanical bond graph models

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APA (6^th Edition):

Hearn, C. S. (2013). Design methodologies for advanced flywheel energy storage. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/23032

Chicago Manual of Style (16^th Edition):

Hearn, Clay Stephen. “Design methodologies for advanced flywheel energy storage.” 2013. Doctoral Dissertation, University of Texas – Austin. Accessed February 28, 2021. http://hdl.handle.net/2152/23032.

MLA Handbook (7^th Edition):

Hearn, Clay Stephen. “Design methodologies for advanced flywheel energy storage.” 2013. Web. 28 Feb 2021.

Vancouver:

Hearn CS. Design methodologies for advanced flywheel energy storage. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2013. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/2152/23032.

Council of Science Editors:

Hearn CS. Design methodologies for advanced flywheel energy storage. [Doctoral Dissertation]. University of Texas – Austin; 2013. Available from: http://hdl.handle.net/2152/23032

University of Texas – Austin

11. -6028-0636. Cost-conscious control strategies for wind turbine systems.

Degree: PhD, Mechanical Engineering, 2017, University of Texas – Austin

URL: http://hdl.handle.net/2152/47462

► Wind energy is one of the most abundant renewable energy sources that can meet future energy demands. Despite its fast growth, wind energy is still… (more)

▼ Wind energy is one of the most abundant renewable energy sources that can meet future energy demands. Despite its fast growth, wind energy is still a marginal player in electricity generation. The key issues preventing wider deployment of wind turbines include low energy conversion efficiency, high maintenance cost, wind intermittency and unpredictability etc. These issues lead to considerably higher cost of wind power compared to that of traditional power sources. This work is focused on control designs to overcome the above challenges. First, control algorithms are developed for energy capture maximization. During partial load operation, wind turbine rotor speed is continuously adjusted to remain optimal operation by manipulating the electromagnetic torque applied to the generator. In this dissertation, a dynamic programming based real-time controller (DPRC) and a gain modified optimal torque controller (GMOTC) are developed for faster convergence to optimal power operation under volatile wind speed and better robustness against modeling uncertainties. Secondly, fatigue loading mitigation techniques are developed to reduce the maintenance cost of a wind turbine. During partial load operation, a generator torque-based fatigue mitigation method is devised to reduce the impact of exacerbated tower bending moments associated with the resonance effect. During full load operation, a H₂ optimization has been carried out for gain scheduling of a Proportional-Integral blade pitch controller. It improves speed regulation and reduces drivetrain fatigue loading with less oscillations of turbine rotor speed and generator torque. Thirdly, battery energy storage systems (BESS) have been integrated with wind turbines to mitigate wind intermittence and make wind power dispatchable as traditional power sources. Equipped with a probabilistic wind speed forecasting model, a new power scheduling and real-time control approach has been proposed to improve the performance of the integrated system. Finally, control designs are oriented to wind turbine participation in grid primary frequency regulation. The fast active power injection/absorption capability of wind turbine enables it to rapidly change its power output for stablizing the grid frequency following an sudden power imbalance event. In addition to quick response to grid frequency deviation event, the proposed controller guarantees turbine stability with smooth control actions. Advisors/Committee Members: Chen, Dongmei, Ph. D. (advisor), Baldick, Ross (committee member), Djurdjanovic, Dragan (committee member), Longoria, Raul G. (committee member), Barr, Ronald (committee member).

Subjects/Keywords: Wind turbine; Wind energy; Adaptive algorithm; Power dispatch; Frequency regulation; Energy maximization; Fatigue mitigation

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APA (6^th Edition):

-6028-0636. (2017). Cost-conscious control strategies for wind turbine systems. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/47462

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Chicago Manual of Style (16^th Edition):

-6028-0636. “Cost-conscious control strategies for wind turbine systems.” 2017. Doctoral Dissertation, University of Texas – Austin. Accessed February 28, 2021. http://hdl.handle.net/2152/47462.

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MLA Handbook (7^th Edition):

-6028-0636. “Cost-conscious control strategies for wind turbine systems.” 2017. Web. 28 Feb 2021.

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Author name may be incomplete

Vancouver:

-6028-0636. Cost-conscious control strategies for wind turbine systems. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2017. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/2152/47462.

