Loss reduction in generalised multilevel converters

Abstract

Capacitor-switching operations found in magnetic-less DC-DC converters lead to significant capacitor power loss while capacitor voltage unbalance leads to high peak currents in the capacitors and switches. Power loss leads to premature failure of capacitors and is inversely proportional to both capacitance and switching frequency. A given reduction in losses then requires a corresponding increase in one of these parameters. This paper will show that by increasing the size of specific capacitors, it is possible to reduce significantly switching state transition capacitor losses and voltage unbalance without the need to increase the size of the capacitor bank by the same proportion. A method to identify capacitors that will lead to significant switching transition loss reduction when their sizes are increased is proposed.