INDIVIDUAL BLADE ADJUSTMENT IN A WIND POWER INSTALLATION

Abstract

A method for controlling a wind power installation, wherein the wind power installation has a rotor with a plurality of rotor blades, the rotor blades are adjustable in their blade angle, each rotor blade is activatable individually, for the individual activation, in each case a total adjustment rate R.sub.of which indicates an intended speed of change of the respective blade angle is predetermined, a collective blade angle identical for all of the rotor blades is provided, a collective adjustment rate identical for all of the rotor blades describes an intended speed of change of the collective blade angle, an individual offset angle which indicates a value by which the blade angle is intended to deviate from the collective blade angle is predetermined for each rotor blade, an individual feed forward control adjustment rate which indicates an adjustment rate which is provided for reaching the offset angle is determined for each rotor blade from the individual offset angle, an individual offset deviation is determined for each rotor blade depending on a comparison of the individual offset angle and a detected blade angle of the rotor blade, and the total adjustment rate of each rotor blade is determined depending on the collective blade angle and/or the collective adjustment rate, the individual feed forward control adjustment rate, and the individual offset deviation.

Claims

1. A method for controlling a wind power installation, wherein: the wind power installation has a rotor with a plurality of rotor blades, the plurality of rotor blades have adjustable blade angles, each rotor blade of the plurality of blade is individually activatable, the method comprising: for individual activation of each rotor blade of the plurality of rotor blades, predetermining a total adjustment rate indicative of an intended speed of change of the respective blade angle, determining an individual offset angle, which indicates a value by which the blade angle is intended to deviate from the collective blade angle, for each rotor blade, determining an individual feed forward control adjustment rate, which indicates an adjustment rate, which is provided for reaching the offset angle, for each rotor blade from the individual offset angle, determining an individual offset deviation for each rotor blade depending on a comparison of the individual offset angle and a detected blade angle of the respective rotor blade, and determining the total adjustment rate of each rotor blade depending on: a collective blade angle identical for all of the rotor blades, and/or a collective adjustment rate identical for all of the rotor blades describing an intended speed of change of the collective blade angles, the individual feed forward control adjustment rate, and the individual offset deviation.

2. The method as claimed in claim 1, comprising: determining the individual feed forward control adjustment rate from the individual offset angle by a feed forward control, and determining a feedback controller adjustment rate from the individual offset deviation by an offset feedback controller to adjust the individual offset deviation, wherein the total adjustment rate is determined from the collective adjustment rate, the individual feed forward control adjustment rate, and the feedback controller adjustment rate.

3. The method as claimed in claim 2, wherein the total adjustment rate is a sum of the collective adjustment rate, the individual feed forward control adjustment rate, and the feedback controller adjustment rate.

4. The method as claimed in claim 1, wherein the individual feed forward control adjustment rate is determined independently of the detected blade angle, in particular independently of the individual offset deviation.

5. The method as claimed in claim 1, wherein the individual feed forward control adjustment rate is determined independently of the individual offset deviation.

6. The method as claimed in claim 1, wherein the individual offset angle is predetermined as a temporal offset profile by an offset function which is time-dependent and/or dependent on a position or rotation of the rotor.

7. The method as claimed in claim 1, wherein each individual offset angle is predetermined as a temporal offset profile having: a pitching component for reducing a pitching moment, and a yaw component for reducing a yaw moment, wherein the pitching component and the yaw component are combined in a temporal profile of the individual offset angle.

8. The method as claimed in claim 1, wherein each individual offset angle is predetermined as a temporal offset profile by a time-dependent offset function to reduce a pitching moment and a yaw moment, wherein the temporal profile comprises an amplitude parameter and a phase parameter, and wherein the amplitude parameter and the phase parameter take into consideration a reduction in the pitching moment and the yaw moment.

9. The method as claimed in claim 1, wherein: at least one amplitude limit value is predetermined for a offset profile, for each rotor blade, checking whether the offset profile reaches the amplitude limit value, and if the offset profile is reached, interrupting a connection of the individual feed forward control adjustment rate to the collective adjustment rate, in particular wherein a or the feedback controller adjustment rate continues to be connected to the collective adjustment rate.

10. The method as claimed in claim 9, wherein interrupting the connection of the individual feed forward control adjustment rate to the collective adjustment rate comprises interrupting such that the feedback controller adjustment rate continues to be connected to the collective adjustment rate.

