• KEPCO Journal on Electric Power and Energy
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• 제6권4호
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• pp.399-404
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• 2020

There are many attempts to apply AI technology to diagnose facilities or improve the work efficiency of the power industry. The emergence of new machine learning technologies, such as deep learning, is accelerating the digital transformation of the power sector. The problem is that traditional power systems face security risks when adopting state-of-the-art AI systems. This adoption has convergence characteristics and reveals new cybersecurity threats and vulnerabilities to the power system. This paper deals with the security measures and implementations of the power system using machine learning. Through building a commercial facility operations forecasting system using machine learning technology utilizing power big data, this paper identifies and addresses security vulnerabilities that must compensated to protect customer information and power system safety. Furthermore, it provides security guidelines by generalizing security measures to be considered when applying AI.

• 전기학회논문지P
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• 제65권2호
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• pp.77-83
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• 2016

The electric quality of train is represented by voltage and current harmonics at PT(Ratio 25,000/15/[V]) which is located between pantograph and primary winding of train transformer. In this paper, voltage and current harmonics were measured on the test EMU(electric multiple unit)train with maximum speed of 180km/h in existing railway lines(chungbuk, Taeback, Honam). As a results of test, it is found that the electric quality of train depends on the mostly operation conditions which is accelerating mode and braking mode on each sections. Voltage THD is above all 3[%] and current harmonics is monitored from lowest Harmonic to highest Harmonic in case of accelerating mode. But, highest current harmonics is not monitored in case of breaking mode. The results in this paper can help to stabilize the power device and power converter of the test EMU train.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.470-475
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• 1998

A robust control technique is presented for a high performance control of a permanent-magnet(PM) synchronous motor. In order to deal with the internal and external disturbances of a PM synchronous motor drive system, a new feedback control structure is proposed. Since the dynamic behavior of the PM synchronous motor drive system is mainly concerned with the difference between the electro-magnetically developed torque and the load torque which generally referred to as an accelerating torque, the estimation and control techniques of this torque are introduced. The simulations and experiments are carried out for the DSP-based PM synchronous motor drive system and the results well demonstrate the effectiveness of the proposed control technique.

• Journal of Electrical Engineering and Technology
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• 제10권6호
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• pp.2442-2447
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• 2015

Because an electric railway vehicle is a large scale moving load, it can cause various kinds of power quality problems in the railroad power system. The power quality impacts are considered as the strong instantaneous stresses to the related power systems and can cause an accelerating aging and a malfunction of the power supplying components. Therefore, it is necessary to detect the small and intermittent symptoms mixed in the voltage waveform. However, they cannot be detected by the triggering functions of the existing power analyzers installed in the railway systems. This paper will examine the drawback of some fast detection tools and propose an advanced detecting and analyzing method based on a combined TEO and STFT algorithm.

• 한국철도학회논문집
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• 제12권4호
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• pp.582-589
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• 2009

회생에너지는 회생 전동차와 역행 전동차의 순간적인 오버랩 경우를 제외하고, 전동차내 저항기 또는 전차선의 저항에 의해 열로서 사라지게 된다. 에너지자정시스템은 전동차 제동시 발생되어 재활용되지 못하고 사라지는 회생 에너지를 에너지저장시스템에 저장하고 전동차가 역행할 때 에너지저장시스템으로부터 에너지를 공급하여 도시철도시스템에서 회생 에너지를 재할용하는 시스템이다. 동시에 역행과 제동하는 차량이 존재하지 않을 지라도 차량간 에너지의 완전한 교환이 이루어 질 수 있다. 따라서 에너지저장시스템은 에너지를 저장하고 재활용함으로서 에너지를 절감할 수 있는 유용한 장치이다. 에너지저장시스템은 운행시격과 관계가 깊은데, 운행 시격이 짧은 경우보다 큰 경우 전동차 회생시 회생 에너지가 모두 에너지저장시스템으로 저장되므로 저장된 에너지를 활용할 수 있어 도시철도 운영기관의 에너지 절감율이 높아지게 된다. 반대로 운행 시격이 짧을 경우 한 변전소 구간 내에 전동차 여러 편성이있을 수 있다. 이때 하나의 전동차 회생시 이 회생 에너지가 주변의 역행 전동차에 공급되면 에너지저장시스템으로 들어오는 회생 에너지는 적을 것이다. 따라서 본 논문은 에너지저장시스템을 적용하는데 있어서 악조건인 운행 시격이 국내에서 가장 짧은 서울메트로 2호선을 대상으로 에너지저장시스템 적용 효과를 에너지절감 측면에서 현장 실측과 시뮬레이션을 통해 분석하고자 한다.

