Test methods for electric heavy-duty drivetrains based on multiphysical hardware-in-the-loop test benches

eTestHiL project logo Copyright: © RWTH

Electrically driven commercial vehicles are an important step on the way to sustainable mobility. Depending on the use of the vehicles, the requirements differ significantly. However, all vehicles share the need for a rapid market ramp-up and short development times. System tests carried out early in the development process allow a review and optimization of the development goals on an ongoing basis, which accelerates the overall process.

Within eTestHiL, test methods are developed that allow the development, construction and subsequent testing of electrified heavy-duty drives. Hardware-in-the-loop (HiL) test benches provide a realistic representation of the overall system behavior, which is directly included in the development process of the various components.

The test methods found in the project will be validated by developing an electric powertrain and chassis for heavy-duty trucks. A prototype will be developed and built by the Institute for Automotive Engineering (ika) of RWTH and tested in the HiL test benches of the project partners Leadrive Technology Germany GmbH and BPW Bergische Achsen KG. At the Institute for Machine Elements and Systems Engineering (MSE) of RWTH Aachen University, a 1 MW dynamometer gets modernized to enable testing of this drive unit as well as heavy electric vehicle drives in general.

  Schematic testbench overview Copyright: © RWTH

PGS develops a modular DC/DC converter system for the 1 MW test bench consisting of four converters with two galvanically isolated modules each. The converters are designed to work as a battery emulator, enabling the testing of electric drive trains without battery. Here, the converters connect on the primary side to the existing DC link of the test bench, to which the load machines are also connected. The motor inverters of the DUT connect to the secondary side. This creates a circular power flow during test operation, with only losses drawn from the grid.

To realize a versatile test bench, the converters must be able to emulate different battery systems. This requires a wide secondary-side voltage range. Due to the modularity of the inverters, a series or parallel connection of the secondary sides is possible. The parallel connection of two modules allows high current at low system voltages, while the series connection shown in the figure enables the emulation of high battery voltages. On the primary side, the modules are connected in series due to the constant DC link voltage of the test bench.

The series connection of both primary and secondary side of each module in combination with bidirectional power flow presents a control engineering challenge. Based on the research findings on previous modular converters (, we develop control concepts that will find application in the system context at high power levels for the first time.

The project partner ebusplan supports us in the development of the battery emulation. Modified traction converters from project partner Leadrive are used to validate the control concept.

MSE is coordinating the three-year project. Further information is available at

Funding code: 01MV22021A