In wireless power transfer (WPT) systems, lateral misalignment between coils can lead to substantial fluctuations in transmission efficiency. Although various misalignment-tolerant coil structures have been proposed, many still face challenges in maintaining high transmission efficiency under displacement conditions. To overcome these limitations, this paper propose a novel interwoven magnetic field (IMF) coil structure that simultaneously achieves strong magnetic coupling and enhanced misalignment tolerance. The proposed IMF structure partitions the transmitting coil into two functional components: a primary transmitting coil configured as a Double-D (DD) coil, and auxiliary compensating coils implemented as bipolar (BP) coils symmetrically placed on both sides of the DD coil. The receiving side employs a reverse-series connection coil configuration. The IMF structure benefits from the inherently high coupling efficiency of DD coils relative to conventional single coils for the same footprint, while the BP coils provide edge compensation. This configuration enables the system to sustain high efficiency even under coil displacement. Specifically, when lateral misalignment occurs along the direction of vehicle motion, the magnetic interaction between the reverse-series receiving coil and the edge-positioned BP coils adaptively compensates for the misalignment, thereby preserving the stability of the system of transmission efficiency. Under a horizontal misalignment along the Y-axis corresponding to 50% of the transmitter coil length (394 mm), the IMF system exhibits a maximum transmission efficiency fluctuation rate of only 0.21%, while achieving a peak efficiency of 97.16%.

In dynamic wireless power transfer systems for smart rail trains, a high fluctuation rate of mutual inductance leads to reduced efficiency when an offset occurs between the transmitting and receiving coils. This paper explores the mutual inductance characteristics and the variation rule of magnetic induction strength between the transmitting coil and the receiving coil at offset. And proposes an I-shape coil structure. The I-shape coil structure has good anti-offset performance in the direction of motion, and the maximum offset distance is up to 1.2 times the outer length of the transmitting coil. First, the mutual inductance characteristics of this I-shape coil structure are investigated based on the coupling mechanism of the I-coil. Meanwhile, a mutual inductance optimization method is proposed, which is used to obtain the values of each coil parameter that satisfy the requirements. Secondly, the magnetic core optimization of the I-coil structure has been carried out to achieve higher mutual inductance and better transmission efficiency. Finally, a wireless power transfer system is constructed based on the obtained coil and magnetic core parameters. Simulation and experimental tests are carried out for this coil structure and the coil structure with magnetic core, respectively. The experimental results verify the rationality and correctness of the structure. The results show that the maximum mutual inductance fluctuation rate is only 4.97% in the coil structure without magnetic cores with the offset distance between the transmitting and receiving coils at 120% of the outer edge length of the transmitting coil. With the addition of the magnetic core, the maximum mutual inductance fluctuation is only 5.02% with an efficiency of 97.61% at an offset distance between the transmitting and receiving coils of 120% (50.8 cm) of the outer edge length of the transmitting coil.