Multibattery Charger System Based on a Three-Level Dual-Active-Bridge Power Converter

A charger for two batteries connected in series is presented in this work. From the three-phase grid, the batteries are charged through a three-level neutral-point-clamped ac-dc converter in cascade with a three-level dual active bridge converter. The system provides galvanic isolation and allows bidirectional power flow. A simple control strategy to charge the batteries is presented, based on the regulation of the common-and differential-mode components of the batteries’ charging currents. With this control approach, each battery bank can be charged independently, allowing it to reach full battery bank capacity, even under different battery initial state-of-charge values or different battery nominal capacities. Moreover, the proposed control system also regulates the total dc-link voltage and the dc-link voltage balance in both dc-links of the system. The simulation results verify the feasibility of the proposed implementation and control system approach.