EP-4735763-A1 - ENHANCED WIND TURBINE WAKE MIXING

Abstract

Method and wind turbine controller for controlling a wind turbine for improved wake mixing. The method comprises the steps of monitoring a periodic component of an air stream incoming on the at least first blade; controlling periodically and dynamically a pitch angle of the at least first blade over time according to a wake mixing control scheme on the basis of the monitored periodic component. For an array of at least a first wind turbine and a second downstream wind turbines, the method comprises controlling the first wind turbine such that the wake formed downstream of the first wind turbine follows a first periodic pattern, and controlling the second wind turbine such that the wake formed by the second turbine follows a second periodic pattern, wherein at least one of a frequency, a direction and/or a phase shift of the second periodic pattern is coordinated with the first pattern.

Inventors

• VAN VONDELEN, Aemilius A.W.
• OTTENHEYM, Joris
• VAN WINGERDEN, Jan-Willem
• KALOGERA, Maria

Assignees

• CrossWind Beheer B.V.

Dates

Publication Date

20260506

Application Date

20240628

Claims (20)

1. 1. Method for controlling a wind turbine comprising at least a first blade, the method comprising the steps of: - Monitoring a periodic component of an air stream incoming on the at least first blade; - Controlling periodically and dynamically a pitch angle of the at least first blade of the wind turbine over time according to a wake mixing control scheme on the basis of the monitored periodic component.
2. 2. Method according to claim 1, wherein controlling the pitch on the basis of the monitored periodic component comprises coordinating at least one of a frequency, a direction and/or a phase shift of the wake created downstream of the wind turbine with the monitored periodic component.
3. 3. Method according to the preceding claim, wherein the at least one of a frequency, a direction and/or a phase shift of the wake created downstream is further set according to a desired objective of power production and/or load mitigation.
4. 4. Method according to any of the above claims, wherein controlling the pitch on the basis of the monitored periodic component comprises synchronising in frequency and with a predetermined phase shift the wake created downstream of the wind turbine with the monitored periodic component.
5. 5. Method according to the preceding claim, wherein the predetermined phase shift is set to zero, such that the wind turbine is in phase with the incoming air stream.
6. 6. Method according to any of the above claims, wherein the wake mixing control scheme is a dynamic individual pitch control scheme, wherein the pitch of each blade of the wind turbine is controlled independently to periodically vary in time such as to create an helical wake downstream of the wind turbine.
7. 7. Method according to any of the above claims, wherein monitoring the periodic component of an air stream incoming on the at least first blade comprises monitoring a phase φ of an incoming periodical wake.
8. 8. Method according to any of the above wherein monitoring the periodic component of an air stream incoming on the at least first blade comprises monitoring at least one parameter of an incoming periodical wake modelled as up(t)= ^ ℎ ^ ^1 αi sin(ωit + φi) where αi, φi, ωi are the amplitude, phase shift and frequencies of each periodic component, and h is the number of periodic components, wherein preferably the at least one parameter comprises a phase shift φo of a fundamental component of an incoming periodical wake.
9. 9. Method according to any of the above claims, wherein monitoring the periodic component of an air stream incoming on the at least first blade comprises measuring at least one state of the turbine, and preferably deriving an estimation of the periodic component on the basis of the measured state.
10. 10. Method according to the previous claim, wherein measuring at least one state of the turbine comprises measuring at least a root blade moment on the at least first blade.
11. 11. Method according to any of the above claims, wherein monitoring the periodic component of an air stream incoming on the at least first blade comprises estimating and tracking the periodic component of the air stream incoming on the at least first blade.
12. 12. Method according to the previous claim and any of claims 9 or 10, wherein estimating and tracking the periodic component comprises processing at least one measured state of the turbine through a Kalman filter or a recursive least squares method.
13. 13. Method according to any of the above claims, wherein the wake mixing control scheme is configured for controlling the amplitude, location, frequency, phase shift and/or direction of a wake formed downstream of the wind turbine.
14. 14. Method according to any of the above claims, wherein the wind turbine comprises at least two blades, and wherein controlling the wind turbine comprises periodically and dynamically changing a pitch angle of each blade independently over time.
15. 15. Method for controlling an array of at least a first wind turbine and a second wind turbine, wherein, for a given wind direction, the second wind turbine is arranged at least partially downstream in a wake of the first wherein each wind turbine comprises at least a first blade, comprising the steps of: - Controlling the first wind turbine such that the wake formed downstream of the first wind turbine follows a first periodic pattern with a first frequency and a first phase shift, - applying the method according to any of the above claims for controlling the second wind turbine such that the wake formed by the second turbine follows a second periodic pattern, wherein at least one of a frequency, a direction and/or a phase shift of the second periodic pattern is coordinated with the first pattern.
16. 16. Wind turbine controller for controlling a wind turbine comprising at least a first blade, said wind controller being configured for: - receiving data related to a periodic component of an air stream incoming on the at least first blade, - monitoring the periodic component on the basis of the received data, - generating control signals for controlling dynamically and periodically over time a pitch angle of the at least one blade of the wind turbine according to a wake mixing control scheme and on the basis of the monitored periodic component.
17. 17. Wind turbine controller according to any of the previous claim controlling the pitch on the basis of the monitored periodic component comprises coordinating at least one of a frequency, a direction and/or a phase shift of the wake created downstream of the wind turbine with the monitored periodic component.
18. 18. Wind turbine controller according to any of the above controller claims, wherein the at least one of a frequency, a direction and/or a phase shift of the wake created downstream is set according to a desired objective of power production and/or load mitigation.
19. 19. Wind turbine controller according to any of the above controller claims, wherein controlling the pitch on the basis of the monitored periodic component comprises synchronising in frequency and with a predetermined phase shift the wake created downstream of the wind turbine with the monitored periodic component.
20. 20. Wind turbine controller according to preceding claim, wherein the predetermined phase shift is zero, such that the wake downstream the wind turbine is in phase with the incoming air stream.

