Performance Evaluation of 18-Level Inverter Fed Open-end Winding IM Drive

Abstract

A novel hybrid 18-level inverter topology for open-end winding induction motor (OWIM) is presented in this paper. In the proposed topology one end of the open-end winding IM is fed by a conventional two-level inverter, while other end is connected to a nine-level cascade H-bridge (CHB) inverter. The combined effect of these two inverters generates 18 levels in the phase voltage of open-end winding IM. The two-level inverter with higher DC link voltage has lower switching frequency and thereby reduces the switching losses. In addition to that, the proposed topology requires less number of components as compared to conventional multilevel inverter (MLI) topologies. An interesting feature of the proposed topology is that, it can operate in nine-level mode by connecting the motor winding in star in case of failure of the two-level inverter. Similarly, if the fault occurs in CHB inverter the proposed inverter can operate in two-level mode. Thus, the reliability of the system is improved. The proposed topology is experimentally verified on 1.5 kW OWIM. The experimental results have proven an excellent steady-state as well as transient-state performance of the proposed inverter in the entire range of linear modulation.