A High-Efficiency Interleaved Single-Phase AC-DC Converter with Common-Mode Voltage Regulation for 380 V DC Microgrids

A transformerless two-stage bidirectional single-phase ac-dc converter is designed to connect 380 V bipolar dc microgrids with 240 V split-phase single-phase ac systems. The converter consists of a full-bridge ac-dc stage and a full-bridge dc dc stage. This decouples the common-mode (CM) voltage between the connected ac and dc systems. To achieve high efficiency, interleaving and state-of-the-art Silicon Carbide (SiC) MOSFETs are adopted. A pluggable phase-leg module with embedded driving and protection circuit is designed and tested. Interleaving angles are optimized for magnetics design. Besides high efficiency, an active CM voltage control method is incorporated to regulate the dc and low-frequency dc bus to ground voltage. A CM equivalent circuit is derived and used to design the CM controller. A 10 kW converter prototype is built and achieves an efficiency higher than 97%. The dc bus voltages are symmetric to ground, and the leakage current is suppressed.