International Journal of Control and Automation Vol.10, No.9 (2017), pp.15-26 http://dx.doi.org/10.14257/ijca.2017.10.9.02 ISSN: 2005-4297 Copyright ⓒ 2017 SERSC Australia Investigations on Z-Source Based Three Level Inverter 1 Chinnapettai Ramalingam Balamurugan and Kumaravel Vijayalakshmi Karpagam College of Engineering, Coimbatore, Tamil Nadu, India crbalain2010@gmail.com Abstract This paper presents the new inverter topology based on combination of Z Source Inverters (ZSI) and Multi Level Inverters (MLI). The basic structure includes one DC voltage source, Z-network and multilevel inverter. MLI composed of four switches to generating three voltage levels. The proposed work eliminates the limitations of both voltage source inverter and current source inverter by replacing multilevel inverter. The presence of multilevel inverters provide high output voltages with low harmonics without the use of transformers .The Z source concept can be applied to ac-dc, dc-ac, ac-ac and ac-dc power conversions. Z-source inverter can able to boost up the inverter Direct Current (DC) side voltage. This work observes the rms (Root Mean Square) output voltage and presence of THD (Total Harmonic Distortion) in the output waveform by simulating the Z source multilevel inverter using MATLAB/simulink. The Z-source multilevel inverter is simulated by sinusoidal reference, TAR reference, THI reference and trapezoidal reference with various inductance (L) and capacitance(C) values. The RMS voltage is controlled by varying the modulation index. Keywords: IndexTerms - Z Source Inverter, Multilevel Inverter, THD, RMS, Reference Signals 1. Introduction The Z-source inverter topology was developed in 2002 to overcome the problems of traditional inverters. Z source inverter is used to reduce the line current harmonic, high reliability and improves the input power factor. The traditional Z source inverter consists of an impedance network having two inductors and two capacitors. The main circuit is coupled with the DC source using impedance network in Z source inverter. Z-source inverter used in both bucks and boost operations. Shoot through state of the ZSI determines the buck- boost feature to the inverter. The proposed work presents the features of Z-source multilevel inverter to eliminate the limitation of voltage source inverter and current source inverter by replacing multilevel inverter. Multilevel inverters are composed of a number of power electronics switching devices and DC voltage sources. Multilevel inverters increase the voltage levels in the output, provide higher quality of power in its output and reduce the harmonic contents. The Z-source multilevel inverter has the ability to buck-boost the voltage. Keith Corzine and Yakov Familiant in [1] discussed about a new cascaded multilevel inverter H bridge drive. This concept, as well as supplying each cell with a unique dc voltage, can result in a high number of dc voltage levels. Peng in [2] determined about functions of Z- Source inverter. It employs an impedance network to couple the main circuit with DC source. Z-source network composed of two inductors and two capacitors. The Z- source concept can be applied to ac-dc, dc-ac, ac-ac and dc-dc power conversions. The Z- source inverter can overcome the limitations of voltage source and current source inverters. Peng et al. in [3] discussed about Z source inverter system and control for Adjustable Speed Drives (ASD). The Z- Received (November 11, 2016), Review Result (July 10, 2017), Accepted (August 18, 2017)