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  1. 1. Sensor-less Motor Starting of Grid Connected Small Wind Turbine Mohamed Aner Ahmed Ali Edwin Nowicki David Wood International Conference on Recent Advances in Energy and Power Systems, RAEPS 2012
  2. 2. 1. Introduction 2. Proposed System 3. Wind Turbine Description 4. Proposed Control Technique. 5. Backward operation of VSMC 6. Simulation 7. Conclusion Outline:Outline:
  3. 3. 1.1. IntroductionIntroduction • Small wind turbine takes longer time for starting due to the lake of pitch adjustment. • When the turbine starts under the aerodynamic torque, it takes turbine takes 13 sec to reach it optimal tip speed ration at rated wind speed while at cut-in wind speed it take around 45 sec. for 5kW wind turbine. • Due to the intermittence of the wind, the wind turbine system needs to increase the conversion efficiency to extract the max. possible energy. • If the turbine can reach faster to its optimal speed, the turbine can extract more energy especially at higher power rating. • small wind turbines are being grid connected which can use grid power for rapid acceleration in order to reach to the optimal tip speed ratio fast.
  4. 4. Starting of 5 kW wind turbineStarting of 5 kW wind turbine
  5. 5. 2.2. Proposed SystemProposed System
  6. 6. 3.3. Wind Turbine DescriptionWind Turbine Description 6 5 4 3 2 6 5 4 3 2 1 0 3 0.5 = = = + + + + + + m P p T T P AC U C C C a a a a a a a ρ λ λ λ λ λ λ λ 4.4. Proposed Control TechniqueProposed Control Technique • According to the dynamic equation of the turbine rotor , the rotor can be accelerated if the generator is operated as a motor. • The turbine rotor can operate near its optimal tip speed ratio if the generator torque matches the aerodynamic torque a gT T J d dt B− = Ω + Ω
  7. 7. 4.1 Motoring Mode4.1 Motoring Mode • When wind turbine starts, the turbine speed has to be increased to establish operation at maximum power coefficient , The turbine speed can be quickly increased, if the aerodynamic torque is assisted by operating the generator as a motor using grid power and the bidirectional power flow feature of the VSMC. • In order to reach the maximum acceleration, the generator torque is set to its rated value by injecting the rated quadrature current component to the generator in the positive direction according. 1.5 ( )= −e m qT P Iλ
  8. 8. 4.2 MPPT Mode4.2 MPPT Mode • When the turbine reaches to 60% of optimal tip speed ratio λopt, the MPPT control takes over to maintain operating around λopt. = Ω mvir mvir P T max 3 0.5=mvir P virP AC Uρ vir opt RU λ Ω= • Rotor speed can be estimated from the space vector angle of the generator voltage ( )2 /3 2 /32 3 − ∠Θ = + +J J a b cSV V V e V eπ π
  9. 9. 5.5. Backward operation of VSMCBackward operation of VSMC  VSMC Control:VSMC Control:  Rectifier stage control aspects:Rectifier stage control aspects:  Switching frequency Fs should be higher than Fo and Fi.  Only two switches should be turned on at the same time “one from upper and the other from lower switches” to insure current continuity.  The rectifier should be switched at zero current.  The switching should provide a max DC link voltage.  The switching should provide a unity input displacement power factor “DPF”.
  10. 10. Control Technique LayoutControl Technique Layout
  11. 11. Modulation of Input PhasesModulation of Input Phases ( )ic ic md md θ θ π β α sin 3 sin =       −=
  12. 12. ( ) )(1 sin 3 sin βα β α θ θπ ddd md md o +−= =       −= Inverter stage controlInverter stage control
  13. 13. 6. Simulation results Starting at 10 m/s
  14. 14. Starting at 4 m/s
  15. 15. Starting time Versus Wind Speed
  16. 16. Energy Gain due to Motor Starting
  17. 17. 17 7. Conclusion7. Conclusion • The proposed control technique allows faster starting. • The proposed motor starting control technique produce more energy than aerodynamic starting • The proposed Control technique has significant increase in conversion efficiency • The proposed starting technique can start the turbine at any wind speed even below the cut-in wind speed.