Gangnam gu, South Korea
Gangnam gu, South Korea

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Namkung H.,Ajou University | Xu L.-H.,Institute for Advanced Engineering | Kang T.-J.,Ajou University | Kim D.S.,Korea Western Power Co. | And 2 more authors.
Applied Energy | Year: 2013

Coal gasification was carried out in order to verify the coal fouling tendency in the drop tube furnace (DTF), which can simulate an entrained-bed gasifier. Thirteen pulverized coal samples, in the range of bituminous and sub-bituminous, were utilized, and compared, with predictions using a wide range of empirical indices. Large discrepancies were noted in most cases, with respect to experimental results, ash deposition rates, and different indices. Some indices used for anticipating fouling tendency are not co-related with the results of this experiment. A newly approached index, which is especially important considering the diffusivity parameter, looks at the ratio of acid and alkali mineral matters injected into gasifier and heat flux, indicates that traditional expressions are modified to account for other parameters which influence the ash deposition phenomenon. The alternative index resulted in improved correlations between predictions and experimental observations. © 2012 Elsevier Ltd.

Ibrahim A.O.,University of Waterloo | Nguyen T.H.,Yeungnam University | Lee D.-C.,Yeungnam University | Kim S.-C.,Korea Western Power Co.
IEEE Transactions on Energy Conversion | Year: 2011

This paper proposes a low-voltage ride-through technique of a doubly fed induction generator (DFIG) wind turbine system using a dynamic voltage restorer (DVR). For effective control of the DVR, digital all-pass filters are used for extracting the positive-sequence component from the unbalanced grid voltage since they have the advantages of giving a desired phase shift and no magnitude reduction over conventional low- or high-pass filters. Using the positive-sequence component, the phase angles for the positive- and negative-sequence components of the grid voltage are derived. A control algorithm for the DVR that is dual voltage controllers only is implemented for the two sequence components in the dq synchronous reference frame. In order to achieve the power rating reduction of the DVR, the stator power reference for the DFIG is reduced during faults. In addition, a control scheme of pitch angle system is applied to stabilize the operation of the wind turbine system in the event of grid faults. PSCAD/EMTDC simulations show the effectiveness of the proposed technique and a feasibility of reducing the power rating of DVR for the fault ride-through capability of DFIG. The validity of the proposed control scheme for the DVR has also been verified by experimental results. © 2011 IEEE.

Choi J.,Gyeongsang National University | Park J.,Gyeongsang National University | Baek U.,Korea Western Power Co. | Ku B.,Daejin University | Cha J.,Daejin University
2010 IEEE 11th International Conference on Probabilistic Methods Applied to Power Systems, PMAPS 2010 | Year: 2010

A technique using a fuzzy search method which is based on fuzzy multi-criteria function has been proposed for GMS(generator maintenance scheduling) in order to consider uncertainties of forced outage rate of generators and multiobjective function. This paper evaluates the results of maintenance scheduling of the seven generation company obtained by the previous proposed method. Especially this paper focus on the GMS of Korea Western Power Co. The probabilistic reliability evaluation method was used to calculate production cost and used as criterion. © 2010 IEEE.

Oh T.,Gyeongsang National University | Choi J.,Gyeongsang National University | Cha J.,Daejin University | Baek U.,Korea Western Power Co. | Lee K.Y.,Baylor University
IEEE Power and Energy Society General Meeting | Year: 2011

This paper proposes a generator maintenance scheduling (GMS) problem with due consideration of minimizing CO2 emissions. The conventional objectives such as leveling the reserve rate, maximizing reliability and minimizing production cost have been effectively dealt with in the GMS problem until now. This paper considers minimizing CO2 emission as an additional objective in the GMS problem, where the CO2 emission is evaluated by using CO2 emission unit cost. The practicality and effectiveness of the proposed approach are demonstrated in the simulation for a real-size power system model in Korea in 2010. © 2011 IEEE.

