Circulating Current Modeling in Multi-Transmitter Inductive Wireless Power Transfer System

A multi-transmitter structure with LCC compensation is widely utilized in wireless power transfer (WPT) systems to ensure stable output over a board range. Turning off the transmitting coils with low coupling coefficients is usually necessary to improve overall efficiency. However, due to the inevitable coupling between the transmitting and receiving coils, an induced current will also be generated in the deactivated transmitting coils. This paper accurately models the current of deactivated coils and the circulating current between the TX coils. The result indicates that the current in the deactivated coil has a similar amplitude to that in the activated coils but is phase- inverted, leading to additional losses and a reduction in the maximum output power of the system. Simulations and experiments have verified the accuracy of the modeling.