Abstract:
Lithium-based batteries are considered as the most advanced batteries technology,
which can be designed for high energy or high power storage systems. However, the battery
cells are never fully identical due to the fabrication process, surrounding environment
factors and differences between the cells tend to grow if no measures are taken. In order to
have a high performance battery system, the battery cells should be continuously balanced
for maintain the variation between the cells as small as possible. Without an appropriate
balancing system, the individual cell voltages will differ over time and battery system
capacity will decrease quickly. These issues will limit the electric range of the electric
vehicle (EV) and some cells will undergo higher stress, whereby the cycle life of these
cells will be shorter. Quite a lot of cell balancing/equalization topologies have been
previously proposed. These balancing topologies can be categorized into passive and
active balancing. Active topologies are categorized according to the active element used
for storing the energy such as capacitor and/or inductive component as well as controlling
switches or converters. This paper proposes an intelligent battery management system (BMS)
including a battery pack charging and discharging control with a battery pack thermal
management system. The BMS user input/output interfacing. The battery balancing system
is based on battery pack modularization architecture. The proposed modularized balancing
system has different equalization systems that operate inside and outside the modules.
Innovative single switched capacitor (SSC) control strategy is proposed to balance between
the battery cells in the module (inside module balancing, IMB). Novel utilization of
isolated bidirectional DC/DC converter (IBC) is proposed to balance between the modules
with the aid of the EV auxiliary battery (AB). Finally an experimental step-up has been
implemented for the validation of the proposed balancing system.
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