WO2020216424A1

WO2020216424A1 - Controller and method for a wind turbine

Info

Publication number: WO2020216424A1
Application number: PCT/DK2020/050109
Authority: WO
Inventors: Joe CUOGHI; Stephen BUGGY
Original assignee: Vestas Wind Systems A/S
Priority date: 2019-04-26
Filing date: 2020-04-23
Publication date: 2020-10-29

Abstract

The invention provides a controller and method for an ice detection system of a wind turbine for determining whether to halt operation of the wind turbine. The controller 5 receives values of different parameters to be used to determine whether ice is present at the wind turbine, wherein for each parameter first and second parameter values from respective first and second parameter sensors are received. The controller determines whether, for each of the parameters, the first and second parameter values are valid. The controller determines an expected output power of the wind turbine based on at least one 10 of the parameters, and an actual output power of the wind turbine based on at least one of the parameters. The controller determines a power difference between the expected output power and the actual output power. The controller disables the wind turbine when it is determined that operation of the wind turbine is to be halted, which is to be determined based on whether the sensor output data is valid and whether the power difference is 15 greater than a threshold power difference value.

Description

CONTROLLER AND METHOD FOR A WIND TURBINE

FIELD OF THE INVENTION

The present invention relates to a controller for a wind turbine and in particular, but not exclusively, to a controller for determining the presence of ice at the wind turbine. Aspects of the invention relate to a controller, to a method, and to a wind turbine.

BACKGROUND

Wind turbines are normally provided with a rotor in the form of a rotatable hub carrying a set of wind turbine blades. The wind acts on the wind turbine blades, thereby causing the hub to rotate. The rotational movements of the hub are transferred to a generator, either via a gear arrangement or directly, in the case that the wind turbine is of so-called direct drive type. In the generator, electrical energy is generated, which may be supplied to a power grid.

It is common for wind farms including a number of wind turbines to be situated in geographical locations in which atmospheric temperatures often drop below freezing. Such a‘cold climate’ increases the risk of ice forming on the components of a wind turbine, in particular on the rotor blades of the wind turbine. This can not only reduce the efficiency of the wind turbine, but the risk of ice being thrown from the rotor blades as they rotate increases. This poses a risk to animals or humans in the vicinity of the wind turbine, and the risk of other damage caused by‘ice throw’ also increases. For these reasons, it is necessary for wind turbines to have systems for detecting the presence of ice at the wind turbine and, if a positive determination is made, to disable operation of the wind turbine. Furthermore, wind turbines have one or more active systems for removing ice from the wind turbine rotor blades or other components in the event that ice is detected. Only once the ice has been removed may the wind turbine be permitted to resume operation.

Systems for detecting the presence of ice at a wind turbine may be regarded as being ‘safety-related’ systems as they contribute to reducing risk as outlined above. One or more industry standards outline the required performance level of such safety-related systems such that they may be determined to be demonstrably ‘safe’. The performance level achieved by a particular system may depend on the system hardware/architecture, the reliability of the system components, and/or the effectiveness of the error detection by the system.

One or more current system for detecting ice may not be demonstrably‘safe’ according to one or more of the standards. For example, the accuracy of current systems and methods may be heavily subject to the accuracy and/or reliability of the collected data on which the presence of ice determination is based.

It is an aim of the present invention to address one or more of the disadvantages of current systems and methods described above.

SUMMARY OF THE INVENTION

According to an aspect of the invention there is provided a controller for a system, for example an ice detection system, of a wind turbine. The controller is for determining an indication as to whether operation of the wind turbine is to be halted. Halting operation of the wind turbine can mean disabling or stopping operation of the wind turbine. Halting operation may mean that the wind turbine enters a safe mode or idle mode. Entering a safe mode may in turn mean that operation of the wind turbine is disabled.

The controller comprises an input configured to receive sensor output data indicative of values of a plurality of different parameters to be used to determine whether ice is present at the wind turbine. For each parameter the sensor output data may comprise first and second parameter values from respective first and second parameter sensors.

