| Magnetically-coupled Resonant Wireless Power Transfer(MCR-WPT) has been widely applied in medium-small power field due to its advantages of long transfer distance, high transfer power and high transfer efficiency. However the ubiquity of DC load in low-voltage distribution system impels this study on DC/DC type wireless power transfer system. In this paper, the modeling of WPT system with rectifier bridge load and its influence on transmission characteristics is analyzed, meanwhile, the analysis and design of the DC/DC type wireless power transfer system is also payed attention. The study is aimed at providing theoretical foundation and practical reference. The main details are as follows:Firstly a method of modeling and analysis of MCR-WPT for a rectifier-bridge load is proposed. Most of the low-voltage power distribution terminals are DC loads, and the modeling of which is directly put as a pure resistance load, revealing the influence on transmission characteristics incompletely. So a steady-state equivalent nonlinear resistance model is derived to describe the rectifier-bridge load. Hence transmission characteristics about system output power and efficiency are derived to get the conclusion that there exists a maximum efficiency point with distance varying, which is different from the reported conclusion when considering the rectifier bridge load as an pure resistance. The obtained theoretical analysis can supply theoretical foundation for MCR-WPT driving small power DC load.Then the influence on transmission characteristics caused by LED connection forms at the rated power is discussed based on the theory above. It is necessary to drive LED wirelessly due to its widespread application in lighting-system as a new green illuminant. While the dynamic model is too complex to be built and the report about driving wirelessly is also insufficient. So the approximate steady model is obtained by measuring the u-i characteristics and then the reasonable LED connection forms at rated power with different transimission distance and efficiency is determined intuitively. This section provides a scheme to adjust transmission characteristics through LED connection forms without extra equipment giving a reference for practical design.In addition, a class E2 type DC/DC converter topology is presented in order to improve the overall efficiency. The design of the power conversion block at present can not meet the demands of both high frequency and high efficiency. So a class E2 type DC/DC converter topology is put forward and the soft switch mechanism is analyzed in detail and finally the expressions of the main parameters are derived at steady state. The study of this chapter presents an analytical design procedure which provides guidance to practical application due to its periorities of high efficiency and high power density. |
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