Predictive Control for Current Distortion Mitigation in Mining Power Grids
, Alex Navas-Fonseca 1, Freddy Flores-Bahamonde 1, Luca Tarisciotti 1,*, Cristian Garcia 2, Felipe Nuñez 3, Jose Rodriguez 4 and Aldo Z. Cipriano 3
Round 1
Reviewer 1 Report
This paper presents predictive control strategy for current distortion mitigation in mining power grids. The idea presented in the paper is good. The article is well organized; the results are well presented and discussed. However, the article needs minor revision. Some comments and suggestions are given here:
The choice of the predictive command should be justified.
Improve the quality of figures 8(c) and 8(b).
Some parameters used in the equations should be defined.
Author Response
The authors would like to thank the reviewer for the effort in improving the manuscript quality. Please find the detailed answers to the reviewer questions in the attache pdf and revised manuscript.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
1) Some terms are unknown and have been used in different forms in the literature. For instance, "Model-based Predictive Control" is a new term, while "Model Predictive Control" has been used for decades.
2) Literature review is too poor and should be improved. Multiple optimize-based schemes have been introduced in the literature that could be discussed in the manuscript. Consider improving the literature review by discussing the following manuscripts:
[R1]. "Robust Optimal Power Management System for a Hybrid AC/DC Micro-Grid", 2015. [http://doi.org/10.1109/TSTE.2015.2405935]
[R2]. "An Improved Model Predictive Control Method Using Optimized Voltage Vectors for Vienna Rectifier With Fixed Switching Frequency", 2023. [http://doi.org/10.1109/TPEL.2022.3205946]
[R3]. "Multi-Vector Model Predictive Current Control for Paralleled Three-Level T-Type Inverters With Circulating Current Elimination", 2022. [http://doi.org/10.1109/TIE.2022.3208607]
3) How can one make sure that the proposed optimization problem is convex; that is, it has only one and unique optimal solution.
4) Consider comparing your method with a state-of-the-art method. This would help the readers to understand pros and cons of the proposed method.
5) Consider providing future directions. This would help the readers to understand improvement potentials and opportunities.
Author Response
The authors would like to thank the reviewer for the effort in improving the manuscript quality. Please find the detailed answers to the reviewer questions in the attached pdf and revised manuscript.
Author Response File: Author Response.pdf
Reviewer 3 Report
In this paper the authors propose an original MPC-based scheme for current
distortion mitigation by including power harmonics compensation and total current distortion constraints. The proposed method uses the frequency harmonics decomposition of real power, enabling to control their magnitudes by a MPC and their angle phases by a traditional PI controller. to the reviewed literature. In order to satisfy the current distortion imposed by IEEE 1547 Standard the optimization problem allows controlling two current harmonics components by considering one power harmonic component, and also by define real power constraints. Four different cases are presented by using a MicroLabBox-dSPACE and an OP4510 241 real-time computer in HIL configuration. The simulation results show that the proposed scheme is capable of bounding the current distortion according to IEEE 1547 Standard for both individual harmonics and the total rated current distortion, through inequality constraints of the optimization problem.
The proposed method is well described and constructed. The simulation results seem promising.
Minor comments to authors:
1. Please verify the language. Several examples: page 3/line 116 ..an MPC; page 6/201 …TRD; e.a.
2. Define: N in equations (14a), and (14b); IIR at page 7/line 234; e.a.
3. Improve the quality of Figures 5-9.
4. It may by useful for Journal’s readers to provide a logical diagram (flow chart) of your control strategy (page 7, after Figure 2).
Author Response
The authors would like to thank the reviewer for the effort in improving the manuscript quality. Please find the detailed answers to the reviewer questions in the attached pdf and revised manuscript.
Author Response File: Author Response.pdf
Reviewer 4 Report
The paper proposes a predictive control-based scheme for mitigating the current distortion in the coupling node between utility grid and the mining facility-power system. This task is included into the microgrids control hierarchy. Hardware-in-the-Loop simulation results are reported.
The paper matches the scope of the Journal and of the Special Issue.
In its current form, the paper is not suitable for publication. The theoretical concepts are not adequately detailed and the results must be further discussed. In addition, the literature review must be extended.
In the following, some notes are reported.
General notes:
1) In my opinion, following the journal guidelines (https://www.mdpi.com/journal/applsci/instructions), the paper must contain an introduction section, materials and methods section, results section, discussion section and conclusion section. I suggest to reorganize the paper following these instructions.
2) For each innovation provided by the paper, a claim must be added in the core of the paper.
3) Please report the measurement units and the description of each term used in all equations when each term is first introduced. For example, H in Equation (5), m in Equation (11a), and N in Equation (14a) are not defined.
4) Please add a reference for all concepts that are exploited in the paper when they are already in the literature.
Section 1 (Introduction)
- Please extend the literature review.
Section 2 (Preliminaries)
1) In the equations reported in this section, is never specified if the equations refers to continuous-time and/or discrete-time.
2) It seems that, in Equations (2a)-(2b), some brackets have been omitted. Please check it.
3) Please detail the steps to obtain Equations (3)-(4)-(5)-(6)-(7).
4) In Equation (6), what is the meaning of the “and” symbol?
