Grid Connected Microgrid Optimization and Control for a Coastal Island in the Indian Ocean
Round 1
Reviewer 1 Report
This paper analyzes the possibility of a hybrid renewable microgrid that is dispatch strategy-governed in both off-grid and on-grid scenarios for a suggested site in Maldives. Both the power system response study and the techno-environmental economic analysis of the proposed microgrid were carried out using DIgSILENT Power Factory and HOMER respectively. After going through the paper, I found some concerns, as listed below:
1. More in-depth analysis of the author's contribution of this paper in the introduction section. Moreover, I would like to see more discussion of the literature so that I can clearly identify the article relates to competing ideas.
2. There are several up-to-date approaches for the idea. Authors should look for these approaches, compare the results and prove their idea. This is the major concern.
3. Major clarifications and explanations are needed make the contributions of the paper clearly stand out. There exist many works that are focusing on energy management through microgrids considering different distributed means of generation, responsive loads, storage units, and in the presence of uncertainties. The novelty of the present work should be well stated and justified. The new author's contribution should be justified regarding the previous works in the literature. (such as https://doi.org/10.1016/j.csite.2022.102442, https://doi.org/10.3390/su142113765 and many more).
4. The authors must clarify how their approach works for larger test cases with thousands of variables. What's the performance of the method in large-scale optimization problem?.
5. Author must justify the choice of solution method. What is the rationale behind using such optimization method and not to use other mathematical-based approaches? How do authors guarantee optimality of the obtained solutions?.
6. Does the proposed approach guarantee the converging to the global optima or close to the global optima? Authors should talk about how far the obtained solutions are from the global optima.
7. The authors must explain how their approach can handle the uncertainties.
8. What's the sensitivity of the model with the change of computational parameters?.
9. The cost details including the interest rate and inflation for the utilized units are missing.
10. The paper needs another technique for system sizing to compare the results with (i.e. PSO, GA, MFO …).
Author Response
Reviewer#1, Concern #: This paper analyzes the possibility of a hybrid renewable microgrid that is dispatch strategy-governed in both off-grid and on-grid scenarios for a suggested site in Maldives. Both the power system response study and the techno-environmental economic analysis of the proposed microgrid were carried out using DIgSILENT Power Factory and HOMER respectively. After going through the paper, I found some concerns, as listed below:
Author response: The authors would like to thank the respected reviewer for the valuable comments and time in reviewing the manuscript. The authors appreciate the valuable thinking and effort of the respected reviewer and have given highest priority to satisfy the issues raised by the honorable reviewer.
The authors have considered the comment of the respected reviewer with the highest priority and have corrected the manuscript accordingly. The authors do believe that the comments of the respected reviewer will definitely help enhancing the quality and acceptability of the manuscript.
Author action: N/A
Reviewer#1, Concern # 1: More in-depth analysis of the author's contribution of this paper in the introduction section. Moreover, I would like to see more discussion of the literature so that I can clearly identify the article relates to competing ideas.
Author response: The authors thank the respected reviewer for the valuable comments and critical findings.
Author action: The work has now been updated according to the comments of the respected reviewer. The authors have now added more clarification about the contributions of this research work. Now a point-by point contribution list is provided so that the significance of the work is more clarified to the readers (lines 194-203). Also, more critical discussion of the presented literatures and new literatures are now included to prove the novel contribution of this work according to the comment of the respected reviewer (lines 65-88, 97-112, 116-148, 153-166, references 21, 22, 27, 40, 41).
Reviewer#1, Concern # 2: There are several up-to-date approaches for the idea. Authors should look for these approaches, compare the results and prove their idea. This is the major concern.
Author response: The authors thank the respected reviewer for the critical comment and wonderful suggestion. The authors have followed the previous comment of the respected reviewer and have updated the introduction section accordingly by including more literatures on similar research works and have also clarified the main contribution of this research work which proves the significance of the work in this research domain.
According to the valuable comment of the respected reviewer, in result section the authors have felt the necessity of including a comparison among different approaches to prove the significance of this idea. Now it has been included (Section 3.5, line 461-482, table 2, 3). Hope this satisfies the respected reviewer.
Author action: Now the issue has been addressed by including a comparison sub-section in the result section where other optimization methods and another similar work are compared with the proposed one (Section 3.5, line 461-482, table 2, 3).
