Investigation on the Effect of the Baseline Control System on Dynamic and Fatigue Characteristics of Modern Wind Turbines

Round 1

Reviewer 1 Report

Major revisions:

In general, I notice a lack of statistical rigor in the results. Results are compared graphically. In some cases a clear difference is seen but in other cases the differences are not so clearly seen. In an experimental work like this, I think it should contain greater statistical rigor. Only a standard deviation is calculated, but no type of statistical inference is carried out that allows the results obtained to be affirmed with some degree of uncertainty.

In particular,

Lines: 96-99:  Numerous studies are referenced in the introduction. However, you say that " rarely consider the interaction between the BCS and structural vibration ". Why do you think it is so rare to take this interaction into account in these models?

Lines: 338-345: It is very difficult to observe something in figures 10, 11, 12 and 13. Is it possible to have some other type of graphic representation that allows visualizing what the authors want to show us in those figures?

Line 350:  Comparing standard deviations is not very correct since they are dispersions referred to a mean value. Wouldn't it be better to use the coefficient of variation (standard deviations divided by the arithmetic mean)?

 

Minor revisions:

Line 16: 

“... to wind loading with and without considering BCS were compared.”

“… to wind loading with and without considering BCS (case 1 and case 2, respectively) were compared.”

 

Line 251:

"This is the results of BCS regulation".

"These are the results of BCS regulation".

 

Author Response

Dear reviewer：

We would like to express our sincere thanks to the reviewers for the constructive and positive comments. Those comments are all valuable and very helpful for revising and improving our paper. We have studied comments carefully and revised the manuscript. We have addressed the comments and the amendments are highlighted in red in the revised manuscript. Point by point responses to the comments are listed in the attachment. Please see the attachment.

 

Kind regards,

Chenyang Yuan

Author Response File: Author Response.docx

Reviewer 2 Report

Excellent research has been done and shows the high expertise of the authors in this field. I believe this article can be published after minor revision. please consider the following:

1- what is the meaning of case 1 and case 2 in the abstract. the authors should firstly define these cases and then use case No.

2- what is the meaning of 3P in the abstract (the 3P of wind turbine ....)?

3- In most research as stated in the literature review, fatigue life assessments are performed without BCS. But, some scholars do it considering BCS. So, what is the novelty of the present research compared to others? based on the title, the authors only compared fatigue analysis with and without considering BCS. you should describe the innovation in bold sentences.

4- fatigue analysis and rain flow cycle counting are done for different caseloads such as different shear stress and moment. As you know, the blade has complicated surfaces and geometry. So, it is subjected to a 3D stress field due to different working conditions, so why the authors do not use equivalent stress theories and after that use the cycle counting technique for a time history load?

5-The references used are old and need to be updated (only 2 or 3 articles published after 2017).

 

 

Author Response

Dear reviewer：

We would like to express our sincere thanks to the reviewers for the constructive and positive comments. Those comments are all valuable and very helpful for revising and improving our paper. We have studied comments carefully and revised the manuscript. We have addressed the comments and the amendments are highlighted in red in the revised manuscript. Point by point responses to the comments are listed in the attachment. Please see the attachment.

 

Kind regards,

Chenyang Yuan

Author Response File: Author Response.docx

Reviewer 3 Report

The authors have done dynamic structural and fatigue analysis for NREL 5 MW turbine with and without baseline control. The topic is of big importance and can be interesting to the readers. Overall analysis and representation of the methods and results are fine, but can be further improved. I overall recommend publishing of the article after addressing the following comments:

1- Some of the models' description is inadequate or needs better presentation. Examples are as follows:

• In Equation 4, only the mass matrix and forces array are shown, what about the stiffness matrix which is responsible for the returning the blade to its original position after deflection? Also, damping matrix can be used for more accurate results, but can usually be omitted.
• The authors haven't mentioned what software they used for the wind field generation. Is it TurbSim? If so, please mention it. Also, please mention why exactly did you choose Kaimal spectral model. You can mention that vonKarman for instance is more suitable for wind tunnel turbulence, while Kaimal model is suitable for atmospheric turbulence. Check: https://doi.org/10.5109/1929727
• The same comment is for MLife fatigue analysis tool, it has been first mentioned in the results and discussion section. It should be mentioned in the methods and theory first.
• The authors implemented baseline control for the generator and blade pitch, however, they haven't mentioned the control parameters. For instance, which gains for the PID control have you used? Did you use the certification test control file in FAST? If so, please mention the details of the control methods.

2- Some suggestions to improve the manuscripts presentation:

• In Table 1, it would be better if you use the Tip Speed Ratio of 7 at the rated speed, instead of the rated tip speed. TSR is more informative nondimensional property.
• In Tables 3 and 4, I suggest switching all the signs of the Difference (%), since you compared to the uncontrolled turbine (Should be the reference). So, a negative difference means reduction in the value. While in Table 4 for the tower loads at cut-in wind speed, the controlled turbine showed increase in the loads and deflections, and hence, positive difference.
• Figure 14, you should mention the physical quantity on the Ordinate, not only in the caption. I should get which DEL for each subfigure without looking for it between the text or in the caption. For instance, Fig 14.a, the ordinate title should be: BFX Normalized DEL and STD.
• Figure 15 would be more informative if the abscissa was the blade's Azimuth angle instead of Time. Blade's azimuth position is of great influence on the sinusoidal behavior of blade's loads and deflections. The blade in the upright position is against gravity, while after 180 azimuth degrees gravity will play a major rule. Remember the blades are not in a vertical position, there is a cone angle and shaft tilt angle, and gravity matters in the deflections. Check: https://doi.org/10.3390/en12101881
• Frequency analysis for each time series would be of big importance to check the exiting frequencies for each series and check for resonance.

3- Formatting and proofreading:

The manuscript overall needs proofreading, there some grammatical and formatting mistakes that should be addressed. Examples are as follows:

• L32-36: Long sentence. [Consequently, ..... of wind turbine]
• L35: What's more [Please refrain from using informal language, change to what is more]
• L49-79: Very long paragraph, should be divided into two or three paragraphs.
• L51: Analysis to drive the local loads [Derive]
• L101: an aeroelastic mode FAST [code]
• L219: damage is supposed that DEL [Supposes that]
• L258-259: It can be see that the each mean [Remove the]
• L301: which causes the 3P of the rotor speed is code [Weird phrasing, please revise]
• L352: also calculated to analysis the results [analyze]

Author Response

Dear reviewer：

We would like to express our sincere thanks to the reviewers for the constructive and positive comments. Those comments are all valuable and very helpful for revising and improving our paper. We have studied comments carefully and revised the manuscript. We have addressed the comments and the amendments are highlighted in red in the revised manuscript. Point by point responses to the comments are listed in the attachment. Please see the attachment.

 

Kind regards,

Chenyang Yuan

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

The authors have done good effort addressing comments of all reviewers. The manuscript has improved significantly. I have no more comments regarding the technical content.