Second Harmonic Current Reduction Control for Two-Stage Inverter with a New Inductor Current Feedback Path
Round 1
Reviewer 1 Report
This paper is well written and the topic is described in detail. My comments are given as follows:
1. Is it possible to apply the proposed control system in the case of utilizing a boost DC/DC converter or a buck-boost DC/DC converter?
2. In this study single-phase inverter is considered. Did you consider three-phase intverter?
3. Is it possible to utilize the proposed control system in the case when the buck DC/DC converter is supplied by a photovoltaic source or fuel cells?
4. Please update the list of references with current references of a more recent date.
5. Please quantify the contributions in the conclusion. Provide some numbers.
Author Response
Reviewer#1, Comment 1: Is it possible to apply the proposed control system in the case of utilizing a boost DC/DC converter or a buck-boost DC/DC converter?
Author response: Thanks for the reviewer’s comment. The control method is presented based on the buck DC/DC converter. Due to the different system configurations, the proposed control method can’t be directly used to the boost DC/DC converter or the buck-boost DC/DC converter.
Reviewer#1, Comment 2: In this study single-phase inverter is considered. Did you consider three-phase inverter?
Author response: Thanks for the reviewer’s comment. The second harmonic current (SHC) is an important issue in the two-stage single-phase inverter. For the two-stage three-phase inverter, the SHC is also generated in the front-stage DC-DC converter when the load or the grid voltage is unbalanced. In this case, the three-phase inverter can be considered as three single-phase inverters, thus, the proposed control scheme in this paper can be used to the unbalanced two-stage three-phase inverter.
Reviewer#1, Comment 3: Is it possible to utilize the proposed control system in the case when the buck DC/DC converter is supplied by a photovoltaic source or fuel cells?
Author response: Thanks for the reviewer’s comment. As described in the introduction, the SHC control is important for the two-stage single-phase inverter with a wide DC input voltage range. The photovoltaic source and fuel cells are both the DC power supply with a wide voltage range, thus, when the buck DC/DC converter is supplied by a photovoltaic source or fuel cells, the proposed control system can be directly used.
Reviewer#1, Comment 4: Please update the list of references with current references of a more recent date.
Author response: Thanks for the reviewer’s comment.
According to the comment, we update the references as below.
[1] S. Kan, X. Ruan, X. Huang, H. Dang. Second harmonic current reduction for flying capacitor clamped boost three-level converter in photovoltaic grid-connected inverter. IEEE Trans. Power Electron. 2021, 36, 1669-1679.
[2] H. Zhou, L. He, Z. Lin. Low frequency current ripple suppression for two-stage single-phase inverter based on impedance editing. IEEE Trans. Ind. Electron. 2022, 69, 13417-13427.
[3] F. Liu, X. R, X. Huang, Y. Qiu, Y. Jiang. Control scheme for reducing second harmonic current in AC-DC-AC converter system. IEEE Trans. Power Electron. 2022, 37, 2593-2604.
[4] S. Kan, X. Ruan, H. Dang, L. Zhang, X. Huang. Second harmonic current reduction in front-end DC−DC converter for two-stage single-phase photovoltaic grid-connected inverter. IEEE Trans. Power Electron. 2019, 34, 6399-6410.
[5] L. Zhang, X. Ruan. Control schemes for reducing second harmonic current in two-stage single-phase converter: an overview from DC-bus port-impedance characteristics. IEEE Trans. Power Electron. 2019, 34, 10341-10358.
Reviewer#1, Comment 5: Please quantify the contributions in the conclusion. Provide some numbers.
Author response: Thanks for the reviewer’s comment. According to the comment, we update the manuscript by adding the contributions in the conclusion as below.
“The SHC proportion can be reduced to about 4.7% in the proposed NICFPS, while 33.2% in the scheme I and 11.1% in the scheme II. The undershoot and settling time can be reduced close to 50 V and 50 ms in the proposed NICFPS, while 61 V and 230 ms in the scheme I.”
Reviewer 2 Report
This paper presents the SHC reduction for the two-stage inverter with the front-end buck converter. To reduce the SHC, the virtual resistance and the BPF in a new feedback path is introduced to increase the output impedance at 2fo, and the control method of the NICFPS is proposed after simplifying the feedback function. Importance of the work should be pointed out through giving some specific results. The structure is balanced. The remarks made after each simulation and experimental results could be better synthesized in conclusions. In the conclusions in necessary to appear more emphasized the effects of different construction features upon the systems functioning.
Author Response
Reviewer#2, Comment: This paper presents the SHC reduction for the two-stage inverter with the front-end buck converter. To reduce the SHC, the virtual resistance and the BPF in a new feedback path is introduced to increase the output impedance at 2fo, and the control method of the NICFPS is proposed after simplifying the feedback function. Importance of the work should be pointed out through giving some specific results. The structure is balanced. The remarks made after each simulation and experimental results could be better synthesized in conclusions. In the conclusions in necessary to appear more emphasized the effects of different construction features upon the systems functioning.
Author response: Thanks for the reviewer’s comment. According to the comment, we update the remarks after each simulation and experimental results, and add the effects of different construction in the conclusion. The detailed descriptions are as below.
“It is obvious that the proposed NICFPS has the best ability to suppress the SHC, and the reason is that the scheme has the highest output impedance at 2fo, which can be seen from Figure 11.”
“This is because the scheme I has the highest output impedance almost at all frequencies, but the proposed NICFPS and the scheme II can reduce the output impedance at the frequencies except for 2fo, and the characteristic comparison of the output impedance about the three schemes can be seen from Figure 11.”
“It is thus clear that the proposed NICFPS has the best effect on the SHC reduction, because the highest output impedance at 2fo can be obtained for the scheme as shown in Figure 11.”
“It is obvious that the NICFPS and the scheme II have the better dynamic performance. The reason is that the proposed NICFPS and the scheme II can reduce the output impedance at the frequencies except for 2fo, which can be seen from Figure 11.”
“The SHC proportion can be reduced to about 4.7% in the proposed NICFPS, while 33.2% in the scheme I and 11.1% in the scheme II. The undershoot and settling time can be reduced close to 50 V and 50 ms in the proposed NICFPS, while 61 V and 230 ms in the scheme I.”
Reviewer 3 Report
Please, find the attached PDF file.
Comments for author File: 
Comments.pdf
Author Response
Reviewer#3, Comment: The Authors presents a new approach to reduce the second harmonic current component in a DC-DC converter. The paper is well organized and well written and the proposed method is interesting. Moreover, each section is adequately discussed and presented. However, I suggest the authors to address the following points:
- I suggest the Authors to revise the whole document in order to check the typos.
- Enlarge the Bode diagrams because they could by too small for some readers.
To conclude, I suggest to publish the article after minor revision.
Author response: Thanks for the reviewer’s comment.
According to the comment, we revise the whole document, and enlarge the Bode diagrams, including Figure 3, Figure 4, Figure 8, Figure 9, and Figure 11.
