METHOD FOR DETECTING A SENSOR MALFUNCTION OF A LOAD SENSOR OF A WIND POWER INSTALLATION

Abstract

A method for detecting a sensor malfunction of a load sensor of a wind power installation having a rotor and at least one rotor blade, wherein the load sensor is configured to detect a loading variable of one of the rotor blades, and the sensor malfunction involves the functional freezing of a sensor signal from the load sensor, such that it remains temporally constant, wherein at least one loading variable of the rotor blade is estimated and, in the event that the sensor signal is temporally constant, a comparability test is executed wherein, according to the at least one estimated loading variable, a check is executed as to whether a non-constant sensor signal is to be anticipated, and a sensor malfunction is identified by reference to the comparability test.

Claims

1. A method comprising: detecting a sensor malfunction of a load sensor of a wind power installation, the wind power installation having a rotor and a rotor blade, the detecting comprising: using the load sensor to detect a loading variable of the rotor blade, and wherein detecting the sensor malfunction comprises detecting a sensor signal of the load sensor that is functionally frozen, such that the sensor signal is temporally constant, estimating at least one loading variable of the rotor blade, in response to the sensor signal being temporally constant, executing a comparability test, in which according to the at least one estimated loading variable, a check is executed as to whether a non-constant sensor signal is to be anticipated, and identifying a sensor malfunction based on the comparability test.

2. The method according to claim 1, wherein the load sensor is a strain measurement sensor and arranged on the rotor blade, wherein the strain measurement sensor is configured to detect a blade load based on strain in the rotor blade.

3. The method according to claim 1, wherein the at least one estimated loading variable is a gravitational load acting on the rotor blade, wherein a blade load is generated by a weight force acting on the rotor blade, and wherein the estimated gravitational load is determined based on a rotor position of the rotor.

4. The method according to claim 1, wherein the at least one estimated loading variable is a wind load acting on the rotor blade, wherein the wind load is dependent upon a wind speed, and wherein: the wind load is determined based on a measured wind speed, and the measurement of wind speed comprises: a LiDAR measurement, and/or an anemometer measurement, or the wind load is determined in accordance with a state variable which is dependent upon the wind speed, and the state variable comprises: a generated power, an acceleration power of the rotor, and/or a generator torque detected.

5. The method according to claim 1, wherein, in the comparability test, the at least one estimated loading variable includes a first estimated loading variable and a second estimated loading variable, wherein a check is executed as to whether a sensor malfunction is present, wherein: the first estimated loading variable is an estimated gravitational load, and the second estimated loading variable is an estimated wind load.

6. The method according to claim 1, determining a projected loading variable based on the estimated loading variable projected for a measurement direction of the load sensor, and wherein in the comparability test, according to the projected loading variable, a check is executed as to whether a non-constant sensor signal is to be anticipated.

7. The method according to claim 1, wherein if it has been detected that the sensor signal is temporally constant, in the comparability test executed according to the at least one estimated loading variable, and according to the at least one projected loading variable, it is determined whether a temporally non-constant sensor signal was anticipated, and depending upon the anticipation of a temporally non-constant sensor signal a sensor malfunction is identified.

8. The method according to claim 1, wherein, in the comparability test for appraisal of whether a temporally non-constant sensor signal was to be anticipated, a check deviation is generated as a difference between the projected loading variable at a current time point, and the projected loading variable for a time point at which the sensor signal was last not detected as temporally constant, and the check deviation is compared with a specified limiting value, and if the check deviation does not exceed the limiting value, it is expected that the sensor signal is temporally constant, wherein different limiting values are specified for the different loading variables considered, and wherein a different limiting value is specified in each case for the check deviation with respect to the gravitational load and for the check deviation with respect to the wind load.

9. The method according to claim 1, wherein if the sensor signal has been detected as temporally constant, but, by the execution of the comparability test, it is established that a temporally constant signal was not anticipated, a counter is advanced, wherein a sensor malfunction is identified, if the counter has achieved a stipulated threshold value.

