A Three-Resonator Wireless Power Transfer System With Constant-Output Feature Within a Misalignment Range

The magnetic coupling of a practical wireless power transfer (WPT) system is greatly influenced by the variations in the alignment of the magnetic couplers. For a given coupling range, a WPT system is expected to output the required rated power with a given load. However, this requirement cannot be easily met by the widely adopted series–series or inductor–capacitor–capacitor compensation topologies in a conventional two-resonator WPT system. This article proposes a design methodology for three-resonator WPT systems to achieve a constant output power in a wide coupling range. The basic characteristics of the three-resonator WPT system are reviewed and the proposed design methodology is presented in detail. A 3.3-kW three-resonator WPT prototype is designed and built, achieving nearly constant output in the given misalignment range. The measured dc–dc efficiency of the prototype reaches 94.47$\%$ at the rated power.