Systems and methods to optimize active current sharing of parallel power converters

Patent metadata

Field	Value
Publication number	US-9450479-B2
Application number	US-201514627041-A
Country	US
Kind code	B2
Filing date	Feb 20, 2015
Priority date	Feb 20, 2015
Publication date	Sep 20, 2016
Grant date	Sep 20, 2016

Abstract

Provided is an approach for active control of cross currents flowing among multiple paralleled converters. Control of cross currents is achieved by using at least one proportional-integral (PI) controller and at least one resonant controller to target several selected dominant harmonics with infinite gains to ensure elimination of targeted harmonic cross currents in steady state. The cross currents are decomposed by into (1) common mode and differential mode components or (2) current phase domain components and each component is suppressed to a value approximately near zero using the controller. Also provided is a device comprises instructions, that, when executed by a processor, cause the processor to perform operations, which regulate and suppress cross current within a power system.

First claim

We claim:

1. A method for regulating cross-current flow within a power converter system comprising:
measuring, by a controller comprising a proportional control, an integral control, and at least one resonator control, an existing amount of cross current within each of a plurality of converters within the power converter system;
summing, by the controller, the existing amount of cross current within each of a plurality of converters to create a summed cross current;
applying, by the controller, a selective current control within the plurality of converters to suppress a common mode component, a first differential mode component, and a second differential mode component within the summed crossed current;
calculating, within one of the plurality of converters, the common mode component of the summed cross current formed by summing a current first current from a first phase of a converter, a second current from a second phase of the converter, and a third current from a third phase of the converter; and wherein
the common mode component within each of a plurality of dominant harmonics within the one of the plurality of converters is suppressed to a value approximately near zero using the controller.

2. The method of claim 1 further comprising:
calculating, for the power system, the first differential component of the summed cross current formed by summing the first differential component of each of the plurality of converters; and
calculating, for the power system, the second differential component of the summed cross current formed by summing the first differential component of each of the plurality of converters.

3. The method of claim 2 wherein the first differential component within each of a plurality of dominant harmonics within the one of the plurality of converters is suppressed to a value approximately near zero using the controller.

4. The method of claim 2 wherein the second differential component within each of a plurality of dominant harmonics within the one of the plurality of converters is suppressed to a value approximately near zero using the controller.

5. The method of claim 1 further comprising:
deriving, by the controller, an initial voltage reference from one of the plurality of converters;
performing, by the controller, a voltage limitation determined by a calculation of voltage not delivered by the converter system due to saturation;
calculating, by the controller, a loss of current corresponding to the calculated voltage not delivered by the converter system due to saturation; and
adjusting, by the controller, the existing amount of cross current by the amount of the loss of current.

6. The method of 5 , further comprising:
adding, by the controller, to the initial voltage reference, a deliverable voltage reference derived from a cross current to the initial voltage reference.

7. A method for regulating cross-current flow within a paralleled converter system comprising:
calculating, by a controller comprising a proportional control, an integral control, and at least one resonator control, an existing amount of cross current within each of a plurality of converters within the power converter system;
summing, by the controller, the existing amount of cross current within each of a plurality of converters to identify a common mode component of the cross current, a first differential mode component of the cross current, and a second differential mode component of the cross current, creating a summed cross current; and
applying, by the controller, a selective current control within the plurality of converters to suppress the common mode component of the cross current, the first differential mode current of the cross current, and the second differential mode current of the cross current within the summed crossed current;
calculating, within the one of the plurality of converters, the first phase mode current of the converter by (i) summing the first phase mode current within each of the plurality of converters to generate a summed first phase mode current, (ii) dividing the summed first phase mode current by an integer of the number of the plurality of converters to form a divided first phase mode current, and (iii) subtracting the divided first phase mode current from the first phase mode current of one of the polarity of converters; and
suppressing, by the controller, the first phase mode current within each of a plurality of dominant harmonics within the one of the plurality of converters is suppressed to a value approximately near zero.

8. The method of claim 7 further comprising:
calculating, within the one of the plurality of converters, the second phase mode current of the converter by (i) summing the second phase mode current within each of the plurality of converters to generate a summed second phase mode current, (ii) dividing the summed second phase mode current by an integer of the number of the plurality of converters to form a divided second phase mode current, and (iii) subtracting the divided second phase mode current from the second phase mode current of one of the polarity of converters; and
suppressing, by the controller, the second phase mode current within each of a plurality of dominant harmonics within the one of the plurality of converters is suppressed to a value approximately near zero.

9. The method of claim 7 further comprising:
calculating, within the one of the plurality of converters, the third phase mode current of the converter by (i) summing the third phase mode current within each of the plurality of converters to generate a summed third phase mode current, (ii) dividing the summed third phase mode current by an integer of the number of the plurality of converters to form a divided third phase mode current, and (iii) subtracting the divided third phase mode current from the third phase mode current of one of the polarity of converters; and
suppressing, by the converter, the third phase mode current within each of a plurality of dominant harmonics within the one of the plurality of converters is suppressed to a value approximately near zero using the controller.

10. The method of claim 7 further comprising:
deriving, by the controller, an initial voltage from one of the plurality of converter;
calculating, by the controller, a voltage limitation determined by a calculation of voltage not delivered to the converter system due to saturation;
calculating, by the controller, a loss of current corresponding to the calculation of voltage; and
adjusting, by the controller, the existing amount of cross current by the amount of the loss of current.

11. The method according to claim 10 , further comprising:
adding, by the controller, to the initial voltage the calculation of voltage.

12. A computer-readable device comprising instructions, that, when executed by a processor, cause the processor to perform operations, regulating cross current within a power system, comprising:
measuring, by the device, an existing amount of cross current within each of a plurality of converters within the power converter system;
summing, by a controller, the existing amount of cross current within each of a plurality of converters to create a summed cross current;
applying, by the controller, a selective current control within the plurality of converters to suppress a common mode current, a first differential mode current, and a second differential mode current within the summed crossed current,
calculating, within one of the plurality of converters, the common mode component of the summed cross current formed by summing a current first current from a first phase of a converter, a second current from a second phase

Assignees

• Ge Energy Power Conversion Technology Ltd

Inventors

• Basic Duro
• Giroux Mathieu

Classifications

• H02M7/539

  with automatic control of output wave form or frequency (H02M7/5375 - H02M7/5387 take precedence) · CPC title

• H02M1/12 Primary

  Arrangements for reducing harmonics from AC input or output · CPC title

• H02M7/493 Primary

  the static converters being arranged for operation in parallel · CPC title

• H02M1/0025

  Arrangements for modifying reference values, feedback values or error values in the control loop of a converter · CPC title

• H02M1/123

  Suppression of common mode voltage or current · CPC title