Research On A Family Of Universal IPT Couplers With High Tolerance To Pad Misalignment

To realize the efficient and reliable inductive power transfer(IPT)system,primary and secondary pads should be well aligned.However,it is inevitable with pad misalignment in many practical IPT applications.Therefore,the IPT system should tolerate pad misalignment to a certain extent to meet the design requirements of output power and transmission efficiency.At present,in order to achieve a certain tolerance to pad misalignment,the magnetic field distribution between primary and secondary coils can be improved by designing magnetic coupler to mitigate the change of coupling coefficient during pad misalignment.However,the coupler design is usually complex and the misalignment tolerance is poor.In addition,an approach is to deploy two IPT topologies having opposite trends in output variation to pad misalignment,forming a hybrid IPT converter that improves the pad misalignment tolerance.However,these topologies need to be selected according to output characteristics,which is not universal and usually incursa higher component count.To solve above issues,in this article,a hybrid IPT coupler,which combine a four-coil bipolar coupler and a simple series–series(S-S)topology,is proposed to achieve high tolerance to pad misalignment.The proposed hybrid IPT coupler also has over-current protection,which is applicable all IPT compensation topologies.In this paper,based on two-port network theory,the equivalent model of the hybrid IPT coupler and its construction principle and method are studied.Besides,whose characteristics of the mutual inductance and over-current protection are analyzed.The hybrid IPT coupler is applied to an S-LCC compensation topology with load independent output constant voltage(CV)and input zero-phase angle(ZPA),so that the IPT system can realize output CV and input ZPA to tolerate pad misalignment.Then,a 3-k W IPT prototype using the hybrid coupler and the S-LCC topology is built to verify the analytical findings.In order to design the BP coupler briefly,an improved IPT coupler is further proposed in this paper.The improved IPT coupler still adopts a BP coupler,but the compensation network adopts a higher order structure of parallel-series-series(PS-S)or series-series-parallel(S-SP)than S-S structure.Although a compensation element is added,it also has high misalignment tolerance and is suitable for any IPT compensation topology.The compensation element selection and parameter design method of PS-S or S-SP structure are analyzed in detail,and the improved IPT coupler is applied to an S-S compensation topology,so that a 3-k W IPT prototype is built.The IPT system can output constant current and input ZPA to tolerate pad misalignment and load variation.Experimental results well verify the theoretical analysis.