Converter lifetime improvement method for doubly fed induction generator

• US 8,736,091 B2
• Filed: 06/18/2010
• Issued: 05/27/2014
• Est. Priority Date: 06/18/2010
• Status: Active Grant

• Current Assignee: Rockwell Automation Technologies Incorporated (Rockwell Automation, Inc.)
• Original Assignee: Rockwell Automation Technologies Incorporated (Rockwell Automation, Inc.)
• Inventors: Wei, Lixiang, Kerkman, Russel J., Lukaszewski, Richard A., Lu, Haihui, Yuan, Zhenhuan
• Primary Examiner(s): Vu, Bao Q
• Assistant Examiner(s): TSEHAYE, ZEKRE A
• Application Number:
  US12/818,895
• Publication Number:
  US 20110309875A1
• Time in Patent Office: 1,439 Days
• Field of Search: 702/34, 702/176, 702/181, 324/120, 324/537, 324/210, 324/762.01, 324/522, 700/297, 700/298, 290/44, 290/55
• US Class Current: 290/44
• CPC Class Codes: G01B 3/52 preadjustable for wear or tolerance
• CPC Class Codes: G05F 1/67 to the maximum power available from a generator, e.g. from solar cell
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 7/537 using semiconductor devices only, e.g. single switched pulse inverters
• CPC Class Codes: H02P 9/007 Control circuits for doubly fed generators

Abstract

The present techniques include methods and systems for operating converter to maintain a lifespan of the converter. In some embodiments, the operating frequency of the converter may be increased such that stress may be reduced on the bond wires of the converter. More specifically, embodiments involve calculating the aging parameters for certain operating conditions of the converter operating in a maximum power point tracking (MPPT) mode and determining whether the MPPT operation results in aging the converter to a point which reduces the converter lifespan below a desired lifespan. If the MPPT operation reduces the converter lifespan below the desired lifespan, the frequency of the converter may be increased such that the converter may be controlled to operate at a percentage of MPPT. Thus, in some embodiments, power output may be optimized with respect to maintaining a desired lifespan of the converter.

Claims

1. A method comprising:

operating a rotor-side converter and a line-side inverter of a power system, wherein the rotor-side converter is coupled to a generator;

calculating an aging parameter of the line-side inverter converter;

changing a first operational mode of the rotor-side converter to a second operational mode when the aging parameter is above a threshold parameter for achieving a desired lifespan of the line-side inverter, wherein changing the first operational mode to the second operational mode comprises

increasing a first fundamental frequency of the rotor-side converter to a second fundamental frequency larger than the first fundamental frequency regardless of a speed of a rotor that corresponds to the generator.

2. The method of claim 1, wherein calculating the aging parameter comprises calculating a junction temperature variation of power devices in the line-side inverter.

3. The method of claim 1, wherein calculating the aging parameter comprises looking up a frequency, a current, and a voltage that correspond to the line-side inverter based on the first operational mode of the rotor-side converter.

4. The method of claim 1, wherein calculating the aging parameter comprises calculating a number of cycles of the line-side inverter to an estimated failure of the line-side inverter.

5. The method of claim 1, wherein calculating the aging parameter comprises looking up an estimated number of cycles of failure of the line-side inverter based on the first operational mode of the rotor-side converter.

6. The method of claim 1, wherein changing the first operational mode to the second operational mode comprises outputting a maximum power from the rotor-side converter when the rotor-side converter is operating in the first operational mode and outputting less than the maximum power from the rotor-side converter when the rotor-side converter is operating in the second operational mode.

7. The method of claim 1, wherein changing the first operational mode of the rotor-side converter to the second operational mode comprises changing the rotor-side converter from a maximum power point tracking (MPPT) operation to a percentage of the MPPT operation.

8. The method of claim 7, wherein the percentage is based on an optimization between power output by the rotor-side converter and the desired lifespan of the line-side inverter.

9. The method of claim 1, wherein the method is performed dynamically during operation of the rotor-side converter.

10. The method of claim 1, wherein the method is performed at set time intervals during operation of the rotor-side converter.

11. The method of claim 1, wherein the method is performed whenever operating parameters of the rotor-side converter change to result in calculating a different aging parameter.

12. The method of claim 1, wherein the rotor-side converter is a converter of a wind power converter system.

13. A method of delivering power to a load, the method comprising:

determining an aging parameter of a converter in a power system based on a first operational mode of the converter, wherein the converter is coupled to a generator;

comparing the aging parameter with a threshold, wherein the threshold is based on a desired lifespan of the converter; and

changing the converter to a second operational mode by increasing a fundamental frequency of the converter when the aging parameter is beyond the threshold and regardless of a speed of a rotor that corresponds to the generator.

14. The method of claim 13, wherein determining the aging parameter comprises calculating an aging per second of the converter operating at a maximum power point tracking (MPPT) mode.

15. A non-transitory computer readable medium, which when executed by a computer, causes the computer to perform the steps of:

calculating an aging parameter of a line-side inverter in a power generator, wherein the aging parameter is calculated based on a junction temperature variation of at least one switch within the line-side inverter after one output cycle of the line-side inverter, a mean junction temperature of the at least one switch, and a fundamental frequency of the line-side inverter;

changing a first operational mode of a rotor-side converter to a second operational mode when the aging parameter is above a threshold parameter for achieving a desired lifespan of the line-side inverter, wherein the rotor-side converter is coupled to a generator, and wherein changing the first operational mode to the second operational mode comprises increasing a fundamental frequency of the rotor-side converter regardless of a speed of a rotor that corresponds to the generator.