Scholars' Mine Masters Theses Student Theses and Dissertations Spring 2011 Design of a conditioner for smoothing wind turbine output power Murali Bottu Follow this and additional works at: https://scholarsmine.mst.edu/masters_theses Part of the Electrical and Computer Engineering Commons Department: Recommended Citation Bottu, Murali, "Design of a conditioner for smoothing wind turbine output power" (2011). Masters Theses. 4900. https://scholarsmine.mst.edu/masters_theses/4900 This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. DESIGN OF A CONDITIONER FOR SMOOTHING WIND TURBINE OUTPUT POWER by MURALI BOTTU A THESIS Presented to the Faculty of the Graduate School of the MISSOURI UNIVERSITY OF SCIENCE AND TECHNOLOGY In Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE IN ELECTRICAL ENGINEERING 2011 Approved by Dr. Mariesa L. Crow, Advisor Dr. Badrul H. Chowdhury Dr. Mehdi Ferdowsi 2011 Murali Bottu All Rights Reserved iii ABSTRACT As a result of wind speed intermittency, wind turbine output power can be highly variable. The large variability in output power can adversely impact local loads that are sensitive to pulsating power. To mitigate large swings in power, the wind turbine output power can be smoothed by using a small energy buffer. A power conditioner is proposed to smooth the wind power output by utilizing the energy of an ultracapacitor. The conditioner is based on a single phase voltage source inverter (VSI) connected between the grid interconnection point and the ultracapacitor. The shunt VSI injects or absorbs active power from the line to smooth the wind power output by utilizing the short term storage capabilities of the ultracapacitor. The ultracapacitor is connected to the DC link through a DC-DC converter. The bidirectional DC-DC converter acts in buck mode during discharge and in boost mode during charging to maintain the voltage of the DC link relatively constant to provide good controllability of the VSI. The control strategies for the conditioner are presented in this thesis. The simulation results show that the power quality conditioner is efficient in smoothing the wind power. To understand how effectively the power conditioner smoothes the wind turbine output in real time operational conditions, a hardware prototype for verification is developed in addition to software simulation. The bidirectional DC-DC converter and VSI are constructed and tested in the laboratory and then field tested. The control of the bidirectional DC-DC converter is implemented using the microchip PIC24FJ128GA010 microcontroller. The gate signals for the IGBTs in the VSI are obtained from the TI TMDSDOCK28335 digital signal controller. The conditioner design and control are validated on a Skystream 3.7 wind turbine installed at Missouri University of Science & Technology. iv ACKNOWLEDGMENTS I would like to express my sincere gratitude to my advisor, Dr. Mariesa Crow, for her guidance, supervision and encouragement throughout my Master’s program and with my research. She has been a continuous source of motivation and has helped me to develop my skills. I dedicate this thesis to her. I would like to thank Dr. Mehdi Ferdowsi and Dr. Badrul Chowdhury for their time and effort in serving as committee members and helping through my graduate studies. I would like to thank Mr. Jerry L. Tichenor and Dr. Jonathan Kimball, who have been very helpful throughout my work. Lastly, I am obliged to my parents, my sister, and my friends who have been very supportive throughout my studies offering encouragement. Without their support, I would not have been achieved my Master’s study. v TABLE OF CONTENTS Page ABSTRACT ....................................................................................................................... iii ACKNOWLEDGMENTS ................................................................................................. iv TABLE OF CONTENTS .................................................................................................... v LIST OF ILLUSTRATIONS ............................................................................................ vii LIST OF TABLES ............................................................................................................. ix NOMENCLATURE ........................................................................................................... x SECTION 1. INTRODUCTION ...................................................................................................... 1 1.1 MOTIVATION .................................................................................................... 1 1.2 PROPOSED APPROACH ................................................................................... 1 1.3 CONTRIBUTIONS OF THE THESIS ................................................................ 2 1.4 OUTLINE OF THESIS........................................................................................ 3 2. WIND TURBINE AND ULTRACAPACITOR ........................................................ 5 2.1 INSTALLED WIND TURBINE ......................................................................... 5 2.2 SIMULINK MODEL OF THE WIND TURBINE .............................................. 7 2.3 SIMULATION RESULTS .................................................................................. 7 2.4 ULTRACAPACITOR ELECTRIC CIRCUIT MODEL ..................................... 8 3. POWER QUALITY CONDITIONER ..................................................................... 11 3.1 POWER CONDITIONER TOPOLOGY ........................................................... 11 3.2 EQUIVALENT CIRCUIT OF THE CONDITIONER ...................................... 12 3.3 CONSTRUCTION OF THE POWER QUALITY CONDITIONER ................ 14 4. BIDIRECTIONAL DC-DC CONVERTER ............................................................. 16 4.1 DC-DC CONVERTER TOPOLOGY ............................................................... 16 4.2 CONTROL OF THE DC-DC CONVERTER ................................................... 17 4.3 SIMULATION RESULTS ................................................................................ 20 4.4 CONSTRUCTION OF THE DC-DC CONVERTER ....................................... 20 4.4.1 PIC Microcontroller ................................................................................ 22 vi 4.4.2 Voltage Measuring Circuit ...................................................................... 24 4.4.3 Gate Driver Circuit .................................................................................. 26 4.5 HARDWARE RESULTS .................................................................................. 27 5. SHUNT INVERTER ................................................................................................ 30 5.1 TOPOLOGY OF THE VSI ................................................................................ 30 5.2 CONTROL OF THE SHUNT INVERTER ....................................................... 31 5.3 CONSTRUCTION OF THE SINGLE PHASE VSI ......................................... 33 5.3.1 Measurement Circuit ............................................................................... 33 5.3.2 Signal Shaping Circuit ............................................................................. 33 5.3.3 Digital Signal Controller ......................................................................... 34 5.3.4 PWM Signal Generation ......................................................................... 37 5.4 HARDWARE RESULTS .................................................................................. 37 6. SYSTEM VALIDATION ........................................................................................ 42 6.1 SIMULATION RESULTS ................................................................................ 42 6.2 HARDWARE RESULTS .................................................................................. 45 7. CONCLUSION AND FUTURE WORK ................................................................. 49 APPENDIX: LIST OF THE COMPONENTS ................................................................. 50 BIBLIOGRAPHY ............................................................................................................. 52 VITA ................................................................................................................................. 54 vii LIST OF ILLUSTRATIONS Figure Page 2.1. Wind Turbine Installed at the Missouri University of Science and Technology ......... 5 2.2. The Actual Output Power of Installed Wind Turbine (blue) and the Target Smoothed Power (red) ................................................................................................. 6 2.3. Skystream3.7 Wind Turbine Connections to the Grid ................................................. 7 2.4. Modeled Active Power Output of the Wind Turbine................................................... 8 2.5. Electric Model of the Ultracapacitor ............................................................................ 9 3.1. Topology of the Power Quality Conditioner ............................................................. 12 3.2. Equivalent Circuit of the Conditioner .......................................................................