An Asymmetrical Loosely Coupled Transformer and Constant Current Wireless Charging Scheme for Warehouse Vehicles

Wireless power transfer (WPT) is the preferred charging method for battery-powered electric vehicles (EVs). In this paper, a novel WPT system with constant current charging capability is introduced for warehouse vehicles with lead-acid batteries. First, the schematic structure of the proposed system is discussed. A novel structure of asymmetrical loosely coupled transformer is designed to enable high-voltage feeding to low-voltage output and reduce the weight of the secondary side. Secondly, an optimized magnetic coupler using ferrite cores and magnetic shielding structure is proposed to ensure stable power transmission and high efficiency. Then, a dual-side independent control strategy on dual active bridge is proposed, aiming for maintaining constant charging current and high system efficiency. Finally, a 3kW inductive charging experimental platform is established to validate the theoretical analysis. Constant charging current of 45 A is achieved at the transmission distance of 50mm. The rated transferring power and system efficiency are 3 kW and 94.3%, respectively.