Transcript Preliminary Design Review October 16, 2012 Christopher Corey, Josh Crowley, John Fischer, Tim Myers, Neil Severson, Kristine Thompson.

Preliminary Design Review
October 16, 2012
Christopher Corey, Josh Crowley, John Fischer,
Tim Myers, Neil Severson, Kristine Thompson
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Design and implement smart microgrid
energy delivery system
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Combine multiple/varied energy sources in
most efficient use of resources possible
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Utilize advantages and address drawbacks of
each source
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Intelligently match energy collection to load
requirement
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Design system to be as grid-independent as
possible

Develop innovative system that has ability to
combine sources and pursues intelligent
management of sources and loads

Team is varied in skill sets and fields of
interests
 Reflected in requirements and functional roles of
project
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Rwandan Orphans Project Catch-Up School
 Kigali, Rwanda
 Provide education for 200-300 orphans and local
community children
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Unreliable grid
Primary Goals
 Cheap operation
 Robust
 Simple
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Rise of renewable energy sources has
increased the popularity and practicality of
localized, grid-independent, and highly
efficient power systems

Flexible power solutions to meet needs in
many settings, including developing
countries
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Increase the effectiveness and efficiency of
small scale power systems

System concept able to supply steady power
to facilities such as schools, medical facilities,
and community centers in areas of expensive
and/or unreliable grid connection
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Convert solar and grid power to single
homogeneous energy carrier (DC bus)
Store energy in battery system for use when
resources are unavailable
Delivery energy to both DC and AC loads
Monitor load usage and display to user
through web interface
Ability to isolate system components for
protection
Predictive load profiling
 System mode control by the user
 Optimum power point tracking for solar
 Weather solar resource prediction
 Add scalability
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 Allow for multiple source possibilities
 System architecture may be followed for higher
power applications
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Load prioritization and control
• Two control signals
• Variable DC output to
bus/battery voltage
• AC constant voltage
output to bus
• 2 Charge Controllers
• Bridge Rectifier
• Charge Controller
• 3 control signal
outputs, one control
input from Linux
Server
• Load data output to
Linux Server
• Current and voltage
measurements from
AC Rectifier, solar
converter
• State of charge and
load monitoring input
for decision making
• Separate in-line SCRs
for load control
• Monitoring hardware
with output to
controller
• Spec’d for max draw
of 55W and up to 4
loads
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Monocrystalline
 Most efficient
 Most expensive
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Polycrystalline
 Less efficient than mono
 Less expensive
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Thin Film
 Lowest efficiency and density
 Least expensive
 Potentially available from University
Lead-acid for best emulation of
large scale implementation
 AGM deep-cycle
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 Maximum safety
 Low self-discharge
 Low hydrogen emission
 High charge rate
 Maintenance free
 Deliverable by UPS
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Responsible for drawing and converting
power from the solar panel, outputting to
power bus without overcharging battery
Solar
Panel
Variable
DC
Solar
Converter /
Charge
Controller
Battery
Voltage DC
Power Bus
Battery
Voltage DC
Battery
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Implemented as DC-DC switching converter
 Buck/boost to be determined by solar panel
voltages
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Output voltage is controlled by the power bus
 Set by the battery voltage
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This, duty cycle from controller, and
converter M(D) set the PV operating point
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Prevent overcharging of battery with charge
controller
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Solar panel may be producing power even
though battery is at max capacity
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Must also prevent power from flowing back
into panel during times of no insolation
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Responsible for drawing energy from grid
when deemed necessary, outputting to
power bus without overcharging battery
120V 60Hz AC
AC Grid
Grid
Rectifier
Battery
Voltage DC
Power Bus
Battery
Voltage DC
Battery
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Implemented using a full-wave rectifier and
switching (buck) regulator
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Will receive an input from the controller
dictating whether it is in operation
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The grid rectifier must also make sure to not
overcharge the battery using a charge
controller
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Design will be similar to the solar energy
charge controller
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System control should prevent excess power
to battery, but a safety backup is needed
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The two charge controllers must also make
sure to not exceed the maximum charge rate
of the battery with their combined output
currents
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Design will keep testability in mind
 Allow for subcomponents to be tested on their
own
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Ex: Converter will be capable of being tested
without solar panel input or charge controller
output for proper DC-DC conversion
 Verify small pieces of functionality individually
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Design somewhat hinges on choice of solar
panel
 Operating voltage range dictates converter type
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Currently some of most difficult / high risk
components
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Project hinges on success of this subsystem
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Brain of operation
 Central controller
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Controls the inputs to provide appropriate
power to the loads and battery
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Current and voltage measurements from the
solar panel
Current readings from the grid connection
State of charge of the battery
User inputs
Web interface settings and readings
Load monitoring measurements
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Load control – on/off
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Data to the web interface
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Solar panel / converter control
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Rectifier control (on/off)
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Calculating available power from input sources
Power point tracking (PPT) for solar panel(s)
Calculating required power to be delivered
Controlling external hardware
 AC grid connection
 Solar converter / power point tracking
 Includes turning off inputs with insufficient power
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Reporting data to the web interface
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Change of operation based on user mode
Load priority control
Use predictive models as an input for a higher
efficiency system
 If it is going to be sunny all day, don’t use the grid to
charge the battery the night before
 If the grid is unreliable on Tuesdays, charge the
battery in advance
