Wind Farm Introduction Wind turbine Wind speed Wind turbine Generator DFIG Direct drive

1. Wind Farm • Introduction • Wind turbine • Wind speed • Wind turbine • Generator • DFIG • Direct drive Dr. Dharshana Muthumuni September 2009

2. Main components Introduction

3. Introduction System Turbine Generator Connection

4. Turbine-Wind Speed • Wind speed distribution???? • Short term wind speed variations • Modeling wind speed Turbine aero dynamic model Wind speed model Pitch control

5. Turbine-Wind Speed • PSCAD allows modeling of • mean wind speed • Short term wind: gusts, ramps and noise.

6. Turbine-Wind Speed Gust Noise Ramp

7. Turbine-Wind Speed Modeling Short term wind speed variations • Recorded wind speed data (speed vs time) can be used in a PSCAD simulation

8. Wind Turbine Turbine aero dynamic model Wind speed model Pitch control

9. Wind Turbine • Turbine components • Aerodynamics • Power coefficient • Control options

10. Wind Turbine 风机机械功率 风能效率系数 叶尖速比 桨矩角 β

11. Wind Turbine • Stall (定桨距失速调节型) • Pitch （变桨距调节型） • Active stall control （主动失速调节型） Turbine aero dynamic model Wind speed model Pitch control

13. PSCAD pitch control model

14. Wind Generator 风能效率系数 叶尖速比 • Variable and fixed speed？？ • Induction machines • Doubly fed induction machines • Synchronous and PM machines

15. Wind Generator Direct connected induction machine: network IM Gear box Capacitors or SVC • No slip rings/brushes, • Squirrel cage machine has a simple robust construction • Less maintenance • ‘Fixed speed’ operation

16. Torque Equation in Steady State Wind Generator Torque Speed (pu) • Operating region of the machine falls over a small speed range • No reactive power control

17. Torque Equation in Steady State Wind Generator Rrotor increasing Typical speed variation: +/- 5% Effect of varying rotor resistance in Wound Rotor Machines

18. Wind Generator Direct connected induction machine (variable rotor resistance): • Control rotor resistance with power electronics IM To rotor

19. Wind Generator • Direct connected induction machines: • Poor fault response

20. Wind Generator • Direct connected induction machines: • Poor fault response • Machine must be tripped during faults.

21. Wind Generator Double fed induction machine: DFIG Controls network IM Gear box Current of variable frequency and magnitude are forced into the rotor windings • Wound rotor machine with slip rings • ‘Variable speed’ operation • P and Q independent control

22. Wind Generator Double fed induction machine:

23. Wind Generator Double fed induction machine: • Fast control of P and Q • ‘Variable speed’ operation – Optimal power tracking at low wind speeds • Store kinetic energy in the rotating system during high winds • Machine and mechanical system ratings limit operating region. • Rotor crow bar protection during faults • Over speed limits

24. Wind Generator Synchronous machine connected through a ac-dc-ac converter: network SM Gear box • With or without gear box • Can allow variable speed operation • Permanent magnet machine are used as well