Matlab-Based Design Consideration of Series ZVS Single-Ended Resonant DC-DC Converter

Round 1

Reviewer 1 Report

The motivation for this study is not clear. The authors should explain why the authors have adopted optimization procedures to improve the design process. The converter is not new, and the modelling of the converter is also not new because you can find the modelling in various literature. The objective function and constraints are not clearly explained. The converter performance is not tested under various testing environments, i.e., change in input, change in load, and external disturbance. The stability of the converter is also not discussed. To validate the claimed results, the authors must share the source code in the repository and share it during the revision submission. This is required only for the reviewing purpose. It is also suggested to post in open source for the reader's benefit if the authors want to increase visibility. The authors should list the contributions at the end of the introduction section. The organization of the paper is also missing. 

The overall language quality of the paper is poor. Try to improve it.

Author Response

First of all, I would like to thank you for your thorough review of our paper (mathematics-2384778) and helpful comments to improve it.

Reviewer 1

Comments to the Authors
The motivation for this study is not clear. The authors should explain why the authors have adopted optimization procedures to improve the design process. The converter is not new, and the modelling of the converter is also not new because you can find the modelling in various literature. The objective function and constraints are not clearly explained. The converter performance is not tested under various testing environments, i.e., change in input, change in load, and external disturbance. The stability of the converter is also not discussed. To validate the claimed results, the authors must share the source code in the repository and share it during the revision submission. This is required only for the reviewing purpose. It is also suggested to post in open source for the reader's benefit if the authors want to increase visibility. The authors should list the contributions at the end of the introduction section. The organization of the paper is also missing.

The overall language quality of the paper is poor. Try to improve it.

To Reviewer 1:

            Thank you very much for your review and valuable remarks.

1. The motivation for this study is not clear. The authors should explain why the authors have adopted optimization procedures to improve the design process. The converter is not new, and the modelling of the converter is also not new because you can find the modelling in various literature.

- Thank you very much for the remark. The main idea of the manuscript is by combining different design methods: analytical (design procedure), based on the designer's experience and optimization to determine the most suitable values of some of the circuit elements, which are very difficult to find analytically. We hope that in revising the manuscript this has become clearer and more understandable to the reader.

2. The objective function and constraints are not clearly explained.

- Thank you very much for the question. The objective function is based on the defined reference curve. The limitations are related to the reduction of current ripples through the filter inductance in transient modes, and also from technological design limitations related to the values of the filter elements. 

3. The converter performance is not tested under various testing environments, i.e., change in input, change in load, and external disturbance. The stability of the converter is also not discussed.

- Thank you very much for the suggestion! We have conducted additional research on the optimized DC-DC converter under sudden load and input voltage changes. The presented results confirmed the excellent dynamic characteristics of the device under study. We have not conducted a robustness analysis because this goes beyond the tasks we set out to solve in the manuscript. Rather, it is a task related to the synthesis of control.

4. To validate the claimed results, the authors must share the source code in the repository and share it during the revision submission. This is required only for the reviewing purpose. It is also suggested to post in open source for the reader's benefit if the authors want to increase visibility.

- Thank you very much for the suggestion! The source code of the authoring program is attached to your review reply. I will seek assistance from the assistant editor to upload this code for free access as well (I have no such experience so far).

5. The authors should list the contributions at the end of the introduction section. The organization of the paper is also missing.

- Thank you very much for the remark. The purpose and organization of the manuscript have been added to the introduction section.

6. The overall language quality of the paper is poor. Try to improve it.

- Thank you very much for the remark. The manuscript has been revised and edited based on your observations, comments and recommendations. Additionally, per the other reviewer's recommendation, Figure 3 has been omitted.

Thank you very much for your remarks and comments. They were very useful for me to emphasize the main tasks and contributions of the manuscript, and also to focus the attention of the readers on the new and unique elements.

Author Response File: Author Response.docx

Reviewer 2 Report

The reviewed manuscript describes the process of the design of the particular DC/DC converter at the theoretical level. The converter was chosen as an example to show the process because of its complexity. On one hand, the content of the manuscript is highly interesting for the converter designers because it presents a method step by step and it can be very helpful for many of them. On the other hand, I can’t find what’s new or original there to be published in Q1 journal. I understand the paper roughly as it follows: here is a converter topology, it is described with these equations, let’s have some basic values (as voltage, resistance of windings etc.) and let’s require such result waveform; now we use a tool/algorithm in Matlab that gives us the values of parameters; if it’s not optimal we code an iterative procedure that gives us better values. That’s it. I don’t think it is a new approach. So, I would like to know what is the novel contribution of the paper. And then, the theory is one thing, the practical realization another one. How can you prove that your results are really the optimal?