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Author name may be incomplete

Council of Science Editors:

-6028-0636. Cost-conscious control strategies for wind turbine systems. [Doctoral Dissertation]. University of Texas – Austin; 2017. Available from: http://hdl.handle.net/2152/47462

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Author name may be incomplete

12. -4907-2702. Model-based decentralized optimal control of a microgrid.

Degree: PhD, Mechanical Engineering, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/5755

► Power networks have experienced dramatic changes with the growth of renewable energy and `smart' grids. To accommodate the challenges posed to traditional power system control… (more)

▼ Power networks have experienced dramatic changes with the growth of renewable energy and `smart' grids. To accommodate the challenges posed to traditional power system control architectures, the microgrid concept has gained traction. Microgrids are small-scale power networks that can disconnect from the main grid and operate autonomously if necessary. These systems add robustness and facilitate the incorporation of renewable power, but they face control challenges of their own due to the lack of significant inertial generation. Without the main grid to provide balance, the high proportion of electrically-interfaced power resources can cause significant deterioration in microgrid stability. This dissertation proposes designs to improve decentralized control in microgrids; model based information is incorporated into controllers and estimators to more optimally guide control signals, while still only using local data for real-time computation. We outline the role that microgrid topology can have on stability, and how judicious power injection can mitigate instabilities. These results are extended to a decentralized H-infinity control design for microgrid frequency; even with limited model-based information and controller distribution, the design offers significant improvements over traditional controllers. Building upon the idea of microgrid stabilization, we also present a control method by which a wind turbine can be coordinated for microgrid support. The wind turbine is used as a controllable power source by utilizing the rotational energy stored in its rotor; this design incorporates an aerodynamic wind turbine model and a novel optimal blade pitch angle controller to ensure stable turbine operation. This allows for rapid power injection for grid support. This theme concludes with a decentralized estimation scheme to facilitate coordinated control across a microgrid using only local data. We leverage the frequency synchronization and load-sharing intrinsic to the microgrid so that local measurements can provide insight about grid-wide conditions. This allows for effective implementation of optimal filtering techniques so that remote conditions can be estimated using only local data; this allows for grid-wide coordination and optimization. Together these ideas represent the concept that the microgrid model, even in a limited and inaccurate sense, can be manipulated to provide significant benefits for decentralized control across the network. Advisors/Committee Members: Chen, Dongmei, Ph. D. (advisor), Bakolas, Efstathios (committee member), Du, Pengwei (committee member), Hall, Matthew J (committee member), Seepersad, Carolyn (committee member).

Subjects/Keywords: Renewable energy; Microgrid; Power systems; Optimal; Optimal control; Decentralized control; Dynamic systems

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APA (6^th Edition):

-4907-2702. (2019). Model-based decentralized optimal control of a microgrid. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/5755

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Chicago Manual of Style (16^th Edition):

-4907-2702. “Model-based decentralized optimal control of a microgrid.” 2019. Doctoral Dissertation, University of Texas – Austin. Accessed February 28, 2021. http://dx.doi.org/10.26153/tsw/5755.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-4907-2702. “Model-based decentralized optimal control of a microgrid.” 2019. Web. 28 Feb 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-4907-2702. Model-based decentralized optimal control of a microgrid. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2019. [cited 2021 Feb 28]. Available from: http://dx.doi.org/10.26153/tsw/5755.

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Author name may be incomplete

Council of Science Editors:

-4907-2702. Model-based decentralized optimal control of a microgrid. [Doctoral Dissertation]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/5755

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Author name may be incomplete

University of Texas – Austin

13. -4221-291X. Optimal control of wind turbines for distributed power generation.

Degree: PhD, Mechanical engineering, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/31543

► Wind energy represents one of the major renewable energy sources that can meet future energy demands to sustain our lifestyle. During the last few decades,… (more)

