Analysis of Multicarrier Switching Techniques for Nine Level Inverter

The demand for multilevel inverter have increased over time due to the high total harmonic distortion and unsatisfactory operation of conventional inverter. Cascaded H-bridge (CHB) multilevel inverter is simple, requiring fewer power components and more reliable than other types of topology so it is more preferable. But to increase the level of inverter output more number of components are required which makes more switching losses. So we are going toward asymmetrical topology which helps to get more number of levels with less number of power components. In this paper nine-level asymmetric CHB inverter is presented with eight power switches and two dc voltage sources of 1:3 proportion. The analysis is done for carrier scheme, amplitude index, and modulation index. Results are obtained with MATLAB Simulink software.

I. Introduction

Today’s Era the power inverters are an integral part of power conversion technology in modern power generation, distribution, transmission and utilization of electric power. As the power semiconductors are a vital part of the inverter has high voltage stress across them as well as the current draws by this converter have high distortion. In order to alleviate this problem, multilevel inverter (MLI) is proposed. The first topology of MLI has been proposed and patented in 1975 by Baker and Banister. The whole scenario of MLI is to reduce the voltage stress across the power switches however at the same time it has high voltage required by the load [1]-[3]. The main advantage of a multilevel inverter is to get more number of levels with fewer harmonics contain in the output waveform. Due to low harmonics contained in output waveform which make system become more stable and reliable. Multilevel inverter topologies are described as Cascaded H-bridge, Diode clamped and Flying capacitor. Among them, CHB is widely used due to its scalability, feasibility, reliability, and modularity. Cascaded H-bridge inverters do not require clamping diodes and flying capacitors so the component count in Cascaded H-bridge (CHB) is minimum which results in reduced switching losses [4]-[6].