1. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 1 Power Converter Systems Graduate Course EE8407 Ryerson Campus Bin Wu PhD, PEng Professor ELCE Department Ryerson University Contact Info Office:ENG328 Tel: (416) 979-5000 ext: 6484 Email:bwu@ee.ryerson.ca http://www.ee.ryerson.ca/~bwu/

2. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 2 PWM CSI fed MV drive Topic 9 PWM Current Source Inverters (CSI) Courtesy of Rockwell Automation

3. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 3 Lecture Topics Single Bridge Inverter Trapezoidal Modulation (TPWM) Selective Harmonic Elimination (SHE) Space Vector Modulation (SVM) Dual Bridge Inverter PWM Current Source Inverters

4. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 4 Inverter Topology Features: - Simple topology – no antiparallel diodes - Reliable short circuit protection – constant dc current - Very low dv/dt on motor terminals Symmetrical GCTs Function of C f : - Assist GCT commutation - Reduce harmonic distortion Single Bridge Inverter

5. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 5 DC Current Source I d Implementation of dc current source: - use a large size dc choke – making I d smooth; - use dc current feed back control – keeping I d constant Single Bridge Inverter

6. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 6 Trapezoidal PWM (TPWM) Selective Harmonic Elimination (SHE) Space Vector Modulation (SVM) Constraints on Switching Pattern Design - dc current I d cannot be interrupted - inverter output current waveform must be defined. At any time instant, only two switches are turned on, one connected to the positive dc bus, and the other to the negative dc bus. Modulation Techniques Single Bridge Inverter

7. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 7 Trapezoidal PWM (TPWM) Number of pulses per half cycle: N p = 7 Trapezoidal Modulation

8. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 8 Harmonic Content (TPWM) N p = 15 Fundamental does not change much with m a m a = 0.85 Trapezoidal Modulation

9. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 9 Waveforms (TPWM) Trapezoidal Modulation

10. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 10 Principle Not all the switching angles are independent. Only two harmonics can be eliminated with N p = 5. No modulation index control – the magnitude of inverter output current is controlled by I d Number of harmonics to be eliminated: Selective Harmonic Elimination (SHE)

11. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 11 Fourier Analysis Selective Harmonic Elimination

12. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 12 Expression for a n Fourier Analysis Selective Harmonic Elimination

13. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 13 Switching Angle Calculation To Eliminate n th harmonic, set a n = 0 For 5 th, 7 th and 11 th harmonic elimination: Selective Harmonic Elimination

14. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 14 Switching Angles (SHE) Selective Harmonic Elimination

15. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 15 Inverter Waveforms (SHE) Harmonic eliminated: 5 th, 7 th and 11 th ; f sw = 420Hz Selective Harmonic Elimination

16. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 16 Waveforms (SHE) Selective Harmonic Elimination

17. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 17 Space Vector Modulation Six active current vectors and one zero vector Six sectors Space Vector Modulation

18. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 18 Switching State Space Vector Modulation

19. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 19 Switching States & Space Vectors [1]: Upper switch on [-1]: Lower switch on [0]: None of the switches in a leg turned on [2]: Both switches in a leg turned on (bypass mode) Space Vector Modulation

20. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 20 Dwell Time Calculation Following the same principle of SVM for the NPC inverter Space Vector Modulation

21. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 21 Dwell Time Calculation  Space Vector Modulation

22. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 22 Switching Sequence Requirements: 1)Transition from one switching state to the next involves only two switches 2) At any time only two switches are on. Space Vector Modulation

23. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 23 Switching Sequence (Over one cycle) Space Vector Modulation

24. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 24 Inverter Output Waveforms (SVM) f 1 = 60Hz, f sw = 540Hz, N p = 9 and m a = 1 Space Vector Modulation

25. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 25 Harmonic Spectrum (SVM) f 1 = 60Hz, f sw = 540Hz, N p = 9 and m a = 1 Space Vector Modulation

26. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 26 Harmonic Content (SVM) Space Vector Modulation

27. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 27 Converter Configuration Dual-Bridge Inverter

28. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 28 Space Vector Diagram 19 vectors and 51 switching states Dual-Bridge Inverter

29. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 29 Current paths with switching state [16;56] DC Current Balance Control Dual-Bridge Inverter

30. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 30 DC Current Balance Control Current paths with switching state [16;56] Dual-Bridge Inverter

31. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 31 Space Vector Diagram Dual-Bridge Inverter

32. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 32 PWM Scheme Comparison Summary

33. EE8407 Topic 9 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006 33