5) Equation (9) is not clear: the left term is the same for both inequalities? Or is an inequality symbol missing?
6) Equation (9): please detail how the term at the second row is obtained.
7) Equation (9): maybe a typo is present (in the first term within the square bracket it seems that the subscript h+1 must be present in both terms). Please check it.
Section 3 (Optimization problem formulation)
1) In the equations reported in this section, is never specified if the equations refers to continuous-time and/or discrete-time. In case of discrete time equations how are obtained? What is the discretization procedure?
2) A clear and precise definition of the Manipulated Variables, Controlled Variables and Disturbance Variables for the analyzed control problem is not present. Please add it.
3) Lines 187-191 are not very clear; besides, the reported concepts seem to be key assumptions for the paper. Please rewrite and detail.
4) The derivation of the nine equations (11a)-(15) is not reported. Please add it or add insights for their computation.
5) Equation (11c) is not clear: usually the slack variable/variables are introduced in the MPC formulation with a different sign in the lower and upper constraints. The same note holds for Equation (14a). Please check it.
6) In lines 201-202 the authors state “TRD is stated by the IEEE std 1547 as an additional power quality requirement, defined by (13)”, but equation (13) defines THD. Please clarify.
7) Please accurately motivate the defined optimization problem given by the minimization of (16) subject to the constraints (11), (14), and (15).
8) Details on the tuning choices must be added.
9) Details on the analysis of computational time must be added.
Section 4 (Experimental Setup and Results)
1) Details on the PI controller must be added to the paper. Maybe this part can be introduced in the theoretical section of the paper.
2) Figure 2 must be better detailed and described. Maybe it can be moved in theoretical section of the paper.
3) The discussion section must be enriched.
Section 5 (Conclusion and Final Remarks)
- This section must be extended.
Author Response
The authors would like to thank the reviewer for the effort in improving the manuscript quality. Please find the detailed answers to the reviewer questions in the attached pdf and revised manuscript.
Author Response File: Author Response.pdf
Reviewer 5 Report
Please find here the correct report: 1) The contribution of the proposed scheme is not highlighted and remains unclear. Authors should clearly present the novelty. 2) Related to the above, an extensive literature review is presented but what are the limitations of the reviewed references that this work fills? 3) No comparative results between the proposed method and the previously reported methods with regard to low-order harmonics compensation are presented. 4) From the presented Figures we may notice that the proposed method is effective under constant load demand. Is it equally effective when the load demand is changing? 5) The presented control strategy is described very briefly. The authors should provide more details to help readers understand and possibly replicate the strategy Major Revision
Comments for author File: Comments.pdf
Author Response
The authors would like to thank the reviewer for the effort in improving the manuscript quality. Please find the detailed answers to the reviewer questions in the attached pdf and revised manuscript.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
No further comment.
Author Response
We would like to thank the reviewer for the effort in improving the mnuscript quality.
Reviewer 4 Report
The paper proposes a predictive control-based scheme for mitigating the current distortion in the coupling node between utility grid and the mining facility-power system. This task is included as a secondary level objective control referred into the microgrids control hierarchy. Hardware-in-the-Loop simulation results are reported.
The paper matches the scope of the Journal and of the Special Issue.
In its current form, the paper is not suitable for publication. Some concepts still need to be clarified and some equations need further checks. In addition, the literature review must be further extended.
In the following, some notes are reported.
General notes:
- In the revised version of the paper, the authors adjusted some sections in order to clearly state the novelties. In the Introduction (Section 1), at page 3 the authors reported a bullet list with three claims. In my opinion, a further step is required for the explanation of the third point. Please motivate why the Hardware-In-the-Loop (HIL) system test environment represent a novelty in the field.
Section 1 (Introduction)
- Please further extend the literature review. In the revised version of the paper, the authors extended this part but, in my opinion, a further step is required.
Section 2 (Preliminaries)
- The Appendix reported by the authors should be added to the article to understand the mathematical steps in the formulation.
- Equation (9a): as already observed in the first review, maybe a typo is present (in the first term within the square bracket it seems that the subscript h+1 must be present in both terms). Please check it and check also the Equation (A.18).
Section 3 (Optimization problem formulation)
- Lines 229-230: in my opinion, the concept described on these rows must be further detailed in order to improve the readability of the paper or at least add a focused literature reference.
- With regard to the Disturbance Variables, please report some considerations whether or not they need to be predicted in the proposed control scheme
- Line 260: maybe “THDs” must be replaced by “THDs” in order to ensure consistency with Equation (14a).
- With regard to the tuning choices, the authors enriched Section 3.2. I suggest to add some literature references (for example, the three references reported by the authors in the cover letter) in order to further assess this aspect.
- In the revised version of the paper, the authors have modified equations (12a), (14a) and (15) in order to adjust the formulation in terms of slack variables. In the updated paper the lower bound of the considered equations appears to be a hard constraint. Is this the case? If so, please motivate this design choice.
Author Response
We would like to thank the reviewer for the effort in improving the mnuscript quality. Please find detailed response to the reviewer comments in the attached pdf.
Author Response File: Author Response.pdf
Reviewer 5 Report
The authors have improved the paper according to my comments. I suggest to publish the paper as is.
Author Response
We would like to thank the reviewer for the effort in improving the mnuscript quality.
