Method for smoothing input current to a power delivery system having regeneration capability

1. A method for smoothing input current to a power delivery system having regeneration capability, the method comprising:

evaluating input current to an input converter of the power delivery system for a first fundamental cycle;

shifting a window relative to a waveform of an input voltage after the first fundamental cycle;

evaluating input current to the input converter for a second fundamental cycle;

determining whether the input current of the second fundamental cycle is smoother than the input current of the first fundamental cycle;

shifting the window in the same direction the window was shifted after the first fundamental cycle if the input current of the second fundamental cycle is smoother than the input current of the first fundamental cycle; and

shifting the window in the opposite direction the window was shifted after the first fundamental cycle if the input current of the second fundamental cycle is not smoother than the input current of the first fundamental cycle.

2. The method of claim 1 , wherein evaluating the input current for the first fundamental cycle comprises:

determining an average value of the input current over the first fundamental cycle; and

determining a RMS value of the input current over the first fundamental cycle.

3. The method of claim 2 , wherein determining the average value of the input current over the first fundamental cycle comprises:

determining an absolute value of the input current for each of a plurality of time periods;

summing the absolute values determined for each of the plurality of time periods; and

dividing the sum of the absolute values by the number of time periods.

4. The method of claim 3 , wherein determining the RMS value of the input current over the first fundamental cycle comprises:

determining a square of the absolute value of the input current for each of the plurality of time periods;

summing the squares determined for each of the plurality of time periods;

dividing the sum of the squares by the number of time periods; and

determining the square root of:

the sum of the squares divided by the number of periods.

5. The method of claim 1 , wherein shifting the window after the first fundamental cycle comprises shifting the window forward relative to the waveform.

6. The method of claim 1 , wherein shifting the window after the first fundamental cycle comprises shifting the window backward relative to the waveform.

7. The method of claim 1 , wherein evaluating the input current for the second fundamental cycle comprises:

determining an average value of the input current over the second fundamental cycle; and

determining a RMS value of the input current over the second fundamental cycle.

8. The method of claim 7 , wherein determining the average value of the input current over the second fundamental cycle comprises:

determining an absolute value of the input current for each of a plurality of time periods;

summing the absolute values determined for each of the plurality of time periods; and

dividing the sum of the absolute values by the number of time periods.

9. The method of claim 8 , wherein determining the RMS value of the input current over the second fundamental cycle comprises:

determining a square of the absolute value of the input current for each of the plurality of time periods;

summing the squares determined for each of the plurality of time periods;

dividing the sum of the squares by the number of time periods; and

determining the square root of:

the sum of the squares divided by the number of periods.

10. The method of claim 1 , wherein determining whether the input current of the second fundamental cycle is smoother than the input current of the first fundamental cycle comprises:

determining a ratio of an average value of the input current and a RMS value of the input current for the first fundamental cycle;

determining a ratio of an average value of the input current and a RMS value of the input current for the second fundamental cycle; and

comparing the ratio for the first fundamental cycle to the ratio for the second fundamental cycle.

11. The method of claim 10 , wherein determining the ratio for the first fundamental cycle comprises:

determining the average value of the input current over the first fundamental cycle; and

determining the RMS value of the input current over the first fundamental cycle.

12. The method of claim 11 , wherein determining the average value comprises:

determining an absolute value of the input current for each of a plurality of time periods;

summing the absolute values determined for each of the plurality of time periods; and

dividing the sum of the absolute values by the number of time periods.

13. The method of claim 12 , wherein determining the RMS value comprises:

determining a square of the absolute value of the input current for each of the plurality of time periods;

summing the squares determined for each of the plurality of time periods;

dividing the sum of the squares by the number of time periods; and

determining the square root of:

the sum of the squares divided by the number of periods.

14. The method of claim 10 , wherein determining the second ratio comprises:

determining the average value of the input current over the second fundamental cycle; and

determining the RMS value of the input current over the second fundamental cycle.

15. The method of claim 14 , wherein determining the average value comprises:

determining an absolute value of the input current for each of a plurality of time periods;

summing the absolute values determined for each of the plurality of time periods; and

dividing the sum of the absolute values by the number of time periods.

16. The method of claim 15 , wherein determining the RMS value comprises:

determining a square of the absolute value of the input current for each of the plurality of time periods;

summing the squares determined for each of the plurality of time periods;

dividing the sum of the squares by the number of time periods; and

determining the square root of:

the sum of the squares divided by the number of periods;

determining a sum of average values over the second cycle; and

determining a sum of RMS values over the second cycle.

17. The method of claim 10 , further comprising deeming the input current smoother if the ratio for the first fundamental cycle is greater than the ratio for the second fundamental cycle.

18. The method of claim 10 , further comprising deeming the input current not smoother if the ratio for the first fundamental cycle is less than the ratio for the second fundamental cycle.

19. The method of claim 1 , further comprising:

evaluating input current to the input converter for a third fundamental cycle;

determining whether the input current of the third fundamental cycle is smoother than the input current of the second fundamental cycle;

shifting the window in the same direction the window was shifted after the second fundamental cycle if the input current of the third fundamental cycle is smoother than the input current of the second fundamental cycle; and

shifting the window in the opposite direction the window was shifted after the second fundamental cycle if the input current of the third fundamental cycle is not smoother than the input current of the second fundamental cycle.