A Modified Reduced-Order Generalized Integrator–Frequency-Locked Loop-Based Sensorless Vector Control Scheme Including the Maximum Power Point Tracking Algorithm for Grid-Connected Squirrel-Cage Induction Generator Wind Turbine Systems

Round 1

Reviewer 1 Report

1. Clarify the novelty and contributions and purpose clearly.

2. The introduction needs significant expansion and restructuring. It should include the motivation for the research, a clear explanation of the main objectives, and emphasize the improvements compared to previously published works. Additionally, the literature review must be improved to better state the contribution of this research and should consider other relevant works with similar objectives (as httpshttps://doi.org/10.1016/j.ijhydene.2016.06.109, https://doi.org/10.2202/1553-779X.1052)

3.The research's motivation should be explicitly stated, and the paper's innovation must be adequately emphasized.

4. Present the recommended method in comparison with other publications from the literature to demonstrate its superiority and effectiveness.

5. The paper proposes a novel speed sensorless control method for grid-connected squirrel-cage induction generator (SCIG) wind turbine systems, integrating the maximum power point tracking (MPPT) algorithm with a modified reduced-order generalized integrator (ROGI)-frequency-locked loop (FLL) approach. The modified ROGI-FLL-based observer allows for precise estimation of rotor flux linkages using d-q axis rotor electromotive forces (EMFs), improving the accuracy of rotor position determination.

6.The inclusion of DC offset compensators in the modified ROGI-FLL structure effectively reduces oscillations in estimated rotor speed caused by DC offset in estimated rotor flux linkages, leading to improved stability and performance. Which is a positive point of this paper.

7. The ROGI demonstrates excellent capability in mitigating the negative effects of high-frequency components on rotor flux linkage estimation, contributing to enhanced system performance.

8. The paper provides a thorough dynamic response analysis of the modified ROGI-FLL with DC offset compensators, demonstrating the feasibility and effectiveness of the proposed method.

9.While the effectiveness of the proposed approach is demonstrated some negative points are noticed, please clarify and give some details on this following points to improve your paper:

1. While the feasibility of the proposed method is demonstrated in comparison with an existing method based on dual second-order generalized integrator-frequency-locked loop (SOGI-FLL) with DC offset compensator, a more comprehensive comparative analysis with other state-of-the-art approaches could provide deeper insights into the performance and limitations of the proposed method.
2. The paper primarily focuses on theoretical analysis and simulation results to validate the proposed method. Including experimental validation on real-world SCIG wind turbine systems could enhance the credibility and applicability of the findings.
3. The proposed method involves a complex control algorithm and observer structure, which may pose challenges in practical implementation and require advanced technical expertise for design and implementation.
4. The applicability of the proposed method may be limited to specific SCIG wind turbine systems and operating conditions, and its effectiveness in diverse environments or with different wind turbine configurations may require further investigation.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The study introduces a novel speed sensorless control approach for grid-connected squirrel-cage induction generator (SCIG) wind turbine systems. This method seamlessly integrates the maximum power point tracking (MPPT) algorithm with an enhanced reduced-order generalized integrator (ROGI) and a frequency-locked loop (FLL), allowing for accurate estimation of the rotor flux linkage and its positional determination. The introduction of a DC offset compensator significantly reduces estimation oscillations, thereby enhancing system stability. Furthermore, the proposed method demonstrates excellent suppression of high-frequency components, minimizing their negative impact on rotor flux linkage estimation. This article is well-organized and could be accepted directly, but there are a few minor details that require attention for improvement and accuracy.

1.  The punctuation marks after the formula need to be removed;

2.  The use of "Figure" in the figure and "Fig" in the article needs to be consistent;

3.  There are no horizontal and vertical axes in the figure, which need to be explained or added.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The suggested ROGI-FLL based control for SCIG with MPPT, in the presented work, is a replication with minor modifications of the original work (Sensorless Control of Variable-Speed SCIG Wind Energy Conversion Systems Based on Rotor Flux Estimation Using ROGI-FLL ; doi: https://doi.org/10.1109/JESTPE.2022.3207904).

1. the mathematical modeling in these two papers is almost identical

2. Figure 2 is the same as in the original work (doi stated above)

3. Figs (4-5) exist identically in the original work

4. The DC offset compensator of Figure 7 is not sufficient to make this work "novel" as stated in the title

5. Not a single concrete information is stated upon the MPPT. No code snippets, no flowchart, no working mechanism.

6. Figure 8 exists identically in the original work

7. The SCIG parameters in Table 1 are identically the same in Table 1 of the original work. Same fact applies for Table 2!

8. Results are almost the same between Figure 18 (in this presented work) and Figure 17 in the original work 

9. The average error in the speed estimation in this work and the original are almost identical

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Thank you very much for addressing each comment. You can clearly see the resulting quality improvement. My previous concerns were eradicated, mainly due to the modifications of the previously stated problematic figures. A final minor recommendation still exists:

1. your provided explanation as a reply to Comment 1 is to be kindly inserted appropriately in the modified version of the paper 

Author Response

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Author Response File: Author Response.pdf