The controller comprises a processor configured to determine whether, for each of the plurality of parameters, the sensor output data is valid based on the respective first and second parameter values. The processor is configured to determine an expected output power of the wind turbine based on the received sensor output data for at least one of the plurality of parameters. The expected output power may be determined with reference to a reference power curve associated with the wind turbine. The processor is configured to determine an actual output power of the wind turbine based on the received sensor output data for at least one of the plurality of parameters. The processor is configured to determine a power difference between the expected output power and the actual output power. The controller comprises an output configured to send a control signal to disable the wind turbine when it is determined that operation of the wind turbine is to be halted.

The processor is configured to determine whether operation of the wind turbine is to be halted based on whether the sensor output data is valid and whether the power difference is greater than a threshold power difference value.

The present invention is advantageous in that a check or determination as to whether the sensor output data being provided by the various sensors is valid is performed, and only if the sensor output data is valid is a determination as to the presence of ice at the wind turbine made on the basis of the received sensor output data. This means that the resulting determination as to the presence of ice has improved accuracy compared with prior known systems.

The invention allows for a check as to the validity of the sensor output data by providing two or more sensors for measuring data associated with each of the plurality of parameters. The measured data collected by the two or more sensors for each parameter may be checked to ensure that the data is consistent and/or the same, thereby providing a degree of certainty as to the accuracy of the sensor output data.

It is necessary for operation of a wind turbine to be halted in the event that ice is detected. If the measured data on which the ice detection determination is based is not accurate, then the risk of an incorrect determination of ice detection increases. In particular, this may pose a serious risk to, for example animals in the vicinity of the wind turbine or on-site service personnel, in the event that an incorrect determination is made when there is in fact ice present.

The control signal may include a signal to activate first and second actuators to halt operation of the wind turbine. In embodiments, the first and second actuators may both be actuated to perform the same function, i.e. to effect stopping of the wind turbine. In embodiments, the first actuator effects stopping of the wind turbine and the second actuator is utilised only if there is a fault with the first actuator. In this way, a degree of redundancy is provided whereby failure of one of actuators does not cause failure of the entire ice detection system, which reduces a risk that the wind turbine operation cannot be stopped in the event of ice being present. In particular, a single fault in one of the actuators does not lead to a loss of function of the entire ice detection system, which may be a required performance level of certain industry standards. As there is a potential risk to life associated with‘ice throw’ from a wind turbine rotor blade then the standard needed to show that a system is demonstrably‘safe’ according to certain standards may be relatively high.

The architecture of the ice detection system and, in particular, the operation of the controller therein, of the present invention leads to a safety-related control system with a level of redundancy that reduces a level of risk associated with failure of one or more components of the system. In particular, the system is provided with an architecture that minimises risk for many or all eventualities or failures, or improves the reliability of the ice detection system to demonstrably‘safe’ levels.

The first and second actuators may be pitch pilot valves or emergency pitch valves. Advantageously, use of such actuators may enable operation of the wind turbine to be disabled more quickly.

In some embodiments, when the sensor output data is determined to be not valid for at least one of the plurality of parameters the processor is configured to determine that operation of the wind turbine is to be halted. If the accuracy of the measured data cannot be verified, i.e. the sensor output data is determined to be invalid, then any ice detection determination based on such data cannot be relied upon. As a safety precaution, therefore, the operation of the wind turbine may be stopped until the fault or anomaly in the sensor output data can be fixed. Again, this reduces the risk that an incorrect ice detection determination is made, which is particularly important for safety reasons if ice is indeed present at the wind turbine. As such, no single fault associated with sensors or data measurements in the ice detection system will lead to an increased safety risk as operation of the wind turbine is stopped.

In some embodiments, when the sensor output data is determined to be valid for each of the plurality of parameters the processor may be configured to determine that ice is present at the wind turbine and that operation of the wind turbine is to be halted when and the power difference is greater than a threshold power difference value. In such embodiments, the processor may be configured to determine that ice is not present at the wind turbine when the power difference is less than the threshold power difference value. Advantageously, operation of the wind turbine may be permitted to commence or continue if the measured data is deemed to be valid in addition to a determination of no ice based on said data.

