WO2020069975A1 - Method and system for operating a wind turbine - Google Patents

Abstract

The invention relates to a method and a system for operating a wind turbine, which has at least one rotor blade, comprising the following work steps: detecting sensor signals, which are suitable for characterizing a blade load, particularly an impact flexural moment, on the at least one rotor blade; determining a blade load, particularly a value of the blade load, on the basis of the sensor signals detected and a calibration function; and controlling the wind turbine, particularly an adjustment angle of the one rotor blade, on the basis of the blade load determined, wherein the calibration function is adjusted by means of calibration processes on the basis of the blade load determined, wherein more recent calibration processes are weighted higher than older calibration processes in order to adjust the calibration function. The weighting is preferably applied as a function of a predefined time constant, which preferably defines a predefined time period.

Description

 Method and system for operating a wind turbine

The invention relates to a method for operating a wind energy installation which has at least one rotor blade, sensor signals which are suitable for characterizing a blade load on the at least one rotor blade being detected, and determining a blade load on the basis of the detected sensor signals and a calibration function is, and the wind turbine, in particular an angle of incidence of the at least one rotor blade, is controlled on the basis of the determined blade load.

In the case of control strategies for minimizing loads on a wind energy installation, in particular a control of an adjustment angle of the rotor blades is used. The rotor blades are preferably individually rotated (pitched) during the revolution so that a total mechanical load that is introduced via a rotor hub, a rotor shaft and a gondola onto a tower of the wind energy installation can be minimized. In this case, an individual pitch control is referred to (individual pitch control).

It is particularly advantageous here if an individual blade load, in particular a blade bending moment, can be provided for control purposes for each rotor blade. In this case, we speak of a rotor blade feedback control (blade feedback control).

In general, sensors for measuring blade loads cannot be attached exactly to the place where, according to theoretical considerations, they should be attached. Furthermore, sensors can change their properties over time, so that calibration of the sensors is necessary.

In order to carry out load measurements, strain sensors, for example fiber Bragg grating sensors or strain gauges, are usually used, which are connected in such a way that only bending strains, but not normal forces due to temperature expansion or centrifugal forces, are taken into account. The sensors are usually calibrated statically against the gravitational bending moment from the known mass and the known center of gravity of the distance of the Rotor blade from the measuring point with the rotor blade in a horizontal position. To determine a possible offset of the sensors for measuring the blade bending moments, the rotor blade is preferably placed vertically. The impact bending moment of the rotor blade, which is essentially perpendicular to a reference plane of the rotor blade, or the swivel bending moment, which is essentially parallel to a reference plane of the rotor blade, can be addressed by rotating the blade setting angle by 90 °.

The publication WO 2008/014935 A2 relates to a method for calibrating at least one sensor of a wind energy installation, the wind energy installation having at least one movable component, the component being pivoted or rotated about a predeterminable axis and a measurement value detected by the at least one sensor , which is a measure of the load on the component, is evaluated.

DE 102 19 664 A1 relates to a wind power plant with a tower, one in the region of the top of the tower, preferably on a machine nacelle rotatably mounted with respect to an axis of rotation essentially running in the direction of gravity, one rotatably mounted with respect to an essentially horizontal rotor axis and at least one with respect to one A rotor having a rotor blade that projects essentially radially from the rotor axis, a sensor device assigned to the rotor for generating sensor signals as a function of the mechanical load on the rotor, and an evaluation device receiving the sensor signals, in particular data processing device, at least one, preferably each, The rotor blade of the rotor is assigned at least two sensor elements, preferably mounted in pairs, and the evaluation device for determining evaluation signals representing the mechanical loads on at least one rotor blade on the basis of the previous is designed in the sensor signals generated for this rotor blade associated with sensor elements.

It is an object of the invention to improve a calibration of a control system of a wind turbine. This task is solved by the independent claims. Advantageous refinements are claimed in the subclaims.

A first aspect of the invention relates to a method for operating a wind power plant which has at least one rotor blade, comprising the following working steps:

Detection of sensor signals which are suitable for characterizing a blade load, in particular an impact bending moment, on the at least one rotor blade; Determining a sheet load, in particular a value of the sheet load, on the basis of the detected sensor signals and a calibration function; and

 Control of the wind energy installation, in particular an adjustment angle of the one rotor blade, on the basis of the determined blade load, the calibration function being adapted by means of calibration processes on the basis of the determined blade load, whereby to calibrate the calibration function, younger calibration processes are weighted higher than older calibration processes. The weighting preferably takes place as a function of a predefined time constant, which preferably defines a predefined time period.

