PONE-D-24-35622A load conservation valley-filling heuristic for electric vehicle power charging allocation: algorithms and scenariosPLOS ONE

Dear Dr. Souza,

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PLOS ONE

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Additional Editor Comments:

A well written interesting article which requires greater structure, a broader discussion of the literature in both a tabulated as well as written format as suggested by reviewers and clarification of the methodology.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Partly

Reviewer #4: Yes

Reviewer #5: No

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: Yes

Reviewer #4: Yes

Reviewer #5: No

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3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

Reviewer #5: No

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: No

Reviewer #4: No

Reviewer #5: No

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Strengths:

1. Novel Contribution: The introduction of the Load Conservation Valley-Filling (LCVF) heuristic significantly advances electric vehicle load management.

2. Comprehensive Analysis: Strong analysis showing LCVF’s effectiveness in reducing peak charge and energy consumption across various scenarios.

3. Clear Presentation: Results are well-structured with effective tables and figures.

4. Relevance: The research is timely and relevant to the growing need for efficient energy management in smart grids.

5. Future Work: Suggestions for future research are valuable and well-articulated.

Weaknesses:

1. Statistical Analysis: More detail on statistical methods (e.g., ANOVA) is needed, including assumptions and implications.

2. Limitations Discussion: A more comprehensive discussion of LCVF's limitations, especially regarding computational complexity, is necessary.

3. Contextualization of Results: A deeper comparison with existing literature would enhance the significance of the findings.

4. Clarity and Conciseness: Some sections could be streamlined for readability and to reduce redundancy.

5. Figures and Tables: Better integration of figures and tables into the narrative would improve coherence.

Recommendations for Improvement:

1. Enhance the clarity of statistical analysis.

2. Expand on LCVF's limitations.

3. Provide a thorough literature comparison.

4. Streamline text for clarity.

5. Improve integration of figures and tables.

Reviewer #2: The manuscript presents a method for optimizing electric vehicle (EV) charging in order to reduce grid demand across many scenarios, showing notable reductions in energy consumption, improving grid stability and efficiency.

I have the following concerns about it:

1- The introduction needs to be revisited. It is lacks direction with a clear research gap.

2- The novelty of the work must be clearly addressed and discussed, compare your research with existing research findings and highlight novelty, (compare your work with existing research findings and highlight novelty).

3- There are so many works in the existing field, author should mention all new work.

4- It is recommended that the simulation results be expanded and more comparisons with state-of-the-art methods be conducted to validate the effectiveness of the proposed approach.

5- More updated references from year 2023 and 2024 can be included for literature review. Additionally, in the area of smart grid managment, You may find the following reference helpful to be added to the references list: Smart vehicle-to-grid integration strategy for enhancing distribution system performance and electric vehicle profitability, Energy, Volume 302, 2024, 131807.

Reviewer #3: Comment 1: There are several grammatical mistakes. Please work close to a native English speaker to refine the language of this manuscript.

Comment 2: The literature review section should be improved. It should be dedicated to present critical analysis of state-of-the-art related work to justify the objective of the study. Also, critical comments should be made on the results of the cited works.

Comment 3: Please carefully check recent literature and discuss/cite as you see fit and update your reference list.

Comment 4: The findings were not comprehensively discussed. It seems that the paper is a report instead of a scientific paper.

Comment 5: It would be excellent if the importance of this issue was validated by detailed research and thoroughly documented data.

Comment 6: The introduction section should be enriched by adding the following related

Reviewer #4: Comments

Title:

•Clarify the focus: specify that the heuristic is aimed at improving energy efficiency or grid management in the title for

clearer emphasis on the objective.

•Consider streamlining the title for better readability while maintaining clarity.

•Ensure the title appeals to both energy management and electric vehicle researchers by highlighting practical implications like power grid optimization.

Abstract:

•Clarify the novelty by explaining more clearly what makes LCVF heuristic innovative as compared to previous approaches like CVF and OVF.

•Consider simplifying some of the numerical results or presenting them in a more accessible way to ensure the abstract remains concise and easy to follow for a broad audience.

•Include a sentence on how these findings could be applied in real-world EV charging infrastructure or energy management systems.

•Strengthen the link between the DSM strategies and their practical implications for energy grids, offering clearer insights into how DSM contributes to the sustainability of electric grids.

Introduction:

•The introduction does a good job of outlining the challenges faced by electricity grids due to EV adoption, but it could be more concise in framing the core problem to focus the reader’s attention.

•Terms like "DSM techniques" and "Valley-Filling" are introduced well, but the explanation could be made more accessible to non-experts. Brief definitions for key terms could help general readers.

•There is some repetition, particularly around explaining the challenges of grid stress and DSM strategies. Condensing these parts could make the introduction more engaging.

