Design and manufacturability of a high power density M2C inverter

The modular multilevel converter (M2C) circuit, a voltage source converter originally introduced to reduce the footprint of high voltage DC systems, is adapted here for a single-phase, low voltage, high power density inverter application (450 V
_DC
, 2 kW, 100 W/in
³
). The adaptation is achieved by using small, high speed gallium nitride (GaN) transistors in the M2C half-bridge submodules that are stacked in series and parallel to achieve voltage and current requirements. Here the design and analysis of an individual half-bridge cell, and full arm of the M2C topology is presented. To achieve such high power density, factors including gate drive circuit design, submodule electrical performance and thermal management, and the manufacturability of the full arm were considered. This work presents the detailed process of designing and manufacturing the multiple printed circuit boards, as well as thermal and electrical experimental evaluation and analysis. The stringent size and operational requirements drove design iterations between circuit designers and manufacturers.