Load Current Control of One Pulsewidth Modulation for Dynamic Wireless Power Transfer System Using Vehicular AC Current Estimation

A wireless power transfer (WPT) system has been considered applicable to various charging applications. Dynamic WPT technology for electric vehicles limits communication speed and capacity due to the separation of assemblies between the ground and vehicle sides. It is challenging to communicate signals synchronized with the transmission frequency at the same timing. Hence, the system that controls the power only by the vehicle itself is necessary for the sake of safety. This article proposes a dynamic WPT system in which only the vehicle-side assembly acquires a synchronized signal and controls the load current to the battery. The theoretical analysis concludes that an input voltage derives an output ac current as a constant, and the one-pulsewidth modulation for a converter changes a load current. A feed-forward control method of its current estimation is proposed. The bench system is designed, constructed, and tested to verify the effectiveness of the proposed method compared with the proportional-integral control in a static state. Furthermore, the system is also verified when in motion. The load current was limited to the maximum value of the system in areas where the coupling coefficient is high, while the current value was well controlled in the other areas.