Reaction to an overspeed event

Abstract

Provided is a method of controlling at least one wind turbine in case of a rotational overspeed situation, the method including: determining a current state related to the wind turbine; providing data related to the current state as input to a turbine model; predicting a load of at least one wind turbine component and power output of the wind turbine using the turbine model provided with the input for plural control strategies; comparing the predicted load and power output for the plural control strategies; and selecting that control strategy among the plural control strategies that satisfies a target criterion including the load and the power output.

Claims

1. A method comprising: determining a rotational speed of a main rotor of a wind turbine; identifying a controller overspeed situation when the rotational speed of the main rotor of the wind turbine exceeds a first predefined rotational speed limit but is lower than a second predetermined rotational speed limit; and continuing to operate the wind turbine and controlling the wind turbine during the controller overspeed situation, wherein controlling includes: determining a current state related to the wind turbine; providing data related to the current state as input to a turbine model; predicting a load of at least one wind turbine component and power output of the wind turbine using the turbine model provided with the input for plural control strategies, wherein the plural control strategies include curtailing the rotational speed of the wind turbine rotor and/or the power output by adjusting at least one blade pitch angle and/or adjusting a generator torque; comparing the predicted load and power output for the plural control strategies; and selecting that control strategy among the plural control strategies that satisfies a target criterion comprising the load and the power output; further wherein when the rotational speed of the main rotor of the wind turbine exceeds the second predetermined rotational speed limit a safety overspeed situation is identified and the wind turbine is shut down.

2. The method according to claim 1, wherein the target criterion includes the predicted load of at least one or plural or all wind turbine components is in an allowed range; and/or the predicted power output is maximized wherein the target criterion is in particular configurable.

3. The method according to claim 1, wherein predicting the load and power output includes modelling the behavior of the wind turbine using the turbine model provided with the input for each of the plural control strategies for a predetermined time interval and/or wherein the turbine model models each rotor blade as one single component.

4. The method according to claim 1, wherein the state comprises at least one measured and/or estimated operational parameter relating to an operation of the wind turbine, including: a measured load of at least one blade; a rotational speed; a power output; a temperature of a wind turbine component; and/or a pitch position of at least one blade, wherein the state comprises at least one measured and/or estimated environmental parameter relating an environmental condition of the wind turbine, including: a wind speed; a wind direction; a thrust; an air density; an air humidity; and/or an air temperature.

5. The method according to claim 1, wherein information from a lidar and/or a radar and/or at least one wind turbine upstream is acquired for determining evolvement and/or state of environmental condition.

6. The method according to claim 1, wherein at least one is assumed during the predetermined time interval: at least one environmental parameter is constant; at least one environmental parameter is extrapolated according to a forecast, and/or wherein an evolvement of at least one operational parameter is predicted using the wind turbine model based on the current state and/or a change of the current state.

7. The method according to claim 1, wherein the plural control strategies include maintaining residual power output.

8. The method according to claim 1, wherein the wind turbine component includes: a wind turbine tower; a wind turbine rotor blade; a wind turbine drive train; and/or at least one bearing of a rotor blade and/or of a wind turbine drive train.

9. The method according to claim 1, wherein the turbine model is an online turbine model predicting the load and power output during performing the method.

10. The method according to claim 1, wherein the turbine model is an offline turbine model that has, for plural discrete states and for the different plural control strategies, loads and power outputs pre-calculated, the method comprising: discretizing the data related to the state and feeding the discretized data to the offline turbine model; and retrieving the pre-calculated loads and power outputs based on the discretized data.

11. The method according to claim 1, further comprising: controlling the wind turbine according to the selected control strategy.

12. An arrangement for controlling at least one wind turbine, the arrangement comprising: a determining portion adapted to determine a current (operational) state related to the wind turbine; a turbine model connected to receive data related to the current (operational) state as input, wherein the model is adapted to, provided with the input, predict a load of at least one wind turbine component and power output of the wind turbine for plural predetermined control strategies; and a processor adapted to compare the load and the power output for the plural control strategies and select that control strategy among the plural control strategies that satisfies a target criterion comprising the load and the power output; wherein when a rotational speed of a main rotor of the at least one wind turbine exceeds a first predefined rotational speed limit but is lower than a second predetermined rotational speed limit a controller overspeed situation is identified and the selected control strategy includes continuing to operate the wind turbine but curtailing the rotational speed of the at least one wind turbine rotor and/or the power output by adjusting at least one blade pitch angle and/or adjusting a generator torque; and wherein when the rotational speed of the main rotor of the at least one wind turbine exceeds the second predetermined rotational speed limit a safety overspeed situation is identified and the selected control strategy includes shutting down the at least one wind turbine.

