Research On Coil Self-positioning Method For Inductive Wireless Power Supply System

Inductive Wireless Power Supply(IWPS)technology is one of the effective ways to solve the safe and flexible power consumption of mobile devices,such as portable electronic devices.However,in practical application,the transmitting and receiving coils are usually difficult to be aligned accurately,which will bring about the adverse effects to the system operation,such as the decrease of transmission power and efficiency.For adjusting the IWPS system to the best electromagnetic coupling state,it is very important to realize accurate positioning of coils.Drone has been widely used in such fields as electric power inspection and photographing and crop monitor.Using inductive wireless power supply technology to charge the drone can avoid the problems of electric shock,leakage and spark existing in the traditional charging method.In practical applications,the offset between the coupling coils would reduce the wireless energy transmission efficiency of the system and increase the charging time.Moreover,the voltage and current stress of power electronic devices in the system would also increase,which makes device selection difficult and cost increase.For this purpose,according to the research background of this thesis,the proposed positioning strategy was analyzed.For the one-to-one coil system,a self-positioning method based on the parameter identification of mutual inductance was proposed for inductive power transfer system.This method can provide the accurate orientation of receiving coil without the additional auxiliary coils or position sensors.The analytical formula for describing the relationship of mutual inductance and coil position was first deduced,and then the changes of mutual inductance under the position disturbance were combined to solve the three-dimensional coordinates of the transmitting coil.Therefore,the autonomous positioning of an inductive wireless power supply system could be achieved.Finally,the one-to-one coil system with S-S topology was built.The positioning accuracy of this method was verified by experimental data,and the applicability of this selfpositioning method was discussed.In order to improve the anti-offset ability of receiving coil,the number of transmitting coil could be increased.Because the position of the receiving coil is not fixed,when increasing the number of transmitting coils,some transmitting coil units would work ineffectively.In this thesis,for the many-to-one coil system,the positioning method and activation strategy of coil array were proposed.And then,the structure of coupling coil was designed.The transmitting coil array with hexagonal uniform distribution and receiving coil that completely covers one transmitting coil unit was constructed.By collecting direct current value in the secondary side of IWPS system,the mutual inductance parameters between the receiving coil and the transmitting units were obtained.So that,the coordinate of receiving coil could be obtained by "three-point positioning" method.Under the condition that the current of each transmitting unit is constant and same,the calculation formula of the transmission efficiency of many-to-one coil system was derived,and the judgment condition of the optimal transmission efficiency was given.Thus,in the transmitter coil array,the transmitter coil unit that should be activated was identified.The many-to-one coil system with S-S topology was built to verify the proposed method in experiment,the applicability of positioning method and activation strategy of coil array was discussed.The experimental results of one-to-one coil system show that it can realize the effective and accurate positioning between the transmitting coil and receiving coil,and the positioning accuracy is within 1mm,which meets the requirements of practical application.And the experimental results of many-to-one coil system show that it can also realize the effective and accurate positioning,and the positioning accuracy is also within 1mm.By activation strategy of transmitting array,the efficiency was improved.This strategy ensures the efficient energy transmission of the IWPS system.