機能創造理工学科 宮武研究室のYu Meng Lanさん(理工学研究科理工学専攻グリーンサイエンス・エンジニアリング領域博士後期課程1年)が国際学会「24th International Conference on Electrical Engineering (ICEE 2018)」 においてBest Oral Presentation Awardを受賞しました．そこでLanさんに受賞された業績についてご紹介いただきました．

題目：Core Design of EE-shaped Dynamic Wireless Power Transfer Device with Optimal Circuit Topology for Railway Vehicles (鉄道車両用に最適化された回路構成を持つ移動無線給電デバイスのE-E形コアの設計法)

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1. Under what kind of background you chose the topic of your research?

Compared with shipping, aircraft and road transport, the railway has the advantages of low carbon emission, strong transport capacity, and high safety factor. As the power supply method of the electrified railway, the third rail power came out in 1879 and the overhead line power published in 1881 are applied worldwide nowadays. However, these two modes of power supply are also facing the shortcomings of large work amount and frequent maintenance. At the same time, the exposed power supply cable makes human and other things near the track at risk of electric shock. Hence, a new form of power supply is on the way.

2. What kind of power supply do you study?

I’m studying dynamic wireless transfer system for the high-power application. This technique is achieved by converting the energy in the form of electric-magnetic-electric according to the Ampère’s circuital law and Faraday’s law of induction. Thanks to the magnetic field, there is no need for any contact between the power line and the pick-up. In other words, there isn’t any mechanical loss during the operation so that the frequency and costs of maintenance are going to stay at a shallow level. Also, all the cables are sealed by isolating materials
that the chance of electric shock is theoretically eliminated. Based on the working state, the WPT (Wireless Power Transfer) system can be divided into dynamic and static modes. Comparing with the static WPT, the dynamic WPT can expand the duration of operation and bring more flexibility for scheduling even though it requires a longer ransmission path. Of course, both the static and the dynamic modes is facing the weakness of lower efficiency than the existing power supply system.

3. How about introducing more about your research?

I picked the EE-shaped model as the structure for dynamic WPT system, which is similar to a transformer with a considerably large air gap as shown in Figure 1. The structure is symmetric along the plane where the central axis lies, and the magnetic field shape passing by the receiver hardly changes with the movement of its driving irection. This structure also has a reasonable endurance of lateral misalignment because of the existing of three magnetic poles. My study is mainly divided into two parts. One is the reactive power compensation topology to minimize the power converter with keeping high power factor. The other is core design with ferromagnetic materials for balancing the volume and performance. In the paper presented on ICEE 2018, the mathematical derivation of various reactive compensation topologies was carried out, and the relationship between the core volume and the magnetic field concentration capacity was theoretically analyzed based on the electromagnetic theorems. Finally, the conclusions obtained in the theoretical analysis were verified by using the Finite Element Method simulation.

4. Is there any suggestion for making a presentation?

Unlike writing a paper, the content for presenting needs to be more selective rather than exhaustive. First, the ain content of the research should be fully displayed within the specified time. At the same time, the core content of the research is supposed to be elaborated in detail. What I did was to present the keywords and charts on the
slides and to explain the content of each part orally according to its importance. This enriches the presentation by ensuring the readability of each slide. Speaking in a language other than your own can be very stressful. How about stopping for a moment to take a sip of water and reorder your words when you realize you’re too tense to express yourself fluently. For someone who is lack of confidence in language ability just like me, it might be better trying to choose words commonly used rather than those that are too difficult to pronounce. Body language is also helpful in the case of explaining charts or figures, and it makes you look less nervous.

5. How do you think about the future of the WPT system?

Although there is growing number of new rail transportation such as maglev train and vacuum capsule, the dynamic WPT system is more suitable and research valued for the developed railway web all over the world due to the advantage of combining with the present railway system. Nowadays, some research institutes have developed high-power WPT equipment for railway with certain practicability. However, due to the influence of large air gap and expensive ferrite core, it still has not very good application value. The next step of my research will focus on lighter core and better cable layout.

EE-shaped Dynamic WPT and Single phase Transformer