SOFT SWITCHING POWER ELECTRONIC TRANSFORMER

• US 20110007534A1
• Filed: 07/12/2010
• Published: 01/13/2011
• Est. Priority Date: 07/10/2009
• Status: Active Grant

• Current Assignee: Regents of The University of Minnesota (University of Minnesota)
• Original Assignee: Regents of The University of Minnesota (University of Minnesota)
• Inventors: Mohan, Ned, Mohapatra, Krushna Keshab, Basu, Kaushik, Weise, Nathan, Castelino, Gysler, Gupta, Ranjan Kumar
• Granted Patent: US 8,446,743 B2
• Time in Patent Office: Days
• US Class Current: 363/126
• CPC Class Codes: H02M 5/297 for conversion of frequency
• CPC Class Codes: H02M 7/217 using semiconductor devices only

Abstract

This patent document discloses power electronic transformers having a high-frequency link. An example apparatus include a transformer having a primary winding and a secondary winding, the transformer is configured to receive a primary power signal having a first frequency, a primary converter configured to selectively oscillate polarity of the primary windings with respect to the secondary windings at a second frequency, the second frequency substantially substantially higher than the first frequency, a secondary converter coupled to the secondary winding, the secondary converter configured to provide a load power signal using a high frequency power signal generated using the secondary winding. The secondary converter can be configured to reduce current flow in the primary winding when the polarity of the primary winding is switched, the reduced current follow is configured to reduce disturbances resulting from leakage inductance of the transformer.

Claims

1. An apparatus comprising:

a transformer having a primary winding and a secondary winding, the transformer configured to receive a primary power signal having a first frequency;

a primary converter configured to selectively oscillate polarity of the primary windings with respect to the secondary windings at a second frequency, the second frequency substantially higher than the first frequency;

a secondary converter coupled to the secondary winding, the secondary converter configured to provide a load power signal using a high frequency power signal generated using the secondary winding; and

wherein the secondary converter is configured to reduce current flow in the primary winding when the polarity of the primary winding is switched, the reduced current flow configured to reduce disturbances from leakage inductance of the transformer.

2. The apparatus of claim 1, wherein the primary windings includes at least two windings magnetically coupled to secondary winding.

3. The apparatus of claim 2, wherein the primary converter includes:

a first switch configured to couple a first primary winding to a voltage source with a first polarity; and

a second switch configured to couple a second primary winding to a voltage source with a second polarity.

4. The apparatus of claim 3, wherein the first switch and the second switch are two-quadrant switches.

5. The apparatus of claim 1, wherein the primary converter includes:

a first switch configured to couple the primary winding to a voltage source, wherein the winding is coupled to the voltage source with a first polarity using the first switch; and

a second switch configured to couple the primary winding to the voltage, wherein the winding is coupled to the voltage source with a second polarity using the second switch.

6. The apparatus of claim 5, wherein the first switch and the second switch are two-quadrant switches.

7. The apparatus of claim 1, wherein the secondary converter is configured to couple to a direct current (DC) device.

8. The apparatus of claim 7, wherein the primary converter is configured to receive a three-phase power signal;

and

the transformer is a single-phase transformer.

9. The apparatus of claim 7, wherein the primary converter is configured to receive a three-phase power signal;

and

the transformer is a three-phase transformer.

10. The apparatus of 1, wherein the primary winding includes a first primary winding and a second primary winding associated with the secondary winding, wherein the primary converter is configured to selectively couple the first primary winding and the second primary winding to a voltage source with opposite polarity.

11. A method comprising:

receiving a first alternating current (AC) power signal having a first frequency at a primary converter;

using the primary converter to selectively couple the first AC power signal to a primary winding of a transformer at a second frequency, wherein the second frequency is substantially higher than the first frequency;

receiving a second AC power signal from a secondary winding of the transformer; and

modulating the second AC power signal using a second converter to generate an output power signal having a third frequency.

12. The method of claim 11, wherein receiving the first AC power signal includes receiving a first three-phase AC power signal.

13. The method of claim 11, wherein using the primary converter to selectively couple the first AC power signal includes:

coupling the first AC power signal to the primary winding with a first polarity using a first single two-quadrant switch; and

coupling the first AC power signal to the primary winding with a second polarity using a second single two-quadrant switch.

14. The method of claim 11, wherein using the primary converter to selectively couple the first AC power signal includes:

coupling the first AC power signal to a first winding of the primary winding with a first polarity using a first single two-quadrant switch; and

coupling the first AC power signal to a second winding of the primary winding with a second polarity using a second single two-quadrant switch.

15. The method of claim 11, wherein receiving the second AC power signal includes receiving the second AC power signal from a single secondary winding of the transformer.

16. The method of claim 11, wherein receiving the second AC power signal includes receiving a three-phase second AC power signal from the secondary winding of the transformer.

17. The method of claim 11, wherein modulating the second AC power signal includes controlling the second converter to generate an average output power signal having a third frequency equal to substantially zero hertz.

18. The method of claim 11, wherein modulating the second AC power signal includes pulse width modulating the secondary power signal with a symmetric pulse.

19. The method of claim 11, wherein modulating the second AC power signal includes pulse width modulating the secondary power signal to provide a unity power factor at the primary converter.

20. A system comprising:

a power grid;

a power electronic transformer (PET) coupled to the power grid, the PET having a high frequency link operating substantially above 50 Hz;

an electronic device coupled to the PET, wherein the electronic device is at least one of a wind generator, a hybrid vehicle, a photovoltaic cell, or an energy storage device;

wherein the PET is configured to bi-directionally exchange energy between the power grid and the electronic device.