Improving the Life, Safety and Capacity of Lithium-ion Batteries with Power Electronics Based Solutions

Lithium-ion batteries are considered as the only viable energy storage solution for the large deployment of plug-in hybrid electric vehicles (PHEV). The main issues of lithium-ion batteries include capacity fade, cycle life, and safety. The safety and longevity issues are significantly magnified in large battery systems used in PHEV and renewable energy systems. Much of the work at the present time is focused on battery chemistry and manufacturing process improvement. However, these issues can be effectively addressed from the control and management perspective, with a power electronics based solution. This presentation discusses the management of lithium-ion battery systems aimed at improving battery life, available capacity, battery safety and reliability with power electronics based solutions.

The power electronics based solutions use isolated charge architecture to provide effective and safe cell-balancing during charge with reduced charging time, and a dynamic balance circuit during discharge to utilize all the cell energy available. Every cell tightly balances during charge and discharge in any combination of rows, modules, arrays, or strings of batteries. An effective thermal design and management are included to extend battery life, along with health monitoring, fault detection and fault isolation. Additional features of the system include conditioning vehicle system with a bidirectional converter for cold weather performance improvement. A number of fundamental issues were identified in the research, including dual phase-shift algorithm, advanced control that combines online parameter identification and dead-band compensation, and a framework for the research of short timescale transients in high power converters.
Dr. Chris Mi is Associate Professor of Electrical and Computer Engineering and Director of DTE Power Electronics Laboratory at the University of Michigan-Dearborn, Michigan, USA. His research interests are in power electronics, electric machines, and their applications in hybrid electric vehicles and renewable energy systems. He has taught tutorials and led seminars on the subject of HEV/PHEV for the Society of Automotive Engineers (SAE), the IEEE, NSF funded workshops, and National Society of Professional Engineers (NSPE). He delivered the HEV course to major automotive OEMs and suppliers, including GM, Ford, Chrysler, A&T Technology, GE, and Delphi. He has offered the tutorial in five countries, including the US, China, Korea, Singapore, and Mexico. He has published more than 90 referred articles and delivered 30 invited talks and keynote speeches, and served as panelists.

Dr. Mi is the recipient of the 2009 Distinguished Research Award of the University of Michigan-Dearborn, 2007 SAE Environmental Excellence in Transportation (E2T) Award for “Innovative Education and Training Program in Electric, Hybrid and Fuel Cell Vehicles,” the 2005 Distinguished Teaching Award of the University of Michigan-Dearborn, IEEE Region 4 Outstanding Engineer Award, and IEEE Southeastern Michigan Section Outstanding Professional Award. He is also the recipient of the National Innovation Award (国家发明奖二等奖) and the Government Special Allowance Award (政府特殊津贴) given by the China Central Government.

Dr. Mi holds a BS and an MS degree from Northwestern Polytechnical University, Xi’an, China, and a Ph.D degree from the University of Toronto, Canada. Dr. Mi worked with General Electric Company from 2000 to 2001. Dr. Mi is the associate editor of Journal of Circuits, Systems, and Computers; the editorial board member of International Journal of Electric and Hybrid Vehicles; guest editor of IEEE Transactions on Vehicular Technology, Special Issue on Vehicle Power and Propulsion; and regional editor of Journal of Small & Special Electrical Machines. Dr. Mi served as the Vice Chair of IEEE Southeastern Michigan Section from 2006 to 2007, and Section Chair for 2008. He is currently the General Chair of the Fifth IEEE International Vehicle Power and Propulsion Conference to be held in Dearborn, Michigan, September 7-11, 2009.