Otherwise, the text is written well and comprehensibly. I haven’t found some serious mistakes. The only one detail is in line 272 “Kirch’s”. “Kirchhoff’s” is correct. Further, I consider Fig. 3 as useless, but it’s my opinion.

 (I don’t feel qualified to judge the English, however, I feel some unsuitable word usage in the text.)

Author Response

First of all, I would like to thank you for your thorough review of our paper (mathematics-2384778) and helpful comments to improve it.

Reviewer 2

Comments to the Authors

The reviewed manuscript describes the process of the design of the particular DC/DC converter at the theoretical level. The converter was chosen as an example to show the process because of its complexity. On one hand, the content of the manuscript is highly interesting for the converter designers because it presents a method step by step and it can be very helpful for many of them. On the other hand, I can’t find what’s new or original there to be published in Q1 journal. I understand the paper roughly as it follows: here is a converter topology, it is described with these equations, let’s have some basic values (as voltage, resistance of windings etc.) and let’s require such result waveform; now we use a tool/algorithm in Matlab that gives us the values of parameters; if it’s not optimal we code an iterative procedure that gives us better values. That’s it. I don’t think it is a new approach. So, I would like to know what is the novel contribution of the paper. And then, the theory is one thing, the practical realization another one. How can you prove that your results are really the optimal?

Otherwise, the text is written well and comprehensibly. I haven’t found some serious mistakes. The only one detail is in line 272 “Kirch’s”. “Kirchhoff’s” is correct. Further, I consider Fig. 3 as useless, but it’s my opinion.

To Reviewer 2:

            Thank you for your review and valuable remarks.

1. The reviewed manuscript describes the process of the design of the particular DC/DC converter at the theoretical level. The converter was chosen as an example to show the process because of its complexity. On one hand, the content of the manuscript is highly interesting for the converter designers because it presents a method step by step and it can be very helpful for many of them. On the other hand, I can’t find what’s new or original there to be published in Q1 journal.

- Thank you very much for your comment. Our claim is that we use a rational design approach that combines classical design methods, supplementing them with modern advances in mathematical modeling, computational mathematics, and mathematical software. Another advantage of the presented procedure is that it is not based on data accumulated from numerous experiments, which facilitates the practical implementation of the optimization procedure. On the other hand, we believe that such research is important in view of the large practical application for the design of complex devices (which you also highlighted). In our opinion, it is important to present in such prestigious journals besides purely theoretical and more applied research, which will increase the impact of the journal itself. In our opinion, this is also the idea of organizing a special issue with such a theme.

2. I understand the paper roughly as it follows: here is a converter topology, it is described with these equations, let’s have some basic values (as voltage, resistance of windings etc.) and let’s require such result waveform; now we use a tool/algorithm in Matlab that gives us the values of parameters; if it’s not optimal we code an iterative procedure that gives us better values. That’s it. I don’t think it is a new approach.

- Thank you very much for your comment. The main idea of the manuscript is by combining different design methods: analytical (design methods), based on the designer's experience and optimization to determine the most suitable values of some of the circuit elements (which are difficult to find analytically). This is also the essence of the rational design method - to combine the advantages of classical and innovative design techniques, with the goal being to obtain the best possible result with the smallest requirements regarding the necessary resources to solve the task. We hope that during the revision of the manuscript this has become clearer and more understandable for the reader.

3. So, I would like to know what is the novel contribution of the paper. And then, the theory is one thing, the practical realization another one. How can you prove that your results are really the optimal?

- Thank you very much. By default, fmincon uses a numerical optimization procedure based on the “Levenberg Marquardt” method. This procedure can be replaced by gradient descent. Of course both optimization procedures will get stuck in the nearest local minimum. How was this problem investigated in our case? The paper has formulated a procedure to choose an initial approximation from which to start the optimization. The optimization itself is then run several times, varying the initial approximation within +-30% of its initial value. As a result, it gets "stuck" at the same optimal point. So, in this study we are talking about a sufficiently wide neighborhood in which there is obviously a minimum. Of course, strictly speaking, one cannot claim that the optimization problem itself has a single global minimum. On the other hand, changing the values of the circuit elements within wider limits would not make sense from the point of view of the practical implementation of the power electronic device and that the converter is being designed for a specific application. In accordance with your comment, we have changed the title of the manuscript where "optimal" was dropped.