•The introduction of the Load Conservation Valley-Filling (LCVF) heuristic is delayed until later in the paragraph. Consider mentioning it earlier to highlight the novelty and contribution of the research.

•The technical details (like "Peak charge (Pc)" and "load time-slots (TS)") could be briefly explained or simplified to improve clarity and accessibility.

•The English and grammar are mostly clear but could be improved for smoother flow:

Example: Instead of "in contexts where the grid operator could look at the previous patterns of EV power consumption," use "in scenarios where grid operators can analyze previous EV consumption patterns."

•Some sentences could be shortened to avoid overloading readers with complex ideas in one go.

•You can strengthen the section by discussing the broader impact of adopting LCVF, such as cost savings, energy efficiency, and real-world applicability, earlier in the introduction.

Related work section/Literature Review

•To further improve the literature review, it is essential to include a comparison table that summarizes the key findings, methodologies, and limitations of previous studies. This table will provide a clear visual reference for readers to quickly understand how the proposed approach compares to existing solutions and also mention how your studies overcome those limitations

•The literature review effectively covers various DSM techniques, but it can be better organized. Consider grouping studies more clearly by themes (e.g., EV aggregators, V2G technologies, forecasting algorithms) to enhance readability.

•There is some redundancy when describing similar techniques across different studies. Streamlining these descriptions would help reduce repetition and focus on the key contributions of each work.

•More emphasis should be placed on explaining how each referenced study specifically relates to the presented research. For instance, directly linking how previous methods fall short and how the proposed LCVF heuristic addresses those gaps would strengthen the argument.

•While the section does well in presenting technical details, Try to simplify technical jargons, some complex terms (e.g., "EVRPTW," "SoC," and "load factor") could benefit from brief explanations or simplification for readers unfamiliar with those terms.

•Transitions between studies could be smoother. Some paragraphs feel disconnected; adding linking sentences between studies could enhance the narrative flow.

•The novelty of the proposed heuristic is introduced only at the end. Consider briefly introducing the research gap and how the new approach fills it earlier in the section to keep readers engaged.

•Some studies are explained in much more detail than others. Consider providing consistent levels of detail across all referenced works or focusing more on studies that are most relevant to the proposed research.

•The English grammar is generally good, but a few sentences are overly complex. For example, “...resulted in better initial solutions and avoiding drops in local optima” could be rephrased as “...resulted in better initial solutions while avoiding local optima.” Simplifying sentence structures would improve clarity.

Methodology/ Material and Methods:

•The "Methodology" section is missing, which should clearly explain the proposed design of the new heuristic, named Load Conservation Valley-Filling (LCVF), and its detailed implications. The absence of this section makes it difficult for readers to develop a general understanding of the concept and its application.

•A flowchart or block diagram outlining the general framework of the proposed methodology is missing.

General Comments

•Consider defining key terms more clearly when they are first introduced (e.g., "valley," "peak charge," "capacity margin index") to ensure the reader fully understands their significance.

•Ensure all referenced figures (e.g., Fig. ??) are clearly labeled and include descriptive captions that summarize their relevance to the text. This will aid in comprehension.

•Provide a brief justification for why the chosen time slice (e.g., 10-minute intervals) is optimal for the VF approach in the context of electric vehicles.

•Be generous in citing the work of others. It makes the work more reliable. I have noticed at most of the places the references are missing.

Specific Comments on Algorithms

•Clarify how the parameters (e.g., upperPc, lowerPc) are initialized and adjusted in both the CVF and OVF algorithms. A flowchart or diagram illustrating the decision-making process could enhance understanding.

•Include a more detailed comparative analysis between CVF and OVF, highlighting their performance metrics (e.g., convergence speed, efficiency) based on real-world scenarios or simulations.

•When discussing the oscillatory behavior in CVF, provide quantitative data or examples to illustrate its impact on grid stability. This will underscore the importance of the OVF approach.

Comments on Load Conservation Valley-Filling (LCVF)

• Elaborate on the "state storage" concept in the LCVF algorithm. Discuss how this improves efficiency and stability compared to CVF. Providing a visual representation of how data is stored across iterations could be beneficial.

•Sensitivity Analysis: Consider incorporating a sensitivity analysis to show how variations in parameters (e.g., Pc) impact the performance of LCVF compared to CVF and OVF.

Future Directions

•Discuss potential challenges in implementing these heuristics in real-world scenarios, such as computational limits, user behavior, or grid characteristics.

•Suggest other potential applications for the VF approach beyond electric vehicles, which could demonstrate the versatility and broader relevance of your research.

Formatting

•Ensure consistent notation throughout the document, particularly for variables and parameters, to avoid confusion.

Result and discussion

•The description of the scenarios could benefit from clearer transitions between them. Consider adding a brief introduction or summary for each scenario to avoid confusion and provide a clearer flow of information.

