Analysis of Phase-Shift Control Method for Efficiency Optimization of Multi-Coil Wireless Power Transfer

Magnetic resonance wireless power transfer (MR-WPT) has been widely adopted due to its high efficiency over long distances. For fixed receiver (RX) coil positions, the power transfer efficiency (PTE) of multi-coil MR-WPT is maximized when all transmit (TX) coil currents are in-phase. In this paper, a phase-shift control method is presented which optimizes the TX coil phases for various TX-RX coil misalignments, to achieve high PTE. A graphical user interface (GUI) program is implemented which efficiently determines optimal phases to achieve maximum received voltage for each TX-RX coil distance. Experimental results indicate that the efficiency of multi-TX WPT with the proposed phase-shift control method is about 30% higher than the conventional MR-WPT system. Furthermore, with optimized phase shifts, the PTE of MR-WPT can still be enhanced even in close proximity to foreign metallic objects.