Discharge scheduling for voltage balancing in reconfigurable battery systems

Abstract

To manage thousands of battery cells effectively, a reconfigurable battery system has emerged where each battery cell is equipped with a set of switches for controlling connectivity (i.e. series, parallel, bypass or combinations thereof). While most studies have focused on maximising operation-time or lifetime of a reconfigurable battery system, few studies have addressed how to quickly balance voltage of cells, which affects both efficiency and safety of a battery system. A new discharge scheduling policy for battery cell voltage balancing for a reconfigurable battery system is proposed. Based on the analysis why existing naive approaches are not effective for voltage balancing, a new approach consisting of three steps is designed: determination of a set of battery cells to be discharged, calculation of a target voltage, and distribution of the system load to each battery. The present simulation results show that the proposed approach outperforms three alternative ones up to 45.6% in terms of voltage balancing.

An Enhanced Active Balancing Circuit with Reconfigurable Battery for Electric Vehicles

“…The battery pack controller identifies the sub packs which have to be balanced and provides appropriate switching signals to the switches D 1 , D 2 , D 3 , B 1 , B 2 , B 3 , Q 1 and Q 2 by the reconfiguration algorithm like [22], [23]. The switches B 1 , B 2 and B 3 decide which sub packs have to be balanced while the switches D 1 , D 2 and D 3 decide the sub pack which has to deliver the load and the switches Q 1 and Q 2 are used to transfer the charge through the coupled inductor.…”