A new cascaded multi-level phase structure suitable for high-voltage high-power applications

A new phase-structure of cascaded multilevel is proposed for high-voltage high-power application. The proposed phase structure consists of identical half-bridge (HB) submodules (SM), which are divided into upper and lower arms like in a modular multilevel converter (MMC). The SMs in the lower arm are connected in opposite polarity to those in the upper arm. By such an arrangement, the proposed phase structure is capable of outputting AC voltage. As a result, the popular CHB-based converters can be replaced by converters based on the proposed phase structure, featuring the same output characteristic, but halved number of switches. It not only can be used in grid-connected single-phase or three-phase inverters, but also supply load as inverter. An application in STATCOM as an example is studied. The experimental results also prove the viability of the proposed phase structure.