Description: A bidirectional dual active bridge (DAB) dc-dc converter for electrical power systems (EPS) is proposed. The converter operates as a charger, upconverter, and downconverter using a single transformer. The converter uses smart technology to interleave DAB converter stages for ripple current reduction and optimized load sharing of stages to extend the high efficiency load range of the converter to 6.25% of full load. By using smart technology, the load condition of each DAB converter stage is monitored and its load sharing controlled depending on the converters total load condition. In this way, each converter stage is kept at or above 25% load. Therefore the minimum load of the new DAB converter with four interleaved stages is one fourth of 25% or 6.25%. The design employs radiation-resistant and cryogenic-temperature-capable GaN HEMT devices to process 2 kW of power per stage. Mainstream has tested GaN HEMT devices to -225 C. GS66508T GaN HEMT devices are rated for 650 VDC maximum drain-to-source maximum voltage stress allowing for a maximum steady-operating voltage of 400 VDC at 60% derating.

Benefits: Many NASA applications can benefit from incorporating the DAB converter into their electrical power systems. Spacecraft power systems can manage power sources with fewer power supplies. To charge on-board batteries and provide the high-voltage DC bus for motor inverters, the power systems of NASA electric vehicles, such as the Modular Robotic Vehicle and unmanned aerial vehicles, such as the Predator B, need compact, low-volume, low-mass dc-dc converters. The converter must also be bidirectional and multifunctional.

Military vehicle, and helicopter starter-generator power systems also necessitate the use of small, compact, dc-dc converters. These applications also operate in extremely low temperature conditions of less than -55 C in artic, high elevation, and cold, high-altitude, environments. Therefore the DAB converter is an optimal solution for these applications.