Modeling and Optimization of Magnetically Coupled Resonant Wireless Power Transfer System With Varying Spatial Scales

Previous work reveals that the magnetically coupled resonant (MCR) wireless power transfer (WPT) technology is efficient and practical for mid-range wireless energy transmission, able to handle nontrivial amount of power. Due to the variable coupling coefficient under lateral misalignment and angular misalignment between transmitting coils and receiving coils, the output power and transmission efficiency will fluctuate, leading to instability of the system. This paper presented an equivalent analytical model for the MCR WPT system to incorporate spatial misalignments. The mutual inductance formulas were derived when receiving coils are laterally, angularly or generally misaligned from transmitting coils. The relationship among the output power, transmission efficiency, the mutual inductance, and load resistance were analyzed in detail. For the design of the MCR WPT system, it is necessary to seek optimal transmission performance under different applications. To achieve maximum output power and high stability of power transfer in a specific misalignments range, a normalization method based on the obtained analytical model was introduced, providing critical insight into the optimal design of coils. Relative design considerations and optimization procedures were further stated. Experiments had also been carried out to evaluate the accuracy of theoretical analysis and confirm the validity of the proposed optimization method.