Summary
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
Read more Read lessGFL and GFM converters under AC faults, evaluating fault current injection, voltage support, and apparent impedance trajectories observed by distance relays. The influence of key control elements, including phase-locked loop and virtual synchronous machine dynamics, fault current injection, and virtual impedance, is analysed through EMT simulations. The results show that fault behaviour is dominated by the current limitation strategy for both control modes.
However, GFM converters provide better voltage support and produce more stable impedance trajectories, leading to less sensitivity of distance protection to fault resistance and fault location. In contrast, distance protection under GFL operation is more prone to underreach.
These findings highlight the advantages of GFM control with appropriate current limitations for reliable protection in converter-dominated power systems.
Additional informations
| Publication type | Session Materials |
|---|---|
| Reference | B5_10126_2026 |
| Publication year | |
| Publisher | CIGRE |
| Country | Belgium |
| Study committees | |
| File size | 2 MB |
| Price for non member | 30 € |
| Price for member | 30 € |
Authors
LIU Xiaoxiao - KU Leuven, Belgium; CHAFFEY Geraint - KU Leuven, Belgium; JUDGE Paul - University of Edinburgh, United Kingdom; VAN HERTEM Dirk - KU Leuven, Belgium
