Linear Voltage Stability Indicator (LVSI) for Optimal Placement of SVC Devices to Improve the Voltage Stability Margin in Transmission Systems
Round 1
Reviewer 1 Report
This study presents a procedure for the placement of SVC compensators in the EPS using the fuzzy c-Means clustering technique. I agree that the topic of this work is relevant and I judge it appropriate for the journal. The work is also quite organized and readable. I may notice that the authors may be unaware of recent works on cybersecurity of multi-area powers systems: Wide-area damping control resilience towards cyber-attacks: a dynamic loop approach. The relevance is related to the following point, the SVC compensators mentioned by the authors can (based on my understanding) be used also to monitor the status of the power system. In this sense, they can be used to detect abnormal operation due to faults or attack. Please check if it is appropriate to cite this. Concerning this manuscript, the methodology can be summarized as:
The OPF is initially quantified to obtain the sensitivity array of the system based on the Jacobian of the system. Then, the attenuation and electrical distance matrices are estimated. Subsequently, the fuzzy c-Means clustering algorithm is used with the initial estimated cluster identification criterion to obtain the voltage control areas (VCA).
The methodology seems solid and as I could follow the steps, it seems free of errors. But I would like to ask a few questions to check my understanding
- Based on my understanding, the modelling of the power system is based on static equations. This means that all the dynamics are neglected. Please explain under which assumptions it is reasonable to do so
- Related to the comment above, would there be any benefit in considering a dynamic model of the power system?
- Since part of the methodology essentially relies on an optimization problem, it could be appropriate to mention the computational complexity (i.e. the computational time) of the proposed optimization. How much time is needed to solve the problem for a 14-node and 30-node power system?
The technique described is applied to the 14-node and 30-node scheme to check its effectiveness. Also, the results obtained are compared with the Power Factory software and with similar studies. I judge the experiments very convincing, especially given the fact that authors also provide convincing comparisons. Therefore, I am will to support the work subject to the minor comments above.
Author Response
Comments and Suggestions for Authors
This study presents a procedure for the placement of SVC compensators in the EPS using the fuzzy c-Means clustering technique. I agree that the topic of this work is relevant and I judge it appropriate for the journal. The work is also quite organized and readable. I may notice that the authors may be unaware of recent works on cybersecurity of multi-area powers systems: Wide-area damping control resilience towards cyber-attacks: a dynamic loop approach. The relevance is related to the following point, the SVC compensators mentioned by the authors can (based on my understanding) be used also to monitor the status of the power system. In this sense, they can be used to detect abnormal operation due to faults or attack. Please check if it is appropriate to cite this. Concerning this manuscript, the methodology can be summarized as:
Response: We are very grateful for your comments and contribution to the work. This analysis was not really included because the objective of the study is based on the optimal compensation of reactive power for a system operation with high quality and efficiency. But, this would be a very interesting topic to analyze in future work dedicated to this study.
The OPF is initially quantified to obtain the sensitivity array of the system based on the Jacobian of the system. Then, the attenuation and electrical distance matrices are estimated. Subsequently, the fuzzy c-Means clustering algorithm is used with the initial estimated cluster identification criterion to obtain the voltage control areas (VCA).
Response: Thank you very much.
The methodology seems solid and as I could follow the steps, it seems free of errors. But I would like to ask a few questions to check my understanding
Response: Thank you very much.
- Based on my understanding, the modelling of the power system is based on static equations. This means that all the dynamics are neglected. Please explain under which assumptions it is reasonable to do so
Response: Thank you very much. We greatly appreciate this excellent observation. And yes, it's true. The dynamic analysis in the event of a fault or disturbance in the electrical network is a specific topic that should be dealt with in a different work. However, the dynamic response is offered by the SVC device and is validated by this use. In this case, the proposal is part of the optimal location and dimensioning of this SVC device to improve the operation of the system, raising quality and efficiency.
- Related to the comment above, would there be any benefit in considering a dynamic model of the power system?
Response: Thank you very much. It would be interesting to carry out this study, but it could be very large and would be more associated with the individual response of the SVC, perhaps under disturbed conditions. However, this work focuses on the optimal planning of the electrical system operation, and its objective is to find the optimal location and dimension of the SVC for the best compensation of reactive power.
- Since part of the methodology essentially relies on an optimization problem, it could be appropriate to mention the computational complexity (i.e. the computational time) of the proposed optimization. How much time is needed to solve the problem for a 14-node and 30-node power system?
Response: Thank you very much. We have included in the paper the computing time used to find the solutions.