11. The method as claimed in claim 1, wherein an offset profile is predetermined via the following offset function f(t):
f(t)=A*sin(ω*t+ϕ) wherein: A denotes a predeterminable amplitude, ω describes a rotational speed of the rotor, and ϕ describes a predeterminable angular displacement relative to a reference angle.

12. The method as claimed in claim 1, wherein the individual feed forward control adjustment rate is predetermined as a feed forward control profile via the following feed forward control function v(t):
v(t)=A*cos(ω*t+ϕ)*(ω+dϕ/dt)+dA/dt*sin(ω*t+ϕ) wherein: A denotes a predeterminable amplitude, ω describes a rotational speed of the rotor, and ϕ describes a predeterminable angular displacement relative to a reference angle.

13. The method as claimed in claim 1, wherein a or the amplitude A and a or the angular displacement ϕ of a or the offset function f(t)=A*sin(ω*t+ϕ) are determined depending on detection of a loading, and in particular the amplitude A and/or the angular displacement ϕ form filtered variables, in particular wherein depending on the detection of a load, a preliminary amplitude A.sub.v and/or a preliminary angular displacement ϕ, are ascertained, and the amplitude A and/or the angular displacement ϕ are each determined from the preliminary amplitude A.sub.v and/or the preliminary angular displacement ϕ.sub.v by filtering of the preliminary amplitude A.sub.v and/or the preliminary angular displacement ϕ.sub.v, and/or in each case by predetermining a ramp as the maximum speed of change for the preliminary amplitude A.sub.v and/or for the preliminary angular displacement ϕ.sub.v, or depending on detection of a load, the amplitude A and the angular displacement ϕ are predetermined as constant values and therefore a simplified feed forward control function vs(t) is predetermined from a derivation of the offset function f(t)=A*sin(ω*t+ϕ) as:
vs(t)=A*cos(ω*t+ϕ)*ω

14. A wind power installation comprising: a rotor with a plurality of rotor blades, wherein the plurality of rotor blades have adjustable blade angles, wherein each rotor blade of the plurality of rotor blades is individually activatable, and a controller configured for carrying out an individual blade adjustment, and wherein the controller is configured to perform the method as claimed in claim 1.

15. The wind power installation as claimed in claim 14, comprising: a detection device for detecting a loading of the wind power installation, for detecting a pitching moment component and a yaw moment component for each rotor blade.

16. The wind power installation as claimed in claim 15, wherein the controller is configured to determine, from the detected pitching moment component and the detected yaw moment component, an offset angle individual to the respective rotor blade, and to determine an individual feed forward control adjustment rate for the respective rotor blade.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0097] The invention will be explained in more detail below by way of example using embodiments with reference to the accompanying figures.

[0098] FIG. 1 shows a wind power installation in a perspective illustration.

[0099] FIG. 2 schematically shows a closed-loop control system of a conventional individual blade adjustment.

[0100] FIG. 3 schematically shows an individual blade control system via an adjustment rate specification.

[0101] FIG. 4 shows a schematic closed-loop control system of an individual blade adjustment via a pitch rate with feed forward control and an offset feedback controller for controlling the individual blade angle to be connected.

[0102] FIG. 5 schematically shows an overall structure of an individual blade adjustment with feed forward control and an offset feedback controller for the offset angle to be connected.

[0103] FIG. 6 shows a simplified diagram of a possible offset angle profile of a rotor blade.

DETAILED DESCRIPTION

[0104] FIG. 1 shows a schematic illustration of a wind power installation according to the invention. The wind power installation 100 has a tower 102 and a nacelle 104 on the tower 102. An aerodynamic rotor 106 with three rotor blades 108 and a spinner 110 is provided on the nacelle 104. During operation of the wind power installation, the aerodynamic rotor 106 is set into a rotational movement by means of the wind and therefore also rotates an electrodynamic rotor of a generator which is coupled directly or indirectly to the aerodynamic rotor 106. The electrical generator is arranged in the nacelle 104 and generates electrical energy. The pitch angles of the rotor blades 108 can be changed by pitch motors on the rotor blade roots 109 of the respective rotor blades 108.

[0105] FIG. 2 shows a closed-loop control system 200 which relates to a conventional blade angle control with individual blade adjustment. The structure shows an operating control block 202 which predetermines a collective blade angle ac. Said operating control block 202 comprises, for example, a known rotational speed control which outputs the blade angle as correcting variable for controlling the rotational speed. This operating control therefore relates to a blade angle which is identical for all of the rotor blades and which is referred to as the collective blade angle. It can also be synonymously referred to as the common blade angle.