Reviewer#1, Concern # 3: Major clarifications and explanations are needed make the contributions of the paper clearly stand out. There exist many works that are focusing on energy management through microgrids considering different distributed means of generation, responsive loads, storage units, and in the presence of uncertainties. The novelty of the present work should be well stated and justified. The new author's contribution should be justified regarding the previous works in the literature. (such as https://doi.org/10.1016/j.csite.2022.102442, https://doi.org/10.3390/su142113765 and many more).
Author response: The authors thank the respected reviewer for raising this important issue and for the valuable suggestion.
According to the comments of the respected reviewer, the core contribution of this research work has been further clarified and explained in the introduction now. The introduction part has been updated accordingly. Also, according to the comment, a comparison section is introduced in the result section which further clarifies the contribution. The suggested works by the respected reviewer have also been studied and cited in the reference list. The core contribution of this work is that, the implementation of dispatch strategy based control in designing and operating a hybrid microgrid system where the performance of the microgrid has been evaluated by assessing the power system responses and the work has been done by considering both off and on grid microgrid and now also a comparison with other works. The total concept is not present in the available research works. Now the manuscript has been corrected accordingly and hope this satisfies the respected reviewer.
Author action: Now the issue has been further clarified and the introduction, literature review, reference list and result section has been updated according to the comment to prove the contribution. Also, the contribution is presented in a point-by point fashion within the last part of the literature. Please see. lines 65-88, 97-112, 116-148, 153-166, references 21, 22, 27, 40, 41, Section 3.5, line 461-482, table 2, 3.
Reviewer#1, Concern # 4: The authors must clarify how their approach works for larger test cases with thousands of variables. What's the performance of the method in large-scale optimization problem?
Author response: The authors thank the respected reviewer for raising this important issue.
The approach for larger test cases will be conducted by using same methodological approach to optimize the system for minimizing the NPC, COE and carbon emission. For the larger scale optimization problems the stochastic nature of the solar radiation, wind speed and temperature will be considered to justify the overall performance of the system.
Author action: N/A
Reviewer#1, Concern # 5: Author must justify the choice of solution method. What is the rationale behind using such optimization method and not to use other mathematical-based approaches? How do authors guarantee optimality of the obtained solutions?
Author response: The authors thank the respected reviewer for raising this important issue.
The reason for choosing HOMER based method rather than other mathematical approaches in finding the optimal solution is that HOMER has some superiority over the other methods. HOMER is a user-friendly environment offering faster convergence rate, uses deterministic algorithm and provides accurate results and it has less complexity. Other models cannot model the back up diesel generator and battery storage units and the stochastic nature of the renewables.
From HOMER, the obtained results shown in table 1 are optimum. Optimization is done here to minimize the NPC, COE, green house gas, component sizing etc. From table 1 it is evident that, the results are minimum to satisfy the load demand optimally. Also, the power system responses show a stable and feasible response from the HOMER optimized results. So, it can be said that the results from HOMER are optimal ones.
Author action: The justification of the choice of the solution method and rationale behind using HOMER optimizer has now been addressed in 194- 203, 236-240.
The guarantee of the optimality of the obtained solutions has been described in lines 315-319, sections 3.1-3.4.
Reviewer#1, Concern # 6: Does the proposed approach guarantee the converging to the global optima or close to the global optima? Authors should talk about how far the obtained solutions are from the global optima.
Author response: The authors thank the respected reviewer for raising this important issue.
Yes, the proposed approach guarantees the converging to the global optima. The obtained solutions are in line with the global optima in terms of NPC, COE and carbon emission and the designed system will be applicable for the area where the meteorological condition and load demand profile is similar.
The proposed solution can be justified for global optima according to the different dispatch strategies based on available renewable resources.
Author action: Now lines 319-324 contains the discussion in the manuscript.
Reviewer#1, Concern # 7: The authors must explain how their approach can handle the uncertainties.
Author response: The authors thank the respected reviewer for raising this important and critical issue.
The research approach explained in this research work can handle uncertainty issues like solar and wind resource variations. The other uncertain or sensitivity parameters like inflation etc. have not been considered in this present version of work to keep things limited to keep focus on the main contribution of this research work which is dispatch strategy-based analysis. The sensitivity analysis has been kept as future work. The approach as explained in the research methodology considers the uncertain characteristics of solar and wind profile and provides feasible solution considering the uncertainty.