A second aspect of the invention relates to a method for operating a wind energy installation which has at least one rotor blade, comprising the following working steps:

Detection of sensor signals which are suitable for characterizing a blade load, in particular an impact bending moment, on the at least one rotor blade;

 Determining a sheet load, in particular a value of the sheet load, on the basis of the detected sensor signals and a calibration function; and

 Controlling the wind energy installation, in particular an adjustment angle of the at least one rotor blade, on the basis of the determined blade load;

wherein the calibration function is adapted by means of calibration processes on the basis of the determined sheet load, wherein for the adaptation of the calibration function a predefined number of calibration processes depending on a predefined time constant, which preferably defines a predefined time segment, are taken into account, preferably an older calibration process, in particular a oldest calibration process is no longer taken into account as soon as a younger calibration process, in particular a youngest calibration process, is taken into account.

The blade load is preferably a bending moment, in particular an impact bending moment. The methods according to the invention are further preferably carried out in a computer-assisted manner.

 Accordingly, in a third aspect, the invention relates to a system for operating a wind energy installation which has at least one rotor blade, comprising:

 An interface set up for detecting sensor signals which are suitable for characterizing a blade load, in particular an impact bending moment, on the at least one rotor blade;

Evaluation means, set up for determining a sheet load on the basis of the detected sensor signals and a calibration function, further set up for adaptation. the calibration function is calibrated on the basis of the determined sheet load, with younger calibration processes being weighted higher than older calibration processes and / or with a predefined number of calibration processes or calibration processes as a function of a predefined time constant, which is preferably a predefined one Time period defined, are taken into account, wherein preferably an older calibration process, in particular an oldest calibration process, is no longer taken into account, as soon as a younger calibration process, in particular a youngest calibration process, is taken into account; and

 Control means for controlling the wind turbine, in particular an angle of inclination, at least one rotor blade, based on the determined blade load.

Further aspects of the invention relate to a computer program, a computer-readable medium and a wind turbine.

The features and advantages explained below in relation to the method according to the invention according to the first and second aspect of the invention also apply accordingly to the other aspects of the invention.

A setting angle in the sense of the invention is preferably an angle, measured about a longitudinal axis of the rotor blade, between a reference plane of a rotor blade and a rotor plane swept by the longitudinal axis of the rotor blade when the rotor rotates, which plane is preferably perpendicular to the rotor axis or, in the case of rotors with a cone angle, represents a conical surface area. The setting angle is preferably defined as 0 ° when the rotor blade is in the operating position, ie. H. in operation with an optimal high-speed number that delivers the maximum power on the rotor shaft. As an alternative or in addition, the setting angle can also be defined as an angle between a rotor blade chord, which preferably extends at least substantially from a rotor blade leading edge to a rotor blade trailing edge, on a predefined profile cut of the rotor blade and the above-mentioned rotor plane or conical outer surface.

An impact bending moment in the sense of the invention preferably occurs perpendicular to the reference plane of the rotor blade. This is preferably perpendicular to the rotor plane when the setting angle of the rotor blade is 0 °.

Controlling a wind power plant in the sense of the present invention is preferably specifying setpoints of operating parameters of the wind power plant itself. the rotor in the spin mode, in which the rotor blades are preferably in a flag position, or in the production mode.

 A calibration function in the sense of the invention is preferably an assignment rule between sensor signals or blade loads as input variables and an adjusted blade load as output variable.

A gain in the sense of the invention is preferably a proportional part of a calibration function.

A means in the sense of the present invention can be embodied in terms of hardware and / or software technology, in particular a data processing or signal processing unit, in particular a digital processing unit, in particular a microprocessor unit (CPU), preferably connected to a memory and / or bus system. and / or have one or more programs or program modules. The CPU can be designed to process commands that are implemented as a program stored in a memory system, to acquire input signals from a data bus and / or to output signals to a data bus. A storage system can have one or more, in particular different, storage media, in particular optical, magnetic, solid-state and / or other non-volatile media. The program can be designed in such a way that it embodies or is capable of executing the methods described here, so that the CPU can execute the steps of such methods and thus in particular can control and / or monitor a wind energy installation.

A time constant in the sense of the invention preferably characterizes a characteristic time period or decay time. The time constant can preferably also be specified as a time period.

The invention is based in particular on the approach of an adaptive calibration for measurements of the blade load on a sensor on a rotor blade. The calibration is carried out here while the wind turbine is subject to a continuous control process.

Sensor signals which are recorded according to the invention are suitable for characterizing a blade load, in particular an impact bending moment, on the at least one rotor blade. According to the invention, in particular the same sensor signals, on the basis of which the wind power installation is controlled, are used in addition to calibrating a calibration function used in relation to the sensors used for the measurement. On the basis of this calibration function, the sensor signals and / or the blade loads determined on the basis of the sensor signals are corrected.

