• Journal of Electrical Engineering and Technology
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• 제7권6호
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• pp.852-858
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• 2012

This paper describes evaluation results of the wind power penetration limit (WPPL) and the wind energy penetration (WEP) in the Mongolian central power system (MCPS). A wind power plant (WPP) in a power system possesses an output power limit because the power system must maintain a balance between the generation and consumption of electricity at all times in order to achieve an adequate level of quality. The instantaneous penetration limit (IPL) of wind generation at a load is determined as the minimum of the three technical constraints: the minimum output, the ramp rate capability, and the spinning reserve of the conventional generating units. In this paper, a WPPL is defined as the maximum IPL divided by the peak load. A maximal variation rate (VR) of wind power is a major factor in determining the IPL, WPPL, and WEP. This paper analyzes the effects of the maximal VR of wind power on the WPPL, WEP, and capacity factor (CF) in the MCPS. The results indicate that a small VR can facilitate a large amount of wind energy while maintaining a high CF with increased wind power penetration.

• 한국컴퓨터정보학회논문지
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• 제23권10호
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• pp.57-63
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• 2018

The operating system for an isolated microgrid, which is completely disconnected from the central power system, aims at preventing blackouts and minimizing power generation costs of diesel generators through efficient operation of the energy storage system (ESS) that stores energy produced by renewable energy generators and diesel generators. In this paper, we predict the amount of renewable energy generation using the weather forecast and build an optimal diesel power generation plan using a genetic algorithm. In order to avoid inefficiency due to inaccurate prediction of renewable energy generation, our search algorithm imposes penalty on candidate diesel power generation plans that fail to maintain the SOC (state of charge) of ESS at an appropriate level. Simulation experiments show that our optimization method for maintaining an appropriate SOC balance can prevent the blackout better when compared with the previous method.

• KEPCO Journal on Electric Power and Energy
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• 제6권4호
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• pp.413-418
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• 2020

초기 학습 데이터의 과적합으로 인한 전력망 상태예측 모델의 성능 감소를 방지하고 예측모델의 예측 정확도 유지를 통한 계속적인 현장활용을 위해서는 기계학습 모델의 예측 정확도를 지속적으로 관리할 필요가 있다. 이를 위해, 본 논문에서는 다양한 요인에 의해 끊임없이 변화하는 전력망 상태 데이터의 특성을 고려하여 예측모델의 정확성과 신뢰성을 높이고 현장 적용 가능한 수준의 품질을 유지하기 위한 기계학습 기반 전력망 상태예측 모델의 성능 유지관리 자동화 기법을 제안한다. 제안 기법은 워크플로우 관리 기술의 적용을 통해 전력망 상태예측 모델 성능 유지관리를 위한 일련의 태스크들을 워크플로우의 형태로 모델링하고 이를 자동화하여 업무를 효율화 하였다. 또한, 기존 기술에서는 시도되지 않았던 학습데이터의 통계적 특성 변화 정도와 예측의 일반화 수준을 모두 고려한 예측모델의 성능 평가를 통해 성능 결과의 신뢰성을 확보하고 이를 통해 예측 모델의 정확도를 일정 수준으로 유지관리하고 더욱 성능이 우수한 예측모델의 신규 개발이 가능하다. 결과적으로 본 논문에서 제안하는 전력망 상태예측 모델 성능 유지관리 자동화 기법을 통해 예측모델의 성능 저하문제를 해결하여 분산자원 연계 등 외부 환경의 변화에 유연한 예측모델 관리를 통해 정확성과 신뢰성이 보장된 예측 모델의 지속적인 활용이 가능하다.

• 전기학회논문지P
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• 제60권1호
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• pp.13-18
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• 2011

More and all-electric aircraft (AEA) carry many loads with varied functions. In particular, there may be large pulsed loads with short duty ratios which can affect the normal operation of other loads. In this paper, a converter with spilt capacitors and an improved adaptive controller is used as the Voltage Bus Conditioner (VBC) with the reduced capacitive storage to mitigate the voltage transients on the bus. The proposed converter allows the smaller capacitive storage. Also, the proposed controller has the advantage of requiring only one sensor and performing both the functions of mitigating the voltage bus transients and maintaining the level of energy stored. Experimental results are presented which verify the control principles and demonstrate the practicality of the approach.

• 한국수소및신에너지학회논문집
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• 제34권5호
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• pp.490-496
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• 2023

Unmanned aerial vehicles (UAVs) research is recently actively underway. Especially, fuel cell battery hybrid systems are widely used to overcome the limitations of continuous operation. However, fuel cell systems must be operated in combination with a battery due to their low specific output characteristics. Therefore, a hybrid power system model for UAVs is developed. The rule-based strategy is applied to the model to properly distribute power to batteries and fuel cells. As a result, the designed rule-based power distribution control operates UAVs while maintaining battery state of charge(SOC) at an appropriate level.

