An Enhanced Sizing Approach of Auxiliary Energy Storage on Improving Li-Ion Battery Equalization Performance for Motor Drive Applications

This paper introduces a novel sizing algorithm for an Auxiliary Energy Storage System (AESS) that operates within non-dissipative equalization topologies utilizing bidirectional DC/DC converters, developed for battery powered motor drive applications. The sizing algorithm integrates both equalization and dynamic energy support functions to determine the optimal AESS energy capacity and power specifications. The key objectives of the proposed sizing methodology are to fulfil the desired equalization and dynamic support of the main battery with the minimum cost, mass, and volume by also considering the ageing process of both the main battery and the AESS. This can be accomplished by considering the specific energy and operating demands of the application, the characteristics of the candidate storage technologies that may be used for AESS (such as Li-ion batteries or supercapacitors), and the system longevity. Thus, aging models are integrated to consider AESS degradation for ensuring its viability for second-life use and thus, maximizing asset value. A significant advantage of the proposed AESS sizing methodology is its broad applicability, as it is both model- and hardware-agnostic. The algorithm's effectiveness is validated through both simulation and experimental results on a cell-to-cell equalization topology, and several results are presented to demonstrate the operating improvements.