Round 1

Reviewer 1 Report

This study proposed to eliminate the DC-offset in the single-phase grid synchronization, using delay signal cancellation (DSC), and a fixed-length transfer delay (TD) based PLL. But, required corrections.

The Delta Wg used for the delays should be explained while creating the equations. The system is given only through signal processing. The circuit elements and circuit structure used here can also be given as a summary. Input reference values used for PI control should be well explained.

The contribution and innovation of the study should be better emphasized and comparisons with the studies done so far in this field should be made in more detail.  

Some simulation results obtained should be given in a more clear and understandable way.

Some upper and lower-case errors in my writing should be corrected.

Minor editing of English language required

Author Response

Response to the comments of reviewer#1

We express our sincere gratitude and appreciation for the valuable feedback provided by the reviewers. Their insightful comments will undoubtedly enhance the content and overall quality of our paper. With great consideration and attention, we have thoroughly revised our manuscript entitled "Grid-Connected Renewable Energy Sources: A New Approach for Phase-Locked Loop with DC-Offset Removal" according to the reviewers' comments. In response to their feedback, we have prepared a comprehensive list of itemized responses addressing each of their comments.

Point 1: The Delta Wg used for the delays should be explained while creating the equations. The system is given only through signal processing. The circuit elements and circuit structure used here can also be given as a summary. Input reference values used for PI control should be well explained.

 Response 1: We have thoroughly evaluated and provided a detailed explanation of all the equations pertaining to the delta theta. Additionally, we have included any missing equations in the small signal model section [lines 186-215].

In response to the second suggestion, we have incorporated relevant information regarding the electrical components utilized in the simulation. This information enables a better understanding of how the input signal was generated and how disturbances were introduced into the system [lines 268-271].

As per the last suggestion, we have now provided a comprehensive explanation of how we selected the damping factor. This decision was based on the phase margin, which is outlined in detail within the PI gain design section [lines 228-231].

 

Point 2: The contribution and innovation of the study should be better emphasized and comparisons with the studies done so far in this field should be made in more detail.

Response 2: In this study, we have enhanced the existing non-adaptive DSC PLL method by incorporating TD (Transfer Delay) and DSC (Delay Signal Cancellation) operators. By doing so, our objectives are to improve the performance of the PLL. To thoroughly evaluate the effectiveness of our proposed non-adaptive DCI PLL, we have conducted a comparative analysis with both adaptive and non-adaptive DSC PLL methods.

By comparing the proposed PLL with these existing methods, we are able to assess its performance in relation to key parameters such as accuracy, stability, and robustness. This comparative analysis will provide valuable insights into the effectiveness and advantages of our non-adaptive DCI PLL.

 

Point 3: Some simulation results obtained should be given in a more clear and understandable way.

Response 3: To enhance the clarity and comprehensiveness of our research, we have included additional simulation results in our study. These supplementary results further strengthen our findings and contribute to a more comprehensive analysis of the simulation outcomes. Figures 7 to 12 [lines 286-343].

To ensure the clarity and comprehensibility of our research, we have taken great care in explaining the results in a detailed manner within Table 1. This enables readers to easily interpret and understand the implications of the findings. [line 360]

We greatly appreciate this valuable input, and we believe that the inclusion of additional simulation results and the thorough explanations provided throughout the manuscript significantly improve the overall quality of our research.

 

Point 4: Some upper and lower-case errors in my writing should be corrected.

Response 4: By ensuring consistency in the use of upper and lower-case letters, we aim to enhance the overall readability and professionalism of the manuscript. These corrections have been implemented diligently to maintain a consistent and coherent writing style. We appreciate your attention to detail and thank you for bringing this issue to our attention. [Throughout the manuscript]

 

Author Response File: Author Response.pdf

Reviewer 2 Report

1. References need to be cited in order, not "3,8, 12,15,19" at random.

2. Authors should summarize the related works more succinctly, rather than introducing it in detail, leading to such a long 'Introduction;.

3. The font size is too small in mathematical formulas, such as equation 5, 10, and 12. 

4. The authors need to highlight the work in this paper and detail the original work in this study that differs from other existing methods. Unfortunately, the length of the third chapter 'Development' in the manuscript is almost the same as that of the first chapter 'Introduction'.

