Projection-Based Coordinated Scheduling of Distribution–Microgrid Systems Considering Frequency Security Constraints

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper proposes a projection-based coordinated scheduling method for distribution–microgrid systems that embeds frequency security constraints into optimization, ensuring stable operation during unintentional islanding while improving coordination efficiency, accuracy, and privacy, as validated on a modified IEEE-33 bus system. Overall, the results are sufficient and interesting. However, there are several points where clarifications, justifications, and expansions would improve the manuscript.

 

1. The abstract should be revised to include key quantitative findings from the study, thereby more effectively emphasizing its main contributions and results.
2. Reference [6] is cited but not discussed in the introduction. Please revise accordingly.
3. The paper highlights that microgrids serve as critical platforms for integrating high-penetration distributed energy resources, including renewable generation with significant uncertainty. However, uncertainty-oriented methods are not discussed. It is recommended to include and discuss scenario-based stochastic optimization approaches, such as “Enabling high-efficiency economic dispatch of hybrid AC/DC networked microgrids: Steady-state convex bi-directional converter models.”, to enhance the quality and contextual relevance of the introduction.
4. Please clarify how the distribution system is modeled within the coordinated scheduling framework of the distribution–microgrid system.
5. In the case study, the IEEE 33-bus system is adopted for the distribution network. What system is used for the microgrid network? Please specify.
6. There are minor typographical errors, such as “Table summarizes the total operation costs,” which should be corrected.
7. The conclusion section should also discuss the limitations of the study and propose potential directions for future research.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This paper presents a well-structured and technically strong contribution to coordinated energy management, focusing on the projection-based scheduling of distribution–microgrid systems. The authors introduce a novel projection-based coordination algorithm that enhances convergence efficiency and reduces communication overhead between Distribution System Operators (DSO) and microgrid controllers. The methodology is supported by detailed mathematical formulation and validated through IEEE 33-bus test case simulations. While the work is innovative, some theoretical and practical aspects require further clarification to strengthen its applicability and scientific impact.

1. Introduction and Literature Review

1) The introduction clearly defines the importance of coordinated scheduling, but the discussion of related work could better position this paper relative to recent hierarchical and decentralized optimization studies.
2) Please expand on how the proposed projection-based approach advances beyond conventional decomposition or ADMM-based coordination frameworks.
3) The study should also reference recent research such as “Ghasemi Naraghi. S., Kareck. T., Jiang. Z, Multi-objective Optimization of Steam Cracking Microgrid for Clean Olefins Production”, which complements the present work by addressing stochastic coordination in complex energy systems.

2. Methodology

1) The bi-level optimization formulation is well presented, but additional explanation of the projection operator and its convergence guarantee would improve mathematical clarity.
2) Please discuss scalability: how would the algorithm perform in larger distribution systems or multiple interacting microgrids?
3) It would be helpful to include pseudocode or a concise flowchart of the proposed scheduling process for improved readability.

3. Results and Discussion

1) The IEEE 33-bus case demonstrates the feasibility of the approach, though more detail on runtime and convergence criteria would enhance transparency.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript entitled “Projection-Based Coordinated Scheduling of Distribution–Microgrid Systems Considering Frequency Security Constraints” addresses an important topic in modern distribution–microgrid (DN–MG) operation. The integration of frequency-security constraints into a projection-based scheduling framework is technically relevant, especially given the growing penetration of low-inertia microgrids. The work is clearly presented and supported by mathematical modeling and case studies on a modified IEEE-33 bus system.

While the paper is generally well organized and the technical approach is interesting, several issues concerning novelty, clarity, and practical validation should be addressed to strengthen its contribution.

I added five major comments, if addressed, could substantially enhance the manuscript’s scientific rigor, clarity, and overall suitability for publication. Please consider it.

Comments

Novelty and Positioning (Introduction, Sec. 1)

• The manuscript states that it “proposes a projection-based coordinated scheduling method under microgrid frequency constraints.”
  However, several existing works (e.g., [24]–[26], [17], [30]) have already introduced non-iterative or projection-type methods.

• The authors should explicitly clarify how the proposed inner-approximation based on power–energy boundaries differs from and improves upon these prior approaches, particularly in terms of:

  • computational efficiency,

  • coverage ratio improvement,

  • handling of temporal coupling.

Frequency-Security Modeling (Sec. 2)

• The derivation of the linear maximum-frequency-deviation constraint (Eq. 8) relies on a conservative approximation.
  A more detailed justification of the linearization step and its practical conservativeness vs. accuracy trade-off would be helpful.

• The assumed RoCoF and frequency-deviation limits should be compared with standard grid-code or industry limits to demonstrate realism.

Scalability and Practical Deployment (Sec. 4–5)

• The case study uses three microgrids on the IEEE-33 test feeder.
  The authors should discuss computational performance and convergence for larger, more realistic systems with tens of microgrids and finer-time resolution (e.g., 15-min scheduling).
• Communication and privacy advantages are emphasized, but practical implementation aspects (e.g., required data exchange, response time for day-ahead vs. real-time operation) should be described.

 

Economic Interpretation (Sec. 5.1)

• Although the focus is on frequency security, the trade-off with operational cost is central.
  The authors should analyze why energy-storage costs rise only slightly but exchange revenues drop significantly, and relate this to constrained flexibility.

 

Validation of the Approximation (Sec. 5.4)

• The proposed method achieves 87.6 % coverage vs. 38.7 % for the box method.
  The authors should comment on the remaining uncovered feasible region and potential operational risks (e.g., infeasible dispatch points) due to inner-approximation.

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thanks for the careful revisions. The authors have fully addressed all my concerns.

Reviewer 2 Report

Comments and Suggestions for Authors

They addressed my concerns.