Wind turbine safe mode requests and control

Abstract

Disclosed is a method and an arrangement that enable control of a wind turbine to activate a safe mode in the wind turbine. First and second systems regulated by first and second control functions respectively, are configured to receive status signals indicative of a status and / or a state of at least one sensor of a plurality of sensors in the wind turbine. The first and second systems are configured to determine fault alerts based on at least one received status signal and provide first and second safe mode requests if a fault alert is determined. A safe mode controller is configured to receive the first and second safe mode request from the first and second systems, respectively, and configured to determine a safe mode for the wind turbine based on the received first and second safe mode requests.

Description

[0001] WIND TURBINE SAFE MODE REQUESTS AND CONTROL

[0002] The present disclosure pertains to the field of wind turbine control. In particular, the present disclosure relates to a method and an arrangement for requesting and controlling safe modes of a wind turbine.

[0003] BACKGROUND

[0004] In a wind turbine, a safe mode is a state that reduces loading of the turbine in case of warning signals or faults. The reduction of loading may be a reduction in power and speed, implemented to reduce the risk of damages on the turbine. If, for example, flap blade load sensors are not operational, then certain control functions, for example a control function to reduce tilt moments and / or yaw moments on the main bearing, will not work properly and the risk of excessive loads or damages will increase accordingly. In such cases, the turbine can be put in a safe mode where it is either stopped completely (shut down) or where the power and rotational speed are de-rated to bring the loads under an acceptable level.

[0005] An example of a safe mode function is described in WO12025121, where a central system receives sensor signals, determines if an alarm scenario is met, and analyses further sensor signals in accordance with predefined steps of the met alarm scenario to determine whether the wind turbine is to be put into either a predefined safe mode, a shutdown mode, or a continued operation mode.

[0006] The operation of contemporary wind turbines involves a lot of sensors, systems and control functions that are both overlapping and inter-dependent. A fault in e.g. a sensor may have different consequences in different systems, and the determination of whether to enter a safe mode, and which safe mode to enter, is complicated.

[0007] SUMMARY

[0008] Accordingly, it would be a benefit to provide control of a wind turbine where consequences of a fault in different systems are considered when a safe mode is decided upon.

[0009] It is an object of the present invention to provide a method and an electronic device where fault alerts are determined by different systems of a wind turbine, and where the different systems then send safe mode requests to a safe mode controller that will determine a selected safe mode. Thereby, individual control functions can decide on requesting a safe mode upon detecting a fault or disturbance, such as a fault triggered by a status or a state of a sensor or similar. It can also be ensured that different safe mode requests from different control function are considered when a safe mode is determined.

[0010] Disclosed is a method for activating a safe mode operation of a wind turbine. The method comprises providing status signals indicative of statuses and / or states of sensors in the wind turbine during operation. The method comprises, in or by a first control function, determining a first fault alert based on at least one status signal, and upon determining the first fault alert, providing a first safe mode request to a safe mode controller of the wind turbine. The method comprises, in or by a second control function, determining a second fault alert based on at least one status signal, and upon determining the second fault alert, providing a second safe mode request to the safe mode controller of the wind turbine. The method comprises, in or by the safe mode controller and based on the received first and second safe mode requests, determining a safe mode for the wind turbine.

[0011] Disclosed is an arrangement for activating safe modes in a wind turbine. The arrangement comprises a first system regulated by a first control function and configured to receive status signals indicative of a status and / or a state of at least one sensor of a plurality of sensors in the wind turbine. The first system comprises processing circuitry configured to determine a first fault alert based on at least one status signal and provide a first safe mode request. The arrangement comprises a second system regulated by a second control function and configured to receive status signals indicative of a status and / or a state of at least one sensor of a plurality of sensors in the wind turbine. The second system comprises processing circuitry configured to determine a second fault alert based on at least one status signal and provide a second safe mode request. The arrangement comprises a safe mode controller configured to receive first and second safe mode request from the first and second systems, respectively, the safe mode controller comprising processing circuitry configured to determine a safe mode for the wind turbine based on the received first and second safe mode requests.

[0012] It is an advantage of the present disclosure that the safe mode controller takes safe mode requests from different control functions and systems into account when determining a safe mode for the wind turbine. A safe mode typically involves setpoints and / or adjustment of setpoints of operational settings of the wind turbine, which result in the wind turbine operating with a reduced power output. It is an advantage of the present disclosure that the determined safe mode can be selected to balance a risk of damage with a target production. It is an advantage that a dedicated control function can request a specific safe mode for this specific control function, and that the selected safe mode for the wind turbine is based on the specific requested safe modes. In this manner, the selected safe mode is based on the abilities of control functions experiencing the actual faults and not on worst case situations.

