Reduced Power Components Based Asymmetric Multilevel Inverter With Elimination of Lower Order Harmonics

Conventional drive converters suffer from several power component counts, a complex circuit design, large switching losses, and other problems. Motivated by these issues, a reduced power components-based asymmetric hybrid inverter is presented for a medium voltage drive. A new structure is designed with a series connection of (1:1) dc-source-based level generator unit with polarity converter H-bridge, which is cascaded to a conventional H-bridge, whose dc source magnitude is double. An eleven-step inverter is configured with a ten-power switches and three dc sources. An extension of proposed inverter to higher voltage levels can be easily achieved by cascading several level-generator and H-bridge units. Due to utilization of selective harmonic elimination (SHE), most power switches are turned on and off at a low and fundamental frequency, which significantly reduces losses and enhances converter efficiency. A further benefit of SHE is that it provides precise control over harmonic spectrum of a specific voltage and/or current waveform produced by a power converter. Nonlinear equation of selected harmonic is solved optimally using particle swarm optimization (PSO) in this study. Apart from this, a 54-pulse rectifier is designed to maintain dc-link voltage and to feed input power to this eleven-level inverter. Apart from this, presented drive ends eleven level dc-ac and grid side fifty-four pulse ac-dc converter, are used to mitigate lower order harmonics at motor terminal currents/ voltages and grid currents. Drive design details, operational modes and fundamental switching scheme are described in detail. This topology is validated using tests on a down-scale prototype, and test results are presented in detail.