Combined Scheme of Lithium-ion Battery Equalization with Energy Support Capabilities for Electric Vehicle Applications

Abstract:
Tauhe problem of Lithium-ion (Li-ion) battery equalization is examined in this paper and a combined scheme of cell equalization and energy support for high demanding applications such as electric vehicles is proposed. The aforementioned combined scheme is realized with cell-to-cell operating mode. The non-dissipative technique is utilized for the Li-ion battery cell equalization and the respective algorithm controls a matrix switch that connects the battery cells with an auxiliary energy storage system (AESS) which can be consisted by either supercapacitors or Li-ion battery cells of lower energy capacity than the main battery pack. Thus, not only cell equalization is attained but also energy support to any weak or problematic cells for both improving the cell equalization process and protecting the cells’ life span of the main battery. Moreover, the AESS can enhance the dynamic performance of the vehicle during fast accelerations and decelerations of the electric vehicle by providing additional energy and absorbing the excess braking energy that cannot be stored in the main battery system so that energy saving is attained. Therefore, a more robust battery storage system is developed that can simultaneously match the requirements of effective non-dissipative cell equalization, cells’ energy support, and improvement of the power dynamic performance of the Li-ion battery pack. The functionality and feasibility of the proposed combined system have been verified with several simulation results that validate the operating improvements and demonstrate the enhanced dynamic performance of the battery system.