Review Reports

Round 1

Reviewer 1 Report (Previous Reviewer 2)

Comments and Suggestions for Authors

The proposal is interesting, but the following observations must be addressed.

1. Why was v(k-2) used in the sampling process rather than v(k-1)?

It is important to indicate the minimum procedure for obtaining e(k), A(k) and R(k) in expression (9).

3. A diagram indicating the trigonometric relationship that allows expressions (11) and (12) to be obtained should be included.

(4) Include the minimum development required to obtain (27).

In the simulation results section, the simulations should be placed after their description to make the proposal and its impact easier to understand.

(6) A comparative table should be included for the proposed method and TOGI and SOGI methods, highlighting the main characteristics that allow the authors' conclusions to be validated.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report (Previous Reviewer 1)

Comments and Suggestions for Authors

As this is a resubmitted manuscript, I have found the previous paper version and I have performed a direct comparison of this and the previous paper version. The Authors have performed some minor modifications and improvements, but the most problematic elements still remain in the paper and are not resolved at all. For the resubmitted paper version, the Authors have enough time to properly expand this paper and make a clear connection with the real exploitation conditions, but all of this is completely missing. The Authors have answered to my comments, but the elements which are explained as performed and implemented in the paper are completely missing.

 

In this review, I will refer to my previous comments only:

 

1) Previous comment 1: In the Abstract the Authors have added as the most important exact result of this paper: “the parameter estimation method is consistently controlled within 30 ms, with all estimation errors converging to zero.” Is this really the most important result which clearly highlights paper novelty and makes a clear distinction in relation to other literature? I don’t believe so, because the same can be obtained by other numerical approaches, not only by the presented one, so this cannot be the most important exact results and conclusions obtained in this research.

2) Previous comment 2: The Authors did not add in the paper a Nomenclature, only the Abbreviation list is slightly enlarged. In the Nomenclature, all abbreviations, symbols, and markings used throughout the paper should be placed and explained, which is especially highly important for the presented mathematical model. Many variables in the presented mathematical model are not properly explained and described – I was hoping that the Nomenclature where all missing elements should be presented will be very helpful in clear understanding the presented mathematical model. Unfortunately, variables of the mathematical model are not presented in one place – what again makes high difficulties in proper mathematical model understanding.

3) Previous comment 3: After modifications, the presented mathematical model is less understandable than in the first paper version (at least to me). Novelties and contributions presented in the mathematical model are still completely unclear and cannot be detected.

4) Previous comment 4: Section 4. Stability Analysis is still completely unclear, especially when numerous variables are not properly described and discussed and when they are not presented in the Nomenclature.

5) Previous comment 5: Section 5. Simulation Results – a clear connection with the real exploitation conditions is still completely missing. There is missing any exact validation. The Authors have presented simulation results which may look like real exploitation conditions, but all the presented is the product of numerical simulations – there is missing any connection to the real system in real exploitation conditions where occur some losses and disturbances which cannot be easily captured by mathematical modeling. The Authors have again presented several mathematical model variations with different basic assumptions – but direct validation and comparison of mathematical model results and results from the real exploitation conditions did not exist.

6) Previous comment 8:  The paper is still theoretical only - comparison to the measured results and real exploitation conditions is still missing.

7) Previous comment 9:  In the Conclusion are still missing any exact novel and unique results obtained in this analysis.

8) Previous comment 10: In the List of the References the Authors have added exactly four new references – I did not consider four new references only as a proper and sufficient literature extension.

 

In addition:

 

The whole paper looks too simple; if the Authors have performed extensive numerical simulations, then much more results should be presented and discussed. At the moment, the paper looks like a theoretical approach to the numerical modeling of the observed system – nothing more than that.

 

Final remarks: Unfortunately, the Authors did not resolve the most important problematic and debatable elements, while a clear connection to the real exploitation conditions is still completely missing in the paper. The whole paper remains theoretical only, without any clear novelty or contribution to this research field. Previously, I have recommended a major revision of the paper, because I believe that the Authors will be able to properly improve this paper during the revision process. I am highly disappointed that the paper is not properly improved in the resubmitted version and that major problematic elements still remain. Now, I do not believe any more that the Authors will perform proper improvements and additions in another possible revision, so I cannot recommend this paper for publication, due to the above explained reasons.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report (New Reviewer)

Comments and Suggestions for Authors

Please improve the manuscript according to comments 

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report (Previous Reviewer 1)

Comments and Suggestions for Authors

After this revision, the Authors have performed notable improvements and modifications. Almost all elements mentioned in my review are properly performed and implemented in the paper.

Nomenclature is added and properly arranged; now the details related to the numerical model are clear and understandable. The Authors have added experimental results and a clear comparison of the developed method in relation to the standard, traditional methods is performed and discussed. Now, the benefits and advantages of the developed method are clear and easily understandable. List of the References is sufficiently enlarged.

However, I believe that the paper still requires minor revisions due to the following elements:

1) I cannot understand why it is so difficult for the Authors to add some exact results (along with proper descriptions) obtained in this research in the Abstract and Conclusion. Such results will clearly highlight paper novelty and the most important exact elements obtained in this paper, which will make a clear difference in comparison to other published literature. Therefore, I still believe that the most important exact results obtained in this research should be added in the Abstract and Conclusion.

