Download Power Conversion for a Micro-Wind Turbine

Design and Implementation of a
Micro-Wind Turbine for the Union
College Campus
Kevin Donovan and Malysa Cheng
Advisors: Professors John Spinelli and Richard Wilk
ECE 498 Presentation
19 March 2009
Slide 1
10/21/2008
Union College
Project Goals
Generate a useable amount of electric power
Demonstrate turbine in a visible location on campus
Evaluate Union College’s potential for wind power generation
Design and manufacture a micro-wind turbine to generate
electricity for an on-campus application
Slide 2
10/21/2008
Union College
Wind Speeds at Union
Wind speeds are not
desirable for wind
power generation
Most wind speeds occur at 1 mph
Most high speeds occur at 3 mph
High gusts up to 56 mph
-% of the time speed is at 5 mph
Slide 3
10/21/2008
Union College
Wind Speeds at Union
Summer season is least
desirable
Winter Season better
for wind turbine
performance
Shows seasonal fluctuations in wind
speeds
Slide 4
10/21/2008
Union College
Wind Tunnel Testing
Clocking Issues
Needed 2nd
Generation Models
Successfully completed
rotations
Final design based off
2nd gen models
Too much
resistance with
torque setup
Slide 5
10/21/2008
Union College
Hybrid VAWT
Savonius Wind Turbines
Self Starting
Uses drag forces
Lower efficiency
Slide 6
10/21/2008
Darriues Wind Turbines
Not self-starting
Uses drag and lift forces
Highest VAWT Efficiency
Union College
Gear Ratio
Expect approximately 100 RPMs from wind
turbine
Beveled gear set
•Expensive
•Not easy to switch out
Chain and sprocket
•Cheaper
•Easy to switch out
sprocket sizes
Slide 7
10/21/2008
Timing Belt
•Cheaper
•Easier to switch out
Less noise than chains
V Belt
•Cheaper
•Easier to switch out
•Less noise than chains
•Less resistance
Union College
Electrical System
Alternator
Slide 8
10/21/2008
DC-DC
Rectifier Converter
Battery Bank
Inverter Load
Union College
Electrical System
Alternator
Wind
Slide 9
10/21/2008
Torque
DC-DC
Rectifier Converter
AC
DC
Battery Bank
Storage
Inverter Load
AC
Union College
Outlet
Electrical System
Alternator
Wind
Torque
DC-DC
Rectifier Converter
AC
DC
Inverter Load
Battery Bank
Storage
AC
•Design Goals
•Safely charge battery
•Broaden range of usable wind speeds
•Maximize system efficiency
•Synchronized data acquisition
Slide 10
10/21/2008
Union College
Outlet
Electrical System
Alternator
Wind
Torque
DC-DC
Rectifier Converter
AC
DC
Inverter Load
Battery Bank
Storage
AC
•Design Goals
•Safely charge battery
•Broaden range of usable wind speeds
•Maximize system efficiency
•Synchronized data acquisition
Slide 11
10/21/2008
Union College
Outlet
Generator Selection
Design Considerations
Generators vs. Alternators
Starting Torque
Direct-Drive vs. Gear-Drive
Power Curves
Conclusions
Alternators can produce three phase AC
More efficient
Allows for control over rectification
Low starting torque was critical
Single step gear
Unavoidable given project magnitude and
region’s average wind speeds
Needed higher voltages at lower speeds
Wind
Slide 12
10/21/2008
Torque
AC
DC
Storage
AC
Outlet
Union College
Source: Gin Long Permanent Magnet Generators
Site: http://www.ginlong.com
Generator Selection
Decision
WindBlue DC-540
Three phase AC
Rewound stator provides higher voltages at lower RPMs
12 V at 150 RPM
Low starting torque
Current vs. Torque
Voltage (V)
Current (A)
Voltage vs. RPMs
RPMs
Wind
Slide 13
10/21/2008
Torque (oz-in)
Torque
AC
DC
Storage
AC
Outlet
Union College
Source: Wind Blue Power
Site: http://www.windbluepower.com/
Alternator Testing
•DC motor used to drive alternator
•Required heavy-duty power source
•Power in, torque, RPM, and power out data
collected
•Used to create current, voltage, and efficiency
curves
Slide 14
10/21/2008
Union College
Rectification
Design Considerations
Three-phase AC output from alternator
Heat dissipation
Decision
Three-phase full-wave bridge rectifier
Large heat sink can easily dissipate expected
power levels
Wind
Slide 15
10/21/2008
Torque
AC
DC
Storage
AC
Outlet
Union College
Source: Lessons in Electronic Circuits
Site: http://www.ibiblio.org/kuphaldt/electricCircuits/Semi/03269.png
Source: Wind Blue Power
Site: http://www.windbluepower.com/
DC-DC Converter
Design Considerations
Wind speed is not constant
Alternator will output varying amounts of power
Union’s average wind speeds are low but not always
Battery bank requires different current ratings
Depends upon depth of discharge
Consistent overcharging of battery bank leads to premature failure
Charging voltage needs to stay within .7 V of the nominal battery
voltage
Voltage regulation is critical
Wind
Slide 16
10/21/2008
Torque
AC
DC
Storage
AC
Outlet
Union College
DC-DC Converter
Options
Linear voltage regulator
Simpler design
Input must be at least 3 V above output voltage
Low efficiency
Switch-mode power converter
Various topologies for outputs above or below inputs
High efficient
More complex
Decision
Buck/Boost switch-mode converter
Raises or lowers input voltage to obtain desired output
