ELECTROMAGNETIC SYSTEM DESIGN FOR WIRELESS POWER By JOAQUIN JESUS CASANOVA A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2010 °c 2010 Joaquin Jesus Casanova 2 To my family, for their support and encouragement 3 ACKNOWLEDGMENTS First and foremost, I’d like to thank Dr. Jenshan Lin for being the most helpful, understanding, and encouraging advisor a student could ask for. He is one of the rare professors who will give his students to explore their research on their own, and in doing so, allows them to truly learn. Thanks are also due to my commitee, Dr. Henry Zmuda, Dr. Robert Moore, and Dr. Subrata Roy, for their encouragement and insightful questions. They put me at ease without going easy on me. I owe a debt of gratitude to Zhen Ning Low for taking the first steps on this project, for his help understanding power amplifiers, and for his friendship and conversation. He kept me sane. I thank Jason Taylor, Ashley Trowell, and Raul Chinga for their technical support, guidance, and friendship in working on this project. Thanks also go out to my parents and my brother, who always supported me, even if it did seem like my life was nothing but my research to the exclusion of all else. Finally, I’d like to thank Florida High Tech Corridor and Florida Department of Environmental Protection for funding and support. 4 TABLE OF CONTENTS page ACKNOWLEDGMENTS .................................. 4 LIST OF TABLES ...................................... 8 LIST OF FIGURES ..................................... 9 ABSTRACT ......................................... 14 CHAPTER 1 INTRODUCTION TO WIRELESS POWER TRANSFER . 16 2 LOOSELY-COUPLED NEAR FIELD WIRELESS POWER . 18 2.1 Introduction ................................... 18 2.2 Analysis ..................................... 18 2.2.1 Design Equation for Crx ........................ 20 2.2.2 Design Equation for Lout ........................ 21 2.2.3 Design Equation for Cout ........................ 21 2.2.4 Design Equation for Ct ......................... 22 2.3 Tests ....................................... 23 2.4 Conclusion ................................... 28 3 NEAR-FIELD ELECTROMAGNETIC ANALYSIS . 30 3.1 Introduction ................................... 30 3.2 Coil Fields .................................... 30 3.3 Coil Inductance ................................. 31 3.4 Coil Parasitics .................................. 33 3.4.1 Round Conductor ............................ 33 3.4.1.1 Skin effect .......................... 33 3.4.1.2 Proximity effect ........................ 35 3.4.2 Rectangular Conductor ......................... 36 3.4.2.1 Skin effect .......................... 37 3.4.2.2 Proximity effect ........................ 40 3.5 Litz Wire ..................................... 42 3.6 Regulations ................................... 42 3.7 Conclusion ................................... 43 4 OPTIMAL PRIMARY COIL DESIGN ........................ 45 4.1 Introduction ................................... 45 4.2 Planar Wireless Power System ........................ 45 4.3 Coil Design ................................... 46 4.4 Testing ...................................... 47 5 4.5 Results ..................................... 48 4.6 Conclusion ................................... 49 5 M:N ANALYSIS .................................... 52 5.1 Introduction ................................... 52 5.2 Analysis ..................................... 52 5.3 Tests Results .................................. 55 5.3.1 Verification ............................... 57 5.3.2 Receiver Decoupling .......................... 58 5.3.3 Impact on Efficiency and Total Received Power . 63 5.4 Conclusion ................................... 65 6 OPTIMAL PRIMARY COIL DESIGN FOR MULTIPLE COILS . 67 6.1 Introduction ................................... 67 6.2 Coil Design ................................... 67 6.3 System ..................................... 68 6.4 Testing ...................................... 71 6.5 Results ..................................... 71 6.6 Conclusion ................................... 73 7 INCLUSION OF FERRITES ............................. 74 7.1 Introduction ................................... 74 7.2 Inductance Estimation ............................. 75 7.3 Loss Estimation ................................. 78 7.4 Thickness and Width Effects ......................... 78 7.5 Experimental Evaluation ............................ 80 7.6 Conclusion ................................... 83 8 BAYESIAN LOAD/FAULT TRACKING ....................... 84 8.1 Introduction ................................... 84 8.2 Technology/Data ................................ 86 8.3 Theory/Methods ................................ 