Hardware-in-the-Loop Testing of Electric Traction Drives with an Efficiency Optimized DC-DC Converter Control

In order to reduce development cost and time, frontloading is an established methodology for automotive development programs. With this approach, particular development tasks are shifted to earlier program phases. One prerequisite for this approach is the application of Hardware-in-the-Loop test setups. Hardware-in-the-Loop methodologies have already successfully been applied to conventional as well as electrified powertrains considering various driving scenarios. Regarding driving performance and energy demand, electrified powertrains are highly dependent on the dc-link voltage. However, there is a particular shortage of studies focusing on the verification of variable dc-link voltage controls by Hardware-in-the-Loop setups. This article is intended to be a first step towards closing this gap. Thereto, a Hardware-in-the-Loop setup of a battery electric vehicle is developed. The electric powertrain consists of an interior permanent magnet synchronous machine and an inverter, which are set up as real components at a laboratory test bench. The test bench is connected to a real-time vehicle simulation including a battery model and the dc-dc converter model. The entire Hardware-in-the-Loop setup is successfully validated by vehicle measurements performed on a chassis dynamometer. Thereafter, the battery electric vehicle is tested at this Hardware-in-the-Loop setup for the worldwide harmonized light vehicle test cycle class 3. The tests are performed for electric powertrain configurations with and without dc-dc converter. For the application with dc-dc converter, reductions in energy losses of the traction machine by 5.4% and of the traction inverter by 37.6% are determined. This leads to an efficiency improvement of the entire electric powertrain by 1.5 percentage points, which results in a total energy reduction by 0.28 kWh/100km for the investigated test cycle. This use case demonstrates the efficiency improvements of a variable dc-link voltage and how Hardware-in-the-Loop tests can support the verification of dc-dc converter controls during frontloading phases of automotive development programs.