Symmetry-Preserving Clustering and Coordinated Control for Voltage Fluctuation Mitigation and Stability Enhancement in Active Distribution Networks with SoC Balancing of Battery Energy Storage

High penetration of distributed renewable generation in active distribution networks frequently leads to severe voltage fluctuations and challenges system voltage stability, as the inherent power-flow symmetry is disrupted by stochastic and bidirectional power injections. To address these issues, this paper proposes a symmetry-preserving coordinated control strategy that integrates topology-constrained clustering with state-of-charge (SoC) balancing of battery energy storage systems to actively mitigate voltage fluctuations and enhance operational stability. First, an agglomerative hierarchical clustering algorithm that explicitly enforces physical line connectivity is employed to partition the distribution network into multiple structurally symmetric autonomous control zones. Within each zone, the SoC of distributed storage units is balanced and aggregated into a virtual battery model, thus maintaining energy-level symmetry and reducing the risk of uneven charging/discharging that would otherwise exacerbate voltage deviations. A model predictive control-based rolling optimization framework is then developed to coordinate photovoltaic inverters and energy storage systems across the zones, explicitly targeting the suppression of voltage fluctuations and the maintenance of short-term voltage stability under varying operating conditions. The proposed method is validated on a modified IEEE 34-bus test feeder with high renewable penetration. Simulation results demonstrate that the strategy effectively limits voltage fluctuation magnitudes, keeps nodal voltages within the required bounds, improves the SoC balance among the storage units, and maintains the nodal voltages within the required bounds across all evaluated coordination strategies.