This paper describes the 750-Vdc, 100-kW, 20-kHz bidirectional isolated dual-active-bridge(DAB) dc-dc converters using four 1.2-kV 400-A SiC-MOSFET dual modules with or without Schottky barrier diodes(SBDs). When no SBD is integrated into each dual module, the conversion efficiency from the dc-input to the dc-output terminals is accurately measured to be 98.0% at the rated-power(100 kW) operation, and the maximum conversion efficiency is as high as 98.8% at 41-kW operation, excluding the gate-drive and control-circuit losses from the total power loss. The bidirectional isolated DAB dc-dc converters are so flexible that series and/or parallel connections of their individual input and output terminals make it easy to expand the voltage and current ratings for various applications such as the so-called “solid-state transformer” or “power electronic transformer.”