▼ Wind energy represents one of the major renewable energy sources that can meet future energy demands to sustain our lifestyle. During the last few decades, the installation of wind turbines for power generation has grown rapidly worldwide. Besides utility scale wind farms, distributed wind energy systems contributes to the rise in wind energy penetration. However, the expansion of distributed wind energy systems is faced by major challenges such as the system’s reliability in addition to the environmental impacts. This work is intended to explore various control algorithms to enable the distributed wind energy systems to face the aforementioned challenges. First of all, a stall regulated fixed speed wind turbine augmented with a variable ratio gearbox has been proven to enhance the wind energy capture at a relatively low cost, and considered as an attractive design for small wind energy systems. However, the high reliability advantage of traditional fixed-speed wind turbines can be affected by the integration of the variable ratio gearbox. A portion of this work is intended to develop a control algorithm that extends the variable ratio gearbox service life, thus improves overall system reliability and reduces the expected operational cost. Secondly, a pitch regulated variable speed wind turbines dominates the wind energy industry as it represents a balance between cost and flexibility of operation. They can be used for midsized wind power generation. Optimizing its wind energy capture while maintain high system reliability has been the one of the main focuses of many researchers. Another portion of this work introduces a model predictive control framework that enhances the reliability of pitch regulated variable speed wind turbines, thus improves their operational cost. Finally, one of the major environmental challenges facing the continuous growth of wind energy industry is the noise emitted from wind turbines. The severity of the noise emission problem is more significant for small and medium sized wind turbines installed in the vicinity of residential areas for distributed power generation. Consequently, the last portion of this work is intended to investigate the potential of wind turbine control design to reduce noise emission in different operating conditions with minimal impact on power generation Advisors/Committee Members: Chen, Dongmei, Ph. D. (advisor), Longoria, Raul G. (committee member), Crawford, Richard H. (committee member), Deshpande, Ashish D. (committee member), Malikopoulos, Andreas A. (committee member), Pratap, Siddharth B. (committee member).

Subjects/Keywords: Wind energy; Optimal control; Energy maximization; Fatigue load mitigation; Noise emission reduction

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APA (6^th Edition):

-4221-291X. (2015). Optimal control of wind turbines for distributed power generation. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/31543

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Chicago Manual of Style (16^th Edition):

-4221-291X. “Optimal control of wind turbines for distributed power generation.” 2015. Doctoral Dissertation, University of Texas – Austin. Accessed February 28, 2021. http://hdl.handle.net/2152/31543.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-4221-291X. “Optimal control of wind turbines for distributed power generation.” 2015. Web. 28 Feb 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-4221-291X. Optimal control of wind turbines for distributed power generation. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2015. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/2152/31543.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-4221-291X. Optimal control of wind turbines for distributed power generation. [Doctoral Dissertation]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/31543

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

University of Texas – Austin

14. Yan, Zeyu, Ph. D. Numerical optimal control of a wind turbine system.

Degree: PhD, Mechanical engineering, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/31546

► With the development of wind turbine technology and the need for maximizing wind energy harvesting, more wind turbines operate in the partial load region. Among… (more)

▼ With the development of wind turbine technology and the need for maximizing wind energy harvesting, more wind turbines operate in the partial load region. Among many control algorithms developed for this region, controllers based on feedback of the global maximum power coefficient have been widely used. These control schemes offer good performance with simple implementations, but they may not be suited for wind turbines with limited rotor speed ranges. In such cases, the controller is challenged because the main feature – the global maximum power coefficient – is not achievable due to the turbine speed constraint. It is necessary to develop a controller to seek the achievable maximum power coefficient that leads to optimal wind energy capture. In this dissertation, the development of an optimal control framework to maximize wind energy capture for wind turbines with constrained turbine speed is first presented. Numerical optimal control techniques are applied to search for the achievable maximum power coefficient, with proposed modifications to make this task more computationally feasible. Mitigating the turbine generator torque variation, thus reducing the fatigue loading on turbine generator shaft, is also important for the partial load region operation. Including this aspect in the optimal control is then discussed. Furthermore, an approach of incorporating time-varying weightings into developing the optimal controller is introduced to seek further improvement on turbine generator torque variation reduction, thus fatigue reduction. In addition, the power generated by the wind turbine varies due to variation in the wind speed. Depending on the load demand and the wind speed, the wind turbine's operation switches between two modes: a multi-input-single-output (MISO) mode and a single-input-single-output (SISO) mode. Due to the wind turbine changes its dynamic behavior during the switching process, applying the traditional control methods to each corresponding mode may not be capable of maximizing the overall wind energy capture throughout the entire turbine's operation. Therefore, the development of an optimal control framework to maximize the overall wind energy capture for a switched wind turbine system is subsequently presented. Advisors/Committee Members: Chen, Dongmei, Ph. D. (advisor), Fahrenthold, Eric P. (committee member), Hall, Neal A. (committee member), Li, Wei (committee member), Seepersad, Carolyn C. (committee member).

