POWER FACTOR CONTROL OF A CYCLO-CONVERTER

• US 20130201738A1
• Filed: 06/15/2011
• Published: 08/08/2013
• Est. Priority Date: 06/29/2010
• Status: Active Grant

• Current Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Original Assignee: Eaton Industries Limited (Eaton Corporation PLC.)
• Inventors: Harrison, Michael John, Lee, Kevin, Familiant, Yakov
• Granted Patent: US 9,143,031 B2
• Time in Patent Office: Days
• US Class Current: 363/84
• CPC Class Codes: H02M 1/4216 operating from a three-phase input voltage H02M1/4233 takes precedence
• CPC Class Codes: H02M 1/4241 using a resonant converter
• CPC Class Codes: H02M 1/425 using a single converter stage both for correction of AC input power factor and generation of a high frequency AC output voltage
• CPC Class Codes: H02M 1/4258 using a single converter stage both for correction of AC input power factor and generation of a regulated and galvanically isolated DC output voltage H02M1/4241 takes precedence
• CPC Class Codes: H02M 5/271 from a three phase input voltage
• CPC Class Codes: H02M 5/293 using semiconductor devices only
• CPC Class Codes: H02M 7/217 using semiconductor devices only
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A three-phase resonant cyclo-converter comprising a power control module, wherein the power control module is arranged to develop a plurality of repeating switching periods within a cycle, the power control module further arranged to: control the length of a first switching period in the cycle to adjust the power flow, and control the relative length of two or more further switching periods in the cycle to adjust the power factor, wherein the relative length is controlled based on a cross-product of voltage and current values associated with the further switching periods.

Claims

1. A three-phase resonant cyclo-converter comprising a power control module, wherein the power control module is arranged to develop a plurality of repeating switching periods within a cycle, the power control module further arranged to:

control the length of a first switching period in the cycle to adjust the power flow, and control the relative length of two or more further switching periods in the cycle to adjust the power factor, wherein the relative length is controlled based on a cross-product of voltage and current values associated with the further switching periods.

2. The cyclo-converter of claim 1, wherein the power control module comprises a power factor control module, the power factor control module arranged to adjust a ratio of the further switching periods based on a cross product of derived voltage and current waveforms associated with a first and a second of three input phase voltage signals, the power factor control module comprising:

a voltage development module arranged to develop voltage waveforms based on the input phase voltage signals; and

a current synthesizer module arranged to synthesize current waveforms based on a resonant current of the cyclo-converter measured during the switching of the first and second input phase voltage signals.

3. The cyclo-converter of claim 2, wherein the voltage development module is further arranged to develop the voltage waveforms by measuring the input phase voltage signals directly.

4. The cyclo-converter of claim 2, wherein the voltage development module comprises a phase detection module which is arranged to detect a phase difference between the phases of the input phase voltage signals, and the voltage development module is further arranged to develop the voltage waveforms based on the detected phase difference and a trigonometric function.

5. The cyclo-converter of claim 4, wherein the detected phase difference is used to determine a phase angle that identifies the phase position of the input phase voltage signals.

6. The cyclo-converter of claim 2, wherein the first input phase voltage signal is determined by the input phase voltage signal that has the greatest absolute magnitude, and the second input phase voltage signal is determined by the input phase voltage signal that has a medium absolute magnitude.

7. The cyclo-converter of claim 2, wherein the power factor control module is further arranged to adjust the ratio by modifying the first switching signal using an error signal based on the cross product of the derived voltage and current waveforms.

8. The cyclo-converter of claim 2, wherein the first and second switching signals are used to control the switching of two of three of the input phase voltage signals.

9. The cyclo-converter of claim 2, wherein the current synthesizer module is arranged to feed the resonant current into a first and second integrator using first and second drive signals that are based on the switching periods.

10. The cyclo-converter of claim 9, wherein the first drive signal is based on the first switching period and the second drive signal is based on one further switching period.

11. The cyclo-converter of claim 10, wherein the cyclo-converter further comprises an input phase voltage signal monitor module arranged to monitor the input phase voltage signals, wherein the current synthesizer module is further arranged to invert the drive signals when the input phase voltage signals are detected by the input phase voltage signal monitor module as being negative.

12. The cyclo-converter of claim 9, wherein the current synthesizer module comprises a current transformer and burden resistors arranged across the current transformer to detect the resonant current on the output of the cyclo-converter.

