DC-electrified Railway Systems Research Articles

Design of Light-Load Regenerative Brake Control System with Load Power Estimation for DC Electrified Railways

In DC-electrified railway systems, light-load regenerative brake control prevents the occurrence of overvoltage at the filter capacitor (FC) of the traction inverter of the regenerative vehicle. However, such control can restrict regenerative power more than necessary when the distance between the powering train and regenerative train is increased, although a sufficient load exists in the electric traction system. This study clarifies the principle of the method to restrict torque current of the regenerative train based on the load power. Subsequently, a method is proposed to design the load power estimation controller.

Evaluation of the Effect of Stray Current Collection System in DC-Electrified Railway System

Stray current corrosion damage is significant in DC traction power supply system (DTS). Stray current collection system including stray current collection network (SCCN) and stray current drainage device (SCDD) is designed to control the stray current. A comprehensive system integrated calculation model is established to evaluate the stray current. And the iterative power flow algorithm with simplification of DTS is proposed. The stray current distribution is calculated by multi sections rail reflux system model. The model is verified with CDEGS simulation. The influence of stray current collection system on stray current is evaluated. The result shows that the primary stray current is mainly affected by rail to SCCN resistance and the length of the line. The efficiency of collecting stray current of SCCN is mainly affected by the resistance of SCCN and the SCCN to earth resistance. While the use of SCDD deteriorates the efficiency of collecting stray current of SCCN. A site test was carried out in Chengdu Metro Line 1 to evaluate the effect of stray current collection system.

Determining the optimum installation of energy storage systems in railway electrical infrastructures by means of swarm and evolutionary optimization algorithms

The installation of wayside Energy Storage Systems (ESSs) in DC-electrified railway systems is one of the main measures to improve their energy efficiency. They store the excess of regenerated energy produced by the trains during the braking phases and give it back to the system when necessary. Nevertheless, the big cost of the associated installation can make railway operators hesitate about the convenience of the investment. Additionally, the decisions about the configuration of the installation (locations and sizes for the ESSs) are usually based on the previous experience of the railway operators or, at best, in assessments made with simulation tools with low accuracy.This paper proposes a model to optimize the profitability of the investment. Nature-inspired optimization algorithms are applied in combination with a very realistic railway simulator. The flexibility of the nature-inspired optimization algorithms, together with their ability to successfully deal with the computationally-intensive and highly non-linear and non-convex problem posed by the realistic railway simulator, makes them the perfect choice.Three different nature-inspired optimization algorithms have been selected and compared: the Genetic Algorithm (GA) as the main exponent of the evolutionary algorithms, the Particle Swarm Optimization algorithm (PSO) as the main exponent of the swarm algorithms and the Fireworks Algorithm (FA) as another variant of the swarm algorithms. The algorithms have shown an excellent behavior, providing solutions that combine the increase of energy efficiency with a very good profitability of the installation required to obtain that increase.

Numerical Simulation to Design Light-load Regenerative Brake Control System at Load Shutdown for DC-electrified Railway Systems

Numerical Simulation to Design Light-load Regenerative Brake Control System at Load Shutdown for DC-electrified Railway Systems

Optimal energy saving in DC railway system with on-board energy storage system by using peak demand cutting strategy

A problem of peak power in DC-electrified railway systems is mainly caused by train power demand during acceleration. If this power is reduced, substation peak power will be significantly decreased. This paper presents a study on optimal energy saving in DC-electrified railway with on-board energy storage system (OBESS) by using peak demand cutting strategy under different trip time controls. The proposed strategy uses OBESS to store recovered braking energy and find an appropriated time to deliver the stored energy back to the power network in such a way that peak power of every substations is reduced. Bangkok Mass Transit System (BTS)-Silom Line in Thailand is used to test and verify the proposed strategy. The results show that substation peak power is reduced by 63.49% and net energy consumption is reduced by 15.56% using coasting and deceleration trip time control.

