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- 1. IV th International Conference on Advances in Energy Research Indian Institute of Technology Bombay, Mumbai Islanding Operation of DFIG for Rural Electrification Using Back to Back Converter Presented By Paper ID-236 M.Tech Scholar Rakhi Soni Co-authors- Monika Jain & Sachin Tiwari OIST Bhopal (MP)
- 2. Contents Introduction Distributed generation Technologies of DG Advantages of DG Types of generator DFIG (Doubly Fed Induction Generator) Control schemes of DFIG Results & discussion conclusion References
- 3. INTRODUCTION Wind turbines convert the kinetic energy present in the wind into mechanical energy by means of producing torque. They are operated either at fixed speed or variable speed. Generators driven by fixed speed turbines can directly be connected to grid. Variable speed generators need a power electronic converter interface for interconnection with the grid. Variable generation. speed generation is preferred over fixed speed
- 4. Types Of AC. Generators AC GENERATOR ASYNCHRONOS GENERATOR SEIG DFIG SYNCHRONOS GENERATOR
- 5. DFIG (Doubly Fed Induction Generator) Wound rotor induction generator with slip rings. Rotor is fed from a three-phase variable frequency source, thus allowing variable speed operation reduction of mechanical stress; higher overall efficiency, reduced acoustical noise. The variable frequency supply to rotor is attained through the use of two voltage-source converters linked via BESS.
- 6. Advantage of DFIG The variable speed machines have several advantages :- They reduce mechanical stresses. Reduced convertor losses. improve power quality & system efficiency.
- 7. Control schemes of DFIG DFIG iLi(a) ist(a) Pm Pm a iLi(b) ist(b) b Vp(ab) Vp(ca) ist(c) Vp(bc) iLi(c) c iro(a) iro(c) iro(b) RC Filter Rbat Cdc Cbat ica Rin icb Vdc Voc Rotor side converter Battery icc Inductive Filter ibat Stator side converter icn Zig- Zag Transformer balanced/ unbalance d, resistive and reactive load
- 8. Principle of Operation The rotor currents and stator currents of the DFIG are controlled by stator-flux oriented control to decouple the active and reactive components of these currents and to achieve fast dynamic response. Torque Control- The electrical torque of the DFIG can be controlled to operate the wind turbine at the point of maximum aerodynamic efficiency by controlling the active power current component of the rotor. Max. Power Point Control- To operate at maximum coefficient of performance for optimizing energy capture from the wind, the turbine should run at optimal tip speed ratio.
- 9. Continue….. Voltage control- the voltage control at the stator terminals is achieved by controlling the reactive component of the stator current. Frequency control- the stator frequency control is achieved by generating stator flux angle by integrating the reference stator frequency and using that angle for transformation of reference d-q stator quantities to reference three phase quantities.
- 10. Wind Turbine The aerodynamic power generated by wind turbine can be expressed as by, P=0.5ρACpV3ω Where the aerodynamic power is expressed as a function of the specific density (ρ) of the air, the swept area of the blade ( A), and the wind speed (V3ω)
- 11. Stator side converter Stator current measurem -ent Vter * DFIG ist(a) Cdc ist(b) * Iqro * i st(a) * Iqst PI Controller Idst * i st(b) Ɵ st flux -Lm/Lst * 2Πf t dq/ abc * i st(c) Battery ist(c) Vter Voc Rbat ibat Rin Cbat Hysteresis controller Hysteresis modulating signals Inductive filter Zig- zag transformer n Connected to load Connected to stator c b a
- 12. Cntd… The terminal sensed voltage (Vter) is calculated by, Vter={(Vab2+Vbc2+Vca2)/3}1/2 Vter* which is taken as 415V. Vterr(n) = Vter* -Vter Vterr is fed to PI voltage controller with gains Kpv and Kiv. 12
- 13. Cntd… The magnetizing current requirement of the DFIG is provided by the rotor side converter. Any additional reactive power for the electrical loads and stator leakage reactance is supplied from the stator side converter. 13
- 14. Cntd… The stator frequency control is achieved by өstatorflux=2πfnTsamp 14
- 15. Cntd… 15
- 16. Rotor side converter Vter Stator voltage measurem -ent DFIG Iro(b) Iro(a) Iro(c) imsaturated Idro* ωter * ωter * i PI Controller Iqro* Ɵ slip dq/ abc ro(a) Hysteresis modulating signals * i ro(b) * i ro(c) Hysteresis controller Voc Iro(a) Iro(b) Iro(c) Cdc Rbat ibat Battery Ɵ st flux (p/2) Ɵ ro Rotor current measurent Cbat Inductive filter Zig- zag transformer n Connected to load Connected to stator c b a
- 17. Cntd… The reference for the d component of the rotor current (Idro*) is taken as the rated magnetizing current (lmsaturated), Imsaturated = √2 Vter* / √3 Xm Where, Vter* is 415V, Xm is the magnetizing reactance of the DFIG. 17
- 18. Cntd… 18
- 19. Cntd… For dq to abc transformation, the angle between d-axis and rotor axis (ϴSlip) is required. ϴSlip can be generated as, ϴslip = ϴstatorflux - ( p/2 )ϴro 19
- 20. Cntd… 20
- 21. Battery Specifications The terminal voltage of the equivalent battery Vbat is given by, Vbat= (2√2/√3) V Where VLi is the line rms. voltage (V = 415V). A slightly higher round-off value of 750 V is considered. the equivalent capacitance can be given by, Cbat = (kwh * 3600 * 103) / 0.5 (V2ocmax – V2ocmin) Cbat = (7.5*10*3600*103) / 0.5 [(7602) – (7402)] Cbat = 18000 F
- 22. Ratings…… A. Machine parameters: 7.5 kW, 415V, 50Hz, Y -connected, 4-pole, Rs = 1Ω, Rr=0.77Ω, Xlr= Xls= 1.5Ω, J= 0.1384kg-m2 B. Wind turbine parameters: Wind rating= 15 kW, Wind Speed Range = 9 -11 m/sec, Inertia = 3 .5 kg_m2, r = 3.55 m, gear ratio= 7.516. C. Controller parameters: Kpf= 10, Kif = 50, Kpd = 0.02, Kid = 0.0025.
