• 전기학회논문지
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• 제62권7호
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• pp.918-924
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• 2013

In a conventional power system, the frequency is recovered to the nominal value by the inertial, primary, and secondary responses of the synchronous generators (SGs) after a large disturbance such as a generator tripping. For a power system with high wind penetration, the system inertia is significantly reduced due to the maximum power point tracking control based operation of the variable speed wind generators (WGs). This paper proposes a virtual inertial control for a wind power plant (WPP) based on the maximum rate of change of frequency to release more kinetic energy stored in the WGs. The performance of the proposed algorithm is investigated in a model system, which consists of a doubly fed induction generator-based WPP and SGs using an EMTP-RV simulator. The results indicate that the proposed algorithm can improve the frequency nadir after a generator tripping. In addition, the algorithm can lead the instant of a frequency rebound and help frequency recovery after the frequency rebound.

• Food Science and Biotechnology
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• 제17권6호
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• pp.1327-1331
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• 2008

In order to determine whether peach contains compounds to regulate adipocyte differentiation, extracts of flesh/pericarp of yellow/white peach were prepared in water, ethyl acetate (EtOAc), or n-butanol solvent and determined for effects on adipocyte differentiation in C3H10T1/2 or 3T3-L1 cells. Interestingly, none of peach extracts has statistically significant stimulatory effect on the adipocyte differentiation in C3H10T1/2. Furthermore, the presence of EtOAc extract of white peach pericarp (WPP) was found to inhibit lipid accumulation in 3T3-L1 cells both by microscopic examination of Oil Red O-stained lipid droplets and by spectrophotometric quantification of extracted stain, indicating a significant inhibitory effect on adipocyte differentiation. The inhibition of lipid accumulation was accompanied by a significant decrease in the expression levels of adipocyte molecular markers-peroxisome proliferator-activated receptor $\gamma$, CAAT enhancer binding protein $\alpha$, and fatty acid-binding protein. Thus, this study determined that WPP EtOAc extract contains the inhibitory compound(s) on adipogenesis.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2236-2244
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• 2018

We make optimal consecutive offer curves for an energy storage system (ESS) integrated wind power producer (WPP) in the co-optimized day-ahead energy and regulation markets. We build the offer curves by solving multi-stage stochastic optimization (MSSO) problems based on the scenarios of pairs consisting of real-time price and wind power forecasts through the progressive hedging method (PHM). We also use the rolling horizon method (RHM) to build the consecutive offer curves for several hours in chronological order. We test the profitability of the offer curves by using the data sampled from the Iberian Peninsula. We show that the offer curves obtained by solving MSSO problems with the PHM and RHM have a higher profitability than offer curves obtained by solving deterministic problems.

• 전기학회논문지P
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• 제63권4호
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• pp.339-344
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• 2014

An offshore wind power plant (WPP) is very expensive and different from an onshore wind power system in many ways. There has been a continuous increase in the capacity of the offshore WPPs. Therefore it is essential to analyze the feasibility and reliability of the offshore wind power to optimize their redundancy. Besides, it is very important to study a planning for grid interconnection of adjacent offshore WPPs. This paper proposes a economic evaluation method to interconnect with adjacent offshore substations in offshore wind power grid. Also, we suggest the probabilistic reliability method to calculate a probabilistic power output of the wind turbine and a cost of the expected energy not supplied that is used as the reliability index of the power system.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2004년도 춘계학술발표대회
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• pp.461-464
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• 2004

무선 환경에서의 전자상거래가 빠르게 성장함에 따라 종단간 보안이 필요하다. 기존 WTLS를 사용하는 WPP 프로토콜에서는 종단간 사용자 안전성을 보장하고 있지 않다. 이 논문에서는 AIP프로토콜에서 사용자와 서비스 제공자간에 종단간 안전성이 제공되는 무선 인터넷 플랫폼에 독립적인 소액지불 프로토콜을 제안한다. 또한 인증기관이 인증과정에 참여할 경우 ID 기반 공개키 암호 시스템을 적용한 세션키를 생성하여 제안 프로토콜의 안전성 및 효율성을 분석한다

• Journal of Power Electronics
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• 제19권2호
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• pp.569-579
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• 2019

A robust controller is designed based on feedback linearization and sliding mode control to damp sub-synchronous control interaction (SSCI) in doubly fed induction generator (DFIG) wind power plants (WPPs) interfaced with the grid. A feedback-linearized sliding mode controller (FLSMC) is developed for the rotor-side converter (RSC) through feedback linearization, design of the sliding mode controller, and parameter tuning with the use of particle swarm optimization. A series-compensated 100-MW DFIG WPP is adopted in simulation to evaluate the effectiveness of the designed FLSMC at different compensation degrees and wind speeds. The performance of the designed controller in damping SSCI is compared with proportional-integral controller and conventional sub-synchronous resonance damping controller. Besides the better damping capability, the proposed FLSMC enhances robustness of the system under parameter variations.

