Description:TITLE OF INVENTION

A METHOD FOR DETERMINING WIND DATA IN A WIND PARK

FIELD OF INVENTION

The present invention is directed to a method for determining wind data in a wind park, a method of operating a wind park with determined wind data and further to a wind park as well as a computer program product.

BACKGROUND

In known prior art typically LIDAR systems or met masts are used measuring wind data in the wind farm.

WO 2019/166236 A1 discloses a method of estimating free-stream inflow at a downstream wind turbine of a wind park. This method comprises the step of se-lecting upstream wind turbine based on a currently determined wind direction, from plural candidate wind turbines previously defined specifically for the down-stream wind turbine. Then using determining equipment of the selected upstream wind turbine to determine the free-stream inflow at the upstream wind turbine and correcting it with a time delay calculated from the wind speed, wind direction and the distance between the upstream wind turbine and downstream wind turbine. Further disclosed is that for each of the downstream wind turbines, plurality of candidate wind turbines may have previously been defined especially for the con-sidered downstream wind turbine. These candidate wind turbines may all be pe-ripheral wind turbines, i.e. wind turbines which are on the outer border of the wind park, e.g. wind turbines which surround or encircle all other wind turbines of the wind park. The number of the plural, pre-selected candidate wind turbines for the downstream wind turbine may be less than the number of all wind turbines in the wind park. Thus, an extensive and time-consuming search for the appropriate upstream wind turbine may not be necessary.

OBJECT OF THE INVENTION

The prior art has several disadvantages. Wind turbines in a wind park are placed so that they influence each other. Wind turbines placed downstream experience tur-bulences from the upstream wind turbine. Hence, the wind data measurement from downstream wind turbine is disturbed. Often met masts for measuring wind data are not or rare available for reliable wind data measurement for the whole wind park. Additional LIDAR systems are expensive and not reliable under all conditions.

Apart from the above drawbacks, control features in a wind park controller, e.g. wake control, requires exact and accurate wind data like wind speed, wind direc-tion and turbulence intensity in real time. Thus, an object of the present invention is to provide a method for determining wind data with increased accuracy.

SUMMARY OF THE INVENTION

This object is solved by a method for determining wind data in a wind park ac-cording to a first aspect of the invention. According to the invention it was recog-nized that if wind data are determined in a two-step approach from plurality wind turbine measurements of the wind park then the accuracy of the wind data can be increased. In a first step the wind direction is taken as average from majority or all wind turbines within the wind park to determine the global wind direction. This global wind direction only serves to determine the wind turbines standing in free wind stream. In a second step the wind speed and direction of free standing wind turbines are used for determining global wind speed and direction used in control features of the wind park. In that way the wind data will be more accurately de-termined from wind turbine sensor data.

According to the invention the method for determining wind data in a wind park comprises the steps of:
- determining global wind direction of a wind park,
- determining free standing wind turbines based on determined global wind direction and
- determining wind data of the wind park based on wind data measurements of determined free standing wind turbines.

Advantageously, preferred wind data are wind speed, turbulence intensity or wind direction or a combination thereof.

According to a preferred embodiment of the method for determining wind data in a wind park, the method comprises measuring wind direction, via at least one wind vane, from majority of wind turbines within the wind park for determining global wind direction of the wind park.

According to a preferred embodiment of the method for determining wind data in a wind park, the method comprises measuring wind speed, via at least one ane-mometer, of determined free standing wind turbines for determining wind data of the wind park.

According to a more preferred embodiment of the method for determining wind data in a wind park, the method comprises calculating average wind speed based on measured wind speed of determined free standing wind turbines for determin-ing global wind speed of the wind park.

According to a more preferred embodiment of the method for determining wind data in a wind park, the method comprises calculating average wind speed takes place continuously or periodically. Advantageously, the periodical calculation takes place in a time range of 10 min, 1 min, 30 s, 10 s, or 5 s.

According to a preferred embodiment of the method for determining wind data in a wind park, the method comprises determining turbulence intensity based on de-termined wind data of the wind park based on wind data measurements of deter-mined free standing wind turbines.

According to a preferred embodiment of the method for determining wind data in a wind park, the method comprises measuring wind speed of determined free standing wind turbines for determining wind data of the wind park and calculat-ing the turbulence intensity based on measured wind speed of determined free standing wind turbines.