- 23. Ratings…… D. Battery parameters: Lf = 3mH, Rf = 0.1Ω and Cdc = 4000µf, R1=10K, Ro=0.01 Ω, Cbat=36000 F E. Zigzag Transformer specification: Three phase zigzag transformer, 50 Hz, 150 V/ 415 V, kVA rating =10 kVA. F. Consumer Loads: Resistive load= 2.5 kW single phase loads. Reactive load = 2.5kW, 1.875 KVAR 0.8PF lagging single Phase loads.
- 24. Performance of DFIG with BESS Feeding Balance / Unbalanced Resistive Load Icabc1 Stator V abc Stator voltage Controller current 1 500 20 00 -20 -500 2.1 2.1 2.2 2.3 2.4 2.5 2.15 2.2 2.25 2.1 2.15 2.2 2.25 -20 2.1 2.15 2.2 2.25 2.15 2.2 2.25 2.6 2.35 2.4 2.9 2.45 2.3 Load netural current 2.35 2.4 2.45 2.5 2.3 2.35 2.4 2.45 2.5 2.3 2.35 2.4 2.45 2.5 2.3 Stator current 2.7 2.8 3 2.5 0 i abc 20 -20 0 I Ln 20 I L abc 20 Load current 0 -20 2.1
- 25. Cntd… Frequency (Hz) 55 f 50 45 2.1 2.15 2.2 2.25 2.4 2.45 2.5 2.7 2.4 2.8 2.9 2.45 3 2.5 2.7 2.8 2.9 3 te r Wind I bat 1 Vt3 Vt2 V f 2 f 3 2.35 Terminal (Hz) 3 Frequency voltage 2 600 55 50550 45500 2.12.1 2.3 2.2 2.15 2.3 2.2 2.4 2.25 2.3 2.6 2.35 Battery Current 10 600 0 550 -10 500 12 2.1 2.5 Terminal voltage 2 3 2.2 2.3 2.4 2.5 Wind 2.6 10 8 2.1 2.15 2.2 2.25 2.3 Time 2.35 2.4 2.45 2.5
- 26. Performance of DFIG with BESS Feeding Balance/ Unbalanced Reactive Load Icabc1 Stator V abc Stator voltage 500 200 0 -20 -500 2.1 2.1 Controller current 1 2.22.15 2.3 2.2 2.4 2.1 2.15 2.2 2.25 -20 2.1 2.15 2.2 2.25 2.25 2.5 2.35 2.7 2.4 2.8 2.9 2.45 3 2.5 2.3 2.35 2.4 2.45 2.5 2.3 2.35 2.4 2.45 2.5 2.35 2.4 2.45 2.5 2.3 2.6 Stator current 0 i abc 20 -20 Load netural current 0 I Ln 20 Load current I L abc 20 0 -20 2.1 2.15 2.2 2.25 2.3
- 27. Cntd… Frequency (Hz) f 55 50 45 2.1 2.15 2.2 2.25 2.3 Terminal voltage Frequency (Hz) 32 2.35 2.25 2.5 2.3 2.6 Battery Current Terminal voltage 2 3 2.35 2.45 2.5 2.45 2.9 32.5 2.9 3 3 f V te r f 2 600 2.4 55 50 500 452.1 2.1 IVt3 1 Vt2 bat 55 550 2.3 2.2 2.2 2.3 2.4 10 600 5500 500 -10 2.1 12 Wind 2.22.15 2.4 2.5 Wind 2.6 2.7 2.4 2.7 2.8 2.8 10 8 2.1 2.15 2.2 2.25 2.3 Time 2.35 2.4 2.45 2.5
- 28. Conclusion There are many isolated locations which cannot be connected to the grid and where the wind potential exists, for such locations wind system are beneficial. The performance of proposed controller demonstrated under balanced/unbalanced linear loads. The simulated results verify the effectiveness of the controller under various consumer loads. It has been observed that the proposed controller has been found to regulate the magnitude and frequency of isolated system. It has also been found that controller is capable to function as load balancer, load leveler and harmonic eliminator as well as the capability of MPT. Zigzag transformer is used for harmonics eliminator having voltage boost capability. The implementation of this technology reinforces the use of such system in remotely located villages by locally available energy sources.