The technique described is applied to the 14-node and 30-node scheme to check its effectiveness. Also, the results obtained are compared with the Power Factory software and with similar studies. I judge the experiments very convincing, especially given the fact that authors also provide convincing comparisons. Therefore, I am will to support the work subject to the minor comments above.
Response: Thank you very much.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Review of the paper " THE LINEAR VOLTAGE STABILITY INDICATOR (LVSI) FOR OPTIMAL PLACEMENT OF SVC DEVICES TO IMPROVE THE VOLTAGE STABILITY MARGIN IN TRANSMISSION SYSTEMS"
This paper presents a procedure for deploying SVC compensators in EPS using the fuzzy c-Means clustering technique. The described technique is applied to a 14-node and a 30-node scheme to test its effectiveness. Furthermore, the results obtained are compared with the Power Factory software and with similar studies.
The work addresses a very important and topical issue. The current dynamic development in the use of RES is unfortunately causing problems in the electrical grid. I agree with the authors of the paper that proper voltage regulation and reactive power compensation are required to regulate the system voltage and reduce active power losses. Reactive power control leads to improved performance of AC power systems. Therefore, in order to maximise the overall system performance and ensure an appropriate investment in FACTS devices, it is necessary to determine the optimal position and size of these devices. The study uses objective functions to seek to reduce generation costs, energy losses and voltage deviation in the power grid. I rate the research idea very highly. The methodology of the work is also developed very well. On the other hand, I believe that other parts of the work need to be corrected.
1) I propose to present the advantages and disadvantages of known methods for the deployment of FACTS devices. Please indicate what scientific problem is to be solved. The characteristics of the known methods will be helpful to evaluate the authors' proposed solution. From the literature review performed, there is no need to realise new research. Please indicate clearly what is the reason for carrying out new research.
2) From Figure 1, does it appear that an increase in EPS capacity results in lower investment costs regardless of power?
3) Figure 2 - in the wrong place the description of the figure.
4) The paper is very comprehensive but lacks specific information. Table 1 and 2 I suggest replacing with text.
5) Incorrect numbering of tables.
6) figure 5 and 6 - What are the differences in the voltage profiles for SVC - 1, 3 and 6? If there are differences in profiles it is better to show them all in one drawing. Profiles for a given size in one figure. Such a presentation will make it easier to show the differences. Please expand on the interpretation of the profiles. Stating that something increases or decreases is too simplistic. Please avoid statements such as: much, little, etc. throughout your work. Please give specific values or ranges of values.
7) Incorrect references in the text to figure numbers.
8) Why were only diagrams analysed for which LVSI suggests that ESP is far from voltage collapse?
9) Comments for the 30-node diagram analogous to those for the 14-node diagram.
10) Table 1 and 3 - What is the LVSI voltage stability index for individual VCAs? Perhaps a brief characterisation of the clusters?
11) What is apparent from table 5? It can be replaced by one sentence.
12) Conclusions need to be revised. Currently it is a description of the work carried out.
13) 6, 7, 32 literature item misspelled.
14) Literature item number 40 is also under number 46.
The idea of the work is very interesting. In my opinion the work should be shortened. It needs to contain more concrete research results. It needs an editorial correction. There are many errors.
Author Response
Comments and Suggestions for Authors
Review of the paper " THE LINEAR VOLTAGE STABILITY INDICATOR (LVSI) FOR OPTIMAL PLACEMENT OF SVC DEVICES TO IMPROVE THE VOLTAGE STABILITY MARGIN IN TRANSMISSION SYSTEMS"
This paper presents a procedure for deploying SVC compensators in EPS using the fuzzy c-Means clustering technique. The described technique is applied to a 14-node and a 30-node scheme to test its effectiveness. Furthermore, the results obtained are compared with the Power Factory software and with similar studies.
The work addresses a very important and topical issue. The current dynamic development in the use of RES is unfortunately causing problems in the electrical grid. I agree with the authors of the paper that proper voltage regulation and reactive power compensation are required to regulate the system voltage and reduce active power losses. Reactive power control leads to improved performance of AC power systems. Therefore, in order to maximise the overall system performance and ensure an appropriate investment in FACTS devices, it is necessary to determine the optimal position and size of these devices. The study uses objective functions to seek to reduce generation costs, energy losses and voltage deviation in the power grid. I rate the research idea very highly. The methodology of the work is also developed very well. On the other hand, I believe that other parts of the work need to be corrected.
Response: Thank you very much for your comments and contribution to this research.