In some embodiments, the plurality of parameters may include an ambient temperature in the vicinity of the wind turbine. In such embodiments, when the sensor output data is determined to be valid for each of the plurality of parameters the processor may be configured to determine that ice is not present at the wind turbine when the ambient temperature is greater than a threshold ambient temperature value. In these embodiments, the processor may be configured to determine that when the ambient temperature is less than the threshold ambient temperature value, ice is present at the wind turbine and that operation of the wind turbine is to be halted when and the power difference is greater than a threshold power difference value. In such embodiments, the processor may be configured to determine that ice is not present at the wind turbine when the power difference is less than the threshold power difference value. Advantageously, by basing the determination on measured ambient temperature data in addition to power output data, then there is increased confidence in the accuracy of the determination as to whether ice is present.

In some embodiments, when the sensor output data is determined to be not valid for only the ambient temperature, the processor may be configured to determine whether operation of the wind turbine is to be halted based only on whether the power difference is greater than the threshold power difference value. Advantageously, this guards against failure of a temperature sensor causing unnecessary halting of the operation of the wind turbine during summer months when ice is unlikely to be present.

The processor may be configured to determine that the sensor output data is not valid if no sensor output data is received for at least one of the plurality of parameters.

The processor may be configured to determine a redundancy difference between the first and second parameter values for each of the plurality of parameters. The processor may be configured to determine that the sensor output data is not valid when the redundancy difference for at least one of the plurality of parameters is greater than the respective redundancy difference threshold value.

The first and second parameter sensors for each of the plurality of parameters may be two-channel sensors. The plurality of parameters may include an output power of the wind turbine. The sensor output data may comprise first and second output power values from respective first and second output power sensors. The processor may be configured to determine the actual output power based on the first and second output power values.

The plurality of parameters may include an output current and an output voltage of the wind turbine. The sensor output data may comprise first and second output current values from respective first and second output current sensors. The sensor output data comprises first and second output voltage values from respective first and second output voltage sensors. The processor may be configured to determine the actual output power based on the first and second output current values and the first and second output voltage values. Advantageously, the use of a plurality or current signals and a plurality of voltage signals is a relatively simple way to determine output power, and introduces greater design flexibility into the system. Furthermore, the use of such a plurality of signals introduces more redundancy into the system.

The plurality of parameters may include a wind speed at the wind turbine. The sensor output data may comprise first and second wind speed values from respective first and second wind speed sensors. The processor may be configured to determine the expected output power based on the first and second wind speed values. Advantageously, as a wind speed sensor is often used in prior ice detection systems, then the use of wind speed sensors in the present invention may be readily achievable in that current systems may readily be modified.

The plurality of parameters may include a rotation speed and a pitch of the wind turbine. The sensor output data may comprise first and second rotation speed values from respective first and second rotation speed sensors. The sensor output data may comprise first and second pitch values from respective first and second pitch sensors. The processor may be configured to determine the expected output power based on the first and second rotation speed values and the first and second pitch values. Advantageously, the sensor output data from rotation speed sensors and pitch sensors on many current wind turbines is already demonstrably‘safe’, i.e. the data or signals exist in the correct format, which may provide for simpler development of the present invention by modification of current systems. According to another aspect of the invention there is provided a system, for example an ice detection system, for a wind turbine. The system is for determining an indication as to whether operation of the wind turbine is to be halted. The system comprises first and second parameter sensors for each of a plurality of different parameters to be used to determine whether ice is present at the wind turbine, the first and second parameter sensors being configured to measure data indicative of the respective parameters.

The system comprises a controller having an input configured to receive sensor output data indicative of values of the plurality of different parameters. For each parameter the sensor output data comprises first and second parameter values from respective first and second parameter sensors.

The controller comprises a processor configured to determine whether, for each of the plurality of parameters, the sensor output data is valid based on the respective first and second parameter values. The processor is configured to determine an expected output power of the wind turbine based on the received sensor output data for at least one of the plurality of parameters. The processor is configured to determine an actual output power of the wind turbine based on the received sensor output data for at least one of the plurality of parameters. The processor is configured to determine a power difference between the expected output power and the actual output power.

The controller comprises an output configured to send a control signal to activate first and second actuators to disable the wind turbine when it is determined that operation of the wind turbine is to be halted.

The system may comprise the first and second actuators.

The first and second actuators may be pitch pilot valves.

