Multilevel DC Link converter with auxiliary module for level multiplication

Reduced switch count multilevel converters are garnering interest due to their reduced component count, lower losses, and high-quality power output. The idea of a levelmultiplier (LM) network for multilevel inverters is appealing, as it increases the number of voltage levels without proportional increase in component count. This paper introduces a general idea for a level-multiplier network for Wave-Shaper (WS)/multilevel DC-link inverters. A STATCOM application is chosen to verify the claims. The DC side of the converter consists of cascaded Half-Bridge modules and one auxiliary Full-Bridge module. The Full-Bridge module acts as the level multiplier. Algorithm to maintain the capacitor voltages of the level multiplier and other modules are presented. A voltage tolerance band based voltage control is used for the level multiplier module. Simulation results of two converters of the Wave-Shaper (WS)/multilevel DC link inverter family are considered to show the effectiveness of the proposed level-multiplier and capacitor voltage balancing algorithm.