Research on Energy Management Technology of Photovoltaic-FESS-EV Load Microgrid System

Round 1

Reviewer 1 Report (New Reviewer)

Comments and Suggestions for Authors

This paper presents high-quality research in the energy field, focusing on the management of a DC microgrid system that incorporates both PV and FESS resources. The document is well-structured, with clear sections on the introduction, methodology, and conclusions, all supported by results from a simulation case study.

Below are some suggested improvements and comments:

• Page 2, Lines 84-88: PMSM technology is introduced here, but its relevance to the paper’s main purpose is unclear. A brief yet clear explanation of how PMSM enhances the performance of the EMS should be added, with supporting references.

• Page 3, Lines 94-96: Please revise this sentence for clarity.

• Page 3, Lines 96-99: This statement is not universally applicable. Feedback to the AC grid depends on the policies of the grid operator and national or local regulations.

• Page 3, Lines 107-108: The sentence should read "[...] works in maximum power point tracking (MPPT) mode ...". The word "point" is missing.

• Page 4, Line 128: "DC/AC" is repeated and should be corrected.

• Page 7, Eq. 4: This equation assumes that all flywheels have the same inertia (J). In reality, this is rarely the case, even for units of the same model, and especially after maintenance or replacement operations. The paper should address this by acknowledging that the reference currents (ILi*) may have minor discrepancies from their real values, though these do not significantly affect the control strategy in Figure 5.

• Page 8, Figure 7: Please correct the second block on the right, where the FW unit should be labeled 2 instead of 1.

• Page 15, Line 483: The sentence is repeated (see lines 474-475). Please remove the redundancy.

• Pages 16-17: For clarity, Figures 12 and 13 should include an additional graphic showing the control mode for each time period.

• Page 18, Section 3.5: The simulation results do not mention the tuning of the PI controller parameters. Some information on these values should be provided, perhaps at the beginning of the section.

Author Response

Comment 1: Page 2, Lines 84-88: PMSM technology is introduced here, but its relevance to the paper’s main purpose is unclear. A brief yet clear explanation of how PMSM enhances the performance of the EMS should be added, with supporting references.

Response 1: Thank you for your correction. We explained the relevance and importance of PMSM in FESS by citing literature #13 in lines 84-86.

Comment 2: Page 3, Lines 94-96: Please revise this sentence for clarity.

Response 2:Thank you for your correction. We have made this statement in lines 94-96 clearer by revising it to read “The DC microgrid system is connected to the AC grid through a grid-connected converter, and when the DC microgrid system is operating in a grid-connected state, the AC grid inputs power to the DC microgrid system through the grid-connected converter to support the bus voltage of the DC microgrid system if the power emitted by the microgrid system itself cannot meet the consumption”

Comment 3: Page 3, Lines 96-99: This statement is not universally applicable. Feedback to the AC grid depends on the policies of the grid operator and national or local regulations.

Response 3:Thanks to your correction, We have deleted lines 96-99 from the original text.

Comment 4: Page 3, Lines 107-108: The sentence should read "[...] works in maximum power point tracking (MPPT) mode ...". The word "point" is missing.

Response 4: Thank you for your correction, We amend lines 107-108 of the original text to read “The PV power generation system works in the maximum power point tracking (MPPT) mode during normal operation to make use of solar energy as much as possible.”

Comment 5: Page 4, Line 128: "DC/AC" is repeated and should be corrected.

Response 5: Thank you for the correction. We have trimmed the redundant DC/AC.

Comment 6: Page 7, Eq. 4: This equation assumes that all flywheels have the same inertia (J). In reality, this is rarely the case, even for units of the same model, and especially after maintenance or replacement operations. The paper should address this by acknowledging that the reference currents (ILi*) may have minor discrepancies from their real values, though these do not significantly affect the control strategy in Figure 5.

Response 6: Thanks for the correction, We have added a remark in lines 243-244 “Ignore small differences between reference current and actual value.”

Comment 7: Page 8, Figure 7: Please correct the second block on the right, where the FW unit should be labeled 2 instead of 1.

Response 7: Thanks for the correction, We have modified Figure 7.

Comment 8: Page 15, Line 483: The sentence is repeated (see lines 474-475). Please remove the redundancy.

Response 8: Thanks for the correction, We have removed line 483 from the original text.

Comment 9: Pages 16-17: For clarity, Figures 12 and 13 should include an additional graphic showing the control mode for each time period.

Response 9: Thanks for the correction, because of the limited space in the picture in order to better show the waveform fluctuations in each stage, we have explained the operation model of each stage in Figures 12 and 13 in detail in the text below the picture.

Comment 10: Page 18, Section 3.5: The simulation results do not mention the tuning of the PI controller parameters. Some information on these values should be provided, perhaps at the beginning of the section.

Response 10: Thanks for the correction, for detailed information on the parameters of the Simulink modeled electrical system we have uploaded the model attachment for reference.

Reviewer 2 Report (New Reviewer)

Comments and Suggestions for Authors

This study focuses on the development and implementation of coordinated control and energy management strategies for a photovoltaic-flywheel energy storage system (PV-FESS)-electric vehicle (EV) load direct current (DC) microgrid. There are few comments:

1.      The novelty of the approach could be emphasized more clearly, as it’s not evident how this research improves upon existing methods in the literature.

2.      Although the review includes relevant studies, it would benefit from incorporating more recent research. In the introduction, the research background should be further described. It is advisable to incorporate more recent research, particularly the latest developments in the field.

