Phase-Shift Controlled Multilevel Bidirectional DC/DC Converter: A Novel Solution to Battery Charge Equalization in Fuel Cell Vehicle

Series-connected battery pack is one of the most economic and significant element within a fuel cell vehicle energy storage system. It provides fast dynamic response for electric drive train and handles regenerative power efficiently. Battery charge equalization has to be considered in the battery management system design because of its important influence on the battery life, uniform state of charge of battery packs can also enhance the battery-string performance. In urban drive cycles, battery string need to be frequently discharged and charged, which brings up another challenge for battery charger in fast charging. This paper presents a novel multi-level bi-directional DC/DC converter with phase-shifted charging control algorithm, which is capable of providing balanced fast charging of battery string in fuel cell vehicle applications. The basic operation mode of the converter/charger is presented, charge equalization and fast charging algorithm is discussed and simulated.