Damping of electromagnetic transients in a superconducting VSC transmission system

Applications of superconductivity in power systems, especially in transmission systems, is a subject of study since 1970s. Superconductors´ advantage of providing an almost lossless transmission system, due to the non-existence of joule losses, has been highlighted during the last decades. However, the absence of resistance and its ability to damp oscillatory phenomena, which in case of a superconducting transmission system can be long-lasting, can result in a system prone to instability. Therefore, persisting oscillations that can be attributable to a variety of reasons (ac or dc faults, voltage sags, rapid load changes, switching actions etc.) need to be damped by applying other methods. This paper introduces a method to provide damping in a superconducting two-terminal voltage-source converter (VSC) transmission system by incorporating suitably-dimensioned snubber circuits. The method is generally used in other types of application but, in this paper, its suitability is tested on a specific case reference model built in MATLAB/Simulink®, as well as under different oscillation causes, i.e. dc and ac faults.