1) I propose to present the advantages and disadvantages of known methods for the deployment of FACTS devices. Please indicate what scientific problem is to be solved. The characteristics of the known methods will be helpful to evaluate the authors' proposed solution. From the literature review performed, there is no need to realise new research. Please indicate clearly what is the reason for carrying out new research.
Response: Thank you very much for your comment. The requested bibliographic analysis is included.
2) From Figure 1, does it appear that an increase in EPS capacity results in lower investment costs regardless of power?
Response: Thank you very much for your comment. As it is a quadratic function, it can be observed that the lowest installation costs occur in capacities close to 500 Mvar. There is an increase in the installation price of the SVC device for capacities lower or higher than this value. This was better explained in the text.
3) Figure 2 - in the wrong place the description of the figure.
Response: Fixed text scrolling. Thank you very much for your observation.
4) The paper is very comprehensive but lacks specific information. Table 1 and 2 I suggest replacing with text.
Response: Fixed. Thank you very much for your observation.
5) Incorrect numbering of tables.
Response: Fixed. Thank you very much for your observation.
6) figure 5 and 6 - What are the differences in the voltage profiles for SVC - 1, 3 and 6? If there are differences in profiles it is better to show them all in one drawing. Profiles for a given size in one figure. Such a presentation will make it easier to show the differences. Please expand on the interpretation of the profiles. Stating that something increases or decreases is too simplistic. Please avoid statements such as: much, little, etc. throughout your work. Please give specific values or ranges of values.
Response: Thank you very much for your observation. The figures show similar behaviors, but they are different since each one represents different case studies.
7) Incorrect references in the text to figure numbers.
Response: Fixed. Thank you very much for your observation.
8) Why were only diagrams analysed for which LVSI suggests that ESP is far from voltage collapse?
Response: Thank you very much for your observation. Actually, only those outside of the voltage collapse were not analyzed. But this restriction was guaranteed.
9) Comments for the 30-node diagram analogous to those for the 14-node diagram.
Response: Thank you very much for your observation. OK
10) Table 1 and 3 - What is the LVSI voltage stability index for individual VCAs? Perhaps a brief characterisation of the clusters?
Response: Thank you very much for your observation. A brief characterization of the clusters was included.
11) What is apparent from table 5? It can be replaced by one sentence.
Response: Thank you very much for your observation. OK, table 5 was removed.
12) Conclusions need to be revised. Currently it is a description of the work carried out.
Response: Thank you very much for your observation. According to the observation, the most descriptive information was eliminated, highlighting the achievements of the research and the fulfillment of its objectives.
13) 6, 7, 32 literature item misspelled.
Response: Fixed. Thank you very much for your observation.
14) Literature item number 40 is also under number 46.
Response: Fixed. Thank you very much for your observation.
The idea of the work is very interesting. In my opinion the work should be shortened. It needs to contain more concrete research results. It needs an editorial correction. There are many errors.
Response: Fixed. Thank you very much for your observation.
Author Response File: Author Response.pdf
Reviewer 3 Report
The authors present the optimal placement of SVC devices in electric power systems considering a linear voltage stability indicator. Although the paper discusses an interesting topic, my main concern lies in the scientific contribution of the document. There are also some issues regarding presentation and English writing that are not minor and must be corrected.
1- There seem to be some problems with the title. On one hand, it should not be in capital letters, on the other hand, the authors must check the correct use of the definite article “the”.
2- The contribution of the paper is not clear. Several papers in the scientific literature approach the optimal allocation of FACTS devices in electric power systems. The problem and the solution method do not seem to present something new. Please clarify and explain.
3- The literature review must be complemented either with a timeline or a table that briefly indicates the main aspects of other research works and the difference from the one proposed by the authors.
4- In the abstract, the authors use several acronyms that are not defined. Please define each acronym the first time it is used in the document.
5- The first line of the abstract says “SVC compensators” but SVC already include the word “compensator” in its definition. Please check and correct.
6- Sometimes the authors use “c-means” and sometimes “c-Means” (with capital M). Please keep uniformity in the use of capital letters.
7- In line 18 what do the authors mean by “created” SVC? I guess the word “created” is misused in this sentence. The same applies to the sentence in lines 20-21 when the authors mention the “creation” of CVAs. Please check.
8- Please check the technical accuracy of the sentence in lines 31-32. Are these sources of reactive power?
9- The legend of figure 2 is misplaced.
1- Please improve the quality of Figures 2 and 3.
1- The right expression is “IEEE 30-bus test system” not “IEEE 30-node test scheme”
1- The discussion of results is laconic and must be substantially improved.
1- The first paragraph of the conclusions is not a conclusion but a description of the paper.
