RoCoF Constrained Regional Inertia Security Region: Formulation and Application

TL;DR

This paper develops a non-linear, non-convex regional inertia security region model for power systems, introducing a linearized calculation method and convexification techniques, with applications demonstrating complex inertia-RoCoF relationships.

Contribution

It formulates the non-linear regional inertia security region and proposes a linearized calculation and convexification approach for practical application.

Findings

Increasing regional inertia may worsen RoCoF in some cases.

The proposed methods effectively handle non-convex security regions.

Application on a 3-region system demonstrates counter-intuitive inertia effects.

Abstract

The regional inertia, which determines the regional rate of change of frequency (RoCoF), should be kept in a secure status in renewable-penetrated power systems. To break away from mapping the regional maximum RoCoF with regional inertia in a linearized form, this paper comprehensively studies the regional inertia security problem from formulation to applications. Firstly, the regional inertia security region (R-ISR) is defined, whose boundary is non-linear and non-convex. Then, a local linearized method is devised to calculate the global maximum of regional RoCoF. The non-convex ISR boundary is expressed by multiple simple boundaries corresponding to each local solution, which can be obtained by a simple search-based method. Finally, the convexified R-ISR constraint is formed by convex decomposition and embedded in an inertia optimal adjustment model. The results on a 3-region system show some counter-intuitive findings, such as increasing the inertia of one region may worsen its RoCoF.