Modeling and analysis of transient behavior of polymer electrolyte membrane fuel cell hybrid vehicles

The paper focuses on the simulation of a hybrid vehicle with proton exchange membrane fuel cell as the main energy conversion system. A modeling structure has been developed to perform accurate analysis for powertrain and control system design. The models simulate the dynamics of the main powertrain elements and fuel cell system to give a sufficient description of the complex interaction between each component under real operating conditions. A control system based on a multilevel scheme has also been introduced and the complexity of control issues for hybrid powertrains have been discussed. This study has been performed to analyze the energy flows among powertrain components. The results highlight that optimizing these systems is not a trivial task and the use of precise models can improve the powertrain development process. Furthermore, the behavior of system state variables and the influence of control actions on fuel cell operation have also been analyzed. In particular the effect of introducing a rate limiter on the stack power has been investigated, evidencing that a 2 kW/s rate limiter increased the system efficiency by 10% while reducing the dynamic performance of the powertrain in terms of speed error.