Receiving-End Voltage Compensation Method with NPC-Inverter-Based Active Power Line Conditioner in Three-Phase Four-Wire Distribution Feeder
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe paper presents the study of a receiving-end voltage compensation method employing a phase-1 specific reactive power control strategy with a neutral point clamped (NPC) inverter in a three-phase 2
four-wire distribution system. While the paper addresses an interesting problem, several details need attention to enhance quality.
The introduction section lacks references, and some sentences can not be supported. In the same section, some equations use diagrams to support them, but the variables are not in the diagrams. Additionally, some acronyms must be defined.
In the second section, the authors say, "The nonlinear load consists of a diode rectifier with capacitor input filter and resistor." Why? Are there other forms? How were the values of Table 1 defined?
The first sentence of the first and second paragraphs is redundant in the third section. The authors must pay attention when citing mathematical functions in the paragraphs; they do not have the correct format (line 142, for example). In line 155, the authors mention, "A moving average low-pass filter (MALPF) is used to extract the DC components." why was it used? They also used PI controllers to control the output currents but provided no information about the PI parameters or implementation design.
The results section is very interesting, but several details must be clarified. For example, how were the parameters of Table 3 defined?. Also, a comparative table to highlight the results obtained (tables 4, 5, and 6) must be added to the section. Also, figures 7 and 8 must be modified to highlight the contribution of the results.
Finally, The conclusions should be extended with more future work, offering hope and optimism for the potential advancements in this field.
Please ensure that typographical and grammatical errors are corrected, for example, in line 145.
Author Response
Thank you very much for your review of our paper. The authors have revised our paper with the reviewer’s comments and resubmitted our paper. Please review our revised manuscript.
Comments 1: The introduction section lacks references, and some sentences can not be supported. In the same section, some equations use diagrams to support them, but the variables are not in the diagrams. Additionally, some acronyms must be defined.
Response 1: Thank you for pointing this out. We added 12 papers in the Introduction. The variables in Figure 1 have been added in the revised paper. Moreover, some acronyms have been added in the revised paper, such as “Thyristor-switched capacitor (TSC)”.
Comments 2: In the second section, the authors say, "The nonlinear load consists of a diode rectifier with capacitor input filter and resistor." Why? Are there other forms? How were the values of Table 1 defined?
Response 2: As you well known, many household appliances and industrial equipment have AC/DC converter such as diode rectifier with capacitor input filter and thyristor-controlled rectifier. We added the Reference [2] for harmonic sources in power system.
The values of Table 1 were defined to evaluate at around the rated capacity for verification of compensation effects by the proposed method. We added the description for the values of Table 1 at lines 120-126 in the revised paper as follows:
“Table 1 shows the numerical values for the reduced model used in the experiment, which simulates the power distribution system in South Korea. It is necessary to evaluate at around the rated capacity for verification of compensation effects. In addition, according to reference [35], for capacities of 100 kVA or less, the equipment imbalance ratio is specified as 30% or less. Therefore, in this study, when the phase a load is 1.0 pu, the phase b and c loads are designed to be 0.8 pu and 0.75 pu, respectively, so that the equipment imbalance ratio is within 30%.”,
Comments 3: The first sentence of the first and second paragraphs is redundant in the third section. The authors must pay attention when citing mathematical functions in the paragraphs; they do not have the correct format (line 142, for example). In line 155, the authors mention, "A moving average low-pass filter (MALPF) is used to extract the DC components." why was it used? They also used PI controllers to control the output currents but provided no information about the PI parameters or implementation design.
Response 3: Thank you for your deep reading. The authors have decided to reflect your opinion. Lines 125-126 in the original paper,
“The control circuit depicted in Figure 4 illustrates the proposed strategy for phase-
specific reactive power control for regulating the receiving-end voltage.”,
has been changed to line 157
“In Figure 4, ”.
in Page 5.
Thank you for pointing this out. The authors have made some corrections to the way mathematical functions are cited.
Again, thank you very much for your appropriate comment. Considering your comment, “A moving average low-pass filter (MALPF) is used to extract the AC components”, in line 185, in Page 7, has been corrected to
“A moving average low-pass filter (MALPF) is used to extract the AC components in (9) because the instantaneous power that flows into and out of the APLC is all even-order components, and by adopting MALPF, which uses a moving average of half a cycle as a low-pass filter, it is possible to remove the even-order component, 2w component.”,
lines 174-177, in the revised paper.
In the revised paper, the authors added the PI parameters in the Table 4.
