Dynamic Wireless Power Transfer System for Electric Vehicle to Simplify Ground Facilities - Power Control Based on Vehicle-side Information -

Electric vehicles (EVs) have environmental advantages and the capacity for advanced motion control. However, EVs need to be charged frequently due to their limited mileage per charge. A dynamic wireless power transfer (WPT) system for EVs can extend their cruising distance and reduce the size of their energy storage system. However, when being applied to rugged roadways over long distances, it is important to simplify ground facilities as much as possible. While it is practical for a static system to control both side using communication, a dynamic system for EVs should be controlled only on the vehicle-side. To implement a suitable control system, this paper focuses on vehicle-side control for achieving a required power and proposes a control method based on road-side voltage estimation using only vehicle-side information. Conventional methods have proposed voltage control using a DC-DC converter on the vehicle-side while road-side voltage is regulated to obtain a reference value. However, this causes ground facilities to become complicated due to a need for a feedback system. The proposed method estimates roadside voltage, therefore eliminating the need for its regulation. As a result, ground facilities can be simplified. The estimation equation is based on the equivalent circuit of a WPT system and expressed as a function of vehicle-side voltage and current. The reference value and the equilibrium point of the DC-DC converter can be obtained by the estimated road-side voltage. Therefore, the power control system with a voltage controller can be designed. The estimation equation and the power control are verified by experiments. These results suggest that the proposed method can achieve the required power without controlling the road-side or communicating between a vehicle and ground facilities.