Research Of Wireless Power Transfer Systems Based On Electric Coupling And Magnetic-Electric Combined Hybrid Coupling Using Two Coupling Plates

Due to the virtues of simple structure and easy implementation,two-coil inductive power transfer(IPT)technology has been applied in various scenarios,such as wireless charging for electrical vehicles,railway vehicles,material handling systems,and online monitoring devices on high-voltage power transmission lines.However,the transmission efficiency of a two-coil IPT system is limited by the coupling between transmitting and receiving coils,which degrades rapidly with transfer distance increasing.To extend the transfer distance and promote the transmission efficiency,the inductive and capacitive combined hybrid wireless power transfer(HWPT)system provides an alternative.Nevertheness,for existing HWPT systems,four plates are needed to complete the electrical coupling.Moreover,the coupling plates are separated from the coil,which significantly increase the area of the coupler and result in inconvenience for practical implementation.In this dissertation,the general circuit for a two-plate capacitive power transfer(CPT)system is firstly proposed.Then,the full-area coupling plates are replaced by ring/frame shaped ones,thus achieving a ring/frame-shaped two-plate CPT system.Furthermore,the ring/frame-shaped plate is integrated with the coupling coil to form a compact and efficient hybrid coupler.Besides,an LCC resonant topology and a resonant parameter tuning circuit are designed and deployed at transmitting side so that the proposed HWPT system can be more adaptive to practical parameter changes.To reduce the number of coupling plates,the general circuit structure for a two-plate CPT system is proposed.For different application scenarios,the corresponding circuit models are established.For the sake of accurate analysis in high frequency situations,the stray capacitance of coupling plates with respect to the ground is also taken into consideration.The availability and accuracy of the proposed circuit model are verified through theoretical analysis and experiments.Moreover,the influence of promoting the resonant frequency is also investigated to achieve better system performance.To reduce the area occupied by full-area coupling plates,a ring/frame-shaped two-plate CPT system is proposed.By utilizing the fringe effect of charge distribution,conventional full area coupling plates are replaced by ring/frame-shaped ones.The function relationship between the width of a metal ring/frame and the capacitance terms of a two-plate capacitor is explored by using the finite element modeling software.Then,a proper ring/frame width is selected to achieve both a comparative transfer efficiency and a compact coupler structure.Meanwhile,the influence on power transfer capability(PTC)by promoting the resonant frequency is also studied.To enhance the transfer efficiency at a large distance,a HWPT system structure based on the ring/frame-shaped two-plate CPT structure is proposed.In the proposed HWPT system,the coupling coil is embedded in the central zone of a metal ring/frame,thus achieving a compact and simple hybrid coupler.Furthermore,the equivalent circuit of the proposed HWPT system is built,and the promotion of PTC over conventional two-coil inductive systems is analyzed from the perspective of reflected impedance.Similarly,the influence of promoting the resonant frequency is also analyzed.Both the theoretical and experimental results show that,with a high resonant frequency,the proposed HWPT system can effectively enhance the coupling between the receiving and transmitting sides,thus promoting the system PTC.To make the proposed HWPT system more adaptive to distance and load variations in practical situations,an LCC resonant topology at transmitting side is designed,which can maintain a stable working current in transmitting resonant loop against distance and load variations.Additionally,considering that the resonant parameters(i.e.,the resonant inductance and capacitance)of transmitting side may deviate from those of receiving side due to aging,manufacturing tolerance and environment variation,etc.,a parameter deviation compensation method is proposed and a tuning circuit is designed,thus reducing the adverse influence on PTC by the resonant parameter detuning.Finally,the research works of this dissertation are summarized,and the further researches on HWPT systems are prospected.