Self-Balancing Supercapacitor Energy Storage System Based on a Modular Multilevel Converter

Round 1

Reviewer 1 Report

1. All Figure Simulation Results quality should be improved
2. In-Line no. 234 - 'slightly reduced when SC voltage is lower than 1.5V". But in the flow chart ( see Figure 11. Mode selector diagram.- 1.4V. What is the threshold value 1.4V/1.5V??
3. Balancing control is not clear.
4. Eq.no (19) - Please see. Is it Right?
5. Figure 5. is not clear.
6. Figure 4. Buck-mode waveforms are not clear.
7. Abstract should be rewritten 

Author Response

"Please see the attachment."

Since Reviewer 1 reported extensive editing of the English language the updated manuscript version was proofread by a native English speaker.

Author Response File: Author Response.docx

Reviewer 2 Report

Aiming at the problem of improving power quality in the environment of power transmission, this paper introduces the design of an energy storage system (ESS) based on a modular multilevel converter (MMC) with bidirectional power flow. The energy storage system effectively reduces the number of cascaded stages and allows the supercapacitors to be connected to the grid to perform the high-power transfer. The reviewers have the following opinions on the problems of the article. The specific amendments are as follows:

1. Introduction section is incomplete. It should include four key components: motivation, literature survey, contributions, and the organization of paper. Please modify this section accordingly.
2. The relevant work in the introduction should clearly point out the shortcomings of the relevant research, which is insufficient in this present version.
3. The formula problem in the article：

• The meaning of the letters in the formula and the meaning of the upper and lower marks in the formula are not clearly described. It is suggested that the author add tables.
• The description of many formulas is not clear, and the article does not link the process with the demonstration of formulas.

4. The most significant drawback of the simulation section is that there is no performance benchmarking with other state-of-the-art approaches. The simulation results should be extended to support the proposed approach effectively. Author need to add more illustrative figures as well as some comparison tables to clearly highlight the key findings by simulation results.
5. The presentation of results are messy, Figures such as Figure 12 is very unfriendly to the readers, the authors are strongly required to reorganize the presentation of their results.
6. The following two articles investigating energy storage from the perspective of information science should be cited and discussed:

1) A Novel Consensus-Based Optimal Control Strategy for Multi-Microgrid Systems with Battery Degradation Consideration. T. Wang, H. Liang, H. Hua, Y. Qin, and J. Cao. CSEE J. Power and Energy Systems, 2021.

2) Stochastic Optimal Control Scheme for Battery Lifetime Extension in Islanded Microgrid via A Novel Modeling Approach. Y. Qin, H. Hua, and J. Cao. IEEE Trans. Smart Grid, 10(4), 4467-4475, 2019.

7. The references have the following problems:

1) Most of the references are too old. More recent works must be cited.

2) Too few references. The authors should cite more references.

8. The conclusion does not put forward the shortcomings of this study, and it is recommended to add some related comments.

Author Response

"Please see the attachment."

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

No more comments.