Quazi Trans-Z-Source T-type Multi-level Dual Inverter with Improved Performance for Open-end Winding Induction Motor Drives

This paper presents an improved trans-Z-Source network and its control for dual inverter fed open end winding induction motor drive. A major drawback of VSI is that it requires high battery capacity and provides only buck operation. Dual inverter topologies have the advantage of low battery voltage requirement and more levels in output voltage. Introduction of impedance network in dual inverter configuration can further reduce the battery voltage requirement. Proposed circuit consists of a 3-level Z-Source inverter on one side and a 2 level voltage source inverter (VSI) on the other side with two isolated DC sources. Isolated power supplies are kept at voltage levels 1:(B/4) to generate a 6 level space vector structure, where B is the boost factor of the Z-Source network. Output voltage can be varied by regulating the turns ratio, time period for shoot-through and modulation index. Various operation modes, voltage relationships and modulation technique used are explained in detail. For modulation of trans-Z-Source network, simple boost control technique is used and carrier-based space vector PWM is used for inverter modulation. MATLAB simulation on a 3HP, 220V scalar controlled three-phase IM drive is done to validate the working of the proposed topology.