Bidirectional Dual Active Bridge Power Converter for Spacecraft Power Systems

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 ⁰C. 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.