Transcript Power Melder Midterm Presentation

Power Melder
Midterm Presentation
SEPTEMBER 25, 2008
About Us
Christopher
Harper
EE
Power
conversion
electronics
Tina
McGlaston
CPE
Isolation/ADC
/Humaninterfacing
Daniel Wilson
CPE
Tyler Pettit
EE
Firmware/Hu
maninterfacing
Power-factor
correction
Overview
 Current Problem
 Solution
 Constraints
 Practical Constraints
 Technical Constraints
 Approach and Trade-off Analysis
 Power-Factor Correction
 DC-DC Converter
 External ADC
 Opto-coupler
 Microprocessor
 Progress
 Timeline
 Questions
Current Problem
 Small generators cannot 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
System Overview
Power Melder System
μC
LCD
Keypad
Generator
Generator
DC-DC
Converter
DC-DC
Converter
Output power bus
System Overview
DC-DC Converter Subsystem
Master/Slave bus
ADC
Bridge
From
generator rectifier
μC
Power
factor
correction
DC-DC
converter
Shunt
resistor
Output
bus
Practical Constraint: Economic
Yamaha
2500 Watt
Power Melder
Generator
The Power Melder must cost
less
than
a
typical
consumer
• Must cost no more than
Subaru
1400 Watt
typicalgenerator
generators
with anwith similar capacity.
Generator
with
inverter
• Adds the extra benefit of
an
inverter
with
Inverter Technology
$1500
Inverter Technology
•$1000-$1500
Mitsubishi 2500 Watt Generator
$1000
$825
[1]
Practical Constraint: Safety
 Input Isolation
 Fuses
 Conductor Separation
Voltage Between Conductors
( AC Peaks or DC Volts )
Minimum Bare Board Spacing
B1
B2
B3
B4
…
…
…
…
…
301-500
0.25mm (.01 in.)
2.5mm (.1 in.)
12.5mm (.492 in.)
0.8mm (.0315 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
[2]
Technical Constraints
Name
Description
Input Power
Must accept 90-300V DC or AC 50200Hz
Output Power
Must provide a single output DC bus
between 12V and 14.5V for use with an
AC inverter
Output Stability
Must be stable to within 10% of
nominal value with a maximum of 10%
ripple
Accuracy
Measured power draw and power
limiting must be accurate to within 10W
Power Capability
Must be capable of drawing 150W from
any acceptable power source
Power Factor Correction
 Bridge Rectifier
 AC to DC
 Current pulses at voltage
peaks
 Poor power factor

Current spikes stress generator
Power Factor Correction
 Passive Power Factor
Correction

Inductor used to shape
current
Large inductor required
for high power
applications
 Increased weight
 Increased cost

 Active Power Factor
Correction

IC used to shape current
Low cost
 Compact and lightweight
 More accurate current
shaping

Power Factor Correction
 Applicable Constraints
Input Power: Must accept 90-300V DC or AC 50-200Hz
 Power Capability: Must be capable of drawing 150W from
any acceptable power source

 LT1249 Power Factor Controller
Built-in peak current limiting
and over-voltage protection
 100kHz switching frequency

DC-DC Converter Topology
 Applicable Constraints
Output Power: Must provide a single output DC bus
between 12V and 14.5V for use with an AC inverter
 Power Capability: Must be capable of drawing 150W from
any acceptable power source
 Output Stability: Must be stable to within 10% of nominal
value with a maximum of 10% ripple
 Cost: The Power Melder must cost less than a typical
consumer generator with similar capacity.

DC-DC Converter Topology
Topology
Cost*
Output
Power
Flyback
Half-Bridge
Full Bridge
Forward
Forward (double
switch)
* Cost for high output power, low volume; more stars means cheaper
Ripple
Fault
Protection
Analog to Digital Converter
Used to sense input voltage of the generators
Applicable Constraints:
• Measured power draw and power limiting must be accurate
to within 10W
LTC2309
 12 bit resolution
 I2C compatible
 Low power: 1.5mW at 1ksps
 Fast Conversion Time: 1.3µs
Opto-Coupler
Opto-coupler
•Isolates two circuits
•Passes signals without
allowing electrons to move
between circuits
Components of the Opto-Coupler
•LED
•Phototransistor
[3]
Microcontroller
 Microchip PIC24HJ32GP202
[4]
Progress: 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
Progress: 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
Progress: 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
Progress: Power Factor Correction
Power Melder PFC Stage
Progress: Power Factor Correction
Input Voltage =
177VAC, 60Hz
LT1249 Current Shaping
Progress: DC-DC Converter
Timeline
September
Hardware Design
Prototype Boards
Single Unit
Testing
System Testing
Software
October
November
References
 [1] http://www.stmicroelectronics.com/stonline/
books/pdf/docs/3721.pdf
 [2] http://pcbwizards.com/
 [3] http://www.mech.uwa.edu.au/
 [4] PIC24HJ32GP202 datasheet.
http://www.microchip.com/
 Questions?