Bidirectional DC–DC Converter for Modular Residential Battery Energy Storage Systems

A novel bidirectional dc-dc converter based on the quasi-Z-source (qZS) topology is presented in this paper. During battery discharge, it operates as the conventional qZS full-bridge converter with a synchronous voltage doubler rectifier. During battery charging, it operates as the half-bridge converter with a synchronous full-bridge rectifier and LC filter. A relay is used for reconfiguration between those two modes. The operation principle is explained, and design guidelines are provided. A prototype with a nominal power of 300 W is used for verification of steady-state regulation characteristics and efficiency measurements in the input voltage range compatible with an eight-cell LiFePO4 battery. Closed-loop control system for the converter application in dc microgrids is presented and tested in two control scenarios: dc-bus signaling and direct reference defined by a master controller through a communication channel.