[0013] BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The above and other features and advantages of the present disclosure will become readily apparent to those skilled in the art by the following detailed description of exemplary embodiments thereof with reference to the attached drawings, in which:

[0015] Fig. 1 is a flow-chart illustrating an exemplary method for activating a safe mode operation of a wind turbine according to the disclosure,

[0016] Fig. 2 is a block diagram illustrating an exemplary arrangement for activating a safe mode operation of a wind turbine according to the disclosure, and

[0017] Fig. 3 is a block diagram illustrating exemplary processing circuitry.

[0018] DETAILED DESCRIPTION

[0019] Various exemplary embodiments and details are described hereinafter, with reference to the figures when relevant. It should be noted that the figures are only intended to facilitate the description of the embodiments. They are not intended as an exhaustive description of the disclosure or as a limitation on the scope of the disclosure. In addition, an illustrated embodiment needs not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced in any other embodiments even if not so illustrated, or if not so explicitly described.

[0020] The present disclosure provides methods, electronic devices and wind turbines that enable a controlled reaction to situations where a control function does not have the information it relies upon to prevent excessive loads or damages and thereby become incapable of effectively perform its function of regulating a condition of the wind turbine.

[0021] The disclosure provides a method for activating a safe mode operation of a wind turbine. The method comprises providing status signals indicative of statuses and / or states of sensors in a wind turbine during operation. First and second control functions can, respectively, determine first and second fault alerts based on at least one received status signal. Upon determining such fault alert, the first and second control functions can, respectively, provide first and second safe mode requests to a safe mode controller of the wind turbine. The safe mode controller determines, based on the received first and second safe mode requests, a safe mode for the wind turbine. The method may comprise controlling the wind turbine to effectuate the determined safe mode.

[0022] The disclosure also provides an arrangement for activating safe modes in a wind turbine. The arrangement comprises first and second systems regulated by first and second control functions respectively, and being configured to receive status signals indicative of a status and / or a state of at least one sensor of a plurality of sensors in the wind turbine. The first and second systems comprise processing circuitry configured to determine fault alerts based on at least one received status signal and provide first and second safe mode requests if a fault alert is determined. A safe mode controller of the arrangement is configured to receive the first and second safe mode request from the first and second systems, respectively, and the safe mode controller comprises processing circuitry configured to determine a safe mode for the wind turbine based on the received first and second safe mode requests.

[0023] A wind turbine is controlled by means of operational settings that are set to both maximize energy production and protect the turbine under varying environmental conditions. Such operational settings include blade pitch angle, rotor speed, yaw angle, cut-in and cut-out wind speeds, generator torque, power output limit, and many others. Wind turbines also involve a lot of sensors used by different components and systems to control or monitor the wind turbine, including controlling and monitoring the operational settings of the wind turbine.

[0024] In relation to a performance of a sensor, or circuitry or algorithms connected to a sensor, a 'status' of a sensor reflects whether the sensor itself is operational and capable of providing meaningful data, such as the sensor's overall health, connectivity, or role within a system. A status signal indicative of a status of a sensor may thus indicate whether the sensor, or circuitry or algorithms connected to the sensor, is online, offline, not working, not working properly, faulty, saturated, overloaded, etc.

[0025] In relation to a performance of a sensor, or circuitry or algorithms connected to a sensor, a 'state' of a sensor indicates what the sensor is detecting or measuring (its physical or logical output), such as the real-time data or conditions being monitored or detected by the sensor. A status signal indicative of a state of a sensor may thus indicate one or more outputs from the sensor or from circuitry or algorithms connected to the sensor, such output comprising parameter values from the sensor, transformations or modulations of parameter values, outputs being a function of parameter values, control functions using parameter values, etc.

[0026] In relation to a sensor, a parameter is a variable that can be sensed by a sensor, for example the sensor 'thermometer' can sense the parameter 'temperature'. A parameter value is the value of the sensed parameter as determined by the sensor, for example the temperature 14 °C is a parameter value sensed by a thermometer.

[0027] The status and / or state of one sensor, or of circuitry or algorithms connected to that sensor, is often used by different components and systems to control or monitor the wind turbine. Status signals indicative of statuses and / or states of sensors during operation thus serve to provide such different components and systems with the information they need to control or monitor the wind turbine, including controlling and monitoring the operational settings of the wind turbine.

[0028] The first and second control functions are different control functions, and all references to 'a' or 'the' control function is intended to refer to either or both of the first and second or further control functions unless otherwise indicated.

