Lars Abrahamsson

Railway Power Supply Investment Decisions Considering the Voltage Drops - Assuming the Future Traffic to Be Known

Transports on rail are increasing and major railway infrastructure investments are expected. An important part of this infrastructure is the railway power supply system. The future railway power de ...

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

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.

Basic Modeling for Electric Traction Systems Under Uncertainty

The objective of this paper is initially to present a basic modeling of the railway traction system. This model includes the basic technologies used today. The voltage dependencies of the maximal possible power consumption as well as the maximal velocity of the common Rc-locomotives are included. The latter is very crucial for the studies of time table sensitivity, which is of our immediate interest. Moreover, a method is presented, that estimates the expected train delay time for a given feeding technology. The reference timetable assumes the same train and surrounding conditions, but no voltage drops. In the numerical example where the developed model is applied to a realistic test system, a set of possible amounts of railway traffic are treated as uncertainties. Mainly, the contributions of this paper are three: compiling and connecting already accepted models, the development of a method for numerical calculations using this model compilation, and an example to apply this model on

HVDC feeding with OPF and unit commitment for electric railways

In this paper a railway power system design based on an HVDC feeder is suggested. The converter stations between the public grid and the HVDC feeder can be sparsely distributed, in the range of 100 km or more, whereas the converters connecting the HVDC feeder to the catenary are distributed with a much closer spacing. The ratings of the catenary-connected ones can be lower than substation transformers or rotary converters, since the power conversion can be fully controlled. Simulations of the proposed solution show clear advantages regarding transmission losses and voltages compared to conventional systems, especially for cases with long catenary sections, and when there are substantial shares of regeneration from the trains.

Fast estimation of the relation between aggregated train power system information and the power and energy converted

Transports on rail are increasing and major investments in the railway infrastructure, including the Railway Power Supply System (RPSS), are expected. The future railway power demands are naturally not known for certain. The more remote the uncertain future, the greater the number of scenarios that have to be considered. Large numbers of scenarios make time demanding simulations unattractive. The aim of this paper is to present a fast approximator that uses aggregated RPSS information. Since the electrical and mechanical relations governing an RPSS are quite intricate, an approximator based on neural networks (NN), is applied. This paper presents a design suggestion for an NN estimating the power and energy flows through each converter station, given RPSS data and levels of train traffic. Even if the future usage of the NN is investment planning, the modeling of such an approximator has a value in itself concerning the understanding of the relations between RPSS and train traffic.

An SOS2-based Moving Trains, Fixed Nodes, Railway Power System Simulator

This paper presents and proposes an optimization model for railway power supply system simulations. It includes detailed power systems modeling, train movements in discretized time considering running resistance and other mechanical constraints, and the voltage-drop-induced reduction of possible train tractive forces. The model has a fixed number of stationary power system nodes. The proposed model uses SOS2 (special ordered sets of type 2) variables to distribute the train loads to the two most adjacent power system nodes available. The impact of the number of power system nodes along the contact line and the discretized time step length impacts on model accuracy and computation times are investigated. The program is implemented in GAMS (General Algebraic Modeling System). Experiences from various solver choices are also presented. The train traveling times are minimized in the example. Other studies could, e.g. consider energy consumption minimization. The numerical example is representative for a Swedish non-centralized, rotary-converter fed railway power supply system. The proposed concept is however generalizable and could be applied for all kinds of moving load power system studies.

A variable no-load voltage scheme for improving energy efficiency in DC-electrified mass transit systems

Railway mass transit systems like subways play a fundamental role in the concept of sustainable cities. In these systems, the amount of passengers strongly fluctuates along the day. Hence, in order ...

Fast Estimation of Aggregated Results of Many Load Flow Solutions in Electric Traction Systems

Transports on rail are increasing and major railway infrastructure investments are expected. An important part of this infrastructure is the railway power supply system. The future railway power de ...

Optimizing the Power Flows in a Railway Power Supply System Fed by Rotary Converters

This study focuses on optimizing the operation of rotary railway-feeding converters. Since a large share of rotary converters can be expected to be in operation for decades to come in the railway p ...

Identifying electrically infeasible traffic scenarios on the iron ore line : Applied on the present-day system, converter station outages, and optimal locomotive reactive power strategies

This paper presents the main findings of a Masters Thesis project carried out in cooperation between Transrail and Royal Institute of Technology (KTH). The main objective was to create a plugin fo ...