• International Journal of Fluid Machinery and Systems
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• 제8권2호
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• pp.84-93
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• 2015

The computational cost is expensive for CFD-DEM simulation, a larger time step and a simplified CFD-DEM model can be used to accelerate the simulation. The relationship between stiffness and overlap in non-linear Hertzian model is examined, and a reasonable time step is determined by a new single particle test. The simplified model is used to simulate dilute pneumatic conveying with different types of bends, and its applicability is verified by compared with the traditional model. They are good agreement in horizontal-vertical case and vertical-horizontal case, and show a significant differences in horizontal-horizontal case. But the key features of particle rope formed in different types of bends can be obtained by both models.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 추계학술대회 논문집
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• pp.221-223
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• 2008

In Korean urban transit system, when the railcar starts, the electric power is absorbed from the line, and then the line voltage is instantaneously collapsed to provide a large accelerating torque. On the other hand, when the railcar brakes, the regenerative power is created and it increases the line voltage at the pantograph of the railcar. Therefor, by using the energy storage system near the train, the regenerated power can be saved to this system. The energy storage system is consisted of supercapacitor and a bidirectional DC-DC converter. In this paper, controller design of a bidirectional DC-DC converter based on pole-assignment is proposed. This method can be easy to design controller. Simulation results by using the calculated parameters are presented.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4685-4694
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• 2023

The ability to calculate the material density sensitivity coefficients of power with respect to the material density has broad application prospects for accelerating Monte Carlo-Thermal Hydraulics iterations. The second-order material density sensitivity coefficients for the general Monte Carlo score have been derived based on the differential operator sampling method in this paper, and the calculation of the sensitivity coefficients of cell power scores with respect to the material density has been realized in continuous-energy Monte Carlo code RMC. Based on the power-density sensitivity coefficients, the sensitivity coefficients of power scores to some other physical quantities, such as power-boron concentration coefficients and power-temperature coefficients considering only the thermal expansion, were subsequently calculated. The effectiveness of the proposed method is demonstrated in the power-density coefficients problems of the pressurized water reactor (PWR) moderator and the heat pipe reactor (HPR) reflectors. The calculations were carried out using RMC and the ENDF/B-VII.1 neutron nuclear data. It is shown that the calculated sensitivity coefficients can be used to predict the power scores accurately over a wide range of boron concentration of the PWR moderator and a wide range of temperature of HPR reflectors.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 Techno-Fair 및 추계학술대회 논문집 전기물성,응용부문
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• pp.135-136
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• 2008

In the paper, we evaluated insulation evaluation of EPDM insulator used often in power distribution lines in Korea. The selected samples for our experiment were three EPDM insulators for 22.9[kV] operated for 10 years or less. Using these samples, we observed the discharge pattern through accelerating experimental and analyzed discharge quantity using fractal theory. The validity of our fractal method were discussed and life time. reliability and quantitative analysis of the insulator was conducted through the method.

• Journal of the Optical Society of Korea
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• 제15권4호
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• pp.403-406
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• 2011

Here we report Airy beams coupled with waveguide modes. These waveguide Airy (WAiry) beams propagate through layered planar structures inheriting the characteristics of waveguide modes as well as those of Airy beams, such as diffraction-free and accelerating features. In particular, we focus on the WAiry beams associated with backward waveguide modes, showing that the backward feature can alter the trajectories of the WAiry beams significantly. Based on this, we propose a new scheme of waveguide-type polarization/power beam splitters.