An Adaptive Reclosing Scheme for Preserving Dynamic Security in Low-Inertia Microgrids

Conventional reclosing schemes with fixed dead times can threaten the dynamic security of low-inertia microgrids (mu Gs) in case of permanent faults. This paper proposes an adaptive reclosing approach for restoring the interrupted feeder operation and maintaining the dynamic security within the shortest time. The proposed approach is outlined in three stages: First, a secure zone based on mu G operation conditions is determined at the pre-fault stage for reclosing under permanent faults. The mu G dynamic security can be retrieved if the fault is cleared in secure zone. Second, mu G state variables are monitored at the during-fault stage to obtain associated temporal characteristics. At the third stage, post-fault samples are examined as appropriate candidates to reclose faulty feeders. Here, samples are forecasted considering a sufficient readiness lead time. For forecasted samples, the locus of state variables for reclosing under permanent fault is predicted using the characteristics attained at the second stage. Here, reclosing decisions are made by comparing the locus of state variables with secure zone boundaries. Comprehensive simulations presented in this paper confirm effectiveness of the proposed adaptive reclosing method.