Application of linear analysis in traction power system stability studies

Dynamical phenomena such as oscillations and instability in railway power systems have caused concern in the experts' community the recent years. On several occasions, modem advanced electrical rail vehicles have been the source of low frequency power oscillations leading to an unstable power system due to lack of damping, and as a consequence operational problems. A method to study these phenomena is needed. Well known linear techniques based on small-signal analysis provide valuable information about the inherent characteristics of even non-linear single-phase power systems. This paper describes how a traction power system and its dynamical railway-related components are modelled in a commercially available power system analysis software and studied by linear analysis such as eigenvalues, participation factors and parameter sensitivities. This is used to gain knowledge about the interaction between the rail vehicles and the electrical infrastructure. Linear analysis is found to be a powerful tool in this respect provided that adequate models of the relevant components can be established in RMS mode. The results clearly indicate poor interaction.