Detecting a pitch angle adjustment fault
View Patent ↗A method for detecting a rotor blade pitch angle adjustment fault of a rotor blade of a wind turbine is provided, the method includes measuring a rotor blade pitch angle speed; predicting, based on an actual rotor speed, a rotor blade pitch angle speed; indicating a fault, if a first criterion is satisfied, wherein the first criterion is satisfied, if deviation between the measured rotor blade pitch angle speed and the predicted rotor blade pitch angle speed exceeds a speed threshold.
1. A method for detecting a rotor blade pitch angle adjustment fault of a rotor blade of a wind turbine, the method comprising:
measuring a rotor blade pitch angle speed during operation of the wind turbine wherein the rotor blade pitch angle speed is a speed or velocity with which a rotor blade pitch angle changes with time;
predicting, based on an actual rotor speed, a predicted rotor blade pitch angle speed; and
indicating a fault, if a first criterion is satisfied,
wherein the first criterion is satisfied, if deviation between the measured rotor blade pitch angle speed and the predicted rotor blade pitch angle speed exceeds a speed threshold wherein indicating the fault further comprises activating a safety system which increases the rotor blade pitch angle.
2. The method according to claim 1 , wherein the measured rotor blade pitch angle speed is taken as an average rotor blade pitch angle speed or a maximum rotor blade pitch angle speed among at least two rotor blades of the wind turbine.
3. The method according to claim 1 , wherein predicting the predicted rotor blade pitch angle speed is further based on a rotor acceleration and/or the rotor blade pitch angle of a respective rotor blade.
4. The method according to claim 1 , wherein predicting the predicted rotor blade pitch angle speed includes computing a derivative of a predicted rotor blade pitch angle.
5. The method according to claim 1 , wherein the predicted rotor blade pitch angle speed is derived based on a deviation between a reference rotor speed and the actual rotor speed.
6. The method according to claim 1 , wherein the predicted rotor blade pitch angle speed is derived based on an instantaneous and a time integrated deviation between a reference rotor speed and the actual rotor speed.
7. The method according to claim 1 , wherein the predicted rotor blade angle speed is derived based on a predicted rotor blade pitch angle ( ref ) defined according to:
ϑ
ref
=
G
(
ϑ
)
·
(
K
p
δ
+
∫
0
t
K
i
δ
d
t
)
wherein
G( ) is a gain function depending on a filtered blade pitch angle ,
δ is a deviation between a reference rotor speed and the actual rotor speed,
K p is a proportional gain, and
K i is an integrative gain.
8. The method according to claim 1 , wherein,
if the predicted rotor blade pitch angle speed is greater than a maximum controller pitch angle speed, the predicted rotor blade pitch angle speed is reset to the maximum controller pitch angle speed, the maximum controller pitch angle speed being a maximum speed the controller is able to change the pitch angle.
9. The method according to claim 1 , wherein
a fault is not indicated, if the measured rotor blade pitch angle speed, that is in a direction to increase the rotor blade pitch angle, is greater than a minimum rotor blade pitch angle speed threshold.
10. The method according to claim 1 , wherein
a fault is not indicated, if the rotor speed is smaller than a minimal rotor speed threshold.
11. The method according to claim 1 , wherein
the fault is indicated, if at least one of the first criterion and a second criterion is satisfied,
wherein the second criterion is satisfied, if the rotor speed is greater than a maximum rotor speed threshold.
12. The method according to claim 1 ,
wherein the fault is indicated, if at least one of the first criterion and a second criterion and a third criterion is satisfied,
wherein the second criterion is satisfied, if the rotor speed is greater than a maximum rotor speed threshold,
wherein the third criterion is satisfied, if the following holds:
rotor speed>PitchRunAwayEnableSpeed
AND
(ABS(Pitch_A_Pitch_B)>MaxPitchDeviation) OR
ABS(Pitch_B_Pitch_C)>MaxPitchDeviation) OR
ABS(Pitch_A_Pitch_C)>MaxPitchDeviation))
wherein
the PitchRunAwayEnableSpeed is a rotor speed threshold,
the Pitch_A is the rotor pitch angle of a first rotor blade,
the Pitch_B is the rotor pitch angle of a second rotor blade,
the Pitch_C is the rotor pitch angle of a third rotor blade,
the first, second and third rotor blades being connected to a shaft of the wind turbine, and
the MaxPitchDeviation is a pitch angle deviation threshold.
13. A software program stored on a non-transitory computer-readable medium, adapted, when executed on a computing system, to carry out a method according to claim 1 .
14. The method according to claim 1 , wherein the measured rotor blade pitch angle speed is taken as an average rotor blade pitch angle speed or a maximum rotor blade pitch angle speed among all rotor blades of the wind turbine.
15. The method according to claim 1 , wherein the measured rotor blade pitch angle speed is continuously measured or continuously sampled during the operation of the wind turbine.
16. A wind turbine controller comprising: an arrangement including a processor for detecting a rotor blade pitch angle adjustment fault of a rotor blade of a wind turbine, the arrangement of the wind turbine controller configured to:
receive a measured rotor blade pitch angle speed and to receive an actual rotor speed wherein the measured rotor blade pitch angle speed is a speed or velocity with which a rotor blade pitch angle changes with time:
predict, based on the actual rotor speed, a predicted rotor blade pitch angle speed and determine that a first criterion is satisfied, if a deviation between the measured rotor blade pitch angle speed and the predicted rotor blade pitch angle speed exceeds a speed threshold; and
transmit a signal to a safety system which indicates a fault, if the first criterion is satisfied wherein the safety system causes a change in the rotor blade pitch angle of the rotor blade.
17. The wind turbine controller according to claim 16 , wherein the predicted rotor blade angle speed is derived based on a predicted rotor blade pitch angle ( ref ) defined according to:
ϑ
ref
=
G
(
ϑ
)
·
(
K
p
δ
+
∫
0
t
K
i
δ
d
t
)
wherein
G( ) is a gain function depending on a filtered blade pitch angle ,
δ is a deviation between a reference rotor speed and the actual rotor speed,
K p is a proportional gain, and
K i is an integrative gain.