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A converter intended to be used for the interconnection of battery-based energy storage systems with the cells of a multilevel converter is addressed in this paper. High efficiency at light and medium loads is important in these applications and it can be achieved using soft switching techniques. Two control techniques with fixed and variable switching frequency are proposed and compared. The use of silicon carbide (SiC) mosfets provides a higher attainable switching frequency, which is especially interesting in variable frequency control techniques, allowing the operation at high voltages and high switching frequencies, with high efficiencies over a wide power range. A synchronous boost DC/DC converter rated for 400 to 800 V and 10 kW is designed and developed with SiC mosfets obtaining efficiencies higher than 97% from 100% to 3.5% of full load using a variable switching frequency (up to 200 kHz) control. Significant efficiency improvement is achieved at medium and light loads. [ABSTRACT FROM PUBLISHER]

This paper is focused on a high-voltage (400 to 800 V) bidirectional converter, which is intended to be used for the interconnection of battery-based energy-storage systems with the cells of a modular multilevel converter, providing distributed energy-storage capability to a solid-state transformer. This converter must have a high efficiency at medium and light load and also a low current ripple due to the charging and discharging processes. This work takes advantage of the use of SiC MOSFETs into a synchronous boost converter to accomplish the previous requirements. First, the adoption of a variable-switching frequency control to keep the efficiency high is analyzed, and second, the use of a modular converter with different control techniques to provide a current ripple reduction is also addressed in this study. An input-parallel–output-parallel synchronous boost converter, made up with three modules (3 kW per module), is used to validate experimentally the advantages of the use of SiC MOSFETs and to compare different control techniques. [ABSTRACT FROM PUBLISHER]