5. Although the author introduced a large number of improvement methods for PLL in the Introduction, they only compared it with adaptive DSC PLL and non adaptive DSC PLL in the experimental section, which cannot highlight the advantages of the method proposed in the manuscript. The author needs to compare with more existing methods (adding no less than 5, as many improvement methods have already been mentioned in introduction).

Author Response

Response to the comments of reviewer#2

We express our sincere gratitude and appreciation for the valuable feedback provided by the reviewers. Their insightful comments will undoubtedly enhance the content and overall quality of our paper. With great consideration and attention, we have thoroughly revised our manuscript entitled "Grid-Connected Renewable Energy Sources: A New Approach for Phase-Locked Loop with DC-Offset Removal" according to the reviewers' comments. In response to their feedback, we have prepared a comprehensive list of itemized responses addressing each of their comments.

 

Point 1: References need to be cited in order, not "3,8, 12,15,19" at random.

 Response 1: Thank you for your feedback. We appreciate your attention to detail regarding the order of references cited in the manuscript. We have carefully reviewed our reference citations and have made the necessary adjustments to ensure they are presented in a sequential and orderly manner. [Throughout the manuscript]

 

Point 2: Authors should summarize the related works more succinctly, rather than introducing it in detail, leading to such a long 'Introduction'.

Response 2: We have carefully revised and summarized the 'Introduction' section of our manuscript to ensure conciseness while still providing essential background information.[lines 26-115]

 

Point 3: The font size is too small in mathematical formulas, such as equation 5, 10, and 12.

Response 3: We have thoroughly reviewed all the equations in our manuscript and have made the necessary adjustments. Specifically, we have addressed the font size of the equations, setting it to 10 for all mathematical formulas.[lines 153-215]

 

Point 4: The authors need to highlight the work in this paper and detail the original work in this study that differs from other existing methods. Unfortunately, the length of the third chapter 'Development' in the manuscript is almost the same as that of the first chapter 'Introduction'.

Response 4: we have revised the 'Introduction' section to provide a clearer and more focused overview of the existing methods in the field. Furthermore, in the 'PI gains design' section, we have added additional simulation results to demonstrate the distinctiveness of our approach compared to other existing methods, the resuls in Figure 4. [lines 238-263]

 

Point 5: Although the author introduced a large number of improvement methods for PLL in the Introduction, they only compared it with adaptive DSC PLL and non adaptive DSC PLL in the experimental section, which cannot highlight the advantages of the method proposed in the manuscript. The author needs to compare with more existing methods (adding no less than 5, as many improvement methods have already been mentioned in introduction).

Response 5: In this study, we have enhanced the existing non-adaptive DSC PLL method by incorporating TD (Transfer Delay) and DSC (Delay Signal Cancellation) operators. By doing so, our objectives are to improve the performance of the PLL. To thoroughly evaluate the effectiveness of our proposed non-adaptive DCI PLL, we have conducted a comparative analysis with both adaptive and non-adaptive DSC PLL methods.

By comparing the proposed PLL with these existing methods, we are able to assess its performance in relation to key parameters such as accuracy, stability, and robustness. This comparative analysis will provide valuable insights into the effectiveness and advantages of our non-adaptive DCI PLL.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

First of all please check the Instructions for Authors from the Journal page and try to respect the template instructions

- maximum number of words for the abstract,

- the figures, tables and equations should be cited in the main text in order and the figures are cited in the text before they appear

-References must be numbered in order of appearance in the text - right now they are presented chaotic

- Please pay attention how you cite the papers, you also have a extra character (& ) .

Then please reread the paper, sometimes you use long phrases and you lose context. See for example the first sentence ("effect on the environment, being sustainable, low cost, and a lot of benefits [1]. " ) or "One of the most popular PLL is based on a synchronous reference frame (SRF), all SRF-PLLs have three main parts: The phase detector (PD), which generates a phase error signal, i.e., a signal that contains the error between real and estimated phases." (here you have at least 2 sentences).

- row 175 capital letter when you start a sentence

- all the abbreviations must be explained in the text when they first appear (for example TD is not explained in the main text)

- milliseconds is ms not Ms,

- you use pu then Pu

- not all terms that appear in the equations are explained and they are not clearly presented, some steps are missing. Correct and verify the equations. 

