Method and system for reducing switching losses in a high-frequency multi-cell power supply

1. A method of reducing switching losses in a power supply comprising:

advancing the output voltage of a first pole of a power cell by a first angle;

retarding the output voltage of a second pole of the power cell by a second angle; and

producing a combined output voltage of the power cell equal to a positive pulse of a duration angle equal to the sum of the first angle and the second angle for a first half of a switching cycle of the power cell, and equal to a negative pulse of a duration angle equal to the sum of the first angle and the second angle for a second half of the switching cycle of the power cell.

2. The method of claim 1 , further comprising:

performing the advancing, retarding and producing for a plurality of power cells such that the first angle used for each power cell has a different value.

3. The method claim 1 , wherein at least one of the first angle and the second angle is a negative angle.

4. The method of claim 1 , wherein the advancing and retarding are performed so that the first angle and the second angle are equal in magnitude.

5. The method of claim 1 , wherein the producing comprises:

producing, by a first pole of the power cell, a first symmetrical square-wave voltage; and

producing, a second pole of the power supply cell, a second symmetrical square-wave voltage;

wherein the first symmetrical square wave voltage and the second symmetrical square wave voltage differ in at least one of polarity and phase.

6. The method of claim 5 , wherein the first symmetrical square-wave voltage and the second symmetrical square-wave voltage are offset in phase.

7. The method of claim 1 , further comprising applying a notch of duration of a third angle and a pulse of duration of a fourth angle to a first pole during a first half of the switching cycle, such that the power cell has three degrees of freedom during the first half of the switching cycle.

8. The method of claim 7 , further comprising applying the notch of duration of the third angle and the pulse of duration of the fourth angle to a second pole during a second half of the switching cycle, such that the power cell has three degrees of freedom during the second half of the switching cycle.

9. A method of reducing switching losses in a multi-cell power supply comprising:

applying a first angle command of a selective harmonic elimination control pattern to a first power cell of a first phase group of a multi-cell power supply;

applying a second angle command of the selective harmonic elimination control pattern to a second power cell of the first phase group of the power supply, wherein at least one of the first angle command and the second angle command is a negative angle command;

applying the second angle command to a power cell other than the second power cell after a first portion of a switching cycle of the power supply; and

applying the first angle command to the second power cell.

10. The method of claim 9 , wherein the applying the first angle command of the selective harmonic elimination control pattern to the first power cell of a first phase group of the power supply and the applying the second angle command of the selective harmonic elimination control pattern to the second power cell of the first phase group of the power supply are performed concurrently.

11. The method of claim 9 , wherein the applying the second angle command to the first power cell after a first portion of a switching cycle of the power supply and the applying the first angle command to the second power cell are performed concurrently.

12. The method of claim 9 , wherein the first and second power cells generate an equal portion of total load power during an operational interval.

13. The method of claim 9 , wherein the first angle command, the second angle command, and any other angle commands are selected such that a first harmonic generated by the power supply is equal to a desired output voltage.

14. A multi-cell power supply comprising:

a plurality of power cells arranged into at least a first phase group; and

a control system in communication with the power cells, wherein the control system is configured to:

apply a first angle command of a selective harmonic elimination control pattern to first power cell of the first phase group,

apply a second angle command of the selective harmonic elimination control pattern to a second power cell of the first phase group, wherein at least one of the first angle command and the second angle command is a negative angle command,

apply the second angle command to a power cell other than the second power cell after a first portion of a switching cycle of the power supply, and

apply the first angle command to the second power cell.

15. The power supply of claim 14 , wherein the control system is further configured to apply the first angle command of the selective harmonic elimination control pattern to the first power cell of the first phase group and to apply the second angle command of the selective harmonic elimination control pattern the second power cell of the first phase group concurrently.

16. The power supply of claim 14 , wherein the control system is further configured to apply the second angle command to the first power cell and apply the first angle command to the second power cell concurrently.

17. The power supply of claim 14 , wherein the first and second power cells are configured to generate an equal portion of total load power during an operational interval.

18. The power supply of claim 14 , wherein the first angle command, the second angle command, and any other angle command are selected such that a first harmonic generated by the power supply is equal to a desired output voltage.

19. The power supply of claim 14 , wherein the control system comprises:

a torque signal producing component that receives an output from a speed regulator and a q-axis current estimate to generate a torque signal;

a flux signal producing component that receives an output from a flux regulator and a d-axis current estimate to generate a flux signal; and

current regulators that adjust the torque signal and flux signals to values to be used to command the plurality of power cells.