Design And Analysis Of Wireless Power Transfer System With Low Magnetic Leakage

Wireless power transfer(WPT)system can transmit energy to power-using equipment through the air and other media by the high-frequency magnetic field,which helps to eliminate sparks generated by plugging and unplugging wires and improve the automation level of the system.It has the advantages of safety,convenience,and beauty.However,the WPT system is a loosely coupled magnetic field system,which inevitably generates magnetic leakage in space.The magnetic leakage interferes with the regular operation of electromagnetically sensitive equipment and even endangers the organism’s health,which has intensified the anxiety about the safety of WPT systems.In order to promote the further development of WPT systems,it is urgent to solve the magnetic leakage problem of the WPT system.Typical magnetic shielding includes conductive shielding,ferromagnetic shielding,and coil shielding.Among them,coil shielding has the advantages of low heat generation and a controlled shielding effect,which is a popular magnetic leakage shielding method.However,the generally larger size of the shielding coil may result in insufficient installation space for the WPT system.In addition,an important development direction of the WPT system is to make the system lighter and more compact.Therefore,how to reduce the size of the shielding coil under the premise of ensuring the safety of the magnetic field of the system has essential research significance.The main contents of the thesis are given as follows:1)The relationship between the equivalent reactance of the shielding coil and the magnetic shielding effect is clarified.First,the equivalent circuit of the WPT system with the shielding coil is established,and the current expressions of each coil with the equivalent reactance of the shielding coil are derived.Secondly,the influence of each coil current on the magnetic induction intensity at any point in the system is analyzed,and the relationship between the equivalent reactance of the shielding coil and the magnetic shielding effect at this point can be clarified.Thirdly,the magnetic shielding target is extended from a single point to the three-dimensional target space,and an optimization method of the shielding coil equivalent reactance is proposed and applied to reduce the maximum magnetic induction intensity in the three-dimensional target space.Finally,an experimental prototype is built to verify the effectiveness and feasibility of the shielding coil equivalent reactance optimization method.The experimental results show that the magnetic induction intensity of the target space meets the safety standards when the reactive resonant coil obtains the optimal equivalent reactance.The maximum magnetic induction intensity in the target space was reduced by 53.40%,and the average decreased by 58.15% compared with that without the reactive resonant coil.The system efficiency was reduced by only 0.31%.In addition,in view of the deviation of the system and the target to be shielded is located around the system,the applicability of the proposed method is analyzed theoretically,and the magnetic shielding effect of the system is explored through experiments.2)A compact magnetic coupler is proposed,which integrates the shielding coil and compensating inductance.First,a compact magnetic coupler is proposed,which uses the partial compensation inductance of the LCC-LCC compensation topology as a magnetic shielding coil.The design principles of the magnetic coupler are given.Secondly,the magnetic shielding principle of the proposed magnetic coupler is analyzed.Thirdly,the influencing factors of the magnetic shielding effect and the parameters of the optimal compensation capacitor are analyzed.Finally,an experimental prototype is built to verify the effectiveness and feasibility of using the proposed compact magnetic coupler to reduce the magnetic leakage of the system.The experimental results show that after the compact magnetic coupler is adopted,the maximum magnetic flux leakage on a line in the right-center of the system is reduced by 82.4%,and the average value is reduced by 75.18%.The system efficiency was reduced by only 0.32%.Compared with the system using a passive shielding coil in Chapter3,the power density of the system is increased by about 2.78 times.In addition,in view of the deviation of the system and the target to be shielded is located around the system,the applicability of the proposed method is analyzed theoretically,and the magnetic shielding effect of the system is explored through experiments.