Abstract
Hybrid-electric vehicles (HEVs) constitute an interesting evolution of conventional road vehicles, since they can exhibit significant efficiency and emissions improvements by employing existing or emerging technologies. Nevertheless, these improvements can be achieved, at a reasonable cost, only by carefully designing and matching the powertrain configuration and the energy management strategy adopted. Moreover, it was experimentally demonstrated that a suitable management strategy can also prolong the useful life of particularly sensitive and expensive devices, such as electrochemical accumulators, usually employed in HEVs. Keeping in mind the complexity of HEVs structures, it results so very useful to employ a reliable simulation program that allows to study different solutions at design stage, allowing to analyze, also in dynamic terms, the main vehicles behavior aspects. For this purpose, University of Pisa and Enea started a joint program for the development of a modular HEVs simulator, named Hy-Sim, operating within the Matlab/Simulink environment. This paper describes the structure of this simulator, that was developed to mainly permit the power and energy performance evaluation of different powertrain configurations and management strategies keeping into account the functional limits and features of the different components involved. Simulation results are reported, referring to the study of an improved energy management strategy for an existing experimental metropolitan stock transportation HEV; moreover, corresponding experimental results are reported, comparing and commenting them.