Modelling of VSC-HVDC multi-terminal systems for small-signal angle stability analysis

This paper presents a model for small-signal analysis (SSA) of the angle stability of hybrid high-voltage AC (HVAC) systems containing high-voltage DC multi-terminal systems based on Voltage Source Converters (VSC-HVDC). The model developed is highly flexible and makes it possible to seamlessly adapt existing tools for SSA of HVAC systems to be used for hybrid HVAC/VSC-HVDC systems. The proposed small-signal model has been validated and has been used to analyse the impact of an active-power control strategy on power oscillations. The strategy was previously used to improve transient stability in the same type of systems. Results show that the strategy analysed can also help to damp inter-area power oscillations.