 In order not to make individual measured values of the sensors, which are far from the usual received sensor measurements, so-called individual outliers, the basis for the control of the wind power plant, the calibration function is not adapted according to the invention by means of individual measurements and / or the blade loads determined thereon, but rather a number of measurements are taken into account in order to adapt the calibration function. In particular, a plurality of calibration processes are used for this. A calibration process in the sense of the invention is preferably based on determining a deviation of the sheet loading determined on the basis of measurements from a target sheet loading. By taking into account a plurality of measured values or a plurality of calibration processes, in particular a predefined number or a number depending on a predefined time constant, which preferably defines a predefined time period, the influence of individual measurements or calibration processes on the calibration function is reduced. As a result, a statistically high-quality adjustment of the calibration function is achieved.

In addition, according to the invention, younger measured values or calibration processes are preferably weighted higher than older measured values or calibration processes. Younger calibration processes are the most recently performed calibration processes. The most recent calibration process is therefore the last calibration process carried out. Alternatively or additionally, according to the invention, after a new measured value has been measured or a new calibration process has been carried out and this measured value or calibration process is taken into account for adapting the calibration function, an older measured value or calibration process, in particular the oldest calibration process, is no longer taken into account .

The higher weighting of recent measured values or calibration processes and the rejection of older calibration processes ensures that the adaptation responds to the latest changes to the sensors or the rotor blades, which necessitate a post-calibration. Older measurement values or calibration processes are still taken into account here in order to reduce interference effects caused by the so-called individual outliers. A permanent deviation of the blade loads determined from the sensor signals, which makes a post-calibration necessary, is however taken into account by the gradually increasing influence of the younger measured values or calibration processes. In an advantageous embodiment of the method according to the invention, the calibration function is continuously adapted during operation of the wind turbine. Such an adaptation, which also takes place in particular during the operation of the wind energy installation, stands in contrast to calibration methods in which the wind energy installation has to be brought into a predefined stationary position. In particular, constant post-calibration is possible in this way.

In a further advantageous embodiment of the method according to the invention, the calibration function is only adapted if predefined criteria, in particular with regard to the operating conditions or an operating state of the wind energy installation, are met. Operating conditions are preferably environmental parameters such as wind speed, wind direction, time of day etc. By considering criteria as boundary conditions it can be ensured that only those measured values or calibration processes are taken into account when adapting the calibration function that are highly meaningful in relation to have systematic errors in the measurement by sensors. Preferably, only those periods are taken into account during which the predefined criteria are met.

 In a further advantageous embodiment, the methods according to the invention further comprise the work step:

 Determining at least one correction parameter of the calibration function, in particular an offset and / or gain, on the basis of the determined sheet load. The correction parameters are preferably determined in a calibration process and the correction parameter used in each case for adapting the calibration function is calculated on the basis of a plurality of calibration processes.

Accordingly, in an advantageous embodiment of the system according to the invention, the evaluation means is set up to determine at least one correction parameter for the calibration function on the basis of the determined sheet load.

In a further advantageous embodiment of the method according to the invention, the time constant after a restart of the wind energy installation, in particular after a new installation or a component replacement, is smaller, in particular 10 to 75% of the time constant during operation. Due to the smaller time constant after a restart, fewer measured values or calibration processes are used to adapt the correction function. inspects so that the adjustment process can take place faster. Since the wind turbine is equipped with a default correction function or the correction parameter is started with default values (preferably 0 for offset, 1 for gain), the relatively quick first-time adaptation to the real conditions is particularly important. After a first adjustment of the calibration function after the new installation of the wind energy installation or after the component replacement, the change is preferably made to the predefined time constant during operation. The time period after which the changeover is preferably 1 to 10 times the time constant.

In a further advantageous embodiment of the method according to the invention, the calibration processes are weighted in such a way that new calibration processes bring about an adaptation of the calibration function which does not exceed a predetermined difference in relation to a change in a value of the calibration function. In this way, a smoothed behavior can be achieved when controlling the wind energy installation.

In a further advantageous embodiment of the method according to the invention, the weighting is carried out in such a way that an adaptation of the calibration function beyond the predetermined difference requires a large number of calibration processes, in particular at least one third of the calibration processes taken into account for the adaptation. This also results in a particularly smooth control behavior of the wind power installation. In particular, jumps in the setpoint specification for the setting parameters of the wind turbine can be avoided in this way. One such setting parameter is, for example, the individual setting angle for a respective rotor blade.

In a further advantageous embodiment of the method according to the invention, a delay function, in particular a function of a PT1 element, is mapped when the calibration processes are taken into account.

