A Precise Current Detection Method Using a Single Shunt and FET Rds(on) of a Low-Voltage Three-Phase Inverter
Round 1
Reviewer 1 Report
Thank you for providing a manuscript regarding A Precise Current Detection Method using a Single Shunt and FET Rds(on) of a Low-Voltage Three-Phase Inverter. A brief introduction to the shunt-resistor, current detection method, followed by an experiment is described well in the paper. I have several comments and suggestions:
> Line 11, "a shunt resister..." --> do you mean "a shunt resistor..." ?
> Figure 9. How Q is defined and obtained? Why you choose that number?
in Figure (a)(b) and (c), Q values are the same as 0.1; However, the Figure caption mentioned that the Q value in (a) is 0.7. Please your comment.
> Please increase the quality of Figures or Graphs.
> The references are out of date. More than 50% of your references are too old. New/current references could be a great source and make a good comparison to your work.
Author Response
Thank you for your sharp and candid review. Your review has given me an opportunity to further upgrade my thesis. Your advice was very sharp and worth considering. I will respond to your review.
> Line 11, "a shunt resister..." --> do you mean "a shunt resistor..." ?
>It's a mistake. Edited.
> Figure 9. How Q is defined and obtained? Why you choose that number?
in Figure (a)(b) and (c), Q values are the same as 0.1; However, the Figure caption mentioned that the Q value in (a) is 0.7. Please your comment.
> The value of Q is defined as the system noise. Usually, it is a principle to accurately reflect and configure in principle, but there is a limit to making an analytical decision because several errors are compounded. Therefore, in this paper, purely experimental values are defined. Figure 9 shows the results for the experimental values for Q and R values. However, there was also a mistake in this part. The order of the pictures and the information in the pictures are incorrect. Since I am presenting my thesis for the first time, there are many mistakes. The information in the picture caption is correct. The thesis has been edited.
> Please increase the quality of Figures or Graphs.
> Edited.
> The references are out of date. More than 50% of your references are too old. New/current references could be a great source and make a good comparison to your work.
> Edited.
Reviewer 2 Report
The paper proposes an improved current detection method for three-phase inverters. The method uses a single shunt resistor and the Rds(on) value (with kalman filter application) to improve the current measurement.
The work proposed by the authors is very interesting and appears to be an interesting proposal for a low-cost measurement method. The experimental results validate the proposed method.
However, the paper is not well written/structured. Some sentences/discussions are not well explained leaving the reader somewhat confused. The work contribution was only clear (in the opinion of this reviewer) in the results discussion. In this way, I suggest rewriting the introduction, leaving the current problems in literature more evident and, obviously, valuing the authors' proposal.
Below I provide some suggestions for improving the paper writing/discussion:
- In line 32 change "considerable" for "Considerable";
- Rearrange the figures so that they appear after being cited in the text. For example, Figure 1 appears in the middle of the introduction when it should only appear in section 2.
- Several sentences cite interchanged figures. For example, in line 85 the authors exchanged Figure 2a for 1a.
- There are two figures 5 in the paper.
- All figures must be cited/explained in the text. For example, Figure 2b is not cited in the text.
- The area of non-detection should be better explained in the paper. For example, what is the difference between band area and star area? What is the minimum (practical) time for the equation 1?
- The quality of the results figures (9-13) could be improved (better resolution).
- I believe the legends (b) and (c) of Figure 8 are interchanged.
- Apparently the harmonic content of the curves in red are superior to the harmonic content of the curves in black in figure 12. However, the results presented in table 4 place the harmonic results very similar. Do the authors have any comments on this?
- The authors quote: "Additionally, an OP-AMP circuit that could measure the drain source voltage of the switch at the bottom of the MOSFET was tested, but it did not add much loss, so it did not have a big impact on the unit cost". I believe that this issue (power losses) is also crucial for the analysis, since equipment is being inserted to improve the measurement. That way, I suggest inserting more information/discussions about it. For example, what is the amount of losses? How many measurements (OP-AMP) were used (one for each leg?).
