Lightweight power converter for future electric aircrafts garners top prize for ECE researchers

ECE ILLINOIS researchers are making advancements in inverter designs for light-weight mobile systems such as aircraft and electric vehicles. In addition to mobile systems their work has potential to enable light-weight utility inverters which will reduce the cost of renewable energy installations.

Christopher Brandon Barth, an ECE ILLINOIS PhD student and research assistant in Professor Robert Pilawa-Podgurski research group, received the best paper award for the paper “Design and Control of a GaN-based, 13-level, Flying Capacitor Multilevel Inverter” which he presented this past June at the 2016 IEEE Control and Modeling of Power Electronics (COMPEL) Conference in Trondheim, Norway. The paper and research was completed jointly in collaboration with Thomas Foulkes, Won Ho Chung, Tomas Modeer, Pourya Assem, Yutian Lei and Professor Pilawa.

The prize paper details the research being supervised by ECE ILLINOIS Professor Robert Pilawa-Podgurski in the design of flying capacitor inverters for converting direct current to alternating current. Such converters are used in connecting renewable energy resources to the grid, and to drive electric motors in stationary and mobile applications. While conventional inverters are large and bulky through their heavily reliance on inductors and transformers, the paper presented a new circuit topology that leveraged the smaller size and lower weight of capacitors to perform the power conversion. By integrating state-of-the-art gallium nitride (GaN) transistors into the new converter architecture, the group was able to build an extremely light-weight inverter which offer a high “specific power density” (the ratio of power to weight). The weight of the power electronics is a key obstacle that must be overcome before hybrid and all electric airplanes are possible. The paper presents the design and hardware implementation of an 800 V, 3.1 kW prototype 13-level flying capacitor inverter which showcases the expandability of the architecture.

The group has diligently worked for the past year overcoming obstacles in regards to their research. “A lot of this project was implementation challenges. A concept that can be easy to design in theory or in a computer model, but to actually make it work in hardware can be a lot more difficult,” said Barth. “If something goes wrong in power electronics-it breaks, which means you need to start over.” To build a working prototype with excellent performance required careful attention to the circuit topology, mechanical integration, thermal management, electromagnetics modeling, as well as the development of sophisticated digital control algorithms.

“I was very pleased to see the students’ hard work being recognized, as it is a significant breakthrough in the size and weight of power converters at this voltage and power level” said Professor Pilawa. “In terms of switching frequency – one indication of the size reduction – this new prototype achieves an approximate increase of 100 over comparable state-of-the-art solutions in this space,” Pilawa continued. At the conference, the ECE Illinois researchers fielded questions from other experts on the details of how they were able to accomplish this. The recipe for success, according to Pilawa: “A few good ideas, many hours in the laboratory, and excellent teamwork.”

 COMPEL is the premier conference for those interested in the control and modeling of power electronics, with attendance by domain experts, who also review the papers. For this reason, the paper quality of accepted papers is very high. This year’s event was specifically focused on the stability of complex power electronics systems and the impact of converter control strategies on system stability. More information can be found on the COMPEL webpage.

COMPEL allows for engineering students, industry leaders, and researchers to meet and discuss the latest advancements in modeling, simulation, and circuits. It grants the engineering community an opportunity to learn from one another as well as applaud those who have excelled in their specific research areas. “Papers and conferences are one way to not only learn, but to also gain recognition for the things you have been doing,” said Barth.

This research was sponsored by NASA under the NASA Fixed Wing research and from the Power Optimization of Electro-Thermal Systems (POETS) NSF Engineering Research Center.