ARDUINO BASED HYBRID MPPT CONTROLLER FOR WIND AND SOLAR Michael Assaad Thesis Prepared for the Degree of MASTER OF SCIENCE UNIVERSITY OF NORTH TEXAS December 2017 APPROVED: Miguel Acevedo, Major Professor Weihuan Zhao, Committee Member Yan Wan, Committee Member Shengli Fu, Chair of the Department of Electrical Engineering Costas Tsatsoulis, Dean of the College of Engineering Victor Prybutok, Dean of the Toulouse Graduate School Assaad, Michael. Arduino Based Hybrid MPPT Controller for Wind and Solar. Master of Science (Electrical Engineering), December 2017, 62 pp., 12 tables, 33 figures, 39 numbered references. Renewable power systems are becoming more affordable and provide better options than fossil-fuel generation, for not only the environment, but a benefit of a reduced cost of operation. Methods to optimize charging batteries from renewable technologies is an important subject for off-grid and micro-grids, and is becoming more relevant for larger installations. Overcharging or undercharging the battery can result in failure and reduction of battery life. The Arduino hybrid MPPT controller takes the advantage of solar and wind energy sources by controlling two systems simultaneously. The ability to manage two systems with one controller is better for an overall production of energy, cost, and manageability, at a minor expense of efficiency. The hybrid MPPT uses two synchronous buck DC-DC converters to control both wind and solar. The hybrid MPPT performed at a maximum of 93.6% efficiency, while the individual controller operated at a maximum 97.1% efficiency when working on the bench test. When designing the controller to manage power production from a larger generator, the inductor size was too large due to the frequency provided by the Arduino. A larger inductor means less allowable current to flow before the inductor becomes over saturated, reducing the efficiency of the controller. Utilizing a different microcontroller like the PIC16C63A produces a much faster frequency, which will reduce the inductor size needed and allow more current before over saturation. Copyright 2017 by Michael Assaad ii ACKNOWLEDGEMENTS I would like to begin with thanking Dr. Acevedo for allowing me to go on this journey and guiding me when I came across many difficulties. His door was open anytime I had questions, and he always took the time to help me find solutions. He helped thoroughly understand the process and procedure needed to have a successful thesis. My appreciation extends to Dr. Wan and Dr. Zhao for their willingness to serve as members on my thesis committee. I would like to thank faculty, staff and students, both former and present in the Electrical Engineering Department of UNT, for everything you did, whether it was helping me with parts and equipment or just offering an ear to talk to. To staff such as Peggy Foster, Jason Mieritz and Nick Thompkins. As well as my colleagues Sanjaya Gurung and Samuel Iyiola. I would also like to thank Breana Smithers who took the time to help setup the project site and helped me understand important elements of my paper. Most importantly to my family, my mother Elizabeth Assaad, my father Bassam Assaad and my sister Sarah Assaad. They helped me through times when I was unsure of myself and were always there for support. My girlfriend Catalina Celemin, who has been by my side throughout the whole process. Lastly to my friends, Steven Davidson, Kareem Aridi, Logan Davidson, Mark Botros, Jason Bramow, Alex Szymanowski, Omar Hariri, Michael Kandalaft, Sebastian Ariza and Jake Lanning. Thank you for your support and encouragement. iii TABLE OF CONTENTS Page ACKNOWLEDGMENTS ............................................................................................................. iii LIST OF TABLES ......................................................................................................................... vi LIST OF FIGURES ...................................................................................................................... vii CHAPTER 1. INTRODUCTION ....................................................................................................1 1.1 Background ..............................................................................................................1 1.2 Motivation ................................................................................................................2 1.3 Objective ..................................................................................................................3 1.4 Chapters Overview...................................................................................................3 CHAPTER 2 LITERATURE REVIEW ..........................................................................................4 2.1 Introduction ..............................................................................................................4 2.2 Asynchronous Wind Turbine ...................................................................................4 2.3 Photovoltaic Panel ...................................................................................................5 2.4 Rechargeable Lead Acid Battery .............................................................................6 2.5 DC to DC Power Converter Circuits .......................................................................7 2.6 MPPT Controllers ..................................................................................................10 CHAPTER 3. SYSTEM HARDWARE ........................................................................................17 3.1 System Components...............................................................................................17 3.2 System Layout .......................................................................................................17 3.3 Component Selection .............................................................................................18 CHAPTER 4 SYSTEM AND SOFTWARE DESIGN ..................................................................25 4.1 Introduction ............................................................................................................25 4.2 Inductor and Capacitor Size Calculations for Hybrid Controller ..........................25 4.3 Controller Design ...................................................................................................27 4.4 Software Implementation........................................................................................30 CHAPTER 5 TESTING AND ANALYSIS ..................................................................................47 5.1 Introduction ............................................................................................................47 5.2 Solar MPPT Controller Test ..................................................................................49 iv 5.3 Wind Controller Test .............................................................................................51 5.4 Hybrid Controller Test ...........................................................................................53 5.5 Final Design of Hybrid Controller .........................................................................54 5.6 Prototype Component Cost ....................................................................................56 5.7 Current Consumption Analysis ..............................................................................56 CHAPTER 6. CONCLUSION