In particular the more free standing wind turbine can be determined the more ac-curately is the determined wind data, e.g. wind speed. Even if simulations has shown that best results are provided with ten and more wind turbines, the present invention works with less than ten wind turbines.

A further aspect of the present invention is directed to a method for controlling a wind park.

According to the invention the method for controlling a wind park comprises the step of using the method for determining wind data in a wind park comprising the steps of:
- determining global wind direction of a wind park,
- determining free standing wind turbines based on determined global wind direction and
- determining wind data of the wind park based on wind data measurements of determined free standing wind turbines.

According to a preferred embodiment of the method for controlling a wind park, the method comprises that the determined wind data of the wind park is used as control input for at least one of the wind turbines of the wind park.

According to a preferred embodiment of the method for controlling a wind park, the method comprises that a park controller is configured for wake control.

According to a preferred embodiment of the method for controlling a wind park, the method comprises operating set-points are based on determined wind data determined by the method for determining wind data in a wind park comprises the steps of:
- determining global wind direction of a wind park,
- determining free standing wind turbines based on determined global wind direction and
- determining wind data of the wind park based on wind data measurements of determined free standing wind turbines.

A further aspect of the present invention is directed to a wind park.

According to the present invention the wind park comprises a plurality of wind turbines having a park controller configured for executing the method for deter-mining wind data in a wind park comprises the steps of:
- determining global wind direction of a wind park,
- determining free standing wind turbines based on determined global wind direction and
- determining wind data of the wind park based on wind data measurements of determined free standing wind turbines.

According to a preferred embodiment of the wind park, the park controller is con-figured to send determined wind data of the wind park, based on wind data measurements of determined free standing wind turbines as control input for at least one of the wind turbines of the wind park.

A further aspect of the present invention is directed to a computer program prod-uct.

According to the present invention a computer program product comprising in-structions which, when the program is executed by a computer, cause the comput-er to carry out the steps of the method for determining wind data in a wind park comprises the steps of:
- determining global wind direction of a wind park,
- determining free standing wind turbines based on determined global wind direction and
- determining wind data of the wind park based on wind data measurements of determined free standing wind turbines.

The computer program product, which enables a data processing device, once the computer program product is executed on the data processing device, and is pref-erably stored in a storage device, to perform a method of controlling a wind tur-bine as described above.

The present invention provides several advantages, namely
- wind data can be more accurately determined by using wind data of free standing wind turbines;
- this accurately determined wind data can be used as control input for several wind park control schemes as well as control input for the wind turbines of the wind park;
- no need for additional equipment like met masts and/or LIDAR systems and
- the method can be updated in any existing wind park.

BRIEF DESCRIPTION OF DRAWINGS

The invention will now be explained in more detail with respect to exemplary em-bodiments with reference to the enclosed drawings, wherein:

Figure 1 shows a wind turbine according to prior art,

Figure 2 shows a part of a wind park with wind direction and

Figure 3 shows a part of a wind park of Fig. 2 with different wind direction.

The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompany-ing drawing figures.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 depicts a schematic view of a wind turbine 1 with a tower 2 and a nacelle 3. Depending on given requirements the wind turbine 1 can be used for offshore or onshore applications. The nacelle 3 is rotatable mounted on the tower 2 which is indicated by a double arrow at the tower 2. The nacelle 3 incorporates a number of components like a drive train chain 4 comprising a rotor shaft 5 (also known as slow-speed-shaft) connecting a rotor 6 with a gear box 7. A high-speed-shaft 8 connects the gear box 7 with a generator 9. The generator 9 is connected with a plurality of electrical components indicated by box 10. Further the nacelle 3 com-prises a yaw system 11 for rotating the nacelle 3 indicated by double arrow at tower 2. The rotor 6 comprises three rotor blades 12 which are mounted to a hub body (not shown). Latter is connected to the rotor shaft 5 of the drive train chain 4. The rotor blades 12 are adjustably mounted on the hub body indicated by dou-ble arrows at the rotor blade 12. This is realized by means of pitch drives 13, said pitch drives (not shown) being part of a pitch system 13. The pitch system controls the rotor speed to given set points. By means of pitch-drives, the rotor blades 12 may be moved about a rotor blade axes into different pitch positions which is in-dicated by double arrows at the rotor blade 13. Said rotor blade 6 axis extends in an axial direction of the rotor blades 13. Each rotor blade 13 is connected to the hub body via its blade bearing (not shown). The nacelle 3 is covered by a nacelle cover 14. The hub body is covered by a spinner 15, wherein the hub body and spinner 11 forming a hub 16. On top of the nacelle 3 is arranged at least one wind vane 17 for determining the wind direction and at least one anemometer 18 for determining the wind speed.

