Overview of Single-Stage Isolated AC-DC Topologies for Interfacing DC and AC Grids

The large-scale deployments of dc appliances and renewable generation have increased industry and research interest in dc electrical distribution systems for homes, offices, and other small buildings. In these systems, it is necessary to provide an isolated active front-end (AFE) interface between an ac grid and a residential dc microgrid/nanogrid. These power devices are often referred to as isolated active front-end (i-AFE) or grid interface converters. Single-stage isolated ac-dc converters can be a promising solution for the concept of the i-AFE converters. Single-stage topologies have no intermediate dc bus and potentially lead to reduced system weight, volume, and cost, compared to traditional two-stage solutions (ac-dc/dc-dc). Despite the potential advantages, single-stage isolated ac-dc converters are still an emerging topic in power electronics, which has not yet gained wide industrial adoption. This paper provides an overview of single-stage isolated ac-dc topologies, for dc microgrids application.