Research On Switching LCC-S/P Compensation Network For IPT System

Inductive Power Transfer(IPT)technology has attracted more and more attention from domestic and foreign scholars and industry because of its safety,reliability,efficiency and convenience.How to realize the stable output characteristics and high-efficiency transmission characteristics of the compensation network in IPT system have always been the key technical issues in the research of IPT technology,which is of great significance.Aiming at the charging characteristics of the constant current and constant voltage of lithium battery in electric vehicle,this paper studies the optimization strategy of compensating the output characteristics and transmission efficiency of constant current and constant voltage based on the LCC-S/P compensation network structure switching of the IPT system.In this thesis,the fundamental wave approximation analysis method is used to analyze the IPT system structure and its equivalent model,and the fundamental wave equivalent model of the resonant network is obtained.Then,according to contrasting analysis the characteristics of magnetic field distribution and magnetic field shielding and anti-offset of the square planar spiral coil and the circular planar spiral coil,the coil structure of Loosely Coupled Transformer(LCT)is designed,and selecting the square planar coil as the transmission structure of electric energy.And then based on the LCC type compensation topology,the derived composite compensation network structure LCC-S and LCC-P compensation network structure are analyzed and illustrated.Combining the characteristics of the two composite compensation topologies and the characteristics of the constant voltage charging after the constant current of the lithium battery,the structure of the LCC-S/P compensation network switching is constructed,based on which compensation network to realize the constant current and constant voltage output characteristics of the IPT system.For the main research content of this paper,firstly,according to the analysis of constant current and constant voltage output characteristics of any high-order compensation network,the basic "LC" type,"П" type and "T" type compensation network structure cascade method are adopted to achieve constant current or constant voltage output of any high-order compensation network,and then analyze the resonant conditions of constant current or constant voltage for the IPT system of LCC-S and LCC-P compensation networks,and propose a dual-mode control method that realize the output characteristics from constant current output to constant voltage by switching the structure of the LCC-S and LCC-P compensation networks at a fixed resonant frequency.And then,the transmission efficiency of the compensation network is analyzed,according to the characteristics that LCC-S compensation network features high efficiency at heavy load and low efficiency at light load in constant current mode,while LCC-P compensation network exhibits low efficiency at heavy load and high efficiency at light load in constant voltage mode,combining with the heavy load and light load characteristics of lithium battery charging process,this paper proposes an efficiency optimization strategy and designs a block diagram of the optimal control flow based on LCC-S/P compensation network switching.Finally,the experimental platform is built to test the constant current and constant voltage output characteristics and efficiency optimization control strategy of the IPT system based on LCC-S/P compensation network switching.The experimental results are consistent with the simulation results and theoretical analysis.The verification of the dual mode control method to achieve constant current to constant voltage output characteristics and efficiency optimization control strategy based on LCC-S/P compensation network switching is correct and effective.