Wireless power transfer (WPT) technology has garnered widespread attention in recent years due to its advantages in safety, reliability, and flexibility. However, these benefits are often dependent on the precise alignment of the coupling mechanism. In practical applications, as perfect alignment cannot always be ensured, misalignment leads to a reduction in the coupling coefficient, significantly degrading transmission efficiency and system performance. Traditional flat solenoid coils perform well in resisting longitudinal misalignment, but when lateral misalignment occurs, especially near the coil's edge, the coupling coefficient and efficiency drop rapidly. To address this issue, this paper proposes an improved flat solenoid coil WPT system.

First, an equivalent model of the LCC/S compensation circuit is established to analyze the effects of circuit parameters on output characteristics, and a method for configuring the parameters of resonant elements is derived, revealing key circuit parameters affecting voltage gain. Then, an equivalent magnetic circuit model is built to analyze the magnetic field distribution characteristics of the coil, demonstrating that core shape and winding configuration significantly influence the coupling coefficient. Consequently, an optimized winding distribution is proposed using an arithmetic progression for the inter-turn spacing, and the specific optimization process is provided. Additionally, the core shape of the transmitter coil in the traditional flat solenoid design is improved to better concentrate the magnetic field lines, enhancing magnetic field uniformity and increasing the misalignment tolerance of the coupling mechanism.

To verify the optimization effects, multiple simulation models were created with core shape and winding configuration as variables for comparison. Finite element simulation results show that the improved transmitter core achieves more uniform magnetic flux density distribution, significantly reducing the rate of change in the coupling coefficient. Magnetic field uniformity and misalignment tolerance are markedly improved. Finally, a 100 W WPT system prototype was built, and thermal imaging was used to analyze the system’s loss distribution.

Experimental results show that when the receiver is laterally misaligned within ±50% in both the X and Y directions, the output voltage fluctuation is controlled within 5%, and transmission efficiency reaches 89%. These results validate the effectiveness and feasibility of the proposed system.