Improving grid strength in a wide‐area transmission system with grid forming inverters

Abstract

This paper summarizes Electromagnetic Transient (EMT) simulation studies using PSCAD/EMTDC undertaken to evaluate the capability and suitability of commercially available large scale Grid Forming Inverters (GFMI) to dampen oscillations in a real bulk power transmission network. Faults and a range of grid voltage oscillation frequencies are tested on GFMI and synchronous condenser (SC) models using single source equivalent network model and comparisons of transient, post fault and oscillatory rejection tests are presented. A critical credible fault in the West Murray Zone (WMZ) was simulated on a wide‐area EMT model of the Australian National Electricity Market (NEM) to show the effectiveness of GFMI in providing system strength services and improving damping of network sub‐synchronous control interactions (SSCI). Two scenarios were examined: Direct replacement of existing centralized synchronous condensers in the WMZ of the NEM, and a decentralized distribution of GFMI in the transmission network (treated as expansion or repowering solution for existing grid following inverter equipped solar farms). Simulation results show that commercially available GFMI are a viable option for improving system strength in a practical transmission system with a high proportion of Inverter Based Resources (IBR).

On the Stabilizing Contribution of Different Grid-Forming Controls to Power Systems

“…Finally, even in studies directly targeting the improvement brought by GFM controls, little attention is paid to their specific type. In fact, it is often assumed that all GFM controls yield similar stability improvements, provided they are properly tuned and fulfill the primary functions of synthetic inertia and/or frequency droop 19 .…”

On the Respective Contributions of Different Grid-Forming Controls to Small-Signal Stability

“…Finally, even when a study is directly targeted towards the study of the improvement brought by GFM controls, little attention is paid to the type of GFM controls. In fact, it is assumed all GFM controls lead approximately to the same stability improvement, provided they are properly tuned and fulfill the main functions of synthetic inertia and/or frequency droop [13].…”