Method for controlling a wind power installation
Method for controlling a wind power installation ( 100 ) which has rotor blades ( 108 ) whose blade angle is adjustable and which can be operated at a variable speed using speed control, wherein the speed control is prepared to control the speed to a variable target speed value, comprising the steps of evaluating a test criterion for predicting an emerging overspeed, predicting an overspeed (n U ) on the basis of the at least one test criterion, and changing the speed control if an overspeed (n U ) has been predicted. Proposed are techniques that avoid an excessive increase in the rotor speed even in the event of strong wind speed increases. In particular, proposed are techniques that avoid reaching an overspeed that leads to shutdown, but without increasing the operating loads too much.
1 . A method comprising:
controlling a wind power installation having a plurality of rotor blades,
wherein:
the plurality of rotor blades have adjustable blade angles,
the wind power installation is configured to be operated at a variable speed using speed control,
the controlling of the wind power installation comprises:
controlling the speed control to a variable target speed value,
the controlling of the speed control comprises:
evaluating a test criterion for predicting an overspeed,
predicting the overspeed based on the test criterion, and
changing the speed control if the overspeed has been predicted,
the changing of the speed control includes increasing a controller gain of the speed control if the overspeed has been predicted, and
the speed control works in such a way that a speed deviation defining a difference between the variable target speed value and an actual speed value leads, via the speed control, to a planned blade angle of at least one of the adjustable blade angles or a planned adjustment rate of at least one of the adjustable blade angles.
2 . The method according to claim 1 , wherein:
the overspeed denotes a speed which reaches or exceeds a speed limit value which is above a target speed by a minimum exceedance value,
the minimum exceedance value is at least 5%, and/or
the changing of the speed control is carried out or started before the variable speed reaches the speed limit value, and/or
the changing of the speed control is only carried out or started if the variable speed is above 90% of the target speed or nominal speed.
3 . The method according to claim 2 , wherein the changing of the speed control is carried out or started before the variable speed reaches a value of 97% of the speed limit value.
4 . The method according to claim 1 , wherein:
to predict the overspeed, a speed profile is recorded as a time profile of the variable speed up to a current time and extrapolated beyond the current time to a test time to obtain an extrapolated speed profile, and
the overspeed is predicted if:
the speed profile up to the test time shows a speed increase that is above a predefinable increase limit value, and/or
the speed profile has a gradient increasing over time, and/or
the extrapolated speed profile up to the test time reaches overspeed, and/or
the extrapolated speed profile, before reaching the test time exceeds a limit speed, which is less than the overspeed.
5 . The method according to claim 4 , wherein:
quantitative changing of the speed control is carried out based on the extrapolated speed profile,
the quantitative changing of the speed control is carried out based on a magnitude of an increase of the variable speed, and/or
the quantitative changing is carried out based on a distance between the variable speed or the extrapolated speed profile and the limit speed or a speed threshold value which is less than the limit speed and greater than a target speed or nominal speed.
6 . The method according to claim 5 , wherein the quantitative changing of the speed control comprises increasing the controller gain.
7 . The method according to claim 5 , wherein, when the quantitative changing of the speed control is carried out:
the controller gain is further increased,
wherein as a speed of the extrapolated speed profile increases the extrapolated speed profile comes closer to the limit speed.
8 . The method according claim 1 , wherein:
speed control using a blade angle adjustment is provided, in which a blade angle of the rotor blades is changed based on the variable speed, and
the overspeed is predicted if the blade angle deviates from a variable reference blade angle by a predefinable differential blade angle,
an ideal blade angle is specified as the variable reference blade angle,
the ideal blade angle describes a blade angle that leads to a constant speed at a current operating point under steady-state conditions, and
the current operating point is indicated by a current speed value, a current generator power, and a current wind speed.
9 . The method according to claim 8 , wherein:
quantitative changing of the speed control is carried out based on a magnitude of a blade angle deviation of the rotor blades,
the blade angle deviates from the variable reference blade angle,
the controller gain is increased if the blade angle deviation exceeds a predetermined minimum deviation value, and/or
as the controller gain increases, the blade angle deviation becomes greater.
10 . The method according to claim 1 , wherein:
damping control is provided and involves a change in a blade angle of the rotor blades depending on a detected longitudinal oscillation of the wind power installation to dampen the detected longitudinal oscillation, and
the damping control is changed if the overspeed has been predicted.
11 . The method according to claim 10 , wherein the damping control is changed if the overspeed has been predicted,
wherein:
a gain of the damping control is reduced,
the damping control is deactivated, and/or
an adjustment of the blade angle of the rotor blades by the damping control is allowed only in a direction of a feathered position.
12 . The method according to claim 1 , wherein:
the changing of the speed control is only completely cancelled by a predeterminable extension time after a time at which the overspeed is no longer predicted,
the predeterminable extension time is in a range of 1 to 10 seconds.
13 . The method according to claim 12 , wherein the range is 2 to 5 seconds.
14 . A wind power installation comprising:
a plurality of rotor blades with adjustable blade angles,
wherein:
the wind power installation is configured to be operated at a variable speed using speed control,
the speed control is configured to control the variable speed to a variable target speed value,
the wind power installation is configured to:
evaluate a test criterion for predicting an emerging overspeed,
predict an overspeed based on the test criterion, and
change the speed control if the overspeed has been predicted,
a controller gain of the speed control is increased if the overspeed has been predicted, and
the speed control works in such a way that a speed deviation defining a difference between the variable target speed value and an actual speed value leads, via the speed control, to a planned blade angle of at least one of the adjustable blade angles or a planned adjustment rate of at least one of the adjustable blade angles.
15 . The wind power installation according to claim 14 , comprising:
an installation controller provided to control the wind power installation.