Conceptual Study on Dc-Dc Converter Topologies in Battery-Fuel Cell Electric Aircraft Propulsion

The propulsion system architectures of all-electric aircraft often rely on multiple energy sources, in particular hydrogen-based fuel cells and batteries, to accommodate varying power demands throughout a mission profile. In this study, the source-side architecture for electric aircraft propulsion was investigated, focusing on the integration with power management and distribution systems. A two-port configuration with dual active bridge converters and a multi-port topology utilizing a triple active bridge converter were compared. Through the analysis of a hydrogen-based regional aircraft mission profile, the performance of each converter was assessed for the relevant mission phases. The topologies were evaluated in terms of efficiency, power density and control complexity. Semiconductor and transformer losses were calculated to assess system efficiency, utilizing thermal models and analytical methods. An existing sizing approach was extended to include transformer design, enabling the evaluation of volumetric and gravimetric power density. The preliminary design results in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$22.7 \text{kW} / \text{kg}$</tex> for the three-port architecture, which is slightly higher than the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$21.9 \text{kW} \text{kg}$</tex> for the two-port architecture. Depending on the mission phase, either the dual active bridge or the triple active bridge would be more advantageous. Additionally, complexity and control considerations for the evaluated converter systems were addressed in this paper, offering insights into the key characteristics and trade-offs for electric aircraft propulsion concepts.