Fig. 2 depicts a part of a wind park 19 with seven wind turbines 1a to 1g which are wind turbines described according to Fig. 1. Depending on the installed capac-ity, in other embodiments the wind park can have more or less than seven wind turbines. The wind park can comprises at least one wind turbine up to several hun-dreds of wind turbines. For determining the global wind direction, indicated by a grey arrow, of the wind park 19 the wind direction will be measured from at least a majority up to all wind turbines 1a to 1g via the wind vane 17 of the respective wind turbine 1. In context of the present invention the global wind direction is the main wind direction measured within the wind park 19, measured by a majority, more than 50% of the wind turbines up to all wind turbines of the wind park 19. Depending on measured wind direction a wind park controller 21 determines the global wind direction, e.g. by calculating average wind direction. According to the shown embodiment the global wind direction is indicated by gray arrow.

In general, each wind turbine 1 of the wind park 19 extracts energy from the wind. There are several indicators available for determining wind turbines which are influenced by another wind turbine, namely wind speed, blade bending mo-ments, power production, turbulence intensity or others. The wind speed, meas-ured by the anemometer 18 of the respective wind turbine 1, is reduced within the downstream area 20 of the respective wind turbine 1. The wind within the down-stream area 20 can also tend to be more turbulent. The reduced wind speed within the downstream area 20 corresponds to a reduced power production, in particular active power production, of any wind turbines 1 which are influenced by the downstream area. The wind continues further downstream from the wind turbines 1, the reduced wind speed disperses until the wind speed again reaches its free stream velocity. This causes depending from the size of the wind park 19 and lo-cation of the respective wind turbines 1 that a free standing wind turbine can be located inside the wind park 19 and is not narrowed to the first row according to the wind direction. For example comparing the wind speed of all wind turbines free standing wind turbines and downstream wind turbines can be determined. Free standing wind turbines measuring in average a higher wind speed than down-stream wind turbines. Same applies for the power production. Wind turbines 1 also cause additional turbulence in the flow. Therefore, each wind turbine 1 changes the inflow conditions of the wind turbines 1 that are nearby in their downstream area 20. This change not only leads to a reduction in the possible en-ergy yield, but also to an increase in the dynamic load on the structure. In case of turbulence intensity or blade bending moments will be considered that the turbu-lence intensity and/or blade bending moments of free standing wind turbines will be less than of downstream wind turbines. In other words the dynamic loads of downstream wind turbines are higher than the dynamic loads of the free standing wind turbines. The allocation of free standing wind turbines and downstream wind turbines changes if the wind direction turns.

According to Fig. 2, the free standing wind turbines will be determined depend-ent from the global wind direction. The wind park controller 21 has stored the layout of the wind park 19 and determines the free standing wind turbines with a look-up table comprising of the global wind direction and position of the wind turbines 1a to 1g within the wind park 19. In result the wind park controller 21 can determine all wind turbines which has no other wind turbine in front in wind direction. These are the free standing wind turbines 1a to 1d. This means that not only the first row of wind turbines of the wind park 19 can be determined as free standing wind turbines; instead also, of course depended on the global wind di-rection, wind turbines within the wind park 19 which are not influenced by a wind turbine in front are determined as free standing wind turbine (see wind turbine 1b in Fig. 3).

Alternatively, according to Fig. 2, depending on the global wind direction all free standing wind turbines will be determined via the wind park controller 21 con-nected with the wind turbines 1a to 1g. For this purpose several wind turbine pa-rameters can be used, like turbulence intensity, blade bending moment, wind speed, power production or structural loads or a combination there of. One or more of these wind turbine data will be measured respectively calculated and compared with wind turbine data of the other wind turbine 1. Free standing wind turbines measure a higher power production than downstream wind turbines. Up-stream wind turbines cause additional turbulence in the flow. Therefore, each wind turbine 1 changes the inflow conditions of the wind turbines 1 that are near-by in their downstream area 20. All necessary wind turbine parameters of each wind turbine 1 will be transmitted to the wind park controller 21. The wind park controller 21 compares the received wind turbine parameters of the wind turbine 1a with the remaining wind turbines 1b to 1g, the received wind turbine parame-ters of the wind turbine 1b with the remaining wind turbines 1a, 1c to 1g and so on. Depending on the received wind turbine parameters wind turbines 1 with higher or lower parameter values are the black marked free standing wind turbines 1a, 1b, 1c and 1d. For example the power production of the free standing wind turbines 1a to 1d is higher than the power production of the downstream wind turbines 1e to 1g. Alternatively the turbulence intensity and structural loads of the free standing wind turbines 1a to 1d are less than of the downstream wind tur-bines 1e to 1g.

