Natural balancing of series-stacked power quality conditioners

This paper develops a systematic and mathematically formal study of the balancing theory of series-stacked multilevel converters. It is shown that the dc bus voltages of these converters balance naturally, provided that the switching frequency is chosen high enough. Two balancing mechanisms, one associated with losses and the other with the load impedance, are identified. A single phase of a 2 MVA series-stacked power quality device was constructed and the theoretical results were verified experimentally. Index Terms--Balancing theory, multilevel converter, series-injection device, series-stacked converter.