This event is free and does not require registration. Please feel free to share the link with colleagues and students.

Where: Online via Zoom

When: Wednesday, August 6, from Noon to 1 p.m. (EDT)

Topic: Megahertz Power Conversion for Lightweight and Power Dense Applications

Presenter: Dr. Kristen Booth

Dr. Kristen Booth is an Assistant Professor at the University of South Carolina where she is researching the codesign of power electronics and power systems. She became a Joint Appointee with Savannah River National Laboratory in 2022, and previously, she was a Postdoctoral Researcher at The Ohio State University in the Center for High Performance Power Electronics (CHPPE). As an NSF Graduate Research Fellow, Dr. Booth completed her Ph.D. degree from North Carolina State University in 2019. She graduated from NCSU with an M.S. in Electrical Engineering in 2017 and received a B.S.E. in Engineering Physics in 2015 from Murray State University. Dr. Booth’s research interests include resiliency and reliability of power electronics converters, AI-integrated power electronics, and digital twins for grid modernization and security.

Abstract: Empty weight of a vehicle refers to the total weight of its structure and operating equipment without passengers or payload. For aerospace applications, empty weight, center of gravity, and flight planning are coordinated to determine the feasibility of a flight. By reducing empty weight, the economics of short-duration flights, such as electric Vertical Takeoff and Landing (eVTOL) aircraft, can be improved by replacing existing equipment weight with payload. While power electronics alone cannot improve energy storage weight, reasonable reduction in the islanded microgrid structure is valuable to adding payload as center of gravity can be shifted outside of a narrow tolerable range, causing instability in transitions from hovering to cruise.

A GaN-based, 1-MHz, 5-kW LLC resonant converter has been experimentally verified for eVTOL battery energy storage systems. This initial prototype focuses on the challenges megahertz operation, including radiated EMI from high slew rates while pushing the GaN devices to the edge of safe operating conditions. This seminar addresses these challenges through the design, modeling, and experimental validation of power converters operating at 1 MHz. Key techniques include a method to accurately determine dead time for soft switching based on GaN output charge behavior, the use of a PCB-integrated transformer to reduce volume and improve power density, and a thermal impedance network to estimate internal temperature rise under forced convection. The temperature dependence of GaN is also characterized to improve the conduction loss prediction. This converter weighs less than a pound, has a power density of 40 kW/L, and transfers the largest reported power at 1 MHz to date. The results demonstrate practical design methods to overcome switching, thermal, and integration challenges in higher-frequency and higher-power converters using commercially available components.