Harmonic Suppression Scheme for Multipulse Converter Fed Multilevel Inverter-Based IM Drive

Abstract

The medium-voltage induction motor drives are regularly utilized for crucial application in enormous industries. It is difficult to design a highly efficient drive system with a satisfactory power quality standard not only at the drive end but also at the grid end. To breakthrough this issue, a 36-pulse ac–dc converter fed seven-level binary cascaded H-bridge multilevel inverter (CHB-MLI) based drive system is presented in this work, where a 36-pulse converter is employed to enhance the power quality at the grid end. For this, the phase-shifted technique is implemented on a multiwinding transformer to eliminate the harmonics injected by the nonlinear diode bridge rectifier toward the grid side. Apart from this, the genetic algorithm selective harmonic elimination (GA-SHE) is applied to a seven-level binary CHB-MLI to diminish lower order (fifth and seventh) harmonics at the drive end. Moreover, a GA is adopted to determine the optimized switching angles by the solution of the nonlinear trigonometric equation of SHE. Furthermore, the GA-SHE-based fundamental frequency modulation scheme is favorable to decrease the switching losses and to enhance the drive end converter efficiency. The performance during the dynamics and steady state of the presented drive system with the indirect field-oriented control is analyzed through simulations and experiments on 298.4 kW and 7.5 kW squirrel-cage induction motors, respectively.