Power Flow Control and ZVS Condition Analysis in Multiport Wireless Energy Router

This paper comprehensively analyzes the power transfer characteristics and soft-switching conditions of a multiport wireless power transfer system in the presence of cross-coupling, and proposes a port-equivalent method to address the relationship between power demands, soft switching conditions and the control variables. First, a system architecture with vertical stacking of coupling coils is presented and its power flow characteristics are analyzed. Then, based on a time-domain model of the system considering higher harmonics, the instantaneous currents at the switching moment of the power switches are derived and the soft switching conditions are analyzed. The relationship between output power and soft switching conditions are established, and a port-equivalent method is proposed to simplify the system analysis. Finally, a 76W one-to-three port prototype is built and used to verify the theoretical analysis.