86 8.3.1 State/Measurement Model ....................... 86 8.3.2 Particle Filter Algorithm ........................ 87 8.3.2.1 Dataset generation ..................... 87 8.3.2.2 Initialization .......................... 88 8.3.2.3 State ............................. 88 8.3.2.4 Measurement ........................ 88 8.3.2.5 Update ............................ 89 8.3.2.6 Estimate ........................... 89 8.3.3 Tests ................................... 90 8.3.4 Implementation ............................. 90 8.4 Simulation Results ............................... 91 6 8.5 Measured Results ............................... 95 8.6 Conclusion ................................... 96 9 MIDRANGE WIRELESS POWER TRANSFER . 103 9.1 Introduction ...................................103 9.2 Analysis .....................................104 9.2.1 Coil Design ...............................105 9.2.2 Component Selection . 106 9.2.2.1 Series-parallel . 107 9.2.2.2 Series-series . 108 9.2.2.3 T-network . 108 9.3 Preliminary Tests ................................109 9.3.1 Rectifying Diode Effects . 109 9.3.2 Frequency and Inductance Effects . 111 9.3.3 Topology Effects ............................113 9.3.4 Sensitivity ................................113 9.4 Synthesis ....................................118 9.4.1 50 cm Separation ............................118 9.4.2 1 m Separation .............................119 9.5 Conclusion ...................................123 10 FAR-FIELD WIRELESS POWER TRANSFER . 125 10.1 Introduction ...................................125 10.2 Theory ......................................127 10.3 Solution Details .................................128 10.4 Physical Properties ...............................129 10.4.1 Soil ....................................129 10.4.2 Atmosphere ...............................130 10.4.2.1 Gaseous water vapor . 130 10.4.2.2 Water droplets . 131 10.4.2.3 Ice crystals . 133 10.4.3 Vegetation ................................134 10.5 Results and Discussion ............................135 10.5.1 Atmospheric Loss Estimation for Solar Power Satellite . 136 10.5.2 Loss Estimation for Radiofrequency-Harvesting Sensor Under Vegetation Canopy . 138 10.5.3 Flux ...................................139 10.6 Conclusions ...................................139 11 CONCLUSIONS ...................................142 REFERENCES .......................................143 BIOGRAPHICAL SKETCH ................................150 7 LIST OF TABLES Table page 2-1 Design parameters. ................................. 23 2-2 Component values. .................................. 23 4-1 Summary of system performance. ......................... 49 5-1 Component values for 1 and 2 transmitter systems. 57 5-2 Maximum Prx and maximum ´c for different M:N arrangements. 63 6-1 Design parameters. ................................. 68 6-2 Component values. .................................. 70 6-3 Summary of system performance. ......................... 71 7-1 Ferrite properties. .................................. 81 7-2 Ferrite experimental evaluation with solenoid coil. 82 9-1 Component values. ..................................110 9-2 Component values. ..................................111 9-3 Component values. ..................................112 9-4 Component values. ..................................118 9-5 Summary of 1 m tests. ................................120 10-1 Parameter values for RTE. ..............................136 8 LIST OF FIGURES Figure page 2-1 One-to-one wireless power system block diagram. 18 2-2 Class E driving circuit for a wireless power system. 19 2-3 Test setup. ...................................... 24 4 2-4 From top left, clockwise: Rin, \Ztx , drain voltage waveform at RL = 10 ­, and Q. ........................................ 25 2-5 Received power and total efficiency as a function of RL. 26 2-6 Received power and total efficiency as a function of RL, and their 95% confidence intervals. ....................................... 27 2-7 Efficiency as a function of RL. ........................... 28 3-1 Current stick for MQS analysis. .......................... 31 3-2 Magnetic field components using MQS and MoM techniques of a 1m by 1m square coil. ..................................... 32 3-3 Magnetic field magnitude using MQS and MoM techniques of a 1m by 1m square coil. ..................................... 32 3-4 Conductor cross section showing field and current in round conductor under skin effect. ...................................... 34 3-5 Conductor cross section showing field and current in round conductor under proximity effect. ................................... 35 3-6 Conductor cross section showing field and current in rectangular conductor