Modular zero-voltage switching converter for direct current microgrid applications

This study presents a high-voltage zero-voltage switching converter with balance capacitors in the direct current microgrid. In the proposed converter, full-bridge circuits with primary-series and secondary-parallel connection are used for high-voltage input and high-current output applications. The series connection of full-bridge circuits reduces the voltage rating of power switches in each full-bridge circuit cell. Therefore, high-speed power metal-oxide-semiconductor field-effect transistors are employed to reduce the converter size. Flying capacitors are connected between each full-bridge circuits so that the input split voltages can be balanced automatically in every switching period without using the complexity control scheme. The phase-shift pulse-width modulation scheme is used to regulate the output voltage. The power switches can be turned on at zero voltage due to the energy stored in the output inductors or primary leakage inductors and the switching losses are reduced. The output sides of the full-bridge circuits are connected in parallel to reduce the current ratings of transformer secondary windings and passive power components. Finally, experiments are provided to validate the characteristics and usefulness of the proposed converter in microgrid applications.