Parallel Control Strategy for Vanadium Redox Flow Batteries Based on SOC and SOH

Based on the issues of uneven power distribution, deterioration of battery health, and dirert current bus voltage drop in parallel-connected vanadium redox flow battery (VRFB) systems under traditional current-sharing strategies, we proposes an improved current-sharing strategy based on the coordinated control of state of charge (SOC) and state of health (SOH). Built upon the conventional average current-sharing framework, the proposed strategy introduces the SOH weight term and the SOC equalization term into the current-sharing loop in an additive separation form, dynamically adjusting the current reference of each energy storage unit, enabling units with higher SOC and SOH to undertake more power, thereby achieving rational load distribution and SOC equalization. Meanwhile, a secondary voltage compensation link is added to effectively suppress dirert current bus voltage drop and maintain the bus voltage at the desired value. A simulation model of the parallel-connected VRFB system is established using MATLAB/Simulink, and the effectiveness of the proposed strategy is validated under multiple operating conditions, including SOC discrepancy, SOH discrepancy, combined SOC/SOH discrepancy, and load sudden change. Hardware-in-the-loop simulation further verifies its engineering feasibility. The research results provide a theoretical reference for the reliable operation and efficiency improvement of parallel-connected VRFB systems.