AND FUTURE WORK ...............................................................57 REFERENCES ..............................................................................................................................58 v LIST OF TABLES Page Table 4.1: Compare output (OC0A) mode, fast PWM [37] ..........................................................35 Table 4.2: Compare output (OC0B) mode, fast PWM. [37] ..........................................................36 Table 4.3: Waveform generation mode bit description. [37] .........................................................36 Table 4.4: Clock select bit description. [37] ..................................................................................37 Table 4.5: Compare output mode, phase correct PWM Mode [37] ...............................................38 Table 4.7: Waveform generation mode [37] ..................................................................................39 Table 4.8: Clock select bit description [37] ...................................................................................40 Table 5.1: Efficiency of solar MPPT only .....................................................................................51 Table 5.2: Efficiency of wind MPPT only .....................................................................................52 Table 5.3: Efficiency of hybrid controller .....................................................................................54 Table 5.4: Component cost for prototype ......................................................................................56 Table 5.5: Current consumption analysis on prototype .................................................................56 vi LIST OF FIGURES Page Figure 1.1: Discovery Park project site............................................................................................2 Figure 2.1: Wind turbine power curve [2] .......................................................................................5 Figure 2.3: Characteristics of a typical 50 A-h lead-acid battery [4] ...............................................7 Figure 2.4: Buck converter design [8] .............................................................................................8 Figure 2.5: Synchronous buck converter [34]..................................................................................9 Figure 2.6: Boost converter design [9] ..........................................................................................10 Figure 2.7: Non-inverting buck-boost converter design [10] ........................................................10 Figure 3.1: Block diagram Arduino hybrid controller ...................................................................18 Figure 3.2: Arduino UNO [19] ......................................................................................................20 Figure 3.3: ASC712 current sensor [23] ........................................................................................21 Figure 4.1: Hybrid MPPT controller circuit diagram ....................................................................28 Figure 4.2: Flow diagram of control sequence ..............................................................................30 Figure 4.3: Defining power conditions for hybrid MPPT controller .............................................32 Figure 4.4: PWM, duty cycle, and voltage multiplier definitions .................................................33 Figure 4.5: LCD library and global variables ................................................................................33 Figure 4.6: Hybrid controller setup ................................................................................................34 Figure 4.7: TC0 control register A [37] .........................................................................................35 Figure 4.8: TC0 control register B. [37] ........................................................................................37 Figure 4.9: TC2 control register A [37] .........................................................................................37 Figure 4.10: TC2 control register B [37] .......................................................................................40 Figure 4.11: Solar and wind enabling and disabling ......................................................................41 Figure 4.12: Setting duty cycle under maximum ...........................................................................42 Figure 4.13: Setting duty cycle above minimum ...........................................................................42 vii Figure 4.14: Measuring and displaying measured values ..............................................................44 Figure 4.15: Solar DC-DC converter update .................................................................................46 Figure 4.16: Wind DC-DC converter update .................................................................................46 Figure 5.1: Changed limits for controller ......................................................................................48 Figure 5.2: Testing Setup ...............................................................................................................49 Figure 5.3: LCD display ................................................................................................................49 Figure 5.4: Solar MPPT only waveforms ......................................................................................50 Figure 5.5: Wind MPPT only waveforms ......................................................................................52 Figure 5.6: Hybrid MPPT controller waveforms ...........................................................................53 Figure 5.7: Final design concept ....................................................................................................55 viii CHAPTER 1 INTRODUCTION 1.1 Background Renewable energy technology has seen a large demand because of an increasing awareness of harmful pollutants and greenhouse gases that are associated with the production and burning of fossil fuels for electricity generation. The increased demand had a complementary effect to the cost of renewables, making them more accessible. Solar Photovoltaic (PV) systems are projected to reduce in cost by 65% from the year 2015 to 2025 [1]. Electric power production by renewable technology is growing, while overall efficiency is increasing for established systems such as wind turbines and solar panels. Other more established forms of renewable power, such as geothermal, and hydroelectric, are becoming more prevalent in the overall reduction of dependency on fossil fuels. Controllers such as Pulse Width Modulation (PWM) and Max Power Point Tracking (MPPT) help manage the energy produced from small-scale renewable systems, such as used off- grid and microgrids, to usable power. These controller types help monitor and regulate the amount of power being delivered to battery storage. The PWM is the less efficient of the two; PWM works by stepping down the voltage to match the voltage of the battery, allowing the current to flow until charged. The MPPT works by tracking the voltage and current; when the voltage is stepped down, the current is increased by using a voltage converter of Direct-Current (DC). This unit is typically called a DC-DC converter. Its role in this case is to match the power production of the source to the load [4]. 1