Finite Frequency H∞ Control for Doubly Fed Induction Generators with Input Delay and Gain Disturbance
Round 1
Reviewer 1 Report
The paper presents a control of a DFIG with input delay and gain disturbance.
The main problem with the paper is the very simplified model used in the study. The linearized state-space model for DFIG is dimension 3. In the references indicated below, models of order 15 to 20 are used.
Another handicap is the validation of the control with the simplified model itself. To demonstrate that the simplifications are acceptable, the control must be validated with a more realistic model.
Therefore, I consider that the contributions of the paper are of low quality and should be rejected.
A) B. Sun, P. Ju, M. Shahidehpour and X. Pan, "Calculation of Stable Domain of DFIG-Based Wind Farm in Series Compensated Power Systems," in IEEE Access, vol. 8, pp. 34900-34908, 2020.
B) Y. Jia, T. Huang, Y. Li and R. Ma, "Parameter Setting Strategy for the Controller of the DFIG Wind Turbine Considering the Small-Signal Stability of Power Grids," in IEEE Access, vol. 8, pp. 31287-31294, 2020,
C) R. Liu, J. Yao, X. Wang, P. Sun, J. Pei and J. Hu, "Dynamic Stability Analysis and Improved LVRT Schemes of DFIG-Based Wind Turbines During a Symmetrical Fault in a Weak Grid," in IEEE Transactions on Power Electronics, vol. 35, no. 1, pp. 303-318, Jan. 2020
Author Response
Thanks the reviewer for the highly pertinent evaluation to our paper. The main topic of this paper is to work out a finite-frequency H-infinite robust control in the DFIG system subject to input time delay. This problem has not been examined fully up to the best knowledge of the authors.
As for the low-order modeling deficiency criticized by the reviewer, we must admit that the comment is meaningful. However, in principle, the suggested method also applies to those 15th to 20th -order models, as long as their high-order linear approximations are available. We hope that it is allowable for the authors to deal with those higher-order cases in our up-coming research.
All the suggested references are included in the bibliography and cited appropriately in the main context.
Reviewer 2 Report
Double-fed machines are a standard (one of two) that has been used for many years in wind farms. Also, their control systems are known and tested. The article presents the study of the stability of DFIG with various variants of regulators carried out on the basis of a mathematical model. There is no reference to the structure of the DFIG control system itself (FOC, DTC, etc.). Reading the article, it is difficult to understand the practical application of the research results.
However, the article is at a high academic level, so after minor corrections it can be published.
Author Response
Thanks the review for his/her careful reading and pertinent revision suggestions. Our responses are given below. Please check if our responses are sufficient and satisfactory.
Responses: Yes, the reviewer is correct. Related discussion about the vector control of the control input voltage has been added in the fourth paragraph of Section 2.1, where references[16],[17] related to FOC, DTC etc are listed. To address time delay to DFIG, the finite frequency disturbance suppression problem is concerned in this paper.
Reviewer 3 Report
The work is devoted to improving the quality of electricity generated by a wind generator. This corresponds to modern trends of intensive development and implementation of renewable energy sources.
In the presented work, an interesting mathematical apparatus was used, which made it possible to determine the controller settings, which provide an increase in the quality of regulation.
There are a number of issues related to this material:
1. In the description of the relevance of the topic, it is desirable to indicate which indicators of the quality of electricity generated by the wind generator with the control systems used do not meet the requirements (in numbers).
2. It is desirable to give figures on the indicators of the quality of regulation in the systems of regulation used in practice. What quality indicators should be and what they are in practice.
3. For what power range of wind turbines are these problems typical?
4. It is desirable to describe how the aerodynamic parameters of the wind turbine are taken into account in the mathematical model.
Author Response
Thanks the review for his/her careful reading and pertinent revision suggestions. Our responses are given below. Please check if our responses are sufficient and satisfactory.
1) Yes，the reviewer is correct that grid-connected wind turbine technologies impact power quality. We have added indicators of the quality of electricity generated by the wind generator in the second paragraph of the introduction.
2) The H-infinite performance indicator is an input-to-response worst-case evaluation and thus is of smaller-is-better significance. In fact, a practical DGIF system has no electrical features that are directly related to the indicator.
3) Yes, we add wind turbine capacity ‘5MW’ in the simulation.
4) Yes, additional notes on wind turbine parameters are included in the third paragraph of Section 2.1.
Reviewer 4 Report
General remarks
Line 28. “wind” is “Wind”.
Line 83. Define an abbreviation first time is mentioned, here “PWM” and you can use it only as abbreviation in Line 154.
Lines 205 to 231, 238 to 246, 258 to 263, representing the proofs of the theorems, wouldn’t be better to be included in an Annex?
Congratulations on a very good paper!
Author Response
Thanks the review for his/her careful reading and pertinent revision suggestions. Our responses are given below. Please check if our responses are sufficient and satisfactory.
‘Wind’ and ‘PWM’ have been changed to their correct form, and the proofs of the theorems are now given in the appendices to keep the main context concise.
Reviewer 5 Report
Dear Authors. Thank you very much for your efforts in this work, but there some comments, and depending on these comments the decision is major, so please to response the following:
1- The most important point that forces me to accept any work is the originality, and novelty, in the manuscript they are not clear.
2- The flow chart will help to understand your work, so please add a flow chart that will facilitate procedure understanding.
3- Please organize the comparative study in a table to present the comparison between previous work and yours.
4- The abstract and conclusion must be rewritten.
5- Please update your refrences.
Author Response
Thanks the reviewer for his/her careful reading and pertinent revision suggestions. Our responses are given below. Please check if our responses are sufficient and satisfactory.
1）Yes, the reviewer is correct. The main contributions or technical advantages are stressed at the end of the introduction and the conclusion.
2）Yes, regarding the reviewer' flowchart suggestion, we add the flowchart in Fig. 3 to facilitate understanding.
3）The innovation of this paper is the H-infinite robust control from in the finite frequency domain sense, while consider harmonic interference suppression in DFIG systems with input time delay. Comparison studies between the general full frequency H-infinite control and this suggested method are done in Section 4.6.
4）The authors have carefully and thoughtfully rewritten the abstract and conclusions to highlight the innovative points and applicability of the paper.
5）More references have been added and cited in the context accordingly.
Round 2
Reviewer 1 Report
I am satisfied with the changes.
Author Response
Thank you for the reviewer's high evaluation and affirmation of my revision.