- present more clearly the Matlab and Simulink results and conclusions 

 

 

 

 

Author Response

Response to the comments of reviewer#3

We express our sincere gratitude and appreciation for the valuable feedback provided by the reviewers. Their insightful comments will undoubtedly enhance the content and overall quality of our paper. With great consideration and attention, we have thoroughly revised our manuscript entitled "Grid-Connected Renewable Energy Sources: A New Approach for Phase-Locked Loop with DC-Offset Removal" according to the reviewers' comments. In response to their feedback, we have prepared a comprehensive list of itemized responses addressing each of their comments.

 

Point 1: First of all please check the Instructions for Authors from the Journal page and try to respect the template instructions

- maximum number of words for the abstract,

- the figures, tables and equations should be cited in the main text in order and the figures are cited in the text before they appear

-References must be numbered in order of appearance in the text - right now they are presented chaotic

- Please pay attention how you cite the papers, you also have a extra character (& ) .

 Response 1: We have carefully reviewed our manuscript and have made the necessary adjustments to address the issues raised.

1. Abstract Word Limit: We have ensured that the abstract conforms to the maximum word limit specified in the journal's guidelines.(200 words) Any excessive content has been appropriately condensed or revised to meet the required length. [lines 8-21]

2. Figures, Tables, and Equations: We have reviewed the placement of figures, tables, and equations in the main text to ensure that they are cited in the correct order. Additionally, we have ensured that figures are referenced in the text prior to their appearance. [Throughout the manuscript]

3. Order of References: We have rearranged the references in the manuscript to adhere to the guideline of numbering them in the order of their appearance in the text. The references are now presented in a sequential and orderly manner. [Throughout the manuscript]

4. Citation Formatting: We have carefully reviewed our citations to ensure accuracy and proper formatting. Any extraneous characters, such as the extra "&" you mentioned, have been removed or corrected as necessary. [lines 398-445]

Point 2: Then please reread the paper, sometimes you use long phrases and you lose context. See for example the first sentence ("effect on the environment, being sustainable, low cost, and a lot of benefits [1]. " ) or "One of the most popular PLL is based on a synchronous reference frame (SRF), all SRF-PLLs have three main parts: The phase detector (PD), which generates a phase error signal, i.e., a signal that contains the error between real and estimated phases." (here you have at least 2 sentences).

Response 2: We have thoroughly reevaluated the paper, paying special attention to sentence structure and clarity, and have made the necessary revisions to address this point. [Throughout the manuscript]

 

Point 3: -row 175 capital letter when you start a sentence

- all the abbreviations must be explained in the text when they first appear (for example TD is not explained in the main text)

- milliseconds is ms not Ms,

- you use pu then Pu.

Response 3:

1. Capital Letter at the Beginning of a Sentence: We have ensured that all sentences in the manuscript begin with a capital letter, including the correction on row 175. [Throughout the manuscript]

2. Explanation of Abbreviations: We have revised the manuscript to ensure that all abbreviations are properly explained when they first appear in the text. This includes providing an explanation for the abbreviation "TD" upon its initial mention [line 57].

3. Unit Formatting: We have corrected the formatting of the unit "milliseconds" to "ms" instead of "Ms". Moreover, we have standardized the abbreviation "pu" and have used lowercase "pu" consistently instead of "Pu". [lines 283-361]

 

Point 4: not all terms that appear in the equations are explained and they are not clearly presented, some steps are missing. Correct and verify the equations.

Response 4: We have ensured that all terms appearing in the equations are now clearly explained in the text. Additionally, we have carefully verified the equations and included any missing steps or explanations to ensure the logical flow of the mathematical derivations [lines 186-215].

 

Point 5: present more clearly the Matlab and Simulink results and conclusions.

Response 5: To enhance the clarity and comprehensiveness of our research, we have included additional simulation results in our study. These supplementary results further strengthen our findings and contribute to a more comprehensive analysis of the simulation outcomes Figures 7 to 12. [lines 286-343].

To ensure the clarity and comprehensibility of our research, we have taken great care in explaining the results in a detailed manner within Table 1. This enables readers to easily interpret and understand the implications of the findings. [line 360]

We have refined the discussion of our conclusions to ensure they are concise, impactful, and accurately reflect the significance of our findings.

