Method for avoiding voltage instability in an electrical grid of an offshore wind park

• US 9,932,966 B2
• Filed: 07/15/2015
• Issued: 04/03/2018
• Est. Priority Date: 02/16/2012
• Status: Active Grant

• Current Assignee: GE Renewable Technologies Wind B.V. (Alstom SA)
• Original Assignee: GE Renewable Technologies Wind B.V. (Alstom SA)
• Inventors: Goms Bellmunt, Oriol, Arags Pealba, Mnica
• Primary Examiner(s): Dunn, Darrin
• Application Number:
  US14/800,608
• Publication Number:
  US 20160010626A1
• Time in Patent Office: 993 Days
• CPC Class Codes: F03D 7/00 Controlling wind motors supplying or distributing electrical power H02J, e.g. arrangements for adjusting, eliminating or compensating reactive power in networks H02J3/18; controlling electric generators H02P, e.g. arrangements for controlling electric generators for the purpose of obtaining a desired output H02P9/00
• CPC Class Codes: F03D 7/0284 in relation to the state of the electric grid
• 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: F05B 2240/95 offshore
• CPC Class Codes: G01R 25/005 Circuits for comparing several input signals and for indicating the result of this comparison, e.g. equal, different, greater, smaller, or for passing one of the input signals as output signal
• CPC Class Codes: G05B 15/02 electric
• CPC Class Codes: H02J 2300/28 The renewable source being wind energy wind motors F03D
• CPC Class Codes: H02J 3/24 Arrangements for preventing or reducing oscillations of power in networks by control effected upon a single generator H02P9/00
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/48 Controlling the sharing of the in-phase component
• CPC Class Codes: Y02E 10/72 Wind turbines with rotation axis in wind direction
• CPC Class Codes: Y02E 10/727 Offshore wind turbines
• CPC Class Codes: Y02E 10/76 Power conversion electric or electronic aspects

Abstract

Method for avoiding voltage instability in an electrical grid of an offshore wind park, the offshore wind park electrical grid being connected at a first end of a high voltage alternating current (HVAC) transmission and the main land electrical grid being connected at a second end of the HVAC transmission, each of the wind turbines being connected to the wind park electrical grid, the method comprises determining a main land phase angle at or near the second end of the HVAC transmission; measuring an individual wind turbine phase angle at one or more wind turbines; determining the difference between each of the measured individual wind turbine phase angles and the main land phase angle; and determining whether the difference between one of the measured individual wind turbine phase angle and the main land phase angle exceeds a threshold phase angle difference.

Claims

1. A method for predicting and avoiding a voltage instability in an electrical grid of an offshore wind park, the offshore wind park electrical grid being connected at a first end of a high voltage alternating current transmission and a main land electrical grid being connected at a second end of the high voltage alternating current transmission, and

the offshore wind park having a plurality of wind turbines connected to the wind park electrical grid, the method comprising:

determining a main land phase angle associated with the second end of the high voltage alternating current transmission,

measuring an individual wind turbine phase angle at one or more of the wind turbines,

determining a difference between each of the one or more measured individual wind turbine phase angles and the main land phase angle,

determining a threshold phase angle difference,

predicting voltage instability and performing an action to avoid the voltage instability when at least one of the differences between the measured individual wind turbine phase angles and the main land phase angle exceeds the threshold phase angle difference; and

wherein determining the main land phase angle comprises measuring a phase angle associated with the first end of the high voltage alternating current transmission and calculating the main land phase angle at the second end based on a model of the high voltage alternating current transmission.

2. The method according to claim 1, wherein the main land phase angle associated with the second end of the high voltage alternating current transmission is an angle of a voltage phasor associated with the second end of the high voltage alternating current transmission and the individual wind turbine phase angle at one of the wind turbines is an angle of a voltage phasor at the wind turbine.

3. The method according to claim 1, wherein the individual wind turbine phase angle is measured at each of the wind turbines.

4. The method according to claim 2, wherein when a difference between the main land phase angle and an individual wind turbine phase angle exceeds the threshold phase angle, active power generated by the corresponding wind turbine is reduced to avoid voltage instability.

5. The method according to claim 2, wherein when a difference between at least one individual wind turbine phase angle and the main land phase angle exceeds the threshold phase angle, the active power generated by all the wind turbines of the wind park is reduced to avoid voltage instability.

6. The method according to claim 4, wherein the reduction of the active power generated by the corresponding wind turbine involves the use of a DC chopper.

7. The method according to claim 1, wherein one or more AC reactors are operatively provided for the first end and/or for the second end of the high voltage alternating current transmission, and wherein the method comprises disconnecting the one or more AC reactors when the difference between the at least one individual wind turbine phase angle and the main land phase angle exceeds the threshold phase angle to avoid voltage instability.

8. The method according to claim 1, wherein the wind turbines have permanent magnet synchronous generators.

9. The method according to claim 1, wherein each of the wind turbines is separately connected to a medium voltage line through a medium voltage transformer.

10. The method according to claim 1, wherein the threshold phase angle difference is more than 60°

.

11. The method according to claim 10, wherein the threshold phase angle difference is 80°

.

12. A method for avoiding voltage instability in an electrical grid of an offshore wind park, the offshore wind park electrical grid being connected at a first end of a high voltage alternating current transmission and a main land electrical grid being connected at a second end of the high voltage alternating current transmission, and

the wind park having a plurality of wind turbines, each of the wind turbines being connected to the wind park electrical grid, the method comprising:

determining a main land phase angle associated with the second end of the high voltage alternating current transmission,

measuring an individual wind turbine phase angle at one or more of the wind turbines,

determining a difference between each of the one or more measured individual wind turbine phase angles and the main land phase angle,

determining a threshold phase angle difference,

when at least one of the differences between the one or more measured individual wind turbine phase angles and the main land phase angle exceeds the threshold phase angle difference,

perform an action to avoid the voltage instability that includes adjusting active and reactive power generated by one or more of the wind turbines, and wherein the adjusted active and reactive power to be generated by each of the one or more wind turbines is determined based on the corresponding difference between the individual wind turbine phase angle and the main land phase angle.

13. The method according to claim 12, wherein the main land phase angle associated with the second end of the high voltage alternating current transmission is an angle of a voltage phasor associated with the second end of the high voltage alternating current transmission and the individual wind turbine phase angle at one of the wind turbines is an angle of a voltage phasor at the wind turbine.