Mainstream designed, built and tested a 2.5 kW 3-port isolated dc-dc converter that is modular and scalable for space applications. This unit consolidates a spacecraft’s electrical power system into a single unit by simultaneously interfacing solar panels (250–400 Vdc), a battery bank (40–60 Vdc), and spacecraft loads (28 Vdc). The converter achieves 98.1% efficient (peak) with GaN power semiconductors and utilizes soft switching techniques.