Improved monitoring and battery equalizer control scheme for electric vehicle applications

Abstract

This paper proposes an improved battery management system (BMS) that provides supervisory monitoring and active cell-to-cell equalization in order to protect the battery lifespan in an electric vehicle (EV). This can be accomplished through a Supercapacitor (SC) bank that can store and then recover electric energy to any weak cell of the EV battery bank. Specifically, the proposed control scheme online detects any problematic battery cell through a supervisory monitoring scheme that oversees the main monitoring system of battery pack. Then, a matrix power switches system connects the SC-bank in parallel with the problematic cell, in order to attain voltage equalization with the other battery cells. Moreover, urgent energy assistance is provided to any weak cells in case of high dynamic conditions, by aiming to keep their voltage as close as possible to the voltage of the other series connected cell unites. The SC-bank is connected to a problematic battery cell through a bidirectional non-isolated dc-dc converter. The functionality and the effectiveness of the proposed supervisory monitoring and battery equalizer system in an EV have been verified by simulations with Matlab/Simulink. Thus, selective simulation results are presented in order to validate the operational improvements obtained by the suggested control scheme.