Constant Current Charging and Transfer Efficiency Improvements for a Dynamic Wireless Charging System

Abstract

Dynamic Wireless Charging (DWC) systems for electric vehicles (EVs) are being studied and developed for wide applications. To ensure a long life for lithium-ion batteries, Constant Current (CC) charging is required. However, the equivalent load of the battery changes during CC charging, which reduces the system's efficiency. To solve that problem, this paper proposes a new control method that combines CC charging and improves transfer efficiency using only an active rectifier on the secondary side of the DWC system. Moreover, this study also proposes a method to estimate the coupling coefficient through the parameters measured on the secondary side without the need for wireless communication between the two sides. A model of a 1.5 kW DWC system with a transfer distance of 150 mm was built in a laboratory to verify the accuracy of the proposed method. The results showed that the charging current reached the required value, and the maximum system efficiency was 85%.