Modeling, Measurement, and Evaluation of the DC Bus Current Ripple in Electric Vehicles

Abstract

The semiconductor switching of traction inverters produces a current ripple overlaying the dc current in the high-voltage dc bus of an electric vehicle (EV). Recent studies show that a current ripple accelerates the aging of the traction battery. Battery aging studies are time-consuming and cost-intensive, and reliable results require a comprehensive study of the current ripple and its occurrence in the mission profile of an EV. Therefore, this article presents a fast and accurate simulation model that derives the battery current ripple for a mission profile of an EV. It is validated with measurements using an automotive test bench at different operation points. The simulation model consists of three different levels. At the inverter level, extensive parameter sweeps show the respective impact on the current ripple. At the powertrain level, the current ripple of the operation points is mapped on a torque-speed plane considering the control scheme of the motor. The vehicle level weights the operation points according to their occurrence in a driving cycle. A criterion is established to compare the impact of the current ripple on the battery degradation. This enables an evaluation of 400- and 800-V dc bus architectures as well as the replacement of Si IGBTs with SiC MOSFETs.