Design, Operation, and Loss Characterization of a 1-kW GaN-Based Three-Level Converter at Cryogenic Temperatures

This article investigates the potential for high power density, high-efficiency power conversion using GaN-based flying capacitor multilevel power converters at low temperature. Specific focus is given to the application of hybrid aircraft powered by liquefied natural gas. Building off of prior characterization of GaN switches over temperature, this article outlines the impact of near-cryogenic operation on the losses of a complete 1-kW inverter. Specific focus has been given to the characterization of the losses in ceramic capacitors and inductors at near-cryogenic operation. A 1-kW GaN-based three-level power converter was designed and successfully tested from room temperature down to -140 degrees C. Along with the first demonstration of a flying capacitor multilevel converter and associated components at such low temperature, a breakdown of losses over temperature is included to facilitate a better understanding of the opportunities and challenges introduced by this article.