Use of Grid-Forming Inverters to Support Nearby Grid-Following Inverter Stability on the New Zealand Power System

<p dir="ltr">New Zealand is on the brink of a boom in solar generation, wind generation, and battery energy storage system deployment, which connect to the grid via inverter-based power electronic technology rather than traditional synchronous machines. A high penetration of inverter-based resources can present grid stability challenges which require adaptation from the traditional methods of maintaining stability on a synchronous generator dominated network. The particular focus of this research is to determine the applicability of using the emerging grid-forming inverter technology to support grid stability, alongside the more widely used grid-following inverter technology which has known stability limitations in weak grids. The research first assesses the performance of both grid-following and grid-forming inverters in isolated single machine infinite bus networks of varying short circuit ratio scenarios, the grid-forming inverter is shown to be more stable than the grid-following inverter. The single machine infinite bus case is then extended to include both the grid-forming inverter and the grid-following inverter, showing that a nearby grid-forming-inverter can improve the stability of a system with a grid-following inverter connected. The study is then extended to demonstrate the same finding on the New Zealand power system, connecting to low strength buses in the Bay of Plenty region. The results show the grid-forming inverters installed close to grid-following inverters can improve the stability of an existing grid-following inverter connection.</p>