TITLE:
A Multi-Stage Control Strategy for Transient Mitigation in Islanded Rural Mini-Grids via CCS-CNT Integration
AUTHORS:
Sinqobile Wiseman Nene
KEYWORDS:
Minigrid, Capacitor Coupled Substation, Controllable Network Transformer, Power Flow Control, Rural Electrification, System Modelling
JOURNAL NAME:
Open Access Library Journal,
Vol.13 No.5,
May
28,
2026
ABSTRACT: Access to electricity remains limited in many rural communities in South Africa and other regions where grid extension is technically difficult and economically unattractive. In such settings, islandable minigrids offer a practical pathway for delivering reliable and sustainable electricity. This paper presents a novel staged islanding and reconnection control strategy for rural minigrids based on the coordinated operation of a Capacitor Coupled Substation (CCS) and a Controllable Network Transformer (CNT). The main contribution of the study is the integration of grid-status logic, a staged circuit-breaker switching sequence, and coordinated CCS-CNT control to reduce switching transients while maintaining voltage stability during the transition between grid-connected and islanded operation. The proposed method is evaluated on an 11 kV minigrid comprising a 1 MW solar photovoltaic source supplying a 500 kVA downstream load. A mathematical model and coordinated switching algorithm are developed and implemented in MATLAB/Simulink to represent the multi-stage breaker actions and the dynamic response of the CCS-CNT interface during islanding. In contrast to direct islanding, the proposed staged sequence is designed to mitigate inrush and synchronization transients, improve active and reactive power coordination, and keep voltage variations within acceptable utility limits. Simulation results show that the CCS-CNT-based staged control strategy improves voltage regulation and reduces transient disturbance during islanding events. These findings indicate that the proposed approach provides a robust and cost-effective solution for improving the resilience of rural minigrid power systems.Subject AreasDynamical System