Procedure for measuring the current in each phase of a three-phase device via single current sensor

• US 6,735,537 B2
• Filed: 03/15/2002
• Issued: 05/11/2004
• Est. Priority Date: 03/15/2002
• Status: Expired due to Fees

• Current Assignee: Continental Automotive Systems, Inc. (Continental AG)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Liu, Guang, DeʼLarminat, Ronan, Kurnia, Alexander
• Primary Examiner(s): Barlow, John
• Assistant Examiner(s): Dougherty, Anthony T
• Application Number:
  US10/099,814
• Publication Number:
  US 20030173946A1
• Time in Patent Office: 788 Days
• Field of Search: 702/64, 318/71, 318/810, 318/811, 318/606, 318/599, 324/107, 324/772, 324/142
• US Class Current: 702/64
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 7/53873 with digital control
• CPC Class Codes: H02M 7/5395 by pulse-width modulation

Abstract

A method for measuring the current in each phase of a three-phase motor (26) by the sensor (32), the motor (26) being controlled by a plurality of switching devices (S1-S6) that receive pulse width modulation signals from a controller (34). In one embodiment, a first and second sampling window (t1 and t2) are monitored. When both the first and second sampling windows (t1 and t2) are less than a minimum sampling window (mw), the voltage pulse trains associated with the highest output (V_h) and the lowest output (V_l) are shifted to form a first modified sampling window (t1′) and a modified second sampling window (t2′). When the first sampling window (t1) is less than the minimum sampling window and the second sampling window (t2) is greater than the minimum sampling window (mw), then the voltage pulse train associated with the highest output (V_h) and/or the middle output (V_m) may be shifted to form the first and second modified sampling windows (t1′ and t2′). When the first sampling window (t1) is greater than the minimum sampling window (mw) and the second sampling window (t2) is less than the minimum sampling window (mw), then the voltage pulse train associated with the lowest output (V_l) and/or the middle output (V_m) is shifted to form the first and second modified sampling windows (t1′ and t2′). The method may then sample a first current and a second current during the first and second modified sampling windows (t1′ and t2′), respectively. The third current may be calculated based on the sampling of the first and second currents.

Claims

1. A method for measuring current in each phase of a three-phase power device by a sensor, the three-phase power device controlled by a plurality of pulse width modulation signals, the method comprising the steps of:

monitoring a first and second sampling window for the pulse width modulation signals during a cycle, the cycle having a first voltage pulse train, a second voltage pulse train and a third voltage pulse train associated with each phase of the three-phase power device;

determining whether both the first and second sampling windows are less than a minimum sampling window, if both the first and second sampling windows are less than the minimum sampling window then;

shifting the first voltage pulse train to form a first modified sampling window;

shifting the third voltage pulse train to form a second modified sampling window;

determining whether the first sampling window is less than the minimum sampling window and the second sampling window is greater than the minimum sampling window, if the first sampling window is less than the minimum sampling window and the second sampling window is greater than the minimum sampling window then;

determining whether more than one of the voltage pulse trains needs to be shifted to ensure the first modified sampling window is not less than the minimum sampling window;

if it is determined that not more than one of the voltage pulse trains needs to be shifted, then shifting the first voltage pulse train to form the first modified sampling window, the second modified sampling window remaining the same as the monitored second sampling window;

if it is determined that more than one of the voltage pulse trains needs to be shifted, then shifting the first and the second voltage pulse trains to form the first and second modified sampling windows;

sampling a first current during the first modified sampling window by the sensor;

sampling a second current during the second modified sampling window by the sensor; and

calculating a third current based on the sampling of the first and second currents.

2. The method of claim 1 wherein the method further includes the steps of:

determining whether the first sampling window is greater than the minimum sampling window and the second sampling window is less than the minimum sampling window, if the first sampling window is greater than the minimum sampling window and the second sampling window is less than the minimum sampling window then;

determining whether more than one of the voltage pulse trains needs to be shifted to ensure the second modified sampling window is not less than the minimum sampling window;

if it is determined that not more than one of the voltage pulse trains needs to be shifted, then shifting the third voltage pulse train to form the second modified sampling window, the first modified sampling window remaining the same as the monitored first sampling window;

if it is determined that more than one of the voltage pulse trains needs to be shifted, then shifting the third and second voltage pulse trains to form the first and second modified sampling windows.

