Bidirectional Converter for Single-Cell Li-Ion Batteries in a Moon Rover

This work deals with a circuit intended to operate as a BCDR in small space vehicles, and especially in the cases when battery sizing is driven by the need to complement the power provided by primary power sources during high peaks of load, while a comparatively small energy is required during eclipses. In particular, a Bidirectional Three Level Neutral Point Clamped (TLNPC) converter was selected, designed and built in a prototype capable to operate as a BCDR to interface a 12V bus with a single-cell Li-ion battery. After providing a rationale of the single-battery-cell approach, and of the criteria adopted to select the TLNPC converter circuit, the paper reports principles of operation of the converter and indicates design criteria for the main circuit parameters. Extensive characterization of the laboratory prototype completes the work.