Blade pitch angle control for wind turbine

p0001The invention concerns a wind power plant with a rotor with at least one rotor blade for converting the flow energy of the wind into mechanical energy, with an adjusting device for individual adjustment of at least one rotor blade, with a generator for converting the mechanical energy of the rotor into electrical energy and with a working connection between the rotor and the generator to transfer the mechanical energy of the rotor to the generator.

p0002Such wind turbines are part of the prior art. For example, shows the German reference book "<nplcit id="ncit0001" npl-type="b"><text>Wind turbines "by Erich Hau, Springer-Verlag, 2nd ed., 1996, pages 52, 175, 222-242, 269, 320 such Windenergieanlag</text></nplcit>en. These known wind turbines can be adjusted using a Rotorblatteinstellwinkelregelung the rotor speed and power output control. Moreover, the known Rotorblatteinstellwinkelregelung serves to protect against overspeed of the rotor at high wind speeds or during a power failure, in which the generator torque due to unexpected loss. In both cases, the aim is to protect the wind turbine against destruction by too high rotating rotor.

p0003As further prior art reference is made to <patcit id="pcit0001" dnum="US4193005A"><text>US-A-4,193,005</text></patcit> pointed. This document discloses a wind turbine with a rotor, which is connected via a gear to a generator, in which by means of a converter (transducer), the shaft connecting to the gearbox and the generator attached, a torque is measured.

p0004There are essentially two ways to bring about using the blade adjustment to reduce the rotor speed: on the one hand allows the blade pitch in the direction of smaller aerodynamic angles reduce, thereby reducing the power consumption of the rotor. On the other hand, it is possible to form larger adjustment angles the critical aerodynamic angle of attack to achieve by adjusting the Rotorblatteinstellwinkels called stall condition. The latter option has the advantage of adjustment shorter path, however, has the disadvantage that the flow separation (stall) is associated with high loads on the rotor and the entire wind power plant. However, both settings in common is that they take into account only a medium, acting on the entire wind turbine wind speed or a certain limit rotor speed as a start signal for the blade angle setting.

p0005Belde aforementioned possibilities of the prior art do not consider that it may occur, especially in a large rotor diameter in an uneven distribution of wind conditions on the rotor surface. This in turn has different loads on individual rotor blades, as well as asymmetric loads on the drive train of the wind turbine, that is the hub, the drive shaft and the respective bearings. Such differences of asymmetric loads occur not only until a certain rotor speed or a certain wind speed, but also find continuously during normal operation of the wind turbine instead. The previously known from the prior art can not respond to Blattwinkeiregelung Windgeschwindgkeitsschwankungen and related Lastsohwankungen in the rotor region, therefore, as in the known systems a single, synchronous adjustment of the rotor blades will take place.

p0006Although in newer facilities (see especially pages 238 of the above reference book) has been proposed for an individual electric adjustment Each individual rotor blade; However, that proposal is assuming an average wind speed acting on the wind power installation. This and further assuming that the wind speed increases with height, then a fixed, circumferential cyclical correction of Rotorblatteinstellwinkels is proposed to compensate for the changing loads on the increase in wind speed with height at least partially can. In this Rotorblatteinstelltechnik it is disadvantageous that the pitch of the rotor blades is fixed and therefore can not respond to local and temporary adjustments to the wind speed in a portion of the rotor. Also with this proposal, therefore, takes place at about the rotor face seen local peaks in the wind speed instead of an asymmetrical and thus lebensdauerverkürzende load the components of Windanergieanlage.

p0007The object of the invention is therefore to avoid the above problems and to provide a wind power plant is available, in which the loads are reduced, which can occur due to local and transient spikes in the wind speed in some areas of the rotor surface.

p0008<b>The object is erfingdungsgemäß solved with the features of claim 1 and 22nd Advantageous developments are described in the dependent claims.</b>

p0009According to the invention in a wind turbine of the type mentioned measuring means are provided which determine the instantaneous stress of a part of the wind turbine, control means are provided which determine a desired for the instantaneous loading position of at least one rotor blade and adjust the rotor blade by means of the adjusting device correspondingly, and connection means are provided, which connect the adjusting device and the measuring means to the control means.

