380 EngineeringRail Power Supply 118 (2020) Heft 10 New method for determining the lowfrequency stability limit of a 50 Hz electric traction power system Yosr Hachicha, David Cypers, Maxime Meli, Séméac (FR); Philippe Ladoux, Nicolas Roux, Toulouse (FR) Low frequency voltage instabilities in AC railway traction power supply networks are due to the interactions between modern traction vehicles and infrastructure. To calculate the correlations a straightforward method to determine the stability limit of the traction system has been developed. The method is based on the plot in the complex impedance plane (R, X) of the stability limit curve of a traction chain. The validation of this method is performed through the use of a PC simulation. Neue Methode zur Bestimmung der Niederfrequenzstabilitätsgrenze eines 50-Hz-Bahnenergieversorgungssystems Niederfrequenzspannungsinstabilitäten in Bahnenergieversorgungsanlagen von Wechselstrombahnen sind auf die Wechselwirkungen zwischen modernen Triebfahrzeugen und der Infrastruktur zurückzuführen. Zur Berechnung der Zusammenhänge wurde eine vereinfachte Methode zur Bestimmung der Stabilitätsgrenze des Bahnenergieversorgungssystems entwickelt. Die Methode basiert auf dem Diagramm in der komplexen Impedanzebene (R, X) der Stabilitätsgrenzkurve einer Traktionskette. Die Validierung dieser Methode erfolgt mittels einer PC-Simulation. Détermination de la limite de stabilité basse fréquence du système d’alimentation de traction ferroviaire à 50 Hz Les instabilités de tension basse fréquence des réseaux ferroviaires électrifiés en courant alternatif sont dues aux interactions entre les véhicules de traction modernes et les infrastructures. Le développement de cette méthode simple pour déterminer la limite de stabilité d’un système de puissance ferroviaire est présenté dans cet article. La méthode est basée sur le tracé dans le plan d’impédance complexe (R, X) de la courbe de limite de stabilité d’une chaîne de traction. La validation de cette méthode est réalisée grâce à l’utilisation d’une simulation PC. 1 Introduction In the early 2000s, many cases of voltage instability were observed in AC rail networks as a result of the massive introduction of traction vehicles equipped with four-quadrant rectifiers (4-Q). The phenomena occurred on both the electrified railway lines in AC15 kV 16,7Hz and AC25 kV 50Hz. In order to determine the origins of the phenomenon, several theoretical studies were carried out [1; 2; 3]. Low frequency instability appears as an amplitude modulation of the contact line voltage and current at very low frequency (a few Hertz). Figure 1 shows the waveforms of the first case of low frequency instability that appeared in northeastern France near the city of Thionville in 2008 [4]. In practice, these low-frequency oscillations can lead to train traction power supply shut down when current or voltage ripple reaches detection threshold. The electric traction power system (composed of the traction power supply network and the traction -900 -600 -300 0 300 600 900 -40 -20 0 20 40 0,00 0,25 0,50 0,75 s 1,00 t UCL ICL a b Figure 1: AC 25 kV 50 Hz electic power supply – Modulation of contact line voltage (a) and current (b) measured at the substation in Thionville – France (source: Didier Frugier/SNCF, modified: eb)].
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