EMI Reduction Techniques from 100 kW Wireless Charging Systems for Heavy-Duty Vehicles

Wireless power transfer (WPT) is a useful technology for vehicle charging. Transfer power above 100 kW is needed for rapid charging of heavy-duty vehicles such as electric buses. One of the issues of WPT systems is electromagnetic interference that affects radio services. Limits of radiated disturbances from WPT systems are specified in CISPR 11 and the Radio Act of Japan. In this study, a 100-kW-class WPT system was constructed with the aim of reducing the radiated magnetic field strength. Opposite-phase transfer and frequency hopping spread spectrum were implemented to reduce the fundamental frequency. Low-pass filters were applied to decrease the harmonic frequency. A 10-m anechoic chamber was used to measure the radiated magnetic field strength of this WPT system. The results confirmed the compatibility of the three proposed techniques. The radiated magnetic field strength of the constructed WPT system was below the limit set by the Radio Act of Japan.