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BIWT :: Blade Induction Wind Turbine. Team 25 (Steven Pitula , Scott Chen, Sangmin No). Presentation Outline. Introduction Features / Benefits System Overview Individual Part Description with Testing Verification Physical Turbine & Power Conversion System Battery Charging System
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BIWT :: Blade Induction Wind Turbine Team 25 (Steven Pitula, Scott Chen, Sangmin No)
Presentation Outline • Introduction • Features / Benefits • System Overview • Individual Part Description with Testing Verification • Physical Turbine & Power Conversion System • Battery Charging System • Tachometer & Braking System • Limitations / Improvements • Ethical Consideration • Q&A
Introduction • BIWT provides eco-friend and efficient solution for current wind turbine manufacturer • The main goal of BIWT is to increase total power produced by wind turbines through the use of electromagnetic induction in the bladesand smart controlling system.
Features & Benefits • Features • Generating extra power in terms of electromagnetic induction • Power conversion • Smart Operation monitoring and controlling (rpm, power output, charging) • Benefits • Clean and renewable energy source • Value for money through efficient power generation • May be implementable on current wind turbines
System Overview – Components • Physical Turbine & Power Conversion System • Induction blades, DC generator • Rectifier, Boost Converter • Battery Charging System • Charge controller • 6V/12V lead-acid battery for storage • Tachometer & Braking System • PIC16F877A • Tachometer
The Turbine • Wood • PVC • Aluminum
Induction System Solenoid length = 4 inches Magnet path = 12 inches The solenoids are connected in series and are positioned at the ends of the blades
Solenoid Testing • 3Vpp up to 10 RPM • 3.5 Vpp from 10 to 30 RPM • Magnets do not move • above 30 RPM
Rectifier and Filter The full-wave rectifier is made of 4 schottky diodes and the filter is a 1mF capacitor
Rectifier/Filter Testing Input = 3 Vpp20Hz Output = 1.15 V 40Hz Vdrop = 0.35V Vripple = 4.9%
Boost Converter • 200uH inductor • 1mF capacitor • Schottky Diode • Transistor
Boost Converter Testing Efficiency: 15%
Efficiency Losses Pac = Pbc * Erec * Eboost Erec = 71% Eboost = 15% Etotal = 10.5%
Battery Charging System - Overview • Store the power output from wind turbine • Charge controller to choose right storage according to power output from the turbine • Charging controller to maximize charging efficiency and protect the battery and circuit • 3 charging methods • Below 13.5V : Charge 6V lead-acid battery • From 13.5V to 15.1V : Charge 12V lead-acid battery • Over 15.1V : Go to dummy load
Battery Charging System – Storage • Battery Selection • 6V lead-acid battery from Power-Series : 7.0Ah • 12V lead-acid battery from Power-Series : 8.0Ah • Required Charging Current Calculation • 6V lead-acid battery : 7.0Ah / 10Hr battery charging time = 0.7 A required : 8.0Ah / 10Hr battery charging time = 0.8 A required
Battery Charging System – 1st Design • 1st Design • Charge 12V lead-acid battery • Use LM 317 voltage regulator • Assume rectified DC Voltage Input to the regulator • Reasons for Design Failure • Lower power output than we expected • Minimum 18V required for LM 317 • Need to modify the circuit for charging 6V battery • Varying DC power output from wind turbine • Potentiometer
Battery Charging System – 2nd Design • 2nd Design • Multiple charging options • Use LTC 1042 monolithic CMOS window comparator • Assume rectified DC Voltage from the DC generator • Reason of Design Failure • Sudden change of turbine motor • Results change in power output • Testing
Tachometer • Built in contactless tachometer • RPM = revolutions per minute • Design requirements: • 5% margin of error vslaser tachometer reading • LCD display • Controls braking system • Additional features: • Average RPM with user reset
Reference1 Original Schematic
Early Design Approach • RPM = • Reduce variables • Circuit Requirements • Accurate time detection • Accurate revolution detection • Large number division • TTL? • Solution = embedded systems microcontroller