Author Response
Thank you for your sharp and candid review. It was my first thesis, so there were a lot of mistakes. Please understand the mistake. Your review has given me an opportunity to further upgrade my thesis. Your advice was very sharp and worth considering. We will respond to your review.
Below I provide some suggestions for improving the paper writing/discussion:
- In line 32 change "considerable" for "Considerable";
>Edited.
- Rearrange the figures so that they appear after being cited in the text. For example, Figure 1 appears in the middle of the introduction when it should only appear in section 2.
>Edited. Thank you.
- Several sentences cite interchanged figures. For example, in line 85 the authors exchanged Figure 2a for 1a.
> It's a mistake. Edited.
- There are two figures 5 in the paper.
>It's a mistake. Edited.
- All figures must be cited/explained in the text. For example, Figure 2b is not cited in the text.
> Figure 2b is the contents of inverter configuration using shunt. I tried to explain the inverter composed of shunt, but since it is judged that the content is not important to this content, it has been deleted and modified. Thanks for the point.
- The area of non-detection should be better explained in the paper. For example, what is the difference between band area and star area? What is the minimum (practical) time for the equation 1?
> Thank you for your sharp point. I will briefly explain the area where the current cannot be detected. As mentioned in the question, the undetectable area is divided into two areas: a band area and a star area. Basically, when measuring current using a single shunt in a 2-level low-voltage inverter structure, it is measured at the dc link negative stage using 3 FETs at the bottom among 6 FETs. The timing of sampling the current then measures the current at the time between the switch and the switch as shown in Figure 1. Current sampling is performed twice per PWM cycle. As shown in Figure 1 for each sampling, current sampling is possible twice per PWM cycle. However, if the two-phase PWM command size is similar or the three-phase PWM size is similar, the time to AD current becomes insufficient and accurate sampling is physically impossible. Among them, if the PWM command size of two phases is similar, the time to AD the current of one phase becomes insufficient, and the current detection becomes impossible. As shown in the upper figure in Fig. 4(b), the PWM form comes out and it appears like the gray area in Fig. 4(a), which is usually called a band area. And if the PWM commands of 3 phases are similar as shown in the figure below in Fig. 4(b), the time to AD the current of 2 phases is insufficient, creating a region where current detection is impossible. At this time, it appears as a star-shaped area as shown in Fig. 4(a). This area is called a star area. I will add this part to the thesis.
> Equation 1) varies depending on the experimental situation or MCU type and setting, but the AD time is usually about 2~3us. Tdead (1~2us) It takes about Tsetting(300~600ns)Tadc(200~400us). I will add it to my thesis.
- The quality of the results figures (9-13) could be improved (better resolution).
>Edited.
- I believe the legends (b) and (c) of Figure 8 are interchanged.
>Edited.
- Apparently the harmonic content of the curves in red are superior to the harmonic content of the curves in black in figure 12. However, the results presented in table 4 place the harmonic results very similar. Do the authors have any comments on this?
>
Figure 12 thinks that it is a matter of representation of sampling. In order to express Figure 12, the black current waveform is expressed by re-sampling only important data among 1 million pieces of data. Red is also expressed by re-extracting important data out of 1 million. When comparing actual 1 million pieces of data in the same space, it was difficult to express Figure (12) by covering each other's data. The data shown in Table 4 is the actual analysis of 1 million data. I will send you a picture material that you can refer to.
- The authors quote: "Additionally, an OP-AMP circuit that could measure the drain source voltage of the switch at the bottom of the MOSFET was tested, but it did not add much loss, so it did not have a big impact on the unit cost". I believe that this issue (power losses) is also crucial for the analysis, since equipment is being inserted to improve the measurement. That way, I suggest inserting more information/discussions about it. For example, what is the amount of losses? How many measurements (OP-AMP) were used (one for each leg?).
