1. Control of Three-phase Active Rectifier for Wind Turbine Applications AALBORG UNIVERSITY INSTITUTE OF ENERGY TECHNOLOGY UNIVERSITY OF MARIBOR INSTITUTE OF ROBOTICS Evgen Urlep December, 2002

2. Contents Introduction System modeling and analysis LCL filter design Control design Simulation and implementation Conclusion

3. Introduction Types of Wind Turbines Horizontal axis Vertical axis Operation modes of WTG Constant Speed – Constant Frequency Variable Speed – Constant Frequency

4. Problem definition Nominal power11kW Nominal grid current16A Grid side phase voltage (rms) 230V Grid frequency50Hz DC link voltage700V DC link nominal current17A Rated values Grid connection Grid connection Stand-alone Stand-alone Design and implementation of the control scheme for the DC/AC converter in WTG in

5. Hardware configuration

6. System overview

7. Three-phase Active rectifier RL-filter

8. RL filter in rotating frame

9. Grid mode controller design

10. Active Rectifier control structure Grid connected

11. Model of the LCL filter

12. LCL filter design L I [mH]1.25 L G [mH]1.5 C F [  F] 6 RD []RD [] 4 Q c <5% Z T <10%Z b  res <0.5  sw

13. Current attenuation

14. Current controller design

15. Root locus Kp=4.8Ti=8 ms

16. DC-link controller design k DC =0.7, T et =4.8ms C DC >>(T ei +  0 ), optimal symmetry criterion

17. Root locus Kp=0.35Ti=20 ms

18. Standalone control structureStand-alone

19. Main voltage controller design

20. Root locus Kp=0.1Ti=0.29 ms 1% load nominal load

21. DC-link voltage limiter T et =2.1ms,  0 =0.2ms C DC >>(T ei +  0 ), optimal symmetry criterion

22. Root-locus Kp=0.79Ti=0.092 ms

23. DC-link choper operation R DC

24. Phase angle detection Kp=80Ti=1 s

25. Simulation in grid mode

26. Steady state simulation Grid mode Generating mode Ideal phase voltage 2% 5 th + 1% 7 th harmonics

27. Simulation in stand-alone mode

28. Steady state simulation phase voltages and current at nominal power using resistive load Stand-alone mode

29. Transient simulation Stand-alone mode System startup Half of nominal load to nominal load

30. Implementation dSPACE 1103 MPPC 604e at 633Mhz MPPC 604e at 633Mhz TMS320F240 TMS320F240 16xADC-16 4  s ±10V 16xADC-16 4  s ±10V 4xADC-12 800 ns  10V 4xADC-12 800 ns  10V 8xDAC-14 bit -6 µs  10 8xDAC-14 bit -6 µs  10 7x IE interface 7x IE interface 32xI/0 32xI/0 TDE software TDE software

31. Combined control

32. ControlDesk

33. Steady state operation Grid mode Measured conditions U DC =650VU AC =220V P=11.28kWPF=0.998 I THD =6.7%U THD =2% Rectifying mode Generating mode

34. Transient operation Grid mode Nominal load system startup Disturbance rejection

35. Steady state operation Stand-alone mode Resistive load Measured conditions U DC =700 VU AC =230 V P=11 kWI AC =16.4 A I THD =3.4 %U THD =3.4 %

36. Steady state operation Stand-alone mode 3-phase diode bridge Measured conditions U DC =700 VU AC =230 V P=11 kWI AC =16.6 A I THD =25 %U THD =10 %

37. Transient operation Stand-alone mode Full load applied on the half of produced power

38. Transient operation Stand-alone mode Short-circuit startup

39. Automatic mode switch Idle mode Grid mode Stand-alone mode I-SA I-GM GM-ISA-I GM-SA I-GM:U G and /PLLe and /TRIP and START I-SA:/U G and /TRIP and START GM-I: TRIP or STOP SA-I: TRIP or STOP or PLLe GM-SA: PLLe

40. Grid mode to Stand-alone mode transition nominal load

41. Stand-alone mode to Grid mode transition

42. Conclusion Vector based control of DC/AC converter with near unity power factor was succesfully designed, simulated, implemented and verified. LCL filter was designed, implemented and tested Two different control strategies were implemented according to the operating modes A common controller design procedure is used to tune controller parameters PLL is designed to detect phase angle Two different control strategies are implemented and tested in dSPACE. Automatic mode detection and switching betwen modes can be implemented