A Monovoltage Equivalent Model of Bi-Voltage Autotransformer-Based Electrical Systems in Railways

Abstract

This paper presents an equivalent model that allows representing bi-voltage autotransformer-based systems (such as 2 25 kV ac, 2 15 kV ac) as if they were monovoltage systems. This model can be used for symmetrical (such as 2 25-kV 50-Hz systems) and unsymmetrical (such as 12/24-kV 25-Hz systems) configurations. It is based on two simplifying hypotheses that establish relationships between currents and voltages in the positive and negative phases. These hypotheses are discussed and the accuracy of the model is evaluated by comparing the results with a detailed conventional model of power-supply systems.

Study of Resonances in 1 <formula formulatype="inline"> <tex Notation="TeX">$\times$</tex> </formula> 25 kV AC Traction Systems With External Balancing Equipment

“…The same example was analyzed with d = 15 km and the result of k p, 4 apx1 allowed the 5 th and 6 th resonance frequencies (i.e., k p, 5 and k p, 6 ) to be obtained. The study verifies that a larger number of trains (that is, higher traction system power consumption) leads to smaller external balancing equipment reactances (2), and therefore to lower first resonance frequencies (see Fig. 4).…”

“…2), which is formed by, -The power system: It is characterized from its open-circuit voltage U O and short-circuit power S S at the point of coupling. Since this short-circuit power is usually high, the short-circuit impedance is nearly zero, and so it could be neglected [2]. -The railroad substation U N1 /U N2 transformer: It is modeled from its rated power S N and per-unit short-circuit impedance ε cc .…”

“…Based on the slight dependence of the second resonance on the power system, external balancing equipment and train position d [2], [5], [10] (Fig. 4), its frequency can be roughly determined by neglecting the power supply and external balancing equipment reactances and placing the train at the beginning of the contact feeder section (i.e., d = 0 km) in the circuit of Fig.…”

“…Although there is no information on the short-circuit power of the supply networks, a 700 MVA value is assumed. It is also assumed that external balancing equipment is connected to the power system and designed according to (2) to balance the power consumption of 2 or 5 trains. Considering these data, Fig.…”

Optimal deployment of energy storage systems in a DC-electrified railway system

“…In the optimization field, [5] has analysed the optimum features of a ESS in the planning stage [6] has developed a simplified model of 2x25 kV high speed railway supply systems which makes it possible to find optimal places for connections to the utility network.…”