• Title/Summary/Keyword: Operation Deviation

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Improved Frequency Mitigation of a Variable-Speed Wind Turbine (개선된 가변속 풍력발전기의 주파수 평활화)

  • Li, Mingguang;Yang, Dejian;Kang, Yong Cheol;Hong, Junhee
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.67 no.6
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    • pp.695-701
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    • 2018
  • For a power grid that has a high wind penetration level, when wind speeds are continuously fluctuating, the maximum power point tracking (MPPT) operation of a variable-speed wind turbine (VSWT) causes the significant output power fluctuation of a VSWT, thereby significantly fluctuating the system frequency. In this paper, an improved power-smoothing scheme of a VSWT is presented that significantly mitigates the frequency fluctuation caused by varying wind speeds. The proposed scheme employs an additional control loop based on the frequency deviation that operates in combination with the MPPT control loop. To improve the power-smoothing capability of a VSWT in the over-frequency section (OFS), the control gain of the additional loop, which is set to be inversely proportional to the rotor speed, is proposed. In contrast, the control gain in the under-frequency section is set to be proportional to the rotor speed to improve the power-smoothing capability while avoiding over-deceleration of the rotor speed of a VSWT. The proposed scheme significantly improves the performance of the power-smoothing capability in the OFS, thereby smoothing the frequency fluctuation. The results clearly demonstrate that the proposed scheme significantly mitigates the frequency fluctuation by employing the different control gain for the OFS under various wind penetration scenarios.

Development of Statistical/Probabilistic-Based Adaptive Thresholding Algorithm for Monitoring the Safety of the Structure (구조물의 안전성 모니터링을 위한 통계/확률기반 적응형 임계치 설정 알고리즘 개발)

  • Kim, Tae-Heon;Park, Ki-Tae
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.20 no.4
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    • pp.1-8
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    • 2016
  • Recently, buildings tend to be large size, complex shape and functional. As the size of buildings is becoming massive, the need for structural health monitoring(SHM) technique is ever-increasing. Various SHM techniques have been studied for buildings which have different dynamic characteristics and are influenced by various external loads. Generally, the visual inspection and non-destructive test for an accessible point of structures are performed by experts. But nowadays, the system is required which is online measurement and detect risk elements automatically without blind spots on structures. In this study, in order to consider the response of non-linear structures, proposed a signal feature extraction and the adaptive threshold setting algorithm utilized to determine the abnormal behavior by using statistical methods such as control chart, root mean square deviation, generalized extremely distribution. And the performance of that was validated by using the acceleration response of structures during earthquakes measuring system of forced vibration tests and actual operation.

A Process Detection Circuit using Self-biased Super MOS composit Circuit (자기-바이어스 슈퍼 MOS 복합회로를 이용한 공정 검출회로)

  • Suh Benjamin;Cho Hyun-Mook
    • Journal of the Institute of Convergence Signal Processing
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    • v.7 no.2
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    • pp.81-86
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    • 2006
  • In this paper, a new process detection circuit is proposed. The proposed process detection circuit compares a long channel MOS transistor (L > 0.4um) to a short channel MOS transistor which uses lowest feature size of the process. The circuit generates the differential current proportional to the deviation of carrier mobilities according to the process variation. This method keep the two transistor's drain voltage same by implementing the feedback using a high gain OPAMP. This paper also shows the new design of the simple high gam self-biased rail-to-rail OPAMP using a proposed self-biased super MOS composite circuit. The gain of designed OPAMP is measured over 100dB with $0.2{\sim}1.6V$ wide range CMR in single stage. Finally, the proposed process detection circuit is applied to a differential VCO and the VCO showed that the proposed process detection circuit compensates the process corners successfully and ensures the wide rage operation.

