High Power Density Flying Capacitor Multilevel Inverter for Electric Aircraft with a Stacked PCB Interleaved Hybrid Commutation Loop Design

Drivetrain efficiency and weight represent significant barriers toward the development of future electric aircraft. Multilevel inverter designs have demonstrated high performance in these applications. The flying capacitor multilevel converter (FCML), in particular, has shown promise. It achieves very high efficiency due to its low-voltage, high figure-of-merit devices, and very low weight due to its reduced output filter size and reliance on capacitive energy storage. FCMLs contains many active devices with associated gate drive circuitry. In order to achieve simultaneous goals of high density, high efficiency, and good signal integrity, the layout of the converter is of utmost importance. In this work, a stacked PCB design is presented, which shields the low-voltage gate signals from interference, while also enabling an uninterrupted power path, low commutation loop inductance, and compact volume. A 400 V, 3.6 kW, 8-level FCML prototype is fabricated, which achieves > 50 kW/kg specific power, > 2 kW/in
³
power density and 98.1 % peak efficiency.