On Dynamic Reconfiguration of a Large-Scale Battery System

Abstract

Abstract-Electric vehicles powered with large-scale battery packs are gaining popularity as gasoline price soars. Large-scale battery packs usually consist of an estimated 12,000 battery cells connected in series and parallel, which are susceptible to batterycell failures. Unfortunately, current battery-management systems are unable to handle the inevitable battery-cell failures very well. To address this problem, we propose a dynamic reconfiguration framework that monitors, reconfigures, and controls large-scale battery packs online. The framework is built upon a syntactic bypassing mechanism that provides a set of rules for changing the battery-pack configuration, and a semantic bypassing mechanism by which the battery-cell connectivity is reconfigured to recover from a battery-cell failure. In particular, the semantic bypassing mechanism is dictated by constant-voltage-keeping and dynamicvoltage-allowing policies. The former policy is effective in preventing unavoidable voltage drops during the battery discharge, while the latter policy is effective in supplying different amounts of power to meet a wide-range of application requirements. Our experimental evaluation has shown the proposed framework to enable the battery packs to be 9 times as fault-tolerant as a legacy scheme.

Pack Sizing and Reconfiguration for Management of Large-Scale Batteries

“…The battery system under consideration is based on the reconfigurable battery system proposed in [10]. Each battery pack consists of a group of control units under a local controller and an array of battery cells.…”

“…With the switches in packs, we can organize cells in series, parallel or many parallel branches of series. The design details of switches, controllers and sensors of SoC can be found in [10], [11]. We can treat a battery pack as a module, just like a single cell, and to use switches around packs to reconfigure them.…”

“…Complex scheduling of switch (on/off) operations can be done but is left as our future. Existing reconfiguration schemes (e.g., [10]) cannot fully utilize available healthy cells a faulty cell. In the existing schemes, all packs are required to use the same number of cells and bypass the rest.…”

“…To achieve fault-tolerance and deliver dynamic power, Kim and Shin [10] proposed a framework to reconfigure and control a large number of battery packs, achieving resilience to cell failures and outputting diverse levels of power. By placing programmable switches around each cell, this reconfigurable framework can bypass faulty cells.…”

“…1) Inflexible connectivity under-utilizes battery cells. Existing reconfiguration frameworks, including the one in [10], restrict the way in which battery cells and packs are connected via programmable switches. For example, they require homogeneous configuration of cells and packs.…”