10. The method according to claim 9, wherein: if, during the comparability test, detecting that the sensor signal has changed, then the counter is reset, or if the sensor signal has been detected as constant, and a constant sensor signal is anticipated, the counter is left at its current reading.

11. The method according to claim 1, wherein in the comparability test, if the sensor signal is constant, a gravitational load comparison, by way of a comparison with an estimated gravitational load, and a wind load comparison, by way of a comparison with an estimated wind load is executed, wherein in each case, an identical or the same counter are respectively advanced by one upward increment, if it is established that a non-constant sensor signal is anticipated, and wherein a sensor malfunction is assumed, if the counter has achieved a threshold value, wherein in the gravitational load comparison, a different upward increment is applied to that employed in the wind load comparison.

12. The method according to claim 1, wherein the sensor signal is greater than a decibel threshold, and wherein the load sensor is considered functionally frozen such that the sensor signal is temporally constant if a predefinable fluctuation amplitude or variation amplitude is not quantitatively exceeded.

13. A wind power installation comprising: a measurement and control device configured to execute the method according to claim 1, a tower, the rotor, the load sensor, and the rotor blade.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0095] The present invention is further described in greater detail hereinafter by reference to examples, in consideration of the figures. Identical reference symbols identify the same or similar elements.

[0096] FIG. 1 shows a perspective view of a wind power installation;

[0097] FIG. 2 shows two load sensors, fitted to a rotor blade;

[0098] FIG. 3 shows a method according to an embodiment of the invention;

[0099] FIG. 4 shows a diagram for determining the check deviation;

[0100] FIG. 5 shows the advancement of the counter in response to an anticipated gravitational load;

[0101] FIG. 6 shows the advancement of a counter in response to an anticipated wind load;

[0102] FIG. 7 shows time diagrams for the illustration of the advancement of a counter.

DETAILED DESCRIPTION

[0103] FIG. 1 shows a schematic representation of a wind power installation according to the invention. The wind power installation 100 comprises a tower 102 and a gondola 104 on the tower 102. On the gondola 104, an aerodynamic rotor 106 having three rotor blades 108 and a spinner 110 is provided. The aerodynamic rotor 106, during the operation of the wind power installation, is set in rotary motion by the action of wind, and thus additionally rotates an electrodynamic rotor or armature of a generator, which is directly or indirectly coupled to the aerodynamic rotor 106. The electric generator is arranged in the gondola 104, and generates electrical energy. The pitch angle or the rotor blades 108 can be adjusted by pitch motors at the rotor blade roots 109 of the respective rotor blades 108.

[0104] A load sensor is connected to at least one of the rotor blades 108. In particular, each rotor blade 108 comprises at least two, and particularly two pairs of load sensors.

[0105] FIG. 2 shows a rotor blade 108, to which a first and a second load sensor 112, 114 are fastened. The load sensors are arranged such that they are offset about the rotor blade through an angle of 90°.

[0106] In the event of bending of the rotor blade, strain is measured by the load sensors 112, 114. Strain which is measured by the first load sensor 112 is converted into a first bending moment 132, and strain which is measured by the second load sensor 114 is converted into a second bending moment 134. To this end, a first bending axis 122 is defined for the first load sensor 112, and a second bending axis 124 is defined for the second load sensor 114, about which the bending moment 132 or 134 is respectively calculated.

[0107] The two bending axes 122, 124 are mutually perpendicular, wherein the same also applies to the bending moments, in the sense that the bending moments 132, 134 which are defined by means of the two load sensors assume mutually perpendicular bending axes 122, 124. The directions in which the bending moments are applied can be considered as measurement directions such that, accordingly, the measurement directions are also mutually perpendicular. This is achieved by the offset arrangement of the load sensors 112, 114 through 90°. Accordingly, the first load sensor 112 is arranged in a first strain direction 142 along the longitudinal direction of the rotor blade, and the second load sensor 114 is arranged in a second strain direction 144, likewise along the longitudinal direction of the rotor blade.

