NPC based dual active bridge topology for integrating battery energy storage to utility gird

This paper proposes a new topology for dual active bridge (DAB) for integrating battery energy storage to the utility grid. The transformer plays an essential role in achieving the isolation between the two full bride converters in traditional DAB. In order to integrate the battery energy storage to the existing grid system, the transformer turns ratio should be very high for the traditional DAB. In this paper a bi-directional DC/DC converter with full bridge on low voltage side and a single phase three level neutral point connected (NPC) structure on high voltage side of the dual active bridge is developed. This topology will reduce the turns ratio of the isolation transformer as well as voltage stress on the switches. Along with this zero voltage switching is achieved for all the switches in full bridge and NPC for bi-directional power flow. The NPC based grid side inverter is employed in this paper with current hysteresis control. The overall configuration is suitable for utility application with improved reliability and reduced maintenance.