Development of a Novel Control Scheme for Grid-Following Converter under Asymmetrical Faults

Round 1

Reviewer 1 Report

1. As, the negative sequence injection is important only in case of unbalanced faults, so this paper also discusses the control modifications to eliminate the phase-locked loop and to minimize the control loop for the negative sequence current injection.

What do the authors mean by the elimination of the phase-locked loop?

 

2. What do the authors mean by the elimination of the phase-locked loop?
3. The main quantitative findings should be added at the end of the abstract.
4. - The variables used in the equations must be explained when they first appear in the text. Please go through the entire manuscript to address this point.
5. The equation 3 is a consequence of the conditions v_q=0 which is generally used in synchronous reference frame PLL (SRFPLL). The authors should clarify this matter.
6. It has been assumed that the parameter k⁺ ranges between 2 and 6. The authors should justify the origin of these boundaries.
7. The link between Eq 15 and Figure 8 should be clarified in terms of the appearance of the operator Z^-2Ts.
8. Some abbreviations are not given in the text (QNP, NQP, …). They should be given after the first appearance of the whole sentence in the text.
9. The authors have ignored the zero sequence. It is suitable to compare their findings with control strategies taking into account such zero sequence. The following reference and others can be consulted https://doi.org/10.1142/S0218126619500579 to highlight the contributions of the present work.
10. How the Voltage Unbalance Factor has been evaluated?
11. The drawbacks and the perspectives of the present study should be added to the conclusions.

Author Response

Dear Reviewer,

Thank you for reviewing this manuscript. We are thankful to you for your insightful comments on our paper. Please find the response in the attached file.

Sincerely,

Muhammad Abubakar, Herwig Renner, and Schürhuber Robert

Author Response File: Author Response.docx

Reviewer 2 Report

energies-2155582

The general idea of the paper seems to be good. However, the paper organization is not acceptable, and there are several major technical challenges that should be effectively addressed.

Comments

 

 

1. Clarify better the innovation of this work in the abstract and in the main text.
2. The introduction has been vaguely written. My suggestion is to divide the introduction into three subsections: 1) motivation and incitement, 2) literature review and 3) contribution and paper organization.
3. A short paragraph introducing the problem statement should be included at the end of the Introduction section. What is the central problem in a sentence that manuscript wants to solve?
4. The main contribution of the paper should be highlighted and emphasized. It would be great if the drawbacks and gaps of literature are clear and, particularly, how the proposed approach aims at filling these gaps.
5. How Authors have obtained the values for the controller gain?
6. Given photo of the hardware. Where is the hardware results?
7. Extend the conclusion with more general usability. What are the benefits of the results in a global context? Please explain this better in the manuscript.
8. There are some grammatical errors and typos that should be corrected before publication.
9. Results and discussion include the presentation of the results but without an in-depth discussion based on other results in the literature. Without this enhancement, the article cannot be published.
10. Include the latest reference.
11. No comparison has been made with the in-use techniques to prove the supremacy of the proposed system. Furthermore, a lot of work has been done and can be found on the said problems with proposed controllers in the literature. Therefore, the authors need to clearly redefine the novelty of this proposed work.

Author Response

Dear Reviewer,

Thank you for reviewing this manuscript. We are thankful to you for your insightful comments on our paper. Please find the response in the attached file.

Sincerely,

Muhammad Abubakar, Herwig Renner, and Schürhuber Robert

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript presents research related to improving the characteristics of power electronic devices in power systems based on optimal control synthesis. In this aspect, the work is useful and has a great impact on the development of power electronic devices and systems with application in energy. The main advantages of the presented engineering development are related to improving the qualities of power electronic devices compared to previous solutions. The manuscript is on a very topical subject and has great potential for development. My main observations and comments are as follows:

- it would be useful, in addition to the advantages in the conclusion section, for the authors to comment on the disadvantages of the proposed management method. In this way, a complete picture of its qualities, capabilities and application limitations will be obtained;

- the manuscript is not formatted as required and the quality of all figures, tables and graphs could be improved;

- a more detailed report on the state of the research problem should be made, containing more relevant literary sources;

- I recommend describing in detail the model and its implementation in mathematical software for conducting numerical experiments, because its synthesis and research capabilities would be very useful for other researchers working in this field.

Author Response

Dear Reviewer,

Thank you for reviewing this manuscript. We are thankful to you for your insightful comments on our paper. Please find the response in the attached file.

Sincerely,

Muhammad Abubakar, Herwig Renner, and Schürhuber Robert

Author Response File: Author Response.docx

Reviewer 4 Report

 

The author presented a novel and simplified reference current generation scheme for the grid-tied converter in case of unbalanced faults while complying with the recent grid code requirements. Comments for the authors include:

1.       The introduction needs to be better articulated. There needs to be more than the literature survey to prove this work's objective.

2.       In the introduction section, some references are old and can be improved to some extent. The latest references should be added.

3.       The innovation of the paper could be clearer. State the novelty of this work at the end of the introduction. After reading the full article, the reviewer felt that the authors' contribution is less. 

4.       How does the proposed control scheme ensure the converter's maximum utilization in faulty conditions?

5.       How is a new sequence extraction scheme based on a delayed sample developed in a stationary reference frame?

6.       Please discuss in detail about delay sampling method.

7.       How the control modification minimizes the control loop for the negative sequence current injection?

8.       How many loops are utilized for a current controller that can be used both for the positive and negative sequence current injection?

9.       Figures 10 and 11 presented in this paper could have better quality. Please improve the quality.

10.    There needs to be more than a comparison for possible publication. The proposed control scheme should be compared with different recently proposed techniques for the grid-tied converter in case of unbalanced faults while complying with the recent grid code requirements.

11.    Could the experimental results be included in this research work? 

12.    There are grammatical things that could be improved in this article.

13.    After improving the paper, recent references must be included in the reference section.

 

Author Response

Dear Reviewer,

Thank you for reviewing this manuscript. We are thankful to you for your insightful comments on our paper. Please find the response in the attached file.

Sincerely,

Muhammad Abubakar, Herwig Renner, and Schürhuber Robert

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have addressed all the comments. The paper may be accepted in its present form.

Reviewer 2 Report

Paper is well revised. But figures are not properly placed . It's overlapped with tha text. Kindly ask authors to resubmit with proper formatting. 

Reviewer 4 Report

The authors have addressed the concerns of the reviewer. Please accept it for publication in its present form.