Method and system for transformer control

• US 7,327,134 B1
• Filed: 07/26/2006
• Issued: 02/05/2008
• Est. Priority Date: 07/26/2006
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Ritter, Allen Michael, Datta, Rajib, Weng, Haiqing, Chen, Kunlun
• Primary Examiner(s): Nguyen; Ha Tran
• Assistant Examiner(s): Nguyen; Tung X.
• Application Number:
  US11/460,064
• Publication Number:
  US 20080024114A1
• Time in Patent Office: 559 Days
• Field of Search: 324/158.1, 324/765, 324/117.R, 324/117.H, 324/127, 324/772, 324/547, 363/37.98, 363/65.39, 363/171, 363/153, 318/805, 318/138, 318/803, 318/808
• US Class Current: 324/127
• CPC Class Codes: H01F 2038/006 matrix transformer consisting of several interconnected individual transformers working as a whole
• CPC Class Codes: H01F 27/34 Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
• CPC Class Codes: H01F 27/42 Circuits specially adapted for the purpose of modifying, or compensating for, electric characteristics of transformers, reactors, or choke coils circuits for controlling transformers, reactors or choke coils, for the purpose of obtaining a desired output H02P13/00; impedance networks H03H
• CPC Class Codes: H02M 7/49 Combination of the output voltage waveforms of a plurality of converters

Abstract

A method to balance transformer flux among a plurality of transformers is disclosed. The plurality of transformers is connected to a plurality of converters, each transformer having an associated converter. The method comprises determining a reference flux value, measuring an actual flux value for each transformer, and developing a plurality of voltage command signals in relation to a plurality of variance values between the reference flux value and each actual flux value. In response to the voltage command signals being received at a modulator in signal communication with the plurality of converters, the method proceeds by generating a plurality of switching signals to reduce each of the variance values by making available the plurality of switching signals to each of the associated plurality of converters.

Claims

1. A method to balance transformer flux of a plurality of transformers connected to a plurality of converters, each transformer having an associated converter, the method comprising:

determining a reference flux value;

measuring an actual flux value for each transformer;

developing a plurality of voltage command signals in relation to a plurality of variance values between the reference flux value and each actual flux value; and

in response to the voltage command signals being received at a modulator in signal communication with the plurality of converters, generating a plurality of switching signals to reduce each of the variance values by making available the plurality of switching signals to each of the associated plurality of converters.

2. The method of claim 1, wherein the determining the reference flux value comprises:

determining an instantaneous, real-time reference flux value.

3. The method of claim 1, wherein the determining the reference flux value comprises:

determining a total flux value; and

dividing the total flux value by the number of converters, thereby providing the reference flux value.

4. The method of claim 1, wherein the developing comprises:

subtracting the reference flux value from the actual flux value for each transformer, thereby determining the variance value for each transformer; and

translating the variance value for each transformer via a flux regulator, thereby developing the voltage command signal.

5. The method of claim 4, wherein the translating comprises:

a closed-loop proportional/integral calculation.

6. The method of claim 1, wherein the generating a plurality of switching signals further comprises:

voltage command signals being received at the modulator from at least one current regulator.

7. The method of claim 1, wherein a set of the plurality of transformers is associated with a permanent magnet motor, wherein:

the determining the reference flux value comprises relating a determined flux value for the permanent magnet motor with the number of converters;

the measuring the actual flux value comprises measuring the actual flux value for each of the set of transformers; and

the developing the plurality of voltage command signals comprises developing a set of voltage command signals related to each of the set of transformers.

8. The method of claim 7, further comprising:

creating an additional voltage command signal by combining the set of developed voltage command signals; and

making available the additional voltage command signal to the modulator.

9. The method of claim 8, wherein the creating an additional voltage command signal comprises:

summing the set of developed voltage command signals, thereby creating a summed voltage command signal; and

inverting the sign of the summed voltage command signal, thereby creating the additional voltage command signal.

10. The method of claim 1, wherein a set of the plurality of transformers is associated with a grid, wherein:

the determining the reference flux value comprises combining the actual flux values for each of the set of transformers; and

the measuring the actual flux value comprises measuring the actual flux value for each of the set of transformers; and

the developing the plurality of voltage command signals comprises developing a set of voltage command signals related to each of the set of transformers.

11. A control system to balance transformer flux among a plurality of transformers connected to a plurality of converters, comprising:

a flux estimator configured to estimate a reference flux value;

a plurality of flux monitors in signal communication with each transformer, each flux monitor configured to measure an actual flux value of each transformer;

a plurality of flux comparators in signal communication with the flux estimator and each flux monitor, the plurality of flux comparators configured to determine a plurality of variance values between the reference flux value and each actual flux value;

a plurality of flux regulators in signal communication with each of the flux comparators, the plurality of flux regulators configured to develop a plurality of voltage command signals responsive to each variance value; and

a modulator in signal communication with the plurality of flux regulators and the plurality of converters, the modulator responsive to each voltage command signal and configured to generate and make available a switching signal to each converter;

wherein the switching signal is configured to reduce each variance value.

12. The system of claim 11, wherein:

a set of the plurality of transformers are series connected.

13. The system of claim 11, wherein:

the transformers are three phase transformers.

14. The system of claim 11, wherein:

the flux estimator is configured to provide an instantaneous, real-time reference flux value.

15. The system of claim 11, further comprising:

at least one current regulator in signal communication with the modulator;

wherein the at least one current regulator is configured to generate a voltage command signal responsive to current flow in the system.

16. The system of claim 11, wherein:

the modulator is a multi-pulse modulator.

17. The system of claim 11, wherein:

the modulator is a pulse width modulator.

18. The system of claim 11, wherein a set of the plurality of transformers is associated with a permanent magnet motor, wherein:

the flux estimator is configured estimate the reference flux value by relating an estimated flux value for the permanent magnet motor with the number of converters;

a set of the plurality of flux monitors is configured to measure the actual flux value of each of the set of transformers;

a set of the plurality of flux comparators is configured to determine a set of variance values between the reference flux value and each actual flux value of each of the set of transformers; and

a set of the plurality of flux regulators is configured to develop a set of voltage command signals responsive to each variance value associated with each of the set of transformers.

19. The system of claim 18, further comprising:

a voltage command signal generator in signal communication with the set of flux regulators and the modulator, the voltage command signal generator configured to create an additional voltage command signal in response to the voltage command signals developed by the set of flux regulators.

20. The system of claim 19, wherein:

the voltage command signal generator is configured to create the additional voltage command signal equal to the inverse of the sum of the voltage command signals developed by the set of flux regulators.

21. The system of claim 11, wherein a set of the plurality of transformers is associated with a grid wherein:

a set of the plurality of flux monitors is configured to measure the actual flux value of each the set of transformers;

the flux estimator is configured to estimate the reference flux value as an average of the actual flux values measured by each of the set of flux monitors;

a set of the plurality of flux comparators is configured to determine a set of variance values between the reference flux value and each actual flux value of each of the set of transformers; and

a set of the plurality of flux regulators is configured to develop a set of voltage command signals responsive to each variance values associated with each of the set of transformers.