A non-isolated bidirectional soft switching current fed LCL resonant dc/dc converter to interface energy storage in DC microgrid

Abstract

This paper proposes a non-isolated soft-switching bidirectional dc/dc converter for interfacing energy storage in DC microgrid. The proposed converter employs a half-bridge boost converter at input port followed by a LCL resonant circuit to assist in soft-switching of switches and diodes, and finally a voltage doubler circuit at output port to enhance the voltage gain by 2x. The LCL resonant circuit may also add a suitable voltage gain to the converter. Therefore, overall high voltage gain of the converter is obtained without transformer or large number of multiplier circuit. For buck operation, the high side voltage is first divided by half with capacitive divider to gain higher step down ratio. Converter is operated at high frequency to obtain low output voltage ripple and reduced magnetics and filters. Zero voltage turn-on is achieved for all switches and zero current turnon and turn-off is achieved for all diodes for both buck/boost operation. Voltage stress across switches and diode is clamped naturally without external snubber circuit. An experimental prototype rated at 350 W has been designed, built and tested in the laboratory to verify the analysis, design and demonstrate the performance of proposed converter.