Search

Multilevel dc-dc converters making use of high-frequency transformers are suitable for integration in solid-state solutions for applications in electric power distribution systems. This paper presents a simplified switching scheme for three-level full-bridge dc-dc converters that enables zero-voltage and zero-current switching of all the main power devices. It describes the main operational modes and design equations of the converter as well as provides simulation and experimental results to demonstrate the feasibility of the proposed ideas. Index Terms--Distributed energy resources, multilevel converters, soft-switching converters, three-level (3L) full bridge (FB), zero-voltage zero-current switching (ZVZCS).

Distributed energy resources (DERs) are becoming integral components of electric power distribution systems. In most cases, an isolated dc-dc converter forms part of the interface required to connect the DER output to the distribution system. Operation of the converter at high switching frequencies results in size reduction of passive components at the expense of increased switching losses. However, silicon carbide (SiC) power devices have the potential of operating at high switching frequencies without significant loss penalty because of their fast switching times and ability to work at high temperatures when compared to similar Si devices. SiC diodes have already displayed the ability to offer more ideal diode behavior than Si diodes. Engineering samples of SiC MOSFETs are depicting lower switching losses and conduction losses over Si MOSFETs. This display is making SiC devices attractive for dc-dc converters used to connect DERs to the distribution system. This paper particularly deals with the design of a 300-W 100-kHz dc-dc full-bridge converter using zero-voltage zero-current switching for comparison of SiC MOSFETs and diodes against Si MOSFETs and diodes. Index Terms--DC-DC converters, distributed energy resources (DERs), full bridge, silicon carbide (SIC) MOSFET, zero-current zero-voltage switching.