Research On The Position Detection Method For The Pick-Up Side Of Wireless Power Transfer System With Multi-Excitation Unit

Since the second half of the 19 th century,electrical energy has been transmitted mainly by direct contact with wires when humans entered the electrical age.However,with the development of the times,the traditional power supply with wire gradually reveals its shortcomings.For example,in some applications such as underwater,mine,oil field and mobile power supply,the traditional power supply inevitably has security risks.Therefore,people gradually shift their attention to the technical field of Magnetic Coupling Wireless Power Transfer(MC-WPT)to improve the safety,environmental protection and convenience of power supply.MC-WPT technology comprehensively contains many subject technologies,such as power electronics technology,electromagnetic field theory,and control theory,and it realizes the wireless transmission of electric energy.The primary side of the multi-excitation MC-WPT system contains multiple transmitter units.Therefore,compared with the traditional MC-WPT system which has single transmitter and single receiver,it is easier to realize high-power transmission of electric energy,and the current or voltage stress of the inverter is smaller.However,in practical engineering applications,the pick-up of the static multi-excitation MC-WPT system tends to deviate from the symmetrical position with the primary coil,thereby affecting the system power and efficiency.Therefore,in order to lay the foundation for position correction,and then ensure the transmission performance of the system,it is necessary to detect the position of the pick-up of the system.For the above-mentioned pick-up position detection problem,the main goal of this paper is to propose a pick-up position detection method suitable for multi-excitation MC-WPT system,so as to lay a theoretical foundation for the pick-up position correction.The basic composition and working principle of the multi-excitation MC-WPT system are analyzed in detail around the high-frequency inverter,resonance compensation network and coupling mechanism.This thesis propose a pick-up position detection method based on the multi-excitation MC-WPT system with multiple coils on the primary side.This method needs to utilize the relationship between the mutual inductance and the position of the secondary coil.Therefore,this thesis presents the measurement method of the mutual inductance between the primary and secondary coils,and its variation with the offset distance.It also points out that the mutual inductance values should be ensured not negative when the coupling mechanism is designed.The offset distance between the secondary coil and each primary coil can be obtained by the mutual inductance value.On this basis,the two-dimensional coordinates of the center point of the secondary coil are obtained by using ordinary least squares(OLS).In addition,its position detection error is analyzed.The analysis results show that the position detection algorithm based on OLS has certain limitations.Because it does not take into account the influence of the two-dimensional coordinate measurement error of the primary coil center point.Therefore,it is necessary to comprehensively consider the offset distance and the two-dimensional coordinate measurement error of the primary coil center point in order to improve the detection accuracy of the pick-up position.Then this thesis proposes to use constrained total least-squares(CTLS)to solve the two-dimensional coordinates of the secondary coil center point.Based on the COMSOL and MATLAB simulation platforms,this paper establishes a coupling mechanism and system circuit simulation model.In the square detection area with a side length of 12 cm,the horizontal and vertical coordinate errors of the center point of the pick-up obtained by the detection method of the pick-up position proposed in this paper are less than 6 mm.The simulation results verify the feasibility and theoretical analysis of the pick-up position detection method proposed in this paper.The specific steps of the position detection method are as follows: first,the mutual inductance of the primary and secondary coils is obtained from the measured secondary coil current,and then the offset distance between the secondary coil and each primary coil are obtained from the mutual inductance,and finally the two-dimensional coordinates of the center point of the secondary coil are solved by CTLS algorithm.