Scaling and balancing of multi-cell converters

Abstract

In this paper, the potential of the multi-cell approach for power electronic converters with efficiencies and power densities beyond the barriers of state-of-the-art systems is discussed. Based on fundamental scaling laws the benefits of splitting a system into multiple converter cells are derived in terms of lower volume and/or higher power density for a given cooling capacity. In addition, the conditions for equal current and/or voltage balancing of multi-cell systems is reviewed. The advantages of the mulit-cell systems are examined in more detail based on the example of a DC-DC boost converter realized with either parallel- or series-interleaved boost cells. It is shown, that the multi-cell systems can offer lower switching and conduction losses and/or an improved voltage spectrum depending on the choice of the switching frequency relative to a single system. Furthermore, the effects of parasitic capacitances on unwanted ground currents are investigated for both configurations.