Research Of The Misalignment Tolerance Static Wireless Charging System Employing Double-sided LCC Topology

Wireless Power Transfer(WPT)is an ideal power supply mode and it has been developing rapidly and widely used in recent years for the advantages of high security,large charging range and good controllable performance.But at the same time,in the practical WPT system,the objective existence of position misalignment between the transmitting coil and the receiving coil will change the coupling coefficient of the system,which leads to large fluctuation of the output power,while reducing the reliability of the wireless charging system.Therefore,when the WPT system is designed,it is necessary to improve the misalignment tolerance of the system to achieve high stability and robustness,which can transmit power smoothly within a certain range of coupling coefficient.To solve the above question,this paper focuses on the methods to improve the misalignment tolerance of the system and realize the static constant current wireless charging in the case of large coupling coefficient variation from the perspective of smoothing the transmission power.First of all,this paper introduces the four basic resonant topologies of WPT system,and analyzes the circuit characteristics of series-series resonant topology by constructing mutual inductance coupling model to study the influence of the coupling coefficient variation on the output power and efficiency of the system,pointing out the poor performance of series-series resonant topology on misalignment tolerance.Then this paper introduces the double-sided LCC topology and analyzes the output power characteristics of this topology to study the parameters design method and mechanism of misalignment tolerance,based on that,the parameter relation that meets the misalignment tolerance characteristic is deduced compared to series-series topology on the purpose of smoothing the transmission power.Meanwhile,the influences of the parameter value on the misalignment tolerance range and rated output power are analyzed,taking the above two factors into consideration as constraint condition synthetically and according to the variation range of coupling coefficient,a comprehensive parameter optimization design method is proposed to improve the performance of the system.Secondly,by applying the secondary constant current control strategy based on the Buck converter,the relationships between the coupling coefficient of three topologies(series-series,LCC-S,double-sided LCC)and the duty cycle of the Buck converter are analyzed when the constant current output is realized under the same input voltage condition,and it is proved that the double-side LCC topology can improve the comprehensive performance of the system both on misalignment tolerance and rated output power raising.A simulation model of static constant current wireless charging system based on double-sided LCC topology is built by Simulink software,and the simulation results agree with the theoretical analysis.Finally,a wireless power transfer experimental platform is designed to analyze and compare the comprehensive performances of the three topologes.The results of the experiment show that when the coupling coefficient of the system changes 24% from the rated value,the power fluctuation of the double-sided LCC topology is less than 12%,which is far lower than the series-series topology under the same condition,and the rated power is raised by 54%,while the efficiency of the system is above 89% which is also higher than the series-series topology with an inherent current limiting ability under no-load operation.Based on that,the closed loop control circuit is added to the above experimental installation to build a constant current wireless charging system based on double-sided LCC topology,the system can achieve the constant control of 1.4A for the equivalent load of 8.5?,10? and 12? when the coupling coefficient varies 200% from 0.17 to 0.34.