Modelling of Electrical Powertrains

Modelling of the current and voltage fluctuations caused by the power electronics in the high-voltage on-board network and analysis of the effects of current and voltage ripple on the on-board network in the form of additional losses or loads of filters.


The need for minimization of (fossil) fuel consumption and local emissions in personal transportation has led to a significant interest in drive train electrification. This trend is not limited to the hybridization or complete electrification of the motor itself but also extends to major auxiliaries either due to the lack of an internal combustion engine in all-electric vehicles or in order to further improve fuel efficiency.

With all components connected to a central dc-link with voltages of several hundred volts, the interaction of all kinds of different loads attracts significant attention during development of an electric powertrain. Detailed simulation models of the complete drive train are used in order to assess powertrain efficiency, driving performance as well as voltages levels and current flows for different driving conditions. Such simulations models subsequently focus on dynamics in the range of seconds (e.g. longitudinal dynamics) or even minutes (e.g. battery state of charge).

However, such simulation models do not account for high frequency variations of voltages and currents which result from the virtually instantaneous switching of load currents in power electronics, such as the drive inverter or DC/DC converters. As such variations might interference with component controllers, cause additional losses and therefore require extensive filtering, a priori analysis of high frequency harmonics becomes increasingly important.

Time constants

This project aims to set up an experimentally validated simulation model of a complex electric drive train focusing on dynamics in the frequency range from 100 Hz up to several dozens of kilohertz. This includes the mathematical modelling of voltage and current ripples caused by switching in power electronics depending on the chosen modulation schemes and drive train configuration. Based on the simulation model, the relevance of high frequency harmonics in terms of additional losses and filter requirements will be analyzed.

  • C. Sagert, M. Walter & O. Sawodny, “DC/DC Converter Control for Voltage Ripple Reduction in Electric Vehicles”, IEEE Conference on Advanced Intelligent Mechatronics, Banff, Kanada, 2016
  • C. Sagert, F. Bender & O. Sawodny, “Electrical drive train modeling for model predictive control of DC-DC converters in fuel cell vehicles”, American Control Conference (ACC), Chicago, IL, USA, 2015, pp. 4333-4338, doi:10.1109/ACC.2015.7172010
  • C. Sagert, M. Walter, S. Fandel & O. Sawodny, “Sizing Electrical DC Link Capacitors in Complex Electriv Powertrains”, IFAC Workshop on Engine and Powertrain Control, Simulation and Modeling, Columbus, USA, 2015, pp. 230-236, doi:10.1016/j.ifacol.2015.10.033


This work was partly funded by the Promotionskolleg Hybrid, a cooperation of the state of Baden-Wuerttemberg, Daimler AG and Bosch.


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