The Load Model Composition Method in Power Systems Using Artifcial Neural Network

Rae‑Jun Park,송경빈,Kyungsang Lee 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.2

An accurate load model is necessary to improve the accuracy of power systems dynamic stability analysis. Recent studies to estimate accurate load model have mainly been focused on the measurement-based load modeling and the method to estimate a single representative load model called load model composition or load representation. The current load model used for the dynamic stability analysis in South Korea power system was aggregated with the measurement data from only three distribution stations. The proposed algorithm is the load model composition method based on artifcial neural network technique using more measurement data than the algorithm to estimate the current load model. The proposed load model composition method using the artifcial neural network uses the load composition ratio as the input value and the ZIP model parameter, which is the estimation result at each distribution line, as the output value. The measurement data to estimate the parameter were collected from 105 distribution lines of 9 substations. The performance of proposed algorithm was verifed for three perspectives in the case studies. The accuracy of the proposed algorithm has been improved by comparing the measurement data with the calculated result by using the proposed model. The mean absolute percentage error (MAPE) between the measured data and the proposed model is 1.7%. The proposed algorithm could be applied to estimate the representative load model using data measured at multiple measurement points.

Load-cell Sensor를 이용한 산지 토사유출량 계측의 현장 적용성 검토

서준표(Jun-Pyo Seo),이기환(Ki-Hwan Lee),김종엽(Dong-Yeob Kim),우충식(Choong-Shik Woo),이창우(Chang-Woo Lee),이헌호(Heon-Ho Lee) 한국산학기술학회 2018 한국산학기술학회논문지 Vol.19 No.1

최근 기후변화로 인한 집중호우, 태풍 등의 영향으로 산사태가 빈번히 발생하고 있다. 산사태를 예방할 수 있는 효율적인 방법은 사방사업이다. 이러한 사방사업의 효율성을 높이기 위해서는 산지에서 유출되는 토사량에 대한 정량적 측정이 필요하다. 본 연구에서는 산지계류에 Load-cell 센서를 설치하고, 분동테스트를 통하여 계류에서의 적용성과 재하 형태에 따른 출력값을 비교하였다. 개별 및 복합 하중시험을 실시한 결과, Site 1에서 평균 0.4kgf, Site 2에서 평균 0.6kgf 차이로 재하 형태의 영향은 낮게 나타났다. 또한 측정값의 정확도를 높이기 위해 하중계수를 산정하였다. 하중계수를 Load-cell 측정값에 적용하여 보정한 결과, 두 사이트에서 출력율이 각각 14.8%p, 24.6%p 상승하여 기준값에 근사하게 산정되었다. Load-cell 센서는 수위, 강우 등과 함께 시계열 분석을 통하여 산지 토사유출량을 정량적으로 산정할 수 있었다. 모니터링이 장기간 이루어진다면 산림유역에 대한 토사유출 매커니즘 구명에도 활용할 수 있을 것이다. 또한 Load-cell과 같은 센서를 산지 계곡에 적용함으로써 계측센서 등 관련분야 산업 발전에 기여할 수 있을 것으로 기대된다. Landslides occur frequently due to the effects of heavy rainfall and typhoons caused by climate change. Erosion control measures are needed to effectively prevent landslide damage. In order to improve their efficiency, it is necessary to quantitatively measure the sediment discharge from the mountain stream. In this study, a load cell sensor was installed in a mountain stream and the measured values were compared according to the applicability and load test type in the mountain stream. The result of the load test showed that the effect of the loading type (load test 1, 2) was low at average (loadings) of 0.4kgf and 0.6kgf at sites 1 and 2, respectively. The load factor was also derived by regression analysis to increase the accuracy of the measured values. According to the results of the load factor (normalized) to the load-cell measurement value, the output value increased by 14.8% and 24.6% in sites 1 and 2, respectively, and was calculated to be similar to the reference value. The load cell sensor enabled us to quantitatively estimate the amount of sediment discharge in the mountain stream through time series analysis with the water level and rainfall information. If the monitoring is carried out for a long time, it can be used to find the sediment discharge mechanism for the mountain stream. In addition, applying sensors such as load-cells to a mountain stream is expected to contribute to the development of related industries, such as the manufacturing of measurement sensors.

