ABSTRACT

In this Project, a multilevel inverter (MLI) scheme is proposed for 4-pole 9-phase induction motor (IM) drives with improved DC bus utilization as well as reduced device count. The proposed MLI is realized with nine 3-switch inverter legs (3-SIL) and a single DC source. In the proposed MLI, each 3-SIL is utilized for exciting the two identical voltage profile coils (IVPC)/phase of the 4-pole stator winding, which means each leg has to be modulated with two references. This 2 independent references/leg will limit the modulation index (M.I) of 3-SIL based proposed MLI. This lower M.I will result in a requirement of the higher magnitude of DC-link voltage to achieve the rated load voltage requirement. In this Project, an effective phase reconfiguring concept is proposed for reducing the DC-link voltage requirement of the proposed MLI. In addition, all the possibilities of phase reconfiguring details for proposed MLI fed 9-phase IM drive are also presented. A 3-phase carrier-based space vector pulse width modulation is implemented for improving the linear modulation range of proposed MLI configuration further. In contrast with existing 9-phase 3-level inverters like NPC and FC, the proposed MLI configuration requires only one DC-link (with half of the magnitude) and lesser number of semiconductor devices. The proposed MLI fed 5 hp 9- phase 4-pole IM drive is validated by using Ansys Maxwell FEM simulation and Experimental prototype for entire modulation range.