For one or more of the plurality of parameters the first and second parameter sensors of the system may be two-channel sensors. For one or more of the plurality of parameters the first and second parameter sensors of the system may be separate sensors. According to another aspect of the invention there is provided a wind turbine comprising a controller or a system as described above. According to another aspect of the invention there is provided a method for an ice detection system of a wind turbine for determining an indication as to whether operation of the wind turbine is to be halted. The method comprises receiving sensor output data indicative of values of a plurality of different parameters to be used to determine whether ice is present at the wind turbine. For each parameter the sensor output data comprises first and second parameter values from respective first and second parameter sensors. The method comprises determining whether, for each of the plurality of parameters, the sensor output data is valid based on the respective first and second parameter values. The method comprises determining an expected output power of the wind turbine based on the received sensor output data for at least one of the plurality of parameters. The method comprises determining an actual output power of the wind turbine based on the received sensor output data for at least one of the plurality of parameters. The method comprises determining a power difference between the expected output power and the actual output power. The method comprises determining whether operation of the wind turbine is to be halted based on whether the sensor output data is valid and whether the power difference is greater than a threshold power difference value. The method comprises sending a control signal to disable the wind turbine when it is determined that operation of the wind turbine is to be halted.

According to another aspect of the invention there is provided a non-transitory computer- readable storage medium storing instructions thereon that when executed by one or more electronic processors causes the one or more electronic processors to carry out the method described above.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 is a schematic diagram illustrating a front view of a wind turbine having a system including a controller according to an aspect of the invention; Figure 2 is a schematic diagram of the system and controller of Figure 1 according to one embodiment;

Figure 3 shows the steps of a method undertaken by the system and controller of Figure 2; and,

Figure 4 is a schematic diagram of the system and controller of Figure 1 according to another embodiment.

DETAILED DESCRIPTION

Figure 1 shows a wind turbine arrangement 10, or simply a wind turbine, according to an embodiment of the invention. The arrangement 10 includes a tower 12, a nacelle 14 rotatably coupled to the top of the tower 12 by a yaw system, a rotor including a rotor hub 16 mounted to the nacelle 14, a plurality of wind turbine rotor blades 18 coupled to the rotor hub 16, and a control system 20 including a controller according to an embodiment of an aspect of the invention. The system 20 is described in greater detail below. The nacelle 14 and rotor blades 18 are turned and directed into the wind direction by the yaw system. The nacelle 14 houses generating components (not shown) of the wind turbine, including the generator, gearbox, drivetrain and brake assembly, as well as convertor equipment for converting the kinetic energy of the wind into electrical energy for provision to the grid. The wind turbine is shown in its fully-installed form suitable for operation; in particular, the rotor 16 is mounted on the nacelle 14 and each of the blades 18 are mounted on the rotor and rotor hub 16.

Figure 2 shows a schematic view of the system 20. In the described embodiment, the system 20 is an ice detection system for determining an indication as to whether ice is present at the wind turbine 10, for example if ice is formed on one or more of the rotor blades 18. The system 20 includes a plurality of sensors 22, a controller 24, and a plurality of actuators 26.

The plurality of sensors 22 includes first and second output power sensors 30a, 30b. Each of the output power sensors 30a, 30b is configured to measure values of the generated output power of the wind turbine 10 during operation of the wind turbine 10. The plurality of sensors 22 also includes first and second wind speed sensors 32a, 32b. Each of the wind speed sensors 32a, 32b is configured to measure values of the wind speed in the vicinity of the wind turbine 10. The wind speed sensors 32a, 32b may be in the form of force-torque sensors. Typically, wind speed sensors are mounted atop the nacelle 14 of the wind turbine 10, and are in the form of anemometers. Anemometers come in various different types, for example cup, vane, hot-wire, laser-Doppler and ultrasonic anemometers. Ultrasonic sensors may be preferred on wind turbines that are difficult to access, for example off-shore, as they do not need recalibration. In particular, ultrasonic sensors measure wind speed based on a time-of-flight of sonic pulses between pairs of transducers. The plurality of sensors 22 also includes first and second temperature sensors 38a, 38b. Each of the temperature sensors 38a, 38b is configured to measure values of the ambient temperature in the vicinity of the wind turbine 10. The temperature sensors 38a, 38b may for example be mounted to the nacelle 14 of the wind turbine 10. In a different example, temperature sensors may be located elsewhere in the wind park comprising the wind turbine 10, and the ambient temperature for all of the wind turbines in the wind park may be based on the data measured by the temperature sensors.

