PhD student Andrew Freeman with Advisor A. Stillwell

The term more-electric aircraft refers to the reduction or replacement of mechanical, hydraulic, electrical, and pneumatic subsystems with their electrically powered counterparts. This consolidation substantially lowers system weight and complexity, while improving efficiency, versatility, and serviceability. An increased electrical power demand necessitates a higher transmission bus voltage to prevent ohmic losses. However, existing power converter switches are limited in their maximum voltage capabilities; as a workaround, multilevel converters enable the use of lower-voltage switches with improved performance. Therefore, this project demonstrates a proof-of-concept flying-capacitor multilevel dual-active bridge (FCML-DAB), demonstrating how low-voltage GaN devices can be successfully integrated into a high-voltage power-conversion application. An 800:28 V prototype achieves a peak efficiency of 93.75% at 88 W in preliminary testing. The design incorporates a high-frequency planar transformer and leverages both the inherent frequency multiplication and the natural DC-blocking of the FCML half-bridge architecture.