Modular, Scalable Battery Systems with Integrated Cell Balancing and DC Bus Power Processing

摘要

Traditional electric vehicle and stationary battery systems use series-connected battery packs that employ centralized battery management and power processing architecture. Though, these systems meet the basic safety and power requirements with a simple hardware structure, the approach results in a battery pack that is energy and power limited by weak cells throughout life and most importantly at end-of-life. The applications of battery systems can benefit significantly from modular, scalable battery systems capable of advanced cell balancing, efficient power processing, and cost gains via reuse beyond first-use application. This thesis considers the requirements imposed by electric vehicle and stationary applications and presents a modular battery system architecture, including design, modeling and control methods, to overcome challenges associated with conventional systems. The modular battery system uses power converters to combine battery balancing and power processing functionality and opens the door to new opportunities for advanced cell balancing methods. With this approach, the power converters can achieve system cost and efficiency gains by replacing or eliminating some of the conventional components inside battery systems. In addition, when coupled with life prognostic based cell balancing control, the modular system can extend the lifetime of a battery pack by up to 40%. The design and control concepts developed in this thesis can be applied to designs of large battery packs and improve battery pack performance, lifetime, size, and cost.