Author action: According to the comment, now the manuscript contains the discussion in the manuscript in lines 324-331.
Reviewer#1, Concern # 8: What's the sensitivity of the model with the change of computational parameters?
Author response: The authors thank the respected reviewer for raising this important issue. The model is obviously sensitive to various sensitivity parameters like, costs of different components, yearly increment, initial investment, replacement costs, rate of rebate etc. The core concern of this very research work is to design the microgrid for it’s optimum operation offering least costs, environmental impact and component sizes. Besides that dispatch strategy based control is applied to further optimize the solution as dispatch strategy has overall impact on the systems sizing, costing and overall performances. Upon their mutual performances best and worst dispatch cases have been determined. As our main concern/ contribution of this work is not showing the impact of sensitivity analysis, the sensitivity analysis has been considered as a future work which is now mentioned in the future research idea section (last part of conclusion) of the manuscript.
Author action: In conclusion future research direction is now added within the manuscript to highlight the shortcomings of this research work and to mention some future research concepts that might be thought while extending the present research work. The issue is now discussed in lines 324-331 and 535-537.
Reviewer#1, Concern # 9: The cost details including the interest rate and inflation for the utilized units are missing.
Author response: The authors thank the respected reviewer for raising this important issue. The cost detailing, inflation rates etc. for the research and other specifications and information are now provided as additional data in the newly added appendix section. Hope the corrections satisfy the respected reviewer.
Author action: Appendix section is added in pages 19-21.
Reviewer#1, Concern # 10: The paper needs another technique for system sizing to compare the results with (i.e. PSO, GA, MFO …).
Author response: The authors thank the respected reviewer for raising this important issue. The critical issue has been responded by the authors by incorporating some recent works within our proposed work by introducing a new subsection in the result part of the manuscript where we have shown a comparison between our proposed work and other research works on some other optimization methods like PSO, GA, ACO, FPA in page 18, table 2. Also, the proposed work has been compared to a related work in table 3 page 19. Hope this correction satisfy the respected reviewer.
Author action: A new comparison section (page 16, section 3.5) is introduced within the result part of the manuscript to incorporate the important concern raised by the respected reviewer. Here the proposed work is compared with other work as well as other optimization techniques.
Reviewer 2 Report
The current research paper analyzes the possibility of a hybrid renewable microgrid in both off/on-grid scenarios. Techno-environmental-economic-power-system assessment is carried out using two platforms DIgSILENT PowerFactory and HOMER Pro. Applications are employed on a part of the Maldives microgrid. The following comments are requested to improve the overall paper quality:
1. The survey part is presented in a good way, add the main contribution points at the end of the introduction section.
2. Show correctly why the selected platforms are suggested for this work.
3. More description of the tested microgrid and the associated data is to be added as an appendix.
4. How the uncertainty is modeled for load, and renewable energies in your microgrid? Add some clarifications.
5. Figures quality can be improved. Extend the comments and concentrate on what you intend to show in each figure.
6. Summaries the techno-economical benefits of the studied scenarios.
7. Improve the conclusion section with the main findings and the future trend.
Author Response
Reviewer#2, Concern #: The current research paper analyzes the possibility of a hybrid renewable microgrid in both off/on-grid scenarios. Techno-environmental-economic-power-system assessment is carried out using two platforms DIgSILENT PowerFactory and HOMER Pro. Applications are employed on a part of the Maldives microgrid. The following comments are requested to improve the overall paper quality:
Author response: The authors would like to thank the respected reviewer for the valuable comments and time in reviewing the manuscript. The authors appreciate the valuable thinking and effort of the respected reviewer and have given highest priority to satisfy the issues raised by the honorable reviewer.
The authors have considered the comments of the respected reviewer with the highest priority and have corrected the manuscript accordingly. The authors do believe that the comments of the respected reviewer will definitely help enhancing the quality and acceptability of the manuscript.
Author action: N/A
Reviewer#2, Concern # 1: The survey part is presented in a good way, add the main contribution points at the end of the introduction section.
Author response: The authors thank the respected reviewer for the valuable comments and appreciations. The main contributions of this research work are now summarized in the last part of the introduction as bullet points for better visualization and understanding (Line no. 193-202).
