A New Five Level Stacked Multilevel Inverter with Reduced Common Mode Voltage

A new reduced switch count 5L stacked multilevel inverter (SMI) fed open end winding (OEW) motor drive is proposed. The SMI topology is obtained by cascading a single low-voltage switched network with a three-phase H-bridge network and results in reduction of semiconductor devices and gate drivers. As a result, the topology achieves a compact size and generate 5L output without requiring additional capacitors, diodes or multiple power supplies. Two space vector modulation methods, along with switching state selection, are proposed for the inverter topology to synthesize the reference voltage. The switching state selection ensures self-balancing of DC-link capacitors, eliminates zero sequence current, and gives reduced common mode voltage (RCMV) operation with half-wave symmetry in the output waveform. The performance of the proposed 5-level inverter is experimentally verified using an open-loop voltage/frequency control system on a three-phase OEW induction motor drive. Test results are presented under various steady state and dynamic operating conditions to validate the modulation scheme and the RCMV operation.