Sustainable mobility is a pressing challenge for modern society. Electrification of transportation is a key step towards decarbonization, and hydrogen Fuel Cell Hybrid Electric Vehicles (FCHEVs) offer a promising alternative to Battery Electric Vehicles (BEVs), especially for long-range applications: they combine a battery system with a fuel cell, which provides onboard electric power through the conversion of hydrogen. Paramount importance is then given to the design and sizing of the hybrid powertrain for achieving a compromise between high performance, efficiency, and low cost.
This work presents a Hardware-in-the-Loop (HIL) platform developed for designing and testing the powertrain layout of an FCHEV. The platform comprises two systems: a simulation model reproducing the dynamics of a microcar and a hardware system for the fuel cell hybrid electric powertrain. The former simulates the vehicle's behavior, while the latter is composed of a 2kW real fuel cell stack and a 100Ah Li-ion battery pack. This element is used for real-time testing of the hybrid powertrain, using a programmable power supply that emulates the vehicle and motor load request.
Two fuel cell stack configurations have been analyzed by applying a linear scale-up approach (2kW and 4kW) and tested on an acceleration and deceleration driving cycle, representative of the microcar application; a simple fuzzy logic control strategy has been chosen for the test.
The system's performances have been evaluated and deeply analyzed in terms of component behavior and energy efficiency. The results demonstrate that the 4kW stack configuration scores a nearly 5% higher efficiency than the 2kW stack, mainly operating in the lower current regions corresponding to higher efficiencies. The improvements can then be translated into an increase in the vehicle's estimated range, more than balancing the increased weight burden of nearly 10kg. By enabling the possibility to consider and test the real behavior of powertrain components, the HIL platform has proven to be an effective tool for design purposes.