[0108] FIG. 3 shows a method according to an embodiment of the invention.

[0109] Firstly, a sensor signal from the load sensor is detected.

[0110] In a constancy check step 210, a check is then executed as to whether the sensor signal is temporally constant, i.e., the sensor signal is functionally frozen. Fluctuations, e.g., caused by evaluation electronics, are also detected as temporally constant.

[0111] If it is detected, in the constancy check step 210, that the sensor signal is temporally constant, an anticipation step 220 is executed. In the anticipation step 220, the comparability test is then executed. A check is further executed as to whether the temporally constant sensor signal was anticipated, or whether a temporally non-constant sensor signal was anticipated. This is executed in accordance with at least one estimated loading variable of the rotor blade.

[0112] If it is determined, in the anticipation step, that a temporally constant behavior is not anticipated, a counter is advanced in an advancement step 240.

[0113] Otherwise, i.e., if it is established in the anticipation step 220 that a temporally constant sensor signal was to be anticipated, the counter is left at its current reading.

[0114] There then follows an evaluation step 250, which is executed in any case, i.e., even in the event that an advancement of the counter has been executed in an advancement step 240.

[0115] If, however, in the constancy check step 210, it is already established that the sensor signal is temporally non-constant, or that the sensor signal has changed, a reset step 230 is executed. In the reset step 230, the counter is reset, i.e., is set back to zero.

[0116] Further to the reset step 230, the evaluation step 250 is likewise executed.

[0117] In the evaluation step 250, the counter is evaluated. Depending upon the reading, a sensor malfunction is identified.

[0118] If the presence of a sensor malfunction is detected, a warning message is generated. Optionally, the wind power installation is shut down, or is switched to a safe operating mode.

[0119] If, on the basis of the counter reading in the evaluation step 250, no sensor malfunction is identified, the method recommences for a subsequent time step, wherein a further sensor signal from the load sensor is detected and, in the constancy check step 210, a check is executed as to whether the sensor signal is temporally constant. The method is thus repeated continuously.

[0120] The method is thus essentially based upon the outcome of the anticipation step 220.

[0121] To this end, in the anticipation step, a loading variable of the rotor blade is estimated. A distinction is drawn between a gravitational load and a wind load. In the anticipation step 220, a gravitational load and a wind load are estimated accordingly.

[0122] Both the estimated gravitational load and the estimated wind load are projected for the measurement direction of the load sensor. For both projected loading variables, a check deviation is determined. The check deviation is expressed as the difference between the projected loading variable at a current time point and the projected loading variable at the time at which the sensor signal was identified as temporally constant.

[0123] Any check deviation which exceeds a stipulated limiting value, whether for the estimated gravitational load or for the estimated wind load, will result in an advancement of the counter, in an advancement step 240. Different upward increments can be assigned to different loading variables, by which the counter is then advanced in each case.

[0124] FIG. 4 illustrates the determination of a check deviation in a projected loading variable. A coordinate system 300 is represented, in which the loading variable L is plotted on the x-axis, and the time t is plotted on the y-axis.

[0125] The measured sensor signal 310 is represented as a solid line. Also represented, by a broken line, with effect from the time point t.sub.1, is the projected loading variable 320, i.e., the anticipated loading variable projected for the measurement direction of the load sensor.

[0126] In the region between time point t.sub.0 and time point t.sub.1, the sensor signal continues to vary by a significant amplitude. At time point t.sub.1, the sensor signal is detected as temporally constant. Time point t.sub.1 is thus the time point of the most recent signal variation.

[0127] At time point t.sub.1, i.e., the time point of the most recent signal variation of sufficient magnitude, the projected loading variable 320 assumes the value P.sub.1. In successive sequential time steps, the check deviation is then determined as the difference between the current projected loading variable and the projected loading variable P.sub.1 at the time point of the most recent signal variation t.sub.1. Provided that the check deviation does not quantitatively exceed a limiting value G, it is anticipated that the sensor signal will be temporally constant.