Subjects/Keywords: Wind turbine; Optimal control

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APA (6^th Edition):

Yan, Zeyu, P. D. (2015). Numerical optimal control of a wind turbine system. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/31546

Chicago Manual of Style (16^th Edition):

Yan, Zeyu, Ph D. “Numerical optimal control of a wind turbine system.” 2015. Doctoral Dissertation, University of Texas – Austin. Accessed February 28, 2021. http://hdl.handle.net/2152/31546.

MLA Handbook (7^th Edition):

Yan, Zeyu, Ph D. “Numerical optimal control of a wind turbine system.” 2015. Web. 28 Feb 2021.

Vancouver:

Yan, Zeyu PD. Numerical optimal control of a wind turbine system. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2015. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/2152/31546.

Council of Science Editors:

Yan, Zeyu PD. Numerical optimal control of a wind turbine system. [Doctoral Dissertation]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/31546

University of Texas – Austin

15. -3146-1283. Modeling, estimation, and control of proton exchange membrane-based electrochemical systems.

Degree: PhD, Mechanical Engineering, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/32873

► To reduce emissions and meet the rapidly growing global energy demand, affordable and efficient methods of electrical energy storage and generation are needed to exploit… (more)

▼ To reduce emissions and meet the rapidly growing global energy demand, affordable and efficient methods of electrical energy storage and generation are needed to exploit renewable energy sources more effectively. Proton exchange membrane (PEM) based electrochemical systems, such as vanadium redox flow batteries (VRFB) and PEM fuel cells, are playing an increasingly important role because they have a fast response rate, high efficiency, and small environmental impact. However, widespread commercial viability of these technologies in the future heavily depends on further improvements in their performance and reliability. Accordingly, this dissertation focuses on developing new methodologies to predict and control the behavior of these PEM-based electrochemical systems. In the first part of this work, a control-oriented physics-based model of a VRFB system is developed. This model can predict the transient response of the cell voltage under different operating conditions and inputs such as current, flow rate, and temperature. The significance of this study is having the ability to predict the short and long term effects of membrane crossover on the system performance. One major challenge of operating VRFB systems is that monitoring the state-of-charge (SOC) in real-time using traditional measurement techniques is expensive and impractical. To address this problem, an SOC estimator is developed based on a constrained extended Kalman filter that can be used for real-time optimization and control because it requires only simple voltage measurements and a low-order model. Simulation results demonstrate the ability to predict the vanadium concentrations of a VRFB system without knowledge of the crossover dynamics. A major obstacle preventing the widespread commercialization of VRFBs is excessive capital costs. This issue is addressed by developing a methodology to optimally size a VRFB system using the minimum amount of materials required for the intended power range. For PEM fuel cells, proper water and thermal management is critical to optimizing performance and longevity. However, this can be a challenging task due to strong system interactions between multiple input and output variables. In the final part of this work, these system interactions are studied in detail and a suitable controller is designed to regulate the stack voltage, stack temperature, and relative humidity during load transients. Advisors/Committee Members: Chen, Dongmei, Ph. D. (advisor), Longoria, Raul G (committee member), Deshpande, Ashish D (committee member), Fahrenthold, Eric P (committee member), Edgar, Thomas F (committee member).

Subjects/Keywords: Modeling; Estimation; Control; Flow battery; PEM fuel cell

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APA (6^th Edition):

-3146-1283. (2015). Modeling, estimation, and control of proton exchange membrane-based electrochemical systems. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/32873

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Chicago Manual of Style (16^th Edition):

-3146-1283. “Modeling, estimation, and control of proton exchange membrane-based electrochemical systems.” 2015. Doctoral Dissertation, University of Texas – Austin. Accessed February 28, 2021. http://hdl.handle.net/2152/32873.

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MLA Handbook (7^th Edition):

-3146-1283. “Modeling, estimation, and control of proton exchange membrane-based electrochemical systems.” 2015. Web. 28 Feb 2021.

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Vancouver:

-3146-1283. Modeling, estimation, and control of proton exchange membrane-based electrochemical systems. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2015. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/2152/32873.

