Bidirectional converter for single-cell Li-ion batteries in a small space vehicle

A Battery Charge-Discharge regulator (BCDR) intended to interface a 12V bus with a single-cell Li-ion battery for power levels in the 100W range is presented. It may be useful 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, with comparatively small energy amounts. In particular, the Bidirectional Three Level Neutral Point Clamped (TLNPC) converter configuration was selected, and a prototype was designed, built and tested. After providing a rationale of the single-battery-cell approach, and of the criteria adopted to select the TLNPC converter circuit, the paper reports the principles of operation of the converter and indicates the design criteria for the main circuit parameters. Extensive characterization of the prototype completes the work.