p0010By Winderiergieanlage invention it is possible, to determine the wind turbine system for instantaneous, at only one Tell the wind power plant locally applied stress by measuring means with the aid of the adjusting device for individual adjustment of at least one rotor blade, agreed with the aid of control means. Thus, it is advantageously achieved that local peaks are avoided in the load of the rotor blades, the hub, final drive and the bearings used. This in turn means that the lifetime of the wind turbine increased or is not unconsciously shortened because asymmetric and the life shortening stresses of parts of the wind turbine can be largely avoided.

p0011Moreover, it allows the wind turbine according to the invention optimal use of the instantaneous distribution of wind speeds on the rotor surface and thus contribute to an increased power output of the wind turbine, since all blades are always driven with the desired and thus optimum blade angle and therefore the efficiency of each rotor blade towards the efficiency of the wind turbines of the prior art increases.

p0012It is particularly preferred that the position of the rotor blade or the rotor blades is adjusted continuously to the instantaneous load of the wind turbine is. In this way it can be ensured that the wind turbine is driven continuously in the optimum operating range and at the same time before load peaks, triggered by locally available in the rotor field peaks in the wind speed, protected.

p0013In a preferred embodiment of the invention, the measuring means determines for determining the local stress of a rotor blade at a rotor blade prevailing wind speed. To this end, the measuring means preferably comprise an attached on the rotor blade anemometer. The fact that the anemometer is arranged directly on the rotor blade, a very precise control of the angular position of the rotor blade in response to an increased or lower wind speed is possible. For the measurement of the wind speed directly to the place which is home to an adjustment of the wind power plant, namely directly on to be adjusted rotor blade, a fast and accurate adjustment of the rotor blade angle position to local changes in wind speed is possible.

p0014A further preferred embodiment is characterized in that the measuring means determine a prevailing in a partial section of the rotor portion mechanical load. In this embodiment is given by the direct determination of the applied in a partial section of the rotor mechanical stress to the control means precise information that will help them to determine when weighed against the geometry, load and / or material data a desired position of at least one adjustable rotor blade ,

p0015Particularly advantageous in this embodiment, when the measuring means detect a prevailing in the adjustable rotor blade mechanical load. For while the load is determined directly in the rotor blade, can similarly to the above-mentioned direct determination of the wind speed at the rotor blade, a very precise information about the wind speed profile over the rotor surface are obtained. With such detailed information, the control means are then able to control, a particularly accurate reaction of the adjustment so that an existing load peak can be broken down very quickly in a partial section of the rotor.

p0016Another embodiment of the invention having a rotor hub for receiving the rotor blades has measurement means for measuring an existing mechanical load in the rotor hub. In this embodiment also allows a quick adjustment of the rotor blades to the changed load situation make. The same applies to embodiments with an axle journal for supporting the rotor, in which the measuring means determine a prevailing in the journal load and connects to a wind power installation with a drive shaft, the rotor and the generator directly or via a gear, in which the measuring means in one of the drive shaft or identify predominant load in the bearings of the drive shaft or the journal. All of the aforementioned embodiments allow an accurate determination of the local load situation in the rotor area and hence an accurate control of the adjustment means of the control means. It is particularly preferred that the measuring means for measuring the mechanical load stretch marks have which are attached to the respective loaded parts of the wind turbine. That is, the stretch marks on the rotor blade in the interior of the rotor blade on the rotor hub or within the rotor hub on the axle journal or in the interior of the journal, on the drive shaft or in the interior of the drive shaft or may be attached to the bearings. In all the aforementioned types of installation as a simple determination of the existing mechanical stress and thus the invention individual adjustment of the rotor blade is possible.

p0017A further preferred embodiment of the invention comprises measuring means which determine a prevailing on the rotor blade to be adjusted angle of attack of the wind. It is thus advantageously possible to determine the wind direction of the oncoming wind relative to be adjusted rotor blade. With this measured value the control means may respond to an existing in a partial area of ​​the rotor wind direction change.

