A novel eighteen-level inverter for an open-end winding induction motor

A novel hybrid eighteen-level inverter topology for open-end winding induction motor (IM) is presented in this paper. In the proposed topology one end of the open-end IM is fed by 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 eighteen-level 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) topology. 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 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. Exhaustive simulation study is carried out to evaluate the performance of proposed inverter for the entire modulation range and results are presented.