Research On Modeling And Controlling Of Multi-phase Magnetically Coupled Resonant Wireless Power Transfer System

Wireless power transfer(WPT)techniques have attracted an increasing attention with the development of power electronics for its safety and superiority to conventional cable transmission.Magnetically coupled resonant(MCR)WPT,which is essentially based on electromagnetic induction,has become one of the most promising WPT technologies in mid-range applications for its higher output power and transmission efficiency within a long distance.It has been revealed that transmission characteristics of the MCR WPT system are significantly affected by the spatial scales of sending coils and receiving coils.And the sensitivity of the system to spatial scales can be effectively reduced by the introduction of multi-phase coil structures.This thesis focused on two kinds of multi-phase MCR WPT systems,namely two-phase orthogonal MCR WPT system and three-phase cylindrical MCR WPT system.The transmission characteristics of two systems were studied by the methods of theoretical analysis,which were based on both distributions of magnetic field and the equivalent circuits,simulations with Ansys Maxwell and experimental verifications.As the essence of MCR WPT is electromagnetic induction,this thesis deduced the distributions of magnetic field in detail when the phase angle control was adopted into the current excitations.The flux through the receiving coils of different geometry was analyzed and the induced voltage was obtained using Faraday’s law of electromagnetic induction,which revealed the relationships between transmission characteristics and spatial scales of coils from the physical perspective.This thesis also presented the equivalent circuits of the two multi-phase MCR WPT systems.The formulae of mutual inductance under different spatial scales of coils were obtained,and the constraints between output power,transmission efficiency and spatial scales of coils were revealed taking the mutual inductance as an intermedia.Finally,the simulation models were established in Ansys Maxwell that is a popular finite element simulation software.Meanwhile,two prototypes were built in the laboratory.The transmission characteristic curves were obtained by simulation and experimental results.And the correctness of the theoretical analysis was verified by both simulation and experiments.