Switched reluctance motor regulation

1. A method of controlling a motor running at an operating speed, the method comprising:

determining a speed error between the operating speed and a commanded speed;

adjusting a turn-on angle in response to the speed error; and

switching to a voltage control when the turn-on angle reaches a retardation limit.

2. The method of claim 1 , wherein switching to the voltage control comprises:

activating a regulator when the turn-on angle reaches a retardation limit; and

scaling down a duty cycle output at the regulator; and

reducing the control voltage.

3. The method of claim 1 , further comprising establishing a commanded voltage limit, wherein the commanded voltage limit is a preset percentage of the operating speed.

4. The method of claim 3 , wherein the preset percentage is about 90%.

5. The method of claim 1 , further comprising detecting the operating speed.

6. The method of claim 1 , wherein adjusting the turn-on angle comprises: generating an angle command by proportionally integrating the speed error; and clipping the angle command when the angle command is outside an angle limit.

7. The method of claim 6 , wherein the voltage-frequency relationship comprises a constant voltage per hertz equation.

8. The method of claim 1 , wherein switching to the voltage control further comprises:

generating a voltage command;

generating a regulated speed by multiplying the speed error by a voltage regulating percentage; and

scaling the voltage command using the regulated speed.

9. The method of claim 1 , wherein adjusting the turn-on angle further comprises maintaining a voltage-frequency relationship.

10. A method of controlling a motor running at an operating speed, the method comprising:

determining a speed error between the operating speed and a speed command;

adjusting an angle command to minimize the speed error while maintaining a voltage-frequency relationship;

determining a retardation limit of the angle command from the speed; and

switching to a voltage control when the retardation limit is reached.

11. The method of claim 10 , wherein adjusting the angle command further comprises running the motor at a constant voltage-frequency relationship.

12. The method of claim 11 , wherein the voltage-frequency relationship comprises a voltage per hertz equation.

13. The method of claim 12 , further comprising:

compensating the voltage command with a voltage compensation limit; and

adjusting a duty cycle with the compensated voltage command.

14. The method of claim 10 , further comprising determining a voltage command from the speed command and the operating speed.

15. The method of claim 10 , further comprising adjusting an output duty cycle using the speed error.

16. The method of claim 10 , wherein the voltage-frequency relationship further comprises a constant voltage-frequency relationship.

17. The method of claim 16 , wherein the constant voltage-frequency relationship comprises a voltage per hertz equation.

18. The method of claim 10 , further comprising switching between the voltage control and adjusting the turn-on angle with at least three voltage regulators.

19. The method of claim 10 , wherein switching to the voltage control further comprises:

generating a voltage command to the motor;

generating a regulated speed by multiplying the speed error by a voltage regulating percentage; and

scaling the voltage command using the regulated speed.

20. A control system of a motor, the control system comprising:

a comparator configured to compare a feedback speed and a commanded speed, and to generate a speed difference between the feedback speed and the commanded speed;

an angle control coupled to the comparator, and configured to receive the speed difference, and to adjust a turn-on angle in response to the speed difference; and

a voltage control configured to be activated when the turn-on angle reaches a retardation limit, and to generate a voltage command.

21. The motor control system of claim 20 , wherein the voltage control further comprises a voltage command limiter configured to limit the voltage command, and to generate a limited voltage command.

22. The motor control system of claim 20 , wherein the voltage control further comprises at least one voltage regulator configured to regulate the voltage command, to reduce the voltage command when the commanded speed drops below a threshold, to generate a voltage regulating percentage, to adjust an duty cycle of the voltage command, and to maintain a constant voltage-frequency relationship.

23. The motor control system of claim 20 , wherein the angle control further comprises a proportional integrator configured to minimize a turn-on angle error.

24. The motor control system of claim 20 , further comprising a cascade accumulator configured to smooth voltage increase transition.