System design of the electric powertrain of hybrid electric distribution vehicles

Author: Johannes Maiterth
Dipl.-Ing. Peter Methfessel, VKA, RWTH Aachen University,
Dr.-Ing. Edoardo Pietro Morra, FEV GmbH, Aachen

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In the European Union trucks, busses and coaches produce around 25 % of the CO2-emissions from road transport. Because of increased road freight traffic, the CO2-emissions rose by 36 % between 1990 and 2010. Therefore, it is planned to also limit and certify the CO2-emissions of new heavy duty vehicles (HDV). One solution to reduce the CO2-emissions of a HDV is to electrify the powertrain. Depending on the driving cycle, different fuel consumption improvements can be achieved with electrification of the powertrain. For a series hybrid bus, up to 33 % of improvement has already been demonstrated. For the fleet operator the potential fuel savings that can be achieved with an alternative powertrain on a daily route is crucial for the selection of the right type of vehicle. For the vehicle manufacturer knowledge about the expected driving cycles is important to size the powertrain parameters appropriate. Hence, different aspects have to be considered when designing hybrid powertrains. To exemplify an advanced development approach, considering the requirements of, both, the operator and the OEM to find a best cost/benefit solution, this paper demonstrates the optimization of an electric powertrain for a hybrid electric distribution vehicle. All components of the electrical powertrain, like high-voltage battery and electric machine are scalable in the simulation model. By means of design of experiments, not only a best compromise between fuel consumption and cost will be determined, but also the requested vehicle performance targets like acceleration from 0 to 50 km/h and climbing capacity will be taken into account. The simulation study will compare the results of a conventional powertrain on at least two different typical routes with a series hybrid and parallel hybrid powertrain.