 (a) Y. Yoldas et al., "A Framework-Based Multi-Agent Coordination for Enhanced Microgrid Energy Management at the Secondary Control Layer," in IEEE Transactions on Applied Superconductivity, vol. 34, no. 8, pp. 1-5, Nov. 2024.

(b) S. Huang et al., "Robust Distributed Fixed-Time Fault-Tolerant Control for Shipboard Microgrids With Actuator Fault," in IEEE Transactions on Transportation Electrification, doi: 10.1109/TTE.2024.3411289.

3.      While the paper presents a control strategy for energy management, the explanations are overly technical and lack an intuitive description. Providing more accessible descriptions of the control flow and its real-world relevance would make the paper easier to

 

4.      The simulation results section is well-structured, but it would benefit from more in-depth analysis. A quantitative comparison of the proposed method versus existing ones would make the results more compelling.

Author Response

Comment 1: The novelty of the approach could be emphasized more clearly, as it’s not evident how this research improves upon existing methods in the literature.

Response 1: Thank you for your correction. The specific innovations of this paper are as follows “In this chapter, according to the application environment of flywheel energy storage system, the photovoltaic flywheel small DC microgrid system is constructed. The unit control strategy of each subsystem of microgrid is analyzed, and the method of array cooperative control of flywheel energy storage system is studied. According to the energy flow and balance relationship of the microgrid system, the stable state and state switching conditions of the system are determined. The energy management strategy based on event management is designed to realize the cooperative control and stable operation of the system. The research results show that the flywheel energy storage array operation control strategy, which distributes energy storage and energy release power in equal proportion to the remaining energy of the energy storage unit, can ensure the synchronous operation of each flywheel energy storage unit, reduce the frequent switching of the flywheel unit, reduce the loss of the flywheel energy storage unit, and improve the operating efficiency of the energy storage system. An energy management strategy of photovoltaic flywheel DC microgrid system based on event management is studied. This strategy can control the input and output power of photovoltaic unit and flywheel energy storage unit harmoniously while maintaining the voltage stability of DC bus, so as to ensure the stable operation of microgrid system.”

Comment 2: Although the review includes relevant studies, it would benefit from incorporating more recent research. In the introduction, the research background should be further described. It is advisable to incorporate more recent research, particularly the latest developments in the field. (a) Y. Yoldas et al., "A Framework-Based Multi-Agent Coordination for Enhanced Microgrid Energy Management at the Secondary Control Layer," in IEEE Transactions on Applied Superconductivity, vol. 34, no. 8, pp. 1-5, Nov. 2024.

(b) S. Huang et al., "Robust Distributed Fixed-Time Fault-Tolerant Control for Shipboard Microgrids With Actuator Fault," in IEEE Transactions on Transportation Electrification, doi: 10.1109/TTE.2024.3411289.

Response 2:Thank you for your correction. We refer to these two articles in lines 28-32 to better introduce microgrid systems

Comment 3: While the paper presents a control strategy for energy management, the explanations are overly technical and lack an intuitive description. Providing more accessible descriptions of the control flow and its real-world relevance would make the paper easier to

Response 3:Thanks to your correction, The system model is described in detail and vividly in lines 488-502.

Comment 4: The simulation results section is well-structured, but it would benefit from more in-depth analysis. A quantitative comparison of the proposed method versus existing ones would make the results more compelling.

Response 4: Thank you for your correction, We list existing methods and compare them in detail in the introduction.

Reviewer 3 Report (New Reviewer)

Comments and Suggestions for Authors

The reviewer invites the authors to reply and take these comments into consideration to modify the paper accordingly as follows:

1.   The introduction section lacks from several important issues: a) The problem definition should be clearer more, b) the literature review and research gaps did not follow a straight path, it is advised that the authors give a deeper analysis on the ideas introduced in the literature c) contributions/novelty were not highlighted enough. The reviewer needs to see more to justify that this work gives new contributions. The motivation of the study should be further emphasized. In particular, the main contributions of the results in this paper should be clearly demonstrated.

Therefore, the introduction part should be improved and re-organized to cover three parts clearly and sequentially (To be easily understood for the reader) as follows: 1) motivation and incitement, and 2) literature review and research gaps, and 3) contributions and paper organization.

2.  The abstract does not cover the main numerical results, and the major conclusions captured from the study. On the other hand, the abstract mentions a "novel energy management strategy centered on event-driven mode switching." However, it does not clearly explain how this mode switching functions or what specific events trigger transitions between states. Additional clarification on the triggers and how the transitions impact the overall stability and efficiency of the microgrid would strengthen the manuscript.

3.     While the study investigates the control strategies for each subsystem within the PV-FESS-EV load DC microgrid, the abstract lacks a discussion of how these control strategies compare to existing methods. A comparison of the proposed control strategies with conventional or previously developed methods would help highlight the novelty and improvements in performance.

4.     While the paper focuses on the control strategies and energy management in a PV-FESS-EV microgrid, there is no mention of the scalability or practical challenges of implementing this system in real-world scenarios. It would be beneficial to discuss how these strategies could be adapted or modified for larger scale microgrids or different types of energy storage systems.

5.  The abstract states that the study provides insights into optimizing energy distribution and minimizing losses within the microgrid. However, it would be valuable to detail the specific mechanisms or methods used to achieve these reductions in energy losses. Additionally, quantifying energy savings compared to other systems would offer concrete evidence of the system’s efficiency.

