Analysis of Wireless Power Transfer System Employing Active Shielding with Virtual Inductance and Two-port Equivalent Circuit

This paper proposes and analyzes an active-shielding method to reduce EMF of wireless power transfer (WPT) systems. Additional power supplies and two windings cancel magnetic field generated by the WPT coils with only reactive power. The advantage of the proposed method is that the capacity of the additional power supplies are small. The parameter variation of the WPT coils and the magnetic field are calculated with a two-port equivalent circuit which the additional power supplies are replaced to virtual inductance in. As a result, the magnetic field decreases by 27.2dB with the proposed method. In addition, the transmitting power is increased as the magnetic field becomes smaller because the equivalent mutual inductance is reduced.