Impedance-based stability assessment of parallel VSC HVDC grid connections

The number of converters connected to the system is likely to be increased. These devices may interact with each other through the network. TSOs are concerned about the impact of these interactions and its influence on the stability. This paper presents the stability analysis of a system with two converters. The problem is studied in the frequency domain by using an impedance-based approach. A model for assessing the closed-loop stability of the complete system is developed. This approach shows to have potential for studying the interactions in larger networks. The relative stability under different grid parameters is addressed. Simulation results show that the stability is compromised when a parallel converter is connected.