ORNL’s Sangwhee Lee, right, receives the Best in Conference paper award for ITEC+2025 from conference chair Liang Du, left. Credit: ORNL, U.S. Dept. of Energy
For most researchers, submitting the first conference paper after earning a doctorate is a memorable moment. For Oak Ridge National Laboratory’s Sangwhee Lee, it was also a winning one. His debut paper earned one of the top three awards at a major international conference — the 2025 IEEE Transportation Electrification Conference & Expo + Electric Aircraft Technologies Symposium in Anaheim, California.
Out of more than 300 accepted papers, Lee’s work placed in the top 1% at this global gathering of transportation experts.
“This is the first paper I submitted since joining ORNL, and it was really exciting to see it recognized,” said Lee, who recently joined the lab full-time as a researcher in power electronics within the Energy Science and Technology Directorate. “It’s a proud moment and a great start to my career.”
New motor drive design improves performance and scalability
In the conference paper published in IEEE Xplore titled “Inverse Segmented Motor Drive Using Dual ANPC Inverters for Common-Mode Voltage and Neutral-Point Current Cancellation,” Lee and colleagues tackled two persistent challenges in multilevel power converters: neutral-point current and common-mode voltage. These electrical issues can lead to overheating, signal interference and premature wear on electric or hybrid motor components.
To manage these issues, engineers have traditionally relied on workaround solutions such as adding new hardware or modifying software. However, that approach increases the cost, weight and complexity of the overall system.
Instead, the team’s innovative motor drive design uses two inversely synchronized inverters to cancel out these unwanted effects at the system level, eliminating the need for extra hardware. With a simple modification to the motor winding configuration, the team demonstrated that the dual-inverter system can eliminate the problematic electrical signals entirely. In simulations, the proposed motor drive design reduced the neutral point voltage fluctuation by 90% and lowered current stress on the capacitors by 43%.
“This kind of system is how you scale up from electric or hybrid cars to heavy-duty trucks, marine vessels or even airplanes,” Lee said. “As we move toward more powerful applications, we need system-level solutions that are scalable, cost-effective and reliable.”
Because the solution requires only a small change to existing systems, it’s especially attractive for manufacturers looking to improve performance without costly redesigns.
Lee is quick to credit his co-authors and emphasize the collaborative nature of the work.
“I'm more on the circuit side. This would not have been possible without reconfiguring the motor, and my co-author Vandana [Rallabandi] helped a lot with that,” said Lee. “The team made the whole system work.”
Additional collaborators on the project include Gui-Jia Su; Shajjad Chowdhury, leader of the Electric Drives Research Group; and Burak Ozpineci, head of the Vehicle and Mobility Systems Research Section. “This was truly a team effort,” Lee said. “It’s a great example of how ORNL’s collaborative culture allows us to focus on the big picture, not just individual components.”
This technology was developed under the Vehicle Technologies Office.
UT-Battelle manages ORNL for the Department of Energy’s Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science. — Julya Johnson