6.     The simulation results presented in the paper appear somewhat underdeveloped and lack the depth needed to fully support the proposed control strategies. It would be beneficial to enhance the simulations by providing more detailed analyses and performance metrics, as well as considering additional test scenarios to further validate the system's effectiveness and robustness.

7.     The conclusions section lacks numerical results to support the findings and claims made throughout the paper. The absence of quantitative results, such as improvements in energy efficiency, reductions in power losses, or specific performance metrics, makes it difficult to assess the actual impact of the control strategies. Providing numerical results derived from simulations would greatly strengthen the validity and clarity of the conclusions.

8.     The reference list should be updated to include more recent and relevant studies that align with the paper's focus on energy management and control in PV-FESS systems. In addition, references that are less directly related to the main topic should be reconsidered or removed to ensure a stronger and more focused citation base, reflecting the latest advancements in this research area.

Less Relevant References:

Reference 4 (Ma et al., "Optimization Strategy for Fast Charging Station..."): While this discusses charging stations, it may be less directly relevant unless the paper includes specific analysis or comparisons of EV charging strategies in microgrids.

Reference 10 (Perveen, "Hybrid Optimal Coordination of Overcurrent Relay and Distance Relay..."): This reference discusses relay coordination for offshore wind farms, which may not directly tie into the manuscript's focus on energy management for PV-FESS systems unless a connection is explicitly drawn.

Comments on the Quality of English Language

Please improve the language of the paper in general during presenting the previous studies in the introduction an the whole manuscript. It should be presented clearly, simply and avoid declaration, sound more, for example using "this study" more when introduce the previous studies.

Author Response

Comment 1: The introduction section lacks from several important issues: a) The problem definition should be clearer more, b) the literature review and research gaps did not follow a straight path, it is advised that the authors give a deeper analysis on the ideas introduced in the literature c) contributions/novelty were not highlighted enough. The reviewer needs to see more to justify that this work gives new contributions. The motivation of the study should be further emphasized. In particular, the main contributions of the results in this paper should be clearly demonstrated.

Therefore, the introduction part should be improved and re-organized to cover three parts clearly and sequentially (To be easily understood for the reader) as follows: 1) motivation and incitement, and 2) literature review and research gaps, and 3) contributions and paper organization

Response 1: Thank you for your correction. We reorganized the introduction according to the order of motivation - current research gap - contribution, and added the cited papers to make the introduction more clear.

Comment 2: The abstract does not cover the main numerical results, and the major conclusions captured from the study. On the other hand, the abstract mentions a "novel energy management strategy centered on event-driven mode switching." However, it does not clearly explain how this mode switching functions or what specific events trigger transitions between states. Additional clarification on the triggers and how the transitions impact the overall stability and efficiency of the microgrid would strengthen the manuscript.

Response 2:Thank you for your correction. We have adjusted the summary to remove the numerical results and main conclusions, and the mode switching of "New energy management strategy centered on Event-driven mode switching" is clearly explained and described in lines 453-456.

Comment 3: While the study investigates the control strategies for each subsystem within the PV-FESS-EV load DC microgrid, the abstract lacks a discussion of how these control strategies compare to existing methods. A comparison of the proposed control strategies with conventional or previously developed methods would help highlight the novelty and improvements in performance.

Response 3:Thanks to your correction, In the last part of the introduction, the FESS studied in this paper is compared with the previously developed BESS system, the advantages and disadvantages of each are analyzed, and the novelty and performance improvement of FESS are emphasized.

Comment 4: While the paper focuses on the control strategies and energy management in a PV-FESS-EV microgrid, there is no mention of the scalability or practical challenges of implementing this system in real-world scenarios. It would be beneficial to discuss how these strategies could be adapted or modified for larger scale microgrids or different types of energy storage systems.

Response 4: Thank you for your correction, The current research focuses on simulation, which is the limitation of the current research. In the future research, we will apply it to the actual scenario.

Comment 5: The abstract states that the study provides insights into optimizing energy distribution and minimizing losses within the microgrid. However, it would be valuable to detail the specific mechanisms or methods used to achieve these reductions in energy losses. Additionally, quantifying energy savings compared to other systems would offer concrete evidence of the system’s efficiency.

Response 5: Thank you for the correction. Reducing the specific loss of energy is the focus of this paper, that is, "Energy management strategy for working mode transformation by event management", which is described in detail in the paper in lines 383-467.

Comment 6: The simulation results presented in the paper appear somewhat underdeveloped and lack the depth needed to fully support the proposed control strategies. It would be beneficial to enhance the simulations by providing more detailed analyses and performance metrics, as well as considering additional test scenarios to further validate the system's effectiveness and robustness.

Response 6: Thanks for the correction, The simulation results provided in this paper describe the flywheel energy storage state of each running stage in detail from the 6 working modes of the proposed strategy, which effectively proves that the strategy can reduce the loss of the flywheel energy storage unit and improve the operating efficiency of the energy storage system.

Comment 7: The conclusions section lacks numerical results to support the findings and claims made throughout the paper. The absence of quantitative results, such as improvements in energy efficiency, reductions in power losses, or specific performance metrics, makes it difficult to assess the actual impact of the control strategies. Providing numerical results derived from simulations would greatly strengthen the validity and clarity of the conclusions.

