CONVERTER TOPOLOGY AND METHODS FOR INTERFACING AN ELECTRICAL MACHINE TO ELECTRICAL POWER GRID

• US 20080037190A1
• Filed: 08/14/2006
• Published: 02/14/2008
• Est. Priority Date: 08/14/2006
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Datta, Rajib, Weng, Haiqing, Ritter, Allen M., Zhang, Richard S., Raju, Ravisekhar
• Granted Patent: US 7,532,490 B2
• Time in Patent Office: Days
• US Class Current: 361/115
• CPC Class Codes: H02M 5/271 from a three phase input voltage
• CPC Class Codes: H02M 5/297 for conversion of frequency

Abstract

A power converter for coupling an electrical machine to an electrical grid, the power converter including a machine side converter and a grid side converter, each side having a plurality of corresponding stages for converting a three-phase electrical signal of the electrical machine to a three-phase electrical signal of the electrical grid; wherein the machine side converter includes a plurality of single-phase bridges coupled in a series and has at least one coupling for coupling with the electrical machine; wherein the grid side converter includes a plurality of three-phase bridges, each three-phase bridge corresponding to one of the single-phase bridges of the machine side converter; wherein each three-phase bridge is coupled to the primary windings of a respective transformer while the secondary windings of the respective transformer are phase-shifted from the primary windings thereof and are coupled to secondary windings of another respective transformer, thus providing for coupling of the plurality of three-phase bridges in a series, wherein a transformer at the end of the series provides a coupling to at least the electrical grid; and wherein each single-phase bridge of the machine side converter is coupled to the corresponding three-phase bridge of the grid side converter by a direct current (DC) link. A method for making the power converter and a method for using the power converter are also provided.

Claims

1. A power converter for coupling an electrical machine to an electrical grid, the power converter comprising:

a machine side converter and a grid side converter, each side comprising a plurality of stages for together converting a three-phase electrical signal of the electrical machine to a three-phase electrical signal of the electrical grid;

wherein the machine side converter comprises a plurality of single-phase bridges coupled in a series and is configured for coupling with the electrical machine;

wherein the grid side converter comprises a plurality of three-phase bridges, each three-phase bridge corresponding to one of the single-phase bridges of the machine side converter;

wherein each three-phase bridge is coupled to the primary windings of a transformer while the secondary windings of the transformer are phase-shifted from the primary windings thereof and are coupled to secondary windings of another transformer, thus providing for coupling of the plurality of three-phase bridges in a series, wherein a transformer at the end of the series is configured for coupling to the electrical grid; and

wherein each single-phase bridge of the machine side converter is coupled to the corresponding three-phase bridge of the grid side converter by a direct current (DC) link.

2. The power converter as in claim 1, wherein each stage of the machine side converter comprises two single-phase bridges and each stage of the grid side converter comprises two three-phase bridges.

3. The power converter as in claim 1, wherein each stage of the machine side converter comprises six single-phase bridges and of the grid side converter six three-phase bridges.

4. The power converter as in claim 1, wherein the electrical machine comprises one of an electrical generator and an electrical load.

5. The power converter as in claim 1, wherein an output voltage level is determined by the DC link voltage of each stage and the number of stages.

6. The power converter as in claim 1, wherein the DC link for each of the single-phase bridges is isolated.

7. The power converter as in claim 1, wherein the electrical signal of the electrical machine comprises a three-phase electrical signal comprising a variable frequency.

8. The power converter as in claim 1, wherein the electrical signal of the electrical machine comprises a multi-phase electrical signal.

9. A method for converting an electric signal between an electrical machine and an electrical grid, the method comprising:

selecting a power converter comprising a machine side converter and a grid side converter, each side comprising a plurality of corresponding stages for converting a three-phase electrical signal of the electrical machine to a three-phase electrical signal of the electrical grid;

wherein the machine side converter comprises a plurality of single-phase bridges coupled in a series and comprises at least one coupling for coupling with the electrical machine;

wherein the grid side converter comprises a plurality of three-phase bridges, each three-phase bridge corresponding to one of the single-phase bridges of the machine side converter;

wherein each three-phase bridge is coupled to the primary windings of a respective transformer while the secondary windings of the respective transformer are phase-shifted from the primary windings thereof and are coupled to secondary windings of another respective transformer, thus providing for coupling of the plurality of three-phase bridges in a series, wherein a transformer at the end of the series provides a coupling to at least the electrical grid;

wherein each single-phase bridge of the machine side converter is coupled to the corresponding three-phase bridge of the grid side converter by a direct current (DC) link;

wherein the power converter comprises a coupling of the electrical machine to the machine side converter and a coupling the electrical grid to the grid side converter;

applying the electrical signal to one of the electrical machine and the electrical grid; and

controlling the power converter to convert the electrical signal.

10. The method as in claim 9, wherein controlling comprises dynamically controlling active power flow between the machine side converter and the grid side converter through the DC links such that power flow in the DC links is balanced.

11. The method as in claim 9, wherein controlling comprises controlling reactive loading of the electrical machine over a range determined by a design of the electrical machine design.

12. The method as in claim 9, wherein controlling comprises controlling reactive power at an interface with the electrical grid over a range determined by grid requirements.

13. The method as in claim 9, wherein controlling comprises maintaining a low switching frequency for the plurality of three-phase bridges with harmonic cancellation through phase shifted transformers in comparison to a pulse width modulation switching frequency for the single-phase bridges.

14. The method as in claim 9, wherein controlling comprises controlling at least one of the active power and the reactive power in the power converter.

15. The method as in claim 9, wherein a switching frequency of the grid side converter comprises of frequency of about three times the grid frequency.

16. The method as in claim 9, wherein controlling comprises providing cancellation of harmonics in the electrical signal.

17. A method for fabricating a power converter for converting an electric signal between an electrical machine and an electrical grid, the method comprising:

providing a machine side converter and a grid side converter, each side comprising a plurality of stages for converting a three-phase electrical signal of the electrical machine to a three-phase electrical signal of the electrical grid;

for the machine side converter, coupling a plurality of single-phase bridges in a series and providing at least one coupling for coupling with the electrical machine;

for the grid side converter, coupling a plurality of three-phase bridges in series, wherein each three-phase bridge corresponds to one of the single-phase bridges of the machine side converter;

coupling each three-phase bridge to primary windings of a transformer and coupling secondary windings of the transformer that are phase-shifted from the primary windings to the secondary windings of another phase-shifted transformer, and further providing a coupling from one transformer at the end of the series for coupling with the electrical grid;

coupling each single-phase bridge of the machine side converter to the corresponding three-phase bridge of the grid side converter with a direct current (DC) link.