• Journal of Electrical Engineering and Technology
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• 제8권1호
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• pp.1-10
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• 2013

The power industry is currently facing many challenges, due to the new environment created by the introduction of smart grid technologies. In particular, the large-scale deployment of electric vehicles (EVs) may have a significant impact on demand for electricity and, thereby, influence generation and transmission system planning. However, it is difficult to deal with uncertainties in EV charging loads using deterministic planning methods. This paper presents a two-stage stochastic decomposition method with Latin-hyper rectangle sampling (LHRS) to solve the integrated generation and transmission planning problem incorporating EV deployment. The probabilistic distribution of EV charging loads is estimated by Latin-hyper rectangle sampling (LHRS) to enhance the computational performance of the proposed method. Numerical results are presented to show the effectiveness of the proposed method.

• 한국수소및신에너지학회논문집
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• 제21권4호
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• pp.258-263
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• 2010

A numerical stack model has been developed to predict the temperature at a constant-load operation of molten carbonate fuel cell stacks. For the validity of the model, the simulated results with several boundary conditions were compared in the cell temperature data obtained from 75 kW class MCFC stack operation. It was shown that the simulated results with the existing boundary condition, which the stack outlet temperature was fixed at $650^{\circ}C$, didn't match well with the measured data. On the other hand, the stack model with the outlet temperature modified by the outlet manifold temperature measured from the stack under several electric loads was found to explain the measured cell temperature distribution well. The results show that the model can be used to predict the cell temperature distribution in the stacks by the measurement of the manifold outlet temperature.

• 전기학회논문지P
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• 제60권4호
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• pp.181-185
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• 2011

Due to the increasing of nonlinear loads such as converters and inverters connected to the electric power distribution system, and extensive application of harmonic generation sources with power electronic devices, disturbance of the electric power system and its influences on industries have been continuously increasing. Thus, it is difficult to construct accurate load model for active and reactive power in environments with harmonics. In this research, we develop current harmonics estimation method based on Extreme Learning Machine (ELM) with fast learning procedure for residential loads. Using data sets acquired from various residential loads, the proposed method has been intensively tested. As the experimental results, we confirm that the proposed method makes it possible to effective estimate current harmonics for various input voltage.

• Journal of Electrical Engineering and Technology
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• 제1권1호
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• pp.63-72
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• 2006

The purpose of this raper is to address the negative impedance instability in DC/DC converters. We present the negative impedance instability of PWM DC/DC converters loaded by constant power loads (CPLs). An approach to design digital controllers for DC/DC converters Is presented. The proposed method, called Power Alignment control technique, is applied to DC/DC step-down choppers operating in continuous conduction or discontinuous conduction modes with CPLs. This approach uses two predefined state variables instead of conventional pulse width modulation (PWM) to regulate the output voltage. A comparator compares actual output voltage with the reference and then switches between the appropriate states. It needs few logic gates and comparators to be implemented thus, making it extremely simple and easy to develop using a low-cost application specific integrated circuit (ASIC) for converters with CPLs. Furthermore, stability of the proposed controllers using the small signal analysis as well as the second theorem of Lyapunov is verified. Finally, simulation and analytical results are presented to describe and verify the proposed technique.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 D
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• pp.2310-2312
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• 2004

In Korea Electric Power Corporation (or KEPCO), several Demand-Side Management (or DSM) program have been carried out to effectively meet electric power demand at least costs by modifying customers electricity use patterns. As one of them, KEPCO applies low-priced night thermal-storage power service for heat appliances to facilitate efficient use of power facilities by shifting relatively high daytime demands to night hours to build loads during the off-peak periods. In the market of heat-storage type water-heater, electric water-heater has been mostly used, but it has low energy efficiency and needs high capacity electric equipments. So in order to replace these electric water heaters, 15 HP air-source heat pump water heater is developed in Korea Electric Research Institute (or KEPRI). This paper shows that measurement system for performance testing of heat pump water heater is established and heating capacity and performance is analyzed and measured for out-door environmental change.