A PT1 element in the sense of the invention is preferably a transfer function with proportional transfer behavior with a first-order delay. The time response of a PT1 element with respect to an input value over time is preferably an exponential function. A weighting A of the calibration processes is therefore initially K and gradually decreases over time, the longer the calibration processes have occurred. This course can be described mathematically by the following relationship:

A (t) = K · e ^{_t T}

K indicates the initial value, T is a predefined time constant of the PT1 element. The last value taken into account, i.e. the most recent value is t = 0. The weighting of the values decreases the older the values are.

The use of a delay function brings about a particularly advantageous smoothing of the control behavior of the wind energy installation.

In a further advantageous embodiment, the methods according to the invention, in which the correction parameters are an offset and / or a gain, furthermore have the following working steps:

 Determining an offset value of the calibration function for the at least one rotor blade, wherein only values of the blade load within a predefined angular sector a about the upper rotational position of the rotor blade, in particular approximately 3 °> a> -3 °, are taken into account; and or

 Determination of a gain value of the calibration function of the at least one rotor blade, with only values of the blade load which meet a boundary condition with respect to a predefined time constant, which preferably defines a predefined time period, which is preferably at least half a revolution, preferably one whole or two revolutions corresponding to the rotor are taken into account; and

wherein the calibration function is adjusted using the determined values.

In an upper rotational position in the sense of the invention, a rotor blade points vertically upwards. According to the invention, this upper rotational position corresponds approximately to a = 0 °.

In addition, other parameters, in particular a torque, are preferably taken into account when determining the gain value.

By taking into account values in the area of the upper rotational position of the rotor blade, influences by a tilt and cone angle of the rotor blades can largely be compensated because these angles act in opposite directions in the upper position and thus cancel each other out, so that essentially only an influence of the dead weight of the rotor blade has to be taken into account as an influencing variable on the sensor when determining the offset value.

By taking at least half a revolution of a rotor into account when determining the gain value, relatively long periods of time are taken into account, which enable a particularly good statistical averaging of short-term operating point deviations.

The correction parameters are preferably calibrated at least once, in particular after a new installation of the wind energy installation or after an exchange of components, by means of a static calibration, in which the individual rotor blades have to be brought into predefined positions. Such a method is known, for example, from document WO 2008/014935 A2 mentioned at the outset.

 In a further advantageous embodiment of the method according to the invention, the calibration function is sensor-specific. Separate calibration functions are preferably provided for each individual sensor device on the rotor blades, by means of which the individual measurement errors of the individual sensors are corrected. This enables a particularly exact calibration of the control of the entire wind turbine.

In a further advantageous embodiment of the method according to the invention, in order to determine the at least one correction parameter, in particular the gain value, a sheet load determined on the basis of the sensor signals is compared with an expected value of the sheet load which is taken from a database with empirical or simulated data or by means of a simulation is provided.

In a further advantageous embodiment, the methods according to the invention furthermore have the following work steps, the at least one correction parameter being a gain:

 Aligning the gain value with a predefined limit value L, in particular 0.85 <L <1.15, preferably 0.92 <L <1.08, particularly preferably 0.94 <L <1.06; and

Output of a status message, in particular a warning message or an error message, when the gain value reaches and / or exceeds or falls below the respectively predefined limit value. If the gain value exceeds a predefined limit, this is an indication indicates that there is a significant fault on the sensor or the respective rotor blade. In this case, for example, individual sensors may have become detached or the rotor blade may be damaged. The output of a status message to a user initializes a check of the wind turbine by the user.

Accordingly, in an advantageous embodiment of the system according to the invention, the evaluation means is set up to compare the gain value with a predefined limit value L and to output a status message when the gain value reaches and / or exceeds or falls below the respectively predefined limit value .

In a further advantageous embodiment of the method according to the invention, the at least one correction parameter is an offset and the offset value is determined in a spin mode of the wind turbine, preferably at a true wind speed of less than approximately 4.5 m / s. The offset value is preferably also only determined if the rotor speed is less than a predefined limit speed, in particular approximately 2.5 rpm or 25% of the nominal speed. More preferably, the offset value is only determined when an angle of incidence of the rotor blade is greater than a predefined limit angle, preferably> approximately 55 °, more preferably> approximately 69 °. Even more preferably, the offset value is only determined when an outside temperature T> about 3 °. The individual measures ensure that the values recorded for the calibration take place at relatively low loads on the rotor blade. In particular, the system is in spin mode during the determination of the offset value and is not iced up.

