Energy efficiency improvement of intelligent fuel cell/battery hybrid vehicles through an integrated management strategy

This paper investigates an integrated energy management strategy (IMS) to improve energy efficiency of proton exchange membrane fuel cell (FC) system in intelligent fuel cell/battery hybrid vehicles (FCHVs). Unlike other similar works which solely control output current from the FC system, stack temperature regulation is added in this research due to its impact on FC output power performance. For liquid-cooled FC systems, joint management of FC current and stack temperature is more difficult than air-cooled FC systems due to complicated thermal management systems. To address this, firstly, a control-oriented integrated model is established to provide the foundation for controller design. For the purpose of decreasing the strong nonlinearity of integrated model, the heat generation term is parameterized with a polynomial function. Secondly, in order to determine reference trajectories for controller, a data set consisting of nearly optimal operation points (FC current and stack temperature) is constructed offline, which provides reference trajectories based on simple rules in real time. Finally, a contraction-based control (CBC) approach is utilized to regulate FC current and stack temperature jointly. The bounded convergence between system states and reference trajectories is guaranteed by contraction theory. The effectiveness of the proposed IMS is validated via MATLAB simulation.