Australian Research for Global Power System Transformation (Stage 3) Topic 1

The Australian National Electricity Market (NEM) is undergoing a significant transition towards inverter-based resources (IBRs) as most synchronous generators (SGs) are being retired and replaced by IBRs such as wind, solar photovoltaic (PV), and battery storage. Currently, the NEM relies heavily on grid-following inverters (GFLIs) that depend on other grid resources to regulate their frequency. However, as IBRs become more prevalent, alternative control methods like grid-forming inverters (GFMIs) will be necessary to maintain a stable IBR-dominated grid. Grid-forming controlled battery energy storage systems (GFM-BESSs) are already being installed in some areas of the NEM, and their usage is expected to increase in the future. To develop effective control strategies for IBR-dominated grids, studies and exploration of different methods are necessary. Due to the unique characteristics of IBRs, such as their fast control schemes, limited overload capabilities, and reduced inertia, their behaviour during and after grid faults is different from that of SGs. Consequently, developing strategies to improve the transient voltage angle behaviour and transient stability (TS) of IBRs would necessitate different approaches than those used for SGs.

This project focuses on the transient stability analysis of power systems, especially those dominated by IBRs, which are prone to instability caused by faults. Building upon the studies completed in Stage 2 CSIRO/GPST, this research project will investigate the transient stability (TS) of multi-generator systems consisting of various power sources, including IBRs, synchronous condensers (SynCons), and dynamic loads. Additionally, the project will develop an analytical tool that can accurately measure the system’s TS margin. Based on the outputs of this analysis, recommendations for maintaining the TS margin at a certain level will be provided. Additionally, the project will investigate potential risks of instability caused by the active power control loop, which is the synchronising loop, and the current limiter of grid-forming inverters (GFMIs). These control blocks play critical roles in stabilising the IBRs during large transients. The findings of this research will be used to develop remedial measures and control schemes to enhance the stability of the synchronising loop and the entire GFMI, while ensuring adequate voltage and frequency support to the grid during large disturbances. Lastly, the project will study the impacts of negative sequence current contributions from IBRs on their TS, particularly for GFMIs. The objective of this task is to recommend reasonable settings for protection systems while maintaining sufficient stability margins for GFMIs.