State of charge estimation for battery packs using H-infinity observer in underground mine electric vehicles

An H-infinity observer (HIO) for state of charge (SOC) estimation is proposed for a series-connected battery pack in underground mine electric vehicles (UMEVs). In the proposed method, an average virtual cell (AVC) model is defined and the SOC of the AVC model is estimated to represent the pack SOC when all terminal voltage differences (TVDs) between each individual cell in the pack and the AVC are within a pre-set voltage threshold. To make sure all the TVDs are within the threshold, lithium iron phosphate cells are clustered into the group with similar characteristics and the cells in the same group are used to build the sorted battery pack. The experiments of pulse current and current profiles based on both urban dynamometer driving schedule and underground mine driving cycle are conducted on the sorted battery pack to verify the effectiveness of the proposed HIO for the pack SOC estimation under UMEVs.