Reliability Assessment for Flexible Interconnected Distribution Network Considering MMC Faults and Coordinated Multi-Device Restoration

This paper proposes a comprehensive reliability assessment method for flexible interconnected distribution networks (FIDNs) with soft open point (SOP) incorporation and coordinated multi-device load restoration. The following research work is conducted: first, a reliability function for hybrid modular multi-level converters (MMCs) is developed based on actual topological structures, with sub-module (SM) correlation and redundancy configurations comprehensively considered. Moreover, various SOP ports fault scenarios and their corresponding control strategies for distribution network faults are analysed, and an improved virtual flow method is proposed to satisfy network radiality and connectivity constraints during load restoration. On this basis, a mixed-integer second-order cone programming (MISOCP) model for FIDN load restoration is formulated, aiming to maximise load restoration through multi-device coordinated output. Furthermore, load nodes are classified based on their restorability post-fault, and optimal load restoration is performed under fault scenarios generated by Monte Carlo sampling, with system reliability indices further calculated. Finally, the effectiveness of the proposed method is validated on a modified 37-node system and the modified IEEE 123-node test system.