Voltage Stability Analysis of Grid-Forming Converters with Current Limitation

In this paper, a systematic short- and long-term voltage stability analysis of grid-forming converters with current limitations is conducted. For this, sampling studies are performed in an aggregated version of the Nordic test system. Here, the grid-forming control approach, the simulation type (EMT/phasor), current prioritisation and load composition are varied. Also, a stability-enhancing control method is developed to stabilise the converter during current limitation. The proposed method does not require any parameter tuning and can be applied to almost all grid-forming approaches. Its performance is demonstrated by comparing it to similar methods. The results show that the proposed method can greatly improve short- and long-term voltage stability for all investigated grid-forming approaches. In addition, accurate load models are crucial, as small modelling differences can have a greater impact on stability than the choice of simulation type. Here, both simulation types show the same voltage dynamics but have small differences in the stability limits.