Receiver-Position-Based Unbalanced-Current Control for a Three- to Single-Phase Wireless Power Transfer System for AGVs

Conventionally, three-phase wireless power transfer systems apply balanced currents with open-loop control. The balanced current enables the receiver coil to receive uniform power regardless of its position. The phase coil away from the receiver coil, however, dissipates the same power as that close to the receiver coil while the far phase-coil contributes to little power transfer. This article presents a receiver-position-based unbalanced-current control. In the unbalanced-current control, a close phase-coil has higher current amplitude than far phase-coils. Therefore, the proposed control can improve the transfer efficiency in comparison with the system with the balanced-current control. The proposed control can dynamically estimate a moving receiver position with the voltage and current in the three-phase inverter and can generate required currents owing to its feedback control. The experiments using the system with a prototype of three- to single-phase wireless power transfer coil and a fabricated inverter implementing the proposed control prove that the system can dynamically transfer uniform power to a moving automatic guided vehicle and can perform with 5% improvement in transfer efficiency in comparison with a system implementing the balanced-current control.