[0128] At time point t.sub.2, the projected loading variable 320 enters the tolerance range, and assumes an approximate value of P.sub.2=P.sub.1+G. For higher values of t, the projected loading variable lies outside the tolerance range. In consequence, the check deviation, with effect from time point t.sub.2, quantitatively exceeds the limiting value G.

[0129] With effect from time point t.sub.2, a variation in the sensor signal is thus anticipated. In the next anticipation step 220, it is thus detected that a constant sensor signal is not anticipated, and the advancement step 240 is executed. Between t.sub.1 and t.sub.2, an arbitrary number of time steps can be included. In theory, however, time point t.sub.2 can also be the immediately succeeding time step, which follows time point t.sub.1.

[0130] In the present example, a high degree of absolute coincidence between the sensor signal and the projected loading variable is also represented. However, as only the presence of variations in excess of threshold values is considered, this is not essential. The same result would be achieved if the sensor signal 310 and the projected loading variable 320 were to be mutually displaced in the direction of the x-axis.

[0131] FIG. 5 shows an exemplary advancement of the counter, if only gravitational loads are acting on the rotor blade, or at least if only these loads are subject to variation. In the coordinate system 400, the check deviation for the gravitational load ΔP.sub.G is plotted on the x-axis, against the time t on the y-axis.

[0132] The check deviation 410 thus determined is plotted as a time characteristic, together with a limiting value 420 of value G.sub.G, upon the overshoot of which a variation in the sensor signal associated with gravitational loads applied is anticipated.

[0133] At time point t.sub.2, the check deviation 410 exceeds the limiting value 420, such that a variation in the sensor signal is anticipated.

[0134] The coordinate system 400 additionally comprises a further x-axis for the variation of the rotor position Δφ. With effect from time point t.sub.2, the variation of the rotor position is determined, i.e., the further rotation of the rotor blade, in degrees. The curve 450 shows an exemplary variation of the rotor position. A signal variation will be permissible, until such time as the rotor has rotated through a predefined angle, e.g., 90°. In the example, this is achieved at time point t.sub.3.

[0135] The advancement of the counter Z is represented on the same time axis, below the check deviation characteristic. The counter or the selected upward increment, together with the threshold value, is correspondingly dimensioned such that a signal variation for a rotor rotation through 90° is permissible, before a sensor malfunction is identified. At time point t.sub.3, the check deviation 410 for the time required to execute a rotor rotation through 90° with effect from time point t.sub.2 exceeds the limiting value 420.

[0136] The coordinate system 470 thus represents the counter reading Z, plotted against the same time axis t. The counter 480 is standardized such that, upon the achievement of a value of 1, a sensor malfunction is identified.

[0137] With effect from time point t.sub.2, the check deviation 410 exceeds the limiting value 420, such that the counter 480 is advanced. The upward increment by which the counter 480 is advanced is proportional to the variation in the rotor position, and is dimensioned such that the counter 480, directly upon the completion of a rotor rotation through 90°, i.e., at time point t.sub.3, achieves the threshold value 1, and the sensor malfunction is identified.

[0138] FIG. 6 shows a case in which only wind loads are acting on the rotor blade, or at least only these loads are subject to variation. In the diagram 500, the check deviation ΔP.sub.W associated with estimated wind loads is plotted as a characteristic 510 against time t.

[0139] The check deviation 510 thus determined is plotted as a characteristic, and an associated limiting value 520 of value G.sub.W is also represented, with effect from the overshoot of which by the check deviation 510 a sensor variation will be anticipated. At time point t.sub.2, the check deviation 510 exceeds the limiting value 520, such that a variation in the sensor signal is anticipated.

[0140] Advancement of the counter by the upward increment in response to wind loads is dimensioned such that an anticipated, but absent sensor variation is tolerated for a duration of 4 seconds, indicated by the time difference 550. At time point t.sub.3, the check deviation 510 for a duration of 4 seconds exceeds the limiting value 520, such that a sensor malfunction is identified.

