Sizing of power storage and conversion components in a hybrid electric propulsion system for advanced air mobility

Abstract

The electric vertical take-off and landing (eVTOL) aircraft will change the future of transportation. This will happen when the pulse-power modes during the vertical flight which needs about 4 to 6 times higher power, are treated appropriately. This paper addresses the design and simulation of hybrid electric propulsion systems that could deliver power for a practical flight envelope. The paper proposes a generic design cycle with realistic modeling of component dynamics to match a combination of power storage, engine-generator, and axial flux motor with a multi-propeller configuration. To solve this system design problem, a hybrid battery-ultracapacitor-generator architecture combines high energy density from battery, high power density from ultracapacitor, and range extension by engine-generator. This unified design includes a pulse-load-optimized sizing process tailored to eVTOL operational profiles and reduces C-rate peak while providing the energy needed for flight endurance. This is realized by integration of an interleaved non-inverting buck-boost converter which is designed based on hover requirements and maximum C-rate per DC bus voltage. The performance of proposed converter in maximum inductor current and voltage gain evaluated by comparative simulations on 400 distinct voltage combinations under optimal soft-switching operation. The results show that the battery lifetime and specific power storage are successfully addressed.