Anomalous step-up behavior in discontinuous series resonant converters

This paper presents the analysis of a bidirectional series resonant converter (SRC) for light loads working in a discontinuous mode. By using the discontinuous mode, the converter´s efficiency is increased because zero current switching is possible at both the turn-on and turn-off process. However, an anomalous step-up behavior was found when the converter is attached to light loads. A comprehensive analysis of this phenomenon is presented and a practical solution for keeping the voltage conversion ratio fixed was implemented in a 25 kW prototype. The converter prototype is used in a supercapacitor power chain to transfer energy to a 560VDC link in a smart grid.