HYBRID DISTRIBUTION TRANSFORMER WITH AC & DC POWER CAPABILITIES

• US 20100201338A1
• Filed: 02/05/2010
• Published: 08/12/2010
• Est. Priority Date: 02/06/2009
• Status: Active Grant

• Current Assignee: Hitachi Energy Limited
• Original Assignee: ABB Research Ltd. (ABB Ltd.)
• Inventors: Gutierrez, Rafael, Tang, Le, Haj-Maharsi, Mohamed Y., Bala, Sandeep
• Granted Patent: US 9,768,704 B2
• Time in Patent Office: Days
• US Class Current: 323/305
• CPC Class Codes: H02M 1/0093 wherein the output is created by adding a regulated voltage to or subtracting it from an unregulated input
• CPC Class Codes: H02M 1/4233 using a bridge converter comprising active switches
• CPC Class Codes: H02M 5/10 using transformers
• CPC Class Codes: H02M 5/4505 having a rectifier with controlled elements
• CPC Class Codes: H02M 5/4585 having a rectifier with controlled elements
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A hybrid transformer is provided that includes an electromagnetic transformer and an AC-AC converter with a DC bridge. The AC-AC converter is operable to keep the input voltage and current of the hybrid transformer substantially in phase and to reduce fluctuation in the output voltage of the hybrid transformer in the event of an increase or decrease in the input voltage.

Claims

1. A hybrid transformer having a primary side for receiving input voltage and current from a source and a secondary side for providing output voltage and current to a load, the hybrid transformer comprising:

a ferromagnetic core;

first, second and third windings wound around the core, wherein at least one of the first, second and third windings is a primary winding for connection to the source, and at least one of the first, second and third windings is a secondary winding for connection to the load; and

an AC-AC converter comprising;

a first switching bridge connected to the first winding;

a second switching bridge connected in series with the second winding;

a DC bridge connected between the first and second switching bridges; and

a controller operable to control the first and second switching bridges to control the power factor on the primary side of the hybrid transformer and to reduce variations in the output voltage in the event of a change in the input voltage.

2. The hybrid transformer of claim 1, wherein the first and second windings are secondary windings and the third winding is a primary winding.

3. The hybrid transformer of claim 1, wherein the first and second windings are primary windings and the third winding is a secondary winding.

4. The hybrid transformer of claim 1, wherein the DC bridge comprises a plurality of capacitors and one or more taps for providing DC power to a DC load.

5. The hybrid transformer of claim 4, further comprising a normally open switch and a battery bank connected in parallel with the DC bridge, wherein when an interruption occurs in the input voltage, the switch closes, thereby providing DC power from the battery bank to the second switching bridge.

6. The hybrid transformer of claim 4, further comprising sensors and a monitoring device for monitoring the operation of the hybrid transformer, the monitoring device being connected to the one or more taps to receive DC power from the DC bridge.

7. The hybrid transformer of claim 6, wherein the monitoring device is an intelligent electronic device (IED) that receives operational data of the hybrid transformer from the sensors, the operational data including currents, voltages and temperatures in the first, second and third windings.

8. The hybrid transformer of claim 7, wherein the IED comprises the controller.

9. The hybrid transformer of claim 8, wherein the IED is connected to a remotely located control center by a communication link and is operable to transmit the operational data to the control center and to receive commands for the controller from the control center.

10. A hybrid transformer for receiving an input voltage and current from a source and providing an output voltage and current to a load, the hybrid transformer comprising:

a ferromagnetic core;

first, second third windings wound around the core, wherein at least one of the first, second and third windings is a primary winding for connection to the source, and at least one of the first, second and third windings is a secondary winding for connection to the load; and

an AC-AC converter comprising;

a first switching bridge connected to the first winding;

a second switching bridge connected in series with the second winding;

a DC bridge connected between the first and second switching bridges; and

a controller operable to control the first switching bridge to control the DC voltage across the DC bridge.

11. The hybrid transformer of claim 10, further comprising sensors and an intelligent electronic device (IED) that is connected to a remotely located control center by a communication link, the IED comprising the controller and being operable to receive operational data from the sensors, transmit the operational data to the control center and receive commands for the controller from the control center.

12. A hybrid transformer having a primary side for receiving an input voltage and current from a source and a secondary side for providing output voltage and current to a load, the distribution transformer comprising:

a ferromagnetic core;

first and second windings wound around the core, the first winding having opposing ends, a plurality of turns disposed between the ends and a tap connected to one of the turns, the tap helping define winding portions of the first winding, and wherein one of the first and second windings is a primary winding for connection to the source, and the other one of the first and second windings is a secondary winding for connection to the load;

a power electronic module connected to the tap of the first winding; and

a control device operable to control the power electronic module to regulate variations in the output voltage and control the power factor on the primary side of the hybrid transformer.

13. The hybrid transformer of claim 12, wherein the power electronic module comprises an AC-AC converter that includes first and second converters, the first converter being connected in parallel with a first one of the winding portions using the tap and the second converter being connected in series with a second one of the winding portions.

14. The hybrid transformer of claim 13, wherein the first winding is the primary winding and the second winding is the secondary winding.

15. The hybrid transformer of claim 13, wherein the first winding is the secondary winding and the second winding is the primary winding.

16. The hybrid transformer of claim 13, further comprising first and second switches, the first switch being connected in series with the first converter and the second switch being connected in parallel with the second converter.

17. The hybrid transformer of claim 16, wherein each of the first and second switches is a mechanical switch, an electronic switch or a hybrid electronic/mechanical switch.

18. The hybrid transformer of claim 16, wherein the first and second switches are controlled by the control device such that when the AC-AC converter is determined to be operating normally, the first switch is maintained in a closed position and the second switch is maintained in an open position, and when the AC-AC converter is determined to not be operating normally, the first switch is opened and the second switch is closed, thereby causing the AC-AC converter to be bypassed.

19. The hybrid transformer of claim 16, further comprising an electronic switch connected in series with an inductor and connected in parallel with the second converter.

20. The hybrid transformer of claim 13, wherein the AC-AC converter further comprises a DC bus having at least one capacitor and one or more DC taps.

21. The hybrid transformer of claim 20, wherein the one or more DC taps comprise a plurality of taps at different DC voltage levels.

22. The hybrid transformer of claim 13, wherein the first converter is connected in parallel with the first one of the winding portions using the tap and an end of the first winding.

23. The hybrid transformer of claim 13, wherein the tap is a first tap and the first winding further comprising a second tap connected to another one of the turns of the first winding;

and

wherein the first converter is connected in parallel with the first one of the winding portions using the first and second taps.

24. The hybrid transformer of claim 12, wherein the hybrid transformer is a distribution transformer.

25. The hybrid transformer of claim 12, further comprising sensors and an intelligent electronic device (IED) that is connected to a remotely located control center by a communication link, the IED comprising the controller and being operable to receive operational data from the sensors, transmit the operational data to the control center and receive commands for the controller from the control center.