A Dynamic WPT System With High Efficiency and High Power Factor for Electric Vehicles

Dynamic wireless power transfer (WPT) for charging electric vehicles (EVs) overcomes some of the problems associated with EVs battery size and weight as well as distance range limitation and long charging duration. High efficiency and fixed output voltage of WPT systems are of great importance for reducing operating cost and facilitating battery charging, respectively. On the other hand, utilizing the maximum power transfer capability of a WPT system leads to a capital cost saving of the system. In this article, the product of transferred power efficiency and input power factor (η·PF) is regarded as a criterion to make near full usage of the system power transfer capacity as well as reduce the capital and operating cost of the system. An optimal frequency-tracking method is proposed to maximize η·PF of the system taking into account possible abrupt changes in the coupling coefficient of the WPT system due to deviations of EV from alignment with the track along the road. In addition, the output voltage of the system is regulated simultaneously by an on-line adjustment of the primary inverter duty ratio. The optimal frequency-tracking method and voltage regulation are validated by extensive simulation and experimental results.