•Cite the link of experiments and evaluation result dataset as reference

Interpretation of Results:

•While the section explains the results in terms of performance, the interpretation of why certain heuristics performed better in specific scenarios is somewhat lacking. More discussion on the reasons behind the behaviors of the CVF, OVF, and LCVF algorithms in each scenario would provide a deeper understanding.

Runtime Explanation:

•The runtime differences between the heuristics are mentioned but could use further elaboration. How does the nature of the problem complexity or dataset size contribute to the differences in runtime across scenarios?

•It might also help to quantify the runtime differences more specifically rather than just qualitatively ("1/2 the time," "1/3 the runtime"). Consider adding a table to summarize the exact times and Pc values for clearer comparison.

Visuals and Graphs:

•The discussion frequently references figures, but the figures are marked as "Fig. ??", which disrupts the flow and makes it difficult to visualize results. Correct the figure numbers and ensure they are referenced consistently.

•It would be helpful to include a discussion of how each graph supports the conclusions. For example, explicitly mention key features or patterns observed in the graphs to reinforce the written analysis.

Deeper Comparative Analysis:

•While the LCVF heuristic is often presented as the superior method, the specific trade-offs between LCVF and the other heuristics are not fully explored. Expanding on where CVF and OVF might still offer advantages (e.g., under different conditions or dataset types) would add depth to the analysis.

•The discussion on the convergence rate and resource allocation could benefit from more numerical comparisons (e.g., percentage reductions in Pc for LCVF versus CVF and OVF).

Broader Implications:

•The broader implications of the findings are not fully addressed. It would enhance the section to briefly discuss how the findings might apply to real-world EV charging systems or suggest future research directions based on the observed outcomes.

Algorithm Specifics:

•It would be valuable to include more details about the LCVF algorithm's operations, especially its ability to "conserve load" more efficiently. For readers unfamiliar with the specific techniques, a short explanation of how each algorithm allocates load in practice would enhance comprehension.

Convergence Criteria:

•The criteria for determining convergence (1% difference between iterations) are mentioned but not justified. Why was this threshold chosen, and how does it affect performance across the heuristics? A brief explanation would help clarify its importance.

Statistical Analysis

•The explanation of hypothesis testing could be streamlined. Instead of re-explaining the concept of the null hypothesis (H0) for each test, it would be beneficial to summarize these tests more concisely. This would improve readability.

•While non-parametric tests were appropriately selected for non-normally distributed data, a brief explanation of why this occurred in certain scenarios (e.g., due to skewed EV load data) could add depth to the analysis

• I found boxplots and other plots at the end but not clarified in the analysis.

•The impact of outliers should be discussed further.

•Expand the analysis to provide more practical insights into the results, particularly for practitioners who may need to decide between these heuristics based on real-world scenarios.

•While there are statistically significant differences in certain scenarios, the practical relevance of small differences, such as those observed in the flexible and increased consumption scenarios, could be further discussed to guide decision-making.

Conclusion

•While the conclusion highlights LCVF's advantages, it could benefit from a clearer explanation of the specific novel aspects that distinguish LCVF from existing methods like CVF and OVF.

•The discussion of LCVF's computational complexity and limitations is somewhat brief. Expanding on these limitations and suggesting mitigation strategies would provide a more balanced view.

•Although quantitative reductions in peak charge and energy consumption are noted, providing more context about the practical impact (e.g., cost savings, grid stability) would enhance the conclusion.

•The proposed future directions are promising, but they could be more specific. For instance, elaborating on which machine learning techniques or real-time optimization methods could be integrated would strengthen the conclusion.

Some minor points

•The list of references should be carefully checked to ensure consistency between all references and their compliance with the journal policy on referencing.

•The professional English editing is recommended. The authors should get editing help from someone with full professional proficiency in English.

•The text should be justified to aligned properly throughout the article

•The plots are presented at the end of paper are appear inappropriate at the end, it should be present at their respective position to relate those pots more concisely with your research work.

•The dataset heading is currently missing and should provide detailed information about the dataset, including its characteristics, size, and the methodology used for its utilization in the study

•Referred figure number at various position are missing which disturb the flow of article

•Include more recent references. At some places I found the references are missing

Reviewer #5: The manuscript lacks significant novelty, as the results presented do not offer new insights or advancements compared to existing literature. The study seems to replicate previous work without addressing a unique angl

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Reviewer #1: Yes: Waqar Ahmad

Reviewer #2: No

Reviewer #3: No

Reviewer #4: No

Reviewer #5: No

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Optimizing power grids: a valley-filling heuristic for energy-efficient electric vehicle charging

PONE-D-24-35622R1

Dear Dr. Souza,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Kind regards,

Barry Kweh

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

The authors have clarified their methodology, provided a tabulated literature review and also improved the overall grammatical structure of their manuscript.

Reviewers' comments: