A Novel Comprehensive SOC-Voltage Control Scheme for Lithium-ion Battery Equalization

This paper proposes a novel comprehensive state of charge (SOC) and voltage control scheme for battery equalization. For the circuit topology, the equalizers contain balancing circuits based on buck-boost converter topology, which can guarantee bi-directional power flow between battery cells, and each cell is corresponding to one balancing circuit. For the control scheme, real time SOC of each cell is measured to determine the switching state of each balancing circuit so that equalization path can be changed accordingly. Real time voltage is also measured to minimize the load voltage ripple. PI controller is then applied to regulate both SOCs and voltages across the battery cells through the adjustment of the switching duty ratios, thus making a trade-off between equalization speed and battery voltage fluctuations. The circuit topology is constructed in SIMULINK while the control algorithm is implemented in MATLAB. Simulation results of SOC, voltage and current are obtained to validate the control design.