Author action: The contribution of this research work is now summarized in the last part of introduction as bullet points (please see line 193-202).
Reviewer#2, Concern # 2: Show correctly why the selected platforms are suggested for this work.
Author response: The authors thank the respected reviewer for the concern. Because we want contribute the following points through this research work:
- Applies five dispatch strategy-based control in optimal modelling of a grid connected and isolated mode of hybrid microgrid system using HOMER Pro.
- The performances for grid tied and isolated modes based on five dispatch techniques have been compared to find the best control approach for both the modes. Also, the performance of the proposed design is compared to other optimization methods and other available works in this research domain.
- The microgrid model has been evaluated in both techno-economic-environmental perspective and the power system response (busvoltage, reactive power and frequency) perspective.
As we want to contribute the above mentioned works by the research work, the selected platforms are suggested for this work.
The reason for choosing HOMER based method rather than other mathematical approaches in finding the optimal solution is that HOMER has some superiority over the other methods. HOMER is a user-friendly environment offering faster convergence rate, uses deterministic algorithm and provides accurate results and it has less complexity. Other models cannot model the back up diesel generator and battery storage units and the stochastic nature of the renewables. DIgSILENT PowerFactory is also a well known software platform that can handle this type of simulation works. So, to find the power system responses in per unit, it has been chosen.
Author action: In the manuscript, lines 194-202, 207-214, 236-240 contains the related discussions.
Reviewer#2, Concern # 3: More description of the tested microgrid and the associated data is to be added as an appendix.
Author response: The authors would like to thank the respected reviewer for the valuable comment and wonderful suggestion. A more detailed description on the tested microgrid and associated data (like solar, wind profile, component details and technoeconomic parameters etc.) has now been supplied as appendix withing the manuscript. Hope the modifications satisfy the respected reviewer.
Author action: The detailed data is now provided as appendix in the manuscript. Please see page no 19-21.
Reviewer#2, Concern # 4: How the uncertainty is modeled for load, and renewable energies in your microgrid? Add some clarifications.
Author response: The authors would like to thank the respected reviewer for the valuable comments and suggestions.
The research approach explained in this research work can handle uncertainty issues like solar and wind resource variations. The other uncertain or sensitivity parameters like inflation etc. have not been considered in this present version of work to keep things limited to keep focus on the main contribution of this research work which is dispatch strategy-based analysis. The sensitivity analysis has been kept as future work. The approach as explained in the research methodology considers the uncertain characteristics of solar and wind profile and provides feasible solution considering the uncertainty.
The model is obviously sensitive to various sensitivity parameters like, costs of different components, yearly increment, initial investment, replacement costs, rate of rebate etc. The core concern of this very research work is to design the microgrid for it’s optimum operation offering least costs, environmental impact and component sizes. Besides that dispatch strategy based control is applied to further optimize the solution as dispatch strategy has overall impact on the systems sizing, costing and overall performances. Upon their mutual performances best and worst dispatch cases have been determined. As our main concern/ contribution of this work is not showing the impact of sensitivity analysis, the sensitivity analysis has been considered as a future work which is now mentioned in the future research idea section (last part of conclusion) of the manuscript.
Author action: According to the comment, now the manuscript contains the discussion in the manuscript in lines 324-331 and 535-537.
Reviewer#2, Concern # 5: Figures quality can be improved. Extend the comments and concentrate on what you intend to show in each figure.
Author response: The authors would like to thank the respected reviewer for the valuable comment.
The quality of the figures has been improved and more critical analysis of the results obtained are now added in the result/discussion part according to the suggestion. Hope the effort satisfies the respected reviewer.
Author action: The comment of the respected reviewer has been addressed by using high quality figures and more detailed analysis on the findings in the result section which can be found in the result and discussion part lines 401-416, 424-431, 447-461, 477-482.
Reviewer#2, Concern # 6: Summaries the techno-economical benefits of the studied scenarios.
Author response: The authors would like to thank the respected reviewer for the valuable comments and suggestions.
As suggested by the respected reviewer, the techno-economical benefits from the studied research work are now summarized in a more organized fashion in section 3 result and discussion, subsection 3.1 Techno-economic-environmental evaluation (Line no 383-387.). Hope the corrections satisfy the comment of the respected reviewer.