Comments 4: The results section is very interesting, but several details must be clarified. For example, how were the parameters of Table 3 defined? Also, a comparative table to highlight the results obtained (tables 4, 5, and 6) must be added to the section. Also, figures 7 and 8 must be modified to highlight the contribution of the results. Finally, The conclusions should be extended with more future work, offering hope and optimism for the potential advancements in this field.
Response 4: Thank you for pointing this out. The authors added how to decide the parameters of Table 3 in the revised paper as follows:
“In Table3 , the cut-off frequency is designed to be 5.19 kHz. The reference DC-capacitor voltage V*DC is 400Vdc because the line-to-line voltages on the source side are 200 Vrms. The CDC is decided to smooth the DC voltage sufficiently.”
The comparative table for Tables 4 and 6 in the original paper has been added as Table** in the revised paper. Table 5 in the original paper is another simulation condition. We didn’t add the comparative table for this table.
The DC-capacitor voltage waveforms of Figures 7 and 8 have been magnified around mean voltage for emphasizing the contribution of the results.
In addition, to show our future plan, lines 340-342, in Page 13,
“In the future, we will try to improve compensation performance for receiving-end voltage and harmonic current compensation by increasing the number of levels of NPC inverter.”,
has been added.
Comments 5: Please ensure that typographical and grammatical errors are corrected, for example, in line 145.
Response 5: We apologize many typos in the original paper. We have corrected the incorrect grammar and words in the revised paper.
Reviewer 2 Report
Comments and Suggestions for AuthorsReviewer Report
Article Title: Receiving-End Voltage Compensation Method with NPC-Inverter based Active Power Line Conditioner in Three-phase Four-Wire Distribution Feeder
Authors: Marek Pavlík, Matej Bereš, František Kurimský
Decision: Accept after minor revisions. The paper presents valuable contributions to the field, but would benefit from minor revisions in terms of references, presentation clarity, and language corrections.
Overall review
The manuscript presents a method for compensating receiving-end voltage in three-phase four-wire distribution systems (3P4WDF) using an NPC-inverter based Active Power Line Conditioner (APLC). The proposed approach, based on phase-specific reactive power control, is both relevant and technically sound. The method addresses critical issues such as unbalanced voltages and neutral-line currents, and the simulation results demonstrate the effectiveness of the proposed control strategy.
Review and Suggested Improvements
· State-of-the-art coverage: The literature review could be improved adding more references on key topics such as recent advances in voltage compensation methods, control strategies for NPC inverters, and handling neutral-line current in 3P4WDF systems. This would give better context to the novelty of the work. The number of references does not show a thorough review of the sate-of-the-art. Please, consider checking recent publications that could be analyzed.
· Methodology clarity: The methodology is generally well-explained, but a more in-depth explanation in some areas could be interesting. Specifically, the control strategy for reactive power compensation by phase should be contrasted with alternative methods in the literature and some comments would be appreciated here.
· Presentation quality: There are minor language issues, including typographical errors, that need correction to improve readability. I found some mistakes, listed here:
- "in particulary" instead of "in particular" in line 21
- "is is explained" instead of "is explained" in line 25
- "ther are defined" instead of "there are defined" in line 131​.
- "ractive currents" instead of "reactive currents" in line 157​.
- "performes" instead of "performs" in line 164.
- "Threfore" instead of "Therefore" in line 194.
- "diffedrence" instead of "difference" in line 248​.
- "Actibe Current Control" instead of "Active Current Control" in ref. 11​.
- "are far from unity DPF" could be changed by "are far from a unity DPF" (suggestion)​.
Although these are not major corrections to be made, there are quite a few mistakes, so the manuscripts should be thoroughly reviewed.
Suggestions
· References: It would be great to add more citations, particularly on alternative voltage compensation techniques and control strategies.
· Clarity in simulations: Consider providing more detailed descriptions of the simulation setup and conditions, especially any assumptions or limitations that may affect the generalizability of the results.
· Typographical and language edits: A few minor errors and awkward phrasing were noted. A light English editing pass is recommended to enhance the clarity of the text.
Conclusion
In conclusion, I would like to congratulate the authors for their valuable contribution to the field of power distribution systems. That being said, there are some minor typographical errors and small areas where the clarity of the methodology and references could be improved. With these minor corrections, the paper will be in good shape for publication. Keep up the great work!
Comments on the Quality of English LanguageSome minor typos were found and some sentences sound a little strange for native speakers.