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Council of Science Editors:

-3146-1283. Modeling, estimation, and control of proton exchange membrane-based electrochemical systems. [Doctoral Dissertation]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/32873

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16. Hadisujoto, Budi Sutanto. Control-oriented modeling of dynamic thermal behavior and two‒phase fluid flow in porous media for PEM fuel cells.

Degree: PhD, Mechanical Enginering, 2013, University of Texas – Austin

URL: http://hdl.handle.net/2152/28727

► The driving force behind research in alternative clean and renewable energy has been the desire to reduce emissions and dependence on fossil fuels. In the… (more)

▼ The driving force behind research in alternative clean and renewable energy has been the desire to reduce emissions and dependence on fossil fuels. In the United States, ground vehicles account for 30% of total carbon emission, and significantly contribute to other harmful emissions. This issue causes environmental concerns and threat to human health. On the other hand, the demand on fossil fuel grows with the increasing energy consumption worldwide. Particularly in the United States of America, transportation absorbs 75% of this energy source. There is an urgent need to reduce the transportation dependence on fossil fuel for the purpose of national security. Polymer electrolyte membrane (PEM) fuel cells are strong potential candidates to replace the traditional combustion engines. Even though research effort has transferred the fuel cell technology into real‒world vehicle applications, there are still several challenges hindering the fuel cell technology commercialization, such as hydrogen supply infrastructure, cost of the fuel cell vehicles, on‒board hydrogen storage, public acceptance, and more importantly the performance, durability, and reliability of the PEM fuel cell vehicles themselves. One of the key factors that affect the fuel cell performance and life is the run‒time thermal and water management. The temperature directly affects the humidification of the fuel cell stack and plays a critical role in avoiding liquid water flooding as well as membrane dehydration which affect the performance and long term reliability. There are many models exists in the literature. However, there are still lacks of control‒oriented modeling techniques that describe the coupled heat and mass transfer dynamics, and experimental validation is rarely performed for these models. In order to establish an in‒depth understanding and enable control design to achieve optimal performance in real‒time, this research has explored modeling techniques to describe the coupled heat and mass transfer dynamics inside a PEM fuel cell. This dissertation is to report our findings on modeling the temperature dynamics of the gas and liquid flow in the porous media for the purpose of control development. The developed thermal model captures the temperature dynamics without using much computation power commonly found in CFD models. The model results agree very well with the experimental validation of a 1.5 kW fuel cell stack after calibrations. Relative gain array (RGA) was performed to investigate the coupling between inputs and outputs and to explore the possibility of using a single‒input single‒output (SISO) control scheme for this multi‒input multi‒output (MIMO) system. The RGA analyses showed that SISO control design would be effective for controlling the fuel cell stack alone. Adding auxiliary components to the fuel cell stack, such as compressor to supply the pressurized air, requires a MIMO control framework. The developed model of describing water transport in porous media improves the modeling accuracy by adding catalyst layers and… Advisors/Committee Members: Moon, T. J. (Tess J.) (advisor), Chen, Dongmei, Ph. D. (advisor).

Subjects/Keywords: Polymer electrolyte membrane; Fuel cell; Thermal model

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APA (6^th Edition):

Hadisujoto, B. S. (2013). Control-oriented modeling of dynamic thermal behavior and two‒phase fluid flow in porous media for PEM fuel cells. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/28727

Chicago Manual of Style (16^th Edition):

Hadisujoto, Budi Sutanto. “Control-oriented modeling of dynamic thermal behavior and two‒phase fluid flow in porous media for PEM fuel cells.” 2013. Doctoral Dissertation, University of Texas – Austin. Accessed February 28, 2021. http://hdl.handle.net/2152/28727.

MLA Handbook (7^th Edition):

Hadisujoto, Budi Sutanto. “Control-oriented modeling of dynamic thermal behavior and two‒phase fluid flow in porous media for PEM fuel cells.” 2013. Web. 28 Feb 2021.

Vancouver:

Hadisujoto BS. Control-oriented modeling of dynamic thermal behavior and two‒phase fluid flow in porous media for PEM fuel cells. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2013. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/2152/28727.

