Abstract
To improve the balancing time of battery energy storage systems with “cells decoupled and converters serial-connected,” a new cell voltage adaptive balancing control method in both charging and discharging modes is proposed in this study. The overall system architecture and basic operating principle of the active balancing system with “cells decoupled and converters serial-connected” are presented first. Then, by dynamically regulating the balancing acceleration coefficient of each cell according to the cell voltage deviation, the adaptive balancing control of cell voltage in charging and discharging modes is analyzed. An experimental prototype consisting of six smart cells is developed, and experiments in charging and discharging modes were carried out. The experiment results demonstrate that compared with the balancing process with a static acceleration coefficient, the proposed adaptive balancing control of cell voltage shows significant improvement in balancing speed and smaller cell voltage discrepancy.
Highlights
In grid-connected energy storage systems and electric vehicles, battery packs are made from long strings of parallel cells in series to achieve higher operating voltages, while each parallel cell consists of several individual cells in parallel to achieve the desired capacity or power levels
Adaptive Balancing Control of Cell Voltage fail before the others
In an unmanaged string of cells in series, the capacities of cells are likely to diverge from one another during a charge/discharge cycle, which can result in degraded battery energy utilization and even damage or explosions (Huang and Qahouq, 2015)
Summary
In grid-connected energy storage systems and electric vehicles, battery packs are made from long strings of parallel cells in series to achieve higher operating voltages, while each parallel cell consists of several individual cells in parallel to achieve the desired capacity or power levels. To validate the effectiveness of the proposed dynamic balancing acceleration coefficient adaptive mechanism in charging and discharging modes, experiments were carried out with an experimental setup consisting of six serially connected smart cells, a DC power supply, a programmable DC electronic load, an oscilloscope, a power meter, a USB-CAN adapter, and a monitoring interface implemented on a computer. 0.25 V for the static acceleration coefficient and 0.5 V for the dynamic acceleration coefficient adaptive mechanism
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