Efficiency Evaluation of 2L and 3L SiC-Based Traction Inverters for 400V and 800V Electric Vehicle Powertrains

Abstract

This paper presents an efficiency evaluation of three silicon carbide (SiC) inverter topologies: two-level (2L) voltage source inverter (VSI), 3L neutral-point clamped (NPC), and 3L T-type inverter. Their efficiency is evaluated for powertrains rated at 400 V and 800 V, and using SiC MOSFET devices rated at 650 V and 1200 V operating at a switching frequency of 30 kHz. Firstly, the efficiency is evaluated at different operating load currents, on a per-unit scale. Secondly, the efficiency curves are mapped into torque-speed 2D maps of 120 kW interior permanent magnet (IPM) motors. Thirdly, the resulting efficiency maps are employed in an electric vehicle (EV) model, in order to study the performance of the three inverters on standard drive cycles. At the vehicle level, the energy consumption of the vehicle using the studied inverters is analyzed. It is found that 3L SiC-based inverters are most competitive in the 800 V powertrain. When compared to VSI, NPC and T-type offer 0.6% and 1.2% energy consumption savings. In 400 V, only T-type enjoys 0.9% energy savings over VSI.