• 스마트미디어저널
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• 제8권4호
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• pp.72-79
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• 2019

The automated demand response (DR) program encourages consumers to participate in grid operation by reducing power consumption or deferring electricity usage at peak time automatically. However, successful deployment of the automated DR program sphere needs careful assessment of appliances load profile (ALP). To this end, the recent method estimates frequency, consistency, and peak time consumption parameters of the daily ALP to compute their potential score to be involved in the DR event. Nonetheless, as the daily ALP is subject to varying with respect to the DR time ALP, the existing method could lead to an inappropriate estimation; in such a case, inappropriate appliances would be selected at the automated DR operation that effected a consumer comfort level. To address this challenge, we propose a more proper method, in which all the three parameters are calculated using ALP that overlaps with DR time, not the total daily profile. Furthermore, evaluation of our method using two public residential electricity consumption data sets, i.e., REDD and REFIT, shows that our energy management systems (EMS) could properly match a DR target. A more optimal selection of appliances for the DR event achieves a power consumption decreasing target with minimum comfort level reduction. We believe that our approach could prevent the loss of both utility and consumers. It helps the successful automated DR deployment by maintaining the consumers' willingness to participate in the program.

• 한국수소및신에너지학회논문집
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• 제34권3호
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• pp.297-306
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• 2023

The frequency of fatal accidents that can occur at hydrogen refueling station was compared with the risk criterion for the general public suggested by the health and safety executive. If hydrogen refueling station meets the accident prevention facility standards presented in KGS Code FP216/217, it was confirmed that the risk of hydrogen refueling station was not at an unacceptable (intolerable) risk level. However, the risk of hydrogen refueling station due to small leak was analyzed as low as reasonably practicable. Therefore, methods for improving the safety instrumented function of hydrogen refueling station were reviewed. It was confirmed that the risk of hydrogen refueling station can be affected by the number of installed safety instrumentation system components, redundant architecture, mission time, proof test interval, etc. And methods for maintaining the risk of hydrogen refueling station at an acceptable risk level have been proposed.

• Journal of Electrical Engineering and Technology
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• 제12권3호
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• pp.1007-1015
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• 2017

This paper proposes a new control technique of energy storage system (ESS) for smoothing the active power of renewable energy sources (RES) such as photovoltaic and wind turbine generation. As the penetration of RES into grid increases, it is difficult to maintain the permissible level of power quality, that is, voltage and frequency fluctuation in power systems. To solve this problem, ESS control methods using low pass filter (LPF) have been proposed for mitigating the fluctuation of RES output. However, those have a lot of drawbacks which need to be supplemented. Hence, this paper presents the improved active power control with additional reactive power control for maintaining power quality properly. The proposed method minimizes the capacity of ESS to be required for smoothing RES output fluctuation through mitigation of phase delay problem in LPF. In addition, the voltage regulation improves by using additional reactive power control. The proposed method was verified through simulation analysis using PSCAD/EMTDC.

• 대한기계학회논문집A
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• 제24권2호
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• pp.481-488
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• 2000

This paper presents a new passive gravity -compensating system for articulated robot manipulators. The system, which consists of linear zero- free -length springs, achieves exact counterbalancing o f the gravitational loads throughout the entire range of the manipulator workspace, A basic concept is to design springs such that the total potential energy of the system including the manipulator and the springs should be maintained constant. A prototype has been developed for a direct-drive five-bar manipulator and its performances have been investigated. Results show that the gravity-induced motor torques have been reduced to less than 5% of those of uncompensated robots. Also, the gravity-compensating system simplifies the position control algorithm while maintaining the trajectory-tracking errors in a satisfactory level. In conclusion, the proposed system efficiently improves the manipulator performances by reducing the driving motor size and the energy consumption as well as by simplifying the control systems.

• 한국식품과학회지
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• 제7권1호
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• pp.7-10
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• 1975

국내(國內)의 변질미(變質米)에서 분리된 A. flavus var. columnaris가 저장곡류(貯藏穀類)에 오염(汚染)되었을 때 aflatoxin 생성(生成)에 의한 위험가능성(危險可能性)을 추구(追究)하기 위하여 일련의 실험이 수행되었다. 그 결과 쌀 저장중 aflatoxin의 생성에는 80%이상의 상대습도(相對濕度)가 요구되었고 일단 축적된 aflatoxin은 다른 미생물의 번식에 의하여 분해되어 50% 수준을 유지하였으며 다른 미생물이 공존하지 않는 경우는 aflatoxin의 대량축적이 일어났다. 곡류(穀類)에서의 aflatoxin생성량은 대두(大豆), 땅콩, 옥수수, 밀, 보리, 조, 쌀, 밀쌀, 녹두, 수수의 순서로 증가하였으며 곡립(穀粒)의 크기와 유지(油脂)의 함량에 영향되는 경향을 보여 주었다.