Impact of future 48 V-systems on powertrain operation under real-driving conditions

48 V-hybrid drives represent a cost-efficient technology that can significantly reduce the fuel consumption of passenger cars, while requiring limited integration effort. To achieve the maximum benefit with a 48 V-system while maintaining low overall system costs, a detailed understanding of the relations between conflicting optimization goals such as efficiency, comfort and cost, especially under real-driving conditions, is essential. This paper analyzes this conflict in a 48 V-system with P2 topology, where the optimization goals are represented by CO2 emissions (efficiency), engine start frequency (comfort) and effective battery load (component cost). Characteristic real-driving scenarios are investigated using a longitudinal-dynamics simulation model. An ECMS operating strategy (OS) is implemented and control parameters are defined in order to manipulate the conflicting goals. The results reveal the sensitivity of OS parameters to conflicting optimization goals. The relationship between optimization goals is identified through Pareto fronts. Pareto optimal solutions are selected for each scenario using weighting factors. Finally, the effects of different Pareto solutions on the powertrain operation in terms of the distribution of ICE-off duration are identified.