A Comprehensive Review on Power-Quality Issues, Optimization Techniques, and Control Strategies of Microgrid Based on Renewable Energy Sources

Round 1

Reviewer 1 Report

1. In Figure 15. the authors have described "the consensus-based control" and the "multiagent system-based control" as two different control schmes. This doesn't seem correct to me. Please, reconsider to me.

2. The droop control (primary control) has not been presented well. It would be better to give the mathematical background of the conventional droop control in the revised manuscript. For example have a look at the following articles: https://doi.org/10.1109/TPEL.2012.2199334 https://doi.org/10.1109/ACCESS.2022.3183635, https://doi.org/10.3390/en14102936

2. In Figures 9 and 15. the authors have described "the consensus-based control" and the "multiagent system-based control" as two different control schmes. This doesn't seem correct to me. Please, reconsider this aspect.

3. In Figure 9, the authors have considered the types of centralized secondary control as (i) multiagent-based control, and (ii) consensus-based control. This is NOT CORRECT.

4. In Table 13, among the three disadvantages of the Distributed Control, two are decribed as "Insufficient coordination between DGUs., High investment in communication". 

However, in case of distributed control, there is a sparse communication network. So, in my view, the communication cost is not high as compared to the centralized control. Furthermore, the distributed control is a consensus-based or agent-based contro. Hence, there is a sufficient coordination among DGs.

5. I cannot see a single equation in the manuscript. This is astonishing from the point of view of a review article. It would be better to include sufficent mathematical background regarding primary, secondary and tertiary control layers. For example, have have a look at the following articles: https://doi.org/10.1109/ACCESS.2020.3048723, https://doi.org/10.3390/en14248408

Author Response

1. We really appreciate you notifying us. We have revised the document again to correct the Figure 9 and 15 and thus comply with your suggestion.
2. We appreciate the suggestion, dear reviewer. We have revised the document and complemented the information about droop-control in section 5.4.1.1 and we have also added the corresponding mathematical formulation to improve the content of the document. It is worth mentioning that we have used the references that you kindly shared with us to “Mathematical Modeling of Micro-Generation Sources".
3. We appreciate your correction on this topic.
   
   Evidently, the consensus–based secondary frequency control is provided for islanded microgrids under weak communication conditions. For which, efforts have been made to reduce the effects of weak communication conditions, proposing new approaches with time-varying control gain is proposed [60] and so distribute power and voltage restoration in island mode. Therefore, following your suggestion, we have replaced
   2 of the disadvantages of distributed control listed in Table 13, as follows.
   
   (Before) Insufficient coordination between DGUs.
   (After) Unsuitable for long transmission lines, security
   
   (Before) High investment in communication infrastructure
   (After) Weak communication

 

4.  Again, we appreciate your comments regarding the mathematical formulation of our manuscript. We have included mathematical background regarding primary, secondary and tertiary control layers relying on the references that he shared with us. In sections 5.4.1., 5.4.2., and 5.4.3.,
the changes will be noted.

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Despite the fact that a lot of efforts have been done by the authors and a comprehensive bibliography has been prepared with almost 340 references, I believe that the manuscript is more similar to book chapters rather than scientific journal papers. Review papers should have critical point of view and focus on the gaps. I think this manuscript is more focusing on mentioning the problems, issues and the strategies applied for solving them and could not properly reflect the analyses and comparison between the strategies and find the gaps for future researches.More critical discussions are needed and more organised sections should be provided.

Author Response

1. Dear reviewer. We agree with your comments. In response to your suggestion, we have added in section 6 entitled "Discussion with recently conducted reviews" critical comments on the studies being analyzed, making clear the contribution of our study compared to the others in terms of HMGs.

We thank you and we really appreciate your comments that help us improve the quality and understanding of our manuscript.

Author Response File: Author Response.pdf

Reviewer 3 Report

This paper offers a comprehensive review on power quality issues, optimization techniques and control strategies of microgrid based on renewable energy sources. After careful review, there are still some minor comments for improving the paper as follows.

1.       The uniqueness of this review is that it considers the challenges related to power quality. However, other reviews have been presented the problems of power quality. What is the difference between this review and other reviews in terms of power quality?

2.       In Table 8, the author should depict the application of the optimization techniques in detail to provide better understanding for readers.

3.       In Section 4.2, it is better to analyze some optimization algorithms proposed in recent years rather than PSO.

4.       Figure 9 shows control strategies most used in HMGs. The author should introduce a table to depict the advantages and disadvantages of control strategies to provide a suitable visualization form for illustration.

