A Design Methodology for EV-WPT Systems to Resonate at Arbitrary Given Bands

Round 1

Reviewer 1 Report

The paper presents an interesting generalization of a design methodology to design multi-coils WPT systems. However, in the present form, the paper appears weak in key parts. In the following, more precise comments.

In the Introduction:

• The general motivation behind the work is the sentence here reported: “So far, there is no systematic design methods for EV-WPT system to resonant at a given band, which is a bottleneck problem that need to be solved.”

To the best of my knowledge, this is true, but I think it is important to mention the work

Wang, C. S., Covic, G. A., & Stielau, O. H. (2004). Power transfer capability and bifurcation phenomena of loosely coupled inductive power transfer systems. IEEE transactions on industrial electronics, 51(1), 148-157.

probably the first which proposed a criterion to avoid the frequency splitting phenomenon. By avoiding the splitting, it is possible to use a variable-frequency supply technique (the one mentioned in the manuscript as “frequency tracking”) to maintain a high-efficiency level.

An interesting analysis and comparison among the effects of mistuning and fixed or variable frequency supply techniques is available in the work:

Cirimele, V., Torchio, R., Villa, J. L., Freschi, F., Alotto, P., Codecasa, L., & Di Rienzo, L. (2020). Uncertainty quantification for SAE J2954 compliant static wireless charge components. IEEE Access, 8, 171489-171501.

• The term “design indexes” should be better defined.

In Sec. 2.1

• The concept of bands and multi-bands should be presented before all other items
• As it is defined, the concept of center frequency is not clear and unambiguous. Is this definition still generally valid in presence of multiple resonance frequencies?

In Sec. 2.2

In general, this section would require a part where the basic concepts are better defined and clarified: the definitions provided in sec. 2.1 are not sufficient for this purpose.

• Probably the authors wrote m (subscript) instead of n as the related figure 1 does not contain any subscript m
• Please, note that omega is not a frequency but an angular frequency
• The part from row 142 to row 146 should be rephrased because it appears really difficult to follow
• In row 147 “can be” is repeated two times
• It should be welcome to add a reference to support the statement “According to the physical properties of a practical system, the real part of eigenvalue lambda q is a negative number with a small absolute value.”

In Sec. 3/4

As indicated by the title, this section should provide the steps that have to be followed to design a multi-coil WPT system. Actually, this section presents a weak point exactly in the steps list: in order to calculate the inductance matrix L, at least shape and number of turns of the coils should be known however information on the design of the coils in these terms is completely missing.
In sec. 4 the values of self-inductance are assumed a priori without a precise explanation, so it is difficult for the reader to understand how to choose and obtain these parameters in the design phase. Moreover, it seems that these parameters could be designed independently of information about source voltage and load characteristics.

 

 

 

Author Response

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Reviewer 2 Report

Manuscript No.: energies-1497985

Manuscript Title: A design methodology for EV-WPT systems to resonate at arbitrary given bands

Dear Editor of Energies

In this paper, the design methodology for EV-WPT systems to resonate at arbitrarily given bands was presented. The paper is well-organized. The topic is interesting in this field. However, the paper needs more improvement before it should be accepted as follows:

1. Add some qualitative results to the abstract in terms of output power at k1, k2, and k3.
2. The abstract should be re-written to include: background, problem statement, objectives, methodology, significant result, and conclusion.
3. The contribution of the paper should be highlighted in the introduction section.
4. In page 3, lines 112-116, the Rpm, Cm, um, vm, and Rml are not found in Fig. 1.
5. In page 3, lines 117-119, the sentence “When vm ≠ 0 and RLm = 0, the m-th circuit is regarded as a transmitter. Conversely, when vm = 0 and RLm ≠ 0, the m-th circuit serves as a receiver. When both of them are equal to zero (vm = 0 and RLm = 0), the m-th circuit is a repeater.” This can be presented as graphs to be clearer.
6. In page 3, line 122, Kirchhoff's voltage law (KVL) states that in any complete loop within a circuit, the sum of all voltages across components that supply electrical energy must equal the sum of all voltages across the other components in the same loop. Therefore, is there any electrical loop available in Fig. 1 between coils? L1 radiated an electromagnetic field through the air gap to induce by L2, and L2 radiated an electromagnetic field through the air gap to induce by L3 and so on for the rest of the coils.
   I doubt that equation (1) is correct unless the authors provide scientific evidence for their claim.
7. Some parameters in equations are not defined.
8. In page 11 line 316, the single-band system, dual-band system, and tri-band system should be clarified. What is meant by them?
9. More details should be presented about the values in Equation 36. How they are obtained.
10. In Figure 4, the intermediate coil must be inserted in the figure.
11. What is the AWG standard of the three coils presented in Table II?
12. In page 12, line 344, the transfer distance d12 = 0.29 m and d23 = 0.16 m should be indicated in Fig. 3.
13. Eq. (26) is not related to M12, M23, and M13 as the author mentioned in page 12, line 347. I think the authors mean Eq. (36).
14. In page 13, lines 335 and 363 Eq. (26) should be Eq. (36).
15. In page 13, line 359, the sentence “In the first set of experiments” must be corrected to “In the third set of experiments”.
16. Based on Figure 5, we can deduce that the single-band achieves better performance than dual- and three-bands. So, the authors should be discussed which one is better in terms of other parameters such as transfer efficiency and transfer distance. I couldn’t find any reason why the authors go further with the analysis of dual- and three-bands where the single-band achieves high performance in terms of output power.
17. Some references are out of date such as refs [1] and [2]. The authors are required to look for new references for 2019, 2020, and 2021.

Best regards
Reviewer

 

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors considerably improved the quality of the work.
Generally, a final check of language and typos is needed, but the paper can be considered for publication.

Some final comments are in the following.

With respect to the answer given by the authors in the previous round of review, I want to emphasize that, although the standards for electric vehicle charging applications indicate a nominal working frequency (i.e. 85 kHz), a range of variation is still provided precisely to allow the use of frequency tracking techniques.

With reference to the answer “Since the purpose of this manuscript is to design lumped parameters, not the geometric parameters, there is no in-depth discussion on coil geometric parameters, voltage and load characteristic.” I understood and agreed with the authors’ point of view. However, I think that this should be more clearly made explicit in the text (better to state it also in the introduction).

Author Response

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Reviewer 2 Report

My previous concerns have been well addressed. I have no further comments. The paper can be accepted in the current form. 

Author Response

Thanks for your comments.