A novel switching strategy for improving modularity and manufacturability of cascaded-transformer-based multilevel inverters

An efficient switching scheme to equalize the size of transformer is proposed for a multilevel inverter employing cascaded transformers, which have a series-connected secondary. All transformers can be designed with the same size regardless of their position because the maximum magnetic flux imposed on each transformer becomes exactly equal each to each. Therefore, identical full-bridge inverter units can be utilized, thus improving modularity and manufacturability. The fundamental idea of the proposed switching pattern is illustrated and then analyzed theoretically. The validity of the proposed switching strategy is verified by experimental results.