[0029] The term control function is intended to encompass a monitoring function, a regulating function, a supervising function, or a managing function of a system of the wind turbine. In one or more embodiments, a control function controls, monitors, regulates, supervises, or a manages a condition of or in a system of the wind turbine. In one or more embodiments, the condition can be one or more of:

[0030] - a loading condition or a load (such as a mechanical, electrical, or thermal load);

[0031] - a movement, vibration, or oscillation of a wind turbine part (such as a blade or the tower); a moment, such an angular moment, or a torque or a force on a mechanical component;

[0032] Hence, the control function may be a load mitigating control function or a load regulating control function serving to mitigate or regulate loads of the relevant system during operation. In this relation, a 'system' specifies a collection of hardware components, software components, electronic components, and mechanical components that together controls or supervises a section or a role of the wind turbine.

[0033] As an example for illustrative purposes only, a system could be related to the blade pitch and comprise mechanical parts, actuators, sensors and controllers related to the pitch angle of a blade. A control function related to the blade pitch system could be an individual pitch control (IPC) function regulating the condition of aerodynamic load on the blade.

[0034] In exemplary embodiments the first control function regulates a first condition of a first system of the wind turbine, and the second control function regulates a second condition of a second system of the wind turbine.

[0035] To perform its function, a control function relies on status signals indicative of statuses and / or states of sensors during operation of the wind turbine and can determining a fault alert based on at least one status signal.

[0036] In one or more embodiments, a fault alert may be an alert indicating a fault, such as an incapability, an error, or an unexpected or undesired determination in the control function. The fault alert can for example be of a type that indicate whether a particular type of error or malfunction is happening. The fault alert can for example be indicative of a degree, magnitude or extent to which an error or malfunction is occurring.

[0037] The fault alert can be based on, such as selected based on, triggered by, or determined from, the at least one received status signal. In one or more embodiments, the fault alert is based on a comparison with a predetermined range or threshold related to the state of the sensor on which the at least one received status signal is based. Such predetermined range or threshold may for example be a function of a sensed parameter value, such as a boolean true / false operation with an outcome that depends on the state of the sensor. In one or more embodiments, determining a first fault alert comprises determining that a status of a sensor indicated in at least one status signal does not agree with, such as is in conflict or not in correspondence with, a predetermined status or operation of the sensor. In one or more embodiments, determining a first fault alert comprises determining that a state of a sensor indicated in at least one status signal does not agree with, such as is outside of or exceeds, a predetermined range or threshold related to the state of the sensor.

[0038] In one or more embodiments, the fault alert is triggered by the control system determining a condition or a value that does not agree with, such as is outside of or exceeds, a predetermined range or threshold for that condition or value.

[0039] As already mentioned, a control function can regulate a condition of a system of the wind turbine. Such control function can preferably determine a current condition of the system using an algorithm and one or more sensor values. If the determined condition exceeds a threshold, or is about to, the control function can adjust operational settings to keep the condition in an acceptable range to reduce the risk of damages on the turbine. While the control function adjusts operational settings to reduce the risk of damages, a power control system of the wind turbine manages the turbine's operation to optimize or maintain the desired power output under varying wind conditions. This operation management typically involves controlling operational settings (blade pitch, generator torque, nacelle yaw) that are also adjusted by the control function in embodiments of this disclosure. Thus, there is an overall balancing of operational settings between a risk of damage and a power production target. During this overall balancing where different systems and functions participate, the control function relies on input from sensors and sensor units to prevent excessive loads or damages. If one of these sensors or sensor units is not operational or provides outlier values, the control function may not have sufficient information to prevent excessive loads or damages, and it becomes incapable of effectively perform its function of regulating the condition of the system. As a result, the control function can determine a fault alert indicating that there is a risk, such as an undeterminable risk, of damage to the turbine since the control function cannot definitively determine whether the condition exceeds a threshold.

[0040] In exemplary embodiments the first control function regulates a first condition of a first system of the wind, and the second control function regulates a second condition of a second system of the wind turbine. In one or more embodiments the first fault alert is indicative of an incapability of the first control function to regulate the first condition, and the second fault alert is indicative of an incapability of the second control function to regulate the second condition. Preferably, the incapability is an incapability to regulate the condition in accordance with a predetermined range or threshold for that condition.

[0041] If a fault alert is determined, the control function provides a safe mode request to a safe mode controller of the wind turbine. A safe mode request is a request for the wind turbine to enter a safe mode to protect it from damages or overload. A safe mode request may or may not be a request for a specific safe mode or a specific type of safe mode. A safe mode request can be triggered by the mere existence of a fault alert or be determined or selected based on one or more fault alerts determined by the control function.

