Variable magnetization machine controller

1. A variable magnetization machine control system comprising:

a controller configured to determine a beginning of a change in a magnetization state of a variable magnetization machine, generate a reversely rotating d-axis/q-axis current vector trajectory while the change in the magnetization state of the variable magnetization machine is occurring to drive the variable magnetization machine at a predetermined speed while maintaining the driving voltage below a predetermined maximum magnitude, determine an ending of the change in the magnetization state, and discontinue generating the reversely rotating d-axis/q-axis current vector trajectory upon determining the ending of the change in the magnetization state,

the reversely rotating d-axis/q-axis current vector trajectory including an elliptical trajectory in which q-axis current decreases after increasing as d-axis current increases and the q-axis current increases after decreasing as the d-axis current decreases.

2. The variable magnetization machine control system according to claim 1 , wherein

a radius of the elliptical trajectory has a d-axis to q-axis ratio corresponding to a ratio L q /L d where L q represents a q-axis inductance and L d represents a d-axis inductance.

3. The variable magnetization machine control system according to claim 1 , wherein

the controller is configured to establish a reverse rotating frequency of the variable magnetization machine equal to an electric fundamental frequency of the variable magnetization machine.

4. The variable magnetization machine control system according to claim 1 , wherein

the controller is configured to generate a second reversely rotating d-axis/q-axis current vector trajectory having a second elliptical trajectory during the change in a magnetization state of the variable magnetization machine, and to combine the elliptical trajectory and the second elliptical trajectory to drive the variable magnetization machine at the predetermined speed while maintaining the driving voltage below the predetermined maximum magnitude.

5. The variable magnetization machine control system according to claim 1 , wherein

the controller comprises a torque regulator that is configured to switch between the torque regulator and the controller for a reversely rotating current vector trajectory based on an operating condition of the variable magnetization machine.

6. The variable magnetization machine control system according to claim 1 , wherein

the controller comprises an open loop controller which is configured to control a d-axis voltage and a q-axis voltage to generate the reversely rotating d-axis/q-axis current vector trajectory.

7. The variable magnetization machine control system according to claim 6 , wherein

the controller further comprises a current regulator and a switch arrangement, and the controller is further configured to control the switch to alternate between providing an output of the open loop controller and an output of the current regulator to control the d-axis voltage and the q-axis voltage.

8. The variable magnetization machine control system according to claim 7 , wherein

the controller is further configured to deactivate at least one of an integrator and an accumulator in the current regulator while the controller controls the switch to provide the output of the open loop controller to control the d-axis voltage and the q-axis voltage.

9. The variable magnetization machine control system according to claim 6 , wherein

the controller is further configured to estimate the magnetization state of the variable magnetization machine based on a measured current from the variable magnetization machine and regulate the d-axis voltage and the q-axis voltage until the magnetization state corresponds to a desired magnetization state.

10. The variable magnetization machine control system according to claim 9 , wherein

the controller is further configured to regulate the d-axis voltage and the q-axis voltage by initially decreasing the d-axis voltage and the q-axis voltage to initially decrease the magnetization state corresponding to a desired magnetization state.

11. The variable magnetization machine control system according to claim 9 , wherein

the controller is further configured to regulate the d-axis voltage and the q-axis voltage by initially reversing a polarity of the d-axis voltage and the q-axis voltage.

12. The variable magnetization machine control system according to claim 1 , wherein

the controller further comprises a current regulator and a voltage feedforward component.

13. The variable magnetization machine control system according to claim 1 , wherein

the reversely rotating d-axis/q-axis current vector includes an initial point at which the q-axis current equals zero.

14. The variable magnetization machine control system according to claim 1 , wherein

the reversely rotating d-axis/q-axis current vector includes an initial point and a final point which correspond to respective points along a demagnetization border of a desired magnetization state.

15. The variable magnetization machine control system according to claim 1 , wherein

the reversely rotating d-axis/q-axis current vector includes a final point at which the q-axis current equals zero.

16. The variable magnetization machine control system according to claim 1 , wherein

the reversely rotating d-axis/q-axis current vector includes a maximum point at which the q-axis current equals zero.