Evaluating Grid-Following and Grid-Forming MMC Impact on AC Fault Current Injection and Distance Protection

This paper investigates the AC fault behaviour of MMC-based systems and its impact on voltage support and distance protection. Although modern grid codes impose similar fault ridethrough and voltage support requirements on grid-following (GFL) and grid-forming (GFM) converters, their fault responses differ fundamentally due to their current-source and voltagesource characteristics. Using identical direct current limitation strategies, the paper compares