Anti-Offset High-Voltage Wireless Power Transfer System Based on Many-to-One Topology
, Rui Li 1,2,*, Shuai Yu 1,2,*, Zhengqing Zhang 1,2, Jiuqing Cai 1,2, Weilong Zhang 1,2 and Haijing Sun 1,2
Round 1
Reviewer 1 Report
The paper proposes a high-voltage wireless charging anti-offset WPT topology based on multi-winding transformers for electric vehicles in order to avoid the dead zones with extremely low energy transmission power and ensuring a proper operating frequency for the system.
The following remarks on the paper are recorded:
· - Many typos are observed.
· - A list of symbols and abbreviation should be added.
· - Some paragraphs in the abstract are with similar meaning, try to unify your expressions without repeating (i.e. Lines 6-7 and lines 11-12).
· - How you can optimally identify the number of series inverters, give numerical illustration according to your study.
· - You didn’t consider the copper and iron losses during your design (especially for the four winding transformer you considered).
- What will be the performance if you considered two-primary coils instead of one, and comparing its performance with the designed WPS system.
-
-
Author Response
1、Many typos are observed.
Thank you, the typos will be corrected in the final draft.
2、A list of symbols and abbreviation should be added.
Some abbreviations have shown their full name when they first appeared, for example the WPT. Some other symbols have been described where they appear, for example the M1,M2,,,Mn.
3、Some paragraphs in the abstract are with similar meaning, try to unify your expressions without repeating (i.e. Lines 6-7 and lines 11-12).
Lines 6-7 mainly emphasizes the many-to-one circuit topology proposed in thispaper. And line 11-12 emphasizes the hybrid operating method based on the many-to-one topology. Maybe there are some ambiguity here, and I will correct it in the final draft.
4、How you can optimally identify the number of series inverters, give numerical illustration according to your study.
In the study of the paper, the series inverters and the primary coils is designed one -to -one. This paper mainly studies the anti -offset characteristics of the many-to-one topology. For the best quantity of the series inverters and the optimization of other parameters, I will complete them in my future work.
5、You didn’t consider the copper and iron losses during your design (especially for the four winding transformer you considered).
Yes, the paper mainly studies the anti -offset characteristics of the many-to-one topology, the optimization of other parameters, for example the copper and iron losses, I will complete them in future work.
6、What will be the performance if you considered two-primary coils instead of one, and comparing its performance with the designed WPS system.
According to the conclusions of the paper, the anti -offset characteristics of the WPT system containing two primary coils is obviously greater than that of a system with only one primary coil. In addition, if necessary, in the multiple -to -one topology, the number of secondary coils can be increased by further increasing the number of primary coils.
Reviewer 2 Report
This paper presented the circuit configuration the method to use a few series connected H-bridge inverter to improve the output power capability of multiple transmitter coils and single receiver coil WPT system. The research topic is attractive. However, the paper has not provided the detailed control scheme analysis and the detailed convincing voltage and current simulation and experimental results of the multiple resonant circuits at a few typical displacement-positions to show how the DC load voltage level and the total power efficiency given in Figure 10 and Figure 11 are achieved.
(1) What is the purpose of inserting multiple conventional iron-core transformers between transmitter coils and individual inverter outputs? Since the primary coils of WPT transformer are electrically isolated, they do not require additional electrical insolation transformer.
(2) In section 2.3 equation (12) is given as the equal DC input voltage operation condition for the DC/AC inverters connected in series in DC side. In this condition, the DC input power of all inverters will be same. However, because of the magnetic couplings of the primary WPT transmitter coils to the WPT receiver coil are different, the output AC active power of the primary transmitter coil with weaker mutual coupling to the receiver coil will be much smaller. The power transfer efficiency will be smaller for this branch of WPT circuit. The WPT system efficiency will be negatively affected by this weaker coupling transmitter coil and become smaller as well. This means the total system efficiency cannot reach the power efficiency as shown in Figure 11 in the range when both inverters are operating unless the input DC power of the individual inverters can be controlled to input different input power which can only be achieved by reduced the AC input voltage and AC input current of the primary coil with weaker magnetic coupling.
(3) In section 2.3, the equation (28) for only one transmitting loop working should not be same as the equation (26) with both transmitting loop working.
(4) In section 2. Simulation and verification, the authors need to provide the detailed control scheme for individual inverter control and how the power is distributed among the inverters considering the mutual coupling between the transmitter coils to the receiver coil are different. The simulation results of the output AC voltage waveform and AC current waveforms of individual inverters should be provided to demonstrate the cascaded AC inverters shares the same DC voltage in the high DC voltage bus. The simulation results of AC voltage and AC current waveforms of the multiple WPT transmitter coils and receiver coil should be presented and explained at different displacement position with both transmitting loop working as compared to with only one transmitting loop working.
