Investigation of a fuel cell hybrid system with a new modular test bench approach for all electric hybrid power train systems

Abstract

In order to reduce the impact of aviation on climate, new technologies like fuel cell and battery hybrids are needed. To develop a hybrid electric aircraft, a flexible and adaptable laboratory test setup of the power train is a cost- and time-effective solution. Replacing the fuel cell and battery with DC sources simplifies the setup, but the characteristics of the fuel cell and the battery must be reproduced. This study presents a test setup for direct hybrid electric power trains with an emulated fuel cell and battery. Two DC (Direct Current) sources are controlled with the help of a database to mirror the behavior of the fuel cell and battery. The setup allows the investigation of the drive train behavior of a direct hybrid consisting of a variety of fuel cells and batteries. The hybrid behavior for different battery state of charge as well as different battery sizes are examined their the influence on the voltage variation within the system is analyzed. The more the fuel cell contributes to the hybrid power, the greater the voltage difference within the entire system. A higher power contribution from the battery reduces the system voltage variation at high power. At a rated power of 5kW, the voltage variation is lowered by 37.2% when the fuel cell share is reduced from 90% to 50%. A lower state of charge of the battery increases the voltage variation.