Multipulse Converter Fed New 7-Level Cascaded Multilevel Inverter Based Induction Motor Drive

This paper presents a new configuration of medium voltage drive (MVD), in which a 60-pulse AC-DC converter is adopted on grid side and a unique cascaded 7-level inverter on the drive end. This 60-pulse converter utilizes a new multi-phase transformer, which converts 3-φinput into 5-φ output AC-supply. The cascaded 7-level inverter is achieved by cascading six numbers of three-phase VSI in unique manner. This type of cascading is taken because the voltage and power level of the level can be scaled as per the application demand. Moreover, this configuration of 7-level inverter needs less numbers of power semiconductor switches than conventional 7-level cascaded H-bridge (CHB) inverter. A vector control scheme is used to control an induction motor (IM) and in this vector control rotor flux reference frame is taken to avoid coupling between the d and q axes currents. A nearest level modulation technique (NLMT) is adopted to control presented 7-level inverter. Due to this NLMT, a 7-level inverter is switched at fundamental frequency switching (FFS) and offers low switching losses than conventional CHB. Performance of MVIMD is verified through both simulated and test results while operating it at different operating conditions and it shows promising performance for the presented drive during all required operating region.