The controller 24 includes an input 40, a processor 42 and an output 44. The input 40 is configured to receive sensor output data from the sensors 22, and the processor 42 is configured to make a determination as to whether ice is present at the wind turbine 10, for example whether there is ice on the rotor blades 18. The output 44 is configured to send a control signal to the actuators 26 in dependence on the determination that is made by the processor 42. The controller 24 additionally comprises a memory device 46, such as a non-transitory, computer-readable medium storing instructions thereon that when executed by the processor 42 causes the processor 42 to carry out a method as described below.

In the described embodiment, the actuators 26 are controlled to disable or stop operation of the wind turbine 10. In particular, the actuators 26 are for controlling the pitch or pitch angle of the rotor blades 18. Specifically, in the described embodiment the pitch of the rotor blades 18 is controlled hydraulically. Each of the blades 18 has a hydraulic pitch system including one or more hydraulic cylinders each including a pitch piston movable therein to adjust the pitch, and an accumulator hydraulically connected to the cylinders so as to pressurise them.

In the described embodiment the actuators 26 include first and second emergency or pilot pitch valves 50a, 50b. The actuators 26 may instead include needle valves, solenoid valves, ball valves, or any other suitable type of valve. Activation of either of the first and second pilot pitch valves 50a, 50b causes a release of pressure in the hydraulic pitch system by draining the accumulator until the pressure in the pitch system reaches a desired level. Such drainage causes the pitch of the blades 18 to be adjusted to their feathering positions.

Figure 3 shows the steps of a method 60 undertaken by the controller 24 to make a determination as to whether operation of the wind turbine 10 should be stopped or paused. In particular, operation of the wind turbine 10 should be stopped if the data measured by the sensors 22 is deemed not to be valid, or if said data ice is valid and it is determined that ice is present at the wind turbine 10.

At step 62, the input 40 receives sensor output data from the sensors 22. As mentioned above, the plurality of sensors 22 includes two output power sensors 30a, 30b and two wind speed sensors 32a, 32b. There is two of each type of sensor in order that the measured data received from the sensors may be validated. The particular setup or layout of the sensors 22 and the particular manner in which the measured data is validated may vary. For example, the first and second output power sensors 30a, 30b may in fact be a sensor having two channels 30a, 30b. In this case a check is made to ensure that the received signal by each of the channels 30a, 30b is the same so as to validate the measured data. In particular, both of the channels 30a, 30b need to receive a signal in order for the sensor output data of the two-channel sensor 30a, 30b to be deemed valid and to be received by the controller 24. If one of the first and second channels 30a, 30b does not receive a signal then the sensor output data is deemed to be not valid. This may mean that the sensor output data is not sent to the controller 24 or the determination of invalid data may be made by the controller 24. The data validation check may additionally, or alternatively, include a comparison of measured values by the two-channel output power sensor 30a, 30b, for example to ensure that the measured values are consistent such as being within a predetermined validity or redundancy threshold. In addition to checking that the signals are within a predetermined threshold of each other, checks that the signals are not outside of predetermined maximum and/or minimum threshold values may also be undertaken. Similarly, the wind speed sensors 32a, 32b may be two-channel sensors.

At step 64 the processor 42 of the controller 24 makes a determination as to whether the sensor output data is valid. This may be done in a number of ways, for example as described above. For instance, if sensor output data is not received by the controller 24 from one or more of the sensors 22 then this may be determined that the data measured by said sensors 22 is not valid. Alternatively, the processor 42 may undertake a comparison of measured values between first and second ones or channels of a particular type of sensor 22 to check for consistency, as mentioned above.

If at step 64 the processor 42 determines that the data is not valid then it is determined that a fault is present in the system 20. In this case, at step 65 the controller 24 is configured to send a fault control signal from the output 44 to command the wind turbine to enter a safe mode. For example, this may include halting, disabling, pausing or stopping operation of the wind turbine 10. In particular, as described above this may include commanding the actuators 26 to adjust the pitch of the rotor blades 18 to their feathering positions.

