Research On Hybrid Topology-based Wireless Charging System With Constant Current Or Constant Voltage Output

Inductive power transfer(IPT)technology breaks the limitation that the energy must rely on carriers(wire,cable and other media)to deliver.Since there is no direct electrical contact,the problem of electric spark caused by the traditional power transmission is avoided.Due to the advantages of flexibility,safety,and reliability,IPT technology has been widely used in medical equipment,consumer electronics,electric vehicles,and other fields.IPT technology is mainly used for battery charging.During the whole charging process,the equivalent load of the battery changes significantly ranging from several ohms to hundreds of ohms.In order to ensure the safety and reliability of battery charging and to prolong the battery lifecycle,constant current-constant voltage(CC-CV)charging mode is usually adopted.Therefore,IPT systems need to provide constant charging current and voltage for the wide range equivalent load of the battery.The existing methods for implementing CC-CV charging in IPT systems are mainly divided into two categories: 1)control strategies for CC-CV charging.This method will increase the control complexity of the system and additional circuits,requiring a wide range of modulation index.2)Switching between different compensating topologies for CC-CV charging.However,the numbers of components and switches are too large in the existing methods.Besides,many hybrid topologies cannot guarantee zero phase angle(ZPA)between the input current and voltage both in CC and CV modes.Therefore,it is necessary to study a new hybrid topology for battery charging,simplifying the control complexity of the system,and reducing the number of the switches for topology switching,as well as achieving ZPA during the whole charging process.The main work of the thesis is given as follows:1)The analysis of the input and output characteristics for compensation topologies.Four topologies such as S-S,S-LCL,LCL-S,and LCL-LCL are systematically analyzed,and the input and output characteristics of these topologies are obtained respectively.By deriving the mathematical models of the four topologies,the conditions for achieving ZPA in CC and CV modes are obtained.2)The study of a new hybrid topology with CC or CV output.A new hybrid topology with CC or CV output is proposed.First,the equivalent T-circuit model of the hybrid topology in CC mode is analyzed.Then,the equivalent ?-circuit model cascaded with a T-circuit model of the hybrid topology in CV mode is elaborated.Based on the input and output characteristics of the hybrid topology,an additional switch is used for the switch between CC and CV modes.Finally,the validity of the proposed hybrid topology for CC-CV charging is verified by the Simulink simulation and experiment.