In one preferred embodiment power production in predefined wind direction bins are measured by the wind turbines 1a to 1g and will be compared via the wind park controller 21. Latter compares the received power production values for each of the predefined wind direction bins of the wind turbine 1a with power produc-tion value of the remaining wind turbines 1b to 1g and the received power produc-tion values of the same wind direction bins of the wind turbine 1b will be com-pared with the remaining wind turbines 1a, 1c to 1g and so on. The wind turbines 1 with higher measured power production in a particular wind direction bin are the free standing wind turbines, the remaining wind turbines measuring lower power production because of the downstream area 20. In shown embodiment the free standing wind turbines are the blacked marked wind turbines 1a to 1d. Accord-ingly the wind turbines 1e to 1g are downstream wind turbines which are influ-enced by the free standing wind turbines 1a to 1d. The downstream areas 20a to 20d are indicated by the dashed lines behind the free standing wind turbines 1a to 1d.

After the free standing wind turbines 1a to 1d are determined, the wind data of the wind park 19 will be determined based on wind data measurements of free standing wind turbines 1a to 1d. Wind data are wind speed, turbulence intensity or wind direction or a combination thereof. Wind data of the wind park 19 will be determined based on the wind data of the free standing wind turbines 1a to 1d obtained with use of suitable sensors (not shown) of the respective wind turbine 1a to 1d. The determined wind data will be transmitted to the wind park control-ler 21 where the average wind data will be calculated. Calculating average wind data takes place continuously or periodically. The periodical calculation takes place in a time range of 10 min, 1 min, 30 s, 10 s, or 5 s It is also possible that the free standing wind turbines 1a to 1d determining wind data continuously and cal-culating average wind data of a predetermined time range and sending these wind data to the wind park controller 21 as input for calculating global wind data of the wind park 19.

In a preferred embodiment the wind speed of the wind park 19 will be determined based on the measured wind speed of the free standing wind turbines 1a to 1d with use of the anemometer 18 of the respective wind turbine 1a to 1d. The meas-ured wind speed will be send to the wind park controller 21 where the average wind speed will be calculated. Calculating average wind speed takes place contin-uously or periodically. The periodical calculation takes place in a time range of 10 min, 1 min, 30 s, 10 s, or 5 s It is also possible that the free standing wind turbines 1a to 1d measuring wind speed continuously and calculating average wind speed values of a predetermined time range and sending these wind speed values to the wind park controller 21 as input for calculating global wind speed of the wind park 19.

In another embodiment the wind data can be the turbulence intensity within the wind park 19. Therefore the wind speed of the wind park 19 is determined as de-scribed above. With this global wind speed of the wind park 19 the turbulence intensity can be calculated. Therefore several calculation methods known in prior art can be used. In result the global turbulence intensity can be used as input for the wind park controller 21 for controlling the wind park 19.

Fig. 3 depicts same wind park as shown in Fig. 2. The difference is that the wind direction has turned and consequently the allocation of free standing wind tur-bines and downstream wind turbines has changed. In result the wind turbine 1a is influenced by free standing wind turbine 1b and wind turbine 1c are influenced by wind turbine 1d, so wind turbines 1a and 1c are not a free standing wind tur-bines. Accordingly the wind data will be determined as described above based on wind data of the free standing wind turbines 1b, 1d and 1g. As can be seen the free standing wind turbine 1b stand in third row in wind direction and the free standing wind turbines 1d, 1g form the first row in wind direction.

The determined wind data of the wind park 19, e.g. average wind speed, will be used as input data for the wind park control scheme and/or as input data for the control scheme for the wind turbines 1 of the wind park 19. In preferred embodi-ment the wind data will be used for wake control.