By filtering the measurements that are used to determine the offset, depending on the weather conditions, only a few relevant measurements are obtained over a longer period of time. A time counter is therefore preferably provided which only takes into account those time periods for the calibration processes during which relevant measurements occur. Calibration times are correspondingly long, in particular if large time constants are provided, ie a relatively large number of calibration processes are taken into account for adapting the calibration function.

In a further advantageous embodiment of the method according to the invention, the at least one correction parameter is a gain and the gain value is determined in a predefined interval of the wind speed v, preferably approximately 7.5 m / s>v> 5.5 m / s. The gain value is preferably determined after a predefined interval the rotor speed N, preferably approximately 98% of the nominal speed or approximately 9.5 rpm>N> 6.7 rpm or approximately 70% of the nominal speed. The gain value is further preferably determined in a predefined interval of the rotor torque M _Rot , preferably approximately a range of approximately 2% of the nominal torque, for example in a range between 30% of the nominal torque and 60% of the nominal torque. In a preferred embodiment, about 44% of the nominal torque + -1% or about 1250 kNm> M _red > 1200 kNm. The gain value is further preferably determined in a predefined interval of the impact bending moment M, preferably between approximately 40% and 70% of the nominal impact bending moment, that is to say the average impact bending moment when the nominal output is reached, with only a comparatively small one for calibrating the gain Interval in the range mentioned is permitted, for example between about 65 and 65.5% of the nominal impact bending moment. Also preferably when an outside temperature T> is about 3 ° C. The predefined criteria with regard to the measurements used to determine the gain value can ensure that the sheet load is in an area with very reproducible results. In particular, in this area there are no dependencies on other state variables, such as air density, or they are negligible. When determining the gain value, the speed is preferably in the range of the optimal high-speed number.

In a further advantageous refinement of the method according to the invention, the rotor has at least two rotor blades and the control comprises determining an individual setpoint angle value for each rotor blade, a setpoint angle of each rotor blade being set on the basis of this individual setpoint angle value.

Further advantages and features result from the exemplary embodiments which are described with reference to the figures. Here at least partially shows schematically:

1 shows a wind energy installation with a system for operating the wind energy installation; and

FIG. 2 shows a method for operating the wind energy installation according to FIG. 1.

1 shows a wind energy installation 1 with a tower 6, on which a tower head in the form of a machine nacelle 5 is attached. The machine nacelle 5 is rotated vertically axis A can be rotated in order to be able to track the respective wind direction WR, indicated by an arrow.

A rotor 2 is rotatably mounted on the machine nacelle 5 about a rotor axis R. This rotor has three rotor blades 3a, 3b, 3c, by means of which a rotor hub 4 is set in rotation when the wind acts. The rotor 2 is preferably coupled via a gear (not shown) to a generator device (not shown) in order to generate electrical energy.

The rotor blades 3a, 3b, 3c can each be pivoted about a longitudinal axis E of the rotor blade, the degree of pivoting being indicated by an angle of incidence.

The wind energy installation 1 also has a system 10 for operating the wind energy installation with a plurality of components, shown in FIG. 1 by the curly bracket.

The system 10 preferably has a position detection device 20 for detecting the rotational position of the rotor blades 3a, 3b, 3c. The position detection device 20 can preferably also detect the setting angle of the rotor blades 3a, 3b, 3c about the longitudinal axis E of the rotor blade.

The system 10 also preferably has sensor devices 40a, 40b, which are each arranged on one of the rotor blades 3a, 3b, 3c, in order to detect the blade load on the respective rotor blade 3a, 3b, 3c.

Position signals with position data P (not shown in FIG. 1) of the position detection device 20 and sensor signals S (not shown in FIG. 1) with sensor data are recorded in the system 10 and passed on by means of an interface 30 and to an evaluation means 50.

This evaluation means 50 is set up to determine blade loads M (all not shown in FIG. 1) on the rotor blades 3a, 3b, 3c on the basis of the position signals P, the sensor signals S and further reference data R. A control means 60 of the system 10 is set up to set the wind energy installation 1, in particular the setting angle of the rotor blades 3a, 3b, 3c about the respective longitudinal axis E of the rotor blades, on the basis of the determined blade load M of the rotor blades 3a, 3b, 3c. In this way, safe, wear- and / or yield-optimized operation of the wind energy installation 1 is guaranteed.

A method 100 carried out by the system 10 according to the invention for operating the wind energy installation 1 is shown in FIG. 2 by means of a block diagram. Accordingly, the system 10 has means or modules, in particular the evaluation means 50, which are implemented and set up in terms of hardware or software in order to carry out such a method 100 in a computer-implemented manner.

 A process for controlling the wind energy installation 1 preferably comprises three basic work steps on the basis of the blade load M of the rotor blades 3a, 3b, 3c.