Author action: The techno-economical benefits of the studied scenarios have now been summarized in a more clarified manner.
Reviewer#2, Concern # 7: Improve the conclusion section with the main findings and the future trend.
Author response: The authors would like to thank the respected reviewer for the valuable comment and constructive suggestion. The authors have also found the importance of improving the conclusion section in a more organized way with the summary of the core findings and contribution of the research work along with a clear direction towards some future research improvements. Now, the conclusion is accordingly updated. Hope the correction satisfies the respected reviewer. Please see line no 536-542.
Author action: According to the comment of the respected reviewer, now, the conclusion section has been updated with main findings and direction towards future trends.
Reviewer 3 Report
The work treats the problem of the functioning of a reduced power microgrid. The choice of the best optimization method is the target of the work, under the conditions of available sources with specified powers. The graphs and Table 1 synthesize the tried variants, using dedicated software and taking in account the imposed operating conditions of the network.
I would reproach the memory size of the work, too large (nearly 82 MB; I don't know if the editor impose a limit size), due to included Figures. If you are considering resizing the Figures, the volume will be reduces consequently. And this is possible (with a little care) without affecting the graphic quality of images. Also, the Figures 6 ... 17 could be "shrinked" by presenting the variation of considered quantities only up to (for example) t = 2 seconds, because nothing interesting happens further. Also consider the elimination of the two blank pages at the end of paper.
I have no other observations on the content of the work, nor regarding the presentation mode.
Author Response
Reviewer#3, Concern # 1: The work treats the problem of the functioning of a reduced power microgrid. The choice of the best optimization method is the target of the work, under the conditions of available sources with specified powers. The graphs and Table 1 synthesize the tried variants, using dedicated software and taking in account the imposed operating conditions of the network.
Author response: The authors would like to thank the respected reviewer for the important comments and valuable suggestions. The authors are grateful to the respected reviewer for the precious time in reviewing this work. The authors have tried their best to consider and incorporate all the comments within the manuscript. The authors do believe that the incorporation of the valuable comments of the respected reviewer will definitely enhance the quality of the paper quality and possibility of acceptance of the work.
Author action: N/A
Reviewer#3, Concern # 2: I would reproach the memory size of the work, too large (nearly 82 MB; I don't know if the editor impose a limit size), due to included Figures. If you are considering resizing the Figures, the volume will be reduces consequently. And this is possible (with a little care) without affecting the graphic quality of images. Also, the Figures 6 ... 17 could be "shrinked" by presenting the variation of considered quantities only up to (for example) t = 2 seconds, because nothing interesting happens further.
Also consider the elimination of the two blank pages at the end of paper.
Author response: The authors would like to thank the respected reviewer for the valuable suggestion and important comment.
As the reviewer has commented about the shrinking of figures 6 to 17 by keeping t=2 rather than 5 seconds as after 2 seconds nothing interesting happens. But the authors believe that keeping the time upto 5 seconds is important because we are taking about stability in the steady state condition. In the opinion of the authors time upto 5 seconds is important in proving the steady state stability issue. Without changing the time frame, we managed to reduce the size after compressing the file. Hope still the manuscript is acceptable.
Now the pages have been removed from the manuscript. Line no
Author action: The issues raised by the respected reviewer have been incorporated throughout the manuscript.
Reviewer#3, Concern # 3: I have no other observations on the content of the work, nor regarding the presentation mode.
Author response: The authors would like to thank the respected reviewer for the valuable comments, appreciation and suggestions. All the comments have been tried to be incorporated within the manuscript. Hope the corrections satisfy the respected reviewer. Thanks to the reviewer for the precious time in reviewing the work.
Author action: N/A.
Round 2
Reviewer 1 Report
The authors have addressed my comments
Author Response
Reviewer#1, Concern #: The authors have addressed my comments
Author response: The authors would like to thank the respected reviewer for the valuable comments and time in reviewing the manuscript.
Author action: N/A
Reviewer 2 Report
No further comments.
Author Response
Reviewer#2, Concern #: No further comments.
Author response: The authors would like to thank the respected reviewer for the valuable comments and time in reviewing the manuscript. The authors appreciate the valuable thinking and effort of the respected reviewer.
Author action: N/A
