In Chaps. 2 and 3 , a single phase voltage-fed semi-dual active bridge (1p-VF-SDAB) DC-DC converter and control strategy have been discussed, but the single phase topology is not preferred to be used for high power application due to the high current stress in switches. So to reduce the current stress for high power applications, a novel high-frequency isolated three phase voltage-fed semi dual active bridge (3p-VF-SDAB) DC-DC converter is proposed for unidirectional power flow with wide input variations and high voltage interface in this chapter. A varying operating mode control independently implemented by phase shift and duty cycle control is subsequently raised to handle the stability and improve conversion efficiency of the converter under the light load conditions. A variety of different operating modes are illustrated and compared in detail. The power expressions and the root mean square (RMS) expressions of the leakage inductor current (LIC) of different modes are derived and the optimal modes are consequently selected. The gating signal falling edge compensation of secondary side switches is implemented to further improve the conversion efficiency. The zero voltage switching (ZVS) conditions based on current polarity is also derived. A 1.6 kW prototype was built to verify the effectiveness of the proposed topology and control strategy. The experimental results show that the proposed converter using the proposed control strategy can achieve the stability throughout the whole input and load variations. Moreover, seamless transition also can be achieved with a good dynamic performance and a high conversion efficiency that can be guaranteed.