Efficiency Analysis and Optimization Method of Power-Relay IPT Systems for Reefer Containers

In order to get rid of plug-in/out actions for container terminals and to save space, a power-relay inductive power transfer system is employed for reefer container wireless charging. Besides, a load-power-based efficiency model is proposed to analyze system efficiency. The function of efficiency against the input voltage and the load power distributions of the system is analyzed in detail. Then, system efficiency can be improved by regulating the input voltage according to the input-voltage-lookup table, which is generated as per various power distributions of loads. Finally, a prototype with three loads is built to validate the performance of the proposed approach. The experimental results show that the efficiency is greater than 94.29% with an improvement by 7.6%, 7.2%, and 6.0%, compared with those without optimization (fixed input voltage 213 V) at one load (@80 W), two loads (@80 and 80 W), and three loads (@80, 80, and 80 W), respectively.