In a first work step 101, sensor signals S of the sensor devices 40a, 40b are detected. These sensor signals S characterize a blade load M present on the rotor blades 3a, 3b, 3c, in particular an impact bending moment. The impact bending moments M on the rotor blades 3a, 3b, 3c are determined on the basis of these sensor signals S by means of an assignment rule in a second work step 102. Finally, the setting angle, in particular target values of the setting angle, of the rotor blades 3a, 3b, 3c are determined individually on the basis of the impact bending moments M determined in each case and any further control parameters of the wind energy installation 1 in a third work step 103.

In order to ensure reliable and exact control of the setting angle of the rotor blades 3a, 3b, 3c, it is advantageous to adapt the assignment rule between the sensor signals S and the impact bending moments M to be determined to the actual circumstances.

Therefore, the assignment rule between the sensor signals S as an input variable and the blade load M as an output variable contains calibration terms, which according to the invention are generally referred to as a calibration function. These calibration terms allow sensor detuning and tolerances and specific properties of the respective rotor blades 3a, 3b, 3c to be taken into account. The calibration terms preferably have correction parameters KP. In the case of a linear calibration term, these calibration parameters KP are an offset parameter or offset which is used for zero-point calibration, and a so-called gain parameter or gain, which serves as a correction factor for compensating for first-order errors.

 A function for determining a sheet bending moment M, in particular the impact bending moment, preferably has the following form:

M (S) = offset + gain · m · S, where m is a conversion factor from the sensor signals S to the blade load M. In the case of an optimal system without the need for calibration, the offset would be 0 and the gain 1.

Furthermore, further correction parameters KP can be provided, which are used to correct higher-order errors.

 The calibration functions are preferably individually adapted for each rotor blade 3a, 3b, 3c or for each sensor device 40a, 40b which is attached to the rotor blades 3a, 3b, 3c. These calibration functions preferably correct the value of the sheet load M determined on the basis of a measurement. Alternatively, the calibration function can also be used to correct the sensor signals S obtained directly from the sensor devices 40a, 40b.

The calibration function is preferably continuously recalibrated, i.e. H. the correction parameters KP are continuously determined 104a, 104b on the basis of the sensor signals recorded for controlling the wind energy installation. This is particularly advantageous since the sensor devices 40a, 40b can change their properties over time (sensor drift). It is also possible for the rotor blades 3a, 3b, 3c or even a device for adjusting the setting angle of the rotor blades 3a, 3b, 3c to be damaged, so that a re-calibration of the wind energy installation 1 is necessary.

The value of the correction parameters KP is preferably determined on the basis of the position signal P of the rotor blades 3a, 3b, 3c, in particular their rotational position and their respective setting angle, and reference data R and the measured impact bending moment M 104a; 104b. In order to determine the correction parameters KP, a deviation of a value of the impact bending moment M, which was determined on the basis of an assignment rule with currently valid correction terms, and a target value of the impact bending moment M is calculated. The target value is determined from reference data R in each case. The correction parameters KP are then set such that a such a deviation or several such deviations is as small as possible or even no longer exists.

The reference data R can preferably be determined from measurements relating to the impact bending moment M in predefined operating conditions of the wind energy installation. These predefined operating parameters serve as boundary conditions and are preferably different in the case of the correction parameters KP offset and gain. For the offset, the rotor speed (spin state), the setting angle, the rotary position of the rotor blade 3a, 3b, 3c as well as the temperature and the wind speed are decisive as predefined operating conditions. The reference data R at the offset in the upper rotational position of the respective rotor blade 3a, 3b, 3c are preferably determined, since influences in this rotational position essentially mutually mutually by a tilt angle of the rotor axis R and a cone angle of the rotor blades 3a, 3b, 3c cancel. With regard to the gain, the operating conditions are preferably relevant in relation to the parameters of rotor speed, wind speed, rotor or generator torque, and outside temperature.

Alternatively or additionally, the reference data R can be determined as an expected value, which is taken from a database with empirical or simulated reference data or is provided by means of a simulation. The reference data R can be stored as a function, but also in any other type of unambiguous assignment rule, such as a table, depending on the operating conditions and / or the position data P. The correction parameters KP are then set in such a way that they correspond to the target values determined on the basis of measurements or the target values determined on the basis of expected values. These determined values of the correction parameters KP are subsequently used to determine the sheet load M in work step 102 in the calibration function. The values of the blade load M determined in this way are then used, as shown in FIG. 2, on the one hand to control the wind energy installation in work step 103, and on the other hand are used again to adapt the calibration terms to work step 104a; 104b issued. In this way, calibration can be carried out iteratively in several steps.

