Dynamic response of grid connected wind turbine with dfig

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Dynamic response of grid connected wind turbine with dfig

  1. 1. Chalmers University of Technology Dynamic Response of gridConnected Wind Turbine with DFIG during Disturbances Abram Perdana, Ola Carlson Jonas Persson Dept. of Electric Power Engineering Dept. of Electrical Engineering Chalmers University of Technology Royal Institute of Technology
  2. 2. Chalmers University of TechnologyContents of Presentation1. Background & objectives2. Model of WT with DFIG3. Simulation a. Fault and no protection action b. Fault in super-synchronous operation + protection action c. Fault in sub-synchronous operation + protection action4. Effect of saturation5. Conclusions
  3. 3. Chalmers University of Technology ObjectivesBackground Presentation of DFIG’sDFIG accounts for 50% of behavior during gridmarket share disturbances in different casesTightened grid connectionrequirements  immunity ofDFIG to external faults isbecoming an issue Possibilities and constraints for designing fault ride through strategy  safe for both WT and the grid
  4. 4. Chalmers University of Technology Model Structure ωg igenvwind Tm Induction Drive-train The grid generator model u gen model model Te ωtTurbine ur model fault Pitch uinf Rotor-side signal controller converter β model
  5. 5. Chalmers University of TechnologyGenerator Model Rotor Side Converter ControllerWound rotor induction generatoru s = rs ⋅ i s + ( ) d ψs + jωaψ s Active power controller dt ( ) Pref Pref Teref Teref ⋅ Ls − irqref ωr u s ⋅ Lm d ψr + j (ωa − ωr ) ⋅ψ r ωru r = rr ⋅ i r + dt us Saturation 1,5 Reactive power controller 1 u sref Qsref irdref - - 0,5 + + 0 us Qs 0 1 2 3 4 Current (pu)
  6. 6. Chalmers University of TechnologyTurbine Model pitch angle tip-speed ratioPitch Controller β* 1 ωt s β max=90 max=90 rate limit min=0 min=0 7 deg/sec ωt *
  7. 7. Chalmers University of TechnologyDrive-train Model dωg 2H g = Tg + K s ⋅θtg + Ds ⋅ (ωt − ωg ) dt Gearbox Damping Generator Stiffness Turbine dωt 2H t = Tt − K s ⋅θtg − Ds ⋅ (ωt − ωg ) dtGrid Model 0.027+j0.164 pu 0.027+j0.164 pu Fault DFIG 100 ms Infinite Pgen = 2 MW (1 pu) Bus Rfault Vinf = 1 0o pu
  8. 8. Chalmers University of TechnologyCase 1: Small disturbance, no protection action 0.027+j0.164 pu 0.027+j0.164 pu Fault DFIG 100 ms Infinite Pgen = 2 MW (1 pu) Bus Rfault Vinf = 1 0o pu Rfault = 0.05 pu Avg. wind speed = 7.5 m/s
  9. 9. Chalmers University of Technology Case 1: Small disturbance, no protection action stator current rotor currentterminal voltage active & turbine & reactive power generator speed
  10. 10. Chalmers University of TechnologyCase 2: Protection action during super-synchronous speed 0.027+j0.164 pu 0.027+j0.164 pu Fault DFIG 100 ms Infinite Pgen = 2 MW (1 pu) Bus Rfault Vinf = 1 0o pu Rfault = 0.01 pu Avg. wind speed = 11 m/s
  11. 11. Chalmers University of Technology Case 2: Protection action during super-synchronous speedSequence: irA. Fault occurs rotor circuitB. If ir > 1.5 pu: converter is blocked & rotor is short-circuitedC. Generator is disconnectedD. Fault is cleared
  12. 12. Chalmers University of TechnologyCase 2: Protection action during super-synchronous speed terminal voltage stator current Insertion of external rotor resistance active power reactive power
  13. 13. Chalmers University of TechnologyCase 2: Protection action during super-synchronous speed no disconnection disconnection + acting of pitch angle generator & turbine speed generator & turbine speed pitch angle
  14. 14. Chalmers University of TechnologyCase 3: Protection action during sub-synchronous speed 0.027+j0.164 pu 0.027+j0.164 pu Fault DFIG 100 ms Infinite Pgen = 2 MW (1 pu) Bus Rfault Vinf = 1 0o pu Rfault = 0.01 pu Avg. wind speed = 9 m/s
  15. 15. Chalmers University of TechnologyCase 3: Protection action during sub-synchronous speed terminal voltage stator current turbine & generator speed active power reactive power
  16. 16. Chalmers University of Technology 1,5 saturationEffect of Saturation 1 curvein the Model 0,5 0 0 1 2 3 4 Current (pu) stator current rotor current
  17. 17. Chalmers University of Technology Conclusions• DFIG provides a better terminal voltage recovery compared to SCIG during (small) disturbance when no converter blocking occurs,• for severe voltage dips DFIG will be disconnected from the grid (with conventional strategy) – converter blocking during super-synchronous operation causes high reactive power consumption, – converter blocking during sub-synchronous operation causes high reactive and active power absorption and abrupt change of rotor speed• Saturation model predicts higher value of stator & rotor currents, therefore it is important to include in designing protection

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