Frequency drift insensitive broadband wireless power transfer system

The resonant frequency of coils in a four-coil magnetic coupling resonance wireless power transfer (MCRWPT) system has a direct impact on transfer coefficient. For efficient power transfer, most of the systems operate at high-Q resonant state, causing a narrow bandwidth and reducing the system tolerance to resonant frequency deviation. To deal with the problem, a four-coil MCR-WPT system characterized with broadband performance is investigated. Based on the equivalent circuit, the transfer coefficient and the input impedance are firstly calculated. The transfer characteristic at different resonant frequency under different transfer distances is discussed. By comparing the number and variance of the extreme values of transfer coefficient under different resonant frequencies, the resonant frequency for excellent broadband transmission is determined. To validate the broadband performance, frequency drift caused by capacitance variations is investigated at the resonant frequency of 19 MHz under the transfer distance of 45 mm. The results indicate that the MRC-WPT system generally maintains broadband transmission and the transfer coefficient at the excitation frequency of 19 MHz remains above 0.9 when the resonant frequency is deviated. Experiments have been performed to validate the excellent broadband performance. The results are generally consistent with the simulation analysis. (C) 2020 Elsevier GmbH. All rights reserved.