A new hybrid multilevel inverter based on coupled- inductor and cascaded H-bridge

Abstract

This paper proposes a new hybrid coupled-inductor and cascaded H-bridge (CHB) multilevel inverter. In the proposed topology, one 5-level coupled inductor inverter is cascaded with several H-bridges so that a hybrid multilevel inverter is obtained. The main aim is to use the advantages of both topologies (coupled-inductor and CHB) in one structure. In the 5-level coupled-inductor inverter, the current of switches is reduced to half of the output current making it possible to use low-current switches in this part. In the CHB part, the voltage of the inverter is divided on several bridges so that low-voltage switches can be used. Also, the proposed topology gives higher number of voltage levels with lower number of switches. For example, the proposed 9-level inverter uses only 10 switches while the CHB multilevel inverter uses 16 switches for the same number of voltage levels. A suitable control method is also presented for the proposed topology. Using this control method, only the low-current switches operate with high frequency and the other switches operate with fundamental frequency. This results in reduced stresses on the switches. The simulation results of the proposed 9-level inverter are presented to verify the proposed topology and control method.