Research On Characteristic And Optimization Design Of Wireless Power Transfer Through Non-Ferromagnetic Conductive Medium

Magnetic coupling resonant wireless power transfer (WPT) technology is considered to be an alternative to transfer electric power wirelessly through the alternating electromagnetic field in the form of resonant coupling. Due to the advantages of long transfer distance, large transfer power and compact system structure, the technology has shown extraordinary potential in many industrial applications such as electric vehicles, rail transportation, intelligent household appliances and so on.To improve the system adaptability to different working environment, the impacts of non-ferromagnetic conductive medium such as metal aluminum plates and seawater on the system performance are investigated. The dissertation intend to maximize system output power and the main contributions can be summarized as follows.Mutual inductance theory and loosely coupled transformer are firstly introduced, on the basis of which the equivalent circuit model of WPT system working in non-ferromagnetic conductive medium is presented. The mathematical expression of system output power is then derived and corresponding influential factors are analyzed. In particular, the variations of system frequency feature caused by different transmitting mediums are discussed.Structure optimization of the resonant coil is carried out to diminish the effect of non-ferromagnetic conductive medium on system performance as much as possible. Accordingly, flat disc coil and spiral one are employed to compare the system characteristic. In addition, auxiliary coils (drive coil and load coil) and relay coil are added to enhance the output power. As for WPT system with fixed working frequency or nonadjustable driving frequency, a compensation technology by adopting ferromagnetic cores is proposed and corresponding system performance is presented.Finally, an experimental prototype consisting of high-frequency power source, resonators and loads is designed. High-frequency inverter under the control of UCC3895 is used to generate continuous and adjustable voltages ranging from 50 KHz to 200 KHz. A series of experiments are implemented to demonstrate system performance in different working conditions. The influence of non-ferromagnetic mediums on system performance, the contribution of auxiliary coils and relay coils to output power increase along with the performance improvement due to the application of ferromagnetic cores are all included in the experiments.