The last years have seen an increasing need to reduce vehicle polluting emissions which has lead car producers to improve their efforts to comply with the new legislation. At the moment, hybrid electric vehicles (HEV) seems to be the most suitable solution as they match good performances in terms of both consumption and reliability. In a such dynamic market, an interest for small and light city-car is rising, especially in Europe, where urban circulation is getting worst due to huge number of vehicles. Such special characteristics, like smallness and lightness, allow these hybrid vehicles to run 40 km with a litre of fuel only.
In this scenario, the Hybrid and Electric Research Group of ENEA planned the realization of an hybrid power train suitable for small city car. The main target of the project, called “Urb-e”, is to realise a power train able to achieve low fuel consumption (2.5 litre/ 100 km), low emissions (comparable to EURO 5 rules), with simple configuration and low power train cost. To fulfil this target a hybrid series power train has been chosen.
In particular, during this phase the goal of project is to realize and to calibrate a power management system able to satisfy the requested performances (power, max speed, acceleration, etc.). The difficulty is due to the use of ultracapacitors (UC) as energy storage system because of the low energy capacity. In order to achieve this goal, different control strategies are tried to manage the auxiliary power unit (APU). The principal aspects of the power management system are shown. Some driving tests results are finally reported to instance the effectiveness of the developed management.