Optimized Design of Passive Array Coils for High-Efficiency and Anti-Misalignment WPT System

Mid-range wireless power transfer (WPT) system for consumer electronics has been hamstrung by modest energy efficiencies and low misalignment tolerance. As the increase in transfer distance, the increasing leakage magnetic flux between transmitting (Tx) coil and receiving (Rx) will deteriorate the system performance. In this paper, a novel optimization-based design method of passive array coils (PACs) is presented in order to maximize the power transfer efficiency (PTE) and improve the misalignment tolerance in WPT system. A modified multiobjective genetic algorithm is implemented to optimize parameters of PACs in consideration of PTE, displacement flexibility (DF) and volume of PACs. Moreover, a parameter design scheme for compensation network, namely S-Ss-S topology for co-planar multiple coils is investigated, which can achieve zero phase angle (ZPA) in primary side and enhance power factor. Finally, the reasonable prototype of the proposed WPT system with PACs is designed, fabricated and tested. The experimental results show that the proposed structure can increase the efficiency by almost 50% over the system without PACs at 400 mm distance and deliver almost 40 W of output power. Moreover, the PTE and output power can still remain stable under large lateral misalignment with PACs.