Hybrid transformer systems and methods

1. A hybrid transformer system comprising:

an electrical voltage transformer comprising:

a high-voltage winding comprising a first end and a second end, the first end having a lower voltage than the second end; and

taps disposed proximate the first end of the high-voltage winding;

a multi-level converter coupleable to at least a portion of the taps and configured to independently and simultaneously control series voltage injection and shunt VAR injection to the high-voltage winding; and

a controller electrically coupleable to the multi-level converter, such that when the multi-level converter is coupled to at least a portion of the taps of the electrical voltage transformer, the controller is configured to selectively inject at least one of shunt VARs and series voltage to the high-voltage winding of the electrical voltage transformer.

2. The transformer system of claim 1 , wherein one or more of the taps are selected from the group consisting of an up-voltage tap, a down-voltage tap, a nominal tap, and combinations thereof; and

wherein the multi-level converter is coupleable to each of the taps.

3. The transformer system of claim 1 , wherein the multi-level converter is selected from the group consisting of a two-level power converter, a three-level power converter, and a neutral-point clamped converter.

4. The transformer system of claim 1 , wherein the multi-level converter comprises a fail-normal switch.

5. The transformer system of claim 4 , wherein the fail-normal switch comprises:

a bi-directional silicon-controlled rectifier; and

a mechanical switch.

6. The transformer system of claim 1 , wherein the transformer system is not cooled using transformer oil.

7. The transformer system of claim 1 , wherein a shunt VAR injection range of the controller is dependent on the series voltage injection of the multi-level converter.

8. The transformer system of claim 1 , wherein the controller is external from the other elements of the transformer system.

9. A transformer system comprising:

an electrical voltage transformer comprising:

a high-voltage winding comprising a first end and a second end, the first end having a lower voltage than the second end; and

taps extending from locations in the first end of the high-voltage winding; and

a multi-level converter coupleable to at least a portion of the taps and configured to independently and simultaneously control series voltage injection and shunt VAR injection to the high-voltage winding;

wherein the taps comprise an up-voltage tap, a down-voltage tap, and a nominal tap;

wherein the multi-level converter comprises:

a first leg electrically coupleable to the up-voltage tap;

a second leg electrically coupleable to the down-voltage tap, the second leg in shunt with the first leg; and

a third leg in series with the nominal tap and a system neutral;

wherein the first and second legs of the multi-level converter are configured to inject voltage in shunt with the up-voltage tap and the down-voltage tap to provide the injected shunt VARs; and

wherein the third leg of the multi-level converter is configured to inject voltage between the nominal tap and the system neutral to provide the injected series voltage.

10. The transformer system of claim 9 further comprising a controller electrically coupleable to the multi-level converter, such that when the multi-level converter is coupled to at least a portion of the taps of the electrical voltage transformer, the controller is configured to selectively inject at least one of shunt VARs and series voltage to the high-voltage winding of the electrical voltage transformer.

11. The transformer system of claim 10 , wherein a shunt VAR injection range of the controller is dependent on the series voltage injection of the multi-level converter.

12. The transformer system of claim 10 , wherein the controller is external from the other elements of the transformer system.

13. The transformer system of claim 9 , wherein the transformer system is not cooled using transformer oil.

14. A hybrid transformer system for providing simultaneous series voltage injection and shunt VAR injection comprising:

an electrical voltage transformer in electrical communication with a source and comprising:

a high-voltage coil comprising a first end and a second end, the first end having a lower voltage than the second end; and

taps disposed proximate the first end of the high-voltage coil;

a multi-level converter coupleable to at least a portion of the taps and configured to independently and simultaneously control series voltage injection and shunt VAR injection to the high-voltage winding, the multi-level converter comprising:

a first leg in electrical communication with a first tap of the taps, wherein the first leg is configured to provide a shunt VAR injection to the first tap;

a second leg in electrical communication with a second tap of the taps;

a third leg in electrical communication with a system neutral and a third tap of the taps, wherein the third leg is connected in series with the third tap and system neutral, and wherein the third leg is configured to provide a series voltage injection to the high-voltage coil; and

a fail-normal switch operably coupled between the third leg of the multi-level converter and the system neutral; and

a controller electrically coupleable to the multi-level converter, such that when the multi-level converter is coupled to the taps, the controller is configured to selectively inject at least one of shunt VARs and series voltage to the high-voltage coil.

15. The transformer system of claim 14 , wherein the electrical voltage transformer is a single-phase electrical voltage transformer.

16. The transformer system of claim 14 , wherein the first tap is an up-voltage tap, the second tap is a down-voltage tap, and the third tap is a nominal tap.

17. The transformer system of claim 14 , wherein the multi-level converter is selected from the group consisting of a two-level power converter, a three-level power converter, and a neutral-point clamped converter.

18. The transformer system of claim 14 , wherein a shunt VAR injection range of the controller is dependent on the series voltage injection of the multi-level converter.

19. A method comprising:

coupling a multi-level converter of a transformer system to a high-voltage winding of an electrical voltage transformer of the transformer system;

coupling a controller to the multi-level converter;

independently and simultaneously adjusting series voltage and shunt VARS of the electrical voltage transformer by selectively injecting at least one of shunt VARs and series voltage to the multi-level converter; and

detecting at least one of the series voltage and shunt VARs of the electrical voltage transformer;

wherein the electrical voltage transformer is a single-phase electrical voltage transformer.

20. The method of claim 19 , wherein the electrical voltage transformer comprises:

the high-voltage winding comprising a first end and a second end, the first end having a lower voltage than the second end; and

taps disposed proximate the first end of the high-voltage winding.

21. The method of claim 19 , wherein a shunt VAR injection range of the multi-level controller is dependent on the series voltage injection of the multi-level converter.

22. The method of claim 19 , wherein the controller is external from the transformer system.

23. The method of claim 19 , wherein the transformer system is not cooled using transformer oil.