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

Patent metadata

Field	Value
Publication number	US-9932966-B2
Application number	US-201514800608-A
Country	US
Kind code	B2
Filing date	Jul 15, 2015
Priority date	Feb 16, 2012
Publication date	Apr 3, 2018
Grant date	Apr 3, 2018

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.

First claim

The invention claimed is:

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.

Assignees

• Alstom Renewable Technologies
• Ge Renewable Tech Wind Bv

Inventors

• Gomís Bellmunt Oriol
• Aragüés Peñalba Mónica

Classifications

• F03D9/257

  the wind motor being part of a wind farm · CPC title

• F03D7/0284

  in relation to the state of the electric grid · CPC title

• F05B2240/95

  offshore · CPC title

• F03D7/048 Primary

  controlling wind farms · CPC title

• F03D7/00

  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 title