VLAN-aware hierarchical multi-agent protection framework for robust fault isolation and coordination in active distribution networks

The increasing penetration of distributed generation (DG) and continuously changing network topologies has fundamentally challenged the reliability and selectivity of conventional protection schemes in modern power distribution systems. These conditions introduce severe coordination difficulties, including miscoordination of relays, loss of selectivity, and delayed fault isolation, particularly under dynamic operating scenarios. To address these challenges, this paper proposes a VLAN-aware hierarchical multi-agent system (MAS) for adaptive protection coordination in DG-rich distribution networks. The proposed architecture introduces a three-layer intelligent protection framework consisting of relay agents (RAs), a coordinator agent (CA), and a supervisory agent (SA). Within this structure, RAs are logically organized into Static VLANs (SVs), Generation VLANs (GVs), and Dynamic VLANs (DVs), representing conventional protection zones, DG-integrated areas, and topology-varying network regions, respectively. The CA enables inter-VLAN coordination, fault localization, and backup protection selection, while the SA ensures system-wide adaptability through topology monitoring and dynamic relay reconfiguration. This hierarchical and VLAN-driven design allows localized decision-making within protection zones while preserving global coordination across the network, ensuring robust and selective fault clearance under bidirectional fault currents and dynamic reconfiguration conditions. A proof-of-concept validation is conducted using an adapted IEEE 39-bus benchmark to evaluate the proposed coordination framework under structurally complex multi-source operating conditions. The results demonstrate the effectiveness of the proposed MAS in improving protection selectivity, coordination reliability, and system resilience within the adopted test platform.