The simulation results of shown in Figure 6 is not convincing because it does not provide the details of AC and DC signal waveform inside both resonant circuits to show how to get the DC Load voltage value at different displacement position.
The power shared by the two individual inverters is obviously different for the circuit shown in Figure 2, However how to control the power sharing to achieve high efficiency operation of entire WPT system is questionable and needs to be answered by the authors.
(4) In section 4, Prototype making and experimental verification. The results of the AC and DC waveforms of the individual inverters, the transmitter coils and the receiver coil should be provided at different displacement location.
The result shown in Figure 10 is not convincing without providing the WPT resonant circuit voltage and current waveforms at each displacement location.
The result shown in Figure 11 (Two-to-one WPT prototype transmission efficiency) is not convincing if the DC input voltage and DC current for both individual inverters are same as given in equation (12).
Author Response
1、What is the purpose of inserting multiple conventional iron-core transformers between transmitter coils and individual inverter outputs? Since the primary coils of WPT transformer are electrically isolated, they do not require additional electrical insolation transformer.
In this paper, the design of the series inverters is to adapt to the high voltage DC input, the number of series inverters is determined by the voltage of the input source and the rated voltage of each inverter. And in the circuit topology of the paper, the number of the primary coils is determined by the system's anti -offset range. Therefore, the number of series inverters may be different from the number of the primary coils. So, if we want to allocate the power of each series inverter to the primary coils, this multi -winding transformer is necessary.
2、In section 2.3 equation (12) is given as the equal DC input voltage operation condition for the DC/AC inverters connected in series in DC side. In this condition, the DC input power of all inverters will be same. However, because of the magnetic couplings of the primary WPT transmitter coils to the WPT receiver coil are different, the output AC active power of the primary transmitter coil with weaker mutual coupling to the receiver coil will be much smaller. The power transfer efficiency will be smaller for this branch of WPT circuit. The WPT system efficiency will be negatively affected by this weaker coupling transmitter coil and become smaller as well. This means the total system efficiency cannot reach the power efficiency as shown in Figure 11 in the range when both inverters are operating unless the input DC power of the individual inverters can be controlled to input different input power which can only be achieved by reduced the AC input voltage and AC input current of the primary coil with weaker magnetic coupling.
In some case, the magnetic couplings of the primary WPT transmitter coils to the WPT receiver coil are different, and this will cause different magnetic induction in the magnetic core of the multi -winding transformer. But in the circuit topology of this paper, each series inverter is connected to a winding of the multi -winding transformer. At the same time, all windings are shared the same magnetic core. Therefore, in this case, no matter what the value of the magnetic induction is in the magnetic core, the output voltage of each series of inverters is equal, in the next, as long as the duty and phase and phase of each series inverter is the same, their input voltage will be the same. Obviously, the input current of the series inverters is equal, so at this time, their input power is equal. As we can see, the power of each series inverter is always the same, which has nothing to do with the primary coil and secondary coil. This is the reason that I designed a multi -winding transformer in the circuit topology.
3、In section 2.3, the equation (28) for only one transmitting loop working should not be same as the equation (26) with both transmitting loop working.
Thank you, I will correct the equation (28) in the final draft.
4、In section 2. Simulation and verification, the authors need to provide the detailed control scheme for individual inverter control and how the power is distributed among the inverters considering the mutual coupling between the transmitter coils to the receiver coil are different. The simulation results of the output AC voltage waveform and AC current waveforms of individual inverters should be provided to demonstrate the cascaded AC inverters shares the same DC voltage in the high DC voltage bus. The simulation results of AC voltage and AC current waveforms of the multiple WPT transmitter coils and receiver coil should be presented and explained at different displacement position with both transmitting loop working as compared to with only one transmitting loop working.
The simulation results of shown in Figure 6 is not convincing because it does not provide the details of AC and DC signal waveform inside both resonant circuits to show how to get the DC Load voltage value at different displacement position.
The power shared by the two individual inverters is obviously different for the circuit shown in Figure 2, However how to control the power sharing to achieve high efficiency operation of entire WPT system is questionable and needs to be answered by the authors.
In the Simulation and verification, All series inverters work in the same input voltage and duty and phase and phase cycle. According to the analysis of the multi -winding transformer, it can be seen that if the input voltage, duty and phase of the series inverters are the same, their output power is the same.
Since all inverters work in the same state, their DC and AC waveforms are the same. Figure 6 focuses on the waveform of the load voltage.
According to the analysis of the multi -winding transformer in this paper, the output power and working status of all series inverters are the same.