[0042] A safe mode can be described by setpoints and / or an adjustment of setpoints of operational settings of the wind turbine, the setpoints or adjustment serving to ensure that a recognized error or malfunction will not cause damage or deterioration to the wind turbine. A safe mode typically involves adjustment of operational settings that result in the wind turbine operating with a reduced power output. In an exemplary embodiment, a safe mode may involve one or more of:

[0043] - A dynamic adjustment of one or more operational settings, wherein the determination of the safe mode comprises determining target setpoints of the operational settings as a function of one or more operational parameters, such as a current wind speed, environmental conditions (turbulence), a current operating point (power, rotational speed, pitch angles).

[0044] - An adjustment of one or more operational settings determined from the first and second safe mode requests, such as from the fault alert, such as on the statuses and / or states of sensors. For example, if there is an issue with a particular sensor in the wind turbine, a control function that would normally regulate a condition based on a status signal related to that sensor would not be able to perform such regulation. This could result in a fault alert triggering a safe mode request. As a precaution, the safe mode controller can adjust a setpoint of an operational setting to reduce the condition.

[0045] An adjustment of operational settings to fixed setpoints. For example, a safe mode may control the wind turbine to operate at a maximum of 60% of the rated power. Relative adjustments of operational settings, such as an adjustment resulting in a percentual reduction of current conditions or production.

[0046] The safe mode to be effectuated is determined by a safe mode controller of the wind turbine. The safe mode controller controls, such as determines, selects, or compiles, a safe mode to be effectuated for the wind turbine to protect it from damages. The safe mode controller receives the first and second safe mode requests from the first and second control functions and may be a centralized safe mode controller for the wind turbine.

[0047] If only a single safe mode request is received, the safe mode controller will typically effectuate a safe mode corresponding to the single received safe mode request. However, when more safe mode requests are received in parallel from different control functions, there may not be a definite safe mode to be effectuated. In the method for activating a safe mode operation according to the disclosure, when several safe mode requests are received from different control functions, the safe mode controller will determine, such as select or compile, a safe mode for the wind turbine based on the different requests. The safe mode controller determines the safe mode to be effectuated based on the received first and second safe mode requests, preferably so that the determined safe mode will mitigate or reduce loads on mechanical or electrical components to protect these from damage or overload. In one or more embodiments, the determined safe mode comprises one or more of a derated power; a generator speed reference, such as a generator, rotor, or drivetrain speed; a minimum pitch; and a maximum trust for the wind turbine.

[0048] The safe mode controller preferably takes the first and second safe mode requests from the different first and second control functions into consideration when determining the safe mode, so that the effectuated safe mode will remedy the underlying causes of both the first and second fault alerts. Thus, in one or more embodiments, determining a safe mode based on the received first and second safe mode requests comprises determining setpoints and / or adjustments of setpoints of operational settings of the wind turbine that seeks to remedy both the first fault alert and the second fault alert.

[0049] The safe mode controller may have two or more predetermined safe modes, i.e. different safe modes each defined by a set of predefined setpoints or setpoint adjustments for operational settings of the wind turbine. A predetermined safe mode often represents a worst-case scenario with very low power production and can therefore be an expensive consequence of a fault alert. Faulty or out of range sensor statuses or states may sometimes be remedied by the control system without generating a fault alert, or if there is a fault alert, the safe mode request will allow the safe mode controller to determine a safe mode that is less detrimental to the production than a worst-case scenario safe mode. In one or more embodiments, the first safe mode request comprises target operational settings determined by the first control function, and the safe mode controller will use these together with the second safe mode requests from the second control function to determine a safe mode ensuring maximum production without overload risk. Thereby, the safe mode controller can decide to overrule target operational parameters from the first control function based on target operational parameters from the second control function and vice versa. Similarly, the safe mode controller can decide to overrule target operational settings in the first safe mode request from the first control function based on operational settings from a predetermined safe mode to ensure an acceptable or non-zero production with no overload risk.

[0050] In one or more embodiments, the first and second safe mode request comprise requests for different predetermined safe modes, and wherein the determination of the safe mode comprises determining a safe mode that is a combination of setpoints and / or adjustments of setpoints of operational settings of the wind turbine for the different predefined safe modes. This may comprise selecting the most conservative setpoint(s) and / or adjustment of setpoint(s) of operational settings from the different predefined safe modes, where the most conservative setpoint and / or adjustment is the setpoint and / or adjustment that causes the largest reduction in a condition having a risk of damaging the wind turbine.

