METHOD FOR OPERATING A WIND TURBINE, WIND TURBINE, AND COMPUTER PROGRAM PRODUCT

Abstract

The invention relates to a method for operating a wind turbine, to a wind turbine designed to carry out the method, and to a computer program product. The method for operating a wind turbine comprising a rotor with rotor blades that can be angularly adjusted via a turbine controller, in which a state variable that reflects the current thrust of the rotor is detected, has the following steps: a) ascertaining a short-term average value of the state variable; b) ascertaining the difference between the short-term average value of the state variable and the detected current state variable; c) ascertaining a first target blade angle correction value from the ascertained difference; and d) taking into consideration the target blade angle correction value while adjusting the blade angle by means of the turbine controller.

Claims

1. A method for operating a wind turbine comprising a rotor with rotor blades of which the angle can be adjusted by means of a turbine controller, in which a state variable which reflects the current thrust of the rotor is detected, comprising the steps of: a) determining a short-term mean value of the state variable; b) determining a difference between the short-term mean value of the state variable and the detected current state variable; c) determining a first target blade angle correction value from the determined difference; d) the turbine controller taking into account the first target blade angle correction value for the blade angle adjustment.

2. The method of claim 1, wherein, parallel to steps a) to c), a second target blade angle correction value is determined from the gradient of the state variable and is combined with the first target blade angle correction value.

3. The method of claim 1, wherein the detected state variable is the current rotor blade loading which is detected in the form of blade bending torques, at the rotor blade root.

4. The method of claim 1, wherein the detected state variable is the current rotor torque.

5. The method of claim 1, wherein the short-term mean value is determined over a moving time period of from 3 to 20 s.

6. The method of claim 1, wherein the detected state variable is filtered before determining the short-term mean value and the detected current state variable for the difference calculation is the filtered state variable.

7. The method of claim 1, wherein determining the first target blade angle correction value comprises multiplying the determined difference by a gain factor.

8. A wind turbine comprising a rotor with a plurality of rotor blades of which the blade angle can be set, which rotor is arranged in a rotatable manner on a nacelle which is arranged in a rotatable manner on a tower and which rotor is connected by means of a drive train to a generator, which is arranged in the nacelle, for converting wind energy acting on the rotor into electrical energy, and comprising a turbine controller for controlling the wind turbine and its components, characterized in that wherein the turbine controller is designed to carry out the method as claimed in one of the preceding claims of claim 1.

9. A computer program product comprising program parts which, when loaded in a computer, preferably the turbine controller of a wind turbine, are designed to carry out the method of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The invention will now be described by way of example on the basis of a preferred embodiment with reference to the appended drawings, in which:

[0032] FIG. 1: shows a schematic illustration of the nacelle of a wind turbine according to the invention which is designed to carry out the method according to the invention; and

[0033] FIG. 2: shows the basic diagram of a possible first implementation of the method according to the invention; and

[0034] FIG. 3: shows the basic diagram of a possible second implementation of the method according to the invention.

DETAILED DESCRIPTION

[0035] FIG. 1 schematically illustrates the nacelle 2 of a wind turbine 1 according to the invention which is therefore designed to carry out the method according to the invention. The wind turbine 1 comprises a rotor 3 with a total of three rotor blades 5 which are fastened in a rotatable manner to a rotor hub 4 by means of blade angle adjusting devices 5′. The rotor 3 is arranged in a rotatable manner on the nacelle 2 which, in turn, is arranged such that it can rotate about a vertical axis on a tower 6 by means of an azimuth drive 14.

[0036] The rotor hub 4 is connected by means of a rotor shaft 7, with an interposed transmission 8, to a generator 9 for converting wind energy acting on the rotor 3 into electrical energy. The power-transmitting components ranging from the rotor 3 to the generator 9—that is to say the rotor shaft 7 and the transmission 8 in particular—form the drive train 10.

[0037] In the illustrated exemplary embodiment, the generator 9 is a doubly fed asynchronous generator, in which a portion of the power generated is conducted directly and another portion of the power is conducted via a converter 11 and a switching element 12 to a transformer (not illustrated) located at the base of the tower 6 and is fed from there into a public power supply network.

