Efficient modeling of multi-coil wireless power transfer systems using combination of full-wave simulation and equivalent circuit modeling

Wireless power transfer (WPT) systems have proven to be very efficient for short-range and mid-range distances, but the transmission efficiency reduces rapidly when the distance is increasing. Multi-coil design based on magnetic resonance can be used to improve the efficiency when the distance is larger than 10 times the diameter of the coils. However, it takes a long computation time when analyzing WPT systems consisting of multiple coils in full-wave simulations. In this paper, a combination of equivalent circuit modeling (ECM) and 3D full-wave modeling based on the method of moments (MoM) is proposed to reduce the calculation time from days to minutes on a today's PC while the calculation accuracy remains acceptable. An optimization of a multi-coil WPT system is carried out with the proposed technique. For long transmission distances, the highest efficiency can be obtained with multiple coils of the same size and an optimum number along the transmission distance. It has to be ensured that the pitch between adjacent coils is equal to the diameter of the coils.