This article presents an extended hybrid modulation (EHM) technique to achieve multistage constant-current (MSCC) charging of electric vehicles using wireless power transfer (WPT) technology. Although most research focuses on constant-current constant-voltage charging, MSCC charging offers key advantages, such as lower temperature rise, decreased charging time, and prolonged battery lifespan. However, the existing phase-shift-modulation (PSM) method encounters substantial circulating reactive power and significant efficiency drops in MSCC charging. To overcome this, an EHM strategy is proposed to expand the modulation range of PSM. By applying EHM to both the inverter and active rectifier, the proposed method provides up to 16 operating modes to facilitate multiple CC outputs. Furthermore, an optimal mode trajectory, specifically designed for the MSCC charging, is developed. By implementing this trajectory across different charging stages, zero-voltage-switching is achieved for all power switches, and the overall power loss of the system is minimized. Finally, a WPT prototype was developed to validate the proposed approach. Experimental results demonstrate that the proposed approach effectively enables the MSCC charging while notably enhancing transmission efficiency, achieving dc-to-dc efficiencies between 92.45% and 95.67% across a power range of 231 to 3.015 kW.

In electric vehicle (EV) charging stations, a common approach to charge multiple EVs is to utilize a shared DC bus for all the converters. However, as the scale of the station grows, this method leads to increased complexity and higher expenses due to the growing number of components. This paper proposes a novel AC multiplexed wireless power transfer (WPT) topology, in which charging modules are connected in parallel on the AC side of a single converter via a highly coupled multi-winding transformer. This topology reduces costs and enables multidirectional power flow for V2X (vehicle-to-vehicle and vehicle-to-grid) applications. In this paper, a comprehensive introduction to the AC multiplexed WPT system is presented, followed by an analysis of its multidirectional power flow characteristics. Finally, a three-port prototype was developed to validate theoretical analysis.