Research On Wireless Charging Technology Employing Orthogonal Laminated Magnetic Integrated Coupler

Wireless charging technology for electric vehicles solves the problems of interface wear and aging,vulnerability to environmental impacts,and potential electric leakage and shock in conductive charging technology.It has the characteristics of safety,reliability,flexible power supply,and strong environmental adaptability.Limited by the capacity and cost of electric vehicles' power battery pack,using high-power wireless charging to short the charging time solves the problems of mileage anxiety and improves the user experience.However,due to the limitation of power device capacity and cost,the traditional wireless charging system with the single power transfer channel may not meet the demand for high power transfer.Although using multiple magnetic couplers in series or parallel to construct multiple power transfer channels reduces the voltage stress and current stress of the device,there are some problems in this method,such as low space utilization,cross-coupling between coils affecting system performance,poor frequency stability of compensation topology in multiple power transfer channels,and weak research on system-level circuit topology and control methods.To solve the above problems,this paper researches several key technologies involved in the wireless charging system with multiple power transfer channels,so as to achieve high flexibility and reliability of high-power wireless energy transfer.From the perspective of the power transfer channel,the high-performance magnetic coupler that integrates multiple power transfer channels is studied;From the perspective of frequency stability,the dynamic tuning method that is used to realize frequency stabilization control for compensating topology in multiple power transfer channels is studied;From the perspective of system-level design,the circuit topology and control method of the wireless charging system with multiple power transfer channels are studied.Aiming at the problems of the traditional magnetic coupler in improving output power,the orthogonal laminated magnetic integrated coupler that features multiple power transfer channels is proposed under the specific size constraint of the transmitter and receiver.The key factors that influence the transfer power of the magnetic coupler are analyzed,and then the magnetic integrated overlap coil is constructed by using magnetic integration technology and the orthogonal decoupling method.The working principle and structural characteristics are analyzed by the magnetic circuit principle and the mutual inductance model.Different magnetic integrated overlap coil is used to construct different types of the orthogonal laminated magnetic integrated coupler,and then their coupling performance and electrical characteristics are analyzed.Meanwhile,the automatic position alignment method based on mutual inductance identification and mechanical auxiliary positioning is proposed,which provides a feasible scheme for improving the anti-misalignment adaptability.Simulation and experimental results show that the orthogonal laminated magnetic integrated coupler increases the system output power and reduces the voltage stress and current stress of the device.Due to the existence of parameter drift and matching error,the non-tuning state of the compensation topology induces inconsistent work characteristics of multiple power transfer channels,the degradation of system efficiency and output power,and system abnormal operation.Therefore,the dynamic tuning method based on soft switching controllable capacitor is proposed and employed to realize frequency stabilization control for compensating topology in multiple power transfer channels.The necessity of frequency stabilization control for LCC-S compensation topology and the problems of existing tuning methods are analyzed.From the view of circuit topology,the dynamic tuning method that is based on the zero phase difference search is proposed.The zero phase difference is used as the frequency stability criterion,and then the tuning state determination is achieved by searching the zero phase difference through variable step size perturbation and observation method.The simulation and experimental results show that the proposed method solves the problem of system performance degradation that is caused by parameter fluctuation in compensation topology and has the characteristics of less passive components and simpler control method.The multiple power transfer channels in the orthogonal laminated magnetic coupler are used as the energy carrier,and the dynamic tuning method based on the soft switching controllable capacitor realizes the frequency stabilization control for compensation topology in multiple power transfer channels.On this basis,the circuit topology and control method for the input series and output series(ISOS)wireless charging system with multiple power transfer channels is proposed.It solves the problems of high voltage stress,poor fault tolerance,weak power expansion,charging current/voltage fluctuation,and nonoptimal efficiency operation that exists in the wireless charging system with the single power transfer channel.In order to solve the problem of system efficiency and output power degradation that are caused by the imaginary part of the input impedance of the existing controllable rectifier,the phase synchronization controlled controllable rectifier is proposed to realize the resistive input impedance and the simplification of the receiver structure.Meanwhile,its operating principle is analyzed in-depth.To meet the actual charging requirements of the power battery pack,the coordinated charging control method for constant current(CC)/constant voltage(CV)charging and system efficiency improvement is proposed.The system fault-tolerant method is analyzed to ensure the system runs at reduced capacity in the fault state.Through analyzing power losses and resonant current ratio,the method for reducing system loss is analyzed to lay the foundation for device selection and heat dissipation design.The simulation and experimental results verify that the ISOS wireless charging system realizes CC/CV charging for multiple power transfer channels and improves system efficiency and fault-tolerance performance.In order to expand the applicability of wireless charging system s in multiple fields and achieve that goal of no wireless communication for charging control and simplifying the receiver structure,the primary-side feedback-controlled wireless charging system is proposed to improve the stability and reliability of CC/CV charging in the complex electromagnetic environment.The parameter identification models of charging current,charging voltage,and mutual inductance are established by using primary-side electrical parameters.Then,CC/CV charging that is based on parameter identification is realized by the primary-side controller.Quadrature transformation method is proposed to obtain the mutual inductance and the sine and cosine value of phase angle that are related to the parameter identification models of charging current and voltage.Then,the recursive least square filter is used to reduce the influence of sampling error and measurement interference on the accuracy of parameter identification values.The experimental platform is built to verify that the proposed method reduces the dependence of the system on wireless communication and simplifies the receiver structure.