Frequency offset suppression method for wireless power transfer based on nonlinear resonant network

Abstract

In magnetically resonant wireless power transfer (MR-WPT) systems, transmitter, and receiver usually operate at the same resonant frequency. However, parameters of inductor, capacitor, or other components are susceptible to changes due to environmental factors and cause resonant frequency deviation. This would lead to decrease of transmission performance. To solve the problem, a wireless power transfer system based on a nonlinear compensation network is proposed to suppress frequency offset. The modeling of the nonlinear MR-WPT system is first established. On this basis, the mathematical equation of the equivalent nonlinear circuit is deduced and the amplitude-frequency response characteristics are analyzed. The influence of inductance parameter on the nonlinear characteristic is studied. Furthermore, the effects of excitation amplitude, compensation capacitance, load, and magnetic ring turns on the operating characteristics of the nonlinear resonant circuit are analyzed.The proposed nonlinear resonant wireless power transfer system is constructed and is experimentally studied. Compared with the traditional linear MR-WPT system, the results show that frequency offset can be effectively suppressed, which ensures efficient transmission performance with the proposed method. K E Y W O R D Samplitude-frequency response, frequency offset, nonlinear, transmission performance, wireless power transfer | INTRODUCTIONMagnetic resonant wireless power transfer (MR-WPT) is a promising technique with which energy can be transferred without electric wires. 1,2 This technique is based on the principle of magnetic field coupling and has the merit of good power supply flexibility. In recent years, MR-WPT has shown its potential in wireless charging of electric vehicles, medical equipment, underwater devices, household appliances, and other fields. [3][4][5][6] In order to obtain better transmission performance, resonant frequency of transmitter and receiver should be consistent with excitation frequency of the MR-WPT system. However, the resonant frequency of the resonator is easily affected by factors such as component aging, temperature change, or metal obstacles. [7][8][9][10] This would cause deviation of resonance frequency and leads to system detuning. Generally, linear resonators are used in most of the existing MR-WPT systems. 11 In order to improve the transmission performance under the frequency offset, frequency tracking detuning control strategy is applied, and deviated resonant frequency is tracked. 12,13 In previous works, 14 a MR-WPT