p0018In particular, in conjunction with the load measuring means mentioned above to get the control means a very accurate picture of the current wind conditions on the rotor surface: by the load measuring means, the control means an absolutely existing load taken into account and by the measuring means for determining the angle of incidence can moreover also - taking into account the actual rotor blade position - accurate determination of the size of the angle to be adjusted to be made. An accurate adjustment in rapidly changing wind conditions is thus advantageously ensured by the combined use of Anströmwinkelmessung and load measurement in the rotor blades. It is particularly preferred to carry out the measurement of the angle of attack using a button located on the rotor blade wind vane.

p0019A further preferred embodiment of the invention is characterized in that a part section of a rotor blade can be adjusted asynchronously to at least one further adjustable partial section of another rotor blade. Thus, the construction cost can be reduced especially for large rotor diameters, by preference, the outer section of the rotor blade, since the power generation of the rotor largely focused on the outer blade section, is designed to be adjustable.

p0020In an advantageous embodiment of the invention can be desired for a specific instantaneous loading position of the rotor blades or through related to the control means input means pretend. In this way, the wind turbine according to the invention on site can be customized after installation of possibly unforeseen wind conditions or after a repair to changing material thicknesses or modified airfoils.

p0021Especially advantageous has proven to tap the actual value of the rotor blade angle position of an adjusting gear, which forms the adjusting device with an adjusting motor. It is particularly advantageous if the control means make the adjustment of the rotor blade substantially simultaneously with the recording of the measured values ​​of the stretch marks, the anemometer or wind vane by comparison with the actual value of the adjusting means of the adjustment. Such an instantaneous response to load changes in the area of ​​the rotor blades, an effective reduction of harmful stress or weight on one side of the rotor is ensured.

p0022An advantageous method for adapting a wind energy plant at prevailing only in a local section of the wind turbine current stresses is characterized that of measuring equipment the instantaneous loading of part of the wind power installation is detected and determined by control means desired for the instantaneous loading position of at least one of the rotor blades is and that is adjusted according to the corresponding rotor blade by means of the adjustment device, wherein the adjusting device and the measuring means are connected to the control means with the aid of connecting means. This simple method can be an effective increase of lifetime and efficiency of the wind turbine according to the invention achieve.

p0023Further advantageous embodiments are described in the subclaims.

p0024An embodiment of the invention will now be described with reference to the accompanying drawings, in which:<ul><li><figref idrefs="f0001">figure 1</figref> a partial section of a wind power plant according to the invention is;</li><li><figref idrefs="f0002">figure 2</figref> a front view of a wind power plant according to the invention is; and</li><li><figref idrefs="f0003">figure 3</figref> a block diagram illustrating the control of the adjustable rotor blade, in a preferred embodiment of the invention.</li></ul>

p0025The <figref idrefs="f0001">figure 1</figref> shows a wind turbine 1 in a partial section. The wind turbine 1 rests on a (only partially shown) tower 2. At the upper end of the tower 2 is a housing 4 placed on the tower. Below the housing 4 is a tower attached to the service platform 6. The housing 4 comprises a (not shown) and a generator shown in phantom in its control unit 8 (in the drawing enclosed, shown on the right) rear part. The generator is located behind a bulge 10 of the housing 4 and is flanged by means of connecting elements 12 with its (not shown) to the rotor hub rotor fourteenth The rotor hub 14 and the (only partially shown) rotor blades 16 together form the rotor 18. The rotor 18 is mounted with its hub 14 via bearings 20 on a journal 22nd The journal 22 extends through an opening provided in the rotor hub 14 port 24 through the rotor hub 14 therethrough. The journal 22 is tower mutually connected within the housing 4 with the tower. 2 From the substantially vertically drawn up Tower 2 of the journal 22 relative to the horizontal extends from slightly tilted upward. The axle journal 22 is connected to the (not shown) stator of the generator and extends through the rotor of the generator and through the opening 24 of the rotor hub 14 therethrough and after its exit from the opening 24 on the side remote from the tower 2 side of the rotor 18 completed by a final piece of 26th

p0026Again, perpendicular to the axis of the journal 22, the blades 16 extend outwardly. The rotor blades 16 pass through openings 28 in the front housing 30 through. The front housing 30 is movable fixed relative to the connected to the tower 2 housing 4 and fixed to the hub 14th

p0027The rotor blades 16 are connected via a flange to the rotor hub 14 for rotation about its longitudinal axis. A variable displacement motor 34 is attached to the flange 32 and adjustable via an adjusting mechanism 36, the rotor blade 16. The adjustment motor 34 and the adjusting gear 36 are via electrical (in<figref idrefs="f0003">Fig. 3</figref> shown) links 50 and 46 connected to the control device eighth The front housing 30 encloses the rotor hub 14 with the bearings 20, the flange 32, the servomotor 34 and the adjusting mechanism 36 weathertight. The front housing 30 has a cross-sectionally substantially semi-spherical shape.

