Suppression of Leakage Current in Wireless Charging Systems Using n-legged Inverters

An n-legged inverter for driving n-1 transmitter coils has been proposed to reduce the implementation costs of wireless power transfer (WPT) systems for the dynamic charging of electric vehicles (EVs). However, leakage current flowing through uncoupled coils deteriorates system efficiency and causes leakage electromagnetic interference (EMI). Suppression of leakage current by switching of legs not directly used for wireless charging is preferable as it requires no additional components. However, turning the unused legs off can be insufficient, while switching them identically to adjacent legs causes large switching losses and is potentially counterproductive. A novel switching method of unused legs is proposed to greatly suppress leakage current with limited losses.