This paper proposes a novel reliability assessment method for flexible interconnected distribution network (FIDN) based on soft open point (SOP) considering post-fault multi-stage recovery

which is characterized by explicitly expressing the SOP-based FIDN topology state through the decision variables of the optimization process

so as to establish a mixed-integer linear programming (MILP) model for FIDN reliability assessment. Firstly

the multi-stage recovery process of FIDN is analyzed

and a FIDN reliability assessment framework with decoupled computation of multi-stage recovery process is proposed. Then

a reliability assessment-oriented SOP equivalent model is established based on the external characteristics of SOP under normal operation and different faults

and a FIDN node-branch state correlation model is established to achieve network topology state explicitness. After that

the SOP fast transfer model under different strategies is established by considering the SOP capacity constraint and short-time overload capability. On this basis

a MILP model for FIDN reliability assessment is established by considering the multi-stage recovery process of SOP fast transfer

fault point upstream recovery

tie switch switching transfer

and island operation. Finally

the effectiveness of the proposed method is verified on a modified 37-node system.