Evaluation and Control of Stray Current in DC-Electrified Railway Systems

In urban electric railway transit systems, rails are used to navigate trains, as well as to provide the returning path of the train's electric current to the traction power substation (TPS). Due to electrical resistance of rails and the rail-to-ground conductivity, a part of the train's returning current to the TPS flows into the ground, which is called stray current, which causes different problems such as an increase of rail potential. In this regard, a model of an electric train with a TPS, running rail, and third rail is simulated in MATLAB/Simulink. In the simulated model, the amounts of stray currents in different soil types, with and without collection mats, are compared. Afterward, to calculate the amount of stray current in the presence of the stray current control method considering different soil types through finite–element (FE) method (FEM), a UIC54 rail with insulated fastening equipment is modeled in FEMM 4.2 and analyzed with 2-D FEM. Finally, a comparison of efficiency of stray current collection mats in different soil models for both simulation in MATLAB/Simulink and FEM is also presented. The obtained results verify the accuracy of the simulated and modeled system in real conditions of electric railways.

直流電気鉄道における省エネルギー化のための地上蓄電装置の電力制御

直流電気鉄道における省エネルギー化のための地上蓄電装置の電力制御

An Analytical Design Method for a Regenerative Braking Control System for DC-electrified Railway Systems under Light Load Conditions

A DC-electrified railway system that is fed by diode rectifiers at a substation is unable to return the electric power to an AC grid. Accordingly, the braking cars have to restrict regenerative braking power when the power consumption of the powering cars is not sufficient. However, the characteristics of a DC-electrified railway system, including the powering cars, is not known, and a mathematical model for designing a controller has not been established yet. Hence, the object of this study is to obtain the mathematical model for an analytical design method of the regenerative braking control system. In the first part of this paper, the static characteristics of this system are presented to show the position of the equilibrium point. The linearization of this system at the equilibrium point is then performed to describe the dynamic characteristics of the system. An analytical design method is then proposed on the basis of these characteristics. The proposed design method is verified by experimental tests with a 1kW class miniature model, and numerical simulations.

Fundamental Study on Saving Energy for Electrified Railway System Applying High Temperature Superconductor Motor and Energy Storage System

Induction motor instead of dc one has been applied widely for dc electric rolling stock because of the advantage of its utility and efficiency. However, further improvement of motor characteristics will be required to realize environment-friendly dc railway system in the future. It is important to study more efficient machine applying dc electric rolling stock for next generation high performance system. On the other hand, the methods to reuse regenerative energy produced by motors effectively are also important. Therefore, we carried out fundamental study on saving energy for electrified railway system. For the first step, we introduced the energy storage system applying electric double-layer capacitors (EDLC), and its control system. And then, we tried to obtain the specification of high temperature superconductor induction/synchronous motor (HTS-ISM), which performance is similar with that of the conventional induction motors. Furthermore, we tried to evaluate an electrified railway system applying energy storage system and HTS-ISM based on simulation. We succeeded in showing the effectiveness of the introductions of energy storage system and HTS-ISM in DC electrified railway system.

Analytic Evaluation of HTS Induction Motor for Electric Rolling Stock

Induction motor in place of DC one has been applied widely for DC electric rolling stock, because of the advantage of its utility and efficiency. However, further improvement of motor characteristics is crucial in order to realize environment-friendly DC railway system in the future. It is important to study more efficient machine; applying DC electric rolling stock for the next generation high performance system. Therefore, we have carried out fundamental study on reduction of energy consumption for electrified railway system with the aid of high temperature superconductor (HTS) technology. We have firstly tried to obtain the specification of HTS induction/synchronous motor (HTS-ISM), which is target HTS motor for the aforementioned purpose. Furthermore, we have investigated the relationship between the current transport property of HTS tape conductors and the torque characteristics of HTS-ISM. As the result, we have shown the possibility of the next generation DC electrified railway system with the use of HTS-ISM.

高温超電導電動機を電気鉄道に適用した電力負荷特性の向上に関する基礎検討

Induction motor instead of dc one has been applied widely for dc electric rolling stock because of the advantage of its utility and efficiency. However, further improvement of motor characteristics will be required to realize environment-friendly dc railway system in the future. Therefore, it is important to study more efficient machine applying dc electric rolling stock for next generation high performance system. For the first step, we reproduced torque characteristics of a dc motor that is utilized in an electric rolling stock, by analyzing specific current waveforms of dc substations. And then, we tried to reflect such torque characteristic to the conventional squirrel-cage induction motor based on the equivalent circuit. Furthermore, we tried to obtain the specification of high temperature superconductor induction/synchronous motor (HTS-ISM), which performance is similar with that of the above-mentioned conventional motors. We succeeded in showing the effectiveness of the introduction of HTS-ISM in DC electrified railway system.