[0038] Furthermore, a brake 13 is provided between the transmission 7 and the generator 9, it being possible to brake a rotational movement of the drive train 10 and to stop the rotor 3 as required using said brake. Furthermore, measurement sensors 14 for determining the rotor rotation speed or the rotation speed of the shaft 7 are provided between the transmission 8 and the generator 9. Measurement sensors 15 for determining the rotor blade bending torques are provided on the rotor blades 5 in the region of the connection to the rotor hub 4.

[0039] The wind turbine 1 and all of its components are controlled by the computer-based turbine controller 20. For this purpose, all of the measurement values detected in the wind turbine 1 and also, via a data line 21, target values, for example from a network operator, are supplied to the turbine controller 20 and, with the aid of control algorithms known to a person skilled in the art in principle and stored in a memory 22, converted into control signals which are then, in turn, output to the various components of the wind turbine 1. The turbine controller 20 determines in a first part, on the basis of the available information, target values for individual parameters, which can be controlled by it, in respect of the operation of the wind turbine 1, these target values then being converted by other parts of the turbine controller 20 in such a way that the corresponding actual values correspond to the target values.

[0040] According to the invention, the turbine controller 20 is designed to carry out the method according to the invention described in more detail below, for which purpose a computer program product designed for this is stored in the memory 22 and executed by the turbine controller 20.

[0041] FIG. 2 shows a basic diagram of a first implementation of the method according to the invention in the turbine controller 20. Here, the illustration is limited to the part of the turbine controller 20 which is essential for carrying out the method.

[0042] A state variable, which reflects the current thrust of the rotor 3, is determined in function block 100. For this purpose, the rotor blade bending torques M.sub.Blade1 . . . 3 detected by the measurement sensors 15 on the individual rotor blades 5 are added up in the functional element 101. Here, calibration of the measurement values, so that these provide the actual absolute value of the rotor blade bending torques, can be dispensed with in principle. Specifically, the method according to the invention is not based on the absolute values, but rather only on the relative change in the state variable. The state variable determined from the rotor blade bending torques is supplied to a filter 102 in order to filter out radiofrequency interference and noise of the measurement sensors 15.

[0043] The state variable determined in this way is then supplied to the function blocks 200 and 300 in parallel.

[0044] A short-term mean value of the state variable supplied is determined by the functional element 201 in function block 200, wherein the time period for calculating the short-term mean value is 10-12 s.

[0045] The difference between the short-term mean value determined by the functional element 201 and the current state variable made available by the function block 100 is determined in element 202.

[0046] The difference determined in this way is multiplied by a gain factor in the functional element 203, this then producing a first target blade angle correction value.

[0047] In parallel to the function block 200, in function block 300, the gradient of the state variable is determined by the functional element 301, then smoothed by the functional element 302, before finally being multiplied by a gain factor in the functional element 303, this then producing a second target blade angle correction value.

[0048] The first target blade angle correction value from the function block 200 and the second target blade angle correction value from the function block 300 are added up in element 400 and then fed to the turbine controller 20 in order to be taken into account for the blade angle control. The determined target blade angle correction value according to the invention can be taken into account, for example, by simple addition to the blade angle target value, particularly when the turbine controller 20 determines a blade angle target value which is then implemented by a part of the turbine controller 20 intended for that purpose.

[0049] FIG. 3 shows a basic diagram of a second implementation of the method according to the invention in the turbine controller 20. This basic diagram corresponds to that from FIG. 2, apart from the state variable used, and for this reason reference is made to the explanations provided there.

[0050] In the implementation in FIG. 1, the rotor torque, that is to say the torque currently transmitted by the rotor to the drive train, is determined by the function block 100′ as the state variable. This rotor torque is calculated by the functional element 101′on the basis of the rotation speed co measured by the measurement sensors 14 and also the electrical power P ultimately generated by the generator and is then filtered by the element 102′, before being made available to the function blocks 200 and 300.

[0051] The function blocks 200 and 300 are identical to those from FIG. 2. It may only be necessary for the gain factors in the functional elements 203 and 303 to be matched to the changed state variable in order to be able to determine an effective target blade angle correction value.

[0052] As is immediately apparent from the above description, the process of determining the target blade angle correction value is not based on the absolute value of the state variable at any time, but rather only on the relative change over time. As a result, the method according to the invention is extremely robust, for example to slow drifts of the values determined by the measurement value sensors.