13. A wind turbine including the arrangement according to claim 12.

Description

BRIEF DESCRIPTION

(1) Some of the embodiments will be described in detail, with references to the following Figures, wherein like designations denote like members, wherein:

(2) FIG. 1 schematically illustrates a method diagram of a method of controlling at least one wind turbine in case of a rotational overspeed situation according to an embodiment of the present invention; and

(3) FIG. 2 schematically illustrates a wind turbine including an arrangement for controlling at least one wind turbine in case of a rotational overspeed situation according to an embodiment of the present invention.

DETAILED DESCRIPTION

(4) The method 1 of controlling at least one wind turbine in case of a rotational overspeed situation includes a step 3 of determining a current state related to the wind turbine. The method 1 further comprises a step 5 of providing data related to the current state as input to a turbine model. Using the turbine model in a step 7, a load of at least one wind turbine component and power output of the wind turbine is determined using the turbine model provided with the input for plural control strategies 9. In a method step 11, the predicted load and power output for the plural control strategies are compared. In a last method step 13 that control strategy among the plural control strategies that satisfies a target criterion comprising the load and the power output is selected for control of the wind turbine.

(5) FIG. 2 schematically illustrates a wind turbine 15 including an arrangement 17 for controlling at least one wind turbine in case of a rotational overspeed situation according to an embodiment of the present invention which is configured to carry out the method 1 illustrated schematically in FIG. 1. The arrangement 17 is located in the nacelle 19 of the wind turbine, wherein the nacelle 19 further comprises a converter 34 and a generator 31 and coupled to the rotor shaft 21 at which plural rotor blades 23 are connected.

(6) The method illustrated in FIG. 1 which is also carried out by the arrangement 17 is performed in case of an overspeed event of the rotor shaft 21. Therefore, the arrangement 17 comprises a determining section 25 which is adapted to determine, a current state related to the wind turbine 15. Thereby, the determining section 25 may also measure for example the speed and/or the direction of the wind 27 and other measurement values 30 related to the operation of the wind turbine 15. The arrangement 17 further comprises a turbine model 29 which is connected to receive data related to the current state as input. The model 29 is adapted to, provided with the input, predict a load of at least one wind turbine component (for example the wind turbine blade 23 and/or a load on a main rotor bearing 22 or a load of a generator 31 and/or a converter 34) and is also adapted to predict the power output 32 of the generator 31 for plural predetermined control strategies. The arrangement 17 further comprises a processor 33 adapted to compare the load and the power output for the plural control strategy and select that control strategy among the plural control strategies that satisfies a target criterion comprising the load and the power output. The load may for example also relate to the load of the wind turbine tower 35 on top of which the nacelle 19 is mounted. The arrangement 17 is adapted to output control signals 37 for controlling different components of the wind turbines, for example the pitch angle of the rotor blades, the generator torque, the converter and so on.

(7) According to an embodiment of the present invention, in advance multiple strategies for high rotational speed events are designed. Among the multiple strategies may be: 1) shut down turbine by pitching out and ramping off power; 2) curtail wind turbine in speed (and/or power) but maintain a (beneficial) power output; and 3) continue (normal operation strategy as before event was identified).

(8) When the rotational speed exceeds a predefined limit (for example a first predetermined rotational speed limit), then the following actions may be performed according to an embodiment of the present invention. The predefined speed limit could be similar to the conventional “controller overspeed limit” and may basically define a limit for when special care shall be taken, as one does not want much higher speeds that could for example exceed the “safety overspeed limit”.

(9) The following steps may be performed: 1) Initialize an online turbine model based on the current state States can be numerous candidates among: measured/estimated wind speed, wind direction (estimated) thrust, (measured) blade loads, (measured) rotational speeds, (measured) power, (measured) pitch positions, (measured or estimated) environmental properties like air density, etc. The turbine model may have dynamics for predicting relevant loads, relevant components can be for example: tower, blades and drive train. 2) Evaluate load channels running the initialized model with each of the multiple strategies for a preview window time assume values for the environmental conditions, for example: assume that current estimated or measured properties are kept or make predictions based on trends (e.g., extrapolation) or make predictions based on adding uncertainty to current values going ahead in time (assume for example that wind picks up a bit) 3) compare load channels for the multiple strategies and select that strategy that gives safe loading with highest power output for example. Other criteria may be defined. Furthermore, embodiments of the present invention may utilize preview information from for example an LIDAR, such as that assumed values for the environmental conditions can be replaced by preview/measurements. Introduce multiple strategies for high rotational speed events but make the choice not from an online model-based what-if-analysis but from offline assessment that has given some indications on the scheduling parameters. Offline assessment then has to discretize operating points and states. This may be less computational heavy online that has higher complexity in configuration of the turbine controller since strategy shall be decided based on some hard coded schemes in some operational parameters. The offline solution may be an approximation because not all states and conditions may be considered accurately.

(10) The “current state” mentioned above may include some past measured values as well as estimated parameter values (which may not be directly measurable).

(11) Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

(12) For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.