If, however, at step 64 the processor 42 determines that the sensor output data is valid then the processor 42 proceeds to make the determination as to whether ice is present at the wind turbine 10 based on said received sensor output data. In particular, at step 66 the processor 42 determines whether the ambient temperature in the vicinity of the wind turbine 10, as measured by the temperature sensors 38a, 38b, is greater than or less than a prescribed threshold ambient temperature value. The threshold ambient temperature value may be a value above which it is unlikely, or not possible, for ice to form and be present at the wind turbine 10. For example, the threshold ambient temperature may be approximately 0 degrees Celsius; however, any suitable threshold ambient temperature may be used.

If at step 66 the processor 42 determines that the ambient temperature as measured by the temperature sensors 38a, 38b is above the threshold temperature then the processor 42 determines at step 67 that no ice is present at the wind turbine 10.

If, however, at step 66 the processor 42 determines that the ambient temperature is less than the threshold temperature threshold then it is deemed that it is possible that ice may be present at the wind turbine 10. The processor 42 then makes a determination as to whether ice is present based on the power output of the wind turbine 10. In particular, the determination is made with reference to a reference power curve of the wind turbine 10. Specifically, the sensor output data from the wind speed sensors 32a, 32b is used at step 68 to determine an expected power to be generated by the wind turbine 10. That is, with reference to the power curve of the wind turbine 10 the power that may be expected to be generated by the wind turbine 10 in normal operating conditions, i.e. no ice present, for the measured wind speed is determined.

At step 70 the processor 42 determines the actual power being generated by the wind turbine 10 based on the sensor output data received from the output power sensors 30a, 30b. It is known that the presence of ice at a wind turbine in cold climate conditions, e.g. freezing conditions, can have a severe impact on the performance of a wind turbine, in particular the power generated by the wind turbine is lower than may be expected in normal operating conditions.

As such, at step 72 determines the difference between the determined expected and actual output power values based on the received sensor output data. The processor 42 compares this power difference to a predetermined threshold difference at step 74. If the difference between the expected and actual output powers is less than the predetermined power threshold value then it is determined at step 76 that no ice is present at the wind turbine 10 as the wind turbine 10 is operating close enough to what may be expected in normal operating conditions. In such a case, the wind turbine 10 is allowed to continue to operate as normal.

If, however, the difference between the expected and actual output powers is greater than the predetermined power threshold value, i.e. the expected output power deviates from the actual output power by a greater amount than would be expected in normal operating conditions, then it is determined at step 78 that ice is present at the wind turbine 10. That is, the presence of ice is determined to be the reason that the wind turbine 10 is not generating the amount of power that may be expected in normal conditions for the given wind conditions. Therefore, at step 78 the controller 24 sends a control signal from the output 44 to the actuators 26 to halt operation of the wind turbine 10 as described above.

The reference power curve of the wind turbine 10 is based on the output power of the turbine for a given wind speed and may built up over several months, e.g. three to six months, during which the turbine operates normally, i.e. when there is no ice such as during summer months. Note that the comparison of the expected and actual output powers may be based on instantaneous measurements or, more commonly, may be based on a rolling average relative output power, i.e. a curve of the measured or actual output power versus the reference power curve for a given wind speed. The rolling average may be taken over a set period of time, for example a ninety-minute interval of data. Note that in step 64 of the method 60, all of the sensor output data in the rolling average interval may need to be deemed to be valid to avoid the wind turbine 10 being paced into safe mode or idle mode. Similarly, at step 74 the output power difference may need to be greater than the output power threshold for the entire rolling average interval for a determination of ice being present to be made.

Note that in addition to halting the wind turbine 10, when ice is determined to be present at step 78 then the controller 24 is operable to send a signal to one or more active systems of the wind turbine 10 to remove ice from one or more components of the turbine 10, e.g. the rotor blades 18. Indeed, operation of the wind turbine may be halted until a subsequent determination of‘no ice’ is made by the system 20.

