A Novel Mechanism for Harmonic Reduction in Single Source Isolated Buck-Boost Hybrid Multilevel Inverter

Abstract

Traditional Hybrid Multilevel inverter produces (2n+1) levels at output voltage of inverter for n number of sources by a switching mechanism which requires 4n number of switches. However, one underlying problem of single phase multilevel inverter is that it requires isolated sources which render it inappropriate except where isolated energy sources are available. In this paper, firstly, a new technique is proposed for generating multiple isolated Buck-Boost DC sources of variable voltages from a single DC source. Secondly, a new switching algorithm is proposed by which number of output voltage levels can be increased by 80%, 157% and 833% while reducing number of switch count by 0%, 16.66% and 25% keeping voltage stress across the switches unhampered for two, three and four source inverter respectively compared to traditional multilevel inverter. As a result, conspicuous improvement is achieved in terms of harmonic distortion dropping it down to 4% and less than 1% for three and four source inverter respectively even without using output filters or sinusoidal PWM switching signals. A meticulous analysis of the circuit configuration and switching algorithm along with detailed performance analysis is provided throughout the paper.