Study On Characteristic Analysis And Optimization Of Transmission Network For Inductive Power Transfer System

Inductive power transfer(IPT)technology transfers power wirelessly through air using magnetic field as the energy carrier,which overcomes the physical space limit,security and reliability(ageing,wear,leakage,et al.)of wire's form.Subject to hardware condition,IPT technology has developed slowly.The emergence of power electronics has further promoted the development of IPT technology and achieved the promotion of IPT technology in the practical application.The design and optimization for the transmission network is crucial to the magnetic characteristic and electrical characteristic of the IPT system.Comprehensively considering the source-network-load characteristic,the design and optimization of the transmission network is the basis to ensure the safe,stable and reliable operation for the IPT system.This dissertation focuses on the magnetic characteristic and electrical characteristic of the transmission network for the IPT system,studying on the modeling of the magnetic characteristic and the static electrical characteristic for the coupler and the optimal design method of the static electrical characteristic for the passive compensation network as well as the modeling and optimization of the dynamic electrical characteristic for the transmission network.The main works and conclusions are as follows:(1)For the magnetic characteristic modeling of the coupler in the transmission network of the IPT system,the magnetic field model of the IPT system with shielding based on the double Fourier series is proposed to explain the influence of the shield on the coupler.The application and design of the shield can improve the electromagnetic compatibility and impact on the magnetic characteristic of the coupler for the IPT system,where the magnetic field model of the IPT system with shielding is beneficial to understanding the influence of the shield on the IPT system in theory.Meanwhile,the shielding effectiveness of different shields are evaluated according to the Moser theory.Then the proposed magnetic field model and the theoretical analysis are validated in experiment based on the IPT magnetic measuring platform.Furthermore,from the viewpoint of the equivalent circuit,the circuit energy efficiency modeling for the IPT system with shielding is proposed to reveal the relationship between the shield's electromagnetic parameters and the static electrical characteristic(the equivalent circuit and the efficiency of the transmission network),which provides the theoretical support for the design of the coupler.(2)For the static electrical characteristic design and optimization of the passive compensation network(PCN)in the transmission network of the IPT system,the design methods of high-order PCN based on two-port network model and multi-objective evolutionary algorithm are proposed.Considering the system modeling and the PCN design facing difficulty with the magnetic cross coupling in multi-coil and multi-load IPT system,the decoupling scheme based on the cascade architecture and multi-layer-shielding structure is proposed to achieve thee magnetic cross decoupling of unexpected coupling coils and improves the coupling of expected coupling coils and the efficiency of the transmission network.An IPT system with six coils and three loads are designed to achieve constant load voltages using the decoupling scheme and high-order PCN design method,which is validated in experiment.Furthermore,a multi-objective evolutionary optimization algorithm based PCN design method for the IPT system is proposed to solve the variety problem and optimization problem for PCN.The unit mathematic model of the high-order PCN based on the T-type circuit is built to obtain the optimization modeling for the PCN.Then,NSGA-? based multi-objective optimization algorithm is construct to design the PCN of the IPT system,which is also applied in the PCN design of the cascade multi-coil and multi-load IPT system.The proposed PCN design scheme provides a new technical approach for the IPT system.(3)For the dynamic electrical characteristic modeling and optimization of the transmission network for the IPT system,the dynamic model for the IPT system based on extended describing function and a two-stage IPT system based optimization scheme for load transient are proposed.The design method of the coupler and the PCN for the IPT system is proposed based on the steady-state model,which can achieve good steady-state performance,but it is difficult in ensuring the high dynamic performance for load step.While,the design and optimization of the dynamic performance are beneficial to enhance the system reliability and the power supply quality.Therefore,the dynamic mathematical model of the LCC/S compensated IPT system based on extended describing function is proposed,and the dynamic electrical characteristic is analyzed for the LCC/S compensated IPT system.Furthermore,applying the buck converter into the transmission network,that is,LCC/S compensated IPT system cascading buck converter,auxiliary inductor based n+1 switching control scheme is proposed to improve the load transient performance.The proposed design and optimization method provide a reference idea to improve the dynamic performance for the IPT system.