[0051] The safe mode, i.e. the target setpoints or adjustments, may depend on current operational conditions of the wind turbine. For example, in low winds, the safe mode may be less conservative than in hard winds, since there is less risk of overloading a component. Hence, in one or more embodiments, the determination of the safe mode comprises determining setpoints and / or adjustments of setpoints of operational settings of the wind turbine as a function of one or more of a current wind speed; current environmental conditions such a turbulence; and a current operating point, such as current power, current rotational speed, or current pitch angles.

[0052] By considering the first and second safe mode request, the safe mode controller may aim at achieving a safe mode wherein the wind turbine can have a maximum production without a risk of overload or damage. In one or more embodiments, the first and second safe mode requests comprise first and second sets of target operational settings, respectively, and determining a safe mode based on the first and second safe mode requests comprises selecting operational settings from the first and second sets of target operational settings that maximise power production. Thereby, the safe mode controller can make a more informed determination than simply selecting between predetermined worst-case safe modes.

[0053] Fig. 1 shows a flow diagram of an exemplary method 100 for activating a safe mode operation of a wind turbine. In one or more embodiments, the exemplary method 100 can be performed by an exemplary arrangement 1 for activating safe modes in a wind turbine as illustrated in Fig. 2. With reference to Fig. 1, the method 100 comprises providing SI 10 status signals indicative of, such as comprising or comprising an indication of, statuses and / or states of sensors in a wind turbine during operation. The status signals may be provided SI 10 by circuitry or algorithms that are connected to the sensors and process the statuses and states from the sensors to provide the indication comprised by the status signal.

[0054] With reference to Fig. 1, the method 100 comprises, by a first control function such as in a first system, determining S122 a first fault alert based on at least one status signal. The determining S122 of a first fault alert may comprise a monitoring of the status signal(s), so that as long as no first fault alert is determined, the step 122 continue monitoring until a determination of a first fault alert is made. This is indicated by the Y / N and the dashed recursive arrow. The first fault alert is determined S122 based on at least one status signal, such as on a status or a state of a sensor as indicated in the at least one status signal. In one or more embodiments, such first control function regulates a first condition of a first system of the wind turbine. Hence, the first fault alert may further be based on the regulation of the condition, such as a magnitude of the condition. Upon determining a first fault alert, a first safe mode request is provided S126 to a safe mode controller of the wind turbine. The first safe mode request will typically be triggered by the first fault alert.

[0055] Similarly, also with reference to Fig. 1, the method 100 comprises, by a second control function such as in a second system, determining S122 a second fault alert based on at least one status signal. The determining S132 of a second fault alert may comprise a monitoring of the status signal(s), so that as long as no second fault alert is determined, the step 132 continue monitoring until a determination of a second fault alert is made. This is indicated by the Y / N and the dashed recursive arrow. The second fault alert is determined S132 based on at least one status signal, such as on a status or a state of a sensor as indicated in the at least one status signal. In one or more embodiments, such second control function regulates a second condition of a second system of the wind turbine. Hence, the second fault alert may further be based on the regulation of the condition, such as a magnitude of the condition. Upon determining a second fault alert, a second safe mode request is provided S136 to a safe mode controller of the wind turbine. The second safe mode request will typically be triggered by the second fault alert.

[0056] The first and second safe mode request are received by a safe mode controller, which determine S150 a safe mode for the wind turbine based on the received first and second safe mode requests. The safe mode controller or a wind turbine controller may then control S156 the wind turbine to effectuate the determined safe mode by controlling or providing control signals to actuators of the wind turbine.

[0057] Fig. 2 is a block diagram of an exemplary arrangement 1 for activating safe modes in a wind turbine. The arrangement is configured to perform any of the methods or method steps disclosed in and described in relation to Fig. 1. The different parts or blocks of arrangement 1 are collectively described as 'elements' of arrangement 1. The arrangement 1 comprises a first system 22 regulated by a first control function and configured to receive status signals indicative of a status and / or a state of at least one sensor of a plurality of sensors 12, 14 in the wind turbine. As indicated by the dotted blocks, the wind turbine may comprise a plurality of sensors 10, each being connected equivalently to sensors 12 and 14. References to sensors 10 are intended to refer to any one or more of sensor 12, sensor 14, and further equivalent sensors. The first system 22 comprises processing circuitry 24 configured to determine a first fault alert based on at least one received status signal and provide a first safe mode request.

[0058] Similarly, the arrangement 1 comprises a second system 32 regulated by a second control function and configured to receive status signals indicative of a status and / or a state of at least one sensor of a plurality of sensors 12, 14 in the wind turbine. The second system 32 comprises processing circuitry 34 configured to determine a second fault alert based on at least one status signal and provide a second safe mode request. As indicated by the dotted blocks, the arrangement 1 may comprise a plurality of systems 20, each being equivalent to systems 22 and 32. References to systems 20 are intended to refer to any one or more of first system 22, second system 32, and further equivalent systems.

