Grid-Forming and Grid-Following inverters: a dynamic performance evaluation using RMS, EMT and small-signal analysis

The dynamic performance of inverter-based resources is of increasing importance in power system dynamics. Over the past decade, new types of instabilities driven by inverter controls have emerged, leading to the need for stability studies using the two main types of inverter control: Grid-forming and Grid-following controls. However, there exists a widespread misconception, prevalent across industry, research, and academia, that Grid-following control is inherently "bad" while Grid-forming control is universally "good." This research challenges this misconception by demonstrating the evaluation of inverter controls based on their performance rather than the internal controller architecture. Through comprehensive time-domain RMS, EMT, and small-signal analysis, this study demonstrates that properly tuned Grid-following inverters can exhibit comparable performance to Grid-forming inverters across a wide range of operational conditions. Additionally, the paper addresses the limitations of each technology, particularly in extreme weak grid scenarios.