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1408-1414
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• 2015

The renewable energies such as photovoltaic power, wind power and biomass have grown to a greater extent as decarbonization techniques. The renewable energies are interconnected to power systems (or electrical grids) in order to increase benefits from economies of scale, and the extra attention is focused on the Grid Code. A grid code defines technical parameters that power plants must meet to ensure functions of power systems, and the grid code determined by considering power system characteristics is various across the country. Some TSO (Transmission System Operator) and ISO (Independent System Operator) have issued grid code for wind power and the special requirements for offshore wind farm. The main purpose of the above grid code is that wind farm in power systems has to act as the existing power plants. Therefore wind farm developer and wind turbine manufacturer have great difficulty in grasping and meeting grid code requirements. This paper presents the basic understanding for grid codes of developed countries in the wind power and trends of those technical requirements. Moreover, in grid code viewpoint, the active power control of wind power is also discussed in details.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1993년도 학술발표집 지반진동 영향평가
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• pp.83-116
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• 1993

본 고는 쓰레기 매립장에서 동다짐을 시행할 시 발생하는 진동을 측정하고, 그 결과를 분석하여 쓰레기 매립지반의 동다짐 진동 특성을 고찰하였다. 진동특성은 크게 쓰레기 매립지반의 일반적 진동특성과 동다짐 조건 변화에 의한 진동특성의 2가지 측면으로 검토되었다. 그 결과 연구대상 쓰레기 매립지반의 기본적인 진동특성으로 충격지점 주위에서의 전단계수 G 행 17496~58320 t/m2, 감쇠비 D=14~58%, 탁월진동수 f=6~14 Hz 등으로 나타났다. 동다짐 조건 차이에 의한 진동특성으로는 타격회수가 증가될수록 cross hole시험에 의한 전단파 및 압축파의 속도가 중가하였으며, 타격지점으로 부터의 거리와 최대입자속도는 vPP = 5.08 [D/E]-1.4의 관계를 가지며, 쓰레기층 바닥에서는 반사파의 영향으로 진동의 진폭이 커지는 것으로 나타났다. 또한 진동에 의하여 지반이 개량되는 범위는 타격지점으로 부터 반경 약 6~10 m정도인 것으로 나타났다.

• 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.

• 한국환경보건학회지
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• 제7권1호
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• pp.33-41
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• 1981

This study was carried out to investigate Water Temperature, Residual Chlorine, Coliform Groups, and the Standard Plate Counts of Water Supply Areas provided by 7 Water Purification Plant (W.P.P) in Seoul from September 20, 1979 through October 20, 1979. The results were summarized below: 1) The mean water temperature of the 63 Water Samples was 19.8$\circ$C, the mean pH 7.18, and the mean residual chlorine concentration 0.52 ppm by each Water Supply Areas. There is no statistically significant differences between the WPP Areas, but there is significant differences between water supply areas. 2) 30(47.6%) out of the 63 Water Samples were Standard Plate Counts free and 33 Samples (52.4%) were contaminated by Standard Plate Counts. 30 (47.6%) out of 33 samples showed the existence of Standard Plate Counts less than 15 and the other 3 samples 15-30. 3) 2 (3.2%) out of the 63 Samples had the coliform. Those 2 Samples had 2 and 6 coliform group counts per 50ml respectively both of them were 0.1ppm in residual chlorine. 4) There is correlation among Water Temperature, pH, Residual Chlorine, Standard Plate Counts, and Coliform Groups. The Coefficient of Correlation(r) between Water Temperature & Residual Chlorine was 0.147, 0.240 between Water Temperature & Standard plate Counts and 0.215 between pH & Standard Plate Counts. These correlations are statistically no significant, But the correlation of coefficient between pH & Residual Chlorine was -0.291 which is showed significant correlation at p<0.05. The coefficient of correlation between Residual Chlorine & Standard Plate Counts was -0.441 which is showed Negative Correlation Statistically Significant difference at p<0.01.