[0059] With reference to Fig. 2, the arrangement 1 comprises a safe mode controller 50 configured to receive first and second safe mode request from the first and second systems 22 and 32, respectively. The safe mode controller 50 comprises processing circuitry 54 configured to determine a safe mode for the wind turbine based on the received first and second safe mode requests.

[0060] With reference to Fig. 2, the status signals may be provided to systems 20 wirelessly or via wired connections from sensors 10, where the connectors in the block diagram does not indicate that all systems 20 must be connected to all sensors 10. The status signals may be provided by or via a sensor unit 18 that makes sensor statuses and states available to different systems of the wind turbine, where sensor unit 18 be provided by several sub-units each connected only to one or a set of sensors. In one or more embodiments, the arrangement 1 comprises one or more sensor units 18 comprising circuitry or algorithms for processing statuses and states of sensors 10 to provide the indications comprised by the status signals. Similarly, in one or more embodiments, a status signal comprises an indication provided by circuitry or algorithms connected to the sensor and processing the status and / or state of the sensor.

[0061] With reference to Fig. 2, the wind turbine can comprise several electrical and mechanical actuators 40 used to control the operational settings of the wind turbine. Systems 20 are preferably connected to one or more actuators 40 so that the control function of the system can regulate a condition by controlling or sending control signals to actuators 40. Similarly, safe mode controller 50 can be connected to one or more actuators 40 so that the safe mode controller can effectuate a determined safe mode by controlling or sending control signals to actuators 40.

[0062] In the following, different exemplary embodiments of both method 100 and arrangement 1 are described. An embodiment such as a method step described in relation to the method 100 is also disclosed as an embodiment of the arrangement 1 in as so far it can be performed by an element of the arrangement 1. Similarly, an embodiment, such as a functionality of an element, of the arrangement 1 is also disclosed as an embodiment of the method 100 in as so far it can be a step of the method 100. Wind turbine involves several systems that together control and monitor the wind turbine, where a system can be a collection of one or more of hardware components, software components, electronic components, and mechanical components that together controls or supervises part of the wind turbine. In one or more embodiments, the first and second control functions are different control functions selected from:

[0063] • an individual pitch control (IPC) function. Exemplary IPC control functions can be a controller of the tilt moment and / or yaw moment of the main bearing and / or rotor axle, asymmetric rotor load mitigating function.

[0064] • an adaptive wind turbine load control function. Exemplary adaptive wind turbine load control functions can monitor a transient wind induced load and reduce the power and / or speed setpoint to reduce the load.

[0065] • a tower movement control function. Exemplary tower movement control functions can be fore-aft tower damper or side-side tower damper.

[0066] • an edge-wise blade vibration control function. Exemplary edge-wise blade vibration control functions can be a pitch supervision controller...

[0067] As described previously, determining S122, S132 a fault alert can comprise determining a risk of damage to the wind turbine, typically due to a condition exceeding a threshold value or several conditions together putting the wind turbine in a state with increased risk of damage. In accordance with the disclosure, control functions and systems can determine such risk of damage based on at least one status signal. In one or more embodiments, determining S122, S132 a first and / or second fault alert based on at least one status signal comprises determining that a status of a sensor 10 indicated in the at least one status signal does not agree with a predetermined status or operation of the sensor 10. In one or more embodiments, determining S122, S132 a first and / or a second fault alert based on at least one status signal comprises determining that a state, such as a sensed parameter value, of a sensor 10 indicated in the at least one status signal is outside a predetermined range or threshold related to the state of the sensor 10.

[0068] The control functions and systems can, in addition to status signals, also determine risk of damage to the wind turbine based on other factors or results. In embodiments where a control function regulates a condition of a system, the fault alert may further be based on results from the process of regulating the condition. For example, a control function may use an algorithm that under normal conditions determines whether a blade load exceeds a threshold load, so that the system can regulate the load on the blade before it exceeds a maximum load for the blade. If the algorithm misses important information, such as sensor statuses or states, or if the outputs are nonconclusive in relation to the current load, the control function may be unable to determine a potential overload, which may cause it to determine a fault alert. Hence, in one or more embodiments, the first fault alert is indicative of an incapability of the first control function to regulate the first condition. Also, in one or more embodiments, the second fault alert is indicative of an incapability of the second control function to regulate the second condition.

