Two‐/three‐coil hybrid topology and coil design for WPT system charging electric bicycles

Abstract

Wireless power transfer (WPT) for charging electric bicycles (EBs) can save people from tiresome plugging actions and avoid electrical shock hazards, especially in adverse weather. This study proposed a two-/three-coil hybrid topology to achieve constant current (CC) and constant voltage (CV) for charging EBs, simplifying control schemes. The system realises CC output with two-coil topology and operates in CV mode with three-coil topology by turning on a switch. Besides, an inductor array is used to compensate reactive power in CV mode when massive EBs are charged by one high-frequency inverter (HFI). The secondary side of the proposed topology is compact, and the number of components and HFI can be reduced. A coil design process based on double-D-type for the three-coil system is given, with the constraint of mutual inductances among three coils and limited size. To demonstrate the validity of the proposed methods, an experimental setup is built, and the performance of the two-/three-coil hybrid system indicates that the fluctuations of charging current and voltage are <0.64 and 2.12% in the whole charging profile. Moreover, the performance of two WPT chargers connected with one HFI hints that massive EBs can be charged with only one HFI.