SIMULATION AND IMPLEMENTATION OF TWOLEVEL AND THREE-LEVEL INVERTERS BY MATLAB AND RT-LAB THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By ABD ALMULA G M GEBREEL Graduate Program in Electrical and Computer Science The Ohio State University 2011 Master's Examination Committee: Professor Longya Xu, Adviser Professor Jin Wang © Copyright by ABD ALMULA G M GEBREEL 2011 Abstract A power electronics device which converts DC power to AC power at required output voltage and frequency level is known as an inverter Two categories into which inverters can be broadly classified are two level inverters and multilevel inverters Some advantages that multilevel inverters have compared to two level inverters are minimum harmonic distortion, reduced EMI/RFI generation, and operation on several voltage levels A multilevel inverter can be utilized for multipurpose applications, such as an active power filter, a static VAR compensator and a machine drive for sinusoidal and trapezoidal current applications Some drawbacks to the multilevel inverters are the need for isolated power supplies for each one of the stages, the fact that they are a lot harder to build, they are more expensive, and they are more difficult to control in software This focus of this thesis is the simulation study of single phase, three phase, two-level, and three-level inverters Full analysis for two-level and three-level inverter are included Software packages MATLAB/SIMULINK and RT-LAB were used to study and simulate inverter waveforms in off time and in real time, respectively Firstly, single phase and three phase inverters are modeled with resistive load and inductive load and their waveforms are observed Secondly, a two-level inverter (single phase and three phase two-level inverter) is modeled by different ways and suitable switching control strategies (PWM technique) to carry out harmonic elimination Thirdly, a three-level inverter (single phase and three phase three-level inverter) is modeled by different ways and ii suitable switching control strategies (PWM technique) to carry out harmonic elimination Finally, all inverters models are modeled and run in real time by using RT-LAB and the results in both cases (off time and real time) are the same Two level and multilevel inverters in both cases for single-phase and three-phase are modeled, run and compared It is formed that in both real time and off time the results were acceptable Also, some derivations, such as thirteen segments of region for each sector, nine segments of region in each sector, seven segments of region for each sector for three-level inverter, which have never been mentioned before, are derived and the switching sequence for each region in each sector is drawn iii Dedication I wish to dedicate this thesis to my family: My son Yazed My daughter Arowa My daughter Tasneem My mother, my wife, my older sister, my father, my friend Dan Aikens and his family thank you for your unending love, support, and above all for being my inspiration which made the completion of this thesis possible iv Acknowledgments I wish to thank all those who helped me complete my M.S in Electrical Engineering at the Ohio State University I would like to thank Professor Longya Xu for giving me an opportunity to work on this thesis by supervising my research, serving as my major professor, providing valuable advice from time to time and for his guidance, encouragement, and support during my graduate study I would like to thank Professor Jin Wang for serving on my thesis committee, and teaching ECE 624 and ECE793 which helped me towards my research I would like to thank Professor Donald G Kasten for his valuable ECE 740, ECE741 and ECE643 classes I would also like to thank my lab mates, Wang for his heartfelt support, and making my graduate school experience so much more enjoyable A special thanks to all my Libyan friends at The Ohio State University and my friend in Libya Finally, I want to extend my deepest thanks and appreciation to my dear wife and my family for their never-ending support and kindness v Vita March 05, 1976……………………………………… ….Born – EL-BIEDA – LIBYA August 1998…………………………… ……………….B.S Electrical Engineering, Omar Al-Mukhtar University, EL-BIEDA - LIBYA September 1999- July2000…………………………… ……………….Electric Engineer at Libyan Electric General Company August 2000– September 2004…………………….……….Electric Engineer at GPTC (General Post and Telecommunications Company \ Libya) October 2004 – December 2007…………………….….…Head of Project between ZTE/China and GPTC/Libya (Fiber optics, Microwaves, and Exchanges stations) January 2008 – April 2008 Teaching Assistant Major Field: Electrical and Computer Engineering / The Ohio State University/ Columbus / Ohio vi Table of Contents Abstract ii Dedication iv Acknowledgments v Vita vi List of Tables xi List of Figures vii Chapter 1: Introduction 1.1 Introduction 1.2 Single-Phase Half-Bridge Inverter 1.2.1 Single-phase half bridge inverter with resistive load 1.2.2 Single-phase half bridge inverter with inductive- resistive load 1.3 Single Phase Full-Bridge Inverter 1.3.1 Single-phase full-bridge inverter with resistive load 1.3.2 Single-phase full-bridge inverter with resistive load 11 1.4 Three-Phase Inverter 13 vii 1.4.1 three-phase 180o degree mode VSI 14 1.4.2 three-phase 120o degree modeVSI 17 1.5 Three Phase Inverter Application 20 1.5.1 Three Phase Inverter Application 25 1.6 Experimental Results 28 1.6.1 Single-Phase Full-Bridge Inverter with R-L load 28 1.6.2 Three-Phase Iverter feed three phase R-L load with Lagging 90o 31 1.7 Conclusion 35 Chapter 2: Two-Level Inverter, Analysis And Simulations 36 2.1 Introduction 36 2.2 Space Vector Modulation 37 2.2.1 Switching Status 37 2.2.2 Space Vector Concept 38 2.2.3 Principle of Space Vector PWM 41 2.2.4 Realization of Space Vector PWM 41 2.2.5 Switching Time Duration at any Time 45 2.2.6 Determine the switching time for each switch (s1 to s6) 46 2.2.7 Switching sequance 46 2.3 Simulation and Experimental Results 53 viii 2.3.1 Single-Phase Two-Level inverter 53 2.3.2 Three-Phase Two-Level Inverter By Using Universal Bridge 56 2.3.3 Three-Phase Two-Level Inverter By Using SVPWM algorithm 59 2.3.4 Exerimental results of two-level inverter by RT-LAB 63 2.3 Conclusion 66 Chapter 3: Analysis of Three-Level Inverter 67 3.1 Inrtoduction 67 3.2 Three-level inverter operation (analysis of SVPWM) 69 3.2.1 Switching Status 69 3.2.2 Space Vector Modulation 69 3.2.2.1 Stationary Space Vector 69 3.2.2.2 Determing the Sector 72 3.2.3 Time Calculation 73 r 3.2.4 relationship between Vref location and time 77 3.2.5 The Switching Status By Using the Switching Sequance 78 3.1 Conclusion 93 Chapter 4: Simulation and Hardware in the loop Results of Three-Level Inverter 94 4.1 Introduction 94 4.2 Matlab Results 94 ix V=3; % elseif (ta < time) && (time