Claims
- 1. A system comprising:
a permanent magnet machine; a DC link; an inverter, coupled between said permanent machine and said DC link; and a controller adapted to provide a linear decrease in voltage for said DC link when said permanent magnet machine is in at least one of an overload and fault current condition.
- 2. The system of claim 1, wherein said controller regulates a DC link voltage by adjusting a load angle and magnitude of an AC terminal voltage of said inverter with respect to an electromagnetic force (EMF) of said permanent magnet machine.
- 3. The system of claim 1, wherein said permanent magnet machine comprises a high reactance permanent magnet machine.
- 4. The system of claim 1, wherein said permanent magnet machine is thermally rated up to 270 volts DC and up to 445 amps DC.
- 5. The system of claim 1, wherein said overload and fault current conditions occur when a load current is between 445 and 605 amps DC.
- 6. The system of claim 1, wherein said controller controls the DC link voltage as a function of current when at least one of said overload and fault current conditions exist.
- 7. The system of claim 2, wherein the load angle is taken as the angle between a Park vector representing machine emf and a Park vector representing the ac terminal voltage.
- 8. The system of claim 2, wherein the controller provides a vector based current command signal as a function of the load angle and a permanent magnet machine reference signal.
- 9. The system of claim 8, wherein the controller provides a feedback current vector signal representing a detected current flowing through stator windings of the permanent magnet machine and the current vector signal and the current command signal being synchronous with respect to a rotor angle of the permanent magnet machine.
- 10. The system of claim 9, wherein the controller provides a voltage command signal to modulate the inverter, the voltage command signal being derived from the vector-based current command signal and the feedback current vector signal.
- 11. The system of claim 10, wherein said controller modulates the inverter using space vector modulation.
- 12. A method of providing overload and fault current protection to a permanent magnet machine generator, the method comprising:
determining a load angle from a measured DC link voltage and a reference DC link voltage; providing a reference current signal from said load angle; detecting a measured current from an AC generator; providing a reference voltage signal from said reference current signal; and modulating an inverter with said reference voltage signal to provide a linear decrease in current of said DC link when said permanent magnet machine is in one of at least an overload and fault current condition.
- 13. The method of claim 12, wherein the permanent magnet machine comprises a high reactance permanent magnet machine.
- 14. The method of claim 12, wherein the reference current signal is synchronous with respect to an electromagnetic force (EMF) of the permanent magnet machine.
- 15. The method of claim 12, wherein the measured current of the AC generator is synchronous with respect to an electromagnetic force (EMF) of the permanent magnet machine.
- 16. The method of claim 12, wherein said permanent magnet machine is thermally rated up to 270 volts DC and up to 445 amps DC.
- 17. The method of claim 12, wherein an overload and fault current condition occur when a load current is between 445 and 605 amps DC.
- 18. The method of claim 12, wherein the inverter is modulated using space vector modulation.
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] Related subject matter is disclosed in a U.S. patent application of Kalman et al. entitled, “Permanent Magnet Generator and Generator Control”, Ser. No. 09/746,437, filed on Dec. 21, 2000, the entire contents of which being incorporated herein by reference.