Evaluating the Potential for Cell Balancing Using a Cascaded Multi-Level Converter Using Convex Optimization

Abstract

The modeling and design of an active battery cell balancing system using Multi-Level Converter (MLC) for EV/HEV/PHEV is studied. The MLC allows to independently switch ON/OFF each battery cell in a battery pack. This extra degree-of-freedom (DoF) can be exploited to optimally use each cell in order to balance among them the temperature and state-of-charge (SoC). This study has shown that the constrained convex optimization based control policy, exploiting the extra DoF of MLC, gives significant benefit in terms of reduction in temperature and SoC deviations, especially under parameter variations, compared to uniformly using all the cells. Thus, the MLC has promising potential to offer extra benefit of achieving cell balancing while being simultaneously used as a motor driver.