4. Otherwise, the text is written well and comprehensibly. I haven’t found some serious mistakes. The only one detail is in line 272 “Kirch’s”. “Kirchhoff’s” is correct. Further, I consider Fig. 3 as useless, but it’s my opinion.

- Thank you very much for your comment. The manuscript has been revised and re-edited. The idea of presenting Fig.3 is to facilitate the implementation and use of the model we created and by non-specialists in applying mathematical software. On the other hand, we fully understood and accepted your arguments and removed Fig.3 from the edited version of the manuscript.

 Thank you very much for your remarks and comments. They were very useful for me to emphasize the main tasks and contributions of the manuscript, and also to focus the attention of the readers on the new and unique elements.

Round 2

Reviewer 1 Report

I am satisfied with the responses provided by the authors, except for comment 4. The authors have uploaded the .m file. I tried running it, but the algorithm failed to converge. It couldn't be able to satisfy the constraints. So, my doubt was raised. I appreciate the authors have made meaningful efforts, but to improve the quality, it is a must. Moreover, after extracting the three decision variables, how it has been adopted in Simulink is not available. Therefore, I insist the authors check it and upload the complete files as supplementary material or deposit them in any repository. Other than this, I am satisfied with the responses. Simulink files also need to be supplied because, after optimizing the variable, how these variables help the model to reduce the ripples during steady-state and dynamic operating conditions. 

Okay

Author Response

First of all, I would like to thank you for your thorough review of our paper (mathematics-2384778) and helpful comments to improve it.

Reviewer 1

Comments to the Authors
I am satisfied with the responses provided by the authors, except for comment 4. The authors have uploaded the .m file. I tried running it, but the algorithm failed to converge. It couldn't be able to satisfy the constraints. So, my doubt was raised. I appreciate the authors have made meaningful efforts, but to improve the quality, it is a must. Moreover, after extracting the three decision variables, how it has been adopted in Simulink is not available. Therefore, I insist the authors check it and upload the complete files as supplementary material or deposit them in any repository. Other than this, I am satisfied with the responses. Simulink files also need to be supplied because, after optimizing the variable, how these variables help the model to reduce the ripples during steady-state and dynamic operating conditions.

To Reviewer 1:

            Thank you very much for your review and valuable remarks.

1. I am satisfied with the responses provided by the authors, except for comment 4. The authors have uploaded the .m file. I tried running it, but the algorithm failed to converge. It couldn't be able to satisfy the constraints. So, my doubt was raised. I appreciate the authors have made meaningful efforts, but to improve the quality, it is a must. Moreover, after extracting the three decision variables, how it has been adopted in Simulink is not available. Therefore, I insist the authors check it and upload the complete files as supplementary material or deposit them in any repository. Other than this, I am satisfied with the responses. Simulink files also need to be supplied because, after optimizing the variable, how these variables help the model to reduce the ripples during steady-state and dynamic operating conditions

- Thank you very much for the remark. In the appendix to the response to your review, we have presented in detail the step-by-step implementation of the two optimization procedures from points 4 and 5. We will also upload the Simulink file with the device model to the system. Please note that we have used the following version of MATLAB R2011b software. We hope we have not made it difficult for you to check our results. Please note that all the steps presented in point 4 are saved in the attached file KraevHinov_Patent1Simulink_sdosession.mat and for your convenience you can run it immediately to implement the described optimization procedure.

 Thank you very much for your remarks and comments. They were very useful for me to emphasize the main tasks and contributions of the manuscript, and also to focus the attention of the readers on the new and unique elements.

Author Response File: Author Response.doc

Reviewer 2 Report

The authors have carefully corrected the article according to the reviewer’s comments. The responses make sense and are objective. I haven’t any problem with the manuscript to be published.

Author Response

Thank you very much for your remarks and comments! They were very useful for me to emphasize the main tasks and contributions of the manuscript, and also to focus the attention of the readers on the new and unique elements.