[0106] In addition, an individual blade control 204 is provided which provides an offset angle α.sub.of for each rotor blade. To this extent, FIG. 2 shows the structure for an individual blade. A wind power installation conventionally has three rotor blades and, accordingly, three such control systems would be required.

[0107] The offset angle α.sub.of and the collective blade angle ac are added up at the first summing point 206 to form the blade setpoint angle α.sub.S. To this extent, three blade setpoint angles are also produced for three rotor blades and correspondingly three structures. Since, however, only the structure for one rotor blade is shown here for illustrative purposes, possible indices for displaying one specific rotor blade are dispensed with. The presented structure is identical to this extent for all of the rotor blades.

[0108] The blade setpoint angle α.sub.S is then compared at the second summing point 208 with a detected actual angle α.sub.i. The result is a control deviation which is further processed in the blade control in accordance with the blade control block 210 in order to activate the schematically illustrated wind power installation 212 or the corresponding pitch motor there of the rotor blade. As a result, the detected blade angle α.sub.i is obtained which is fed back as described.

[0109] An individual blade adjustment can therefore be implemented via such a structure according to FIG. 2, but the control dynamics may be unfavorable because of the stipulation of the absolute blade angle for the collective blade angle. In particular, it has turned out that it is already advantageously possible for the operating control block to predetermine a collective adjustment rate, which is also referred to as collective pitch rate, instead of a collective blade angle.

[0110] Such a structure is illustrated in FIG. 3. The closed-loop control system 300 of FIG. 3 therefore likewise has an operating control block 302 which can likewise comprise a rotational speed control and also other operating controls and can in that respect produce a collective blade angle. However, in this structure, the operating control block 302 outputs a collective blade rate R.sub.C. An individual blade control 304 is likewise provided which outputs an offset angle α.sub.of. This is compared at a third summing point 314 with a detected blade angle α′.sub.i. The detected blade angle α′.sub.i can therefore be a blade actual angle adjusted by the collective blade angle. However, it is also conceivable that the actual blade angle is fed to the third summing point 314, instead of the offset angle α.sub.of being adjusted by the collective blade angle. At any rate, a control deviation is obtained at the third summing point 314 by the differential formation, the control deviation indicating the extent to which the offset angle α.sub.of has been successfully connected.

[0111] The deviation of the blade angle is then fed to the offset feedback controller 316 which determines an individual adjustment rate R.sub.of. Said individual adjustment rate R.sub.of and the collective adjustment rate R.sub.C are added up in the first summing point 306 and produce the setpoint adjustment rate or setpoint pitch rate for the rotor blade concerned.

[0112] In the second summing point 308, a setpoint/actual value is compared with the actual adjustment rate or actual pitch rate R.sub.i which has been detected at the wind power installation 312. This control deviation as an output from the second summing point 308 is then implemented in the adjustment rate control 310 and leads to activation of the wind power installation, in particular of a corresponding pitch drive system.

[0113] A problem with this structure in FIG. 3 is that the offset angle is compared with a detected blade angle and the deviation is adjusted with the offset feedback controller 316. Although such an adjustment is desirable, a control response with good stationary accuracy may, however, lead to poor, in particular slow, dynamics. In particular, there can be a proportional or integral response in the offset feedback controller 316 and/or inert dynamics can be provided in order to avoid excessive control excursions during changes of the guide variable. In other words, a feedback controller for stationary accuracy is provided also to adjust minor deviations. It can do this slowly so that it is then inert overall, or rapidly, but this may lead to powerful control activities during guide changes.

[0114] FIG. 4 shows a closed-loop control system 400 which is intended to be an improvement to this extent over the closed-loop control system 300 of FIG. 3. First of all, a collective adjustment rate R.sub.C is also output here in an operating control block 402. The operating control blocks 402 and 302 can be identical.

[0115] Similarly, an individual blade control 404 is provided which outputs an offset angle α.sub.of. To better explain the operation, the closed-loop control system 400 shows that the individual blade control 404 outputs the offset angle α.sub.of twice. This serves, however, for illustrative purposes and it can just as readily be provided to output the offset angle α.sub.of only at one point or another structural implementation also comes into consideration, in which, for example, the feed forward control adjustment rate is derived directly from loading data.

