Harmonic disturbance regulator

1. A method to regulate each harmonic of a plurality of harmonics in a system having a periodic disturbance to a commanded value and the system has a rotating load adapted to operate at speeds in a speed range, the method comprising the steps of:

for each one of the plurality of harmonics:

transforming a feedback signal having at least one harmonic component due to the one of the plurality of harmonics from a source reference frame to a harmonic reference frame of the one of the plurality of harmonics to form a qd feedback signal;

subtracting the qd feedback signal from the commanded value to form a qd signal;

regulating the qd signal wherein the step of regulating the qd signal comprises the steps of:

regulating the qd signal with a proportional integral (PI) regulator at rotational speeds above a predetermined value; and

when the rotational speed goes below the predetermined value, bypassing the PI regulator and keeping the qd signal at q and d values at values that were at or above the predetermined speed,

transforming the regulated qd signal to a destination reference frame to form a compensation signal; and

adding the compensation signal to a control signal to form a qd control signal to drive the one of the plurality of harmonics towards the commanded value.

2. The method of claim 1 wherein the step of transforming the feedback signal includes the step of determining a harmonic angle of the one of the plurality of harmonics.

3. The method of claim 2 wherein the step of determining the harmonic angle comprises the steps of:

determining a value of the modulo 2π of a phase of the feedback signal multiplied by a harmonic number of the at least one harmonic; and

setting the harmonic angle to the value.

4. The method of claim 1 further comprising the step of filtering the qd feedback signal.

5. The method of claim 4 wherein the step of filtering the qd feedback signal comprises the step of filtering the feedback signal in the harmonic reference frame.

6. The method of claim 4 wherein the step of filtering the qd feedback signal comprises the step of filtering the qd feedback signal with a low pass filter.

7. The method of claim 1 wherein the step of regulating the qd signal comprises the step of regulating the qd signal using a proportional integral regulator.

8. The method of claim 1 wherein the step of transforming the regulated qd signal to a destination reference frame comprises the step of transforming the regulated qd signal to the destination reference frame based upon a destination harmonic number.

9. The method of claim 1 wherein the system has harmonics due to inverter deadtime distortion and wherein the qd feedback signal is a qd current feedback signal.

10. A computer-readable medium having computer executable instructions for performing the method of claim 1 .

11. The computer-readable medium of claim 10 having further computer-executable instructions for performing the step comprising determining a harmonic angle of the at least one harmonic.

12. The computer-readable medium of claim 11 wherein the step of determining the harmonic angle comprises the steps of:

determining a value of the modulo 2π of a phase element of the feedback signal multiplied by a harmonic number of the at least one harmonic; and

setting the harmonic angle to the value.

13. The computer-readable medium of claim 10 having further executable instructions for performing the step of filtering the qd feedback signal.

14. The computer-readable medium of claim 13 wherein the step of filtering the qd feedback signal comprises the step of filtering the feedback signal in the harmonic reference frame.

15. The computer-readable medium of claim 13 wherein the step of filtering the qd feedback signal comprises the step of filtering the qd feedback signal with a low pass filter.

16. The computer-readable medium of claim 10 wherein the step of regulating the qd signal comprises the step of regulating the qd signal using a proportional integral regulator.

17. The computer-readable medium of claim 10 wherein the step of transforming the regulated qd signal to a destination reference frame comprises the step of transforming the regulated qd signal to the destination reference frame based upon a destination harmonic number.

18. The computer-readable medium of claim 10 wherein the system has harmonics due to inverter deadtime distortion and wherein the qd feedback signal is a qd current feedback signal.