[0069] With reference to Fig. 2, systems 20 can be connected to one or more actuators 40 for the control function of the system to regulate a condition by controlling or sending control signals to actuators 40. In case of a faulty actuator 40 or an actuator not being able to perform its actuation, for example in case of a movable part being broken or jammed, the control function will be incapable of regulating the condition. Such incapability to properly operate actuator 40 can be determined by the system 20 in different ways, such as:

[0070] - A sensor 10 is positioned on the actuator or the part it actuates, so that the sensor state is indicative of the actuation.

[0071] - The actuator 40 comprises control circuitry that control or detects the actuation operation so that the control circuitry is de facto a state of a sensor 10. Thus, in one or more embodiments, a sensor 10 is provided by control circuitry of an actuator that detects whether an actuation is performed by the actuator.

[0072] - Upon receiving a control signal from a system 20, the actuator returns a confirmation signal that the intended actuation is or will be performed. Such a confirmation signal or the lack thereof is de facto a status of a sensor 10. Thus, in one or more embodiments, a sensor is provided by an actuator 40 that, upon receiving a control signal from a system 20 to perform an actuation, sends a confirmation signal to the system.

[0073] Hence, in one or more embodiments, a status signal is indicative of an actuator being incapable of regulating an operational setting related to a condition, and a fault alert is indicative of an incapability of the system or control function to regulate the condition. When a safe mode is activated, it will typically be reported to surveillance centers, service centers, customers, etc. so that these are informed that attention is required for the turbine to continue its normal operation. In such cases, it is helpful if a diagnosis or an indication of the underlying fault, faulty system, component, or sensor is provided. For that reason, it may be preferred that information and indications can be advanced through the elements of the arrangement 1 so that the safe mode controller can provide an output comprising such information and / or indications when determining a safe mode. This advancing of information and / or indications may in part be performed by the control functions. Thus, in one or more embodiments of method 100 and with reference to Fig. 1, providing S126 the first safe mode request comprises determining S124 the first safe mode request, such as determining whether to encompass one or more of the following or indications thereof in the first safe mode request: a) the first fault alert; b) a status signal on which a) is based; c) a status or state of a sensor indicated by b); and d) the sensor of c).

[0074] Similarly, in one or more embodiments, providing S136 the second safe mode request comprises determining S134 the second safe mode request, such as determining whether to encompass one or more of the following or indications thereof in the second safe mode request:

[0075] 1) the second fault alert;

[0076] 2) a status signal on which 1) is based;

[0077] 3) a status or state of a sensor indicated by 2); and

[0078] 4) the sensor of 3).

[0079] Similarly, upon determining S150 or effectuating S156 the determined safe mode, the safe mode controller can provide any indications a) - d) and 1) - 4) comprised by the first and second safe mode requests to a user or a supervision function, such as to a surveillance center, a service center, a customer, etc.

[0080] Fig. 3 is a block diagram illustrating exemplary processing circuitry 300, such as processing circuitry of a sensor unit or subunit 18, processing circuitry 24 of the first system 22, processing circuitry 34 of the second system 32, and processing circuitry 54 of the safe mode controller 50. The processing circuitry 300 is optionally configured to perform any of the steps and operations disclosed relation to in Figs. 1 and 2. The processing circuitries 18, 24, 34, and 54 may be provided by one or several shared processing circuitries 300.

[0081] With reference to Fig. 3, the exemplary processing circuitry 300 comprises a processor 302 such as a Central Processing Unit (CPU), a memory circuitry 304 such as a flash memory, a hard drive, a random-access memory (RAM), etc., and an interface 306 such as a wired or wireless interface connected to a network 308. The operations of processing circuitry 300 may be embodied in the form of executable logic routines (e.g., lines of code, software programs, etc.) that are stored by memory circuitry 304 and executed by processor 302. Data used and produced by the processing circuitry 300 may be exchanged with other processing units and servers on network 308 via interface 306.

[0082] It should further be noted that any reference signs do not limit the scope of the claims, that the exemplary embodiments may be implemented at least in part by means of both hardware and software, and that several "means", "units" or "devices" may be represented by the same item of hardware.

[0083] The various exemplary methods, devices, nodes, and systems described herein are described in the general context of method steps or processes, which may be implemented in one aspect by a computer program product, embodied in a computer- readable medium, including computer-executable instructions, such as program code, executed by computers in networked environments. A computer-readable medium may include removable and non-removable storage devices including, but not limited to, Read Only Memory (ROM), Random Access Memory (RAM), compact discs (CDs), digital versatile discs (DVD), etc. Generally, program circuitries may include routines, programs, objects, components, data structures, etc. that perform specified tasks or implement specific abstract data types. Computer-executable instructions, associated data structures, and program circuitries represent examples of program code for executing steps of the methods disclosed herein. The sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps or processes.

