A 1200V DC-link Hybrid Si/SiC Four-level ANPC Inverter with Balanced Loss Distribution, $dv/dt$ and Cost

Abstract

To meet the aggressive performance targets of nextgeneration EV drivetrains, the traction inverter has been evolving by employing emerging technologies such as Silicon Carbide (SiC) devices and multilevel topologies. The four-level ANPC topology comprising six switches per phase has emerged as a promising solution for 1200V dc-link EV systems since its voltage balancing problem has been completely resolved by the latest control schemes. As the inherent property of this topology, the device power losses mainly concentrate on the two outer (primary) devices, which poses challenges to thermal management. This work proposes a hybrid Si/SiC configuration for this topology to achieve balanced overall performance. The SiC devices are adapted to combat the primary loss sources only, i.e. the two outer switches. Meanwhile, the other four switches staying as Si devices can offer additional benefits, on top of reduced cost, such as better loss/temperature distribution and reduced EMI and dv/dt issues. These benefits of the hybrid configuration are demonstrated in a comparative study with simulation and FEA thermal analysis. A prototype has been built and tested to validate the concept.