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A Study on Pipeline Network Analysis for Predicting Pressure and Flow rate Transients in City-gas Supply Lines (도시가스 공급라인의 압력 및 유량변화 예측을 위한 배관망 해석 연구)

  • Nam, Jin-Hyun;Cho, Chan-Young;Jang, Sung-Pill;Lim, Si-Hyung;Shin, Dong-Hoon;Chung, Tae-Yong
    • Journal of the Korean Institute of Gas
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    • v.12 no.2
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    • pp.85-91
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    • 2008
  • The deviation of measured pressures in pipeline networks from normal or reference pressures is useful information for judging the operation of the pipeline networks. A cost-effective monitoring of pipeline networks including a leak detection capability can be realized when transient pressure variation is accurately predicted using measured conditions at supply- and demand-sides of the networks. In this study, a pipeline network analysis program was developed based on one-dimensional flow equations for compressible fluids. The validity of the present analysis was demonstrated by simulating the flow in a straight pipeline and comparing the results with the previously reported ones. Pressure and flow rate transients in several simple city-gas pipeline networks were also analyzed to show the usefulness of the developed program.

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A Case Survey and Analysis of Complex with Theme of Green Care and Healing (치유테마단지 사례조사 분석)

  • Koo, Hee-Dong;Kim, Dae-Sik;Lee, Han-Jun;Lim, Hye-Ji
    • Journal of Korean Society of Rural Planning
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    • v.22 no.2
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    • pp.153-164
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    • 2016
  • Developed countries in agriculture like Netherlands, Belgium and England, have managed Green Care policy and project during the last decades. The needs in Green Care is also increasing as new growth power in rural area of Korea. This study investigated sites which are already operating as complex with Green Care theme. This study surveyed the operating conditions like type, scale, location pattern, purpose, customer and finance for cases of the complex. The period of the survey is from 2015. 8. 11 to 2015. 09. 10 for the 24 activated cases in aspect of operation and management. Among the 24 cases, 16 cases were classified as Green Care Complex which facilities are aggregated a place, and the other 8 cases as Green Care Cluster which are distributed at several places. The analysis result showed that there were apparent distinction among cases in total budget, costs of construction, capacity for guest, and the total number of annual visitors. Despite of the type and scale the accommodation cost, the number of workers, and amount of sales have small deviation in distribution of values, although the cases have various type of contents and scale of space. The result of this study can be used as data of bench marking to develop the Green Care Complex or Cluster in rural area.

Feasibility Study of Gamma Ray Transmission Technique in Distillation Column Using Monte Carlo Simulation (몬테칼로 전산모사를 이용한 감마선 투과계측 증류탑 진단기술의 타당성 연구)

  • Moon, Jinho;Kim, Jongbum;Park, Jang Guen;Jung, Sung-Hee
    • Journal of Radiation Industry
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    • v.7 no.2_3
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    • pp.115-119
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    • 2013
  • The density profile measurement technology by gamma transmission has been widely used to diagnose processes in the field of refinery and petrochemical industry. This technology can reveal a clue and position of abnormal phenomenon of industrial processes during their operation. In this paper, the feasibility of the gamma transmission technology for detecting changes in the amount of fluid in a distillation column was evaluated by using Monte Carlo simulations. The simulations assumed that $^{60}Co$ (1.17, 1.33 MeV) sources and NaI (Tl) detectors (${\Phi}5{\times}5cm$) are located in opposite sides of a column and it concurrently moves in vertical direction. To determine the dependency of a spatial resolution on aperture size of a collimator, the simulation model for a tray in a column were simulated with the aperture sizes of 1 and 2 cm. The thickness of the high density area including a tray and fluid was 7.6 cm in the simulation. The spatial resolution of the tray was 8.2 and 8.5 cm, respectively. As a result, it was revealed that the conventional density profile measurement technique is not able to show the deviation of liquid level on a tray in a column.

Effects of Self-Efficacy and Job Stress on Organizational Commitment among Clinical Dental Hygienists

