Three-Stage Load Transfer for Planned Feeder Maintenance via Coordinated Operation of an R-SOP and DG

Planned feeder maintenance in radial distribution networks requires an alternative supply path when no usable mechanical tie line is available or energized AC loop closing is prohibited. This paper proposes a three-stage quasi-steady-state assessment and coordinated dispatch method using a feeder-reconfigurable soft open point (R-SOP) and heterogeneous distributed generation (DG). No active load shedding is scheduled. Stage I uses full-period forecasts to select connection points and assign asymmetrically rated voltage-source converters (VSCs). Stage II progressively transfers the receiving-area demand to the R-SOP while the maintenance branch remains closed. Opening eligibility is assessed from residual branch current, inter-step voltage variation, and power-flow feasibility before and after opening. Stage III assigns the receiving-side VSC the V/f reference role and updates dispatch through rolling optimization and event triggering. In the modified IEEE 33-bus system, the equal-rated fixed SOP has a receiving-side capacity deficit, whereas the 3.0-MVA R-SOP retains a positive continuous margin. In the main case, the maximum steady-state voltage difference across branch opening is below 0.002 p.u., and all monitored operating constraints are satisfied. With DG available, 27 maintenance branches satisfy the complete operating sequence with the R-SOP, compared with 20 with the fixed SOP. These results establish sequential feasibility at the modeled operating points; switching-scale voltage continuity remains to be validated.