Research On Power Distribution Of Multi-frequency Multi-load Magnetically Coupled Resonant Wireless Power Transfer System

With higher requirements for simple,convenient,safe and green power transfer in the market,widespread attention has been paid for the researches and application developments of wireless power transfer(WPT).Among different kinds of WPT technologies,magnetically coupled resonant(MCR)has been considered as one of the most promising over recent years for its superiorities of long transmission distance,high efficiency and transmission power,and immunity from non-magnetic obstacles in the mid-range WPT applications.Currently,the published studies of MCR WPT mainly focus on single-load systems.With the increasing maturity of single-load MCR WPT technology and the increasing demands for simultaneous delivering power to multiple devices,some research work on multi-load MCR WPT has begun to emerge.Undoubtedly,to satisfy power requirements of each load with high efficiency is the most urgent issue in multi-load systems.In this thesis,the multi-frequency concept is proposed to solve this problem from a new perspective.Employing a basic coil structure with a single transmitter and multiple receivers,a multi-frequency circuit topology driven by multiple inverters is implemented.Based on the influence factors of transmission characteristics revealed from the equivalent circuit model,a high-efficiency design method is presented,and then,an open-loop strategy of power distribution by adjusting the resonant frequencies of the transmitter and multiple receivers,and a closed-loop strategy by cascading DC-DC converters at each receiver for load matching,are put forward respectively.In the multi-load system,the cross interference caused by introduced multi-frequency energy is unavoidable under the multi-coil coupling circumstance,and severe cross interference will increase the difficulty of parameters design and control for multi-load power distribution.In this thesis,a cross interference elimination method,introducing passive compensation circuits into receivers,is proposed from the perspective of impedance matching.Utilizing the impedance characteristics of the series and parallel resonant networks,the transmission paths of different frequency energy can be effectively restrained and the targeted power transfer of the specific frequency to the selective loads can be achieved.Finally,a prototype of a double-frequency double-load MCR WPT system is built and tested for experimental verifications in the laboratory.The experimental results are consistent with the theoretical analysis,and the effectiveness of the two proposed power distribution strategies and the cross interference elimination method are well verified.As shown from the detailed experimental results,the system can satisfy the power requirements of each load with high efficiency by introducing multi-frequency excitations.When the cross interference is completely eliminated,targeted power distribution can be definitely achieved.