Service Restoration through Coordinated Operation of Soft Open Points and Distributed Generation Units in Distribution Networks

Abstract

The Soft Open Point (SOP) is an emerging power electronics device in distribution networks to replace normally open points (NOPs). During faulty conditions, service restoration can be effectively conducted by coordinating SOPs and distributed generation (DG) units. In this paper, a novel two-stage service restoration method is proposed for a distribution network by coordinating multiple SOPs and DGs. In Stage 1, a dynamic load-shedding scheme is applied during a fault at the upstream grid or distribution substation of a distribution network, and power supply to priority loads is kept uninterrupted as much as possible with DGs. Considering the ramp rate constraints of controllable/dispatchable DGs (CDGs) in Stage 1, their active power generation is kept at the same set points as they were before the fault. In Stage 2, CDGs are dispatched to maximize restoration in the outage area. In both stages, active and reactive power of SOPs are regulated to maximize restoration. A mixedinteger nonlinear programming (MINLP) model is developed using AC power flow to formulate the proposed restoration method. The centralized (coordinated) and decentralized (uncoordinated) optimization of SOPs and DGs are conducted and compared to validate the proposed restoration method using the modified IEEE 33-node test system.