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

Patent metadata

Field	Value
Publication number	US-2016010626-A1
Application number	US-201514800608-A
Country	US
Kind code	A1
Filing date	Jul 15, 2015
Priority date	Feb 16, 2012
Publication date	Jan 14, 2016
Grant date	—

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

1 - 14 . (canceled)

15 . A method for predicting 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 at or near 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, and predicting 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.

16 . The method according to claim 15 , wherein the main land phase angle at or near the second end of the high voltage alternating current transmission is an angle of a voltage phasor at or near 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.

17 . The method according to claim 15 , wherein the individual wind turbine phase angle is measured at each of the wind turbines.

18 . The method according to claim 15 , wherein determining the main land phase angle comprises measuring the main land phase angle at or near the second end of the high voltage alternating current transmission.

19 . The method according to claim 16 , wherein determining the main land phase angle comprises measuring a phase angle at or near 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.

20 . The method according to claim 16 , wherein if 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.

21 . The method according to claim 20 , wherein if 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.

22 . The method according to claim 20 , wherein the reduction of the active power generated by the corresponding wind turbine involves the use of a DC chopper.

23 . The method according to claim 15 , wherein one or more AC reactors are provided at or near the first end and/or at or near the second end of the high voltage alternating current transmission, and wherein the method comprises disconnecting the one or more AC reactors if the difference between the at least one individual wind turbine phase angle and the main land phase angle exceeds the threshold phase angle.

24 . The method according to claim 15 , wherein the wind turbines have permanent magnet synchronous generators.

25 . The method according to claim 15 , wherein each of the wind turbines is separately connected to a medium voltage line through a medium voltage transformer.

26 . The method according to claim 15 , wherein the threshold phase angle difference is more than 60°.

27 . The method according to claim 26 , wherein the threshold phase angle difference is approximately 80°.

28 . 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 at or near 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, determining whether 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, and if the one or more differences exceeds the threshold phase angle difference, perform an action to avoid the voltage instability.

29 . The method according to claim 28 , wherein the main land phase angle at or near the second end of the high voltage alternating current transmission is an angle of a voltage phasor at or near 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.

30 . The method according to claim 28 , wherein performing an action to avoid voltage instability comprises reducing active power generated by at least one of the wind turbines.

31 . The method according to claim 29 , wherein performing an action to avoid voltage instability further comprises adjusting reactive power generated by at least one of the wind turbines.

32 . The method according to claim 29 , wherein performing an action to avoid voltage instability comprises 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.

Assignees

• Alstom Renewable Technologies

Inventors

• Gomís Bellmunt Oriol
• Aragüés Peñalba Mónica

Classifications

• F03D7/048 Primary

  controlling wind farms · CPC title

• F03D7/0284

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

• G01R25/005

  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 title

• F05B2240/95

  offshore · CPC title

• G05B15/02

  electric · CPC title