Enhancing Microgrid Resilience and Survivability under Static and Dynamic Islanding Constraints

Microgrids (MGs) are usually characterised by reduced inertia that can lead to large transients after an unintentional islanding event. These transients can result in cascaded device disconnections, triggered by protections, leading to partial of full loss of load in the MG. In this paper, we propose a MG operational planning model for grid-connected operation, enhanced with fault-triggered islanding conditions that ensure the MG survivability (both transient and steady-state) after islanding. We consider the dynamic frequency behaviour after islanding using a non-linear frequency response model and incorporating the associated constraints in the multi-stage, mixed-integer, linear model of the planning problem. Specifically, we include limits on the maximum rate of change of frequency, frequency nadir, and the steady-state frequency deviation. Moreover, to solve this operational planning problem, we propose an iterative solution algorithm that ensures reliable frequency response, selfsufficiency, and optimal operation. Finally, we employ the CIGRE low-voltage distribution network to demonstrate the effectiveness of the proposed method and its suitability in ensuring the reliability, survivability, and resilience of a MG.