13. The cyclo-converter of claim 2, wherein the power factor control module is arranged to detect a magnitude crossing signal or zero crossing signal and further arranged to adjust the ratio of the further switching periods when neither of the magnitude crossing signal and zero crossing signal are detected.

14. The cyclo-converter of claim 2, wherein the power factor control module determines the cross product by multiplying a first derived voltage waveform with a second synthesized current waveform to produce a first output, multiplying a second derived voltage waveform with a first synthesized current waveform to produce a second output, and subtracting the second output from the first output to develop an error term.

15. The cyclo-converter of claim 14, wherein the power factor control module is further arranged to integrate the error term to develop a control parameter that is used to adjust the ratio of the further switching periods.

16. The cyclo-converter of claim 15, wherein the power factor control module is further arranged to apply a feed forward signal to the control parameter to provide an adjusted control parameter.

17. The cyclo-converter of claim 16, wherein the feed forward signal is the magnitude value of a third derived voltage waveform.

18. The cyclo-converter of claim 16, wherein the power factor control module is further arranged to normalise the adjusted control parameter based on the first switching period.

19. The cyclo-converter of claim 1, wherein the cyclo-converter is a half bridge cyclo-converter.

20. The cyclo-converter of claim 1, wherein the cyclo-converter is a full bridge cyclo-converter.

21. A method of developing a plurality of repeating switching periods within a cycle to control a three-phase resonant cyclo-converter, the method comprising the steps of:

controlling the length of a first switching period in the cycle to adjust the power flow, and controlling the relative length of two or more further switching periods in the cycle to adjust the power factor, wherein the relative length is controlled based on a cross-product of voltage and current values associated with the further switching periods.

22. The method of claim 21, further comprising the steps of adjusting a ratio of the further switching periods based on a cross product of derived voltage and current waveforms associated with a first and a second of three input phase voltage signals, developing voltage waveforms based on the input phase voltage signals, and synthesizing current waveforms based on a resonant current of the cyclo-converter measured during the switching of the first and second input phase voltage signals.

23. The method of claim 22, further comprising the step of developing the voltage waveforms by measuring the input phase voltage signals directly.

24. The method of claim 22, further comprising the steps of detecting a phase difference between the phases of the input phase voltage signals, and developing the voltage waveforms based on the detected phase difference and a trigonometric function.

25. The method of claim 24, wherein the detected phase difference is used to determine a phase angle that identifies the phase position of the input phase voltage signals.

26. The method of claim 22, wherein the first input phase voltage signal is determined by the input phase voltage signal that has the greatest absolute magnitude, and the second input phase voltage signal is determined by the input phase voltage signal that has a medium absolute magnitude.

27. The method of claim 22, further comprising the step of adjusting the ratio by modifying the first switching signal using an error signal based on the cross product of the derived voltage and current waveforms.

28. The method of claim 22, wherein the first and second switching signals are used to control the switching of two of three of the input phase voltage signals.

29. The method of claim 22, further comprising the step of integrating the resonant current using first and second drive signals that are based on the switching periods.

30. The method of claim 29, wherein the first drive signal is based on the first switching period and the second drive signal is based on one further switching period.

31. The method of claim 30, further comprising the steps of monitoring the input phase voltage signals and inverting the drive signals when the input phase voltage signals are detected as being negative.

32. The method of claim 29, further comprising the step of detecting the resonant current on the output of the cyclo-converter.

33. The method of claim 22, further comprising the steps of determining whether a magnitude crossing mode or zero crossing mode is active and adjusting the ratio of the further switching periods when neither of the magnitude crossing modes and zero crossing modes are active.

34. The method of claim 22, further comprising the steps of determining the cross product by multiplying a first derived voltage waveform with a second synthesized current waveform to produce a first output, multiplying a second derived voltage waveform with a first synthesized current waveform to produce a second output, and subtracting the second output from the first output to develop an error term.

35. The method of claim 34, further comprising the step of integrating the error term to develop a control parameter that is used to adjust the ratio of the further switching periods.

36. The method of claim 35, further comprising the step of applying a feed forward signal to the control parameter to provide an adjusted control parameter.

37. The method of claim 36, wherein the feed forward signal is the magnitude value of a third derived voltage waveform.

38. The method of claim 36, further comprising the step of normalising the adjusted control parameter based on the first switching period.