Wound field synchronous machine rotor tracking using a carrier injection sensorless signal and exciter current

1. A method of initiating operation of a wound field synchronous machine in a motoring mode, comprising:

estimating an initial position of a rotor of a wound field synchronous machine using a carrier injection sensorless signal;

tracking an operating position of the rotor based on current harmonics of the wound field synchronous machine; and

calibrating the tracking using the initial position.

2. The method of claim 1 , wherein the estimating the initial position comprises interrogating the wound field synchronous machine through stator terminals of the wound field synchronous machine.

3. The method of claim 1 , wherein the current harmonics comprise current harmonics of a polyphase exciter of the wound field synchronous machine.

4. The method of claim 1 , wherein the tracking comprises measuring and demodulating the current harmonics in the wound field synchronous machine.

5. The method of claim 1 , wherein the tracking comprises locking onto a rotor position that is selected from a plurality of possible rotor positions based on the initial position.

6. The method of claim 5 , wherein the plurality of possible rotor positions are determined based on a number of exciter poles in the wound field synchronous machine, an architecture of a rectifier in the wound field synchronous machine, or both.

7. The method of claim 1 , including stopping the estimating after the calibrating.

8. The method of claim 1 , wherein the rotor is the main rotor of the wound field synchronous machine.

9. A method of tracking a rotor of a wound field synchronous machine operating in a motoring mode, comprising:

tracking a reference position of a rotor based on current harmonics of the wound field synchronous machine;

adjusting the reference position to provide an adjusted position, the adjusting based on a carrier injection sensorless signal position estimate; and

controlling the rotor based on the adjusted position.

10. The method of claim 9 , including rotatably driving a turbomachine using the wound field synchronous machine.

11. The method of claim 9 , wherein the rotor is the main rotor of the wound field synchronous machine.

12. The method of claim 9 , wherein the adjusting comprises calibrating the reference position.

13. The method of claim 9 , including stopping the carrier injection sensorless signal after the adjusting.

14. An electromechanical power transfer system, comprising:

a wound field synchronous machine configured to rotatably drive a shaft, the wound field synchronous machine having an associated main machine;

an estimator module configured to estimate an initial position of a rotor of the wound field synchronous machine using a carrier injection sensorless signal;

a tracker module configured to track an operating position of the rotor based on current harmonics of the wound field synchronous machine; and

a starter controller configured to apply a torque producing current to the wound field synchronous machine, wherein the starter controller determines an actual position of the rotor based on position information from the estimator module and the tracker module.

15. The system of claim 14 , wherein the starter controller is configured to calibrate the operating position provided by the tracker module in response to the initial position provided by the estimator module to determine the actual position.

16. The system of claim 14 , including a turbomachine that is rotatably driven by the shaft.