System for controlling phase shifting of superconducting electric machines

1. A wind turbine, comprising:

a superconducting generator comprising an armature and a superconducting field winding set located in a low-temperature region of the superconducting generator during operation of the wind turbine, the armature comprising at least one multiphase armature winding set located outside of the low-temperature region of the superconducting generator, the at least one multiphase armature winding set comprising a plurality of armature windings, the superconducting field winding set separated by a gap from the armature, the superconducting field winding set comprising a plurality of field windings, wherein one of the armature winding set and the superconducting field winding set is connectable to rotate with a rotating component of the wind turbine and another of the armature winding set and the superconducting field winding set being non-rotating;

a controllable power converter coupled to the at least one multiphase armature winding set; and

a controller configured to control switching operations of the controllable power converter to implement independent phase shifting of fundamental and switching harmonics among the plurality of armature windings of the superconducting generator to minimize losses within the low-temperature region.

2. The wind turbine of claim 1 , wherein the armature comprises a plurality of multiphase armature winding sets.

3. The wind turbine of claim 1 , further comprising implementing the phase shifting of the fundamental and switching harmonics among the plurality of armature windings of the superconducting generator as a function of time.

4. The wind turbine of claim 1 , wherein the controller is configured to phase shift fundamental frequencies of each of the plurality of armature windings relative to another of the plurality of armature windings.

5. The wind turbine of claim 1 , wherein the controller is configured to phase shift carrier signals between each of the plurality of armature windings relative to another via a phase shift angle.

6. The wind turbine of claim 1 , wherein the controller is configured to control the switching operations of the controllable power converter by modifying one or more phase shift angles thereof as a function of one or more inputs, the one or more inputs comprising at least one of a generator-commanded power, an actual power, current, a temperature of the low-temperature region, a power supplied to a cryocooler, a current supplied to the cryocooler, a measurement of heat being rejected by the cryocooler, and/or combinations thereof.

7. The wind turbine of claim 1 , further comprising a cryocooler for transporting heat from the low-temperature region to ambient via a thermodynamic cycle, the controller configured to minimize the heat which the cryocooler must reject by controlling the switching operations of the controllable power converter.

8. The wind turbine of claim 1 , wherein the superconducting field winding set is surrounded by a thermal shield maintained at a predetermined temperature range during operation of the wind turbine, the predetermined temperature range ranging from 25 Kelvin to 50 Kelvin.

9. A superconducting electric machine system, comprising:

a superconducting electric machine comprising an armature and a superconducting field winding set located in a low-temperature region of the superconducting electric machine, the armature comprising at least one multiphase armature winding set located outside of the low-temperature region of the superconducting electric machine, the at least one multiphase armature winding set comprising a plurality of armature windings, the superconducting field winding set separated by a gap from the armature, the superconducting field winding set comprising a plurality of field windings, wherein one of the armature winding set and superconducting field winding set is connectable to rotate with a rotating component of the electric machine system and another of the armature and the superconducting field winding set being non-rotating;

a controllable power converter coupled to the at least one multiphase armature winding set; and

a controller configured to control switching operations of the controllable power converter to implement independent phase shifting of fundamental and switching harmonics among the plurality of armature windings of the superconducting generator to minimize losses within the low-temperature region.

10. The superconducting electric machine system of claim 9 , further comprising implementing the phase shifting of the fundamental and switching harmonics among the plurality of armature windings of the superconducting generator as a function of time.

11. The superconducting electric machine system of claim 9 , wherein the controller is configured to phase shift fundamental frequencies of each of the plurality of armature windings relative to another of the plurality of armature windings and phase shift carrier signals between each of the plurality of armature windings relative to another via a phase shift angle.

12. The superconducting electric machine system of claim 9 , wherein the controller is configured to control the switching operations of the controllable power converter by modifying one or more phase shift angles thereof as a function of one or more inputs, the one or more inputs comprising at least one of a generator-commanded power, an actual power, current, a temperature of the low-temperature region, a power supplied to a cryocooler, a current supplied to the cryocooler, a measurement of heat being rejected by the cryocooler, and/or combinations thereof.

13. A method of operating an electric machine system, the superconducting electric machine system having a superconducting electric machine having an armature and a superconducting field winding set located in a low-temperature region of the superconducting electric machine, the armature having at least one multiphase armature winding set located outside of the low-temperature region of the superconducting electric machine, the at least one multiphase armature winding set having a plurality of armature windings, the superconducting field winding set separated by a gap from the armature, the superconducting field winding set having a plurality of field windings, wherein one of the armature winding set and superconducting field winding set is connectable to rotate with a rotating component of the wind turbine and another of the armature and the superconducting field winding set being non-rotating, the method comprising:

controlling switching operations of a controllable power converter to implement independent phase shifting of fundamental and switching harmonics among the plurality of armature windings so as to minimize losses within the low-temperature region.

14. The method of claim 13 , wherein the armature comprises a plurality of multiphase armature winding sets.

15. The method of claim 13 , further comprising implementing the phase shifting of the fundamental and switching harmonics among the plurality of armature windings of the superconducting generator as a function of time.

16. The method of claim 13 , further comprising phase shifting fundamental frequencies of each of the plurality of armature windings relative to another of the plurality of armature windings.

17. The method of claim 13 , further comprising phase shifting carrier signals between each of the plurality of armature windings relative to another via a phase shift angle.

18. The method of claim 13 , wherein controlling the switching operations of the controllable power converter further comprises:

modifying one or more phase shift angles thereof as a function of one or more inputs, the one or more inputs comprising at least one of a generator-commanded power, an actual power, current, a temperature of the low-temperature region, a power supplied to a cryocooler, a current supplied to the cryocooler, a measurement of heat being rejected by the cryocooler, and/or combinations thereof.