Model based evaluation of lithium ion capacitors use and management for plug-in hybrid vehicles

This paper deals with on-board integration of lithium-ion capacitors into plug-in hybrid electric vehicle applications. Power exchanges with the vehicle battery pack are controlled through a DC/DC bidirectional power converter, which is interposed between the DC-Link and a 125 V 73 F lithium-ion capacitor module. Specific energy management strategies have been evaluated and compared in this work with the aim of optimizing battery cycling life on different operative conditions (driving cycles and real driving mission profiles). Those evaluations are carried out in simulation environment, based on the use of detailed simulation models of a C-segment plug-in hybrid vehicle and lithium-ion capacitors. Models have been preliminary parametrized and validated by means of laboratory experimental activities. The obtained results highlighted the benefits of using hybrid energy storage systems, based on lithium-ion capacitors, in reducing power peaks for the battery pack and related impact on battery cycling life.