| Magnetically Coupled Resonant Wireless Power Transfer(MCR-WPT)technology had attracted extensive attention and developed rapidly because of its high transmission efficiency and large transmission power in the near-field region of the electromagnetic field.In practical applications,horizontal misalignment would inevitably occur between the transmitting coil and the receiving coil,resulting in strong fluctuations in the mutual inductance between the coils,resulting in output power fluctuations and reduced efficiency,which seriously affects the stability of the system.Therefore,improving the misalignment tolerance of the coil in the horizontal direction is of great significance to promote the application and development of MCR-WPT technology.In this thesis,starting from the optimal design of the coil body structure,based on the quasi-constant mutual inductance calculation and optimization method,a new type of coil structure with high misalignment tolerance in the horizontal direction is designed,without adding any additional resonance compensation network and auxiliary control device.It could greatly improve the anti-misalignment capability of the system in the horizontal direction.In this thesis,the quasi-constant mutual inductance calculation and optimization design of the new coil structure were carried out as follows.(1)Firstly,the mutual inductance model of the wireless power transmission system with two receiving coils in series was established,and its output energy efficiency was analyzed.Aiming at the mutual inductance fluctuation problem of coils offset in the horizontal motion direction,a rectangular asymmetrical anti-series structure of two receiving coils was proposed,and then a mutual inductance calculation method based on vector potential was proposed to calculate the rectangular asymmetrical anti-series connection of two receiving coils.The mutual inductance of the structure was analyzed,and the mutual inductance law of the structure was analyzed by the proposed mutual inductance calculation method.Based on this,an optimization method of coil parameters was proposed to obtain quasi-constant mutual inductance.The series coil was not only simple in structure principle and optimization method,but also could keep the mutual inductance of the coil almost constant within the limit misalignment distance of 19.7cm in the horizontal motion direction.The comparison of calculation,simulation and experimental results verified the effectiveness of the proposed structure and the correctness of the optimal design method.(2)Aiming at the mutual inductance fluctuation problem of the coil in the horizontal movement direction and lateral misalignment,combined with the proposed mutual inductance model of the two-receiving coil series-connected wireless power transmission system,a two-receiving coil series-connected structure and a magnetic potential vector-based system were proposed.The mutual inductance calculation method of the analytical method was used to calculate the mutual inductance of the series structure of two receiving coils under the offset condition,and then the mutual inductance characteristics of the series structure of the two receiving coils were analyzed,and a quasi-constant mutual inductance optimization method was proposed for the structural parameters of the coils.This method provided a simple and effective theoretical method for studying the variation law of the mutual inductance of the wireless power transmission system and the design of the coil structure and function.The accuracy and feasibility of the mutual inductance calculation method and optimal design method are verified by comparing the formula calculation,finite element simulation and experimental measurement data results of the two-receiving coil series structure and the traditional two-coil structure.The series structure of two receiving coils had high misalignment tolerance in both horizontal and lateral directions,and the fluctuation rate of mutual inductance is within 3%,which improved the system’s ability to adapt to lateral movement on the basis of horizontal motion.(3)Aiming at the mutual inductance fluctuation problem of coils misalignment in all horizontal directions,according to the proposed mutual inductance model of a wireless power transmission system with two receiving coils in series,a circular anti-series structure with two receiving coils was designed,and its composition principle and mutual inductance characteristics are analyzed.Then,based on the parameter vector method,a mutual inductance calculation method of the circular anti-series structure of the two receiving coils at any relative position was proposed,and a coil structure optimization design method based on quasi-constant mutual inductance is proposed.The novel coil structure of tolerance provided a theoretical approach.The effectiveness and accuracy of the proposed quasi-constant mutual inductance calculation and optimization design method were proved by comparing and analyzing the formula calculation,electromagnetic field finite element simulation and the mutual inductance data obtained by the measured coil.The circular anti-serial structure of the two receiving coils could effectively solved the problem of severe fluctuations in mutual inductance caused by the horizontal offset of the wireless power transmission system coils in all directions stability. |
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