Doctoral Defense

Development of a gallium Nitride Based Current Source Inverter for Cryogenic Power Electronics Convrsion for Future Electric Aircrafts

Mustafeez-ul-Hassan

June 12, 2024
10:00 AM
Light Engineering, Room 250
Advisor:  Fang Luo

Challenged with the tasks of reducing CO2 emissions for existing and future propulsive systems, the aviation industry is taking long term and short-term measures. Innovative propulsive systems, as part of short-term strategy, comprise of hybrid electric aircraft, or full electric aircraft (FEA) which target at replacing the mechanical, pneumatic and other conventional systems with more electric, or fully electric systems. For FEA, researchers are focusing on utilization of low temperature on-board cryogenic system to store LH2, which will be used for fuel cell energy conversion. The concept of using LH2 was influenced by its being a highly efficient, safe and clean alternative source of energy; besides having significantly higher specific energy. The presence of an on-board cryogenic system enables the utilization of highly efficient superconducting transmission lines, machines, and cryogenic power electronics conversion systems (CPEC). Power electronics gets benefits from the concept of LH2 as a free cryogen as it basically is considered to operate superconducting machines, and converter runs as a by-product.

For the CPEC, multiple challenges exist, varying from selection of appropriate semiconductor device, filtering components, converter topology, controller design and integration of the whole system. In relation to it, this work focuses on the design and development of a fully cryogenic converter for FEA. A detailed review about semiconductor switching devices, passive filtering components, and CPEC developed, their advantages and drawbacks have been studied and analyzed. Secondly, efforts were spent towards the selection of the most suitable converter topology, from the perspective of size, efficiency, electromagnetic noise generation and compatibility with other system level components. Resultant converter topology: current source inverter was developed using commercially off the shelf components, which were characterized to numerous superconducting temperatures. The lowest characterization temperature achieved was 17 K. Lastly, the converter topology has been further optimized from the perspective of electrical performance and a second generation of fully cryogenic converter was developed. The converter developed is the first of its type, in terms of operating temperature, design considerations with state-of-the art specifications, and hence improved performance. The work concludes by giving a detailed analysis on the cryo vs non-cryo implementation of the converter, and other associated benefits.