Analysis of a New Symmetic Multilevel Inverter Topology with Reduced Component Count

Abstract

Medium voltage drives (MVDs) are increasingly used in industrial applications. Like any ac drive, MVDs employ inverter to modulate the power being supplied to the ac motor so as to match the speed-torque characteristic of the motor with that of the load. The only distinguishing feature is that MVDs operate at the voltage levels of 2.2, 3.3, 4.16, or 6.6 kV. Presently, the solid state technology is such that the power semiconductor switches that operate at medium voltage are not easily available. Multilevel inverter (MLI) emerges as the ideal choice for MVDs as it can overcome this issue with the series connection of switches that is inherent to its power structure. However, MLI topologies often suffer from high switch/diode count. This paper proposes a new symmetrical MLI topology with reduced component count. A comparison of the proposed MLI topology with the earlier reported topologies is presented in this work for the different levels of output voltages. Furthermore, the operation of the proposed 7-level MLI topology supplying a three phase induction motor is analyzed for steady state.