A Five-level AC/DC Converter for MV Solid-State Transformer

A five-level AC/DC converter is presented to realize single-module solid-state transformer (SST) design so that higher simplicity, reliability and power density may be achieved for medium voltage (MV) SSTs. The proposed five-level AC/DC converter consists of a three-level Neutral-Point-Clamped (NPC) converter and two three-level Flying-Capacitor (FC) converters. The operation of the AC/DC converter is explained. The control scheme including the balancing of flying capacitor voltage and neutral-point voltage is given. Finally the proposed circuit and control scheme are verified by simulation.