2) The Authors have clearly highlighted all benefits of the proposed method. However, possible problems and challenges of the proposed method in comparison to other similar methods are not properly explained and discussed - possible problems and challenges of the proposed method should be properly explained and discussed.

After performing the above mentioned elements, I believe that the paper can be accepted for publication.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report (New Reviewer)

Comments and Suggestions for Authors

please seriously consider my concerns to improve quality of research 

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 3

Reviewer 3 Report (New Reviewer)

Comments and Suggestions for Authors

The authours did not considered all recomended points .They should consider all concerns seriously to improve the manuscript 

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1) The Abstract did not contain any exact interesting results obtained in this research. The Abstract should be rearranged and the most important exact results should be added and properly described.

2) Due to numerous abbreviations, symbols and markings used throughout the paper, in the paper should be added a Nomenclature inside which will be listed and explained in one place all mentioned elements. A Nomenclature is necessary because it will notably improve paper readability. Currently, presented Abbreviations list is not sufficient and helpful to any reader.

3) Sections 2, 3 and 4 are related to the description of the applied mathematical model. It is not clear (at least to me) what exact novel elements the Authors have performed and introduced in this numerical model. Proper descriptions, explanations and highlighting new and unique elements in the numerical model are required.

4) Section 4. Stability Analysis should be much better explained. At the moment, it is presented dominantly mathematically – without proper descriptions and explanations this Section is very hard to understand to anyone who is not strictly related to this mathematical approach.

5) Section 5. Simulation Result:

- First of all, a better Section title will be Simulation Results, not Result only.

- Secondly – in this Section the Authors should perform a clear correction of the developed numerical model and real exploitation conditions. At the moment, all presented elements are mathematical only, there is missing any exact connection with the measured real exploitation conditions. Mathematically, I don’t have any doubt that obtained and presented results are correct, but there is no evidence that the developed numerical model can properly track real exploitation conditions. At the moment, it is unknown numerical model accuracy/precision in comparison to the measured results from the real exploitation conditions. Therefore, without measurements and exact verification of the numerical model using real exploitation conditions – the presented model remains theoretical only with unknown accuracy/precision in comparison to the measured results. Proper connection and verification related to real exploitation conditions are highly required.

- Thirdly - theoretically and mathematically, the Authors are surely right – but in the paper is completely missing any exact evidence that the presented results and numerical model performance can be obtained in the real exploitation conditions. These evidences should be added in the paper and properly described.

6) Throughout the paper can be found obvious and typing mistakes – the whole paper should be carefully checked and such mistakes should be corrected. For example – Line 217 – this is Subsection 5.2., not 5.2. and 4.2 simultaneously (this is just one example).

7) The Authors have presented various advantages of the developed numerical model, but the numerical model disadvantages are not even mentioned. As well as any other numerical model, this one also has at least several disadvantages – mentioned numerical model disadvantages should be properly explained, described, and discussed.

8) At the moment, the paper is theoretical only – comparison to the measured results and real exploitation conditions is required.

9) Section 6. Conclusion:

- First of all, the Conclusion is missing any interesting exact results obtained in this research (along with proper explanation). Also the Conclusion is general and descriptive only at the moment (as the Abstract). The Conclusion should be notably modified and the most important obtained exact results should be presented and properly highlighted.

- Secondly – at the end of the Conclusion should be placed guidelines in further research related to this topic.

10) List of the references should be enlarged and more recent literature should be added and properly incorporated in the paper text.

 

Final remarks: This is an interesting paper which presents an interesting new numerical approach. However, the Authors should properly connect this new numerical approach with the real exploitation conditions and measured exploitation data – without this exact and properly performed connection, this paper remains theoretical only. I hope that the Authors will be able to perform the mentioned modifications, improvements, and connections during the paper revision process.

Reviewer 2 Report

Comments and Suggestions for Authors

The article presents a proposal entitled 'A delayed sampling-based power grid parameter modelling and estimation method for a wind power system with a DC component'. After carefully reading the article proposal, the following considerations are important:

1.- The authors indicate that expression (3) is obtained from:
V(k) + V(k − 2) = 2V C cos 2(w Ts) cos (w Ts + φ) + 2V dc + 2V C cos (w Ts) sin (w Ts) sin (w Ts + φ).
However, it is unclear how this was obtained and the linear relationship approach must be substantiated. This explanation should be included in the proposal as it forms the basis of the study.

2.- In (6), the representation of R(k-1) and m(k) should be specified, as well as the reference for the adaptive method and the calculations in (7) and (8).

3.- On line 112, the authors state, 'According to the relationship between µ1 and ω(4),...'. What does ω(4) represent?

4.- The results presented by the authors in: Case A, Case B, Case C and Case D are unclear. The figures are not representative of what is being sought. Figures 5, 6 and 7 only show the dynamic error of an injected disturbance and do not specifically indicate how this relates to the proposal in the article.

In general, the proposal is not properly structured. Nor is it substantiated.