Synergy of Unidirectional and Bidirectional Smart Charging of Electric Vehicles for Frequency Containment Reserve Power Provision

Round 1

Reviewer 1 Report

This paper presents a study on the synergy of smart charging of electric vehicles for frequency containment reserve power provision in electrical power systems.

The results presented in the paper are very general with no details on the methodology used for implementation. The authors must add description of this methodology, with all necessary details.

Author Response

Thank you for the comment. You did not provide exact info, what you were missing, but we agree that the original version did not include enough information. Based on the comments of other reviewers, we added more decription of the methodology, in particular more context about FCR power and the used general simulation model.

Reviewer 2 Report

This paper aims to identify how the coordinated charging of electric vehicles (EVs) supports the power systems for Ancillary Services i.e., reserve power, and thereby simulate a model considering the stochastic behavior of the realistic data and technical constraints. The topic is interesting for researchers in the field of energy management, electric vehicles, power reserve, etc.

A detailed comment is as follows.

Comments:

 

1. The title is quite long and doesn’t fit well with the abstract. If possible, please simplify it according to the main contribution. 
2. The abstract is quite simple and it is hard to understand what is the problem, motivation, and methodology. Is it a simple simulation? With better to describe the model/methodology from the research significance point of view.
3. The introduction defines several opportunities, challenges, and uncertainties concerning Ev's load inductions, but all these are generally described. There are a lot of works of literature on these challenges/uncertainties that can help the readers to understand the problem more clearly. Please check https://doi.org/10.1016/j.jksuci.2022.04.019, https://doi.org/10.3390/en15041304
4. Methodology section 2.1 is quite difficult to understand the problem. Could you please explore a bit more for the sake of the reader’s understandability?
5. In the simulation model, the user’s behavior (arrival/departure/stay time, etc.) is generally mentioned, but what is the user’s behavior, and how does it influences the coordination of EVs? 
6. The authors presented a nice simulation model, though it needs to explain the information (what is the type of information e.g., control, data, etc.) and the power flow (Uni./bidirectional). 
7. Besides, the general model, the authors should provide the flowchart/pseudocode of the proposed algorithm.
8. It is difficult to understand the results (fig. 2), please explain. The simulation is for 5000 EVs, what are their battery capacity, their State-of-charge, stay time, energy requirement, charging power, etc.?
9. The same applies to the uni., and bidirectional (fig. 3). Please explain.
10. The authors claimed the support of power reserves through coordination of EV operations (Charge/discharge) but unfortunately, I can’t find how they proposed work to support the power reserve. Please explain.

Author Response

Thank you for your detailed comments. We tries to adress all points ad good as possible: 

1. We think the title fits the contribution well. We tried to think of a better title but could not come up with a shorter version that catches the essence. 
2. Thank you for this comment. we agree and we refined the abstract to clarify in particular the problem, motivation and methodology.  
3. Thank you for this comment. We revised the introduction and added a section about related work. Here, we also cited one of the given references.
4. Thank you for your comment. FCR power is a standard method to balance power grids. We assume the reader is familiar with the basic concepts. It is impossible to explain all technical details and different market mechanisms in the scope of this paper. This is also not part of our contribution. We do not want to change the way FCR generally works, we "just" analyse how the existing requirements can be fulfilled with alternative assets (in this case electric vehicles). Our simulation model mimics the existing functionality. We agree that we did not explain this well enough though. We added some more explanations and context about FCR power that hopefully make this clearer (Section 3.1), also for readers whe are not very familiar with FCR power. 
5. Thank you for you comment. We added a better explanation of this. In particular we explain how the user behavior results in constraints for the VPP operation. There is also a github link to the mobility model. The reader is encouraged to check the model if he is interested to learn how that works in depth. 
6. Thanks for this comment. The simulation model is not the main contribution here as we used an existing, complex model. We tried to improve the descriptions that are important to understand this paper and we provide many links and references for readers who want to dive deeper into the details of the model.
7. A flowchart or pseudo code of the whole model is unfortunately not possible in the scope of this paper as the model is very complex and consists of many components. The model itself is also not the contribution of this paper. The contribution here is the analysis of the case study and the sensitivity analysis we provide. In Fig. 1 we provide a general overview and we aimed to explain the general functionality in a transparent way. For more in depth info we also reference to Jonas Schlund's PhD thesis which includes a more in depth explanation of the overall model and its components. However, this is several hundreds of pages long.
8. Thank you for this comment. We agree with your comment. We added a better explanation of the graphs at the beginning of Sec. 3.2. This info was indeed missing and it was very hard to understand the graphs without the explanation. In general, the parameters you ask for derive from stochastic distributions of different official data sets in Germany, i.e., they represent the distributions of the current state in Germany. Those data sources are linked at the end of Sec. 3.1. The graphs then always keep the general parameter distribution and vary one particular parameter in each of the subgraphs. This way we can quantify the sensitivity of the results for certain parameters. 
9. Thank you for your comment. We also agree that the provided information was insufficient and added more explanations of how this works and what the graph means.
10. Thank you for your comment. We added some explanation on this as well. However, the "how" the reservation works is not the contribution of this paper. We use the methodology we previously published in https://doi.org/10.1145/3396851.3397697 for the reservation. This is referenced in Sec. 3.2 where we explain the simulation model.