Response 7: Thanks for the correction, The detailed numerical quantitative results of this paper are given in detail in the simulation section. In addition to the simulation result graph, the results are explained in detail under each graph.

Comment 8: The reference list should be updated to include more recent and relevant studies that align with the paper's focus on energy management and control in PV-FESS systems. In addition, references that are less directly related to the main topic should be reconsidered or removed to ensure a stronger and more focused citation base, reflecting the latest advancements in this research area.

Response 8: Thanks for the correction, We have adjusted the irrelevant literature and added the latest research for reference.

Round 2

Reviewer 2 Report (New Reviewer)

Comments and Suggestions for Authors

All comments have been addressed.

Author Response

Thank you for your review！

Reviewer 3 Report (New Reviewer)

Comments and Suggestions for Authors

Although the authors modified the paper according to the comments, there are still some comments that the authors should take these comments into consideration.

The reviewer invites the authors to reply and take these comments into consideration to modify the paper accordingly as follows:

1.    Please do your best to summarize the novelty and contributions in bullets at the end of the introduction. Also, write the main structure of the paper at the end of the introduction section.

2.    The abstract should be improved including the main numerical results, and the major conclusions captured from the study. Both the original and the revised manuscript do not have any numerical results.

3.    The conclusions section lacks the main numerical results to support the findings and claims made throughout the paper. The absence of quantitative results, such as improvements in energy efficiency, reductions in power losses, or specific performance metrics, makes it difficult to assess the actual impact of the control strategies. Providing numerical results derived from simulations would greatly strengthen the validity and clarity of the conclusions.

Therefore, the authors should insert the main numerical results into the conclusion part.

4.    Line 71, the authors should put the full stop (.) after the [13] not before. Please check this repeated error through the paper.

Author Response

Comment 1: Please do your best to summarize the novelty and contributions in bullets at the end of the introduction. Also, write the main structure of the paper at the end of the introduction section.

Response 1: Thank you for your correction. We summarize the novelty and main conclusions of this study in lines 73-80 of the introduction section.

Comment 2: The abstract should be improved including the main numerical results, and the major conclusions captured from the study. Both the original and the revised manuscript do not have any numerical results.

Response 2:Thank you for your correction. After carefully considering your suggestions, we have revised the abstract section and added important numerical results.

Comment 3: The conclusions section lacks the main numerical results to support the findings and claims made throughout the paper. The absence of quantitative results, such as improvements in energy efficiency, reductions in power losses, or specific performance metrics, makes it difficult to assess the actual impact of the control strategies. Providing numerical results derived from simulations would greatly strengthen the validity and clarity of the conclusions.

Therefore, the authors should insert the main numerical results into the conclusion part.

Response 3:Thanks to your correction, In the conclusion of this paper, it is stated that this study reduces the frequent switching of flywheel units, reduces the loss of flywheel energy storage units, and improves the operational efficiency of the energy storage system, and other quantitative index results.

Comment 4:Line 71, the authors should put the full stop (.) after the [13] not before. Please check this repeated error through the paper.

Response 4: Thank you for your correction, We fixed the punctuation error here and rechecked the formatting of the article again.

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. In Fig. 1: the definition of the “PMSM” is not given before. So, it is not clear.

2. Check page 2, line 58 for the full stop instead of comma.

3. Fig. 10 should be changed to a better one.

4. Fig. 11 should be changed to a better one.

5. Fig. 12 and 13 should be enlarged.

6. Paper deals with cooperative control and energy management strategies of a PV-FESS-EV load DC microgrid system. However, there is limited data on electric vehicle load system. So it can be assumed as a regular DC loads. It is better to remove “EV” from the title if EV charging profile and it’s specific behavior has not been considered.

7. Main contributions of the study is missing. Please consider to add clearly.  If the main contributions are mainly based on the coordinated control of the microgrid, the title should be revised to better reflect the study.

8. The structure given in Fig. 1 and the model of the DC-grid in MATLAB in Fig. 11 are different. It is not clear in the study what components are included in the simulation.

9. Literature review missing and must be given. Similar and recent studies with findings should be evaluated and the difference/contributions of your study should be highlighted.

Comments on the Quality of English Language

English language fine.

Author Response

Dear Reviewer,

We appreciate the constructive feedback provided by the reviewers, which has helped us to significantly improve the quality of our work. Below, we address each revision point and describe the changes we have made accordingly.

Comments 1: In Fig. 1: the definition of the “PMSM" is not given before. So, it is not clear

Response 1: Thank you for pointing this out. We agree with this comment. Therefore, we have added the definition of the “PMSM” in line 77.

Comments 2: Check page 2, line 58 for the full stop instead of comma.

Response 2: Thank you for pointing this out. The content has been corrected in line 68-72.

Comments 3: Fig. 10 should be changed to a better one.

Response 3: Thank you for pointing this out. We agree with this comment. Therefore, figure 10 has been changed to a better one.

Comments 4: Fig. 11 should be changed to a better one.

Response 4: Thank you for pointing this out. We agree with this comment. Therefore, figure 11 has been changed to a better one.

Comments 5: Fig. 12 and 13 should be enlarged.

Response 5: Thank you for pointing this out. We agree with this comment. Therefore, figure 12 and 13 have been enlarged.

Comments 6: Paper deals with cooperative control and energy management strategies of a PV-FESS-EV load DC microgrid system. However, there is limited data on electric vehicle load system. So it can be assumed as a regular DC loads. It is better to remove “EV” from the title if EV charging profile and it’s specific behavior has not been considered.

Response 6: Thank you for pointing this out. We agree with this comment. Therefore, we have removed “EV” from the title.

Comments 7: Main contributions of the study is missing. Please consider to add clearly.  If the main contributions are mainly based on the coordinated control of the microgrid, the title should be revised to better reflect the study.

Response 7: Thank you for pointing this out. We agree with this comment. Therefore, the main contributions have been added in the abstract (line 18-20) and conclusion (line 577-283).

Comments 8: The structure given in Fig. 1 and the model of the DC-grid in MATLAB in Fig. 11 are different. It is not clear in the study what components are included in the simulation.

Response 8: Thank you for pointing this out. We agree with this comment. Therefore, figure 11 has added the AC load and its converter.

Comments 9: Literature review missing and must be given. Similar and recent studies with findings should be evaluated and the difference/contributions of your study should be highlighted.

Response 9: Thank you for pointing this out. We agree with this comment. Therefore, literature review has been added in the introduction section.

We have also made some minor corrections to grammar, spelling, and formatting throughout the paper to ensure consistency and clarity. The revised version of the manuscript is attached.

Please let us know if there are any further revisions required. We look forward to hearing from you soon and appreciate your support in advancing our research.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The paper is very interesting and provides new knowledge on microgrids decision making.

However:

1. It should clearly stated that this research is based on simulation results and not on an experimental setup

2. The introduction should be enriched and reconstructed for providing info related to the state of the art and beyond of this research. Outstanding issues and future trends should be also included.

3. It will be wise to include a short paragraph referred to the simulation environment. Only in Fig.11 there is a reference for Matlab.

4. The quality of the figures should be improved (like Fig.11, 9 and others)

5. It is proposed to extend the outcome of the results and to promote the scientific impact of this work.

Comments on the Quality of English Language

The quality of the English is sufficient enough. Some phrases in summary and introduction are repeated and it will be wise to reconstruct it accordingly.

Author Response

Dear Reviewer,

We appreciate the constructive feedback provided by the reviewers, which has helped us to significantly improve the quality of our work. Below, we address each revision point and describe the changes we have made accordingly.

     

       Comments 1: It should clearly stated that this research is based on simulation results and not on an experimental setup.?

        Response 1: Thank you for pointing this out. We agree with this comment. Therefore, the effectiveness of the individual control strategies is based on simulation results. (Line 7-9)

          Comments 2: The introduction should be enriched and reconstructed for providing info related to the state of the art and beyond of this research. Outstanding issues and future trends should be also included.?

         Response 2: Thank you for pointing this out. We agree with this comment. Therefore, the introduction has been expanded to incorporate a detailed state-of-the-art review, addressing key issues and future trends relevant to this research. (Line 29-84)

         Comments 3: It will be wise to include a short paragraph referred to the simulation environment. Only in Fig.11 there is a reference for Matlab.?

 Response 3: Thank you for pointing this out. We agree with this comment. Therefore, we have added a paragraph in the methodology section detailing the simulation environment, including the use of Matlab, as requested. (Line 489-493)

         Comments 4: The quality of the figures should be improved (like Fig.11, 9 and others)

 Response 4: Thank you for pointing this out. We agree with this comment. Therefore, we have enhanced the quality of all figures, including Figures 9 and 11, to meet the required standards.

 

        Comments 5: It is proposed to extend the outcome of the results and to promote the scientific impact of this work.

Response 5: Thank you for pointing this out. We agree with this comment. Therefore, we have expanded the discussion of our results to better highlight their scientific impact and significance. (Line 568-572)

 

We have also made some minor corrections to grammar, spelling, and formatting throughout the paper to ensure consistency and clarity. The revised version of the manuscript is attached.

Please let us know if there are any further revisions required. We look forward to hearing from you soon and appreciate your support in advancing our research.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The paper presents a control strategy and management system for a small DC microgrid involving Photovoltaics, Flywheels and EV load (which in truth is just a load, as nothing in the paper suggest it has been model as an EV load).

The paper has several major drawbacks, with the most notable:

1. not all acronyms and abbreviations have been introduced or used properly, e.g. FESS-EV, MPPT, CMC.

2. on line55 the authors wrote that the DC microgrid system consists of grid-connected system. It is not clear what grid-connected system is this about. Do you mean the grid-connected AC-DC converter?

3. on line 90 the authors wrote that the reliability if the DC microgrid system has been improved through energy distribution adjustment of the flywheel? However, this claim has not been backed-up with data or citations. Please argument your statement.

4. Figure 2 is not properly explained. For example there is no PLL shown and there are blocks (e.g. the one with 6 arrows inside) not explained. Quantities not explained.

5. in line 166 it is claimed that flywheel storage systems play a pivotal role in maintaining power balance within microgrids. Do you refer to your DC microgrid or is this a general statement. Please clarify  and give arguments for it.

6.  Figure 4 is not properly explained, and quantities/acronyms are not explained in the text (some are, but much later).

7. Please state what is J in equation (1)? E_mi is explained 2 times in 202-203, which makes it not clear.

8. In (3) and (4), P_m seems to be a power quantity, but you wrote in line 213 that it is an energy quantity. E_m is indeed used in Figure 5, but then never explained. Please correct all these.

9. Figure 6 is missing entirely.

10. It is unclear what do you mean by "limit output power" (line 251, line 280) and output limit power (line 275). Please make sure you always use the same term for the same quantity. And please re-phrase/re-explain its meaning.