• 전기학회논문지
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• 제63권2호
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• pp.217-223
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• 2014

Recently, various researches and projects about electric vehicles are in progress vigorously and continuously and it is expected to penetrate rapidly with the next a few years. This deployment will cause the change of load composition rate affecting on power system planning and operations. Therefore, a new load model should be developed integrating with electric vehicle loads. In this paper, the load composition rate of residential sectors is analyzed considering the deployment of this mobility load such as electric vehicles and a new diffusion model is proposed based on the classification of the replacement patterns. Additionally, electric vehicle charging loads are basically modeled by some individual load experiments to develop new load models for smart place and some new conceptual power systems such as micro grids.

• Journal of Power Electronics
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• 제12권1호
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• pp.157-163
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• 2012

Internet Data Centers (IDCs), which are essential facilities in the modern IT industry, typically have scores of MW of concentrated electric loads. The provision of an Uninterruptible Power Supply (UPS) is necessary for the power feed system of IDCs owing to the need for stable power. Thus, conventional IDC AC power feed systems have three cascaded power conversion stages, (AC-DC), (DC-AC), and (AC-DC), resulting in a very low conversion efficiency. In comparison, DC power feed systems require only a single power conversion stage (AC-DC) to supply AC main power to DC server loads, resulting in comparatively high conversion efficiency and reliability [4-11]. This paper compares the efficiencies of a 220V AC power feed system with those of a 300V DC power feed system under equal load conditions, as established by the Mok-Dong IDC of Korea Telecom Co. Ltd. (KT). Experimental results show that the total operation efficiency of the 300V DC power feed system is approximately 15% higher than that of the 220V AC power feed system.

• 대한전기학회논문지:전력기술부문A
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• 제50권2호
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• pp.90-95
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• 2001

Electric arc furnaces (EAFs) has a process to cause the degradation of the electric power quality such as voltage flicker. In order to adequately understand and analyze the effects on the power system from these loads, obtaining an accurate representation of the characteristics of the loads is crucial. In this paper, a mixed chaotic EAF model to represent the low frequency and high frequency variations of the arc current respectively has been proposed. The Lorenz system may contribute to the low frequency components of arc current and the logistic equation may contribute to the high frequency components, and the proposed mixed model will be a combination of both Lorenz and logistic model. The concept of chaotic parameters, such as chaotic resistance, inductance of admittance has been also proposed for the characterization of arc furnace operation and the highly nonlinear physical processes. The power quality indices are calculated from the simulated waveforms and compared with the actual power quality indices statistics in order to illustrate the model's capabilities.

• KEPCO Journal on Electric Power and Energy
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• 제2권1호
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• pp.83-88
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• 2016

This paper describes the test results of plant minimum stable load (Pmin) for Ilijan Power Plant. The test was conducted on May 13 through 14, 2015 to investigate the plant operating and equipment condition in accordance with "Ilijan Plant Performance Test Procedure on Plant Minimum Stable Load" [1]. This paper also contains the assessment of the impact of Pmin to plant operating parameters and possible technical operating issues when operating at lower loads and to recommend the safe minimum load operation of Ilijan per block. In addition, this paper describes the performance calculation results of efficiency and heat rate depending on the load level.

• 전기학회논문지P
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• 제59권4호
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• pp.364-371
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• 2010

In this paper, we propose the landscape lighting power control system with solar sell generator equipment for energy saving, and also which is included the landscape lighting power transformation device. The power transformation device can check inverse current in the power of the solar cell module and control the power of the battery. And we present the design of landscape lighting power control system. The power control system uses microprocessor with charging system and power transformation device. And also it can control the power of loads under consideration intensity of illumination. The landscape lighting loads are composed of LED(Lighting Emitting Diode) and HID(High Intensity Discharge)lamps. To evaluate property, we installed the solar cell array which generate three kilo watt power. Experimental results show that the proposed system can have stability and energy saving on the mixed configuration of electric loads with DC and AC lamps.