 

 

Reviewer 3 Report

 

1. Keywords should include relevant words that capture the essence of your research, they need to be listed in an appropriate order of importance.

2. The motivations for conducting this study are not getting clear in the introduction.

 

3. More state-of-the-art literature review should be undertaken to cover various applications of the proposed approach.

 

4. The figures are not clearly presented. Poor qualities of figures, please enhance the resolution of all figures.

5. More discussion for simulation results.

 

6. The conclusions answer the aims of the study. The main results and future work of the proposed research should be included in the conclusion.

7. Add new references recently.

 

Author Response

Thank you for your detailed comments. We tried to address all points as good as possible:

1. Thank you for this comment. We changed the order of our keywords and add some new ones. 
2. Thanks, we agree on this comment. We revised the introduction refined the motivation. 
3. Thank you for this comment. We add a related work section after the introduction to discuss the state-of-the-art literature in the field of ancillary service provision with EVs as well as smart charging. 
4. All figures are super sharp and have 600 dpi (as required). Are you sure that this was not a displaying issue on your side?
5. Thank you for this comment. We agree and we refined the discussion also based on other reviewers comments. 
6. Thank you. We provide the main results in the conclusion. The future work is summarized in the last paragraph. 
7. Thank you for this comment. We updated the references with very recent references and added a whole related work section. 

Reviewer 4 Report

In this manuscript, the authors analysed the electric vehicles (EVs) for providing frequency containment reserve (FCR) power considering the German FCR market. The idea of the paper is good. However, current version of the paper requires a lot of improvement by addressing the following comments.

1. The literature review section of the paper is very weak. The authors should include some recent research articles related to the topic.

2. Please clearly explain the novelty of the paper considering the recent research articles.

3. Please mention the contributions considering the strategy proposed in the manuscript.

4.  Please explain the reason of using 15 minutes interval to provide full reserve power (Positive and Negative).

5. Please include flow chart of the strategy proposed in the manuscript.

6. The authors should explain the case study and results obtained in detail for better understanding of the reader.

7. The results for uni-directional and bi-directional Smart Charging must be explain in detail.

8. English language used in the paper requires a lot improvement.

Author Response

Thank you for your detailed comments. We tried to address all points as good as possible:

1. Thank you for this comment. We agree that tis was missing and add a related work section after the introduction to discuss the state-of-the-art literature in the field of ancillary service provision with EVs as well as smart charging. 
2. Thanks. In the end of the related work section we add our contribution. Additionally, we formulate our contribution also in the end of the introduction.
3. Thanks. We also refined the description of the contributions to consider this.
4. Thanks for this comment. This is a fixed market mechanism defined by the German TSOs. We made this clearer in the manuscript for readers who are unfamiliar with the market.
5. Thanks for this comment. Instead of a flow chart we added another formula to clarify the strategy and improved the explanation of Fig 3. Now it should be easy to understand. We thought about a flow chart but do not think that a flow chart is suitable to explain the strategy.
6. Thank you for this comment. We agree that this was not clear enough and we added more detail on both the methodology and the results discussion.
7. Thank you for this comment. We agree that this was not explained well enough. We added an in detail explanation.
8. The paper was cross checked by a native speaker.  

Round 2

Reviewer 1 Report

The authors have positively responded to all suggestions and recommendations provided by the reviewer.

Reviewer 2 Report

I appreciate the author's efforts in improving the quality of the manuscript. 

Reviewer 3 Report

No comments.

Reviewer 4 Report

The authors have satisfactorily addressed all the comments.