3. The method of claim 1 wherein the method further includes the step of determining whether a failure has occurred by sampling a fourth current by the sensor during a period when no current is expected to flow through the three-phase power device.

4. The method of claim 1 wherein the step of sampling the first current is done at about the middle of the first modified sampling window, and the step of sampling the second current is done at about the middle of the second modified sampling window.

5. The method of claim 1 wherein the steps of sampling the first and second currents are done using a counter, the counter ranging from a minimum value to a maximum value, the minimum value of the counter corresponding to the beginning and end of a cycle, the maximum value of the counter corresponding to the middle of the cycle.

6. The method of claim 1 wherein the steps of sampling of the first and second currents are done in a first cycle of a control loop period, the method further including the steps of:

sampling a fourth current during a second cycle of the control loop period;

sampling a fifth current during the second cycle of the control loop period;

averaging the fourth current and the first current to form an averaged first current; and

averaging the fifth current and the second current to form an averaged second current;

wherein the step of calculating the third current is further based on the averaged first current and the averaged second current.

7. The method of claim 1 wherein the first voltage pulse train corresponds to the voltage pulse train associated with the highest output within the cycle, the second voltage pulse train corresponds to the voltage pulse train associated with the middle output within the cycle, and the third voltage pulse train corresponds to the voltage pulse train associated with the lowest output within the cycle.

8. The method of claim 1 wherein the method is carried out in a system having a plurality of control loop periods, each period having a plurality of pulse width modulation cycles.

9. The method of claim 8 wherein the cycle during which the step of monitoring the first and second sampling windows is carried out is within one control loop period, and the steps of shifting the voltage pulse trains is carried out in each of a plurality of cycles in another control loop period.

10. A method for measuring current in each phase of a three-phase power device by a sensor, the three-phase power device controlled by a plurality of pulse width modulation signals, the method comprising the steps of:

monitoring a first and second sampling window for the pulse width modulation signals during a cycle, the cycle having a first voltage pulse train, a second voltage pulse train and a third voltage pulse train associated with each phase of the three-phase power device;

determining whether both the first and second sampling windows are less than a minimum sampling window, if both the first and second sampling windows are less than the minimum sampling window then;

shifting the first voltage pulse train to form a first modified sampling window;

shifting the third voltage pulse train to form a second modified sampling window;

determining whether the first sampling window is greater than the minimum sampling window and the second sampling window is less than the minimum sampling window, if the first sampling window is greater than the minimum sampling window and the second sampling window is less than the minimum sampling window then;

determining whether more than one of the voltage pulse trains needs to be shifted to ensure the second modified sampling window is not less than the minimum sampling window;

if it is determined that not more than one of the voltage pulse trains needs to be shifted, then shifting the third voltage pulse train to form the second modified sampling window, the first modified sampling window remaining the same as the monitored first sampling window;

if it is determined that more than one of the voltage pulse trains needs to be shifted, then shifting the third and second voltage pulse trains to form the first and second modified sampling windows;

sampling a first current during the first modified sampling window by the sensor;

sampling a second current during the second modified sampling window by the sensor; and

calculating a third current based on the sampling of the first and second currents.

11. The method of claim 10 wherein the method further includes the steps of:

determining whether the first sampling window is less than the minimum sampling window and the second sampling window is greater than the minimum sampling window, if the first sampling window is less than the minimum sampling window and the second sampling window is greater than the minimum sampling window then;

determining whether more than one of the voltage pulse trains needs to be shifted to ensure the first modified sampling window is not less than the minimum sampling window;

if it is determined that not more than one of the voltage pulse trains needs to be shifted, then shifting the first voltage pulse train to form the first modified sampling window, the second modified sampling window remaining the same as the monitored second sampling window;

if it is determined that more than one of the voltage pulse trains needs to be shifted, then shifting the first and the second voltage pulse trains to form the first and second modified sampling windows.

12. The method of claim 10 wherein the method further includes the step of determining whether a failure has occurred by sampling a fourth current by the sensor during a period when no current is expected to flow through the three-phase power device.

