Voltage transfer ratio analysis for multi-receiver resonant power transfer systems

The wireless power transfer characteristics of system architectures with single transmitter and multiple receiver coils are investigated. With multiple receivers in a limited space, couplings within receivers occur. Effective resonant frequency is changed due to such couplings, the desired working region should be adjusted accordingly. An equivalent circuit model is developed to describe the system with a single receiver, and extended to describe the system with two receivers. The circuit model yields transfer frequency responses that are in good agreement with experimental measurements over a range of frequencies that span the resonance. In a multi-receiver system, a method for tracking frequency shifts or retuning the lumped capacitance so as to maximise the efficiency is proposed. The simulation and experimental results well agree with the theoretical analysis.