- 29. References [1] Peña, R., Clare J. C., and Asher G. M. (May 1996) “Doubly Fed Induction Generator using back to-back PWM converters and its application to variable speed wind-energy generation,” Proc. Inst. Elect. Eng., Elect. Power Appl., vol.143, no. 3, pp. 231–24. [2] Murthy S. S., (2007) “A Comparative Study of Fixed Speed and Variable Speed Wind Energy Conversion Systems Feeding the Grid,”IEEE conference. [3] Singh Bhim, (2010) “Performance of wind energy conversion system using a doubly fed induction generator for maximum power point tracking” IEEE conference. [4] Blaabjerg, F., Chen, Z. and Kjer S.B. (2010) “Power electronics as efficient interface of renewable source”, IPEMC conference. [5] K. Goel Puneet, “Modeling and Control of Autonomous Wind Energy Conversion System with Doubly Fed Induction Generator,”IEEE Conference. [6] K. Goel Puneet, Singh Bhim, (April 2011) “Isolated Wind–Hydro Hybrid System Using Cage Generators and Battery Storage,” IEEE Transactions On Industrial Electronics, vol. 58, no. 4, pp. 1141-1152.
- 30. Continued…… [7] Mullane A. Lei Y, Lightbody G., and Yacamini R. (Mar. 2006) “Modeling of the wind turbine with a doubly-fed induction generator for grid integration studies,” IEEE Trans. Energy Conversion, vol. 21, no. 1, pp. 257-264. [8] Kasal Gaurav Kumar, (June 2008) “Voltage and frequency controller for a Three-phase Four wire Autonomous wind energy conversion system,” IEEE Transactions on Energy Conversion, vol. 23, no. 2, pp. 509- 516. [9] Singh Bhim, (2010) “Performance of Wind Energy Conversion System using a Doubly Fed Induction Generator for Maximum Power Point Tracking” IEEE conference. [10] Verma Vishal, (2011) “Decoupled Indirect Current Control of DFIG for Wind Energy Applications,” IEEE Conference. [11] K. Goel Puneet, (July/August 2011 ) “ Parallel Operation of DFIGs in Three-Phase Four-Wire Autonomous Wind Energy Conversion System,” IEEE Transactions on Industry Applications, vol. 47, no. 4,1872-1883. [12] Marek Adamowicz* and Ryszard Strzelecki, (2008) “Cascaded Doubly Fed Induction Generator for Mini and Micro Power Plants Connected to Grid,” IEEE conference.
- 31. Continued…… [13] Ganti Vijay chand, (2010) “Quantitative Analysis and Rating Considerations of a Doubly Fed Induction Generator for Wind Energy Conversion Systems,” IEEE conference. [14] Kasal Gaurav Kumar, (2008) “Voltage and frequency control with Neutral current compensation in an Isolated Wind Energy Conversion System,” IEEE conference. [15] Muller S., Deicke M. and De Doncker R. W. (May/Jun. 2002) “Doubly fed induction generator systems for wind turbines,” IEEE Ind. Appl. Mag., vol. 8, no. 3, pp. 26–33. [16] Petersson A. Harnefors, L. and Thiringer T. (Jan. 2005) “Evaluation of current control methods for wind turbine using doubly-fed induction machine,” IEEE Trans. Power Electron., vol. 20, no. 1, pp. 227–235. [16] Slootweg, J. G., Haan, H. W. S., Polinder, H. and Kling, L. W. (Feb. 2003 ) “General model for representing variable speed wind turbines in power system dynamics simulations,” IEEE Trans. Power Syst., vol. 18, no. 1, pp. 144– 151. [17] Simoes M.G. and Farret F. A., (2004) “Renewable Energy Systems: Design and Analysis With Induction Generators”. Orlando, FL: Fl-CRC. [18] Blaabjerg F., Chen Z., Teodorescu R. & Lov F., (2006) “Power electronics in wind turbine systems,” IEEE Int. Conf. on Power Electronics and Motion Control, pp. 1-11.
- 32. SAVE ENERGY SAVE FUTURE THANKS 32

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