Systems and Methods for Uninterruptible Power Supply Control

• US 20090201703A1
• Filed: 02/07/2008
• Published: 08/13/2009
• Est. Priority Date: 02/07/2008
• Status: Active Grant

• Current Assignee: American Power Conversion Corporation (Schneider Electric SE)
• Original Assignee: American Power Conversion Corporation (Schneider Electric SE)
• Inventors: Prasad, Pyboyina Msvvsv, Klikic, Damir, Ghosh, Rajesh, Agrawal, Mahima
• Granted Patent: US 8,116,105 B2
• Time in Patent Office: Days
• US Class Current: 363/41
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: H02M 1/0012 Control circuits using digital or numerical techniques in DC/DC converters H02M3/157, H02M3/33515; in DC-AC converters H02M7/53873
• CPC Class Codes: H02M 7/538 in a push-pull configuration H02M7/5375 takes precedence ; with oscillating arrangements H02M7/53832, H02M7/53846

Abstract

Systems and methods are provided for distributing power to a load by controlling an uninterruptible power supply that has an inverter and a filter, where the filter has an inductor and a capacitor. The systems and methods apply a pulse width modulation control signal to the inverter, sample inverter inductor current and compare the inductor current to a reference current. A duty cycle of the pulse width modulation control signal is adjusted to drive the inductor current at a second sampling time to a value substantially equal to a reference current at a first sampling time. The systems and methods can filter harmonic distortion from output signals and control uninterruptible power supply output.

Claims

1. A method of distributing power to a load using an uninterruptible power supply having an output inverter and a filter, the filter having an inductor and a capacitor, comprising:

applying a pulse width modulation control signal to the output inverter;

periodically sampling inductor current at a first sampling time and a second sampling time;

comparing the inductor current at the first sampling time with a reference current at the first sampling time;

adjusting a duty cycle of the pulse width modulation control signal to drive the inductor current at the second sampling time towards a value substantially equal to the reference current at the first sampling time; and

applying an output voltage of the uninterruptible power supply to the load.

2. The method of claim 1, comprising:

filtering harmonic distortion from the output inverter.

3. The method of claim 2, wherein harmonic distortion output is less than or equal to 3.4% of an inverter output signal.

4. The method of claim 1, comprising:

sampling a voltage of the capacitor at the first sampling time;

obtaining the reference current at the first sampling time based at least in part on the inductor current at the first sampling time and the voltage of the capacitor at the first sampling time.

5. The method of claim 4, comprising:

initiating adjustment of the duty cycle at a first time within 10% of a first valley of a carrier signal waveform; and

obtaining an updated value of the reference current at a second time within 10% of a second valley of the carrier signal waveform.

6. The method of claim 4, comprising:

sampling a voltage of the capacitor at the second sampling time; and

wherein adjusting the duty cycle includes driving the voltage of the capacitor at the second sampling time towards a value substantially equal to a reference voltage of the capacitor at the first sampling time.

7. The method of claim 6, comprising:

adjusting the reference voltage to drive the output voltage towards a no-load voltage.

8. The method of claim 7 wherein the no-load voltage is greater than 119V.

9. The method of claim 1 wherein the reference current at the first sampling time is within 10% of the inductor current at the second sampling time.

10. The method of claim 1, comprising:

applying a load current of the uninterruptible power supply to the load.

11. The method of claim 1 wherein the first sampling time comprises a time within 10% of a first peak of a carrier signal;

and wherein the second sampling time comprises a time within 10% of a second peak of the carrier signal.

12. The method of claim 11 wherein adjusting the duty cycle comprises:

initiating the adjustment of the duty cycle within a time period less than or equal to half of a switching cycle of the carrier signal after the second sampling time.

13. The method of claim 11 wherein the first peak and the second peak are subsequent peaks of the carrier signal.

14. The method of claim 13 wherein adjusting the duty cycle comprises:

initiating adjustment of the duty cycle at a time within 10% of a valley of the carrier signal.

15. The method of claim 14, comprising:

sampling a load current output from the uninterruptable power supply at the first sampling time; and

determining the reference current based at least in part on an evaluation of the load current.

