A Stacked Multilevel Inverter With Single DC Link for Open-End Winding Induction Motor Drive With Zero-Voltage Switching and Common-Mode Voltage Elimination

A switching state selection scheme for a five level stacked multilevel inverter for open end winding motor drive is presented in this work. Using the proposed scheme, converter can be operated with a single DC supply and with zero common mode voltage. In addition, the switching transition of high voltage switches occurs at zero voltage conditions. The degree of freedom provided by the redundant switching states and voltage vectors of the inverter topology is utilised to design the modulation scheme. The proposed switching state selection leads to inherent capacitor balancing without using any extra sensors and fundamental frequency switching of the high voltage switches of the topology. The modulation scheme uses triangular carrier comparison and hence avoids the complexity of sub-sector identification and dwell time calculation. Half wave symmetry in output waveforms is ensured by maintaining synchronous sampling with constant samples per fundamental cycle. The inverter topology and the effectiveness of state selection scheme is experimentally validated on an open end winding induction motor drive and experimental results showing steady state and dynamic operation are presented.