According to one preferred embodiment, for determining global wind speed in a wind park 19 first the global wind direction will be determined. For this purpose the wind direction of all wind turbines 1a to 1g will be measured via the wind vane 17 of wind turbines 1a to 1g. The measured wind direction will be send to the wind park controller 21, who determines the major wind direction which is the global wind direction, indicated by a grey arrow, of the wind park 19. Based on the global wind direction free standing wind turbines will be determined by the wind park controller 21. Latter has stored the layout of the wind park 19 and de-termines the free standing wind turbines with a look-up table comprising of the global wind direction and position of the wind turbines 1a to 1g within the wind park 19. In result the wind park controller 21 can determine all wind turbines which has no other wind turbine in front in wind direction. These are the free standing wind turbines 1a to 1d. . According to Fig. 2 these are the wind turbines 1a to 1d. From these free standing wind turbines 1a to 1d the measured wind speed will be basis for calculating the global wind speed of the wind park 19. Therefore the wind park controller 21 receives continuously wind speed values from the free standing wind turbines 1a to 1d and based thereon calculates the average wind speed which is the global wind speed of the wind park 19. This global wind speed can be used as input for the wind park controller 19 as well as input for the wind turbine controller of wind turbine 1a to 1g for real-time control for several control schemes. One of this can be wake control.

The above described method for determining the global wind speed provides ac-curate wind speed in real-time. With this a proper wake control is possible. Based on the determined free standing wind turbines 1a to 1d and the global wind speed the influence of the downstream area 20a to 20d, which corresponds to the wake zones, to the downstream wind turbines 1e to 1g can be reduces. Necessary to that end is that the free standing wind turbines 1a to 1d changes their yaw angle and/or their pitch angle. Consequently the influence of the free standing wind turbines 1a to 1d to the downstream wind turbines 1e to 1g will be reduced. In result the power production of the downstream wind turbines will be increased at the same time structural loads will be reduced. Overall the entire power produc-tion of the wind park can be increased.

LIST OF REFERENCE SIGNS

1 wind turbine
2 tower
3 nacelle
4 drive train chain
5 rotor shaft
6 rotor
7 gear box
8 high-speed-shaft
9 generator
10 electrical components
11 yaw system
12 rotor blades
13 pitch system
14 nacelle cover
15 spinner
16 hub
17 wind vane
18 anemometer
19 wind park
20 downstream area
21 wind park controller

, Claims:We Claim:

1. A method for determining wind data in a wind park comprising the steps of
- determining global wind direction of a wind park,
- determining free standing wind turbines based on determined global wind direction and
- determining wind data of the wind park based on wind data meas-urements of determined free standing wind turbines.

2. The method for determining wind data in a wind park according to claim 1, wherein measuring wind direction from majority of wind turbines within the wind park for determining global wind direction of the wind park.

3. The method for determining wind data in a wind park according to claim 1 or 2, measuring wind speed of determined free standing wind turbines for determining wind data of the wind park.

4. The method for determining wind data in a wind park according to claim 3, wherein calculating average wind speed based on measured wind speed of determined free standing wind turbines for determining global wind speed of the wind park.

5. The method for determining wind data in a wind park according to claim 4, wherein calculating average wind speed takes place continuously or periodi-cally.

6. The method for determining wind data in a wind park according to one of the claims 1 to 5, wherein determining turbulence intensity based on deter-mined wind data of the wind park based on wind data measurements of de-termined free standing wind turbines.

7. The method for determining wind data in a wind park according to claim 6, wherein
- measuring wind speed of determined free standing wind turbines for determining wind data of the wind park and
- calculating the turbulence intensity based on measured wind speed of determined free standing wind turbines.

8. A method for controlling a wind park comprising the step of using the method for determining wind data in a wind park according to one of the claims 1 to 7.

9. The method for controlling a wind park according to claim 8, wherein de-termined wind data of the wind park is used as control input for at least one of the wind turbines of the wind park.

10. The method for controlling a wind park according to claim 8 or 9, wherein a park controller is configured for wake control.

11. A method for operating a wind park, wherein operating set-points are based on determined wind data according to one of the claims 1 to 7.

12. A wind park comprising a plurality of wind turbines having a park controller configured for executing the method according to one of the claims 1 to 7.

13. The wind park according to claim 12, wherein the park controller is config-ured to send determined wind data of the wind park, based on wind data measurements of determined free standing wind turbines as control input for at least one of the wind turbines of the wind park.

14. A computer program product comprising instructions which, when the pro-gram is executed by a computer, cause the computer to carry out the steps of the method for determining wind data in a wind park according to one of the claims 1 to 7.