[0084] Although features have been shown and described, it will be understood that they are not intended to limit the claimed disclosure, and it will be made obvious to those skilled in the art that various changes and modifications may be made without departing from the scope of the claimed disclosure. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense. The claimed disclosure is intended to cover all alternatives, modifications, and equivalents.

Claims

CLAIMS1. A method for activating a safe mode operation of a wind turbine, the method comprising the steps of:- providing status signals indicative of statuses and / or states of sensors in a wind turbine during operation;- in a first control function: o determining a first fault alert based on at least one status signal; and o upon determining the first fault alert, providing, by the first control function, a first safe mode request to a safe mode controller of the wind turbine;- in a second control function: o determining a second fault alert based on at least one status signal; o upon determining the second fault alert, providing, by the second control function, a second safe mode request to the safe mode controller of the wind turbine;- upon receiving the first and second safe mode request, determining, by the safe mode controller and based on the received first and second safe mode requests, a safe mode for the wind turbine; and- controlling the wind turbine to effectuate the determined safe mode.

2. The method according to claim 1, wherein:- the first control function regulates a first condition of a first system of the wind turbine; and- the second control function regulates a second condition of a second system of the wind turbine.

3. The method according to claim 2, wherein:- the first fault alert is indicative of an incapability of the first control function to regulate the first condition; and- the second fault alert is indicative of an incapability of the second control function to regulate the second condition.

4. The method according to any of the preceding claims, wherein determining a safe mode based on the received first and second safe mode requests comprises determining setpoints and / or adjustments of setpoints of operational settings of the wind turbine that seeks to remedy both the first fault alert and the second fault alert.

5. The method according to any of the preceding claims, wherein the first and second safe mode request comprise requests for different predetermined safe modes, and wherein the determination of the safe mode comprises determining a safe mode that is a combination of setpoints and / or adjustments of setpoints of operational settings of the wind turbine for the different predefined safe modes.

6. The method according to claim 5, the method comprising, for each setpoint and / or adjustment of setpoint of an operational setting of the wind turbine, selecting the most conservative setpoint and / or adjustment of setpoint from the different predefined safe modes.

7. The method according to any of the preceding claims, wherein the determination of the safe mode comprises determining setpoints and / or adjustments of setpoints of operational settings of the wind turbine as a function of one or more of a current wind speed, environmental conditions, and a current operating point.

8. The method according to any of the preceding claims, wherein the first safe mode request comprises indications of one or more of the following: a) the first fault alert;b) a status signal on which a) is based; c) a status or state of a sensor indicated by b); and d) the sensor of c); and wherein the second safe mode request comprises indications of one or more of the following:1) the second fault alert;2) a status signal on which 1) is based;3) a status or state of a sensor indicated by 2); and4) the sensor of 3).

9. The method according to claim 8, the method comprising, upon activating the determined safe mode, providing the indications a) - d) and 1) - 4) comprised by the first and second safe mode requests, respectively, to a user or a supervision function.

10. The method according to any of the preceding claims, wherein determining a first and / or a second fault alert comprises determining that a status of a sensor indicated in at least one status signal does not agree with a predetermined status or operation of the sensor.

11. The method according to any of the preceding claims, wherein determining a first and / or a second fault alert comprises determining that a state of a sensor indicated in at least one status signal is outside a predetermined range or threshold related to the state of the sensor.

12. The method according to any of the preceding claims, wherein the determined safe mode comprises one or more of:- a de-rated power;- a generator speed reference;- a minimum pitch; and- a maximum trust for the wind turbine.

13. The method according to any of the preceding claims, wherein the first and second control functions are different control functions selected from:• an individual pitch control (IPC) control function;• an adaptive wind turbine load control function;• a tower movement control function; and• an edge-wise blade vibration control function.

14. An arrangement (1) for activating safe modes in a wind turbine, the arrangement comprising: a first system (22) regulated by a first control function and configured to receive status signals indicative of a status and / or a state of at least one sensor of a plurality of sensors (10, 12, 14) in the wind turbine, the first system comprising processing circuitry (24) configured to determine a first fault alert based on at least one status signal and provide a first safe mode request; a second system (32) regulated by a second control function and configured to receive status signals indicative of a status and / or a state of at least one sensor of a plurality of sensors (10, 12, 14) in the wind turbine, the second system comprising processing circuitry (34) configured to determine a second fault alert based on at least one status signal and provide a second safe mode request; and a safe mode controller (50) configured to receive first and second safe mode request from the first and second systems, respectively, the safe mode controller comprising processing circuitry (54) configured to determine a safe mode for the wind turbine based on the received first and second safe mode requests.

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