Investigation of the Impact of Fault Characteristics on the Cost-Effectiveness of Doubly Fed Induction Generator-Based Wind Systems in Withstanding Low-Voltage Ride-Through

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Ms. Nina Yin

Here is my reviewing report for the manuscript under title “investigation of the Impact of Fault Characteristics on the Cost-Effectiveness of DFIG-Based Wind Systems in Withstanding LVRT” with ID sustainability-3073229.

 

The manuscript is written in correct English language, and well-organized structure, the findings are explained in a good and understandable way. Accordingly, the manuscript in the present form can publish in Sustainability.

Regards 

Author Response

Thank you so much, I really appreciate your valuable review.

Reviewer 2 Report

Comments and Suggestions for Authors

The article 'Investigation of the Impact of Fault Characteristics on the Cost-

Effectiveness of DFIG-Based Wind Systems in Withstanding LVRT' is interesting 

and contains a description of current technical and scientific issues. For a better 

reader's understanding of the article, I suggest including the following comments 

in the text of the article : 

1. equations (1 and 2), Figure 6 - regarding coordinate systems : 

whether two systems are used to describe the generator 

rotating reference frame : one with synchronous speed ws, the other 

with -ws velocity ?

2. Figure 6 - a different method of voltage sagging was used, different 

from that used in European countries. Please note this and identify the consequences.

3. lines 237, 268, 270 - please describe in detail the speed indications occurring here:

w, ws, wr . 

4. general remark on the drawings - the numerical values describing the axes of 

these drawings are illegible,

5. Line 312 - briefly describe the Crowbar strategy,

6. line 436 - why between phase (a) and ground ?

Author Response

For research article

Investigation of the Impact of Fault Characteristics on the Cost-Effectiveness of DFIG-Based Wind Systems in Withstanding LVRT

 

Response to Reviewer 2 Comments
1. Summary
Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files
Comments 1: equations (1 and 2), Figure 6 - regarding coordinate systems: whether two systems are used to describe the generator rotating reference frame: one with synchronous speed , the other with -  velocity ?
Response 1: Thank you for pointing this out. The DFIG and power system have an underdamped response characteristic when subjected to a failure., and their transient response includes both & - components.   Comments 2: Figure 6 - a different method of voltage sagging was used, different from that used in European countries. Please note this and identify the consequences. Response 2: Thank you for pointing this out. I agree with this comment, therefore, the paragraph preceding Figure 6, specifically lines 224-228, has been revised as follows:   “Although the representation and symbols of the DFIG equivalent circuits differ depending on the regions, they all share the same principle and provide equal results. Therefore, the stator positive and negative sequence short circuit currents can be determined using, shown in Figure 6, within a synchronous rotating reference frame [42-44], as follows:         Comments 3: lines 237, 268, 270 - please describe in detail the speed indications occurring here: , Response 3: Thank you for pointing this out. I agree with this comment, therefore, the following has been done: ·      ·        Comments 4: general remark on the drawings - the numerical values describing the axes of these drawings are illegible, Response 4: Thank you for pointing this out. I agree with this comment, therefore, I updated the numerical values for the following figures: 8, 9, 11, 12, 13, 14, 15, 16, 17, and 18.   Comments 5: Line 312 - briefly describe the Crowbar strategy, Response 5: Thank you for pointing this out. I agree with this comment, therefore, The following statement is added, line 310-311, to briefly describe the Crowbar approach: “by using a resistor to shorten the rotor terminals during an overvoltage and directing extra current away from the RSC”   Comments 6: line 436 - why between phase (a) and ground? Response 6: Thank you for pointing this out. Any of the three phases, namely a, b, or c, might be utilized to represent the single phase to ground. However, for the sake of simplicity and consistency, I have chosen to use phase a throughout the whole manuscript.

 

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The paper addressed the problem of fault characteristics on the cost- effectiveness of DFIG-based wind systems in withstanding LVRT. The topic is interesting and valuable. It is suggested to be accepted after some modification:

1. The reference is full of application and development in wind farms. Some novel wind turbine structures may be worthwhile for index, such as "Cross-wind dynamic response of concrete-filled double-skin wind turbine towers: Theoretical modelling and experimental investigation. Journal of Vibration and Control, 2023".

2. Some theory work is derived from the current literature. What is the highlight of the theoretical model in this paper?

