This paper presents a novel Double Uneven Power (DUP) converter based dc-dc converter and its design and control methods. The main objectives are to reduce the power losses in the power semiconductor devices and to reduce the output filter inductance in a high-power (MW-levels) dc-dc converter. The proposed converter utilizes two full-bridge converters in a special way to realize the Zero-Current Switching (ZCS) and to reduce the output filter inductance. The advantages of the proposed converter become more significant for high-power applications. A comparative simulation for a dc-grid wind farm application has been performed to verify the effectiveness of the proposed converter in high-power applications. It has been shown that the proposed converter not only requires less filter inductance, but also has less power losses in the semiconductor devices. A smallscale prototype has been built to verify the operational principle of the proposed converter.

This paper presents a novel bidirectional double uneven power (BiDUP) based dc-dc converter and its design and control methods. The proposed converter utilizes two dual active bridge (DAB) converters with different power ratings in a special way to realize zero current switching (ZCS), where both turn-on and turn-off switchings occur under the zero-current condition. A design example of the proposed BiDUP converter is presented for medium voltage (MV) and high-power solid-state transformer (SST) systems where both voltage transformation and bidirectional power flow are required. The main features of the proposed converter are to reduce both the switching losses in power semiconductor devices and the filter inductance requirement simultaneously. To verify the feasibility of the proposed converter, a simulation study on the BiDUP converter based SST in a distribution system is presented. Furthermore, to validate the operational principle of the proposed converter, an experimental study using a small-scale prototype is also presented.