13. The method of claim 10 wherein the step of sampling the first current is done at about the middle of the first modified sampling window, and the step of sampling the second current is done at about the middle of the second modified sampling window.

14. The method of claim 10 wherein the steps of sampling the first and second currents are done using a counter, the counter ranging from a minimum value to a maximum value, the minimum value of the counter corresponding to the beginning and end of a cycle, the maximum value of the counter corresponding to the middle of the cycle.

15. The method of claim 10 wherein the steps of sampling of the first and second currents are done in a first cycle of a control loop period, the method further including the steps of:

sampling a fourth current during a second cycle of the control loop period;

sampling a fifth current during the second cycle of the control loop period;

averaging the fourth current and the first current to form an averaged first current; and

averaging the fifth current and the second current to form an averaged second current;

wherein the step of calculating the third current is further based on the averaged first current and the averaged second current.

16. The method of claim 10 wherein the first voltage pulse train corresponds to the voltage pulse train associated with the highest output within the cycle, the second voltage pulse train corresponds to the voltage pulse train associated with the middle output within the cycle, and the third voltage pulse train corresponds to the voltage pulse train associated with the lowest output within the cycle.

17. The method of claim 10 wherein the method is carried out in a system having a plurality of control loop periods, each period having a plurality of pulse width modulation cycles.

18. The method of claim 17 wherein the cycle during which the step of monitoring the first and second sampling windows is carried out is within one control loop period, and the steps of shifting the voltage pulse trains is carried out in each of a plurality of cycles in another control loop period.

19. A method for measuring current in each phase of a three-phase power device by a sensor, the three-phase power device controlled by a plurality of pulse width modulation signals, the method comprising the steps of:

monitoring a first time period and a second time period during a cycle, the cycle having a first voltage pulse train, a second voltage pulse train and a third voltage pulse train associated with each phase of the three-phase power device;

determining whether the first time period and second time period are both less than a predetermined minimum window, if the first time period and second time period are both less than a predetermined minimum window then;

shifting the first voltage pulse train during a second cycle to form a first sampling window;

shifting the third voltage pulse train during the second cycle to form a second sampling window;

determining whether the first time period is less than the predetermined minimum window and the second time period is greater than the predetermined minimum window, if the first time period is less than the predetermined minimum window and the second time period is greater than the predetermined minimum window then;

determining whether more than one of the voltage pulse trains needs to be shifted to ensure the first sampling window is not less than the predetermined minimum window;

if it is determined that not more than one of the voltage pulse trains needs to be shifted, then shifting the first voltage pulse train to form the first sampling window, the second sampling window being the same as the second time period;

if it is determined that more than one of the voltage pulse trains needs to be shifted, then shifting the first and second voltage pulse trains to form the first and second modified sampling windows;

sampling a first current during the first sampling window by the sensor;

sampling a second current during the second sampling window by the sensor; and

calculating a third current based on the sampling of the first and second currents.

20. The method of claim 19 wherein the method further includes the steps of:

determining whether the first time period is greater than the predetermined minimum window and the second time period is less than the predetermined minimum window, if the first time period is greater than the predetermined minimum window and the second time period is less than the predetermined minimum window then;

determining whether more than one of the voltage pulse trains needs to be shifted to ensure the second sampling window is not less than the predetermined minimum window;

if it is determined that not more than one of the voltage pulse trains needs to be shifted, then shifting the third voltage pulse train to form the second sampling window, the first sampling window being the same as the first time period;

if it is determined that more than one of the voltage pulse trains needs to be shifted, then shifting the third and the second voltage pulse trains to form the first and second sampling windows.

21. The method of claim 19 wherein the method further includes the step of determining whether a failure has occurred by sampling a fourth current by the sensor during a period when no current is expected to flow through the three-phase power device.

22. The method of claim 19 wherein the step of sampling the first current is done at about the middle of the first sampling window, and the step of sampling the second current is done at about the middle of the second sampling window.

23. The method of claim 19 wherein the steps of sampling the first and second currents are done using a counter, the counter ranging from a minimum value to a maximum value, the minimum value of the counter corresponding to the beginning and end of a cycle, the maximum value of the counter corresponding to the middle of the cycle.

