Single-step phase control method under cross-coupling between transmitting coils for omnidirectional wireless power transfer

Abstract

This paper introduces a single-step phase control method to mitigate cross-coupling between transmitting (TX) coils in an omnidirectional wireless power transfer (OWPT) system. In OWPT systems, achieving zero cross-coupling is challenging due to slight variations in coil dimensions. Although the cross-coupling value may appear small, it can significantly impact transfer efficiency because the coupling coefficient between the TX and receiving (RX) coils is inherently low in OWPT systems. Consequently, this cross-coupling induces errors in TX currents and degrades efficiency. The proposed method compensates for TX current errors by adjusting the inverter phase in a single step using a superposition-based model, thereby enhancing efficiency. To validate the proposed method, we implemented an OWPT system consisting of three-orthogonal TX coils (150 mm in diameter) and a 60 × 70 mm2 planar RX coil operating at 6.78 MHz. Experimental results demonstrate that the proposed method, by adjusting the phase in a single step, achieves maximum efficiency and improves overall efficiency by more than 5.8%.