> The OP-AMP used in this study is ON Semiconductor's MC33202VDR2G, which is a 2-channel OP-AMP and is a device widely used in current research. Based on Mouser (electronic component distribution company), as of 21.11.25 days, when purchasing reel units, it is $0.278 each. As it is a 2-channel OP-AMP, it is used by measuring the voltage of the lower switch of v-phase and w-phase with one component. It is a thesis for constantly controlling the motor in paper . So every moment when the pwm cycle starts, we take a measurement. The pwm cycle used in this paper is 10khz and the sample cycle is 1/10k s. These details have been added to the paper.
Author Response File: 
Author Response.pdf
Reviewer 3 Report
The paper aim in comparing current-sensor methods during an inverter operation monitoring.
The paper deep to be revised addressing properly the following points:
1)The paper lacks a deep comparison with the state of the art. Accordingly, please drastically increase the reference list that is now very poor.
The more paper regarding the same topic the better ( notice that MDPI has no pages limit). For a rough search on the Electronic MDPI papers, a similar and recent paper on current detection on power-electronics circuits is https://doi.org/10.3390/electronics10172143
2) The author should briefly cite/comment/discuss this current paper as well as most of the papers cited by this paper (on Rdson, contactless and Hall-effect sensors)... ..and also add other relevant papers that they may find in the literature. In brief, a deep comparison and description of the state-of-the-art is missing.
3) Then, highlighting differences among wired (Rdson) and contactless (i.e. Hall-effect) current sensors, the author may refer to typical EMI issues and countermeasures (i.e. googling "EMI and current sensors":
https://doi.org/10.1016/j.microrel.2012.10.013 and others from MDPI).
4) This framework of adding much more references is also aimed at adding a comparison table in which are listed the main specs and compared with the state of the art.
This may help to make more clear which is the real improvement with respect to the state-of-art of your work.
5) Figures along the paper are blurry. They do not need to be so big: their size could be reduced.
6) please look at the typos along the paper (i.e. MOFET)
7) The work is somehow interesting as it is based on measurements, but please highlight better which is the scientific novelty in your work (if any). It looks like a project dissertation more than a scientific paper.
Author Response
Thank you for your sharp and candid review. It was my first thesis, so there were a lot of mistakes. Please excuse the mistake. Your review has given me an opportunity to further upgrade my thesis. Your advice was very sharp and worth considering. We will respond to your review.
1)The paper lacks a deep comparison with the state of the art. Accordingly, please drastically increase the reference list that is now very poor.
The more paper regarding the same topic the better ( notice that MDPI has no pages limit). For a rough search on the Electronic MDPI papers, a similar and recent paper on current detection on power-electronics circuits is https://doi.org/10.3390/electronics10172143
>Added and edited.
2) The author should briefly cite/comment/discuss this current paper as well as most of the papers cited by this paper (on Rdson, contactless and Hall-effect sensors)... ..and also add other relevant papers that they may find in the literature. In brief, a deep comparison and description of the state-of-the-art is missing.
>Added and edited.
3) Then, highlighting differences among wired (Rdson) and contactless (i.e. Hall-effect) current sensors, the author may refer to typical EMI issues and countermeasures (i.e. googling "EMI and current sensors":
https://doi.org/10.1016/j.microrel.2012.10.013 and others from MDPI).
>Added and edited.
4) This framework of adding much more references is also aimed at adding a comparison table in which are listed the main specs and compared with the state of the art. This may help to make more clear which is the real improvement with respect to the state-of-art of your work.
>A recent paper has been added. There are few studies similar to this study to indicate a comparison table, so it was difficult to compare, so it was not included. Please forgive me. However, recent papers and latest technologies were described and the necessity of this paper was emphasized.
5) Figures along the paper are blurry. They do not need to be so big: their size could be reduced.
>Edited.
6) please look at the typos along the paper (i.e. MOFET)
>Edited.
7) The work is somehow interesting as it is based on measurements, but please highlight better which is the scientific novelty in your work (if any). It looks like a project dissertation more than a scientific paper.
> What you pointed out is very accurate. The scientific novelty in this study is that Rdson, which occurs when switching on, which is a semiconductor characteristic of the existing MOSFET, is used. I will emphasize this part more. The focus of this thesis is to write a thesis focusing on better performance in the conventional inverter type using the properties of the existing MOSFET.