  • Lee, Kyeong-Jin;Kim, Young-im
    • Journal of dental hygiene science
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    • v.19 no.1
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    • pp.60-66
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    • 2019
  • Background: This study aimed to provide basic data to establish a foundation for efficient operation of the organization by assessing the effects of self-efficacy and job stress (measured by self-efficacy, job demand, and job autonomy) on organizational commitment among clinical dental hygienists. Methods: This was a cross-sectional survey study that used a self-administered questionnaire to collect data. After institutional review board approval, a survey was conducted from January to May 2017, targeting dental hygienists working in dental clinics and hospitals. The final 199 questionnaires were analyzed with PASW 18.0 for Windows (IBM Corp.). The data were analyzed using mean and/or standard deviation t-test, one-way ANOVA, and multiple regression analysis. Results: The means for self-efficacy, job demand, job autonomy, and organizational commitment were $55.94{\pm}9.65$, $26.55{\pm}2.29$, $20.24{\pm}3.88$, and $49.49{\pm}8.39$, respectively. Along with self-efficacy, the other factors of organizational commitment among dental hygienists that were statistically significant included job autonomy, mean salary (2,500~2,990 thousand Korean won [KRW] and ${\geq}3,000$ thousand KRW), and employee welfare (good), which are sub-areas of the surface acting. In other words, it was found that the higher the mean salary, the better the employee welfare, the higher self-efficacy, and the higher the organizational commitment, and the explanatory power of the model was approximately 42.1%. Conclusion: These results suggest that the higher the self-efficacy, job autonomy, mean salary, and employee welfare, the higher the organizational commitment. In order to improve job demand among dental hygienists, it is necessary to establish an effective plan to improve job welfare, self-efficacy, and job autonomy.

Configuration of a 16-Element Array Antenna Design to Improve Signal Detection Performances (신호탐지 정확도를 높이기 위해 최적 배열형상을 고려한 16소자 배열안테나 설계)

  • Jang, Doyoung;Yoo, Sungjun;Wang, Jinchun;Lee, Jun-Yong;Choo, Hosung
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.30 no.6
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    • pp.438-444
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    • 2019
  • In this paper, we proposed a 16-element array antenna design to improve signal detection performances. The array antenna characteristics, such as mutual coupling, pattern deviation, and half power beamwidth of the active element, were examined to obtain an optimal spacing between individual elements. The single element of the array antenna consists of an indirect feed using L-shaped feed and shorted radiating patch to achieve a broadband operation. Root mean square(RMS) errors based on the incident angle of the signal were calculated to verify the signal detection performance of the proposed antenna. The results demonstrate that the proposed array antenna with optimal spacing is suitable for detecting interference signals with low RMS error.

Precision comparison of 3D photogrammetry scans according to the number and resolution of images

  • Park, JaeWook;Kim, YunJung;Kim, Lyoung Hui;Kwon, SoonChul;Lee, SeungHyun
    • International journal of advanced smart convergence
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    • v.10 no.2
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    • pp.108-122
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    • 2021
  • With the development of 3D graphics software and the speed of computer hardware, it is an era that can be realistically expressed not only in movie visual effects but also in console games. In the production of such realistic 3D models, 3D scans are increasingly used because they can obtain hyper-realistic results with relatively little effort. Among the various 3D scanning methods, photogrammetry can be used only with a camera. Therefore, no additional hardware is required, so its demand is rapidly increasing. Most 3D artists shoot as many images as possible with a video camera, etc., and then calculate using all of those images. Therefore, the photogrammetry method is recognized as a task that requires a lot of memory and long hardware operation. However, research on how to obtain precise results with 3D photogrammetry scans is insufficient, and a large number of photos is being utilized, which leads to increased production time and data capacity and decreased productivity. In this study, point cloud data generated according to changes in the number and resolution of photographic images were produced, and an experiment was conducted to compare them with original data. Then, the precision was measured using the average distance value and standard deviation of each vertex of the point cloud. By comparing and analyzing the difference in the precision of the 3D photogrammetry scans according to the number and resolution of images, this paper presents a direction for obtaining the most precise and effective results to 3D artists.

An Overheight Warning System for High Height Vehicles (전고가 높은 차량을 위한 통과 높이 경고 시스템)

  • Kim, Tae-Won;Ok, Seung-Ho;Heo, Gyeongyong;Lee, Imgeun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.24 no.7
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    • pp.849-856
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    • 2020
  • Recently, as the number of high-height vehicles such as double-decker buses has increased, collision accidents have occurred in bridges and tunnels due to the deviation from the designated routes and driver's carelessness. In the case of the existing front collision warning system, it is limited to vehicles and pedestrians, so it is difficult to use it as a pass height warning system for the high height vehicles. In this paper, we propose a system that generates a warning by determining the correlation and time series characteristics of data for each segment using multiple lidar sensors and then determining the possibility of collision in the upper part of the vehicle. Also, the proposed system confirmed the proper operation through a real-time driving test and a system performance evaluation by the Korea Automobile Testing & Research Institute.