5、In section 4, Prototype making and experimental verification. The results of the AC and DC waveforms of the individual inverters, the transmitter coils and the receiver coil should be provided at different displacement location.
The result shown in Figure 10 is not convincing without providing the WPT resonant circuit voltage and current waveforms at each displacement location.
The result shown in Figure 11 (Two-to-one WPT prototype transmission efficiency) is not convincing if the DC input voltage and DC current for both individual inverters are same as given in equation (12).
According to the analysis of the multi -winding transformer in this paper, the output power and working status of all series inverters are the same. Therefore, this paper focuses on the working status of the load.
Reviewer 3 Report
The paper presents an important application of many-to-one WPT wireless charging anti-offset system for high voltage environment. Following are my observations:
a. In my view block diagram representation of the proposed methodology shall be added. Hence, an acute need is there to elaborate figure2.
b. In section 3.1, authors described method of calculation of mutual inductance, is it a standard methods for calculation or there are other methods. If yes what will be the impact of the calculation on the design.
c. Parameters in Table1 is same for whole simulation process, what of these parameters are varies? Sensitivity analysis should be conducted for evaluation of the robustness of the system.
Author Response
1、In my view block diagram representation of the proposed methodology shall be added. Hence, an acute need is there to elaborate figure2.
Yes, this picture does contain many factors, which is difficult to understand. I will further explain in detail with Figure 2 in the final draft. I added some icons in Figure 2, hoping that this can make Figure 2 clearer.
2、In section 3.1, authors described method of calculation of mutual inductance, is it a standard methods for calculation or there are other methods. If yes what will be the impact of the calculation on the design.
In section 3.1, this method of calculation of mutual inductance is a new algorithm developed by some researchers. This new algorithm can more accurately calculate the mutual inductance between two complex coils. In the paper, the calculation method of the mutual inductance between the coils is very important, which will affect the accuracy of the simulation results. Therefore, this papere uses this more accurate calculation method.
3、Parameters in Table1 is same for whole simulation process, what of these parameters are varies? Sensitivity analysis should be conducted for evaluation of the robustness of the system.
The parameters in Table 1 are a typical parameter close to real physical conditions, which are mainly used for simulation calculations. Table 2 is the real physical parameters of the prototype in this paper. The correctness of this article can be verified through simulation and experiments. This paper mainly studies the anti -offset characteristics of the many-to-one topology, the optimization of other parameters, I will complete the robustness of the system in future work.
Reviewer 4 Report
Authors have presented interesting topic of wireless power transfer technology.
It is suggested to mention necessity of proposed method in the abstract.
Novelty and contribution of article is poor yet to improve and highlight the same .
what is the motivation behind in selection of topic
many number of equations were already available in the existing literature, what is the impact of these equations.
Is it possible to use in real time applications, what cases have been evaluated under real time conditions.
it is suggested to present cost analysis of the proposed concept.
Author Response
Reviewer 4
1、It is suggested to mention necessity of proposed method in the abstract.
For the WPT system, due to the primary coil and secondary coil are naturally difficult to accurate, many scientific researchers regard the anti -offset characteristics of the WPT system as a research hotspot. Especially in some cases where there is no strong constraint on the coil position, such as wireless charging of electric vehicles, anti -offset characteristics are a pain point that requires emergency solution.
2、Novelty and contribution of article is poor yet to improve and highlight the same .
In some cases where there is no strong constraint on the coil position, such as wireless charging of electric vehicles, anti -offset characteristics are a pain point that requires emergency solution. According to the conclusions of the paper, the anti -offset characteristics of the WPT system containing two primary coils is obviously greater than that of a system with only one primary coil. In addition, if necessary, in the multiple -to -one topology, the number of secondary coils can be increased by further increasing the number of primary coils.
3、What is the motivation behind in selection of topic
By improving the anti -offset characteristics of the WPT system, to solve the problem that the primary coils and secondary coils are difficult to accurate during the wireless charging process of electric vehicles.
4、Many number of equations were already available in the existing literature, what is the impact of these equations.
In section 3.1, this equation of calculation of mutual inductance is a new algorithm developed by some researchers. This new algorithm can more accurately calculate the mutual inductance between two complex coils. In the paper, the calculation method of the mutual inductance between the coils is very important, which will affect the accuracy of the simulation results. Therefore, this papere uses the accurate calculation method.
5、Is it possible to use in real time applications, what cases have been evaluated under real time conditions.
Theoretically, the topology proposed in this paper can be applied to reality. The applications of the research results in this paper is my future work.
6、Tt is suggested to present cost analysis of the proposed concept.
