A three level voltage space vector generation for open end winding IM using single voltage source driven dual two-level inverter

In this paper, a new scheme for three-level voltage space vector generation is proposed. In this work, the three-level inverter topology is realized by feeding an open winding induction motor with two two-level inverters, fed from a single dc source having the magnitude half compared to the NPC three-level inverter. Compared to existing three-level inverter topologies for open-end winding induction motor drives, the present work eliminates the requirement of two isolated voltage sources or additional power circuits (like common mode voltage chokes). In a conventional 3-phase four-pole induction motor, there exist two identical winding coil groups per phase around the armature, which are connected in series and spatially apart by two pole pitches. In this work, these two identical voltage profile pole pair winding coils in each phase of the induction motor are disconnected and reconnected in two star connected groups to deny the path for common mode current. They are fed from independently controlled (decoupled control) two two-level inverters from both sides of the motor with the same dc-link voltage with half the magnitude compared to conventional NPC three-level inverter. The scheme presented in this paper, doesn´t require any special design modification for the induction machine. For the present study, a four pole IM drive is used, and the scheme can be easily extended to induction motors with more than four poles. The proposed scheme is experimentally verified on a four pole, 5HP induction motor drive.