University of Kentucky UKnowledge Theses and Dissertations--Electrical and Computer Engineering Electrical and Computer Engineering 2021 Electric Power Systems and Components for Electric Aircraft Damien Lawhorn University of Kentucky, [email protected] Author ORCID Identifier: https://orcid.org/0000-0002-3642-3983 Digital Object Identifier: https://doi.org/10.13023/etd.2021.134 Right click to open a feedback form in a new tab to let us know how this document benefits ou.y Recommended Citation Lawhorn, Damien, "Electric Power Systems and Components for Electric Aircraft" (2021). Theses and Dissertations--Electrical and Computer Engineering. 163. https://uknowledge.uky.edu/ece_etds/163 This Doctoral Dissertation is brought to you for free and open access by the Electrical and Computer Engineering at UKnowledge. It has been accepted for inclusion in Theses and Dissertations--Electrical and Computer Engineering by an authorized administrator of UKnowledge. 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I also retain the right to use in future works (such as articles or books) all or part of my work. I understand that I am free to register the copyright to my work. REVIEW, APPROVAL AND ACCEPTANCE The document mentioned above has been reviewed and accepted by the student’s advisor, on behalf of the advisory committee, and by the Director of Graduate Studies (DGS), on behalf of the program; we verify that this is the final, approved version of the student’s thesis including all changes required by the advisory committee. The undersigned agree to abide by the statements above. Damien Lawhorn, Student Dr. Dan M. Ionel, Major Professor Dr. Daniel L. Lau, Director of Graduate Studies Electric Power Systems and Components for Electric Aircraft DISSERTATION A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College of Engineering at the University of Kentucky By Damien Lawhorn Lexington, Kentucky Director: Dr. Dan M. Ionel, Professor and L. Stanley Pigman Chair in Power Lexington, Kentucky 2021 Copyright© Damien Lawhorn 2021 https://orcid.org/0000-0002-3642-3983 ABSTRACT OF DISSERTATION ELECTRIC POWER SYSTEMS AND COMPONENTS FOR ELECTRIC AIRCRAFT Electric aircraft have gained increasing attention in recent years due to their po- tential for environmental and economic benefits over conventional airplanes. In order to offer competitive flight times and payload capabilities, electric aircraft power sys- tems (EAPS) must exhibit extremely high efficiencies and power densities. While advancements in enabling technologies have progressed the development of high per- formance EAPS, further research is required. One challenge in the design of EAPS is determining the best topology to be em- ployed. This work proposes a new graph theory based method for the optimal design of EAPS. This method takes into account data surveyed from a large set of refer- ences on commonly seen components including electric machines, power electronics and jet engines. Thousands of design candidates are analyzed based on performance metrics such as end-to-end system efficiency, overall mass, and survivability. It is also shown that sensitivity analysis may be used to systematically evaluate the impact of components and their parameters on various aspects of the architecture design. Once an EAPS architecture has been selected, further, detailed, validation of the power system is required. In these EAPS, many subsystems exist with timescales varying from minutes to hours when considering the aerodynamics, to nanosecond dynamics in the power electronics. This dissertation presents a multiphysics co- simulation framework for the evaluation of EAPS with a unique decoupling method to reduce simulation time without sacrificing detail. The framework has been exemplified on a case study of a 500kW all-electric aircraft, including models for aerodynamics, energy storage, electric motors and power electronics. Electric machines for aviation propulsion must meet several performance require- ments, including a constant power speed range (CPSR) of approximately thirty per- cent above rated speed. This operation is traditionally achieved through the flux weakening technique with an injection of negative d-axis current. However, the de- gree of CPSR achievable through flux weakening is a strong function of the back emf and d-axis inductance. This dissertation reviews alternative methods for CPSR operation in machines with low inductance. A new method of current weakening has been proposed to address this challenge, involving reducing the machine's current inversely proportional