A Three-Level Auxiliary Resonant Commutated Pole Inverter for 800-V Electric Vehicle Powertrain

Shifting the electric vehicle (EV) bus voltage from 400 to 800 V has a major impact on EV inverters design. Three-level inverters are designed to cope with high battery voltage. Among three-level inverter topologies, the neutral point clamped (NPC) has better harmonic spectrum and lower semiconductor losses, which results in achieving higher power density and simpler cooling system. Nevertheless, in this topology, higher switching frequencies will result in more power losses in the inverter. The higher switching frequency capability enables the use of higher speed motors leading to overall reduction in the size of the electric drive system. This article proposes a new soft-switching NPC inverter in which a unidirectional auxiliary resonant commutated pole (ARCP) circuit assists commutation from the clamped diodes to the transistors and eliminates losses of this transition. In this topology, zero-current switching (ZCS) for all auxiliary switches and zero-voltage switching (ZVS) for main outer switches is achieved. Unlike the conventional transformer-assisted ARCP topologies, this structure does not utilize a saturable inductor to reset the transformer, which leads to a more compact design. Simulation and experimental results on a 3-kw prototype verify the effectiveness of the proposed topology in terms of achieving soft-switching.