Splitting Coils in Energy Storage and Wireless Power Transfer Systems: Analysis, Comparison and Solution

Wireless power transfer has become an increasingly widespread technology in electric vehicle and charging-system applications. Advances in power electronics have led to significant improvements in system efficiency, and in parallel, extensive research has been conducted on energy storage technologies and coil designs. In this study, a split-coil structure using a dual inverter system is analyzed, aiming to achieve a flatter magnetic-flux distribution for electric vehicle charging systems and battery energy storage circuits or an increase in total flux density for power applications. A flatter flux distribution will make a significant improvement in electric vehicle charging systems under misalignment conditions. The key point based on these concepts is the dually driven split coil, which is analyzed as both a single-layer and a double-layer coil. The main objective of the present study is to investigate the magnetic-flux distribution and the performance of the proposed fully symmetric two-layer coil structure under nominally aligned conditions. Owing to the fully symmetric geometry, the presented one-dimensional magnetic-flux scan is sufficient for comparing the flux-distribution characteristics of the proposed and conventional coil structures. Following the demonstration that the single-layer split coil design was ineffective, theoretical analyses and experimental data indicate that the double-layer split-coil design provides 10% higher efficiency.