Three-phase five-level bidirectional buck- + boosttype PFC converter for DC distribution systems

This paper discusses a three-phase high-power factor five-level buck- + boost-type converter well-suited for acting as interface between residential DC power distribution systems and the AC grid. The power converter is constructed with two phase-shift modulated six-switch buck-type PFC converters, efficiently paralleled across their DC-link by inter-phase transformers, and a voltage and/or current inverting switching section. Accordingly, the system features: bidirectional current carrying capability; relatively low semiconductor part count; high utilization of the power semiconductors; and low current and voltage ripples at the input and output terminals. The characteristics of this topology, including the principles of operation, modulation strategy, and dimensioning equations are described in this paper. The feasibility of the presented converter is demonstrated by means of a constructed hardware prototype.