16. The method of claim 14, comprising:

sampling a load current output from the uninterruptable power supply at the first sampling time;

extrapolating the load current to determine a load current value at the valley of the carrier signal; and

determining the reference current based at least in part on an evaluation of the extrapolated load current.

17. The method of claim 1 wherein the first sampling time comprises a time within 10% of a first valley of a carrier signal;

and wherein the second sampling time comprises a time within 10% of a second valley of the carrier signal.

18. The method of claim 17 wherein the first valley and the second valley are subsequent valleys of the carrier signal.

19. The method of claim 18 wherein adjusting the duty cycle comprises:

initiating adjustment of the duty cycle at a time within 10% of a peak of the carrier signal.

20. The method of claim 19, comprising:

sampling a load current output from the uninterruptable power supply at the first sampling time; and

determining the reference current based at least in part on an evaluation of the load current.

21. The method of claim 19, comprising:

sampling a load current output from the uninterruptable power supply at the first sampling time;

extrapolating the load current to determine a load current value at the peak of the carrier signal; and

determining the reference current based at least in part on an evaluation of the extrapolated load current.

22. The method of claim 1 wherein adjusting the duty cycle comprises determining the reference current by:

implementing predictive uninterruptible power supply inverter voltage control based at least in part on a capacitance voltage of the capacitor; and

implementing predictive uninterruptible power supply inverter current control based at least in part on the inductor current.

23. The method of claim 1, wherein periodically sampling inductor current comprises periodically sampling inductor current with at least one current sensor.

24. The method of claim 1, wherein the load comprises at least one of a computer, a server, electronic communications equipment, and data storage equipment.

25. The method of claim 1, wherein applying the pulse width modulation control signal, periodically sampling inductor current, comparing the inductor current with the reference current, adjusting the duty cycle, and applying the output voltage are performed by a processor, and wherein the method is implemented in a program stored in a computer readable medium and executed by the processor.

26. An uninterruptible power supply having an output inverter and a filter, the filter having an inductor and a capacitor, comprising:

a processor configured to apply a pulse width modulation control signal to the output inverter;

the processor configured to periodically sample inductor current at a first sampling time and a second sampling time;

the processor configured to compare the inductor current at the first sampling time with a reference current at the first sampling time;

the processor configured to adjust a duty cycle of the pulse width modulation control signal to drive the inductor current at the second sampling time towards a value substantially equal to the reference current at the first sampling time; and

the uninterruptible power supply configured to apply an output voltage for a load.

27. The uninterruptible power supply of claim 26, comprising:

a filter adapted to filter harmonic distortion from the output inverter.

28. The uninterruptible power supply of claim 27, wherein harmonic distortion output is less than or equal to 3.4% of an inverter output signal.

29. The uninterruptible power supply of claim 26, comprising:

the processor configured to sample a voltage of the capacitor at the first sampling time;

the processor configured to determine the reference current at the first sampling time based at least in part on the inductor current at the first sampling time and the voltage of the capacitor at the first sampling time.

30. The uninterruptible power supply of claim 29, wherein the voltage of the capacitor is substantially equal to the output voltage.

31. The uninterruptible power supply of claim 29, comprising:

the processor configured to initiate adjustment of the duty cycle at a first time within 10% of a first valley of a carrier signal waveform; and

the processor configured to determine an updated value of the reference current at a second time within 10% of a second valley of the carrier signal waveform.

32. The uninterruptible power supply of claim 29, wherein the first peak occurs within a time period that is substantially half of a switching cycle of the carrier signal after the first valley.

33. The uninterruptible power supply of claim 29, comprising:

the processor configured to sample a voltage of the capacitor at the second sampling time; and

wherein the processor adjusts the duty cycle to drive the voltage of the capacitor at the second sampling time towards a value substantially equal to a reference voltage of the capacitor at the first sampling time.

34. The uninterruptible power supply of claim 26 wherein the first sampling time comprises a time within 10% of a first peak of a carrier signal;

and wherein the second sampling time comprises a time within 10% of a second peak of the carrier signal.

