Active Balancing System for Electric Vehicles with Incorporated Low Voltage Bus

TitleActive Balancing System for Electric Vehicles with Incorporated Low Voltage Bus
Publication TypeJournal Article
Year of Publication2016
AuthorsEvzelman, M., M. Muneeb Ur Rehman, K. Hathaway, R. Zane, D.. Costinett, and D.. Maksimovic
JournalPower Electronics, IEEE Transactions on
KeywordsBatteries, battery balancing, Computer architecture, DC-DC power converters, dual active bridge, electric vehicle, load sharing, Low voltage, low voltage bus, Microprocessors, power converters, Vehicles, voltage control

Electric-drive vehicles, including hybrid (HEV), plug-in hybrid (PHEV) and electric vehicles (EV), require a high-voltage (HV) battery pack for propulsion, and a low voltage (LV) dc bus for auxiliary loads. This paper presents an architecture that uses modular dc-dc bypass converters to perform active battery cell balancing and to supply current to auxiliary loads, eliminating the need for a separate HV-to-LV, high step-down dc-dc converter. The modular architecture, which achieves continuous balancing of all cells, can be used with an arbitrary number of cells in series, requires no control communication between converters, and naturally shares the auxiliary load current according to the relative state-of-charge (SOC) and capacities of the battery cells. Design and control details are provided for low-voltage, low-power dual active bridge (DAB) power converters serving as bypass converter modules. Furthermore, current sharing is examined and worst case SOC and current deviations are derived for mismatches in cell capacities, SOCs and parasitic resistances. Experimental results are presented for a system consisting of twenty one series 25 Ah Panasonic Lithium-Ion NMC battery cells and twenty one DAB bypass converters, with combined outputs rated to supply a 650 W auxiliary load.