1- I encourage the authors to hire a professional service to improve the English style and grammar of the document.
1- A list of acronyms is needed at the end of the document.
Author Response
Comments and Suggestions for Authors
The authors present the optimal placement of SVC devices in electric power systems considering a linear voltage stability indicator. Although the paper discusses an interesting topic, my main concern lies in the scientific contribution of the document. There are also some issues regarding presentation and English writing that are not minor and must be corrected.
Response: Thank you very much for your comments and contribution to this research. The work addresses a significant and topical issue. Unfortunately, the current dynamic development in the use of RES is causing problems in the electrical grid. Proper voltage regulation and reactive power compensation are required to regulate system voltage and reduce active power losses. Reactive power control improves the performance of AC power systems. Therefore, to maximize overall system performance and ensure proper investment in FACTS devices, it is necessary to determine the optimal position and size of these devices. The study uses multiple objective functions to seek to reduce generation costs, energy losses, and voltage deviation in the electrical network, this multiple analysis being an important contribution to knowledge in addition to the proposed technique that was also validated. We value the idea of the investigation very positively. The work methodology is novel. However, the work has been corrected for a better understanding.
- There seem to be some problems with the title. On one hand, it should not be in capital letters, on the other hand, the authors must check the correct use of the definite article “the”.
Response: Fixed. Thank you very much for your observation.
- The contribution of the paper is not clear. Several papers in the scientific literature approach the optimal allocation of FACTS devices in electric power systems. The problem and the solution method do not seem to present something new. Please clarify and explain.
Response: The proposal is novel and has a clear contribution in the number of variables analyzed in the problem and the use of the proposed methodology. This was expanded upon in the text. Thank you very much for your observation.
- The literature review must be complemented either with a timeline or a table that briefly indicates the main aspects of other research works and the difference from the one proposed by the authors.
Response: This analysis was carried out in Table 5. However, another reviewer (Reviewer 2) suggested that this table not be included and that the analysis only be described and this change was already made appropriately.. Thank you very much for your observation.
- In the abstract, the authors use several acronyms that are not defined. Please define each acronym the first time it is used in the document.
Response: Thank you very much, it's true. The abstract has been corrected according to your suggestion. Thank you very much for your observation.
- The first line of the abstract says “SVC compensators” but SVC already include the word “compensator” in its definition. Please check and correct.
Response: Fixed. Thank you very much for your observation.
- Sometimes the authors use “c-means” and sometimes “c-Means” (with capital M). Please keep uniformity in the use of capital letters.
Response: Fixed. Thank you very much for your observation.
- In line 18 what do the authors mean by “created” SVC? I guess the word “created” is misused in this sentence. The same applies to the sentence in lines 20-21 when the authors mention the “creation” of CVAs. Please check.
Response: You are absolutely right. It was a typing error because it is not about SVC created, but about VCA created, this was duly corrected. Thank you very much. In this case, the term create is used in the reviewed bibliographical references. It is about creating the areas (clusters) or defining the areas. Thank you very much for your observation.
- Please check the technical accuracy of the sentence in lines 31-32. Are these sources of reactive power?
Response: The sentence was corrected. Thank you very much for your observation.
- The legend of figure 2 is misplaced.
Response: Fixed. Thank you very much for your observation.
- Please improve the quality of Figures 2 and 3.
Response: Fixed. Thank you very much for your observation.
- The right expression is “IEEE 30-bus test system” not “IEEE 30-node test scheme”
Response: The change was made throughout the document for both the IEEE 30-bus test system and the IEEE 14-bus test system. Thank you very much for your observation.
- The discussion of results is laconic and must be substantially improved.
Response: In agreement. Comments on the results obtained were extended. Thank you very much for your observation.
- The first paragraph of the conclusions is not a conclusion but a description of the paper.
Response: Thank you very much for your observation. According to the observation, the most descriptive information was eliminated, highlighting the achievements of the research and the fulfillment of its objectives.
- I encourage the authors to hire a professional service to improve the English style and grammar of the document.
Response: Thank you very much for your observation. The entire document has been revised and rewritten by a native speaker. In addition, the GRAMMARLY tool was paid to receive advanced writing corrections.
1- A list of acronyms is needed at the end of the document.
Response: A list of acronyms was included at the end of the document.. Thank you very much for your observation.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Good morning ,
Job Notes:
1. The list of acronyms is much larger. Is the presentation at the end of the work a good place?
Accepts your corrections. However, I still think that the justification for taking up the topic could be better. The research done allows you to draw more valuable conclusions.
Reviewer 3 Report
The authors attended to all suggestions.
I have no further comments
