Hierarchical Aggregation and Optimization-Based Coordinated Control for DERs in Active Distribution Systems

High-penetration distributed energy resources (DERs) make active distribution networks increasingly difficult to operate because resource flexibility must be aggregated accurately, coordinated efficiently, and controlled safely under rapid renewable fluctuations. This paper proposes MLHA-CO, a device–microgrid–distribution three-tier coordination framework for DER dispatch in active distribution systems. The framework combines an operational DER accommodation index, a support-function-based aggregation method for nonlinear inverter P - Q capability regions, and a two-stage coordination strategy that links Nesterov-accelerated ADMM with CBF-based real-time safety filtering. Simulations on a modified IEEE 33-bus system show that MLHA-CO achieves a day-ahead operating cost within 1.9% of the centralized SOCP benchmark while reducing the ADMM iteration count by 59%. In real-time voltage control, the proposed method maintains zero voltage violations in the tested 65% DER-penetration scenario with a decision latency of 14.3 ms. The results indicate that the proposed framework can improve DER accommodation and voltage safety while preserving a distributed coordination structure.