Description

ENHANCED WIND WAKE MIXING The present disclosure relates to a method for controlling a wind turbine, a wind turbine controller arranged for the method of controlling a wind turbine, and a wind turbine comprising the wind turbine controller arranged for the method of controlling the wind turbine and an array of wind turbines, wherein at least a second wind turbine comprises the wind turbine controller. To meet the climate goals, renewable energy sources such as solar and wind energy are required. The most effective approach for developing wind energy on a large scale is by placing individual wind turbines, either on land or offshore, in so-called wind farms. Such wind farms optimize costs, e.g. cabling, maintenance and installation. The exact distribution of wind turbines may depend on several parameters, such as soil conditions or sailing routes but the dominant wind directions play an important role in this design. Typically wind turbines are then placed with respect to each other such that their wakes interact the least with each other when the wind blows from dominant directions. Still, situations occur relatively often where the wake generated by an upstream turbine introduces interaction with the downstream turbines that significantly affect power generation. By wake is meant the region behind a turbine where the flow is changed. Turbines in a wake typically experience lower wind speeds and an increase in turbulence. This results in turn in lower power generation and increased fatigue loads on the downstream turbines. By wake recovery is meant the phenomenon where the wind speed in the wake returns to the free-stream velocity due to mixing with the ambient air. The wind condition and the turbine design itself determine when wake recovery takes place. The distance at which this happens is usually larger than multiple rotor diameters. It is estimated that average power losses due to turbine wakes are in the order of 10 to 20% of the total power output in large offshore wind farms. In addition to reduced power generation, the fatigue load is estimated to increase by 5 to 15%. In order to optimize the power output on the wind farm level, wind farm control research has thus been focussed in recent years on controlling the wake itself. In particular, a type of wind farm controllers facilitates early wake mixing with the surrounding (’free stream’) wind field by manipulating the flow in a dynamic manner. This method, known as Dynamic Induction Control (DIC) involves collectively pitching the blades at a certain frequency to change the magnitude of the thrust force. As a result, the induction factor varies, causing the flow immediately behind the turbine to consist of both fast- and slow-moving parts. These parts interact with each other due to their different velocities, thereby promoting wake mixing. The resulting pulsating shape of the flow is characteristic of this approach, which is commonly referred to as the ‘pulse’ method. A negative side effect of this dynamic actuation is the increase in fatigue loads, especially on the tower and pitch bearings. Dynamic Individual Pitch Control (DIPC) has proposed as an alternative to DIC. Like DIC, DIPC uses the pitch actuators to dynamically control the flow. However, instead of actuating the blades collectively, DIPC applies a phase shift to each blade. This delay causes the thrust vector to periodically change direction rather than the magnitude, resulting in a wake behind the turbine with a helical shape. This method is commonly referred to as the ‘helix’ approach. This approach is in particular explained in WO2021/096363 of the present applicant, which is hereby incorporated by reference regarding the control concept of DIPC. Compared to the ‘pulse’ approach, the ‘helix’ approach has certain advantages. First, thrust variations are significantly reduced because they are more evenly distributed across the rotor disc. However, the blades experience a slightly stronger loads increase compared to the ‘pulse’ approach. As wind turbine wakes propagate far downwind, other wind turbines in wind farms can be affected by them under certain wind directions. It is common to control turbines individually in wind farms. This is called greedy control, where each turbine aims to reach its optimal performance. As a result, downstream waked turbines will experience reduced power production and increased fatigue loads. By following a greedy control strategy, even when applying wake mixing control scheme to an upstream turbine, a wind farm will therefore still reach sub-optimal behaviour due to the waked downstream turbines. The distance at which wake recovery takes place is usually much larger than the distance between turbines in a wind farm, as placing turbines close together reduces costs. It may be a goal of the present disclosure, possibly next to other goals, to obtain a method for controlling a downstream wind turbine that reduces the wake effects of an incoming wake on