Research Of Misalignment Tolerance IPT System With Constant Voltage Output Based On Double Transmitter-side Coil Structure

Inductive Power Transfer(IPT)technology can realize power transfer without physical connection.It has been widely concerned and applied due to its convenience and safety compared with traditional plug-in charging method.However,in many situations,there always exists position misalignment between primary-side coil and secondary-side coil,which causes the variations of parameters of loosely coupled coils.This phenomenon can easily cause the change of output characteristics and the reduction of stability and practicability of IPT system.Therefore,with the development of IPT technology,it is necessary for researchers to improve the misalignment tolerance of IPT system.In order to solve this problem,this paper,in a practical way,designs a load-independent constant voltage(CV)output IPT system with double transmitter-side coils.Research on this novel topology proves that the misalignment tolerance is significantly improved.First of all,the proposed double transmitter-side IPT system is based on LCC-S compensation topology,which has been widely used in inductive IPT systems due to its constant coil current regardless of the load and the coupling coefficient.At the same time,this paper introduces two control parameters: the phase between two transmitter-side inverter bridges and the phase shift angle of the added inverter bridge φ.Based on this,first harmonic approximation(FHA)is used to analyze the CV output characteristic,the misalignment tolerant ability and input impedance condition.Time domain analysis(TDA)method is used to analyze the zero-voltage switching(ZVS)condition.Power losses are also analyzed by mathematical calculation.Secondly,the simulation model of the magnetic coupler with double transmitter-side coils are analyzed by using MAXWELL analyzing software.The structure of loosely coupled coils are built based on simulation results,and two tracks are attached to the secondary-side coil in order to realize the misalignment situation.After that,the variation data of coil parameters during the whole misalignment range can be easily obtained and the compensation parameters can be determined.Thirdly,according to the previous analyses,linear programming and parameter fitting are used as the mathematical method in order to find out the mathematical relationship between control parameters.On this basis,the closed-loop control trajectory is designed to achieve misalignment-independent CV output.The timing sequence of the control pulse width modulation(PWM)signal is also necessary to be clarified.Finally,an IPT platform with load-independent CV output based on double transmitterside coil structure is designed to analyze the misalignment tolerance performance.The air gap of the magnetic coupler is 100 mm,and the maximum transmission power is 3.3k W.Experimental results validate that the proposed approach has a great misalignment tolerance and efficiency performance.The maximum misalignment tolerance can be up to 50% of the coil size,and the fluctuation of the output voltage is less than 0.75% within the whole misalignment range,which is much better than conventional IPT system based on LCC-S topology.At the same time,high efficiency of the system can also be achieved.The maximum efficiency of the system at full-load condition is above 95.3% when misalignment occurs,and91.4% efficiency can still be maintained under 50% misalignment.Experimental results are consistent with theoretical analyses,which proves the effectiveness and practicability of the design method proposed in this research.