When determining the actual value of the correction parameter KP, which is output to the correction function, the currently determined value is preferably provided the correction parameter KP as well as other values of the correction parameters that have been determined in the past.

For this purpose, a delay function, in particular a function of a PT1 element, is preferably used, which takes into account a predefined number of values of the correction parameters KP or a number of values which correspond to a predefined time period. This time period is preferably defined via a time constant T.

On the one hand, with such a function, values of the correction parameters KP, which were determined in an older calibration process, are preferably no longer taken into account as soon as a value of a more recent calibration process is newly determined. Furthermore, with such a delay function, preferably younger values of the correction parameters KP are weighted higher than older values. In this way, statistical averaging of the correction values determined on the basis of measurements or sensor signals S is achieved, which in particular reduce the significance of short-term operating point deviations or measurement deviations.

Different time constants T can be used for different correction parameters KP. For an offset, for example, a time constant of T = 100 seconds, for a gain, for example, a time constant of T = 200 seconds.

Statistically high-quality results can be achieved by using delay functions in the calibration. Furthermore, the influence of short-term incorrect measurements or effects, such as a temporary ice build-up, on the future calculation of the impact bending moment M can be kept low.

However, it should be taken into account here that preferably only those sensor signals S or calibration processes are taken into account that were recorded under the above-mentioned boundary conditions. The time period of the presence of these boundary conditions is measured using a time counter, so that the real time period, which is defined by the time constant, can be considerably longer. For example, a PT1 link with a set time constant of T = 100s to determine the offset can take into account a real time period from several days in the past, if on average calibration processes could only be carried out twice a day for a period of two seconds under the specified boundary conditions . Employees doing repairs on the wind turbine, the time counters and the correction terms can preferably be reset.

After the wind energy installation 1 has been restarted, smaller time constants T are preferably used than during operation. This means that the calibration function can be adjusted quickly, even if it is statistically less precise, after a restart. The current operation is preferably defined as operation after a period after the restart, which corresponds to one to ten times the value of the time constant at restart. For example, a pair of values for the time constants T _{k |} ein = 15s and T _large = 150s. The switchover therefore takes place automatically when the previously mentioned time counter exceeds a multiple of the smaller time constant T of the PT1 link setting.

Limit values are preferably specified for the correction parameters KP, these limit values being compared in a work step 105 with the values of the correction parameters KP determined in work steps 104a, 104b. If the value of a correction parameter lies outside the limit value or limit value range, preference is given to a warning message or error message is issued 106. Measures to protect the wind turbine can be taken on the basis of this message. For example, the operation of the wind turbine can be throttled or stopped in the event of an error message. In addition, as shown in FIG. 2, the output of the correction parameters to the correction function can be prevented if an error message occurs.

It is pointed out that the exemplary embodiments described above are only examples which in no way limit the scope of protection, the application and the structure. Rather, the person skilled in the art is given a guide for the implementation of at least one embodiment by the preceding exemplary embodiments, it being possible for various changes, in particular with regard to the function and arrangement of the described components, to be carried out without leaving the scope of protection which arises the claims and these equivalent combinations of features. Reference list

