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Title: A 2kW, High Power-Density (100W/in3), GaN-Based, Modular Multilevel Converter for Variable Speed Drive Applications in DC Systems

Authors: Ansel Barchowsky, Joseph Kozak, Brandon Grainger, Gregory Reed, and William Stanchina

Abstract: Achieving higher power-density for shipboard power conversion systems is extremely important for reduction of space requirements for electrical systems. This paper presents a single-phase, high power density inverter (450VDC, 2kW, 25in3) including design, analysis, and experimental testing, for variable speed drive applications. High-power density is achieved through the application of the modular multilevel converter (MMC) topology in a low voltage inverter system, which is enabled through the use of millimeter- scale, GaN HEMT devices. These devices exhibit lower conduction and switching losses, as well as having favorable thermal resistances. The MMC arms consist of 14 submodules, comprised of a half-bridge switched capacitance with two EPC2014C transistors (each 0.067in. x 0.039in.), and are mounted on a six-layer, double- sided, printed circuit board assembled with tight tolerances.

This work presents the fundamental design, Simulink/PLECS and finite element simulation, and hardware development for the high-density inverter system. The design and manufacturing challenges associated with this high-density inverter design, including motor control, low frequency voltage oscillation, and thermal considerations for the 0.548in2 submodules are addressed analytically and through simulation, and reflected by experimental milestones. The design is modular with the capability of achieving higher power ratings for varying naval ship applications.