11. What/which is the "bottom controller" you refered to in line 268?

12. In some instances the same text is repeated again in the paper. Just one example for this: the idea/text on line 337-339 has been written in lines 324-326. Same for text on line 418-421.

13. In lines 390-391, I_F_max seems to denote the charging/discharging current and the current limit for charging/discharging of the flywheel. The rotational speed notations used in Table 2 are not the same as the ones used in text.

14. Figure 10 is incomplete. Please show all blocks.

15. Please include in the paper the parameters of the electrical system you modeled in Simulink. You must give sufficient details so that it can be reproduced by other engineers.

16. Please replace Figure 11 with a clear figure showing the system you modelled in Matlab.

17. What is Figure 5-12 you state on line 459? Please correct.

18. Figures 12 and 13 do not have good quality and are too small. Please replace.

19. What is novelty of you paper? And what is the main contribution of the authors?

20. The control strategy and management system proposed by the authors must be compared against other similar control/management systems from the literature. This is missing from the paper, as seems to be no clear purpose on why the authors chose to implement the proposed microgrid in Simulink in the first place.

Considering all these drawbacks, and the extended English editing required by this paper, I can only recommend to the authors to resubmit the paper once it has been significantly improved. Very importantly, please compare your work with the one described in the existing literature, highlighting in which way yours is different or better.

Comments on the Quality of English Language

The quality of English is acceptable in some parts of the submitted paper. However, there are many typos and mistakes in several phrases, including sentences without verbs. This makes it difficult to understand the paper and I strongly recommend to the authors to use a native English speaker to correct their manuscript.

Author Response

Dear Reviewer,

We appreciate the constructive feedback provided by the reviewers, which has helped us to significantly improve the quality of our work. Below, we address each revision point and describe the changes we have made accordingly.

Comments 1: not all acronyms and abbreviations have been introduced or used properly, e.g. FESS-EV, MPPT, CMC.

Response 1: Thank you for pointing this out. We agree with this comment. Therefore, we have added the explanation in abstract and introduction.

Comments 2: on line55 the authors wrote that the DC microgrid system consists of grid-connected system. It is not clear what grid-connected system is this about. Do you mean the grid-connected AC-DC converter?

Response 2: Thank you for pointing this out. We agree with this comment. Therefore, we have added the explanation in line 65-68.

Comments 3: on line 90 the authors wrote that the reliability if the DC microgrid system has been improved through energy distribution adjustment of the flywheel? However, this claim has not been backed-up with data or citations. Please argument your statement.

Response 3: Thank you for pointing this out. We agree with this comment. Therefore, we have added the explanation in line 113 -116.

Comments 4: Figure 2 is not properly explained. For example there is no PLL shown and there are blocks (e.g. the one with 6 arrows inside) not explained. Quantities not explained.

Response 4: Thank you for pointing this out. We agree with this comment. Therefore, we have added the explanation in line 145-150.

Comments 5: in line 166 it is claimed that flywheel storage systems play a pivotal role in maintaining power balance within microgrids. Do you refer to your DC microgrid or is this a general statement. Please clarify and give arguments for it.

Response 5: Thank you for pointing this out. It’s a general statement, the paragraph has been modified.

Comments 6: Figure 4 is not properly explained, and quantities/acronyms are not explained in the text (some are, but much later).

Response 6: Thank you for pointing this out. We agree with this comment. The quantities/acronyms have been added in abstract and introduction section.

Comments 7: Please state what is J in equation (1)? E_mi is explained 2 times in 202-203, which makes it not clear.

Response 7: Thank you for pointing this out. We agree with this comment. Therefore, we have added the explanation of J (line 229). J is the rotor inertia. The repeated explanation of E_mi has been deleted.

Comments 8: In (3) and (4), P_m seems to be a power quantity, but you wrote in line 213 that it is an energy quantity. E_m is indeed used in Figure 5, but then never explained. Please correct all these.

Response 8: Thank you for pointing this out. We agree with this comment. Therefore, the mistakes have been corrected in line 237 and line 239-241.

Comments 9: Figure 6 is missing entirely.

Response 9: Thank you for pointing this out. We agree with this comment. Therefore, figure 6 has been added.

Comments 10: It is unclear what do you mean by "limit output power" (line 251, line 280) and output limit power (line 275). Please make sure you always use the same term for the same quantity. And please re-phrase/re-explain its meaning.

Response 10: Thank you for pointing this out. We agree with this comment. Therefore, they are now been used in the same term.

Comments 11: What/which is the "bottom controller" you refered to in line 268?

Response 11: Thank you for pointing this out. We agree with this comment. Therefore, we have changed “bottom controller” to “underlying controller” explained in section2.4.

Comments 12: In some instances the same text is repeated again in the paper. Just one example for this: the idea/text on line 337-339 has been written in lines 324-326. Same for text on line 418-421.

Response 12: Thank you for pointing this out. We agree with this comment. Therefore, the text in line 324-326 has been removed. But we think the text in line 418-421 is needed for explanation.

Comments 13: In lines 390-391, I_F_max seems to denote the charging/discharging current and the current limit for charging/discharging of the flywheel. The rotational speed notations used in Table 2 are not the same as the ones used in text.

Response 13: Thank you for pointing this out. We agree with this comment. Therefore, the mistake has been corrected in lines 413 and 416.

