抄録
Wireless charging technology for heavy-duty vehicles, such as electric buses, has been actively investigated with a view to accelerating deployment of an important form of eco-friendly transportation. Major standardization bodies recently chose the 85 kHz band as a global common frequency band for light-duty PHEV/EV, based on extensive studies on co-existence with other radio systems. The usage of the common 85 kHz band for a wireless charging system for heavy-duty vehicles would lead to rapid introduction of the wireless charging system while avoiding potential interference with other radio systems. We developed and evaluated a prototype wireless power transfer system for rapid charging of electric buses using the 85 kHz band. The rapid wireless charging system is composed of four components: a power transmission circuit generating 85 kHz band high-power signal from a commercial power source, two sets of transmit and receive charging pads that resonate in the 85 kHz band, a receive circuit that transfers 85 kHz band high-power signal to DC and charges the battery, and a control circuit that uses 2.4 GHz wireless LAN for communication. Achievement of the target by prototyping and evaluating this wireless charging system was confirmed: the maximum electric power received was 30 kW or more, the maximum misalignment tolerance of the transmit and the receive charging pads was +/-10 cm or more, and the longest transmission distance between the transmit and the receive charging pads was 12 cm or more.