Council of Science Editors:

Hadisujoto BS. Control-oriented modeling of dynamic thermal behavior and two‒phase fluid flow in porous media for PEM fuel cells. [Doctoral Dissertation]. University of Texas – Austin; 2013. Available from: http://hdl.handle.net/2152/28727

17. Palejiya, Dushyant. Switching control of wind turbine.

Degree: PhD, Mechanical Engineering, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/33284

► Modern variable speed wind turbines operate within large range of wind speeds. Control of such a turbine is partitioned in two modes: a low wind… (more)

Subjects/Keywords: Wind turbine control; Switching stability; Switched systems

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APA (6^th Edition):

Palejiya, D. (2015). Switching control of wind turbine. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/33284

Chicago Manual of Style (16^th Edition):

Palejiya, Dushyant. “Switching control of wind turbine.” 2015. Doctoral Dissertation, University of Texas – Austin. Accessed February 28, 2021. http://hdl.handle.net/2152/33284.

MLA Handbook (7^th Edition):

Palejiya, Dushyant. “Switching control of wind turbine.” 2015. Web. 28 Feb 2021.

Vancouver:

Palejiya D. Switching control of wind turbine. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2015. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/2152/33284.

Council of Science Editors:

Palejiya D. Switching control of wind turbine. [Doctoral Dissertation]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/33284

18. Headley, Alexander John. Dynamic modeling and analysis of proton exchange membrane fuel cells for control design.

Degree: PhD, Mechanical engineering, 2016, University of Texas – Austin

URL: http://hdl.handle.net/2152/39748

► This dissertation seeks to address a number of issues facing the advancement of Proton Exchange Membrane (PEM) fuel cell technology by improving control-oriented modeling strategies… (more)

▼ This dissertation seeks to address a number of issues facing the advancement of Proton Exchange Membrane (PEM) fuel cell technology by improving control-oriented modeling strategies for these systems. Real-time control is a major ongoing challenge for PEM fuel cell technologies, particularly with regards to water and temperature dynamics. This can lead to a number of operational concerns, such as membrane flooding and dehydration, which can seriously diminish the efficiency, reliability, and long term health of the system. To combat these issues, comprehensive models that are capable of capturing the dynamics of the key operating conditions and can be processed in real time are needed. Also, given the inherently distributed nature of the system, such a model would ideally account for the changes in the conditions from cell-to-cell in the stack, which can be very significant. With this goal in mind, the main focus of this dissertation is the development and experimental validation of control-oriented modeling techniques for PEM fuel cell stacks. The first major work in this study was the verification of a relative humidity model in response to varying loads. Through this work, a multiple control volume (CV) approach was developed and experimentally validated to model the distribution of operating conditions more accurately while keeping the computational expense sufficiently low. To optimize the modeling efforts, further analysis of the temperature and vapor distribution was performed starting from first principles. This led to the creation of various techniques to optimally size CVs based on the parameters and operating conditions of the system in question. Finally, it was noted throughout the testing that the performance of the membrane electrolyte assemblies in the test stack declined significantly from their initial state. To compensate for this, a Kalman filter was implemented to quantify the membrane degradation. SEM analysis of membranes from the test stack confirmed the validity of this technique. This work can be used to significantly improve real-time models for PEM fuel cells for model-based control applications. Advisors/Committee Members: Chen, Dongmei, Ph. D. (advisor), Wei, Li (committee member), Beaman, Joseph J (committee member), Ezekoye, Ofodike A (committee member), Mullins, Charles B (committee member).

Subjects/Keywords: Fuel cells; Dynamic modeling

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APA (6^th Edition):

Headley, A. J. (2016). Dynamic modeling and analysis of proton exchange membrane fuel cells for control design. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/39748

Chicago Manual of Style (16^th Edition):

Headley, Alexander John. “Dynamic modeling and analysis of proton exchange membrane fuel cells for control design.” 2016. Doctoral Dissertation, University of Texas – Austin. Accessed February 28, 2021. http://hdl.handle.net/2152/39748.

MLA Handbook (7^th Edition):

Headley, Alexander John. “Dynamic modeling and analysis of proton exchange membrane fuel cells for control design.” 2016. Web. 28 Feb 2021.

Vancouver:

Headley AJ. Dynamic modeling and analysis of proton exchange membrane fuel cells for control design. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2016. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/2152/39748.

