Hybrid Five-Level Active Neutral Point Clamped Inverter for Electric Aircraft Propulsion Drives

Medium voltage dc system is a promising technology to significantly improve the efficiency and power density of electric aircraft propulsion drives. In this paper, a five-level active neutral point clamped (5L-ANPC) topology is selected as the inverter for the propulsion drives, due to its higher voltage capability and lower output harmonics as well as reduced common-mode voltage. To meet the high-speed requirement of the aircraft propulsion drives and to boost the efficiency and power density of the inverter, Silicon Carbide (SiC) semiconductor devices are considered for the 5L-ANPC inverter. However, the large commutation loop associated with some of the switching states of the inverter prevent configuring all the switches as SiC devices. As a result, a hybrid "Si+SiC" five-level ANPC inverter and a synchronous optimal pulse width modulation strategy are developed, in which the SiC devices are only used for the switches at the ac output side and the rest of the switches are configured with Si IGBTs. This hybrid ANPC inverter concurrently achieves high efficiency and low implementation cost, at high-speed operation mode. Thermal modeling and simulation results are presented to verify the performance of the proposed hybrid inverter.