Power conversion for a novel AC/DC aircraft electrical distribution system

This study proposes a novel and compact AC/DC electrical distribution system for new generation aircraft. In these new aircraft power systems, all loads are fed by two DC bus systems: at 28 V and at ±270 V. The electrical distribution system, whose design and implementation are described in this study, has only one primary AC source (360-900 Hz at 230 V) with all the required DC voltage levels being derived from this source. This solution enables elimination of the complex mechanical coupling apparatus currently used, for fixed frequency AC systems, to maintain the generator speed at constant level while the engines operate at variable speed. Under the proposed solution, all the conversion stages needed to generate various output voltage levels are implemented by using power converters assembled in one unit. Each converter has a current control loop in order to regulate the output current even during output line short circuits and also to limit the inrush current to the circuit at turn-on. To prove the concept, a 5 kW prototype was designed and tested, and demonstrated to meet all the specifications within the relevant standards regarding input and output power quality.