PIC16F877A • 8 bit , 256 bytes EEPROM peripheral interface controller • MPLAB IDE / CCS compiler • Up to 20 MHz external CLK • Useful functions • CCP (capture and compare) • 3 timers (scalable) • Interrupt friendly
Timer1 • 16 bit register • Time = (# of counts)x(frequency of counts) • Time = 2^16 x increment frequency • setup_timer_1(T1_EXTERNAL | T1_DIV_BY_8); • Timer 1 increment frequency = 500 khz • Overflow • #int_timer1 : of_count = of_count + 1; • Extend timer1 by 16 bits • Total Time = [2^16x (overflow count) + (Timer1 count )] x increment freq • Time for overflow ~ .131 seconds
CCP1 and RPM equations • Capture Timer 1 on interrupt from pin17 • current_ccp = CCP_1; • setup_ccp1(CCP_CAPTURE_RE); // rising edge triggered • Allows us to measure time between interrupts • Sets sensor requirement: 1 low to high transition per revolution • RPM = 1/[(2^16 x overflow count + captured timer1 count)/60] • AVGRPM = (((x*AVGRPM) +RPM)/(x+1)); x = x+1; • User push button interrupt reset x • CCP guide *(reference 3)
LCD 16x2 • LCM –SO SO1602D SR/A LUMEX (testing LCD) • HD 44780 controller LCD front panel • Parallel: 4 data inputs / 2 control lines from pic • Modified Flex_LCD driver *(reference 2) • 500 ms delay • Example print format: printf(lcd_putc,"\fRPM: %f\n",RPM); printf(lcd_putc,"AVG: %f\n",AVGRPM);
Braking System • Old braking system: mechanical friction based • Maximum RPM set in code • When tachometer calculates RPM >= Maximum RPM: • Power mosfet IRL 520 is turned on, LED lights up • Generator terminals shorted • RPM decreases, held in brake mode for 3 seconds • RPM is cleared, brake is removed • Recheck RPM • Reapply brake or do nothing
Tachometer Fabrication and Testing • Modular approach • LCD constant LCD variable CCP Timer1 RPM (fxn generator) AVG RPM (fxn generator) sensor RPM and AVG RPM (sensor) = Final Product • LCD output test variables vs assembly debug • Over 11 code versions / 35 word pages of debugging procedures • Debugging procedure and documentation: • Problem/Symptom? Identify associated variables • Output to LCD + check • Solution? Modify code / recheck
Sensor Design and Testing • Old design: reed relays • New design: optical sensor • TX / RX pair RX high impedance 1.5 M Ω • From testing: no voltage change (reflective tape) point TX directly at RX .04v voltage change • Use 110 lab optical sensor: OPB607a • Measurements 2mm away • Vambient: 4.63v Vblacktape: 4.81v Vreflectivetape: .84 • PIC: detects high / low / high transition without debouncing
Key Breakthroughs Debugging • LCD variable output: simple counter with 2 variables • Symptom: counter would stop or reset, shifting breadboard • Possible causes: loose pin connections, bad hardware, bad code
Additional Breakthrough Debugging • AVG RPM function (with fxn generator) • AVG RPM = # of revolutions / [total elapsed time / 60s] • Symptom: AVG RPM not displaying correct value - display interrupt count (# of revolutions) and time count increments - set fxn generator to 1 hz (frequency of interrupt) - interrupt count fine , timer count is incrementing too slowly - possible cause : total time elapsed counter or algorithm issue - check code problem: every CCP interrupt resets timer1, total time is innacurate • Solution: AVGRPM = (((x*AVGRPM) +RPM)/(x+1)); x = x+1; • X will be reset by user push button
Testing and Results • Finished RPM detection Circuit (fxn generator input) • RPM = Frequency x 60
Testing and Results • Final product testing:
Braking System Test • Maximum RPM set in code • Demo : 3000 rpm • Test: Max RPM set to 100 • Source drain impedance switch off (20.18 Ω) • Source drain impedance switch on (.17 Ω) • Drive voltage increased till >100 RPM, LCD display 98 RPM • Brake applied for 3 seconds, RPM drop to 31, led on • Brake disengaged and re-engaged when drive voltage held constant
Limitations and improvements • Generator • Coupling System • Solenoid System • Power Conversion • Charging Circuit
References • 1) http://electroschematics.com/451/digital-bike-tachometer/ • 2) http://www.ccsinfo.com/forum/viewtopic.php?t=30964 • 3) http://www.ccsinfo.com/forum/viewtopic.php?t=29963&highlight=ccp
THE END Thank You