Cavity Resonator-Based WPT System Utilizing Rotating Magnetic Field for Omnidirectional Charging

Compared to traditional inductive wireless power transfer (WPT) technology, quasi-static cavity resonator-based WPT (QSCR-WPT) systems can significantly inhibit transmission efficiency deterioration within room-scale space. However, a conductive pole is required generally in the middle of the cavity for a uniform magnetic field. Besides, changes in receiver angles may cause fluctuations in efficiency and output power. To address these issues, a dual-excitation method is introduced to modulate a rotating magnetic field with uniform magnetic distribution and controllable direction in a QSCR-WPT system. This particular magnetic field configuration is referred to as the Ubiquitous Magnetic Field with Pole-Independent (UMPI) mode in this paper. Compared to the PD and PI modes reported in existing research, the UMPI mode exhibits superior tolerance to both angular and positional variations. Furthermore, the equivalent circuit model of the resonant cavity is established and the electrical parameters between the coil and the resonant cavity are derived for the first time using the reflected impedance equation. Finally, experimental results indicate that the receiver achieves full-angle wireless charging coverage in the majority of spatial locations within the cavity (Over 90% of space).