Controlled by altering switch duty cycle
Wind
Slide 17
10/21/2008
Torque
AC
DC
Storage
AC
Outlet
Union College
DC-DC Converter
Basic Topology
Vin
Vout
VOut  VIn
D
1 D
I   I In
1  D Out
D
where D is duty cycle
On State
Off State
Vin
Vout
Wind
Slide 18
10/21/2008
Torque
AC
Vin
DC
Storage
Vout
AC
Outlet
Union College
DC-DC Converter
Continuous Conduction Mode vs. Discontinuous Conduction Mode
Wind
Slide 19
10/21/2008
Torque
AC
DC
Storage
AC
Outlet
Union College
Source: Wiki Commons
Site: http://en.wikipedia.org/wiki/Buck%E2%80%93boost_converter
DC-DC Converter
Goals
•Operate in continuous conduction mode
•Maintain a low output voltage ripple
•Effectively regulate voltages between 9-15V to a nominal 12.5V
Design
VIn D
I Out D
L
C
f S I L
f S VC
Where fs is the switching frequency
IL is the inductor current ripple
VC is the capacitor voltage ripple
Wind
Slide 20
10/21/2008
Torque
MultiSim buck/boost schematic
AC
DC
Storage
AC
Outlet
Union College
Simulated Results
Slide 21
10/21/2008
Union College
Implementation
•
Switching frequency is limited by BASIC STAMP 2px PWMPAL coprocessor
–
•
•
Inductor series resistance is a serious limiting factor
Trouble driving power MOSFET
–
–
•
•
Duty cycle is controllable only up to 2kHz
Transistor capacitance slows turn-off time, limiting effective duty cycle
Driver ICs may increase performance
NS754410, used as a voltage-controlled switch, also exhibits slow shut off time
Current implementation only allows for output voltage adjustment up to +/-while
still operating in continuous conduction mode
Slide 22
10/21/2008
Union College
Battery Selection
Design Considerations
Charging safety
Batteries may be thoroughly discharged over lifecycle
Temperature
Decision
37Ah Sealed AGM battery
Robust to deep discharging
Superior cold weather performance
Cheaper than gel cell battery with
comparable performance
Wind
Slide 23
10/21/2008
Torque
AC
DC
Storage
AC
Outlet
Union College
Source: MK Battery
Site: http://www.mkbattery.com/
Inverter Selection
Design Considerations
Will determine power output quality
Sine Wave vs. Modified Sine Wave
vs. Square Wave
12v DC input, 120V 60Hz output
Decision
AIMS 300W pure sine wave inverter
Cost was comparable to modified
sine wave inverter
Will allow for more diverse loads
90% efficient
Wind
Slide 24
10/21/2008
Torque
AC
DC
Storage
AC
Outlet
Union College
Source: AIMS Power
Site: http://www.aimscorp.net/
Load Selection
Design Considerations
Contribute to campus in some way
Promote sustainability at Union
Relatively low power consumption
Decision
Programmable LED sign
Draws 1A at 120V 60Hz
Wind
Slide 25
10/21/2008
Torque
AC
DC
Storage
AC
Outlet
Union College
Datalogging
Design Requirements
• Synchronized sensing of wind speed, turbine RPMs, and charging voltage
• External storage for ease of use and large amounts of data
• Microcontroller-based
Implementation with the BASIC Stamp 2px
•NRG #40 anemometer outputs a frequency proportional to wind
speed
•Tested in wind tunnel,
•Accurate within 1 MPH
•Hall effect transistor used to sense turbine rotations
•Successfully implemented in tested against strobe tachometer
•Results were comparable
•Voltage sensing capability through operational amplifier circuit
and A/D converter
•Memory-stick datalogger successfully records data into a text
file for importation into Excel
Slide 26
10/21/2008
Union College
Source: Parallax
Site: http://www.Parallax.com
Continuing Development
• Buck/boost converter implementation
– Investigating better switch drivers
– Inductors with lower series resistance
• Integration with final micro-turbine prototype
• Demonstration on campus
Slide 27
10/21/2008
Union College
Budget
Mechanical
Cost
Electrical
Darrieus
Alternator
Wooden Skeleton
20.00
Top/Bottom Sheet
273.06
Cost
239.00
Rectifier with Heat Sink
14.00
Passive Components
Supplied by EE Dept.
Lexan Sheet
17.48
Board of Education
Supplied by EE Dept.
Shaft
84.91
BASIC Stamp 2ps
Supplied by EE Dept.
Savonius
Ribs
Blades
PWMPAL
26.02
101.70
Mounting/Gearing
160.00
Hall Effect Transistor
4.99
3/8” Magnet
Other
Nuts and Bolts
Anemometer
29.99
.79
30.00
AGM Deep Cycle Battery
73.66
125.00
Pure Sine Wave Inverter
134.00
LED Sign
Supplied by Facilities
Total
$1363.10
Slide 28
10/21/2008
Union College
References
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Kassakian, John. Principles of Power Electronics. Reading, MA:
Addison-Wesley, 1991
Ang, Simon. Power Switching-Converters. New York: Marcel Dekker,
1995
Lessons in Electronic Circuits,
http://www.ibiblio.org/kuphaldt/electricCircuits/Semi/03269.png
WindBlue Power, http://www.windbluepower.com/
Source: Wiki Commons,
http://en.wikipedia.org/wiki/Buck%E2%80%93boost_converter
MK Battery, http://www.mkbattery.com/
Gin Long Permanent Magnet Generators, http://www.ginlong.com
AIMS Power, http://www.aimscorp.net/
Parallax, http://www.Parallax.com
Slide 29
10/21/2008
Union College
Questions?
Slide 30
10/21/2008
Union College