Research On Compensation Topologies Of Inductive Power Transfer Systems With Constant Outputs

Inductive power transfer(IPT)technology has been employed in many applications such as consumer electronics,biomedical implant devices,underwater power supplies,electric vehicles,and so on.IPT systems have advantages of safety,convenience,and flexibility over traditional conductive power supply systems because the energy is delivered from power sources to loads through magnetic coupling without physical contact.In IPT practical applications,the battery is charged with constant current-constant voltage(CC-CV)mode,and the battery equivalent resistance has a wide variation during the whole charging process;the position of the primary and secondary coils is hard to fix resulting in inconstant coupling.With large load or coupling variations,how to keep the output of the IPT system stable is one of the key issues.Therefore,the thesis focuses on the compensation topologies against load variations or coupling variations.Combining circuit parameter design and magnetic coupler design,the purpose of the thesis is to let the IPT system equip with a native characteristic of loadindependent output or misalignment tolerance,then to simplify the control scheme and improve the output stability of the system.The main research work is as follows:(1)A method based on switching topology is proposed for the IPT system with CC-CV outputs.The IPT system with a series-series(SS)compensation topology and its equivalent T circuit are analyzed,which can realize the conversion between CC source and CV source when the circuit parameters satisfy certain conditions.An SS topology and a T circuit are connected to form a series/inductor-capacitor-capacitor(S/LCC)topology with CV output.With component optimization and parameter configuration,two switches and a capacitor are added to the secondary side to achieve the switch between the SS and S/LCC topologies,thus realizing CC-CV outputs.This approach cancels the communication between the primary and the secondary sides,and a single inverter can charge multiple loads with different charging modes.Finally,the effectiveness of the switching topology and parameter design method are verified by experimental results.(2)A method based on variable-parameter topology is proposed for the IPT system with CC-CV outputs.The output characteristics of the T topology driven by a voltage or current source are analyzed,and all the possible conditions for CC-CV outputs by altering one component parameter of the T topology are elaborated.With component optimization and parameter configuration,CC-CV outputs can be achieved by adding the variable-parameter T topology to an IPT system with an SS topology.This approach can reduce the number of components and switches,as well as improve the design freedom of charge current and charge voltage with the constraints of the loosely coupled transformer parameters.Finally,experimental results validate the performance of the variable-parameter topology.(3)A method based on reconfigurable topology is proposed for the IPT system maintaining stable output power over coupling variations.The power transmission characteristics of the detuned SS compensation topology are analyzed,and the relationships between the detuning ratio,coupling range,and input impedance are discussed.In order to expand the coupling range of the detuned SS topology,a reconfigurable topology is used to integrate two equivalent detuned SS topologies into an IPT system,doubling the allowable coupling range with the same output power fluctuation.The reconfigurable topology has two networks such as the delta network and wye network,as well as the applications of the two networks and parameter design process are given.Finally,the performance of the reconfigurable topology is tested in an experiment.(4)A method based on hybrid topology for the IPT system with constant voltage tolerating misalignment is proposed.The output characteristics of the input-series-output-parallel hybrid IPT system based on inductor-capacitor-capacitor/series(LCC/S)topology and S/LCC topology are analyzed,and the requirements of realizing load-independent output and misalignment tolerance are given.Quadruple D quadrature(QDQ)coils are introduced,and variations of the mutual inductances of the coils with X/Y,Z,and diagonal misalignments are elaborated.A parameter design approach is presented,and it can obtain the maximum allowable coupling range within the predetermined output voltage fluctuation.The comparisons between the input-series-output-parallel hybrid topology and input-paralleloutput-series hybrid topology are presented,demonstrating the applications of the two hybrid topologies.Finally,the hybrid topology and parameter design method are verified by the experimental results.On the basis of compensation topologies,the thesis utilizes the switching topology,variableparameter topology,reconfigurable topology,and hybrid topology to achieve CC-CV outputs against variable loads,to achieve constant power output and constant voltage output versus variable couplings for IPT systems.The theoretical analysis and experimental results indicate that the proposed compensation topologies indeed simplify the control scheme and improve the output stability of the IPT system.