A Novel Reconfigurable Inductive Power Transfer System with Pulse Density Modulation for Constant Current and Constant Voltage Charging Applications

Owing to the dependence on coil characteristics, loading profile, and operating frequency in inductive power transfer (IPT) systems, it is difficult to design a charger that provides the electric vehicle (EV) battery with the required constant current (CC) or constant voltage (CV) efficiently over a pre-defined charging profile. Furthermore, existing IPT systems that use CC-CV charging cause power loss due to hard switching or require additional reactive power due to variable frequency control. Recently, automotive manufacturers have moved to 800 V battery pack architectures due to significant EV weight reduction and shorter charging time. To address these concerns, this paper introduces a novel reconfigurable IPT system that charges 400 V and 800 V battery packs with enhanced efficiency and a smooth CC-CV charging profile. It only uses three coils and two relays that can be switched to series series-series (SS-S) topology for CC output and inductor-capacitor-inductor-series (LCL-S) compensation for CV output with relay 1 and a reconfigurable system to charge the 400 V and 800 V battery packs with configuration of relay 2. Additionally, pulse density modulation (PDM) is adopted for this topology to increase IPT's efficiency by achieving the soft switching capability over a wide voltage range. Simulation studies are carried out on a designed 3.3 kW IPT charging system under CC and CV charging profiles at 400 V and 800 V to verify the feasibility of the proposed reconfigurable topology with the PDM method.