We greatly appreciate your valuable input, and we believe that the inclusion of additional simulation results and the thorough explanations provided throughout the manuscript significantly improve the overall quality of our research.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

1. Please carefully check the formula in the manuscript again. For example, Eq 1 has two v_a. And cos in Eq 9 has two different font.
2. Please explain the difference between the two v_a in Figure 1 and why two are needed?
3. “where ^ is the estimated signal” is mentioned in line 177 but redefined in 194.

Minor editing of English language required

Author Response

Response to the comments of reviewer#2

We want to thank the reviewers for their helpful feedback. Their comments and suggestions will improve our paper. We have carefully revised our manuscript titled "Grid-Connected Renewable Energy Sources: A New Approach for Phase-Locked Loop with DC-Offset Removal" based on their suggestions. We have also prepared a detailed list of responses to address each of their comments.

Points:

1. Please carefully check the formula in the manuscript again. For example, Eq 1 has two v_a. And cos in Eq 9 has two different font.
2. Please explain the difference between the two v_a in Figure 1 and why two are needed?
3. “where ^ is the estimated signal” is mentioned in line 177 but redefined in 194.
4. Minor editing of English language required.

 Response 1:

Point 1: thank you for your comment, we checked the formulas throughout the manuscript. In Equation 1, there are two different functions:  and , we mentioned that in lines 154-156 of the new manuscript. " Where  is the alpha signal in the -reference frame,  is the grid-phase,  is the grid-amplitude,  is the grid-frequency, φ is the initial phase angle, and is the DC component in the input voltage ."

Regarding Equation 9, we appreciate your observation, and we rewrote Equation 9 in the correct format, addressing the issue. [line 188]

Point 2: related to Figure 1, we have two different functions:  and , were  is the grid voltage and  is the voltage in the alpha-beta reference frame that we need to generate the orthogonal signal. We have taken this comment into account and have made the necessary updates in our revised manuscript. Specifically, we have mentioned the presence of these two functions in lines 154-156 of the revised manuscript.

Point 3: we have carefully reviewed the manuscript and removed the mention of "^ as the estimated signal" from line 194.

Point 4: we have also addressed the minor editing requirements of the English language, making the necessary revisions to improve the overall quality of the manuscript's language.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript is significantly improved. I have some suggestions and remarks:

- row 10 I suggest to use controllable instead of controllability

- row 28 - this figure should not appear here

- row 32 - to control what??

- reference 23 is at row 136, 24 is at row 145, 21 is at row 150, reference 22 at row 154 . Please try to put them in order - first 21, and then the rest

- equation 9 - try to rewrite it - you have some bold characters

 

Author Response

Response to the comments of reviewer#3

We want to thank the reviewers for their helpful feedback. Their comments and suggestions will improve our paper. We have carefully revised our manuscript titled "Grid-Connected Renewable Energy Sources: A New Approach for Phase-Locked Loop with DC-Offset Removal" based on their suggestions. We have also prepared a detailed list of responses to address each of their comments.

 

Points:

1. Row 10 I suggest to use controllable instead of controllability.
2. Row 28 - this figure should not appear here.
3. Row 32 - to control what??
4. Reference 23 is at row 136, 24 is at row 145, 21 is at row 150, reference 22 at row 154. Please try to put them in order - first 21, and then the rest.
5. Equation 9 - try to rewrite it - you have some bold characters.

Response 1:

Point 1: we sincerely appreciate your suggestion to use "controllable" instead of "controllability" in line 9. We have incorporated this change in our revised manuscript.

Point 2: related to the mentioned figure, we deleted it in the revised manuscript.

Point 3: we have revised the sentence, and we used "controllable" in line 28 as you suggested before.

Point 4: we appreciate your feedback on the order of the references. In the revised manuscript, we have reorganized references 21-24, placing reference 21 first and arranging the remaining references accordingly. The corrected order can be found in lines 85-102 of the main text and 439-446 in the references section.

Point 5: we are grateful for pointing out the issue with Equation 9. We have completely rewritten Equation 9 to ensure clarity. Additionally, we have added a note in the manuscript (lines 188-190) to indicate that the bold lines represent the double frequency terms.

Author Response File: Author Response.pdf