Comments 14: Figure 10 is incomplete. Please show all blocks.

Response 14: Thank you for pointing this out. We agree with this comment. Therefore, the last two blocks have been changed.

Comments 15: Please include in the paper the parameters of the electrical system you modeled in Simulink. You must give sufficient details so that it can be reproduced by other engineers.

Response 15: Thank you for pointing this out. We agree with this comment. Therefore, more Simulink model details have been added at the beginning of section 3.5.1.

Comments 16: Please replace Figure 11 with a clear figure showing the system you modelled in MATLAB.

Response 16: Thank you for pointing this out. We agree with this comment. Therefore, figure 11 has been replaced.

Comments 17: What is Figure 5-12 you state on line 459? Please correct.

Response 17: Thank you for pointing this out. We agree with this comment. Therefore, it has been corrected into Figure 12.

Comments 18: Figures 12 and 13 do not have good quality and are too small. Please replace.

Response 18: Thank you for pointing this out. We agree with this comment. Therefore, the figures have been replaced.

Comments 19: What is novelty of you paper? And what is the main contribution of the authors?

Response 19: Thank you for pointing this out. We agree with this comment. Therefore, we have added these two aspects in abstract (line 18-22) and conclusion (line 577-582).

Comments 20: The control strategy and management system proposed by the authors must be compared against other similar control/management systems from the literature. This is missing from the paper, as seems to be no clear purpose on why the authors chose to implement the proposed microgrid in Simulink in the first place.

Response 20: Thank you for pointing this out. We agree with this comment. Therefore, literature review part has been added in the introduction section.

We have also made some minor corrections to grammar, spelling, and formatting throughout the paper to ensure consistency and clarity. The revised version of the manuscript is attached.

Please let us know if there are any further revisions required. We look forward to hearing from you soon and appreciate your support in advancing our research.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

On page 2, there is no need to indicate “In response to the reviewer's comment,”. Please remove this.

In fig. 4, “PMSM” term can be used instead of “BLDCM”

 

Use “Permanent Magnet Synchronous Machine” instead of “Permanent Magnet Synchronous Motor” because the flywheel works both as a motor and generator.

Author Response

Comments1:On page 2, there is no need to indicate “In response to the reviewer's comment,”. Please remove this.

Response1:Of course,We have deleted the text in question.

Comments2:In fig. 4, “PMSM” term can be used instead of “BLDCM”.

Response2:Yes,We have made modifications and adjustments to Figure 4

Comments3:Use “Permanent Magnet Synchronous Machine” instead of “Permanent Magnet Synchronous Motor” because the flywheel works both as a motor and generator.

Response3:Yes,We have made modifications and adjustments to the acronym.

 

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The following of my previous comments have not been addressed properly or need additional work:  

Comment 1. Some acronyms are introduced several times. Ensure that these are introduced only once in your paper.  

Comment 3. There is no data given and no citation to back-up author's claim. 

Comment 4. Authors have not addressed this comment properly, as not all blocks have a name written in the figure, nor description in the paper's text.  

Comment 5. If it is a general statement, please back-it up with references. Many microgrids work fine without fly-wheels.  

Comment 6. BLDCM is not explained in text - at least the full name of the acronym shall be given.  

Comment 8. Authors wrote "total energy power (W)". Please make up your mind, the unit is for power, so why energy?  

Comment 14. Which are the other events / actions? Are they described or given in text?  

Comment 15. Grid data, load data converter data is still missing.  

Comment 20. I suggest that on line 52 the authors remove "In response to reviewer's comment".

Also, the authors did not made a comparison between their control method and the methods employed by other papers.

 

Comments on the Quality of English Language

Not evaluated since a clean version of the paper has not been included in author's submission.

Author Response

Comments1:Some acronyms are introduced several times. Ensure that these are introduced only once in your paper. 

Response1:Yes,We have made modifications and adjustments to the abbreviations that repeatedly appear in the article.

Comments3:There is no data given and no citation to back-up author's claim. 

Response3:Yes,We provide detailed experimental data in Table 4 and Figure 8-13 to support it.

Comments4:Authors have not addressed this comment properly, as not all blocks have a name written in the figure, nor description in the paper's text. 

Response4:Yes,We have provided specific and detailed explanations below the icons for each small image in Figures 12-13.

Comments5:If it is a general statement, please back-it up with references. Many microgrids work fine without fly-wheels. 

Response5:Yes,We use a flywheel energy storage array system to stabilize the bus voltage, distribute energy storage and release power in an equal proportion during load switching, ensuring synchronous operation of each flywheel energy storage unit and improving the system's operational efficiency.

Comments6:BLDCM is not explained in text - at least the full name of the acronym shall be given. 

Response6:Yes,We have changed BLDCM to 'Permanent Magnet Synchronous Machine'

Comments8:Authors wrote "total energy power (W)". Please make up your mind, the unit is for power, so why energy?  

Response8:Yes,This is the unit used for flywheel energy storage systems.

Comments14:Which are the other events / actions? Are they described or given in text?    

Response14:Yes,All events have been provided in the text.

Comments15: Grid data, load data converter data is still missing.  

Response15:Yes,The power grid data and load data have been provided in Table 4 and various experimental result graphs.

Comments20: I suggest that on line 52 the authors remove "In response to reviewer's comment". 

Response20:Of course,We have deleted the text in question.

