INTERNATIONAL JOURNAL OF RESEARCH IN TECHNOLOGY (IJRT) ISSN No. 2394-9007 Vol. V, No. I, February 2018 www.ijrtonline.org Impact Factor: 4.012 Published under Asian Research & Training Publication ISO 9001:2015 Certified 49 Conventional & Reduced Switch Multilevel Inverter Topologies: A Survey Abstract— Multilevel converters have been evolving for a long time, however it is still under continuous development, and many new topologies have emerged in the recent researches. This paper presents a review of these recent contributions to ascertain the trends in this area so as to provide present standing of multilevel converter technology. Initially a brief overview of the established multilevel converters is presented and then the new promising topologies are discussed. While the classical topologies have proved to be an alternative, there has been an active interest in the evolution of newer topologies. Reduction in overall part count as compared to the conventional topologies has been an important objective in the recently introduced topologies. In this paper, some of the recently proposed multilevel inverter topologies with reduced power switches are reviewed. The comparison of the different topologies presented in this paper may help readers to seek an appropriate multilevel solution for a given application. Recent advances made in modulation and control of multilevel converters is also addressed. The paper emphasises on applications of multilevel converters in non conventional application areas. Finally, some future trends and challenges in the further development of this technology are discussed. Keywords: Multilevel Inverter (MLI), Cascaded Half bridge (CHB), Neutral point clamp (NPC), Flying Capacitor (FC). I. INTRODUCTION Multilevel inverters are finding increased attention as one of the preferred choices for electronic power conversion and today are considered a mature and proven technology. Presently they are widely used in blast furnace blowers, conveyors, crushers, compressors, pumps, fans, rolling mills, hoists, HVDC transmission, hydro pumped storage, wind energy conversion, solar photovoltaic systems, and railway traction systems to name a few [1]. With the advent of recent power sensors, digital controllers and electronics devices, the role of power inverters has become critical for futuristic smart grids having greater penetration and integration of renewable energy sources based power generation [9]. Manuscript received on February, 2018. Pushpendra Kumar Bhatt, M.Tech Scholar, Department of Electrical Engineering, Millennium Institute of Technology & Science, Bhopal, M.P., India. Prof. S. K. Soni, Asst. Professor, Department of Electrical Engineering, Millennium Institute of Technology & Science, Bhopal, M.P., India. A multilevel inverter is basically a power electronic interface that produces a desired output voltage by connecting various DC sources and switches in an appropriate manner. Multilevel inverters are nowadays becoming a key solution for DC power utilization (batteries, solar panels or fuel cells) [1-2], high dynamic performance and power-quality constrained applications covering a power range from 1 to 30 MW [3]. The basic concept of an MLI to achieve higher power is to use power semiconductor switches like IGBTs, MOSFETs, etc. along with appropriate DC voltage sources to perform the power conversion by synthesizing a staircase voltage waveform. This paper reviews recent as well as conventional topologies of multilevel inverters to seek a MLI with reduced number of switches for higher step count in the output. Though multilevel inverter is a proven technology yet it has lot of challenges and possibilities. Researchers are trying to further improve efficiency, reliability, power density, simplicity and cost of classical multilevel inverter topologies like the Neutral Point Clamped (NPC), Cascaded H-bridge (CHB) and the Flying Capacitor (FC), and their modulation methods. II. CLASSIC MULTILEVEL TOPOLOGY OVERVIEW The classic topologies are those that have been extensively addressed and have been in applications for more than a decade. Multilevel technology started with the multilevel stepped waveform concept with Series Connected Half Bridges (CHB) inverter. This was followed by development of a flying capacitor (FC) topology the same year [4]. Fig. 1: Classic MLI topologies: (a) Three-level NPC (b) Three-level Flying Capacitor (FC) and (c) Five-level CH Bridge And in late 70s, the diode clamped topology [5] was introduced. The Diode Clamped topology evolved as three- Pushpendra Kumar Bhatt, S. K. Soni