A Multiway Bidirectional Multiport-Ac-Coupled (MAC) Battery Balancer with Online Electrochemical Impedance Spectroscopy

Battery management systems (BMS) are key to various applications ranging from electric vehicles to grid-tied energy storage systems. Active battery balancers are needed for BMS in order to extend the battery lifetime and maintain high system performance. This paper presents a multiway bidirectional multiport-ac-coupled (MAC) battery balancer architecture based on a multi-active-bridge (MAB) converter. The operation, modeling, and power flow control of the MAC converter are detailed and analyzed. Magnetic models are used to further examine the multi-input multi-output (MIMO) power flow in the multi-winding transformer which couples all ports together. The converter is able to perform active battery balancing as well as online diagnostics through built-in electrochemical impedance spectroscopy (EIS). A 12-port MAC battery balancer was built and tested to verify the functionality and effectiveness of the proposed approach.