3. There is a lack of estimation flow chart for this paper. It is suggested to be complemented.

4. Some legends are missing in some figures, such as the red lines, yellow lines, blues lines. Not sure what it means?

5. The conclusion should be modified brief, and present some useful data in engineering field.

Author Response

For research article

Investigation of the Impact of Fault Characteristics on the Cost-Effectiveness of DFIG-Based Wind Systems in Withstanding LVRT

 

Response to Reviewer 3 Comments
1. Summary
Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files
Comments 1: The reference is full of application and development in wind farms. Some novel wind turbine structures may be worthwhile for index, such as "Cross-wind dynamic response of concrete-filled double-skin wind turbine towers: Theoretical modelling and experimental investigation. Journal of Vibration and Control, 2023". Response 1: Thank you for pointing this out. I agree with this comment, therefore the citation is included in the paper as number 6 in lines 54 and 504.

Comments 2:

Some theory work is derived from the current literature. What is the highlight of the theoretical model in this paper?

Response 2:

Thank you for pointing this out. I agree with this comment, and the theoretical model presented in this study is prominently highlighted as follows:

• From line 250 to 257, Equation (4) is used to show how the the magnitude of the forced AC component is negligible, especially in cases where the voltage drop is substantial, which signifies a considerable value of voltage sag.
• From line 281 to 294, Equation (7) and Equation (9), it can be inferred that during a single line to ground (SLG) fault at phase (a), there is a significant increase in the rotor current, regularly from 3 to 4 times the steady-state current, leading to increased mechanical loads on the rotor and other related components.
• From line 333 to 337, It can be concluded from Equation (10) that the short circuit currents may be significantly decreased with the increase in fault resistance. However, since the footing resistances of each tower connected to the ground wire are parallel, the effective fault resistance is significantly decreased when the transmission-line towers are tied together with overhead ground wires next to the substation.

 

Comments 3:

There is a lack of estimation flow chart for this paper. It is suggested to be complemented.

Response 3:

Thank you very much for the wonderful recommendation; however, due to the length of the paper and the fact that there will be additional future work that will be given in a following article that will contain a flowchart to clarify the idea better, I would like to request that you reconsider your suggestion.

 

Comments 4:

Some legends are missing in some figures, such as the red lines, yellow lines, blues lines. Not sure what it means?

Response 4:

Thank you for pointing this out. I agree with this comment, and therefore, the following has been done:

• I inserted the values (i_a, i_b, i_c) into a visually distinct text within figure 8, positioned above their corresponding waveforms. This was done to enhance the clarity of the phase currents throughout the entire publication.
• I inserted the values (v_a, v_b, v_c) into a visually distinct text within figure 11, positioned above their corresponding waveforms. This was done to enhance the clarity of the phase voltages throughout the entire publication.

 

Comments 5:

The conclusion should be modified brief, and present some useful data in engineering field.

Response 5:

Thank you for pointing this out. I agree with this comment, and therefore, I decreased the word count of the "Conclusion" section from 375 to 306 by implementing the following changes:

 

“This paper investigates the impact of various fault characteristics on the LVRT capability of MGs to comply with grid codes during faults. The objective is to provide a clear picture for the grid response to different fault characteristics to help selecting the most suitable LVRT code and LVRT enhancing technique, whether internal or external, and the appropriate ratings for these devices, with the aim of reducing the installation costs of WFs.

It is found that these characteristics are significantly impacting LVRT and system stability, and determining the speed at which faults are detected. For example, it is recommended to maintain adequate footing resistance, ground wire insulation from both towers and the station ground mat, which can greatly reduce short circuit currents and meet the requirements of the LVRT code. In addition, the total fault resistance and, accordingly, the fault currents, are influenced by various other factors such as fault location, fault duration, ambient temperature, pressure, and the properties of the faulty conductor. Therefore, designers should consider all these factors to ensure the reliable integration of renewable energy sources into the grid at the lowest possible cost.

In addition, it is essential to consider the impedance of the transmission line between PCC and the WF when determining the appropriate LVRT code for a certain area. This impedance has a considerable effect on the impact of fault currents on the WF. It is highly desirable to increase the impedance during a failure to restrict the flow of fault currents. However, the devices employed for this purpose are quite expensive. Therefore, to lessen the financial burden on the system, it is crucial to employ an efficient design or lower the rating.

The study provides case studies, which can be advantageous for engineers in guaranteeing the reliable integration of renewable energy sources into the power grid in a cost-efficient manner.

 

 

 

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

See the attached file.

Comments for author File: Comments.pdf

Author Response

Thank you so much, I really appreciate your valuable review.