We have cited other papers and conducted methodological comparisons in the introduction section

Author Response File: Author Response.pdf

Round 3

Reviewer 3 Report

Comments and Suggestions for Authors

The authors are not addressing all of my previous comments thoroughly. The following comments are still pending.

·        C1. My previous Comment has not been addressed properly:

-        The authors have introduced PV abbreviation more than once and continue to use in the paper both PV and Photovoltaic.

-        MPPT has also been introduced more than once.

-        Constant Voltage Control (CVC) has also been introduced more than once.

-        CMC does not fit with Constant Voltage Mode.

I already raised this issues 2 times before but authors failed to correct it: all acronyms must be introduced only the first time they are used in text.

·         C3. The author’s claim is not backed by data or citations – the simulations results are only covering the microgrid with the FESS. There is no comparison with results for microgrid without FESS. Such comparison is necessary in order to claim that the FESS improves the stability and reliability of the microgrid.

·        C4. My initial comment did not refer to Figures 12 and 13. This is my initial Comment 4:

“Figure 2 is not properly explained. For example, there is no PLL shown and there are blocks (e.g. the one with 6 arrows inside) not explained. Quantities not explained.”

·        C5. Again, my comment has not been addressed. The authors continue to claim in a general statement, therefore not necessarily related to their work, that: “In general, flywheel energy storage systems play a pivotal role in maintaining power balance within microgrids”. This obviously not true, as many microgrids in the world work just fine without flywheels. So please remove your statement or back it up by relevant citations.

·        C8. Comment not addressed. The quantities in question are either power quantities or energy quantities, but they cannot be both in the same time. Obviously, P_mi and P_m are power quantities, so remove the world “energy” from their name. Correct everywhere you have the followings: “energy storage power” and “total energy power”.

·        C14. Comment not addressed properly. Please include in your response on what lines in text are the “Other actions” described. Are these “other actions” the modes that you described in text? If yes, remove “Other actions” from Figure 10 and include all the modes in flowchart. If you do not include all the modes, clearly state in the main text in the author’s reply why you replaced the modes with “Other actions”.

·        C15. Table 4 includes motor data only. There is no data for the grid, loads and converter.

 

Comments on the Quality of English Language

Same comment as in previous iteration.

Author Response

评论 1：我之前的评论没有得到妥善处理：

- 作者不止一次地引入了 PV 缩写，并在论文中继续使用 PV 和 Photovoltaic。

- MPPT 也被不止一次地引入。

- 恒压控制 （CVC） 也已不止一次推出。

- CMC 不适用于恒压模式。

我之前已经提出了这个问题 2 次，但作者未能纠正它：所有首字母缩略词都必须在第一次在文本中使用时引入。

回应 1：感谢您的指正。我们检查了全文，并将 Photovoltaic、maximum power tracking 和 Constant Voltage Control 替换为缩写（第一次引用除外），并删除了缩写 CMC。

评论 3：作者的说法没有数据或引文支持——仿真结果仅覆盖了带有 FESS 的微电网。与没有 FESS 的微电网的结果没有可比性。为了声称 FESS 提高了微电网的稳定性和可靠性，这种比较是必要的。

回应 3：感谢您的指正。在引言的第 59-66 行中，我们引用了没有 FESS 的 BESS 微电网进行比较，这表明包含 FESS 提高了微电网的稳定性和可靠性。

评论 4：我最初的评论没有提到图 12 和图 13。这是我最初的评论 4：

“图 2 没有得到适当的解释。例如，没有显示 PLL，并且有块（例如，里面有 6 个箭头的那个）没有解释。数量没有解释。

响应 4：感谢您的更正，我们在第 3.1 节中进行了一段更改，以更详细地解释图 2，并为图 2 中的逆变器添加了注释。

评论 5：同样，我的评论尚未得到解决。作者继续在一般性声明中声称，因此不一定与他们的工作相关，“一般来说，飞轮储能系统在维持微电网内的电力平衡方面发挥着关键作用”。这显然不是真的，因为世界上许多微电网在没有飞轮的情况下都能正常工作。因此，请删除您的陈述或通过相关引用来支持它。

回复 5：感谢您的指正，我们已经进行了相关研究以确认您的观点，并删除了“一般来说，飞轮储能系统在维持内部电力平衡方面起着关键作用 一般来说，飞轮储能系统在维持微电网内部的电力平衡方面起着关键作用”已被删除。

评论 8：评论未解决。所讨论的量要么是功率量，要么是能量量，但它们不能同时是两者。显然，P_mi 和 P_m 都是功率，因此请从它们的名称中删除世界“能量”。在有以下内容的地方进行更正：“energy storage power” 和 “total energy power”。

回应 8：感谢您的更正。我们更正了“储能功率”和“总能量功率”的内容。

评论 14：评论未正确处理。请在您的回复中包括文本中的哪些行描述了 “其他操作”。这些 “其他操作” 是你在文本中描述的模式吗？如果是，则从图 10 中删除 “Other actions” 并包括流程图中的所有模式。如果您没有包含所有模式，请在作者的回复中清楚地说明为什么您将模式替换为 “Other actions” 模式。

响应 14：感谢您的更正，我们已将图 10 中的其他操作替换为省略号，这是指一直迭代。

评论 15： 请在论文中包括您在 Simulink 中建模的电气系统的参数。您必须提供足够的详细信息，以便其他工程师可以复制它。

回应 15：感谢您的指正。我们在附件中添加了有关负载和转换器的更详细数据。