Optimal Power Flow Formulations for Coordinating Controllable Loads in Distribution Grids: An Overview of Constraint Handling and Hyper Parameter Tuning When Using Metaheuristic Solvers

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper gives a comprehensive review of optimal power flow (OPF) formulations. It investigates which constraint handling techniques are typically used when solving OPF problems using metaheuristics. It is also shown how the hyperparameters of these metaheuristics are tuned. A comprehensive literature review is carried out.

The contribution represents a review paper and does not contain original scientific research.

Furthermore, I have three general concerns:
1) The authors have conducted extensive comparisons in their literature review and performed an analysis based on the relevant criteria. However, the paper lacks a more in-depth synthesis. While the analysis is thorough, the synthesis is missing. Additionally, the authors should provide an assessment of the effectiveness of the methods used.

2) The title of the article suggests a review of controllable loads in low-voltage grids. However, do the majority of the reviewed articles examine low-voltage grids, or do they focus on medium to high-voltage grids?

3) It is not mentioned whether the reviewed articles assess symmetrical or asymmetrical grid systems.

Author Response

Please see attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article contains an overview of issues related to optimal power flow in the power grid. The authors presented the scope of optimization tasks, constraints and methods used to solve them.

• The title is too long – besides, the title of the article indicates OPF problems mainly in the low-voltage network. However, the authors presented a review of literature not only in the field of low-voltage networks. In my opinion, the title should correspond exactly to the content of the article, i.e. it could be more general.
• The structure of the manuscript is correct. In my opinion, the authors presented the structure of the article in a logical and coherent manner.
• The abstract also indicates the problems of low-voltage networks. As was written earlier, one must consider whether to generalize the subject of the article or indicate only those works that strictly concern low-voltage networks.
• In my opinion, the keywords are appropriately selected. The authors did not add the word "low-voltage network" but "electrical distribution grid", which indicates a generalization of the problems of the article.
• The reviewed article is a review article. Such articles are also necessary and valuable. However, they must contain an exhaustive review of the literature and not only a selected/partial one. The authors provide only the two most common databases: Scopus and IEEE. In my opinion, the authors should perform a more detailed literature review of both the indicated two databases and also search lesser-known databases.
• Generally speaking, the literature research is generally well-designed. As previously mentioned, the authors should clarify the following issues:
o It is necessary to decide whether the literature review concerns only low-voltage networks (as the title indicates) or is more general. The authors reviewed OPF tasks and methods that allow for their solution. Since the literature review also indicates works on networks other than low-voltage networks, it would be appropriate to divide the problem into different voltage levels of the network, but generalize it.
o The authors mention in the summary that almost all the articles found consider the problem at a single moment in time. This is not entirely true. There are problems in the literature that are also considered in specific time ranges/intervals.
o The authors state that a very small number of articles are based on real networks. In the literature, one can find more works in which real/existing networks are used. In addition, access to the real network is not always possible due to data confidentiality. Test networks, on the other hand, are also thought out from the point of view of practical application of the results.
o The authors conclude that metaheuristic methods should be subjected to statistical evaluation during the research. Each of these algorithms was previously subjected to such evaluation during which its authors proved its effectiveness. In addition, in practical issues, several algorithms can be used to solve a given problem and the best one can be selected. This shortens the calculation result. When solving real problems, the time to obtain the solution is very often an important factor. Sometimes the results must be available in real mode (online). Often, problems must be solved on an ongoing basis, so performing statistical analysis does not make sense.
o The literature review should also include works on energy storage.
• Generally speaking, when it comes to the editorial side of the article, the equations, figures and tables are correct. The authors could add a figure showing the frequency/histogram of the use of individual optimization algorithms. Although Table 1 provides methods, in my opinion a graph would show it better.
• Table 1 – in my opinion the table title is too long – the abbreviations that appear in the table title should be explained below the table as references.
• The presented conclusions are consistent with the assumptions of the article. Some should be more thought out after a more detailed review of the literature, which was written about earlier.

Author Response

Please see attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Thank you for responding to my comments.