24. The method of claim 19 wherein the steps of sampling of the first and second currents are done in a first cycle of a control loop period, the method further including the steps of:

sampling a fourth current during a second cycle of the control loop period;

sampling a fifth current during the second cycle of the control loop period;

averaging the fourth current and the first current to form an averaged first current; and

averaging the fifth current and the second current to form an averaged second current;

wherein the step of calculating the third current is further based on the averaged first current and the averaged second current.

25. The method of claim 19 wherein the first voltage pulse train corresponds to the voltage pulse train associated with the highest output within the cycle, the second voltage pulse train corresponds to the voltage pulse train associated with the middle output within the cycle, and the third voltage pulse train corresponds to the voltage pulse train associated with the lowest output within the cycle.

26. The method of claim 19 wherein the method is carried out in a system having a plurality of control loop periods, each period having a plurality of pulse width modulation cycles.

27. The method of claim 26 wherein the cycle during which the step of monitoring the first and second time periods is carried out is within one control loop period, and the steps of shifting the voltage pulse trains is carried out in each of a plurality of cycles in another control loop period.

28. A method for measuring current in each phase of a three-phase power device by a sensor, the three-phase power device controlled by a plurality of pulse width modulation signals, the method comprising the steps of:

monitoring a first time period and a second time period during a cycle, the cycle having a first voltage pulse train, a second voltage pulse train and a third voltage pulse train associated with each phase of the three-phase power device;

determining whether the sum of the first time period and the second time period are less than a predetermined minimum overlap value, if the sum of the first time period and the second time period are less than the predetermined minimum overlap value then;

shifting the first voltage pulse train to form a set of first sampling windows;

shifting the third voltage pulse train to form a set of second sampling windows;

sampling a set of first currents during the set of first sampling windows by the sensor;

sampling a set of second currents during the set of second sampling windows by the sensor;

averaging the set of first currents to form an averaged first current;

averaging the set of second currents to form an averaged second current; and

calculating a third current based on the averaged first current and the averaged second current.

29. The method of claim 28 wherein the method further includes the step of determining whether a failure has occurred by sampling a fourth current by the sensor during a period when no current is expected to flow through the three-phase power device.

30. The method of claim 28 wherein the step of sampling the set of first currents is done at about the middle of the first sampling windows, and the step of sampling the set of second currents is done at about the middle of the second sampling windows.

31. The method of claim 28 wherein the steps of sampling the sets of first and second currents are done using a counter, the counter ranging from a minimum value to a maximum value, the minimum value of the counter corresponding to the beginning and end of a cycle, the maximum value of the counter corresponding to the middle of the cycle.

32. The method of claim 28 wherein the steps of sampling of the sets of first and second currents are done in a first cycle of a control loop period, the method further including the steps of:

sampling a set of fourth currents during another cycle of the control loop period; and

sampling a set of fifth currents during another cycle of the control loop period;

wherein the step of averaging the set of first currents to form the averaged first current includes averaging the set of fourth currents and the set of first currents to form the averaged first current;

wherein the step of averaging the set of second currents to form the averaged second current includes averaging the set of fifth currents and the set of second currents to form the averaged second current.

33. The method of claim 28 wherein the first voltage pulse train corresponds to the voltage pulse train associated with the highest output within the cycle, the second voltage pulse train corresponds to the voltage pulse train associated with the middle output within the cycle, and the third voltage pulse train corresponds to the voltage pulse train associated with the lowest output within the cycle.

34. The method of claim 28 wherein the method is carried out in a system having a plurality of control loop periods, each period having a plurality of pulse width modulation cycles.

35. The method of claim 34 wherein the cycle during which the step of monitoring the first and second time periods is carried out is within one control loop period, and the steps of shifting the first and third voltage pulse trains is carried out in each of a plurality of cycles in another control loop period.