Oh T.,Gyeongsang National University | Lim J.,Gyeongsang National University | Choi J.,Gyeongsang National University | Cha J.,Daejin University | And 2 more authors.
Midwest Symposium on Circuits and Systems | Year: 2011

The maintenance of generating units is implicitly related to power system reliability and has a tremendous bearing on the operation of the power system. A technique using a fuzzy search method which is based on fuzzy multi-criteria function has been proposed for GMS (generator maintenance scheduling) in order to consider multi-objective function. In this study, a new technique using combined fuzzy set theory and genetic algorithm (GA) is proposed for generator maintenance scheduling. The effectiveness of the proposed approach is demonstrated by the simulation results on a practical size test systems. © 2011 IEEE.

Park J.,Gyeongsang National University | Choi J.,Gyeongsang National University | Baek U.,Korea Western Power Co. | Cha J.,Daejin University | Lee K.Y.,Baylor University
Journal of Electrical Engineering and Technology | Year: 2010

A new technique using a search method which is based on fuzzy multi-criteria function is proposed for GMS(generator maintenance scheduling) in order to consider multi-objective function. Not only minimization of probabilistic production cost but also maximization of system reliability level are considered for fuzzy multi-criteria function. To obtain an optimal solution for generator maintenance scheduling under fuzzy environment, fuzzy multi-criteria relaxation method(fuzzy search method) is used. The practicality and effectiveness of the proposed approach are demonstrated by simulation studies for a real size power system model in Korea in 2010.

Chung I.-Y.,Korea Western Power Co. | Kim K.-T.,Korea Western Power Co.
55th ISA POWID Symposium 2012 | Year: 2012

With different time behavior of the boiler and the turbine causes an energy imbalance between two main control variable megawatts (MW) and throttle pressure to fluctuate, the throttle pressure lag and excessive overshoot in coordinated unit control cannot be avoided. There are two methods to improve process dynamic response. When the fuel is step up (step down) process delays of 3-5minutes occur before steam flow and pressure increase. By analyzing results, a model pressure set point and turbine set point can be developed that corresponds to the order of boiler response. A second method is to use a transport turbine master feedforward model to reduce pressure deviations at initial stage of load change. As a consequence, the coordinated unit control response is stable and the result is very good.

Lee S.,Sejong University | Kim J.,Sejong University | Lee J.,Sejong University | Lee S.-H.,Korea Western Power Co | Jeon E.,Sejong University
Asian Journal of Atmospheric Environment | Year: 2011

Korea-specific GHG emissions should be estimated correctly in order to ensure effective measurement of climate change variables. The use of country-specific data that reflects fuel and technology characteristics is needed for accurate GHG emissions estimation. Oxidation factors are used to convert existing data into equivalent GHG emissions, and changes in these oxidation factors are directly related to changes in emissions. As such, the oxidation factor is one of the most important variables in using country-specific data to determine GHG emissions. In this study, the oxidation factor of bituminous coal in large scale boilers was estimated using 4,527 data points sampled from eight large-scale boilers that had been using bituminous coal for two years. The average oxidation factor was determined to be 0.997, which is lower than the oxidation factor of 1 that is recommended by the IPCC G/L for large scale boilers when estimating national GHG emissions. However, an oxidation factor less than 1 is assumed for fluidized bed boilers, internal combustion engines, and other small-scale boilers. Accordingly, studies on oxidation factor estimation should be continued to allow for accurate estimation of GHG emissions.

Piao J.,Chungnam National University | Park S.,Chungnam National University | Park H.K.,Korea Western Power Co.
Proceedings of the 2010 International Conference on Mechanical, Industrial, and Manufacturing Technologies, MIMT 2010 | Year: 2010

The power plants are classified by the type of fuel and the type of operating condition. The most of the gas turbine power plants are usually operated under DSS (Daily Start-up and Shutdown) mode. To find out the root causes of the turbine failure, the study and inspection were performed in the plant. Based on the analysis, there are some serious damages on gas turbines generator rotor windings. The basic causes of the damage are thermal growth and abrasion. The damages occurred from squared type winding, retaining ring insulation difference, and short-turn. We use the ABAQUS program to analysis the problem for the damage and show how to improve.

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