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Enable optimum power point tracking when
appropriate
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GPIC – General Purpose Inverter Controller
 National Instruments power controller board
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Microcontroller and custom PCB
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General Purpose Inverter Controller
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Robust device for controlling grid tied and
high power systems
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Built in FPGA
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Real time operating system
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Power protocol support
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Advantage
 Simplifies a lot of implementation
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Disadvantage
 No design experience with a microcontroller
 Far more robust than our product needs
 Unit cost would be high since the GPIC is
expensive
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Advantages
 More design experience
▪ Board design
▪ High power considerations
▪ Choosing the right microcontroller
 Much more cost effective implementation
▪ Options we don’t need can be eliminated
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Disadvantages
 Large added effort to the system design and
implementation
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Testing will be divided into each subsystem of
control
 Example: power point tracking can be tested by
testing a closed loop converter circuit with bench
top power supply
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There are no required parts for initial design
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After PCB fabrication, packages must remain
the same for easy integration
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Web interface does not require specialized
software for access
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Enables monitoring of load power
consumption
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Load Management (On / Off)
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Load profiles, for automatic power
management
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Solid State Relays
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Non-invasive current
sensing
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Beagle Bone
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Arm Cortex A8
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Has a webserver preinstalled, running on
the Angstrom Linux
distribution.
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Serial UART, I2C, SPI
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Sept 25
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Critical Design Review (CDR)
Dec 13
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Demonstration of major hardware and software
components and subsystems critical to major
functions.
Web Interface
Power Point Tracking
Inverter, Converters, Rectifier
Dec 6
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Proof-of-Concept Bench Testing
Power Point Tracking- Optimum and Peak
Switching - Converter Manipulation
Apache Server for Web Interface Current Monitoring
Nov 15
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Functional Decomposition Complete
Functional Decomposition to Level 3
Nov 6
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Preliminary Design Review
Present Functional Decomposition Level 0 and 1
Oct 23
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Proof-of-Concept Open Lab Symposium
Jan 17
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Final Architecture and Requirements Specification
Complete
Jan. 24
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Oct 16
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Initial Requirements Specification and Use Case
Models
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Detailed Design Draft
Software Implementation design
Order PCBs / Complete BOM
Feb 7
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Bench Testing of Prototype Whole System
(Hardware and Software)
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Feb 21
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Mar 7
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Complete test analysis and report results
Develop initial integration test plan
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Mar 14
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Mar 21
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Final integration test plan complete
Complete integration testing
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Apr 11
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Apr 25
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Final Demonstration (EXPO) Testing
EXPO - Demonstration for Public.
May 2
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Complete all technical documents
Appendix II: Division of Labor
Task
Primary
Secondary
Network Interface
John Fischer
Kit Corey
Load Monitoring
Christopher Corey
None
Controller H/W
Kristine Thompson
John Fischer
Solar Charge Controller
Josh Crowley
Kristine Thompson
Rectifier Charge Controller Tim Myers
Neil Severson
Peak Power Point Tracking Tim Myers
Josh Crowley
Controller S/W
Architecture
Christopher Corey
Neil Severson
Item
Item Total
Implement Solar
660
Load Measure and Monitor
300
Controller Implementation
568
Rectifier, Converters, and Inverter
Implementation (Each)
1236
Energy Storage
230
Web Interface Implementation
120
User Interface
390
Margin
300
Total
3804
Area of Risk
Contingency Plan
Controller processor not robust
enough to handle software scheduling
requirements
Controller selection will be based on
robust software specification, code will be
written with efficiency in mind
Five boards to be developed:
• Scheduling constraints for system
integration
• High cost of error
Extensive prototyping combined with
major development focus will ensure
efficacy
Subsystem implementation could
prove to be infeasible
These could be implemented with retail
products if absolutely necessary
Smart control algorithm development
requires working implementation of
hardware; can only be tested late in
development cycle
High level algorithm development is easy
to scale for implementation, modeling will
allow code development to begin prior to
full hardware completion
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High currents and voltages in use throughout
design
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Each board will use over-current protection
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System will use “breaker box” to ensure
modularity, provide additional protection
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Safe usage practices will protect group
members
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Component redundancy for critical blocks
 Batteries
 Solar panels
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Efficiency of individual parts determines
overall system efficiency
 Not critical for basic goals
 Critical for reach goals, overall system efficacy
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Efficiency makes up for cost of
implementation in time
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System components will eventually fail
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Boards can be re-spun– no relying on
manufacturer supply availability
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Disposability always a problem for PCBs and
semiconductor materials
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Fully utilize heterogeneous energy sources
Store energy intelligently
Supply power to variable loads
Smart control to increase total system
efficiency
Adaptable to loss of individual power sources
User monitoring and control
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Most systems of this type cannot deal with
multiple power sources simultaneously
A new and more effective implementation of
popular technology
Energy independence with reliability
Scalability and adaptability
Use in developing countries