Inverter and Battery Drive Cycle Efficiency Comparisons of Multilevel and Two-Level Traction Inverters for Battery Electric Vehicles

This paper investigates the drive cycle performance of different multilevel and two-level inverters. For the multilevel inverters, a cascaded H-bridge (CHB), a modular multilevel series parallel (MMSP) and a battery modular multilevel management (BM3) inverter are considered. The inverter and battery efficiency during the WLTP-driving cycle are estimated based on loss models. The battery loss model is derived from an electrochemical impedance spectroscopy of a cylindrical 18650 Li-ion battery cell. The inverter losses are modeled using the semiconductors’ data sheets and a thermal equivalent circuit. In comparison to the two-level inverter system, the CHB and the MMSP inverter drivetrains show an increased inverter efficiency, despite increased battery losses. In contrast to the CHB and the BM3 topologies, the MMSP inverter shows less battery losses. The BM3 inverter shows acceptable drive cycle efficiency while having the lowest inverter costs.