A New Bidirectional Three-Phase Phase-Modular Boost-Buck AC/DC Converter

Abstract

In this paper, a new phase-modular bidirectional three-phase boost-buck AC/DC converter topology is introduced. Each of its three phase modules is operated independently and consists of a boost-buck converter, allowing to directly convert an AC voltage into an arbitrary DC voltage by only modulating one of the two converter stages at a time, where the AC voltages are applied against a reference point common to all phases. Hence, single-stage high-frequency energy conversion is enabled, resulting in a highly compact and highly efficient converter system realization. In a first step, the basic structure of the phase-modular converter (PMC) is derived from the well known cascaded arrangement of a three-phase boost-type rectifier and a subsequent DC/DC buck converter, followed by a discussion of its operating principle and characteristic waveforms. Furthermore, the corresponding DC output voltage control scheme is presented which allows a seamless transition between buck and boost operation in each phase module. Finally, the phase-modular converter and the conventional two-stage system are compared by means of simple indices as well as a two-dimensional Pareto optimization concerning efficiency $\eta$and power density $ \rho $.