A METHOD OF OPERATING A WIND TURBINE PLANT

• US 20150369217A1
• Filed: 02/15/2013
• Published: 12/24/2015
• Est. Priority Date: 02/15/2013
• Status: Active Grant

• Current Assignee: Vestas Wind Systems A/S
• Original Assignee: Vestas Wind Systems A/S
• Inventors: GUPTA, Amit Kumar, GUPTA, Manoj, GURU, Dilip Kumar
• Granted Patent: US 9,556,853 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F03D 7/0272 by measures acting on the electrical generator
• CPC Class Codes: F03D 7/048 controlling wind farms
• CPC Class Codes: F03D 9/257 the wind motor being part of a wind farm
• CPC Class Codes: G05B 23/0235 based on a comparison with predetermined threshold or range, e.g. "classical methods", carried out during normal operation; threshold adaptation or choice; when or how to compare with the threshold
• CPC Class Codes: H01H 71/10 Operating or release mechanisms
• CPC Class Codes: H01H 81/00 Protective switches in which contacts are normally closed but are repeatedly opened and reclosed as long as a condition causing excess current persists, e.g. for current limiting
• CPC Class Codes: H02H 3/006 Calibration or setting of parameters
• CPC Class Codes: H02H 3/025 Disconnection after limiting, e.g. when limiting is not sufficient or for facilitating disconnection
• CPC Class Codes: H02H 3/08 responsive to excess current responsive to abnormal temperature caused by excess current H02H5/04
• CPC Class Codes: H02H 7/093 against increase beyond, or decrease below, a predetermined level of rotational speed centrifugal switches H01H35/10
• CPC Class Codes: H02H 7/30 Staggered disconnection
• CPC Class Codes: H02J 2300/28 The renewable source being wind energy wind motors F03D
• CPC Class Codes: H02J 3/16 by adjustment of reactive power
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/50 Controlling the sharing of the out-of-phase component
• CPC Class Codes: H02P 9/006 Means for protecting the generator by using control H02H7/06 takes precedence; control effected upon generator excitation circuit to reduce harmful effects of overloads or transients H02P9/10
• CPC Class Codes: Y02E 10/72 Wind turbines with rotation axis in wind direction
• CPC Class Codes: Y02E 10/76 Power conversion electric or electronic aspects
• CPC Class Codes: Y02E 40/30 Reactive power compensation

Abstract

A method of operating a wind turbine plant is provided. Such a wind turbine plant comprises at least one transmission branch comprising a plurality of wind turbine generators and coupled to an electrical grid at a point of common coupling through at least one circuit breaker comprising a breaking capacity. The method comprises monitoring the electrical grid for a low voltage fault event; and if a low voltage fault event is detected: calculating a grid short circuit strength, determining a short circuit current limit if the grid short circuit strength requires an initial fault current contribution which exceeds the breaking capacity of the circuit breaker to be passed through the circuit breaker, determining a maximum fault current contribution based on the short circuit current limit and operating the wind turbine generators to provide to the electrical grid the maximum fault current contribution.

Claims

1. A method of operating a wind turbine plant comprising at least one transmission branch comprising a plurality of wind turbine generators, the transmission branch coupled to an electrical grid at a point of common coupling through at least one circuit breaker comprising a breaking capacity, the method comprising:

monitoring the wind turbine plant for a low voltage fault event; and

if a low voltage fault event is detected;

calculating a grid short circuit strength,

determining a short circuit current limit if the grid short circuit strength requires an initial fault current contribution which exceeds the breaking capacity of the circuit breaker to be passed through the circuit breaker,

determining a maximum fault current contribution based on the short circuit current limit, and

operating the wind turbine generators to provide to the electrical grid the maximum fault current contribution.

2. A method according to claim 1, further comprising:

determining a corresponding maximum fault current contribution for each wind turbine generator, based on the short circuit current limit and an output capability of each wind turbine generator.

3. A method according to claim 1, wherein calculating a grid short circuit strength comprises:

injecting a predetermined amount of reactive power into the electrical grid at a defined location within the wind turbine plant,

measuring a change in a voltage level of the grid, and

determining a grid short circuit strength by comparing the change in voltage level of the grid with the amount of injected reactive power.

4. A method according to claim 1, wherein the short circuit current limit is determined to be the breaking capacity of the circuit breaker.

5. A method according to claim 1, wherein determining the maximum fault current contribution comprises:

implementing the use of a weak grid fault injection profile in place of a conventional fault injection profile.

6. A method according to claim 5, wherein the weak grid fault injection profile is obtained by:

determining the maximum fault current contribution based on the grid short circuit strength, the present grid voltage and the breaking capacities of the circuit breakers in the plant, and

lowering the reactive current injection gain in the injection profile, such that the output of the wind turbine plant matches the maximum fault current contribution.

7. A method according to claim 1, wherein determining the maximum fault current contribution comprises:

lowering a power reference to be provided to the wind turbine generators such that the amount of fault current to be produced by the wind turbine generators drops below the short circuit current limit.

8. A method according to claim 1 wherein the low voltage fault event is any one of an electrical grid short circuit, an electrical grid fault, and a plant transmission circuit short circuit fault.

9. A method according to claim 2, wherein determining the corresponding maximum fault current contribution further comprises analyzing an operational status of the wind turbine generator.

10. A method according to claim 9, wherein determining the corresponding maximum fault current contribution further comprises analyzing an operational status of a power converter in the wind turbine generator.

11. A wind turbine plant comprising at least one transmission branch comprising a plurality of wind turbine generators, the transmission branch coupled to an electrical grid at a point of common coupling through at least one circuit breaker comprising a breaking capacity;

and a wind turbine plant power control system comprising;

a monitoring circuit configured to detect a low voltage fault event,

a short circuit strength calculation unit configured to calculate a gird short circuit strength,

a determination unit configured to determine a short circuit current limit if the grid short circuit strength requires an initial fault current contribution which exceeds the breaking capacity of the circuit breaker to be passed through the circuit breaker,

a fault current determination unit configured to determine a maximum fault current contribution based on the short circuit current limit, and

a power controller configured to send reference signals to the wind turbine generators to provide to the electrical grid the maximum fault current contribution.

12. A wind turbine plant according to claim 11, wherein the determination unit is configured to determine a corresponding maximum fault current contribution for each wind turbine generator, based on the short circuit current limit and an output capability of each wind turbine generator.

13. A wind turbine plant according to claim 11, wherein the fault current determination unit comprises a weak grid fault injection profile for use in place of a conventional fault injection profile.

14. A wind turbine plant according to claim 13, further comprising a fault injection profile determination unit configured to determine the maximum fault current contribution based on the grid short circuit strength, the present grid voltage and the breaking capacities of the circuit breakers in the plant, and lowering the reactive current injection gain in the injection profile, such that the output of the wind turbine plant matches the maximum fault current contribution.

15. A wind turbine plant according to claim 13, wherein the weak grid fault injection profile is provided to and stored in a wind turbine power converter control unit for operating the wind turbine generator.