A Multiload Inductive Power Transfer Repeater System With Constant Load Current Characteristics

In this article, an inductive power transfer (IPT) system is designed to power multiple loads with nearly constant load currents using repeater coils. In the proposed IPT repeater system, every two repeater coils are grouped into a repeater unit and the load is connected to the first repeater coil in each repeater unit. It is deduced that the constant load current can be obtained when only considering the coupling coefficients between any two adjacent coils and omitting the coil resistances. Thus, the load power can be regulated independently, which greatly simplifies the power control design. A feasible magnetic structure is designed to meet the requirement that the coupling coefficients between the nonadjacent coils can be omitted. The relationship between the load resistances to achieve equal power distribution when considering coil resistances is derived. The proposed IPT system can be used to power gate drivers of the multiple submodules (SMs) that are connected in series in the modular multilevel converter (MMC). An experimental setup with six loads is constructed where the distance between two adjacent repeater units is 65 mm. The maximum system efficiency is around 60%.