Characteristic Study Of Tuned Capacitor In IPT System Based On Impedance-matching Theory

As an important branch of the wireless power transfer system, inductively power transfer(IPT) technology has broad application prospects. inductively power transfer technology is the use of electromagnetic induction principle to realize wireless transmission of electrical energy, which have the characteristics of safety and high sensitivity, which is widely used in electric cars, household appliances, consumer electronics and other fields.For wireless charging of electric cars, mutual inductance due to the distance to the ground different system parameters change. For household appliances power supply platform, the different power levels of electrical lead to changes in the load of the system parameters. This will result in changes of the work frequency of the system, reduce transmission power and efficiency of the system.In this paper, when the induction power transmission system parameters(mutua l inductance parameters and load, etc.) change, to ensure the system resonance frequency stability problem. Based on high order nonlinear characteristics of the induction power transmission system, its work frequency point is not the only one in the state of soft switch. When the system is working in a soft switch work point, the system has the highest transmission power and efficiency. Therefore, when the system parameter changes, it need to ensure the stable operation of induction power transmission system in this work frequency point.Therefore, the change of the system parameters lead to impedance mismatch and work frequency drift. By dynamically adjusting the parameters of the resonance circuit(inductor, capacitor) make the system impedance matching, to ensure the stability of the system work frequency. The existing dynamic tuning method(phase inductance tuning method and simple parallel capacitor array tuning method) principle is analyzed. Among them, compensating capacitance of simple parallel capacitor array is increased on the basis of the reference capacitance, and the size and control difficulty of capacitor array is increasing with the equivalent capacitance range and accuracy requirement enhance.In this paper, complex hybrid capacitor array structure instead of a simple parallel capacitor array solve the problem of only increased on the basis of the reference capacitance. And the number of capacitance, range, accuracy of basic capacitance module of complex hybrid capacitor array has analyzed. Then three capacitance module is put forward by using a small amount of capacitance equivalent capacitance to output large range and high precision, to improve the stability of the system. When wide power levels of load changes, to meet the output equivalent capacitance value range and precision requirement, hybrid structure three capacitor array is put forward based on the three capacitance module. Finally, the three modules of capacitance values is optimized by using the genetic algorithm in the genetic algorithm toolbox of MATLAB environme nt. The validity of the three capacitance module has verified in the output of the equiva le nt capacitance value range and the precision. At last, there is a simulation study based on the model of SP-type IPT system by Simulink, when the load switch, the system work frequency has stabilized by dynamically tuning capacitor array.