인지부하 기전과 평가방법에 대한 고찰

문성철(Sungchul Mun) 대한인간공학회 2018 大韓人間工學會誌 Vol.37 No.3

Objective: The aim of this study is to investigate physiological mechanisms underlying cognitive load and determine important factors that should be considered to quantify cognitive load. Background: Many studies have been conducted to propose measurement methods and effectively quantify effects that cognitive load has on user experiences, human performance, and human safety. However, few studies have been made to investigate which factors contributed to different findings of changes in physiological signals characterized with increasing cognitive load. Method: This study systematically reviews physiological mechanisms related to cognitive load based on working memory and selective attention theory. In order to determine the contributing factors to the different previous findings, subjective and objective measurement methods frequently and recently introduced in the literature have been overviewed. The contributing factors were determined by discussing the current advantages and limitations of the measurement methods. Results: Individual differences in inherent cognitive capability and differences in how to increase cognitive load affect human cognitive control, which results in the different findings of the physiological changes as a function of cognitive load. Minimizing the number of measures to quantify cognitive load is very important to address statistical issues such as increased false discovery rate. Conclusion: In order to evaluate accumulated cognitive load for ensuring human safety, objective measures indirectly reflecting neural connection between brain and heart can be considered while using multi-dimensional subjective measures such as NASA-TLX as an assistant method to validate the objective measures. In addition, EEG changes underlying cognitive load can be effectively measured by recording and analyzing brainwaves at just two midline electrodes (frontal and parietal) since the cortical regions are inextricably tied with cognitive control functions such as working memory and selective attention. Application: The findings in this overview are expected to provide practical guidelines to potential researchers who want to quantify cognitive load in their practical fields. With the updated knowledge of the measures, it can be possible to more precisely quantify cognitive load, determine contributing factors to the load, and then optimize various factors positively affecting man-machine interfaces.

Measurement-based Estimation of the Composite Load Model Parameters

Kim, Byoung-Ho,Kim, Hong-Rae The Korean Institute of Electrical Engineers 2012 Journal of Electrical Engineering & Technology Vol.7 No.6

Power system loads have a significant impact on a system. Although it is difficult to precisely describe loads in a mathematical model, accurately modeling them is important for a system analysis. The traditional load modeling method is based on the load components of a bus. Recently, the load modeling method based on measurements from a system has been introduced and developed by researchers. The two major components of a load modeling problem are determining the mathematical model for the target system and estimating the parameters of the determined model. We use the composite load model, which has both static and dynamic load characteristics. The ZIP model and the induction motor model are used for the static and dynamic load models, respectively. In this work, we propose the measurement-based parameter estimation method for the composite load model. The test system and related measurements are obtained using transient security assessment tool(TSAT) simulation program and PSS/E. The parameter estimation is then verified using these measurements. Cases are tested and verified using the sample system and its related measurements.

Measurement-based Estimation of the Composite Load Model Parameters

Byoung-Ho Kim,Hongrae Kim 대한전기학회 2012 Journal of Electrical Engineering & Technology Vol.7 No.6

Power system loads have a significant impact on a system. Although it is difficult to precisely describe loads in a mathematical model, accurately modeling them is important for a system analysis. The traditional load modeling method is based on the load components of a bus. Recently, the load modeling method based on measurements from a system has been introduced and developed by researchers. The two major components of a load modeling problem are determining the mathematical model for the target system and estimating the parameters of the determined model. We use the composite load model, which has both static and dynamic load characteristics. The ZIP model and the induction motor model are used for the static and dynamic load models, respectively. In this work, we propose the measurement-based parameter estimation method for the composite load model. The test system and related measurements are obtained using transient security assessment tool(TSAT) simulation program and PSS/E. The parameter estimation is then verified using these measurements. Cases are tested and verified using the sample system and its related measurements.

U50 풍력발전기 하중측정 실증연구

조주석(Cho, Joo-Suk),홍혁수(Hong, Hyeok-Soo),방조혁(Bang, Jo-Hyug),박진일(Park, Jin-Il),류지윤(Ryu, Ji-Yune),길계환(Gil, Kye-Hwan) 한국신재생에너지학회 2007 한국신재생에너지학회 학술대회논문집 Vol.2007 No.11

This paper addresses the measurement of structural loads on the Unison U50 wind turbine. The load measurement are carried out to determine the actual loads acting on a wind turbine. This is needed not only the certification process but also improving the technical development for prototype wind turbine. The measurement system is consists of measuring load, operating quantities and meteorological signal. All data that occur during the operating of a WT are stored the data acquisition system automatically. With using the measured data, load spectrum and equivalent load are evaluated according to IEC61400-13 Measurement of mechanical loads.