to the operating speed, maintaining constant power through the extended speed range. One benefit of the proposed method is that all current is maintained in the q-axis, maintaining maximum torque per ampere operation. Coreless axial flux permanent magnet (AFPM) machines have recently gained significant attention due to their specific form factor, potentially higher power density and lower losses. Coreless machine designs promise high efficiency particularly at higher speeds, due to the absence of a ferromagnetic core. In this dissertation, coreless AFPM machines with PCB stators are investigated as candidates for propulsion in electric aircraft applications. Two PCB stator design variations are presented with both simulation and experimental results. KEYWORDS: Electric aircraft, power system optimization, co-simulation, electric machine drives, PCB stator, axial flux permanent magnet. Author's signature: Damien Lawhorn Date: May 11, 2021 Electric Power Systems and Components for Electric Aircraft By Damien Lawhorn Director of Dissertation: Dr. Dan M. Ionel Director of Graduate Studies: Dr. Daniel Lau Date: May 11, 2021 To my father ACKNOWLEDGEMENTS First and foremost, I would like to express my upmost gratitude to my advisor, Professor Dan M. Ionel, Ph. D., FIEEE, L. Stanley Pigman Chair in Power, who has always supported me in academic, professional, and personal growth. Since I took his electric class on Electric Vehicles { Electromechanical Components and System and then joined the SPARK Laboratory, he never wavered to provide his wisdom and guidance to help me pursue my goals. The many hours he has spent with me planning, discussing, and reviewing my work have been invaluable to shaping this dis- sertation. Under his caring mentorship, I was able to learn how to navigate research, collaboration, and even daunting tasks, as well as what "more and better" may help you achieve. The service that he done for me, not only for directing my PhD studies with dedication and foresight, but also for always believing in me and my potential for success is a debt that I will never be able to repay. I am grateful for all of his many teachings over the past four years, and how they will be valued utilities in the coming years as a professional. I am thankful to him not only for encouraging me to pursue my Ph.D., but for providing me with an atmosphere that fostered growth while doing so. I am very grateful to Dr. Vandana Rallabandi, an outstandingly knowledgeable mentor with whom I was fortunate to work during her postdoctoral fellowship with the SPARK laboratory. I am proud to count her a close friend. I would also like to thank all my colleague students in our SPARK Laboratory and academic family for their friendship and collaboration. iii The support during my Ph.D. studies by the National Aeronautics and Space Administration (NASA) and the Kentucky Space Grant, directly at University of Kentucky (UK) as a NASA Graduate Fellow during the academic years, and through summer internships at the NASA Glenn Center, is gratefully acknowledged. My great appreciation is also due for the support of University of Kentucky, the L. Stanley Pigman endowment, Regal Beloit Corp., and ANSYS, Inc. At UK, I am thankful to all my professors, and especially to the internal electrical engineering Ph.D. Committee members, Professors Aaron Cramer, James Lumpp, and Joseph Sottile. I am also very thankful to my mentors at NASA and in industry. At the NASA Glenn Research Center, Mr. Ralph Jensen, advised my research on aircraft power system optimization and supported my Graduate Fellowship grants and summer internships, and Dr. David Avanesian and his team, mentored me on the development of motors and drives for electric aircraft. Dr. Greg Heins of Regal Beloit Corp. provided invaluable technical advice on practical design and prototypes, as well as provided specialized hardware components. At ANSYS, Dr. Xiao Li guided my summer internship before the PhD studies, and over the years provided technical insights on system modeling. Mr. and Mrs. Stanley and Karen Pigman have mentored, financially sponsored, and included me in the large group of Pigman Scholars. I am most grateful to them for supporting me personally, as well as for everything they do for our group at University of Kentucky. I would like to thank my parents, Patrick Lawhorn and Tara Mayes, who always encouraged me to chase my dreams and taught me to value kindness, honesty, and diligence. They pushed for me to become the best version of myself and were there to iv hold me up every step of the way.