Council of Science Editors:

Headley AJ. Dynamic modeling and analysis of proton exchange membrane fuel cells for control design. [Doctoral Dissertation]. University of Texas – Austin; 2016. Available from: http://hdl.handle.net/2152/39748

19. Hall, John Francis, 1968-. Design and control of a variable ratio gearbox for distributed wind turbine systems.

Degree: PhD, Mechanical Engineering, 2012, University of Texas – Austin

URL: http://hdl.handle.net/2152/ETD-UT-2012-08-6105

► Wind is one of the most promising resources in the renewable energy portfolio. Still, the cost of electrical power produced by small wind turbines impedes… (more)

▼ Wind is one of the most promising resources in the renewable energy portfolio. Still, the cost of electrical power produced by small wind turbines impedes the use of this technology, which can otherwise provide power to millions of homes in rural regions worldwide. To encourage their use, small wind turbines must convert wind energy more effectively while avoiding increased equipment costs. A variable ratio gearbox (VRG) can provide this capability to the simple low-cost fixed-speed wind turbine through discrete operating speeds. The VRG concept is based upon mature technology taken from the automotive industry and is characterized by low cost and high reliability. A 100 kW model characterizes the benefits of integrating a VRG into a fixed-speed stall-regulated wind turbine system. Simulation results suggest it improves the efficiency of the fixed-speed turbine in the partial-load region and has the ability to limit power in the full-load region where pitch control is often used. To maximize electrical production, mechanical braking is applied during the normal operation of the wind turbine. A strategy is used to select gear ratios that produce torque slightly above the maximum amount the generator can accept while simultaneously applying the mechanical brake, so that full-load production may be realized over greater ranges of the wind speed. Dynamic programming is used to establish the VRG ratios and an optimal control design. This optimization strategy maximizes the energy production while insuring that the brake pads maintain a predetermined service life. In the final step of the research, a decision-making algorithm is developed to find the gears that emulate the ratios found in the optimal control design. The objective is to match the energy level as closely as possible, minimize the mass of the gears, and insure that tooth failure does not occur over the design life of the VRG. Recorded wind data of various wind classes is used to quantify the benefit of using the VRG. The results suggest that an optimized VRG design can increase wind energy production by roughly 10% at all of the sites in the study. Advisors/Committee Members: Chen, Dongmei, Ph. D. (advisor), Longoria, Raul G. (committee member), Masada, Glenn Y. (committee member), Pratap, Siddharth B. (committee member), Traver, Alfred E. (committee member).

Subjects/Keywords: Wind energy conversion; Variable ratio gearbox; Gearbox development; Optimal control; Multiobjective design

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APA (6^th Edition):

Hall, John Francis, 1. (2012). Design and control of a variable ratio gearbox for distributed wind turbine systems. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/ETD-UT-2012-08-6105

Chicago Manual of Style (16^th Edition):

Hall, John Francis, 1968-. “Design and control of a variable ratio gearbox for distributed wind turbine systems.” 2012. Doctoral Dissertation, University of Texas – Austin. Accessed February 28, 2021. http://hdl.handle.net/2152/ETD-UT-2012-08-6105.

MLA Handbook (7^th Edition):

Hall, John Francis, 1968-. “Design and control of a variable ratio gearbox for distributed wind turbine systems.” 2012. Web. 28 Feb 2021.

Vancouver:

Hall, John Francis 1. Design and control of a variable ratio gearbox for distributed wind turbine systems. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2012. [cited 2021 Feb 28]. Available from: http://hdl.handle.net/2152/ETD-UT-2012-08-6105.

Council of Science Editors:

Hall, John Francis 1. Design and control of a variable ratio gearbox for distributed wind turbine systems. [Doctoral Dissertation]. University of Texas – Austin; 2012. Available from: http://hdl.handle.net/2152/ETD-UT-2012-08-6105

20. -2932-5728. Modeling and control of drillstring dynamics for vibration suppression.

