the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Some comments on experimental results of three lift controllers for a wind turbine blade section using an active flow control
Abstract. Controlling wind turbines is generally performed globally (rotor yaw or blade pitch control) to optimize the energy extraction and minimize rotor's loads for rotor's lifetime extension. This means that no information from the blade aerodynamics is up to now taken into account in the control loop while it is well understood that wind inflow interaction with blade aerodynamics can lead to power loss, load fluctuations and noise generation. This work deals with the development of control algorithms applied at the level of the blade section, considering only local aerodynamic sensing and actuators. The objective is to extract the maximum power from the wind energy by maintaining the aerodynamic lift at its highest value, while limiting load fluctuations using different solutions of control which take into account disturbances from different turbulent inflows. Some control strategies are investigated thanks to an experimental bench in the aerodynamic wind tunnel of LHEEA's laboratory in order to compare the tracking performances with respect to different operating scenarios.
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RC1: 'Comment on wes-2024-15', Anonymous Referee #1, 20 Mar 2024
Some comments on experimental results of three lift controllers for a wind turbine blade section using an active flow control
This paper considers three control schemes to extract maximum power by maintaining the highest aerodynamic lift value using local blade section control. Robust PID, model-free, and adaptive super-twisting controllers are proposed. It is concluded that model-free control is a good compromise in case of saturation constraints.
I value the experimental validations that have been performed, showing the performance of the three controllers. Furthermore, I appreciate that you do not draw hard conclusions that one controller type is superior to the others. The introduction should be improved, discussing what has been done in the field of local blade section control and referencing other work. Furthermore, the motivation for choosing these three controllers should be improved upon. The presentation of results should improve, and the description of how you arrive at the controller calibrations should be better.
I advise a major revision of this paper before it can be considered for publication in WES.
MAJOR COMMENTS:
- I think the paper title is weak because of the first three words: "Some comments on." Can you just leave these words out?
- There has been done quite a lot of research on local blade section control. Please extend your introduction by discussing and referencing these works and positioning your work in relation to what has already been done.
- The introduction does not state anything about the outcome of this research, please include this.
- The introduction should clearly state the contributions. Is it that you evaluated three different controller types on an already existing test bench?
- The introduction should make clear why you chose these three controllers. Now feels a bit random. Also, these controllers are not well described in the introduction.- 2.3: It is not clear to me whether you can individually open/close each of the holes in the blade (you say something about multiple solenoid valves?). Maybe indicate and make it clear using a figure?
- Section 3 is not introduced, you directly begin with 3.1.
- 3.1: So you consider a SISO system and no actuation of individual holes? I.e.: Output lift force (y), that needs to be controlled (follow a reference lift, y*) by a pressure input (u)? Be more clear on this.- The performance that you can attain with each of the controller types is very dependent on the calibration and implementation of the controller. I think it is hard to conclude that one of the controllers is superior with respect to the other controllers, using your current approach. That is, how do you know for sure that you cannot attain the performance levels of the other controllers, simply by a more optimal calibration of the gains? Please provide more discussion and insights on this point. What would your approach be to get the most optimal performance of all the controller so that you can draw these conclusions?
MINOR COMMENTS:
- Captions underneath figures need to be more extensive, so that figures are interpretable independent from the main text.
- Subscripts that are not indices should be nonitalic, e.g., K_\mathrm{p}Citation: https://doi.org/10.5194/wes-2024-15-RC1 -
RC2: 'Comment on wes-2024-15', Anonymous Referee #2, 05 Jul 2024
General comments
It is an interesting paper that describes an 2D experimental work on the development of control algorithms applied at the level of the blade section, considering only local aerodynamic sensors and actuators. The authors have presented the experimental setup and control strategies, together with some interesting results.
It is well-organized paper providing the in depth knowledge on the performance and the robustness of different control algorithms (Robust PID, MFC and AST) at the blade section.The reviewer still has some specific comments to address in order to further improve the quality of the paper.
Specific comments
In the following, there are some more specific comments:1. From line 11 to 14 are just repeating exactly the same sentence in abstract. Please consider modifying it.
2. Line 23,"(Bartholomay et al. (2021)) developed a feed-forward controller ...". The parentheses are not needed. The same applies to all the citation in the paper.
3. At line 36,"PID", this term appears in the first time, you need to spell the whole words.
4. The information provided by Figure 5 is very limited, either adding more information to the figure or removing it.
5. There are many occurrences of "thanks to" in the paper, which makes the sentence to be seen as informal or conversational. It does not fit with a technical paper. Please consider modifying it.
6. what is "The ultra-local model". Please describe it or use any citation.
7. Please explain in more detailed regarding how to estimate "F" used in Eq. (2) since this is very important parameter.
8. In Figure 6, the close-loop scheme is not clear. Why is the chopped wind flow signal is added with a signal coming out from "Blade section" block? The measured lift is produced by the blade section directly, but it is not produced by the wind flow directly. You should modify this diagram.
9. At line 186, what is "PWM"? This term is appeared in the first time, you need to spell the complete words.
10. At line 210, "The PID control design requires at least to know a bit the dynamic of the system". What do you mean "a bit"? Can you specify what are the knowledge from the dynamic of the system is needed for the design of the PID control?
11. At line 232, what is "SSE" and "STD"? These terms appear in the first time, you need to spell the whole words.
12. At line 278, Scenario 2 is selected, but it has the lowest turbulent intensity. Is this a proper scenario which can demonstrate the performance of all the controller? Can you explain this?
13. Figure 9, it seems that AST is not able to converge to the reference value. Can you explain this?
14. Comparing Figure 10, 11, 12, the reviewer sees that the PID (c) controller shows only slightly better tracking performance on the lift. It makes more sense if you plot Figure 10, 11 and 12 on one figure so that the comparison can be made directly, and it also can save some pages. Please do this modification.
15. The author should present in more detailed the anti-windup algorithms used in both PID and AST in section 3.
16. Suggestion: The font size in Figures should be increased.
17. Again, Figure 16, 17, 18 should be plotted in one figure to achieve a better comparison.Technical corrections
In general, there are many informal words used in the paper, e.g., "pretty well" at line 227. The paper need to be modified and written in a more technical manner. More comments related to grammar mistake and typos, etc. please find them in the annotated pdf file directly.
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