100kW bidirectional DC/DC converter for a supercapacitor stack

This paper presents the design of a 100kW DC/DC converter that transfer energy from/to two 125V-supercapacitor stacks to/from a 560V DC line that is attached to a three-phase inverter. The converter provides galvanic isolation between the 560V DC line and the supercapacitors. In one power flow direction, it works as a step-up DC/DC converter that maintains the DC voltage at 560V by delivering energy from the supercapacitors, and in the other direction it works as a current source to charge the supercapacitors. The proposed design is a two-stage converter: a series resonant converter that raises the supercapacitor voltage by four and provides isolation, and a half-bridge converter that maintains the output voltage by adjusting the step-up process. Experimental results are presented. The efficiency of the whole converter is higher than 91% at input currents up to 500A.