Research On Hybrid Wireless Power Transmission Systems With High Misalignment Tolerance

The inductive power transmission(IPT)technology can transfer the energy in a predefined distance via the alternating electromagnetic field without the direct electrical contact.IPT has many unique advantages with no use of cumbersome wires,both electrical and mechanical isolation to improve the safety and reliability,and friendly operation in harsh environments,flexibility and convenience,etc.Therefore,IPT technology has been widely used in consumer electronics,electric vehicles,medical devices,rail transportation and robotics.For the IPT system,the coupling coefficient between the transmitting and receiving coils affects the transmission power and efficiency of the system directly.In some practical applications,such as electric vehicle or mobile phone charging,the position misalignment between the transmitting and receiving coils of the IPT system is prone to occur,which results in a change in the coupling coefficient between the coils,further affecting the transmission power and efficiency of the IPT system,and reducing system stability.Therefore,it is necessary to improve the tolerance misalignment capability of the IPT system for most IPT applications.Currently,the research on IPT systems with misalignment tolerance capability mainly focuses on magnetic coupling mechanism,control strategy and compensation topology.Using a complex magnetic coupling mechanism can improve the magnetic field distribution between the coils and reduce the effect of coils misalignment,but the misalignment tolerance capability is weak and the magnetic coupling structure design is complex.Using additional control strategies can adjust output power and efficiency,but additional signal transmission devices and DC/DC converters are added,increasing the system size and cost.Compensation parameter optimization can reduce the impact of coil misalignment on the system transmission power and efficiency,but it cannot achieve the characteristic of load-independent output.Combining two IPT compensation topologies with the same operating mode and complementary output characteristics can obtain a hybrid IPT compensation topology with tolerance misalignment capability,and the hybrid IPT compensation topology has the characteristic of load-independent output.However,methods for deriving general configurations of such hybrid IPT converters and their tolerance to misalignment are still missing.This paper focuses on hybrid IPT compensation topologies with high tolerance to pad misalignment.Moreover,a general design method of hybrid IPT compensation topologies with near load independent output and high tolerance to pad misalignment has been proposed.Firstly,four types of hybrid IPT compensation topologies are analyzed,i.e.,Input Parallel Output Parallel(IPOP),Input Parallel Output Series(IPOS),Input Series Output Parallel(ISOP)and Input Series Output Series(ISOS).In addition,the output characteristics of the four types of hybrid IPT compensation topologies with constant current(CC)and constant voltage(CV)conditions are analyzed separately.Comparative analysis shows that the hybrid IPT compensation topologies based on IPOP and ISOS has tolerance misalignment capability under CC output,and the hybrid IPT compensation topologies based on IPOS and ISOP has tolerance misalignment capability under CV output.Secondly,the CC or CV output IPT compensation topologies which can be used for hybrid are determined.Furthermore,the obtained IPT compensation topologies are combined to obtain a series of hybrid IPT compensation topologies with high tolerance to pad misalignment and independent load output characteristics,and their output characteristics are analyzed.It can be known that the SS and LCC-LCC based hybrid IPT compensation topology using the ISOS structure is more suitable for CC output,while the LCC-S and S-LCC based hybrid IPT compensation topology using the ISOP structure is more suitable for CV output.Finally,the LCC-S and S-LCC based hybrid IPT compensation topology using the ISOP structure with CV output is analysed,and its load-independent output and high tolerance to pad misalignment are verified.Moreover,a general compensation parameter design method was proposed.Meanwhile,a1 k W experimental prototype was constructed,and the experimental results verify the theoretical analysis well.