p0028to stretch marks are located on the axle journal 22 38. At the rotor hub 14 are stretch marks 40. The stretch marks 38 are connected via an electrical connection 42 to the control unit. 8 The stretch marks 40 are a (in<figref idrefs="f0003">Fig. 3</figref> shown) electrical connection 48 connected to the control device eighth

p0029The <figref idrefs="f0002">figure 2</figref> showing parts of the wind turbine 1 of <figref idrefs="f0001">figure 1</figref> as seen from the rotor side. <figref idrefs="f0002">figure 2</figref> shows the tower 2 with the rotor hub attached to its tip 14 from the hub 14 in a star-shaped three rotor blades 16 from. The rotor blades 16 are connected via the flange 32 to the rotor hub fourteenth For clarity of illustration, the front housing 30, the adjusting motor 34, the adjusting gear 36, the axle journal 22, the opening 24 and the end cap 26 from the<figref idrefs="f0001">Fig. 1</figref> not shown.

p0030At the rotor blades 16 wind vanes 44 are mounted for measuring the angle of incidence of the incident on the rotor blades 16 wind. The wind vanes 44 are (in<figref idrefs="f0003">Fig.3</figref> shown) electrical connection 52 to the control unit 8 (<figref idrefs="f0001">Fig. 1</figref>) connected.

p0031On the basis of the block diagram of <figref idrefs="f0003">figure 3</figref> the operation of the wind power plant according to the invention will be described below.

p0032During operation of the wind turbine 1, the rotor 18 rotates about the axis of the journal 22. In this case, the rotor blades 16 in a specific, with the aid of the control unit 8, the adjusting motor 34 and the adjusting gear 36 predetermined angular position relative to the plane in which rotate the rotor blades 16 , the rotor plane. The instantaneous angle α_currently of the rotor blades 16 relative to the rotor plane is the control device 8 received from the adjusting mechanism 16 as the actual value of the instantaneous position of the rotor blade 16 via an electrical connection 46th Simultaneously, the control unit 8 obtains from the strain gauges 38 which are attached to the axle journal 22, measured values ​​relating to the instantaneous load of the journal 22 via the line 42 ( "load signal journal" the<figref idrefs="f0003">figure 3</figref>). Also simultaneously with the transmission of the current position angle of the rotor blades 16 is replaced by the control unit 8 of the stretch marks 40 on the rotor hub via line 48 Observations on the current load on the rotor hub 14 ( "load signal hub" of<figref idrefs="f0003">figure 3</figref>). If the control unit 8 by means of stretch marks 38, 40, a one-sided loading of the rotor fixed, so are the control unit 8, taking into account the current position angle α_currently the rotor blades 36 and the current, determined from the wind vane 44 angle of attack β a signal α_new via line 50 to the α adjustment motor 34 for adjusting the corresponding blade 16 by the difference_new - α_currently,

p0033The fact that the control unit 8 continuously measured values ​​of stretch marks 38 and 40 receives and almost instantaneously in consideration of also continuously transmitted to the control unit 8 via the line 52 flow angle β the work command to the servomotor 34 for setting a new angle of the rotor blades 16 out there that finds on-line with a change in the load conditions in the region of the rotor to adapt the position of the rotor blades 16 instead and thus an on-line compensation of unbalanced loads on the rotor 18th

p0034As an alternative to the measurement of the instantaneous load of the wind turbine by stretch marks on the rotor hub and axle pin a load measurement directly on the rotor blades is possible by corresponding stretch marks.

p0035Finally, it should be noted that the various signals (ie "load signal hub" 40, "Last Signal journals" 38, "Current angle α_currently"46 and" angle of attack β "53), which are used to determine the ideal blade angle, can be either jointly or alternatively used.