Changmu Lee

Harmonic analysis of the korean high-speed railway using the eight-port representation model

This paper presents a harmonic analysis model for the Korean high-speed railway. Since the harmonic current flows through the catenary system, the catenary system must be modeled exactly to analyze harmonic current amplifications and the total harmonic distortion. In the present work, the line constants of five conductors in the catenary system were calculated by the reduction method, and each subsystem, which consisted of the Korean high-speed railway system, was modeled by the eight-port representation. Simulation results using the proposed model were compared to field test data of the Korean high-speed railway system, and the accuracy of the harmonic analysis model was verified. Also, the harmonic characteristics of the Korean high-speed railway system are presented.

Energy Storage Application Strategy on DC Electric Railroad System using a Novel Railroad Analysis Algorithm

There is an increasing interest in research to help overcome the energy crisis that has been focused on energy storage applications in various parts of power systems. Energy storage systems are good at enhancing the reliability or improving the efficiency of a power system by creating a time gap between the generation and the consumption of power. As a contribution to the various applications of storage devices, this paper describes a novel algorithm that determines the power and storage capacity of selected energy storage devices in order to improve upon railroad system efficiency. The algorithm is also demonstrated by means of simulation studies for the Korean railroad lines now in service. A part of this novel algorithm includes the DC railroad powerflow algorithm that considers the mobility of railroad vehicles, which is necessary because the electric railroad system has a distinct distribution system where the location and power of vehicles are not fixed values. In order to derive a more accurate powerflow result, this algorithm has been designed to consider the rail voltage as well as the feeder voltage for calculating the vehicle voltage. By applying the resultant control scheme, the charging or discharging within a specific voltage boundary, energy savings and a substation voltage stabilization using storage devices are achieved at the same time.

Extended hydrogen-bonding lattice fluid theory for dimers and n-mers

Abstract The importance of contributions to real fluid properties by specific interactions has long been recognized. However, it is only recent since such effects have been incorporated into an equation of state. Still the description of some associating systems including organic acids presented difficulties. To explore the solution for such systems, the Veytsman’s statistics was extended for dimers and n-mers. Combining the extended statistics with the physical contribution of the present authors’ nonrandom lattice fluid model a new Helmholtz’s free energy equation was proposed and the resulting equations for pressure and chemical potential were derived. Vapor–liquid equilibria for binary mixtures of organic acids, alcohol, water and alkanes were calculated using the model. The results were found satisfactory for most systems when compared with experimental data.

Phase equilibria and properties of amino acids + water mixtures by hydrogen-bonding lattice fluid equation of state

Abstract For the modeling of activity coefficients and solubility of amino acids that are predominantly present as zwitterions in neutral aqueous solutions, excess Gibbs energy ( G E ) models and Helmholtz free energy models in which solvent is considered as a dielectric continuum have been used. In the present study, charges in zwitterions were considered as proton donors and acceptors. The hydrogen-bonding nonrandom lattice fluid equation of state (EOS) was adopted to account for the specific interactions as well as physical interactions. Parameters were fitted to vapor pressure and density for water and to activity coefficients and partial molar volumes at infinite dilution for amino acids. The calculated densities, activity coefficients and solubilities were in good agreements with data.

Field Tests of DC 1500 V Stationary Energy Storage System

The ESS(energy storage system, here after) for a DC 1500V was developed in 2009. A ESS was installed on the track of Daejeon HRT in 2010. The advantage of the ESS is that it can save the energy and plus stable the catenary voltage. This paper presents the energy saved by the ESS in Daedong substation. When the ESS is on/off, the field tests are performed.

A study on management system for reliability analysis in advanced EMU

Advanced Emu consist of a 6-car production was completed. Advanced EMU has been performed to verify the reliability, safety and so on. We built the PDM with system engineering technology. We constructed the management system in PDM for failure history data and analyzed the reliability of advanced EMU.

Simultaneous description of excess properties and vapor–liquid equilibria for associating mixtures by hydrogen-bonding lattice fluid equation of state

Abstract Since all residual thermodynamic properties can be calculated from an equation of state (EOS), an accurate EOS may also be used for the computation of excess properties and vapor–liquid equilibria (VLE) simultaneously. Cubic equations of state have been used with GE-mixing rules for associating mixtures. In the present study, the applicability of the hydrogen-bonding non-random lattice fluid model (NLF-HB) was investigated for the simultaneous correlation of VLE and excess properties of mixtures containing associating components. The optimized parameters for VLE and HE at room temperature gave reliable results for fitted properties. VE calculation showed large errors but the molar volume was accurate. The allowable range for the temperature extrapolation of the binary parameter was wider for VLE than for for HE.

Interface composition and reduced railway model to verify the effect of supercapacitor applied to railway system

As the importance of the improvement of energy efficiency is constantly increasing, a study has been done on the implementation of an energy storage system, to improve load efficiency, on the railway which has relatively large regenerative energy. The pre-existing regenerative energy not only has a low efficiency but also increases the catenary, which has a possibility to create problems in the electrical device voltage, during the regeneration process. In this paper, the improvement of the efficiency and stabilization of the catenary voltage by the implementation of an energy storage device is being discussed. The composition of the interface, control strategy and reduced railway model for simulation are being proposed.

Analysis of Multiple Factor of the Eddy Current Brake for Railway Application

This paper is analysis of multiple factor that should be considered in the design of an eddy current brake used as auxiliary brake system. The eddy current brake is a brake that generates a braking torque in a rotational direction opposite to the direction of the rotor by using a time-varying magnetic flux. The eddy current brake has the advantage of being able to take high current densities because this is used for a short period of time. Also, the eddy current brake is influenced by multiple factor such as number of slots, teeth width, coating thickness, air-gap length and so on. Therefore the eddy current brake was designed for use in railway application in consideration of the operation region and critical parameters.This paper is analysis of multiple factor that should be considered in the design of an eddy current brake used as auxiliary brake system. The eddy current brake is a brake that generates a braking torque in a rotational direction opposite to the direction of the rotor by using a time-varying magnetic flux. The eddy current brake has the advantage of being able to take high current densities because this is used for a short period of time. Also, the eddy current brake is influenced by multiple factor such as number of slots, teeth width, coating thickness, air-gap length and so on. Therefore the eddy current brake was designed for use in railway application in consideration of the operation region and critical parameters.

Management system of advanced EMU using PDM

The advanced EMU has been developed the core technologies. The advanced EMU consists of a 6-car. The advanced EMU has been performed to verify the reliability, safety and so on. This paper developed PDM(product data management) to make a system engineering of the advanced EMU.