Equalizing the Use of Voltage Sources in Multi-level Structures

Abstract

In multi-level converters which employ several DC voltage sources to deliver an AC output waveform by voltage levels, the selection method and use time of each source has direct effect on the longevity of sources and consequently total system. It is obvious that equal entrance and exit of voltage sources and also time use of them, increase longevity of sources and total system. On the other hand, same condition of working in voltage sources, yield to same condition for switches and uniformed heat distribution produced due to power losses. In this paper the subject of equalizing the use of voltage sources in multi-level structures, especially in symmetrical CHB, would be discussed. For this purpose, switching tables of CHB is corrected and Simulation results on a seven level of this structure with both prevalent and proposed methods are presented. These results confirm performance of corrected switching table and shows improvement in proposed converter work and uniformity in power loss distribution created by switches.