Degree: PhD, Mechanical Engineering, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/2872

► Drill-string vibrations could cause fatigue failure to downhole tools, bring damage to the wellbore, and decrease drilling efficiency; therefore, it is important to understand the… (more)

▼ Drill-string vibrations could cause fatigue failure to downhole tools, bring damage to the wellbore, and decrease drilling efficiency; therefore, it is important to understand the drill-string dynamics through accurately modeling of the drill-string and bottom-hole assembly (BHA) dynamics, and then develop controllers to suppress the vibrations. Modeling drill-string dynamics for directional drilling operation is highly challenging because the drill-string and BHA bend with large curvatures. In addition, the interaction between the drill-string and wellbore wall could occur along the entire well. This fact complicates the boundary condition of modeling of drill-string dynamics. This dissertation presents a finite element method (FEM) model to characterize the dynamics of a directional drill-string. Based on the principle of virtual work, the developed method linearizes the drill-string dynamics around the central axis of a directional well, which significantly reduced the computational cost. In addition, a six DOF curved beam element is derived to model a curved drill-string. It achieves higher accuracy than the widely used straight beam element in both static and dynamic analyses. As a result, fewer curved beam elements are used to achieve the same accuracy, which further reduces the computational cost. During this research, a comprehensive drill-string and wellbore interaction model is developed as the boundary condition to simulate realistic drilling scenarios. Both static and dynamic analyses are carried out using the developed modeling framework. The static simulation can generate drill-string internal force as well as the drilling torque and drag force. The dynamic simulation can provide an insight of the underlying mechanism of drilling vibrations. Top drive controllers are also incorporated as torsional boundary conditions. The guidelines for tuning the control parameters are obtained from dynamic simulations. Drill-string vibrations can be suppressed through BHA configuration optimization. Based on the developed modeling framework, the BHA dynamic performance is evaluated using vibration indices. With an objective to minimize these indices, a genetic algorithm is developed to optimize the BHA stabilizer location for vibration suppression. After optimization, the BHA strain energy and the stabilizer side force, two of the vibration indices, are significantly reduced compared to the original design, which proves the BHA optimization method can lead to a significant reduction of undesirable drilling dynamics. At the end of this dissertation, reduced order models are also discussed for fast simulation and control design for real time operation Advisors/Committee Members: Chen, Dongmei, Ph. D. (advisor), Djurdjanovic , Dragan (committee member), Beaman , Joseph (committee member), Longoria , Raul (committee member), Kinnas , Spyros (committee member).

Subjects/Keywords: Drilling vibration; Finite element method; Drillstring dynamics; Vibration suppression; Drill-string vibrations; Directional drill-string; Wellbore interaction model

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APA (6^th Edition):

-2932-5728. (2019). Modeling and control of drillstring dynamics for vibration suppression. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/2872

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Chicago Manual of Style (16^th Edition):

-2932-5728. “Modeling and control of drillstring dynamics for vibration suppression.” 2019. Doctoral Dissertation, University of Texas – Austin. Accessed February 28, 2021. http://dx.doi.org/10.26153/tsw/2872.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-2932-5728. “Modeling and control of drillstring dynamics for vibration suppression.” 2019. Web. 28 Feb 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-2932-5728. Modeling and control of drillstring dynamics for vibration suppression. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2019. [cited 2021 Feb 28]. Available from: http://dx.doi.org/10.26153/tsw/2872.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-2932-5728. Modeling and control of drillstring dynamics for vibration suppression. [Doctoral Dissertation]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/2872

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

21. Pehlivantürk, Can. Modeling, guidance, and control for cost conscious directional drilling.

Degree: PhD, Mechanical Engineering, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/1375

► Directional drilling has played an important role in the oil and gas industry. One of the challenges for directional drilling is its cost. In this… (more)

Subjects/Keywords: Directional drilling; Path optimization; Non-linear programming; Convex optimization; Advisory software; Vibration mitigation

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Pehlivantürk, C. (2019). Modeling, guidance, and control for cost conscious directional drilling. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/1375

Chicago Manual of Style (16^th Edition):

Pehlivantürk, Can. “Modeling, guidance, and control for cost conscious directional drilling.” 2019. Doctoral Dissertation, University of Texas – Austin. Accessed February 28, 2021. http://dx.doi.org/10.26153/tsw/1375.

MLA Handbook (7^th Edition):

Pehlivantürk, Can. “Modeling, guidance, and control for cost conscious directional drilling.” 2019. Web. 28 Feb 2021.

Vancouver:

Pehlivantürk C. Modeling, guidance, and control for cost conscious directional drilling. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2019. [cited 2021 Feb 28]. Available from: http://dx.doi.org/10.26153/tsw/1375.

Council of Science Editors:

Pehlivantürk C. Modeling, guidance, and control for cost conscious directional drilling. [Doctoral Dissertation]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/1375

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