Performance analysis of reduced switch ladder type multilevel inverter using various modulation control strategies

Abstract

Multi-Level Inverters (MLI) are finding applications in UPS, drives, Grid interfaces because of dynamic output voltage control capability. In this paper a nine level single phase MLI topology with optimized switches is proposed. Increased output level helps in smoothening the output waveform along with reduced THD and eliminates need of filtering circuits. Proposed Reduced Switch Ladder Type MLI (RSL-MLI) topology consists of four DC power sources and nine switches for single phase inverter. When compared to conventional MLIs for same nine output levels, this topology has less number of devices making it cost effective. Both, high frequency switching pulse width modulation and fundamental frequency switching modulation methods are used for simulation of proposed nine level RSL-MLI topology. Output voltage waveform, THD are analysed using Simulink and equated to validate the performance of planned topology. Further, simulation is carried for five and seven levels of output voltages and THD are analysed.