Closed loop control of excitation parameters for switch-reluctance motors
View Patent ↗A system and method for controlling the turn-on and turn-off angles of a switch reluctance motor. A control system is provided that comprises: a turn-on controller that includes a first component for controlling a turn-on angle during low speed operations and a second component for controlling the turn-on angle during high speed operations such that transitions between low speed and high speed occur naturally; and a turn-off controller having an algorithm for controlling a turn-off angle, wherein the algorithm calculates the turn-off angle as a function of rotor speed, reference peak phase current, and a set of curve fit parameters.
1. A controller for a switch reluctance motor (SRM), comprising:
a turn-on controller that includes a first component for controlling a turn-on angle during low speed operations and a second component for controlling the turn-on angle during high speed operations such that the two components automatically exchange control responsibility based on operating conditions; and
a turnoff controller having an algorithm for controlling a turn-off angle, wherein the algorithm calculates the turn-off angle as a function of rotor speed, reference peak phase current, and a set of curve fit parameters.
2. The controller of claim 1 , wherein the set of curve fit parameters are predetermined from a set for the SRM in which a range of optimal turn-off angles are calculated as a function of rotor speed and peak phase current, wherein the data set is selected from the group consisting of: simulated data and experimental data.
3. The controller of claim 2 , wherein the curve fit parameters are predetermined based on a least squares fit calculation of the data set over the range of optimal turn-off angles.
4. The controller of claim 3 , wherein the algorithm consists of four curve fit parameters.
5. The controller of claim 3 , wherein the algorithm is given by formula:
θoff= k 1 ωI ref+ k 2 ω+k 3*sqrt( I ref)+ k 4,
where ω is rotor speed, Iref is the reference current and k 1 , k 2 , k 3 and k 4 are the set of curve fit parameters.
6. The controller of claim 5 , wherein the first component of the turn-on controller causes a rotor angle position associated with a first peak of the phase current to equal the rotor angle position where an inductance begins to increase.
7. The controller of claim 5 , wherein the second component of the turn-on controller cause the turn-on angle to be advanced until peak current equals the reference peak phase current.
8. The controller of claim 1 , wherein the turn-on controller includes a limiter for limiting the turn-on angle based on the turn-off angle.
9. A system for controlling a turn-off angle for a switch reluctance motor (SRM), comprising an algorithm that calculates the turn-off angle as a function of rotor speed, reference peak phase current, and a set of curve fit parameters.
10. The system of claim 9 , wherein the set of curve fit parameters are predetermined from a data set for the SRM in which a range of optimal turn-off angles are calculated as a function of rotor speed and reference peak phase current, wherein the data set is selected from the group consisting of: simulated data and experimental data.
11. The system of claim 10 , wherein the curve fit parameters are predetermined based on a least squares fit calculation of the data set over the range of optimal turn-off angles.
12. The system of claim 11 , wherein algorithm consists of four curve fit parameters.
13. The system of claim 12 , wherein the algorithm is given by formula:
θoff= k 1 ωI ref+ k 2 ω+k 3*sqrt( I ref)+ k 4,
where ω is rotor speed, Iref is the reference current and k 1 , k 2 , k 3 and k 4 are the set of curve fit parameters.
14. The system of claim 9 , wherein the calculated turn-off angle is provided to a turn-on controller in order to provide a limit to a turn-on angle.
15. A program product stored on a recordable medium for controlling a switch reluctance motor (SRM), the program product comprising:
means for controlling a turn-on angle during low speed operations;
means for controlling the turn-on angle during high speed operations;
means for automatically transitioning between low speed and high speed operations based on operating conditions; and
means for controlling a turn-off angle, wherein said means includes an algorithm that calculates the turn-off angle as a function of rotor speed, reference peak phase current, and a set of curve fit parameters.
16. The program product of claim 15 , wherein the set of curve fit parameters are predetermined from a data set for the SRM in which a range of optimal turn-off angles are calculated as a function of rotor speed and reference peak phase current, wherein the data set comprises either simulated or experimental data.
17. The program product of claim 16 , wherein the curve fit parameters are predetermined based on a least squares fit calculation of the data set over the range of optimal turn-off angles.
18. The program product of claim 17 , wherein the algorithm is given by formula:
θoff= k 1 ωI ref+ k 2 ω+k 3*sqrt( I ref)+ k 4,
where ω is rotor speed, Iref is the reference current and k 1 , k 2 , k 3 and k 4 are the set of the set of curve fit parameters.
19. The program product of claim 15 , wherein means for controlling a turn-on angle during low speed operation causes a rotor angle position associated with a first peak of the phrase current to equal the rotor angle position where an inductance begins to increase.
20. The program product of claim 15 , wherein the means for controlling the turn-on angle during high speed operation causes the turn-on angle to be advanced until peak current equals the reference peak phase current.
21. A switch reluctance motor (SRM) controller, comprising:
a first system for controlling a turn-on angle when the SRM operates below a base speed, wherein said first system causes a rotor angle position associated with a first peak of the phase current to equal the rotor angle position where an inductance begins to increase;
a second system for controlling the turn-on angle when the SRM operates above a base speed, wherein said second system causes the turn-on angle to be advanced until peak current equals a reference current;
a third system for automatically transitioning between operation at low speed and high speed; and
a fourth system for controlling a turn-off angle, wherein said fourth system includes the algorithm that calculates the turn-off angle as a function of rotor speed, reference peak phase current, and a set of pre-calculated curve fit parameters.
22. The SRM controller of claim 21 , wherein the algorithm is given by formula:
θoff= k 1 ωI ref+ k 2 ω+k 3 I ref+ k 4,
where ω is rotor speed, Iref is the reference peak phase current and k 1 , k 2 , k 3 and k 4 are the set of pre-calculated curve fit parameters.
23. A method for controlling a turn-off angle for a switch reluctance motor (SRM), comprising the steps of:
obtaining a reference current value from a speed controller of the SRM;
obtaining a rotor speed of the SRM; and
calculating the turn-off angle as a function of rotor speed, reference peak phase current, and a set of pre-calculated curve fit parameters.
24. The method of claim 23 , wherein the set of curve fit parameters are pre-calculated from a simulated or experimental data set for the SRM in which a range of optimal turn-off angles are calculated as a function of rotor speed and peak phase current.
25. The method of claim 24 , wherein the curve fit parameters are calculated based on a least squares fit calculation of the simulated data set over the range of optimal turn-off angles.
26. The method of claim 25 , wherein the turn-off angle θoff is given by formula:
θoff= k 1 ωI ref+ k 2 ω+k 3*sqrt( I ref)+ k 4,
where ω is rotor speed, Iref is the reference peak phase current and k 1 , k 2 , k 3 and k 4 are the set of curve fit parameters.