Efficiency-based design optimisation of a double-sided LCL compensated wireless power transfer system

The double-sided inductor–capacitor–inductor (DS-LCL) compensation topology has been extensively employed in wireless power transfer (WPT) systems owing to its advantages including zero voltage switching operation, constant current output, and no reactive power exchange between the primary and secondary sides. However, in most cases, equality of the primary and secondary coupling inductances is not optimal from the perspective of power transfer efficiency (PTE). This study presents an efficiency-based design optimisation method for DS-LCL compensated WPT system to obtain the highest PTE. The loss sources, as well as their impact on the PTE, are analysed. The analytical equivalent series resistance models of the efficiency-related loss sources are built and validated by practical measurements. The optimisation procedures are given as well. Two 1 A/200 W WPT prototypes are fabricated, tested, and compared, where one of them is designed in terms of the proposed optimisation method, whereas the other is designed in a conventional manner. The power loss on coupling coils of the optimised system is 7.49 W, 21.5% lower than that of the conventional system (9.54 W). The system overall efficiency is increased from 91.65% to 92.67% by utilising the proposed optimisation method.