Download Solar Power Array Management for the Solar Racing Team

Maximum Power Point Tracking
System for Solar Racing Team
Andrew Matteson
Ingrid Rodriguez
Travis Seagert
Giancarlo Valentin
March 14, 2011
GT Solar Jackets
School of Electrical and Computer Engineering
Georgia Institute of Technology
Project Overview
• Customized smart switching power system
to charge car batteries with solar energy
• Intended for use by the Solar Jackets in
the World Solar Challenge 2011
• Estimated material cost: $194 per unit
Prior Work: Fall 2010
• Initial design adaptable to varying sunlight
variations
• Designed for different battery and array
specifications
• Contained one power switching circuit per
board
Design Objectives: Spring 2011
• Minimized PCB layout area
• Efficiency > 90%
• Implement RS-485 communication interface
• Comply with solar challenge regulations
Design Overview
Maximum Power Extraction
Maximum
Power
Point
P = IV
Solar Cell I-V Characteristic
Smart Power Switching Circuit
P&O Tradeoffs
Advantages:
• Simple to
implement
• Popular algorithm;
open-source code
available
• Highly adaptive
Disadvantages:
• Inevitable
oscillation around
the maximum
power point
• May interpret local
maximum as the
absolute maximum
RS-485 Protocol Implementation
• This standard defines a physical layer
• The protocol will be defined by the team
• This standard will be responsible for
communication between other electrical
systems in the car
Operational Safety Precautions
• Gradual shutdown by intentionally deviating
from maximum power point
• Maximum voltage
• Input: 18V
• Output: 105V
• Maximum current
• Input: 8.5A
• Output: 3.5A
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.
Safety Precautions: Zener Diodes
The Zener diodes provide paths for current to
flow in the event of an abrupt disconnection.
Efficiency: Synchronous Rectifier
• Circuit efficiency can be improved by replacing standard
components with more efficient alternatives
• The standard diode can be replaced by a synchronous rectifier
• The current design will accommodate both alternatives in the
following way:
Losses ~ I2RDS(ON)
Losses ~ VFI
Design Challenges and Tradeoffs
Georgia Tech PCB Machine
• Dimensions (10.5 in x 7.5 in )
• This constraint dictates how many MPPT
circuits can fit onto a single board (currently
two)
• Using a different machine would introduce
significant additional costs.
Design Challenges and Tradeoffs
Bounding Simulation Parameters
• Exhaustive circuit simulations cannot be
performed for the full range of variable
parameters
• As a result, the circuit’s values are only
approximations of the ideal optimal
components
Product Delivery
• Scheduled delivery for Monday April 25, 2011
• Fully tested reproducible boards
• Preprogrammed with microcontroller code
• Include mechanical switches for easy control
Future Work Schedule
• March 18, 2011 – First Prototype
• April 01, 2011
– Design Tests for Prototype
• April 15, 2011
– PCB Re-Design
• April 20, 2011 – Final Build
• April 22, 2011
– Final Design Tests
• April 25, 2011
– Deliver Completed Board
RS-485 Demonstration
Questions