[0141] Moreover, in the coordinate system 570, a counter reading Z is also plotted against time t. Again, the counter 580 is standardized such that, upon the achievement of the threshold value 1, a sensor malfunction is identified. At time point t.sub.2, the check deviation 510 exceeds the limiting value 520, resulting in the advancement of the counter 580. The upward increment by which the counter 580 is advanced in response to the action of wind loads is dimensioned such that the counter 580 achieves the threshold value 1 after 4 seconds, and the sensor malfunction is identified.

[0142] FIG. 7 illustrates the advancement of a counter, particularly the counter 580 represented in FIG. 6, and the identification of a sensor malfunction in accordance with both estimated loading variables, namely, the gravitational load and the wind load, wherein the simulation is based upon an actual situation.

[0143] To this end, FIG. 7 shows three coordinate systems 600, 602, 604 for the same time, which is respectively plotted on the y-axes of the coordinate systems 600, 602, 604.

[0144] In the uppermost coordinate system 600, the sensor signal 610 detected is represented by a solid line. Additionally, anticipated loading variables by way of the wind load 620 and the gravitational load 630 are represented by a broken line and a dotted line respectively. The unit of load is kNm.

[0145] At time point t.sub.2, a constant sensor signal 610 is detected. The check deviation for the gravitational load is determined or evaluated accordingly. If the check deviation for the gravitational load lies below the limiting value, and thus does not result in the advancement of the counter, the check deviation for the wind load, namely, in the wind direction, is determined or evaluated instead. To this end, the anticipated gravitational load and the anticipated wind load are projected for the measurement direction of the load sensor and, in each case, a difference is taken from the projected loading variable at time point t.sub.2, the time of the most recent signal variation.

[0146] The middle coordinate system 602 represents the check deviation ΔP thus determined in kNm for the wind load 622 (broken line) and the check deviation for the gravitational load 632 (dotted line). If the check deviation does not exceed the associated limiting value, there is no resulting advancement of the counter, and the check deviation is set to zero. However, this is represented by way of illustration only, in order to indicate which criterion results in the advancement of the counter.

[0147] Accordingly, the coordinate system 602 shows only the pro rata check deviation over time which exceeds the respective associated limiting value, and which results in the advancement of the counter on the grounds of the working point.

[0148] For the gravitational load and the wind load, different criteria are applied, or different design ratings are considered. For the gravitational load, the counter is advanced by an upward increment which is proportional to the rotation of the rotor, i.e., to the value of the further rotation of the rotor blade since the time point of the most recent signal variation. The upward increment is selected such that, at the latest, a sensor malfunction is detected further to a rotation through 90°, if a variation in the gravitational load is anticipated on a continuous basis.

[0149] The action of wind loads results in the advancement of the counter by a different upward increment. This is selected such that, in the absence of the action of gravitational loads, and thus the absence of any variation in gravitational loads, a sensor malfunction is detected after 4 seconds at the latest.

[0150] As both mechanisms result in the advancement of the same counter, the simultaneous action of variations in wind loads and gravitational loads can result in the more rapid identification of a sensor malfunction.

[0151] In the bottommost coordinate system 604, the counter reading Z is plotted against time t. The counter 680 is standardized such that a value of 1 results in the identification of a sensor malfunction, and the wind power installation is shut down.

[0152] Between time point t.sub.2 and time point t.sub.3, the check deviation 622 associated with wind loads results in the advancement of the counter 680 and, between t.sub.3 and t.sub.4, the check deviation 632 associated with gravitational loads results in the advancement of the counter 680.

[0153] At time point t.sub.1, a short-term detection of a constant sensor signal is observed, notwithstanding the anticipation of a variation on the grounds of the check deviation 622. This would result in the advancement of the counter 680. However, the threshold value has not been achieved, and no sensor malfunction detected. Thereafter, the sensor signal shows a further variation, thereby resulting in the resetting of the counter such that, at time point t.sub.2, a value of zero is resumed.

[0154] The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.