Single-Stage Non-Isolated Multiport Y-Converter for Interlinking 400 V DC Microgrids With the Three-Phase AC Grid

Abstract

The integration of dc microgrids (MGs) into distribution networks offers a promising solution to address the growing demand for electric energy by facilitating the incorporation of renewable energy sources and energy storage systems. To ensure sustained and reliable operation, dc MGs are commonly linked to utility grids through interlinking converters. However, with the increasing adoption of small-scale dc MGs for residential and commercial applications, the traditional approach of using a dedicated converter for each MG can significantly increase system size and cost. This paper proposes a single-stage non-isolated multiport converter (MPC) to interface the three-phase ac grid with 400 V dc MGs. The MPC enables direct power sharing between dc MGs, minimizes the dependence on the ac grid, and enhances the efficiency and power density of the power electronic interface compared to using multiple two-port converters. The motivations for the proposed converter include its single-stage power conversion among different ports, potentially leading to enhanced efficiency and power density. Furthermore, the absence of bulky intermediate dc-link capacitors and transformers in the proposed topology contributes to improved power density and reduced costs. Although designed for 400 V dc MGs in this study, the proposed MPC boasts buck-boost capability and bidirectional power flow at all ports, independent of the dc ports' voltage, providing the flexibility to directly interface with a wide range of dc systems. The performance of the converter is assessed through experimental tests under various operating conditions.

Keywords

• AC-DC power conversion
• Multiport converters
• Single-stage converters
• Three-phase modular converters
• Three-phase bidirectional rectifiers