35. The uninterruptible power supply of claim 34 wherein the first peak and the second peak are subsequent peaks of the carrier signal.

36. The uninterruptible power supply of claim 34 wherein the processor is configured to initiate adjustment of the duty cycle at a time within 10% of a valley of the carrier signal.

37. The uninterruptible power supply of claim 34 wherein the processor adjusts the duty cycle within a time period less than or equal to half of a switching cycle of the carrier signal after the first sampling time.

38. The uninterruptible power supply of claim 26, wherein the output voltage is substantially equal to 120V.

39. The uninterruptible power supply of claim 26 wherein the first sampling time comprises a time within 10% of a first valley of a carrier signal;

and wherein the second sampling time comprises a time within 10% of a second valley of the carrier signal.

40. The uninterruptible power supply of claim 39 wherein the first valley and the second valley are subsequent valleys of the carrier signal.

41. The uninterruptible power supply of claim 39 wherein the processor is configured to initiate adjustment of the duty cycle at a time within 10% of a peak of the carrier signal.

42. The uninterruptible power supply of claim 26, wherein the load comprises at least one of a computer, a server, electronic communications equipment, and data storage equipment.

43. The uninterruptible power supply of claim 26, comprising:

at least one current sensor associated with the processor and configured to sample inductor current at the first sampling time or at the second sampling time.

44. The uninterruptible power supply of claim 26, wherein the uninterruptible power supply comprises a three phase uninterruptible power supply.

45. An uninterruptible power supply, comprising:

an input module configured to receive a pulse width modulation control signal;

a control module including an output inverter and a filter, the filter having an inductor;

an output module coupled to the input module and to the control module to provide output power to a load in response to the pulse width modulation control signal; and

means for adjusting a duty cycle of the pulse width modulation control signal to drive current through the inductor towards a value substantially equal to a reference current value within a time period less than or equal to a switching cycle time period of a carrier signal associated with the pulse width modulation control signal.

46. A computer readable medium having stored thereon sequences of instruction including instructions that will cause a processor to:

apply a pulse width modulation control signal to an output inverter of a power supply, the power supply including a filter having an inductor and a capacitor;

sample inductor current at a first sampling time and a second sampling time;

compare the inductor current at the first sampling time with a reference current at the first sampling time;

adjust a duty cycle of the pulse width modulation control signal to drive the inductor current at the second sampling time towards a value substantially equal to the reference current at the first sampling time; and

apply an output voltage of the uninterruptable power supply to the load.

47. The computer readable medium of claim 46, further comprising instructions that will cause the processor to:

sample a voltage of the capacitor at the first sampling time;

obtain the reference current at the first sampling time based at least in part on the inductor current at the first sampling time and the voltage of the capacitor at the first sampling time.

48. The computer readable medium of claim 47, further comprising instructions that will cause the processor to:

sample a voltage of the capacitor at the second sampling time; and

adjust the duty cycle to drive the voltage of the capacitor at the second sampling time towards a value substantially equal to a reference voltage of the capacitor at the first sampling time.

49. A system for distributing power to a load, the system having an output inverter and a filter, the filter having an inductor and a capacitor, the system comprising:

a processor configured to apply a pulse width modulation control signal to the output inverter;

the processor configured to periodically sample inductor current at a first sampling time and a second sampling time;

the processor configured to compare the inductor current at the first sampling time with a reference current at the first sampling time;

the processor configured to adjust a duty cycle of the pulse width modulation control signal to drive the inductor current at the second sampling time towards a value substantially equal to the reference current at the first sampling time; and

the processor configured to apply an output voltage for the load.

50. The system of claim 49, comprising:

the processor configured to sample a voltage of the capacitor at the first sampling time;

the processor configured to determine the reference current at the first sampling time based at least in part on the inductor current at the first sampling time and the voltage of the capacitor at the first sampling time.

51. The system of claim 49, comprising:

the processor configured to initiate adjustment of the duty cycle at a first time within 10% of a first valley of a carrier signal waveform; and

the processor configured to determine an updated value of the reference current at a second time within 10% of a second valley of the carrier signal waveform.