Stability analysis of electrical micro-grids and their control systems. #

Reuben O’Dea, Oliver Smith, Stephen Coombes

11:10 Monday in 4Q07.

Part of the Mathematics of energy session.

Abstract #

The drive towards renewable generation is causing fundamental changes in both the structure and dynamics of power grids. Their topology is becoming increasingly decentralised due to distributed, embedded generation and the emergence of micro-grids. Grid dynamics are being impacted by decreasing inertia, as conventional generators with massive spinning cores are replaced by DC renewable sources. This leads to a risk of destabilisation and places an upper limit on the volume of renewable power sources that can be installed. A wide variety of different control schemes have been proposed to overcome this problem; such schemes fall into two broad categories: so-called grid-following' controllers that seek to match output AC power with grid frequency, and grid-forming’ systems that seek to boost grid stability. The latter frequently work by providing synthetic inertia, enabling DC renewable sources to behave like conventional generators. Here, we employ the master stability function formalism to analyse the stability of micro-grids, providing a framework with which to benchmark the impact of microgrid size and control systems on stability. In addition, we contrast our results with predictions from a widely-used phase oscillator models, finding that such descriptions significantly over-estimate the grid stability properties.