Thank you very much for being my reviewer.
Round 2
Reviewer 1 Report
Thank you for answering my comments.
Just fast comments, the quality of your figures (both graph and image) need to be improved.
Regards
Author Response
Thank you for responding to my comments.
You need to improve the quality of quick comments, pictures (graphics and images).
greetings
> Your feedback could make my paper better.
Thank you for being my reviewer.
Resubmit with improved image quality.
Reviewer 2 Report
All my questions were addressed by the authors.
Below I provide only minor suggestions for paper improvement:
- The abbreviation CT (line 50) should have its meaning explained in the text.
- I believe the citation "Figure 1a" (line 93) should be Figure 2.
- The non-detection area was explained in the paper. However, two sentences were very similar/repeated in the paper (lines 106 to 108), as follows: "Current sampling is performed twice per PWM cycle. As shown in Figure 1 for each sampling, current sampling is possible twice per PWM cycle." Please review the text.
- On line 139 the Tadc is suggested between 200~400us. As Tmim is between 2~3us (and Tdead = 1~2us and Tsetting = 300~600ns), Tadc shouldn't be 200~400ns?
- Please reposition Figure 7 and equation (2) so that both appear after being cited in the text.
- Figures 10-14 still have a poor quality. In the opinion of this reviewer, these figures could be improved. For example, the authors sent additional figures (in the "Author Response File" with better quality). These figures should be included in the paper final version. By the way, Figure 12 is repeated in the paper (in other words, Figure 12 send by the authors in the "Author Response File" should be renamed for Figure 13.
Author Response
Thanks for your feedback.
Your feedback could improve the paper.
We respond to your review.
- The abbreviation CT (line 50) should explain its meaning in the text.
> Edited.
- I think the citation in "Figure 1a" (line 93) should be Figure 2.
> Edited.
- The non-detection area was described in the paper. However, in the paper, the two sentences (lines 106 to 108) are very similar/repeated as follows: " Examine the text.
> Edited.
- On line 139, Tadc recommends between 200 and 400us. Since Tmim is 2-3us (and Tdead = 1-2us and Tsetting = 300-600ns), shouldn't Tadc be 200-400ns?
>The reviewer is right. Edited.
- Both Figure 7 and Equation (2) are rearranged so that they appear after being cited in the text.
> Edited.
- Figure 10-14 is still of poor quality. These numbers could be improved in the opinion of this reviewer. For example, the author has sent additional drawings in a better quality "Author Response File". This figure should be included in the final version of the paper. By the way, figure 12 is repeated in the paper.
>Improved picture quality. In addition, the last picture was changed to an additional picture and reflected in the final version.
Reviewer 3 Report
The requested higher level of comparison with the state of the art has not been addressed.
Suggested references have not been included.
I suggest getting much more references from those cited here: https://doi.org/10.3390/electronics10172143
The number of references in the paper can be even doubled being the topic well known.
Please read again my former review.
Author Response
Thank you for your review.
As a result, the quality of the paper could be improved.
We respond to your review.
The requested higher level of comparison with the state of the art has not been addressed.
> A comparison table with the latest technology has been added at the end of the paper.
Suggested references have not been included.
I suggest getting much more references from those cited here: https://doi.org/10.3390/electronics10172143
>Added suggested references.
The number of references in the paper can be even doubled being the topic well known.
>Additional references were made to the paper using the suggested references.
Round 3
Reviewer 3 Report
Some prior hints (i.e. in adding valuable papers as 10.1016/j.microrel.2012.10.013 and other papers from MDPI in the reference list as contactless alternative methods) have still not been addressed.
The paper has been improved.
Author Response
Thank you for your review.
Respond to your review.
Some prior hints (i.e. in adding valuable papers as 10.1016/j.microrel.2012.10.013 and other papers from MDPI in the reference list as contactless alternative methods) have still not been addressed.
>Edited.
It is referenced in the reference paper [30].
In addition, other papers listed in MDPI have been added [13-16].
The paper has been improved.
