A Multiport Converter for Flexible Active Balancing in Li-Ion Batteries

Abstract

Active balancing techniques have become increasingly popular for mitigating voltage mismatches in series-connected lithium-ion (Li-ion) batteries. These techniques outperform passive balancing in enhancing battery capacity as the battery ages, leading to an increased lifetime, especially in the electric transportation sector, where residual capacitance plays a crucial role in determining battery lifespan. This study proposes a circuit configuration that utilizes a multiport active half-bridge converter for active cell balancing. The proposed method offers a high degree of flexibility owing to multiple operating modes and a relatively straightforward circuit configuration. Based on the state of charge of each cell, bidirectional power flow can be controlled between two or more arbitrary cells or between the entire battery string and a group of batteries. The proposed approach has been experimentally validated in a battery pack of seven Li-ion cells.