Flexible Multilevel Converters Using Four-Switch Extended Commutation Cells

The extended commutation cell is a four-port, four-switch cell that allows bidirectional energy transport in two orthogonal directions throughout the cell. By cascading multiple cells, a multilevel converter can be constructed with a high number of levels. The voltage across each cell capacitor can be adjusted independently of the load, resulting in high flexibility in output levels. In this paper, the general theoretical analysis for this cell, including the necessary design tools, is detailed. Experimental results of a two-cell eight-level dc-ac converter are given. The outcomes are in good agreement with the analysis and simulation results.