36. A method for measuring current in each phase of a three-phase power device by a sensor, the three-phase power device controlled by a plurality of pulse width modulation signals, the method comprising the steps of:

monitoring a first time period and a second time period during a first cycle, the first cycle having a first voltage pulse train, a second voltage pulse train and a third voltage pulse train associated with each phase of the three-phase power device;

determining whether both the first time period and the second time period are less than a predetermined minimum window, if the first time period and second time period are both less than the predetermined minimum window then;

shifting the first voltage pulse train during a second and a third cycle to form a set of first sampling windows;

shifting the third voltage pulse train during the second cycle and the third cycle to form a set of second sampling windows;

sampling a set of first currents during the set of first sampling windows by the sensor;

sampling a set of second currents during the set of second sampling windows by the sensor;

averaging the set of first currents to form an averaged first current;

averaging the set of second currents to form an averaged second current; and

calculating a third current based on the averaged first current and the averaged second current.

37. The method of claim 36 wherein the method further includes the step of determining whether a failure has occurred by sampling a fourth current by the sensor during a period when no cur-rent is expected to flow through the three-phase power device.

38. The method of claim 36 wherein the step of sampling the set of first currents is done at about the middle of the first sampling windows, and the step of sampling the set of second currents is done at about the middle of the second sampling windows.

39. The method of claim 36 wherein the steps of sampling the sets of first and second currents are done using a counter, the counter ranging from a minimum value to a maximum value, the minimum value of the counter corresponding to the beginning and end of a cycle, the maximum value of the counter corresponding to the middle of the cycle.

40. The method of claim 36 wherein the first voltage pulse train corresponds to the voltage pulse train associated with the highest output within the cycle, the second voltage pulse train corresponds to the voltage pulse train associated with the middle output within the cycle, and the third voltage pulse train corresponds to the voltage pulse train associated with the lowest output within the cycle.

41. The method of claim 36 wherein the method is carried out in a system having a plurality of control loop periods, each period having a plurality of pulse width modulation cycles.

42. The method of claim 41 wherein the cycle during which the step of monitoring the first and second time periods is carried out is within one control loop period, and the steps of shifting the first and third voltage pulse trains is carried out in each of a plurality of cycles in another control loop period.

43. A method for measuring current in each phase of a three-phase power device by a sensor, the three-phase power device controlled by a plurality of pulse width modulation signals, the method comprising the steps of:

monitoring a first time period and a second time period during a cycle, the cycle having a first voltage pulse train, a second voltage pulse train and a third voltage pulse train associated with each phase of the three-phase power device;

determining whether the first time period is less than a predetermined minimum window and whether the second time period is greater than a predetermined minimum window, if the first time period is less than a predetermined minimum window and the second time period is greater than a predetermined minimum window then;

determining whether more than one of the voltage pulse trains needs to be shifted to ensure that a first sampling window is not less than the predetermined minimum window;

if it is determined that not more than one of the voltage pulse trains needs to be shifted, then shifting the first voltage pulse train to form the first sampling window, a second sampling window being the same as the second time period;

if it is determined that more than one of the voltage pulse trains needs to be shifted, then shifting the first and second voltage pulse trains to form the first and second sampling windows;

sampling a first current during the first sampling window by the sensor;

sampling a second current during the second sampling window by the sensor; and

calculating a third current based on the first current and the second current.

44. The method of claim 43 wherein the method further includes the step of determining whether a failure has occurred by sampling a fourth current by the sensor during a period when no current is expected to flow through the three-phase power device.

45. The method of claim 43 wherein the step of sampling the first current is done at about the middle of the first sampling window, and the step of sampling the second current is done at about the middle of the second sampling window.

46. The method of claim 43 wherein the steps of sampling the first and second currents are done using a counter, the counter ranging from a minimum value to a maximum value, the minimum value of the counter corresponding to the beginning and end of a cycle, the maximum value of the counter corresponding to the middle of the cycle.

47. The method of claim 43 wherein the steps of sampling of the first and second currents are done in a first cycle of a control loop period, the method further including the steps of:

sampling a fourth current during another cycle of the control loop period;

sampling a fifth current during another cycle of the control loop period;

averaging the fourth current and the first current to form an averaged first current; and

averaging the fifth current and the second current to form an averaged second current;

wherein the step of calculating the third current is further based on the averaged first current and the averaged second current.

48. The method of claim 43 wherein the first voltage pulse train corresponds to the voltage pulse train associated with the highest output within the cycle, the second voltage pulse train corresponds to the voltage pulse train associated with the middle output within the cycle, and the third voltage pulse train corresponds to the voltage pulse train associated with the lowest output within the cycle.