Figure 4 shows a schematic view of an ice detection system 120 of the wind turbine 10 in an embodiment different to that of Figure 2. Many of the features in the system 120 are the same as in the system 20, and like features in Figure 4 have the same reference numerals as in Figure 2. The system 120 has a plurality of sensors 122. Like the sensors 22, the plurality of sensors 122 has first and second output power sensors 30a, 30b and first and second ambient temperature sensors 38a, 38b. Unlike the sensors 22, however, the plurality of sensors 122 has first and second rotation speed sensors 134a, 134b for measuring respective first and second rotation speeds of the rotor 16 of the wind turbine 10, and first and second pitch sensors 136a, 136b, for measuring respective first and second pitch angles of the rotor blades 18. The rotation speed and pitch sensors 134a, 134b, 136a, 136b in the Figure 4 embodiment are used instead of the wind speed sensors 32a, 32b in the Figure 2 embodiment. The system 120 of the presently-described embodiment undertakes a method similar to that of the method 60 of Figure 3. In the presently-described embodiment, however, the expected output power of the wind turbine is determined based on the sensor output data from the rotation speed and pitch sensors 134a, 134b, 136a, 136b (rather than wind speed sensors).

Many modifications may be made to the above-described embodiments without departing from the scope of the present invention as defined in the accompanying claims.

In the above-described embodiments, the actual power output of the wind turbine 10 is based on a measured power output from the power output sensors 30a, 30b. In different embodiments, the wind turbine may alternatively or additionally make use of different sensors in order to determine the actual power output of the wind turbine. For example, the wind turbine may include two or more output current sensors and two or more output voltage sensors, and the actual power output of the wind turbine may be based on the measurements of the output current and output voltage from these sensors.

In the above-described embodiments, two-channel sensors provide sensor output data to the controller; however, sensors having more than two channels may be provided as part of the system and may provide sensor output data to the controller. As an alternative to the two-channel sensors two or more of each type of sensor may be provided. The measured data may then be validated by comparing the values measured by the two or more of each sensor, for example by ensuring the measured values are within a predetermined validity threshold.

In the above-described embodiment, operation of the wind turbine is disabled by direct control of actuators in the form of pilot pitch valves. In different embodiments, however, control of the pilot pitch valves may instead be made via a pitch control system of the wind turbine.

In the above-described embodiment, the processor determines that ice is present when the difference between the actual power output and the expected power output rises above a threshold power difference values. Note that this is equivalent to the actual power output falling below a threshold power value. For example, when the expected power output is determined (based on the measured wind speed) then a threshold power value a prescribed amount below this expected power output is set. If the actual power output is less than the threshold power value then ice is determined to be present.

In the above-described embodiment, a determination is made as to the validity of the data measured by each of the pairs of sensors. In particular, if the data from any pair of sensors is deemed to be not valid then the wind turbine is controlled to enter a safe mode, i.e. operation of the wind turbine is disabled. In different embodiments, however, even if the received ambient temperature data is deemed to be not valid then the wind turbine is not automatically controlled to enter the safe mode. Instead, the determination as to whether ice is present may be made solely on the basis of the difference between the expected and actual power outputs.

Claims

1. A controller (24) for an ice detection system (20) of a wind turbine (10), the controller (24) being for determining an indication as to whether operation of the wind turbine (10) is to be halted, the controller (24) comprising: an input (40) configured to receive sensor output data indicative of values of a plurality of different parameters to be used to determine whether ice is present at the wind turbine (10), wherein for each parameter the sensor output data comprises first and second parameter values from respective first and second parameter sensors (22); a processor (42) configured to determine:

whether, for each of the plurality of parameters, the sensor output data is valid based on the respective first and second parameter values;

an expected output power of the wind turbine (10) based on the received sensor output data for at least one of the plurality of parameters;

an actual output power of the wind turbine (10) based on the received sensor output data for at least one of the plurality of parameters; and,

a power difference between the expected output power and the actual output power; and, an output (44) configured to send a control signal to disable the wind turbine (10) when it is determined that operation of the wind turbine (10) is to be halted, wherein the processor (42) is configured to determine whether operation of the wind turbine (10) is to be halted based on whether the sensor output data is valid and whether the power difference is greater than a threshold power difference value.

2. A controller (24) according to Claim 1 , wherein the control signal includes a signal to activate first and second actuators (26) to halt operation of the wind turbine (10).

3. A controller (24) according to Claim 2, wherein the first and second actuators (26) are pitch pilot valves (50a, 50b).

4. A controller (24) according to any previous claim, wherein when the sensor output data is determined to be not valid for at least one of the plurality of parameters the processor (42) is configured to determine that operation of the wind turbine (10) is to be halted.

