ABSTRACT
In pole-phase modulation, the phase order is coming down by pole ratio times in high pole mode, which results in the higher magnitude of spatial harmonics as well as higher torque ripple. In this Project, the available three identical voltage fed windings per effective phase in 3-phase 12-pole (3PH-12PO) mode are used to develop the simple multilevel inverter (MLI) configuration for minimizing torque ripple. The proposed MLI scheme is realized with three 5-leg inverter modules. Each 5 leg inverter module will generate 3 level voltage across the phase, thereby resultant voltage seen by each phase winding is 5 level voltage in 3PH-12PO mode. This multilevel voltage will improve the torque ripple profile of the motor drive. In addition, the proposed MLI scheme along with phase grouping will enrich the linear modulation range of the Pole Phase Modulated Induction Motor (PPMIM) drive in 9-phase 4-pole (9PH-4PO) mode. The switches used to generate a multilevel voltage in 3PH12PO mode are effectively utilized for blocking the flow of circulating currents. As compared to other conventional 9- phase 5-level inverters the proposed 5-level inverter requires only 30 switches and it doesn’t require extra clamping diodes/capacitors and extra bidirectional switches for isolating neutrals in 9PH-4PO operation. The validation of proposed MLI scheme is done on a 5hp 9- phase IM with Ansys Maxwell as well as laboratory prototype for entire modulation range using V/f = constant control.