Voltage droop control of dual active bridge for integrating battery energy storage to utility gird

This paper proposes a voltage droop method to control the power flow of the bi-directional DC/DC converter associated with a dual active bridge (DAB). The proposed controller dynamically varies the phase shift angle between the two imposed voltages on the high frequency transformer to control the power flow in the DAB network. A DAB topology with full bridge on low voltage side and a single phase three level neutral point connected (NPC) structure on high voltage side is also developed to reduce the number of turns of the high frequency transformer. The proposed open loop controller is simple in implementation and limits the voltage across the neutral point connected capacitors with in an permissible dc-voltage range. Along with this zero voltage switching is achieved for the all the switches in full bridge and NPC for bi-directional power flow. Design procedure for resonant tank parameters selection for ZVS operation is also presented.