5. A controller (24) according to any previous claim, wherein when the sensor output data is determined to be valid for each of the plurality of parameters the processor (42) is configured to determine that:

ice is present at the wind turbine (10) and that operation of the wind turbine (10) is to be halted when the power difference is greater than a threshold power difference value; and,

ice is not present at the wind turbine (10) when the power difference is less than the threshold power difference value.

6. A controller (24) according to any of Claims 1 to 4, wherein the plurality of parameters includes an ambient temperature in the vicinity of the wind turbine (10), and wherein when the sensor output data is determined to be valid for each of the plurality of parameters: the processor (42) is configured to determine that ice is not present at the wind turbine (10) when the ambient temperature is greater than a threshold ambient temperature value; and,

when the ambient temperature is less than the threshold ambient temperature value, the processor (42) is configured to determine that ice is present at the wind turbine (10) and that operation of the wind turbine (10) is to be halted when and the power difference is greater than a threshold power difference value, and the processor (42) is configured to determine that ice is not present at the wind turbine (10) when the power difference is less than the threshold power difference value.

7. A controller (24) according to Claim 5 or Claim 6, wherein when the sensor output data is determined to be not valid for only the ambient temperature, the processor (42) is configured to determine whether operation of the wind turbine (10) is to be halted based only on whether the power difference is greater than the threshold power difference value.

8. A controller (24) according to any previous claim, the processor (42) being configured to:

determine a redundancy difference between the first and second parameter values for each of the plurality of parameters; and, determine that the sensor output data is not valid when the redundancy difference for at least one of the plurality of parameters is greater than the respective redundancy difference threshold value.

9. A controller (24) according to any previous claim, wherein the first and second parameter sensors (22) for each of the plurality of parameters are two-channel sensors.

10. A controller (24) according to any previous claim, wherein:

the plurality of parameters includes an output power of the wind turbine (10); the sensor output data comprises first and second output power values from respective first and second output power sensors (30a, 30b); and,

the processor (42) is configured to determine the actual output power based on the first and second output power values.

11. A controller (24) according to any previous claim, wherein:

the plurality of parameters includes an output current and an output voltage of the wind turbine (10);

the sensor output data comprises first and second output current values from respective first and second output current sensors;

the sensor output data comprises first and second output voltage values from respective first and second output voltage sensors; and,

the processor (42) is configured to determine the actual output power based on the first and second output current values and the first and second output voltage values.

12. A controller (24) according to any previous claim, wherein:

the plurality of parameters includes a wind speed at the wind turbine (10);

the sensor output data comprises first and second wind speed values from respective first and second wind speed sensors (32a, 32b); and,

the processor (42) is configured to determine the expected output power based on the first and second wind speed values.

13. A controller (24) according to any previous claim, wherein:

the plurality of parameters includes a rotation speed and a pitch of the wind turbine

(10);

the sensor output data comprises first and second rotation speed values from respective first and second rotation speed sensors (134a, 134b); the sensor output data comprises first and second pitch values from respective first and second pitch sensors (136a, 136b); and,

the processor (42) is configured to determine the expected output power based on the first and second rotation speed values and the first and second pitch values.

14. A wind turbine (10) comprising a controller (24) according to any previous claim.

15. A method (60) for an ice detection system (20) of a wind turbine (10) for determining an indication as to whether operation of the wind turbine (10) is to be halted, the method (60) comprising: receiving sensor output data indicative of values of a plurality of different parameters to be used to determine whether ice is present at the wind turbine (10), wherein for each parameter the sensor output data comprises first and second parameter values from respective first and second parameter sensors (22); determining whether, for each of the plurality of parameters, the sensor output data is valid based on the respective first and second parameter values; determining an expected output power of the wind turbine (10) based on the received sensor output data for at least one of the plurality of parameters; determining an actual output power of the wind turbine (10) based on the received sensor output data for at least one of the plurality of parameters; determining a power difference between the expected output power and the actual output power; determining whether operation of the wind turbine (10) is to be halted based on whether the sensor output data is valid and whether the power difference is greater than a threshold power difference value; and, sending a control signal to disable the wind turbine (10) when it is determined that operation of the wind turbine (10) is to be halted.