49. The method of claim 43 wherein the steps of sampling the first and second currents is taken during a first half of a cycle, the method further including the steps of:

determining whether a fourth current and fifth current may be taken during a second half of the cycle, if the fourth current and fifth current may be taken during a second half of the cycle then;

sampling a fourth current during the second half of the cycle;

sampling a fifth current during the second half of the cycle;

averaging the fourth current and the second current to form an averaged second current; and

averaging the third current and the fifth current to form an averaged third current.

50. The method of claim 43 wherein the method is carried out in a system having a plurality of control loop periods, each period having a plurality of pulse width modulation cycles.

51. The method of claim 50 wherein the cycle during which the step of monitoring the first and second time periods is carried out is within one control loop period, and the steps of shifting the first and third voltage pulse trains is carried out in each of a plurality of cycles in another control loop period.

52. A method for measuring current in each phase of a three-phase power device by a sensor, the three-phase power device controlled by a plurality of pulse width modulation signals, the method comprising the steps of:

monitoring a first time period and a second time period during a cycle, the cycle having a first voltage pulse train, a second voltage pulse train and a third voltage pulse train associated with each phase of the three-phase power device;

determining whether the first time period is greater than a predetermined minimum window and whether the second time period is less than a predetermined minimum window, if the first time period is greater than a predetermined minimum window and the second time period is less than a predetermined minimum window then;

determining whether more than one of the voltage pulse trains needs to be shifted to ensure that a second sampling window is not less than the predetermined minimum window;

if it is determined that not more than one of the voltage pulse trains needs to be shifted, then shifting the third voltage pulse train to form the second sampling window, the first sampling window being the same as the first time period;

if it is determined that more than one of the voltage pulse trains needs to be shifted, then shifting the third and second voltage pulse trains to form the first and second sampling windows;

sampling a first current during the first sampling window by the sensor;

sampling a second current during the second sampling window by the sensor; and

calculating a third current based on the first current and the second current.

53. The method of claim 52 wherein the method further includes the step of determining whether a failure has occurred by sampling a fourth current by the sensor during a period when no current is expected to flow through the three-phase power device.

54. The method of claim 52 wherein the step of sampling the first current is done at about the middle of the first sampling window, and the step of sampling the second current is done at about the middle of the second sampling window.

55. The method of claim 52 wherein the steps of sampling the first and second currents are done using a counter, the counter ranging from a minimum value to a maximum value, the minimum value of the counter corresponding to the beginning and end of a cycle, the maximum value of the counter corresponding to the middle of the cycle.

56. The method of claim 52 wherein the steps of sampling of the first and second currents are done in a first cycle of a control loop period, the method further including the steps of:

sampling a fourth current during another cycle of the control loop period;

sampling a fifth current during another cycle of the control loop period;

averaging the fourth current and the first current to form an averaged first current; and

averaging the fifth current and the second current to form an averaged second current;

wherein the step of calculating the third current is further based on the averaged first current and the averaged second current.

57. The method of claim 52 wherein the first voltage pulse train corresponds to the voltage pulse train associated with the highest output within the cycle, the second voltage pulse train corresponds to the voltage pulse train associated with the middle output within the cycle, and the third voltage pulse train corresponds to the voltage pulse train associated with the lowest output within the cycle.

58. The method of claim 52 wherein the steps of sampling the first and second currents is taken during a first half of a cycle, the method further including the steps of:

determining whether a fourth current and fifth current may be taken during a second half of the cycle, if the fourth current and fifth current may be taken during a second half of the cycle then;

sampling a fourth current during the second half of the cycle;

sampling a fifth current during the second half of the cycle;

averaging the fourth current and the third current to form an averaged third current; and

averaging the fifth current and the first current to form an averaged first current.

59. The method of claim 52 wherein the method is carried out in a system having a plurality of control loop periods, each period having a plurality of pulse width modulation cycles.

60. The method of claim 59 wherein the cycle during which the step of monitoring the first and second time periods is carried out is within one control loop period, and the steps of shifting the first and third voltage pulse trains is carried out in each of a plurality of cycles in another control loop period.