Y계 초전도 무선전력전송 시스템의 효율 개선을 위한 최적 설계

Abstract

The use of portable electronic devices such as smart phones and tablet PCs is abruptly increasing these days. In addition, free information exchange became possible via mobile communication networks, wireless LAN, etc. With the development of electronic devices, communication systems have been developing as well. Despite such development, the power supply for the electronic devices still relies on wired systems. The wired power supply has many limitations in terms of place and mobility. The limited and degraded battery capacity of mobile devices is also requiring the need of the study on the wireless power supply and chargeable wireless power transmission technology. The wireless power transfer (WPT) uses antenna for wireless power transmission. Although the technology was ignored in the time when it was first suggested by Nikola Tesla in 1914, it is recently drawing attention again. The commercialization of the magnetic induction WPT that uses electromagnetic induction between transmitter and receiver coils has been tried. However, its efficiency may abruptly reduce according to the distance and arrangement between coils and coils. Another WPT type uses the microwave to transmit large power, over tens of watts, using super-high frequency. However, the microwave method is only used in space development because of the problems including the rectenna size, harmfulness to human body due to the use of high frequency, and reduced efficiency by the surrounding environment. To address these problems, Professor Marin Soljacic of MIT proposed the magnetic resonance type WPT technology in 2007. Using the resonance between transmitter and receiver coils, this method enables the WPT in a few meters' distance, and causes no harmful effect on human body because it uses a low frequency range. Accordingly, it seems that this technology can be applied to diverse sectors, and it is continuously being studied to improve its efficiency. In this study, a superconducting coil was fabricated and applied to the magnetic resonance WPT. The superconductor has very low resistance at very low temperature. So it can increase the quality factor (Q-factor), which is the frequency quality characteristic, reducing the reflectivity (S11) in WPT. The superconducting coil requires a cooling system to keep the critical temperature. Therefore, receiver coil was combined with a copper coil with the same resonance frequency considering the use of superconducting coils to real application. A superconducting coil was applied to the transmitter side to increase the Q-factor, and a copper coil was applied to the receiver side to improve the applicability and mobility of the electronic devices. In this setting, the WPT and the 1:n WPT characteristic were considered to derive the performance and characteristic of the magnetic resonance WPT required in real application.