1. A NOVEL INTEGRATED AC/DC/AC CONVERTERS FOR DIRECT DRIVE PERMANENT MAGNET WIND POWER GENERATION SYSTEM by SHEELA AROKIA MARY . J M.E ( EMBEDDED SYSTEM TECHNOLOGIES) Under the Guidance Of Mr.S.Sivasakthi M.E.,M.B.A., Associate Professor Head of the Department Department of EEE

2. To reduce the switching loss & Minimize the circulating current in the power converters used in Wind power generation system and to improve the Power factor & overall performance of the system. 3. 24 switches are used in Power converters. Separate stabilizing circuit is used to maintain stable voltage. Presence of Harmonics, Switching losses & Circulating current is high. No Power factor improvement. 4. 9 switches are used. Switching losses are reduced. Circulating current is minimized. Less harmonics. Power factor improvement is made. 5. Whenever we turn on & turn off the Switches, Certain amount of power will be consumed by the switches that loss is the switching loss. Switching loss depends on Switching frequency. Switching frequency : for a min how many times we turn on & turn off the switches. fsw = 30 KHz , time = .03ms When the number of switches increases switching frequency will be high, when switching frequency increases , switching losses will be high Hence by reducing the number of switches from 24 to 9,obviously switching loss are reduced. For switches IGBT is used 6. The current that circulates among power switching devices. It occurs when the output current is 30 degree out of phase with the output voltage. The presence of circulating current , increases the current flow , produces more heat and increases the switching losses. In order to minimize , IGBTs & Diodes are used. Initially they have the reverse blocking capacity & allows unidirectional power flow, so the arrangement of these IGBT Switches and diodes minimize the circulating current. 7. Distortion in AC waveform. Occurs due to noise & some sort of disturbance. The presence of harmonics causes vibration & the equipments deliver a wrong diagnostic results. Types : Odd Harmonics 1f, 3f, 5f.. Even Harmonics 2f, 4f, 6f. f fundamental frequency of 50 Hz Here we minimize odd harmonics of 150 Hz by using LC filters. 8. The output of the wind turbine depends on speed of the wind, but while connecting to load or grid , a stable voltage must be maintained. At present a separate stabilizing circuits or stabilizers are used . To turn on & turn off those circuits , switches are used and switching frequency increases & as a result switching loss increases. So in this project in order to maintain stable voltage , Vienna rectifier is used in the rectification side. The Vienna rectifier has the property of producing stable DC voltage and without boost converters it produces a slight increase in voltage with the presence of 3 switches 9. In AC circuits generally there will be a phase difference of between the voltage & current, cos of that is represented as Power factor. Loads : Inductive & Capacitive loads Inductive loads The current lags the supply voltage , so lagging power factor. Capacitive loads The current leads the supply voltage, so leading power factor. In this project , due to the presence of the converters & inductive load , we have lagging power factor. 10. Lagging power factor occurs due to the presence of reactive power. Reactive power Artificial power, it is neither consumed nor does any useful work in the circuit, simply flows front & back in the circuit. The presence of reactive power , increases the current flow, produces more heat & additional losses, so its important to maintain PF as close as to unity. To improve the PF 3 static capacitors, each of 1000F is connected in parallel to the load in Vienna rectifier. The capacitors produces a leading current & neutralizes the reactive component & increases the power factor (PF). 11. PHASER DIAGRAM POWER TRIANGLE 12. This proposed system has AC/DC/AC converter. In existing ac-ac converter topologies, 2 level 6 switch comprising a common dc link capacitor & VSI are frequently used In order to minimize the switching loss & circulating current , we are implementing a topology consisting of 9 switch USMC for wind energy conversion system. The USMC consist of 3 switch Vienna rectifier at the rectification side & 6 switch inverters in the inverter stage. 13. The Vienna rectifier converters the unstable AC to a Stable DC voltage with Power factor improvement & using inverters the stable DC is converted to stable AC voltage. By reducing the number of switches to 9 , the switching losses are reduced & because of the unidirectional power flow , the circulating current is minimized. By improving the power factor from 0.8 to 0.9, the efficiency is improved to 90%. 14. For simulation, PWM using PI Controller Technique. PWM For giving gate pulse to the power converters at regular intervals. PI Controller To control the Voltage & Current. Advantage Zero steady state error, value 0.67 Closed loop is used Voltage Stabilizes faster. 15. It converts wind energy into mechanical energy. Types horizontal axis wind turbine & vertical axis wind turbine. Efficiency & Power generation of wind turbine depends on the height of the tower & speed of the wind. Direct drive- Without using gear box , the rotor shaft of the wind turbine is directly coupled with the generator. Because of not using gear box, in order to maintain the synchronous speed of the generator , PWM technique is used. 16. It converts the mechanical power output of wind turbine into electrical power. Principle-Faradays law of electromagnetic induction. Can be extremely large power ratings up to 1500MW They are known as synchronous machines because they operate at synchronous speed (speed of rotor always matches supply frequency)Ns=120 f/p. Instead of field winding, permanent magnet is used. Does not require DC supply, Condenser not needed. So output power is fully utilized and total loss is reduced, higher efficiency. 17. Unidirectional 3phase AC/DC converter. 3 power switches. PF improvement Harmonics are reduced. 18. 3 phase AC source LC Filter Solid state switches Diodes & capacitive circuits DC Link Micro controller based pulse signal 19. 9 switches. Converts unstable AC to stable AC voltage. Switching loss is reduced Circulating current is minimized. Overall efficiency is improved. 20. MATLAB- Simulink SOFTWARE REQUIREMENTS Microcontroller( AVR) Inductor Vienna rectifier Inverter Gate driver 21. Voltage = 12*1.732, Current = 500mA, PF= 0.8 Power = VI = 10.392 watt PF = Active power Apparent power Apparent power = 10.392/0.8 = 12.99VA Watt at 0.8 PF = 10.392 Watt Watt at 0.9 PF = 12.99 * 0.9 = 11.691 Watt Increased power is 11.691- 10.392 = 1.299 Watt 22. % of Efficiency = Output * 100 Input Output = 11.691 Watt Input = 12.99 VA = 11.691 * 100 12.99 = 90% 23. VAR = P( tan1 tan2) Cos1 = 0.8 lag Cos2 = 0.9 lag 1 = 0.64 2 = 0.45 P = Output / VAR = 12.98( tan 0.64 tan 0.45) Reactive power = 3.374VAR Ratings in each = 3.374 / 3 = 1.12 VAR 24. ADVANTAGES APPLICATIONS Vienna rectifier Maintains stable voltage on DC side & maintains pure sine wave form. USMC Converts unstable AC to stable AC with minimum number of switches. AC drives Steel Plant Solar power systems Telecommunications 25. This paper has comprehensively addressed the mimization of circulating current and switching losses. In this method the unstable AC voltage is converted to a stable AC voltage with power factor improvement. Experimental verification of the power converters confirms the good performance and promising features of the proposed directly driven permanent magnet wind power generation system. 26. P.Goel,B.Singh,S.S.Muruthy,& N.Kishore,Isolated wind - hydro hybrid system using cage generators & battery storage,IEEE Trans.Ind.Electron., to appear. M.Liserre,R.Cardenas,M.Molinas,&J.Rodriguez,Overview of multi-MW wind turbines & wind parks,IEEE Trans.Ind.Electron.,vol.58,no.4,pp.1081-1095,Apr.2012. A.Rajaei,M.Mohamadian,S.M.Dehghan,&A.Yazdian,PMSG- based variable speed wind energy conversion system using rectifier,Euro. Trans.Electr.Power,vol,21,Jan 2012