A Single DC Source-Based Three-Level Inverter Topology for a Four-Pole Open-End Winding Nine-Phase PPMIM Drives

This article proposes a three-level inverter topology for nine-phase pole phase-modulated induction motor (PPMIM) drives by using the two identical voltage profile coils (IVPC) of a four-pole stator winding. In general, the two IVPCs of each phase winding are connected in series, but in this article, these two IVPCs are separated and excited with conventional two-switch inverter legs without disturbing the flux per pole and other machine parameters. The 18 IVPCs of four-pole nine-phase induction motor (IM) are excited with 18 two-switch inverter legs and fed by the same dc source. Each two-switch inverter leg generates the two-level voltage across each IVPC winding, i.e., the resultant voltage seen by the phase winding is a three-level voltage waveform. As compared to conventional nine-phase neutral point and flying capacitor multilevel inverters (MLIs), the requirement of the dc-link magnitude for the proposed topology is reduced by 50%. The nine-phase PPMIM drive is modulated with the carrier-based three-phase space vector pulsewidth modulation in order to enhance the linear modulation range (LMR). The inverter legs associated with two IVPCs per phase in 9-phase 4-pole (9PH-4PO) mode and six IVPCs per phase in 3-phase 12-pole (3PH-12PO) mode are modulated with the same reference wave and phase-displaced triangular waves. This results in the generation of multilevel voltage with improved harmonic voltage profile, i.e., minimizes the torque pulsations of nine-phase PPMIM drive. The validation of the proposed MLI-fed 5 hp nine-phase PPMIM drive is carried out by using the Ansys Maxwell FEM tool as well as with an experimental prototype.