1 wind turbine

 2 rotor

3a, 3b, 3c rotor blade

 4 rotor hub

 5 gondolas

 6 tower 10 system

20 position detection device

30 interface

 40a, 40b sensor device

 50 evaluation tools

60 control funds

100 procedures

 101-106 Process steps R rotor axis

 E rotor blade longitudinal axis

 A axis of rotation

WR wind direction P position signal

R reference data

S sensor signal M blade load

Claims

Claims 1. A method (100) for operating a wind energy installation (1) which has at least one rotor blade (3a, 3b, 3c), comprising the following steps:  - Detection (101) of sensor signals (S) which are suitable for characterizing a blade load (M), in particular an impact bending moment, on the at least one rotor blade (3a, 3b, 3c);  - Determining (102) a sheet load (M) on the basis of the detected sensor signals (S) and a calibration function; and  - Controlling (103) the wind energy installation (1), in particular an adjustment angle of the at least one rotor blade (3a, 3b, 3c), on the basis of the determined blade load (M);  wherein the calibration function is adapted by means of calibration processes on the basis of the determined sheet load, whereby to calibrate the calibration function, younger calibration processes are weighted higher than older calibration processes. 2. A method (100) for operating a wind energy installation (1) which has at least one rotor blade (3a, 3b, 3c), in particular according to claim 1, comprising the following steps:  - Detection (101) of sensor signals (S) which are suitable for characterizing a blade load (M), in particular an impact bending moment, on the at least one rotor blade (3a, 3b, 3c);  - Determining (102) a sheet load (M) on the basis of the detected sensor signals (S) and a calibration function; and  - Controlling (103) the wind energy installation (1), in particular an adjustment angle of the at least one rotor blade (3a, 3b, 3c), on the basis of the determined blade load (M); wherein the calibration function is adapted by means of calibration processes on the basis of the determined sheet load, wherein a predefined number of calibration processes or calibration processes depending on a predefined time constant, which preferably defines a predefined time segment, are taken into account for adapting the calibration function, preferably an older one Calibration process, in particular an oldest calibration process, is no longer taken into account, so a younger calibration process, in particular a youngest calibration process, will soon be taken into account. 3. The method (100) according to claim 1 or 2, wherein the calibration function is continuously adapted in the operation of the wind turbine (1). 4. The method (100) according to any one of the preceding claims, wherein the calibration function is adapted only when predefined criteria, in particular with regard to operating conditions or an operating state of the wind power plant (1), are met. 5. The method (100) according to one of the preceding claims, further comprising the following working step:  - Determining (104a; 104b) at least one correction parameter (KP) of the calibration function, in particular an offset and / or a gain, on the basis of the determined sheet load. 6. The method (100) according to one of claims 2 to 5, wherein the time constant after a restart of the wind energy installation, in particular after a new installation or component replacement, is less, in particular 10 to 75%, of the time constant during operation, preferably after a first adjustment of the calibration function after the restart to the predefined time constant during operation, in particular after a time period which corresponds to the time constant from 1 to 10 times, in particular from 1.5 to 5 times. 7. The method (100) according to one of claims 1 to 6, wherein the calibration processes are weighted in such a way that new calibration processes bring about an adjustment of the calibration function which has a predetermined difference in relation to a change in a value of the calibration function does not exceed. 8. The method (100) according to claim 7, wherein the weighting is carried out in such a way that an adaptation of the calibration function beyond the predetermined difference requires a large number of calibration processes, in particular at least one third of the calibration processes taken into account for the adaptation. 9. The method (100) according to any one of claims 1 to 8, wherein a delay function, in particular a function of a PT1 element, is imaged when the calibration processes are taken into account. 10. The method (100) according to one of claims 5 to 9, wherein correction parameters (KP) are an offset and / or a gain, further comprising at least one of the following work steps:  - Determining (104a) an offset value of the calibration function of the at least one rotor blade (3a, 3b, 3c), whereby only values of the blade load (M) within a predefined angular sector a about the upper rotational position of the at least one rotor blade (3a , 3b, 3c), in particular about 3 °> a> -3 °; and or  - Determining (104b) a gain value of the calibration function of the at least one rotor blade (3a, 3b, 3c), with only values of the blade load (M) which meet a boundary condition with respect to a predefined time constant, which preferably one predefined time period, which preferably corresponds to at least half a revolution, preferably one full revolution or two revolutions, of the rotor (2) is taken into account; and wherein the calibration function is adapted by means of the determined values. 1 1. The method (100) according to any one of claims 5 to 10, further comprising the following steps:  - Comparing (105) a value of the correction parameter (KP), in particular the gain value, with a predefined limit value L, in particular 0.85 <L <1.15, preferably 0.92 <L <1.08, particularly preferably 0.94 <L <1.06; and - Issuing (106) a status message, in particular a warning message or an error message, when the value of the correction parameter (KP) reaches and / or exceeds or falls below the respectively predefined limit value. 12. A computer program comprising instructions which, when executed by a computer, cause the latter to carry out the steps of a method according to one of claims 1 to 11. 13. Computer-readable medium on which a computer program according to claim 12 is stored. 14. System (10) for operating a wind energy plant (1) which has at least one rotor blade (3a, 3b, 3c), comprising:  - an interface (30) set up for detecting sensor signals (S) which are suitable for characterizing a blade load (M), in particular an impact bending moment, on the at least one rotor blade (3a, 3b, 3c);  - Evaluation means (50), set up to determine a sheet load (M) on the basis of the detected sensor signals (S) and a calibration function, further set up to adapt the calibration function by means of calibration processes based on the determined sheet load (M), with younger ones Calibration processes are weighted higher than older calibration processes and / or a predefined number of calibration processes or calibration processes are taken into account as a function of a predefined time constant, which preferably defines a predefined time period, preferably not an older calibration process, in particular an oldest calibration process more is taken into account as soon as a recent calibration process, in particular a youngest calibration process, is taken into account; and  - Control means (60) of the wind power plant (1), in particular an adjustment angle of the at least one rotor blade (3a, 3b, 3c), on the basis of the determined blade load (M). 15 wind turbine (1) with a system (10) according to claim 14.