Author Response

1. There has been a lot of effort in the implementation of optimization techniques and control strategies as well as in the design of devices to improve the power quality in conventional EPS, but due to the changes in the nature of the loads, the new challenges that modern devices bring to EPS, increasing customer awareness and cost of power quality improvement devices, there should be a comprehensive review of current power quality aspects of future electrical systems smart as HMGs. This would include the implementation of new tools and methods that address these needs, considering the new challenges and the deployment of new DGUs.

These power quality challenges and issues cited in this paper include component harmonics, voltage unbalance, flicker, over/under voltage, sags and swells, etc. For example, we have concluded that harmonic distortions are one of the main challenges that need to be resolved before HMGs become commonplace. Non-linear loads and the high penetration level of intermittent RES are the main cause of harmonic distortions in HMGs. Therefore, it is necessary for HMGs to propose improved harmonic compensators to avoid a threat to the distribution grid in terms of power quality and stability issues. This is one of the topics proposed by this paper which, unlike other reviews, aims to solve the aforementioned issues. Usually, the modules needed to solve power quality issues are based on power electronics. These modules fall into several categories, and the most important of these items are Power Filter Compensators, Unified Power Quality Conditioner (UPQC), Flexible AC Transmission System (FACTS) devices, etc. The methods and techniques used to increase the quality in power components can be used as a complement to the compensatory elements. Among these methods is the issue of optimizing the control systems of each module based on algorithms or optimization techniques or control strategies, or other methods based on automatic learning, etc.

Another objective of this study is to fill the gap by reviewing and comparing power quality issues, solutions, and standards in HMGs. In addition, the main issues related to voltage sags, voltage swells, voltage and current harmonics, system imbalances and fluctuations are compared to ensure high quality MG output power. Finally, some recommendations and suggestions are highlighted to impro-ve the power quality in HMGs.

2.   Dear reviewer. We appreciate your suggestion, that is why in section 4, specifically in section 4.1, we describe each of the techniques which are summarized in Table 8, remaining as follows in the main text:

4.1. Linear and non–linear technique

4.2. Dynamic and Metaheuristic Optimization

4.3. Genetic Algorithm (GA) and Multi–Agent (MAS) Optimization

4.4. Fuzzy logic and other techniques

4.5. Optimal Power Flow (OPF) Optimization

4.6. Robust and Stochastic Optimization  

3.-  Dear reviewer, we have responded to your comments and have complemented the information on the PSO optimization technique by adding to this information mathematical models that will help the reader understand the scope of this technique.  

4.-   Dear reviewer. Thank you for your comment. In response to your suggestion, we have added a tabulation where we describe the advantages and disadvantages of the control strategies shown in Fig. 9 to facilitate the reader's understanding.  

We thank you and we really appreciate your comments that help us improve the quality and understanding of our manuscript.

Author Response File: Author Response.pdf

Reviewer 4 Report

I think the review is interesting to the readers of Sustainability. The review content covers a lot of topics associated with power quality Issues, optimization techniques and control strategies of microgrid based on renewable energy sources. However, in my opinion performance in presence of large excursions of the states should be dealt with nonlinear control strategies. In the review, only two nonlinear control strategies are mentioned (gain-scheduling and sliding mode control). For this reason, I suggest to include some papers considering this issue. For example, the authors could mention [A]-[D] to explain advantages of the techniques mentioned in those papers.

[A] Ferguson, J., Cucuzzella, M. and Scherpen, J.M., 2023. Increasing the region of attraction in DC microgrids. Automatica, 151, p.110883.

[B] Kabalan, M., Singh, P. and Niebur, D., 2016. Large signal Lyapunov-based stability studies in microgrids: A review. IEEE Transactions on Smart Grid, 8(5), pp.2287-2295.

[C] Zafeiratou, I., Prodan, I., Lefèvre, L. and Piétrac, L., 2020. Meshed DC microgrid hierarchical control: A differential flatness approach. Electric Power Systems Research, 180, p.106133.

[D] Mohammed, M.S., Al-Awasa, K.M. and Al-Majali, H.D., 2021. Energy management and control in microgrid with hybrid energy storage systems by using PI and flatness theory. International Journal of Engineering Trends and Technology, 69(11), pp.227-235.

Author Response

Dear reviewer. We are very grateful for your comments. Indeed, it is necessary to add information on nonlinear control strategies for applications in HMGs. Therefore, in section 5.4.4 we describe some of the strategies implemented in HMGs which relax the restrictive conditions on the parameters of the load, the stress path and the reference stress, guaranteeing the exponential stability of the desired equilibrium point.

We thank you and we really appreciate your comments that help us improve the quality and understanding of our manuscript

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I have no more questions to ask.