A list of mistakes:
- "in particulary" instead of "in particular" in line 21
- "is is explained" instead of "is explained" in line 25
- "ther are defined" instead of "there are defined" in line 131​.
- "ractive currents" instead of "reactive currents" in line 157​.
- "performes" instead of "performs" in line 164.
- "Threfore" instead of "Therefore" in line 194.
- "diffedrence" instead of "difference" in line 248​.
- "Actibe Current Control" instead of "Active Current Control" in ref. 11​.
Author Response
Thank you very much for your review of our paper. The authors have revised our paper with the reviewer’s comments and resubmitted our paper. Please review our revised manuscript.
Comments 1: The literature review could be improved adding more references on key topics such as recent advances in voltage compensation methods, control strategies for NPC inverters, and handling neutral-line current in 3P4WDF systems. This would give better context to the novelty of the work. The number of references does not show a thorough review of the sate-of-the-art. Please, consider checking recent publications that could be analyzed.
Response 1: Thank you for your deep reading. We added 12 papers in the Introduction.
To explain in more detail that there are no reports yet on the voltage compensation method, lines 80-84, in Page 3,
“In addition, although research has been carried out on stable operation under unbalanced load conditions and during system faults, there are no reports to date on research into the control unbalanced voltages in a balanced manner [31,32]. To the best of our knowledge, a method for suppressing the neutral-line currents under unbalanced source current conditions has not yet been reported.”,
has been added.
To explain in more detail about NPC inverter, lines 148-151, in Page 5,
“NPC inverters, which are three-level inverters, can reduce the withstand voltage of the switching element compared to two-level inverters. In addition, since the switching noise is also reduced, the size of the LC filter can be reduced, and the switching frequency can be increased, enabling high-efficiency power conversion [36-38].”,
has been added.
Comments 2: The methodology is generally well explained, but a more in-depth explanation in some areas could be interesting. Specifically, the control strategy for reactive power compensation by phase should be contrasted with alternative methods in the literature and some comments would be appreciated here.
Response 2: Thank you for your valuable comment. In [24], the unified power quality conditioner which has series and parallel PWM converters has been proposed. In this method, the series PWM converter compensates the unbalanced voltage and parallel PWM converter compensates the unbalanced and distorted currents. However, the circuit configuration is complex. On the other hand, our proposed method is used only parallel connected NPC inverter. Thus, the circuit configuration is simple.
Comments 3: There are minor language issues, including typographical errors, that need correction to improve readability. I found some mistakes, listed here:
- "in particulary" instead of "in particular" in line 21
- "is is explained" instead of "is explained" in line 25
- "ther are defined" instead of "there are defined" in line 131 .
- "ractive currents" instead of "reactive currents" in line 157.
- "performes" instead of "performs" in line 164.
- "Threfore" instead of "Therefore" in line 194.
- "diffedrence" instead of "difference" in line 248.
- "Actibe Current Control" instead of "Active Current Control" in ref. 11.
- "are far from unity DPF" could be changed by "are far from a unity DPF" (suggestion).
Although these are not major corrections to be made, there are quite a few mistakes, so the manuscripts should be thoroughly reviewed.
Response 3: The authors would like to express their gratitude to your careful review. We have revised our paper carefully.
Comments 4: Clarity in simulations: Consider providing more detailed descriptions of the simulation setup and conditions, especially any assumptions or limitations that may affect the generalizability of the results.
Response 4: Thank you for your valuable comment. We added the description how to decide the parameters and PI gains of PI controller in the Table 4.
“Table 1 shows the numerical values for the reduced model used in the experiment, which simulates the power distribution system in South Korea. It is necessary to evaluate at around the rated capacity for verification of compensation effects. In addition, according to reference [35], for capacities of 100 kVA or less, the equipment imbalance ratio is specified as 30% or less. Therefore, in this study, when the phase a load is 1.0 pu, the phase b and c loads are designed to be 0.8 pu and 0.75 pu, respectively, so that the equipment imbalance ratio is within 30%.”,
has been added.
The authors added how to decide the parameters of Table 3 in the revised paper as follows:
“In Table3 , the cut-off frequency is designed to be 5.19 kHz. The reference DC-capacitor voltage V*DC is 400Vdc because the line-to-line voltages on the source side are 200 Vrms. The CDC is decided to smooth the DC voltage sufficiently.”
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsAll comments have been addressed satisfactorily; the paper is ready for acceptance.
Author Response
Thank you very much for your review of our paper.