The paper mainly studies the anti -offset characteristics of the many-to-one topology, the optimization of other parameters, for example the cost analysis, I will complete them in future work.
Round 2
Reviewer 1 Report
The technical presentation has been improved. I recommend with the acceptance.
Author Response
Thank you.
Reviewer 2 Report
(1) What is the structure of the multi-winding transformer?
Do all the primary and secondary windings of the multiple coil transformer coil are constructed in the same inductor leg? How is the uneven power output of the secondary windings shared equally by the primary windings?
(2) Can the author explain why the efficiency of (26) is better than the efficiency of (28)?
(3) The high total efficiency of the entire wireless power transfer system needs to be validated with simulation or experimental results. The author should show that the transformer coil current of the transmitter winding with misalignment in its receiver coil is smaller to provide evidence that the transmitter winding with weaker magnetic coupling will not drag the total efficiency low.
(4) The Author should provide simulation and experimental results to provide evidence that the DC input power for each inverter is identical in all operating conditions. The author should show that AC and AC voltage waveforms of the primary and secondary side coils of the multiple winding transformers, at least in the location when one transmitter is misaligned with the receiver and the other transmitter is aligned with the receiver coil
Author Response
(1) What is the structure of the multi-winding transformer?
Do all the primary and secondary windings of the multiple coil transformer coil are constructed in the same inductor leg? How is the uneven power output of the secondary windings shared equally by the primary windings?
All windings are winding on the same magnetic core.
Since the magnetic sensing of each place in the magnetic core is always the same, the voltage of each winding is always the same, whether it is the primary winding or the secondary winding, So, the sum of the power of the original side winding is always equal to the sum of the power of the secondary winding. In fact, the power each primary winding is completely unrelated to the power each secondary winding.
Therefore, the power of each primary winding is actually determined by its series inverters. As long as the input voltage and duty cycle of each series inverter are the same, the power of each primary winding is the same.
(2) Can the author explain why the efficiency of (26) is better than the efficiency of (28)?
According to the simulation results of Figure 8 of formulas (26) and (28), it can be seen that the efficiency of the single primary coil system and the two primary coil systems is related to the position of the secondary coil. Some local formulas (26) are more efficient than (28), and there are some other local formulas (28) higher efficiency than (26).
(3) The high total efficiency of the entire wireless power transfer system needs to be validated with simulation or experimental results. The author should show that the transformer coil current of the transmitter winding with misalignment in its receiver coil is smaller to provide evidence that the transmitter winding with weaker magnetic coupling will not drag the total efficiency low.
In the theoretical analysis, this article regards the multi -winding transformer as an ideal transformer. And in the experimental verification, in order to reduce the effects of multi -winding transformers on the experimental results, the author selected a less leaky magnetic core, and each winding was carefully produced. In the future research, the author will verify the problem through simulation and experiments.
(4) The Author should provide simulation and experimental results to provide evidence that the DC input power for each inverter is identical in all operating conditions. The author should show that AC and AC voltage waveforms of the primary and secondary side coils of the multiple winding transformers, at least in the location when one transmitter is misaligned with the receiver and the other transmitter is aligned with the receiver coil.
From the theoretical analysis, we can see that as long as the duty cycle of each series inverter is consistent, the DC input and the AC output waveform of each series inverter is consisten, and the waveforms of this DC and AC can easily be verified by simulation and experiments.
During the research process, the authors focuses on the output voltage and the anti-offset characteristic of the system. Therefore, the authors have not fully displayed some basic parameters in the paper. In the future research process, the authors will fully consider the selection of waveforms to meet the attention of different readers.
Reviewer 3 Report
Accept
Author Response
Thank you.
Reviewer 4 Report
Authors have answered for all comments raised by the reviewer. Now its in a good shape to accept the article.
Author Response
Thank you.
Round 3
Reviewer 2 Report
It is not convincing that the current of the transmitter coil with weaker magnetic coupling can be limited to a smaller value without additional control in the inverters to ensure the system efficiency is decided by the transmitter coil with stronger magnetic coupling.
Even though the current and voltage of the DC load are same for both power transmission path, The magnetic path with weaker coupling has much lower impedance. If the multi-winding transformer has same input and output voltage (ideal transformer), the secondary side current in the weaker coupling path will be larger because of the lower impedance. This means the efficiency will be lower for the weakly coupled transmitter coils. The total efficiency thus will also drop even another transmitter coil can provide high efficiency.
If the author does not agree with the above analysis, they need to provide the simulation or experimental results to show the weakly coupled transmitter does not take input larger current.
Author Response
The simulation models, simulation results and analysis are in the appendix，please check it.
Author Response File: 
Author Response.pdf