[0116] At any rate, provision is made that the offset angle α.sub.of is fed, inter alia, into the feed forward control 418. The feed forward control 418 determines an individual feed forward control adjustment rate R.sub.v from the individual offset angle α.sub.of. Said feed forward control adjustment rate R.sub.v is provided to already substantially implement the offset angle α.sub.of and, for this purpose, is intended to be added to the collective adjustment rate R.sub.C in order thereby to obtain a setpoint adjustment rate overall.

[0117] For this purpose, the feed forward control 418 can form a derivative of the offset angle α.sub.of, optionally provided with a gain factor, in order thereby to directly determine a corresponding adjustment rate. However, it also comes into consideration that implementations equivalent thereto are carried out, for example to undertake a simplified derivation, to undertake filtering beforehand, and/or to calculate part of the derivative beforehand. It also comes into consideration to carry out such a simplification so that the derivative can be completely calculated beforehand and only still to use specific parameters induced by the situation.

[0118] By means of such a feed forward control, a corresponding adjustment rate can therefore be implemented rapidly and specifically for the offset angle. A stationary or virtually stationary deviation can neither be recognized nor adjusted.

[0119] It is therefore additionally provided to compare the offset angle α.sub.of in the third summing point 414 with a detected blade angle α′.sub.i. As in the closed-loop control system of FIG. 3, the detected blade angle can be a modified blade angle, namely a measured blade angle modified by a collective blade angle. Here too, a modification by the collective blade angle in the offset angle α.sub.of can be carried out instead. In this case, however, such a modification would be carried out only for the offset angle α.sub.of which enters the third summing point 414. The value which enters the feed forward control 418 should not be modified.

[0120] At any rate, a setpoint/actual value comparison is carried out in the third summing point 414 and a feedback controller adjustment rate R.sub.r is determined depending thereon. This takes place by means of the offset feedback controller 416 which, however, can now be parameterized differently from the offset feedback controller 316 of FIG. 3 since the offset feedback controller 416 of FIG. 4 does not need to carry out a rapid dynamic implementation of the offset angle α.sub.of in a feed forward control adjustment rate. The offset feedback controller 416 can be configured in a targeted manner for the pure adjustment or taking a feedback controller deviation into consideration in some other way.

[0121] The feed forward control adjustment rate R.sub.v and the feedback controller adjustment rate R.sub.r are added up at the fourth summing point 420 to form the individual adjustment rate R.sub.of. Said individual adjustment rate R.sub.of is therefore the adjustment rate for the offset angle that is produced in total by the feed forward control 418 and the offset feedback controller 416. It is added at the first summing point 406 to the collective adjustment rate R.sub.C, thus resulting in the total setpoint adjustment rate R.sub.S. This can then be compared, similarly to in FIG. 3, in the second summing point 408 with a detected actual adjustment rate thus resulting in a control error. The latter is implemented in the blade rate control 410, and the blade rate control 410 then activates the wind power installation 412, in particular the corresponding blade adjustment system.

[0122] FIG. 5 illustrates an overall view of the underlying method. A wind power installation 512 is indicated for this purpose. Said wind power installation 512 has three rotor blades 552, of which only two can be seen in the schematic illustration. Each of said rotor blade 552 has a plurality of load sensors 554. The latter can each be provided on the rotor blade 552 concerned as strain gauges in the region of a rotor blade root, to mention one example.

[0123] It is schematically indicated that corresponding load signals L are fed to an evaluation block 556. Said evaluation block evaluates these measurement values and, for this purpose, can also take into consideration further operating data, such as the rotor rotational speed co and the respective rotor position Φ.

[0124] In dependence thereon, the evaluation block 556 can calculate a pitching moment component m.sub.N and a yaw moment component m.sub.G. This is indicated by the pitching moment block 558 and the yaw moment block 560. The pitching moment component m.sub.N and the yaw moment component m.sub.G therefore do not form the total pitching moment or yaw moment, but rather only the portion which is to be assigned to the respectively evaluated rotor blade. To this extent, FIG. 5 illustrates merely the evaluation for one rotor blade.

[0125] A calculation of an offset function, f.sub.N(t) for the pitching moment and f.sub.G(t) for the yaw moment, then takes place in the pitching moment block 558 and the yaw moment block 560. This offset function indicates how an offset angle profile could be selected depending on the rotational speed co of the rotor 551 in order to compensate for the pitching moment component m.sub.N or yaw moment component m.sub.G as far as possible. This is illustrated by the first and second individual offset blocks 561 and 562. The partial offset functions which are shown in these two blocks are combined in the overall offset block 564 into a common offset function f(t).

