Battery Cluster Grid-Connected Balancing Control Strategy Based on Series Power Converter

A study on the grid-connected lithium-ion battery cluster found that in the charging mode, if the module controller controls the current independently, it will lead to unstable current and voltage divergence. To solve this problem, series I-P droop control based on the parallel droop control was used to achieve stable power distribution. To achieve state of charge (SOC) balancing, the SOC was introduced into the series droop control. To improve the speed, an improved strategy was proposed to dynamically adjust the balancing factor according to the SOC range. Simulation results are presented on a cascaded modular grid-connected system containing six battery modules. The results show that the proposed balancing control strategy can achieve bus side voltage, power and SOC balancing; under the same balancing index, the improved strategy requires shorter time, the effect is more significant when the SOC range is small.