A splitting‐coil‐based IPT system of reefer container for high efficiency wireless charing

Abstract

To eliminate the plug-in/out actions for automatic wharves, a splitting-coil-based inductive power transfer (IPT) system is proposed to improve transfer efficiency for reefer container wireless charging. Firstly, the power requirement of a reefer container only hits a few operation points and each operation point is in correspondence to an individual resistance point (IRP); secondly, the maximum efficiency of an IPT system can be achieved with the optimal load resistance (OLR). Therefore, the system efficiency can be improved by transforming the OLR into or near the IRPs. The idea of this work is to create double OLRs of the system by altering the splitting coils operating in parallel mode or series mode with switches, then to select the proper OLRs to match the IRPs for efficiency improvement. A 0.54 kW prototype was built to validate the performance of the proposed approach. The results indicate that with the proposed method, the system can maintain the system efficiency >90.7% from 14 Ω (0.54 kW) to 60 Ω (0.13 kW), with an improvement of 7.0% at most compared with that of the system without the optimisation in the same load resistance range.