AN ABSTRACT OF A THESIS ANALYSIS AND CONTROL OF AN AC/DC PWM RECTIFIER- ASSISTED INDUCTION GENERATOR Jyoti Sastry Master of Science in Electrical Engineering The development of the model of series and parallel rectifiers and the operation of these rectifiers at unity power factor was achieved. The method of control to achieve unity power factor operation was presented using the dq model of the rectifier topologies. This condition of operation is achieved by an in-depth steady state analysis of the converter topologies. A novel method of steady-state analysis of an induction machine as a dc power generator is developed, where the steady-state model was obtained using the dq reference frame equivalent circuits of the induction generator system. Also, the self-excitation requirements of an induction generator were studied, in terms of the magnitude of the modulation index of the rectifier. The detailed analysis studied the system under two operating conditions, rated slip and minimum loss. The condition for minimum loss was achieved by operation of the generator at the slip calculated to satisfy this condition. The effect of magnetic saturation was also accounted for in the analysis. A new control structure for the rotor-flux vector control of an induction machine as a dc generator was developed, where the input-output linearization method was used in separating the linear from the nonlinear terms in the system model equations. The proposed control scheme aims at regulating the dc voltage at the output of the rectifier. The robustness of the proposed control scheme was tested and verified by simulation and experimental results. Control of an induction generator using natural variables was a new method of control put forth. The control scheme was simpler as the system model was in the stationary reference frame. The system model used included a loss-minimization loop, whereby the reference rotor flux in the control scheme was calculated such that the induction generator system operates under a condition of minimum loss. ANALYSIS AND CONTROL OF AN AC/DC PWM RECTIFIER- ASSISTED INDUCTION GENERATOR A Thesis Presented to The Faculty of the Graduate School Tennessee Technological University by Jyoti Sastry In Partial Fulfillment Of the Requirements of the Degree MASTER OF SCIENCE Electrical Engineering August 2005 i CERTIFICATE OF APPROVAL OF THESIS ANALYSIS AND CONTROL OF AN AC/DC PWM RECTIFIER- ASSISTED INDUCTION GENERATOR by Jyoti Sastry Graduate Advisory Committee: Joseph O. Ojo, Chairperson date Prit Chowdhuri date Ghadir Radman date Approved for the Faculty: Francis Otuonye Associate Vice President for Research and Graduate Studies Date ii STATEMENT OF PERMISSION TO USE In presenting this thesis in partial fulfillment of the requirements for a Master of Science degree at Tennessee Technological University, I agree that the University Library shall make it available to borrowers under rules of the Library. Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgement of the source is made. Permission for extensive quotation from or reproduction of this thesis may be granted by my major professor when the proposed use of the material is for scholarly purposes. Any copying or use of the material in this thesis for financial gain shall not be allowed without my written permission. Signature Date iii DEDICATION This work is dedicated to my family. iv ACKNOWLEDGEMENTS I would sincerely like to express my gratitude to the chairperson of my committee, Dr. Joseph Ojo, for his support throughout the period of my Masters Program. I would like to thank Dr. Ghadir Radman and Dr. Prit Chowdhuri for serving as faculty members on my committee. I would also like to thank Zhiqiao Wu, Gan Dong, Conard Murray, and L.V. Randolph for their invaluable help during the course of this project. I would also like to thank the Department of Electrical and Computer Engineering, Center for Energy Systems Research, and the Office of Naval Research (ONR) for the financial support provided during my study. I would like to thank my parents, brother, sister, and Varghese Muthalaly for their moral support, invaluable help, and encouragement during the course of my Masters Program. v TABLE OF CONTENTS Page LIST OF FIGURES....................................................................................................... XI LIST OF TABLES .....................................................................................................XXV CHAPTER 1. INTRODUCTION ...................................................................................................1 1.1 INTRODUCTION .......................................................................................................1 1.1.1 Classification of Switching Power Converters .................................................2 1.2 INDUCTION GENERATORS........................................................................................4 1.3 RESEARCH GOALS ..................................................................................................5 1.4 ORGANIZATION OF THESIS ......................................................................................6 2. LITERATURE REVIEW ............................................................................................9 2.1 INTRODUCTION .......................................................................................................9 2.2 SERIES- PARALLEL BOOST RECTIFIERS..................................................................10 2.3 INDUCTION GENERATORS......................................................................................13 3. MODELING OF THREE-PHASE BOOST RECTIFIER...........................................19 3.1 INTRODUCTION .....................................................................................................19 3.2 OPERATION OF THREE-PHASE BOOST RECTIFIER ...................................................20 3.3 POSSIBLE SWITCHING MODES OF THE BOOST RECTIFIER........................................25 vi Page 3.4 MODULATION TECHNIQUES...................................................................................29 3.5 RELATIONSHIP BETWEEN SWITCHING FUNCTION AND MODULATION SIGNAL .........30 3.6 MODEL OF THREE-PHASE BOOST RECTIFIER..........................................................32 3.7 DYNAMIC SIMULATION OF THREE-PHASE BOOST RECTIFIER ..................................40 3.8 STEADY – STATE ANALYSIS..................................................................................43 4. SERIES AND PARALLEL BOOST RECTIFIERS ...................................................49 4.1 INTRODUCTION .....................................................................................................49 4.2 PARALLEL RECTIFIERS..........................................................................................51 4.2.1 Model of Parallel Rectifiers...........................................................................51 4.2.2 Steady State Analysis ....................................................................................58 4.2.3 Dynamic Simulation......................................................................................64 4.3 SERIES RECTIFIER .................................................................................................71 4.3.1 Model of Series Rectifier...............................................................................72 4.3.2 Steady State Analysis ....................................................................................75 4.3.3 Dynamic Simulation......................................................................................79 4.4 PARALLEL RECTIFIERS WITH COMMON INPUT SOURCE...........................................82 4.4.1 Model of Parallel Rectifiers...........................................................................84 4.4.1 Steady State Analysis ....................................................................................88 4.4.1 Dynamic Simulation......................................................................................90 5. MODELING OF AND PARAMETER DETERMINATION OF THREE-PHASE INDUCTION MACHINE..............................................................................................99 vii Page 5.1 INTRODUCTION .....................................................................................................99 5.2 BASIC OPERATION OF AN INDUCTION MACHINE...................................................100 5.2.1 Stator-Flux Model of Induction Machine.....................................................107 5.2.1 Rotor-Flux Model of Induction Machine .....................................................109 5.2.1 Natural Variables Model of Induction Machine ...........................................112 6. STEADY-STATE ANALYSIS OF VSI-ASSISTED INDUCTION GENERATOR.123 6.1 INTRODUCTION ...................................................................................................123 6.2 SYSTEM MODEL..................................................................................................124 6.2.1 Steady-State Model of Battery.....................................................................126 6.2.2 Overall System Model.................................................................................127 7. MODELING OF THREE-PHASE INDUCTION GENERATOR- RECTIFIER SYSTEM.....................................................................................................................145 7.1 INTRODUCTION ...................................................................................................145