1. Maximum Power Point Tracking System for Solar Racing Team Andrew Matteson Ingrid Rodriguez Travis Seagert Giancarlo Valentin April 25 th, 2011 GT Solar Jackets School of Electrical and Computer Engineering Georgia Institute of Technology

2. Project Overview Customized smart switching power system to charge car batteries with solar energy For use by the Solar Jackets in the World Solar Challenge 2011 Material cost: $121 per unit

3. Design Goals ProposedActual 2 MPPTs in 7” x 9” PCB2 MPPTs in 6½” x 7½” PCB > 90% efficiencyto be measured Multiple PCBsOne PCB Implemented RS-485 communication interface Complied with solar challenge regulations

4. Design Overview

5. Maximum Power Point P = IV Solar Cell I-V Characteristic Maximum Power Extraction

6. Smart Power Switching Circuit PIC Microcontroller

7. CurrentVoltage Smart Switching Demonstration

8. RS-485 Protocol Implementation This standard defines a physical layer The protocol was defined by the team This standard is responsible for communication between electrical systems in the car

9. Safety Precautions: Fuses and Connectors Over-current/voltage protection  Automotive fuse at input  Cylindrical fuse at output Touch-safe connectors Courtesy of Fall 2010 Solar Power Array Management Group.

10. Safety Precautions: Fuses and Connectors Illustration

11. Safety Precautions: Operational Maximum Voltage Maximum Current Input18 V9 A Output105 V3.5 A

12. Tested software by giving it simulated inputs that were out of range. Circuit shut down was indicated by the LED. Safety Precautions: Operational Demonstration

13. Safety Precautions: Zener Diodes The Zener diodes provide paths for current to flow in the event of an abrupt disconnection.

14. PCB Size Changes

15. Efficiency: Synchronous Rectifier Circuit efficiency was improved by replacing standard components with more efficient alternatives The standard diode was replaced by an ideal diode The design accommodated both alternatives in the following way: Losses ~ I 2 R DS(ON) Losses ~ V F I Ideal Diode from Inductor to Battery

16. Problems and Solutions o The holes on the PCB were drilled incorrectly Drilled bigger size holes by hand o Traces were conducting and leaking current Attempted to fix by hand, then determined it would be best to mill another PCB o Limited RAM on PIC Space-conscious coding

17. Final Cost of Design ComponentsUnitsUnit CostTotal Toroid Inductor2$ 9.56$ 19.12 Ideal Diode Controller2$ 3.40$ 10.20 Diodes (various)-- $ 15.30 Switches3$ 5.75$ 17.25 PIC Microcontroller1$ 4.32 Current Sensor3$ 4.52$ 13.56 Connectors (various)-- $ 11.11 MOSFET4$ 2.79$ 11.16 Oscillator1$ 2.13 Miscellaneous Components-- $ 16.40 TOTAL$ 120.55

18. Deliverables One working reproducible PCB PCB layout files and schematics Parts list Source Code RS – 485 Protocol

19. Present Status Testing PCB with solar array Testing efficiency of ideal diode Improving software robustness Combining algorithm and RS-485 code

20. Questions