Efficiency Study of Vertical Distance Variations in Wireless Power Transfer for E-Mobility

A wireless power transfer (WPT) system is a safe, convenient, and smart charging solution for electric vehicle (EV) users. However, a drawback of the WPT systems is the reduced efficiency in comparison to the conventional wired charging due to lower coupling. Increasing the volume of EVs in the market and improving the system efficiency even by a few percent, besides being environmentally suitable, will benefit both consumers and distributors. According to the previous studies, efficiency improvement by decreasing the vertical distance (V-D) between transmitter (T-X) and receiver (R-X) coils has been one of the aims of the companies and universities. However, in low V-D, system performance becomes highly sensitive, due to the magnetic coupling strength. The focus of this paper is to analyze the effects of decreasing the vertical distances to WPT resonance tank efficiencies. Finally, some of the most significant parameters that affect the system efficiency at low V-D, such as the quality factor and the third harmonic interference, are analyzed and a mitigating approach is proposed.