U50 풍력발전기 하중측정 실증연구

조주석(Cho, Joo-Suk),홍혁수(Hong, Hyeok-Soo),방조혁(Bang, Jo-Hyug),박진일(Park, Jin-Il),류지윤(Ryu, Ji-Yune) 한국신재생에너지학회 2007 신재생에너지 Vol.3 No.4

This paper addresses the measurement of structural loads on the Unison U50 wind turbine. The load measurement are carried out to determine the actual loads acting on a wind turbine. This is needed not only the certification process but also improving the technical development for prototype wind turbine. The measurement system is consists of measuring load, operating quantities and meteorological signal. All data that occur during the operating of a WT are stored the data acquisition system automatically. With using the measured data, load spectrum and equivalent load are evaluated according to IEC61400-13 Measurement of mechanical loads.

멀티미디어 스마트러닝 기반 학습 환경에서 정보 제시 유형이 한국어 학습자의 인지부하와 학습 이해도에 미치는 영향

이영희,이효재 서강대학교 언어정보연구소 2019 언어와 정보 사회 Vol.36 No.-

The purpose of this study is to find out what are the effects of the types of presentation on cognitive load and learning comprehension of learners of the Korean language in an educational environment based on multimedia smart learning. To do this, an experiment is conducted on 20 Korean language intermediate learners, each lasting 15 minutes. The experiment method is based on the physical responses of the participants of the experiment, which are observed using various types of presentations. Learning materials are divided into four types: type A is text, type is text and narration, type C is text and vision and type D is text, vision and narration. In order to determine the aspect of change in the learner’s human body during the experiment, their cardiac rate was measured. In addition, to carefully check their cognitive load when they are processing learning materials, a likert-type scale survey was conducted, a six item survey on the germane cognitive load, the intrinsic cognitive load and the extraneous cognitive load. To check the students’ understanding of the learning materials, their learning comprehension was tested using a multiple-choice questionnaire. The results of the experiment were analyzed using SPSS 20’s correlation analysis and a one-way ANOVA. No correlation was found between the type of presentation and the learners’ cardiac rate, their cognitive load and their learning. Type C created less of an intrinsic cognitive load and germane cognitive load compared to type A, yet the result is non-significant in a one-way ANOVA. This means that the type of presentation does not strongly influence the intrinsic cognitive load and germane cognitive load. In addition, type D and type C have less of an extraneous cognitive load than the other types. This result is meaningful, as the material, which is composed of hearing and vision material, has a lower cognitive load than just only vision material. Thus, when teaching material is planned based on smart learning, reducing the cognitive load of students should be considered.

Measurement-based Static Load Modeling Using the PMU data Installed on the University Load

Han, Sang-Wook,Kim, Ji-Hun,Lee, Byong-Jun,Song, Hwa-Chang,Kim, Hong-Rae,Shin, Jeong-Hoon,Kim, Tae-Kyun The Korean Institute of Electrical Engineers 2012 Journal of Electrical Engineering & Technology Vol.7 No.5

Load modeling has a significant influence on power system analysis and control. In recent years, measurement-based load modeling has been widely practiced. In the load modeling algorithm, the model structure is determined and the parameters of the established model are estimated. For parameter estimation, least-squares optimization method is applied. The model parameters are estimated so that the error between the measured values and the predicted values is to be minimized. By introducing sliding window concept, on-line load modeling method can be performed which reflects the dynamic behaviors of loads in real-time. For the purpose of data acquisition, the measurement system including PMU is implemented in university level. In this paper, case studies are performed using real PMU data from Korea Univ. and Seoul National University of Science and Technology. The performances of modeling real and reactive power behaviors using exponential and ZIP load model are evaluated.

Measurement-based Static Load Modeling Using the PMU data Installed on the University Load

한상욱,김지훈,이병준,송화창,김홍래,신정훈,김태균 대한전기학회 2012 Journal of Electrical Engineering & Technology Vol.7 No.5

Load modeling has a significant influence on power system analysis and control. In recent years, measurement-based load modeling has been widely practiced. In the load modeling algorithm,the model structure is determined and the parameters of the established model are estimated. For parameter estimation, least-squares optimization method is applied. The model parameters are estimated so that the error between the measured values and the predicted values is to be minimized. By introducing sliding window concept, on-line load modeling method can be performed which reflects the dynamic behaviors of loads in real-time. For the purpose of data acquisition, the measurement system including PMU is implemented in university level. In this paper, case studies are performed using real PMU data from Korea Univ. and Seoul National University of Science and Technology. The performances of modeling real and reactive power behaviors using exponential and ZIP load model are evaluated.