Power Converter Systems Graduate Course EE8407

1. Power Converter Systems Graduate Course EE8407 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/ Ryerson Campus

2. Topic 10 PWM Current Source Rectifiers (CSR) Courtesy of Rockwell Automation PWM CSI fed MV drive

3. PWM Current Source Inverters • Lecture Topics • Single Bridge Rectifier • Dual Bridge Rectifier • Power Factor Control • LC Resonance and Active Damping

4. Single Bridge Rectifier • Converter Configuration • Switching devices: • Symmetrical GCT • Function of Cf : • To assist GCT commutation; • To reduce line current THD.

5. Single Bridge Rectifier • Rectifier Input Current Waveform • Constraints for Switching Pattern Design • - dc current id should not be interrupted • - waveform of iw should be defined • Three independent angles to eliminate two harmonics • and make modulation index adjustable.

6. Single Bridge Rectifier • Switching Angles • Bypass pulse (BP) - make iw adjustable

7. Single Bridge Rectifier • Switching Angles versus ma (5th and 7th harmonic elimination)

8. Single Bridge Rectifier • Harmonic Profile (5th and 7th harmonic elimination)

9. Single Bridge Rectifier • Waveforms (5th and 7th harmonic elimination)

10. Single Bridge Rectifier • Experiments ma= 0.7 ma= 0.95 Trace A: current in switch S1Trace B: Rectifier input current iw Trace C: Line current is

11. Single Bridge Rectifier • Dual-Bridge Topology • Use 12-pulse transformer to cancel the 5th and 7th harmonics • Use PWM to eliminate the 11th and 13th harmonics • The lowest harmonic in the line current is the 17th • Very low line current harmonic distortion

12. Single Bridge Rectifier • Switching Angles BP BP • Bypass pulses (BP) – make iw adjustable • SHE modulation – eliminate the 11th and 13th harmonics

13. Dual Bridge Rectifier • Switching Angles versus md Switching pattern A Switching pattern B (11th and 13th harmonic elimination)

14. Dual Bridge Rectifier • Harmonic Profile (11th and 13th harmonic elimination)

15. Dual Bridge Rectifier • Experimental Waveforms Modulation index: 0.5 Modulation index: 0.9 Trace A: iA - line current on transformer primary side Trace B: is - line current on transformer secondary side Trace C: iw- rectifier input current

16. Power Factor Control • Phasor Diagram • Cf produces leading PF • Delay angle control • produces lagging PF • To improve PF, use ma • and delay angle control • simultaneously

17. Power Factor Control • Block Diagram

18. Power Factor Control • Power Factor Profile

19. Power Factor Control • Experiments (a) Transient response (b) Steady state waveforms (PF = 1)

20. LC Resonances and Active Damping • LC Resonance Resonance may be excited by - Supply voltage harmonics - Rectifier current harmonics Resonant Mode:

21. LC Resonances and Active Damping • Passive and Active Damping • Passive damping: • Rp– physical damping resistor • Active damping: • - no physical resistor • - damping current ip is produced • by CSR via ma control • - ipis in phase with vc

22. LC Resonances and Active Damping • Block Diagram of Active Damping Control

23. LC Resonances and Active Damping • Simulated Waveforms

24. LC Resonances and Active Damping • Measured Waveforms Without Active Damping - Rectifier input current - Line current - Capacitor voltage With Active Damping - Rectifier input current - Line current - Capacitor voltage

25. LC Resonances and Active Damping • Steady-State Waveforms Without Active Damping No active damping control LC resonance tuned exactly to the 5th harmonic (worst case)

26. LC Resonances and Active Damping • Line Current THD No active damping control

27. LC Resonances and Active Damping • Steady-State Waveforms With Active Damping With active damping control LC resonance tuned exactly to the 5th harmonic (worst case)

28. LC Resonances and Active Damping • Line Current THD With active damping control

29. Thanks