Download Power Melder Midterm Presentation

Power Melder
Midterm Presentation
SEPTEMBER 25, 2008
About Us
Christopher
Harper
Tina
McGlaston
EE
CPE
Daniel Wilson
Tyler Pettit
CPE
EE
Overview
 Current Problem
 Solution
 Constraints
 Approach
 Power Hardware
 Microprocessor
 Progress
 Questions
Current Problem
 Small generators can not power large loads.
Solution
 Parallel power generation
Current Solutions
 Honda EU1000iA
 1 kW generator, may be paralleled
 Input generators must be identical (same output power)
 Must be Honda generators
Economic
Yamaha 2500 Watt
Generator
The Power Melder must cost
with Inverter Technology
less than a typical consumer
Subaru 1400 Watt
generator with similar capacity.
Generator with
$1500
Inverter Technology
Mitsubishi 2500 Watt Generator
$1000
$825
Images, Prices from:
http://www.electricgeneratorsdirect.com
Safety
 Input Isolation
 Fuses
 Conductor Separation
Voltage Between
Conductors
( AC Peaks or DC Volts )
Minimum Bare Board Spacing
B1
B2
B3
B4
0-30
0.05mm (.002 in.)
0.1mm (.004in.)
0.1mm (.004 in.)
0.05mm (.002 in.)
31-50
0.1mm (.004 in.)
0.6mm (.024in.)
0.6mm (.024 in.)
0.13mm (.005)
51-100
0.1mm (.004 in.)
0.6mm (.024 in.)
1.5mm (.06 in.)
0.13mm (.005)
101-150
0.2mm (.008 in.)
0.6mm (.024 in.)
3.2mm (.126 in.)
0.4mm (.016 in.)
151-170
0.2mm (.008 in.)
1.25mm (.05 in.)
3.2mm (.126 in.)
0.4mm (.016 in.)
171-250
0.2mm (.008 in.)
1.25mm (.05 in.)
6.4mm (.252 in.)
0.4mm (.016 in.)
251-300
0.2mm (.008 in.)
1.25mm (.05 in.)
12.5mm (.492 in.)
0.4mm (.016 in.)
301-500
0.25mm (.01 in.)
2.5mm (.1 in.)
12.5mm (.492 in.)
0.8mm (.0315 in.)
>500 add --->
0.0025mm/volt(
.0001in.)
0.005mm/volt(.0002
in.)
0.025mm/volt(.001
in.)
0.00305mm/volt(.0001
2 in.)
B1 - Internal Conductors
B2 - External Conductors, uncoated, Sea level to 3050m ( 10K ft.)
B3 - External Conductors, uncoated, over 3050m ( 10K Ft.)
B4 - External Conductors, coated with permanent polymer coating
Table from
System Overview
Power Melder
Generator
#1
Master uC
PFC
DC-DC Converter
Generator
#2
PFC
DC-DC Converter
Inverter
Power Factor Correction
 Power Factor
 Ratio of real power to
apparent power
 Ideal situation
Unity power factor
 Current replicates voltage
(phase and shape)
 Load appears purely
resistive
 No reactive power drawn

Power Factor Correction
 Bridge Rectifier
 AC to DC
 Non-linear current pulses
 Poor power factor

More line current to produce
same output voltage
Power Factor Correction
 Passive Power Factor
Correction

Inductor used to shape
input current
Large inductor required
for high power
applications
 Increased weight
 Increased cost
 Unregulated output
voltage
 Requires switch for
multiple input voltages

 Active Power Factor
Correction

IC used to shape input
current
Low cost
 Convenient size
 Stable output voltage with
small ripple
 Over-voltage protection
 Input current limiting

Power Factor Correction
Active PFC
Passive PFC
No PFC
Image from: http://www.pcpower.com/prod_revs/pcp_silencer/Oscope_web.jpg
Power Factor Correction
 LT1249 Power Factor Controller
 Peak current limiting
 Over-voltage protection
 100kHz switching frequency
 Low start-up current
 No switch required for multiple input
voltages
Power Factor Correction
Power Melder PFC Stage
Power Factor Correction
Input Voltage =
177VAC, 60Hz
LT1249 Input Voltage/Current and Output Voltage/Current
Power Electronics
 Flyback topology.
 Simple, Commonly used
 Low parts count
 High Ripple
 Requires relatively
large transformer
Image from:
http://www.powerdesigners.com/InfoWeb/design_center/articles/DC-
Power Electronics
 Half-Bridge topology.
 Relatively high power
 Efficient
 Large capacitor
currents
 Requires complex
control circuitry
Image from:
http://www.hills2.u-
Power Electronics
 Full-Bridge topology.
 Extremely high power
 Very Efficient
–Highest parts count
–Requires complex control
circuitry
–No control circuitry fault
tolerance
Image from:
http://www.hills2.u-
Power Electronics
 Double-switch forward topology.
 Isolated (safe)
 Efficient
–Medium
 Cost-effective
power
–Very uncommon
Image from:
http://www.stmicroelectronics.com/stonline/books/pdf/docs/3721.p
Isolation Digital Control Lines
GALVANIC ISOLATION
•Isolating functional sections of electric systems
•Low speed
•High power
•Communication between multiple
OPTO-COUPLER (OPTO-ISOLATOR)
•Uses a beam of light to transmit the signals or data across an electrical barrier
•High speed
•Low power
•Small size
•Achieves excellent isolation
Opto-Coupler
Components of the Opto-Coupler
•light emitting device
•light sensitive device
Analog to Digital Converter
Used to sense input voltage of the generators
LTC2309
 12 bit resolution
 I2C compatible
 Low power: 1.5mW at 1ksps
 Fast Conversion Time: 1.3µs
Microcontroller
 Microchip PIC24HJ32GP202
MCU Firmware (Converter)
ADC Interrupt
Serial comm task
Timer Interrupt
Init frozen?
Copy ADC value
into memory
Reset ADC
Wait for serial
command
Init task
no
Signal init
semaphore
Process
command
Main
frozen?
Return any
requested
data
yes
no
Signal main
semaphore
Wait on
semaphore
Init PWM duty
cycle and start
PWM
Unfreeze main
task and freeze init
task
MCU Firmware
(Converter cont’d)
Main task
Calculate output
voltage from ADC
value
Wait on
semaphore
Calculate input
voltage from ADC
value
Voltage
too low?
yes
Voltage
too high?
yes
no
Voltage
too
high?
no
Turn off
PWM
Send
message to
master
no
Voltage
too low?
no
yes
Freeze main
task
Decrease
PWM duty
cycle
yes
Increase PWM
duty cycle
MCU Firmware (Master)
Main task
Wait on
semaphore
Query current
contributions
Read voltage of
ouput bus
Voltage
too high?
yes
Send decrease
command to
all
no
no
Send
correctional
commands
no
Voltage
too low?
Contr.
correct
?
yes
Send increase
command to
all
yes
 Questions?