[0126] This offset function f(t) therefore reproduces a time function for the offset angle α.sub.of. The overall offset block 564 correspondingly outputs the offset angle α.sub.of. For illustrative purposes, this also takes place here in the illustration of FIG. 5 in such a manner that two offset angles α.sub.of are output, but they may be identical. The overall offset block 564 can therefore correspond to the individual blade control 404 of FIG. 4. The further processing of the offset angle α.sub.of therefore also corresponds to that illustrated in FIG. 4.

[0127] A feed forward control 518 is therefore provided, in respect of which it is made clear in FIG. 5 that it substantially forms a derivative. It is also true for this feed forward control 518 that it does not necessarily have to be an exact derivative, but that simplifications and/or additional functions, such as filtering or the provision of a gain factor, may also enter into consideration. The result is therefore a feed forward control adjustment rate R.sub.v.

[0128] In addition, an offset feedback controller 516 is provided which obtains a control deviation as a difference between the offset angle α.sub.of and a detected blade angle α′.sub.i. It is also pointed out here that the detected blade angle α′.sub.i can be modified by the collective blade angle α.sub.C. Alternatively, the offset angle α.sub.of entering said third summing point 514 can be modified.

[0129] The offset feedback controller 516 therefore outputs a feedback controller adjustment rate R.sub.r and the latter is added at the fourth summing point 520 to form the individual adjustment rate R.sub.of.

[0130] The individual adjustment rate R.sub.of is finally added at the first summing point 506 to the collective adjustment rate R.sub.C, thus resulting in the setpoint adjustment rate R.sub.S, i.e., the total setpoint adjustment rate. Said setpoint adjustment rate R.sub.S is then entered into the operating control block 502 which has previously also produced the collective pitch rate R.sub.C. This operating control block 502 therefore carries out a plurality of functions, i.e., more functions than the operating control block 402 of FIG. 4. The second summing point 408 of FIG. 4 can also be realized analogously in the operating control block 502 of the structure of FIG. 5. At any rate, the operating control block 502 interacts with the wind power installation 512, or it is finally also part of the wind power installation 512, and can therefore both intervene in a controlling manner and also receive, evaluate and transmit measurement values.

[0131] Therefore, loads are detected, are taken into consideration in respect of pitching and yaw moment, an overall offset function for determining the offset angle is produced depending thereon and, depending thereon, the individual blade adjustment is carried out. The individual blade adjustment is undertaken by stipulating an individual adjustment rate R.sub.of which depends on the feed forward control 518 and the offset feedback controller 516. It is then added to the collective pitch rate R.sub.C in order then to obtain a setpoint adjustment rate R.sub.S. Said setpoint adjustment rate R.sub.S then takes into consideration both the blade setting for the general system control and the individual load reduction.

[0132] FIG. 6 illustrates such an offset function f(t). It is plotted here depending on the rotor angle Φ and is clearly cyclical through 360°. It can be considered to be a sine function.

[0133] It does not pass through the zero point, but rather intersects the abscissa during the angular displacement ϕ. The angular displacement is relative to a reference angle and can be considered here to be zero.

[0134] To this extent, FIG. 6 shows the offset function as a profile of the offset angle α.sub.of. An amplitude limit value α.sub.max can be provided for the offset angle α.sub.of. For this, a horizontal dashed line is also shown. If the offset function f(t), i.e., the offset angle α.sub.of, reaches said amplitude limit value α.sub.max, the offset function f(t) would have to be cut off, which is illustrated by the function partial section as in the diagram. The dashed line profile of the offset function f(t), α.sub.S′, may not be implemented.

[0135] However, it is proposed not to cut off the offset function, as is illustrated by the section as, but rather to interrupt the feed forward control for the moment. During the interruption, the measurement value detection and evaluation can continue to be carried out, i.e., can proceed normally. Furthermore, control of the offset angle can also be active, but the feed forward control, and therefore the connection of the feed forward control adjustment rate, is temporarily deactivated.

[0136] For illustrative purposes in the sequence diagram of FIG. 5, only the feed forward control 518 is therefore deactivated. The entire offset block 564 can continue here to calculate the offset function f(t), despite interruption of the individual blade adjustment, and it can then be determined whether or not the amplitude limit value α.sub.max is still reached or would still be reached. The feed forward control 518 can then be correspondingly taken into operation again.

[0137] 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.