Mobile QR Code QR CODE : The Transactions of the Korean Institute of Electrical Engineers

△ABC 삼각형과 Fermat tree의 관계에 대한 연구 Triangle △ABC and Length of Fermat tree

https://doi.org/10.5370/KIEE.2019.68.10.1169

김주철(Ju-Chul Kim) ; 이상중(Sang-Joong Lee)

The Fermat point minimally connects three points of ?ABC and resultant tree(=Fermat tree) is shorter than the path lengths connected via the excenter; circumcenter; centroid; orthocenter; and incenter; respectively. Fermat point and Fermat tree have a useful meaning in physical and engineering point of view. Finding Fermat point and Fermat tree can contribute to cost reduction for electric circuits; power transmission/distribution lines; and etc; especially for high cost conductors; e.g.; the superconducting power cable. This paper shows a brief review of a recently published article on Fermat point and presents detailed derivation procedure and application example of the formula by which the length of the Fermat tree can be directly calculated.

배전 선로별 특성 및 고객별 가중치를 고려한 자동개폐기 설치 방안 A Study on the Installation of Automatic Switches Considering the Characteristics of Distribution Feeder and Importance of Customer

https://doi.org/10.5370/KIEE.2019.68.10.1176

최미곤(Mi-Gon Choi) ; 윤상윤(Sang-Yun Yun) ; 최준호(Joon-Ho Choi) ; 안선주(Seon-Ju Ahn)

About 80% of power system faults occur in the distribution system. In Korea; distribution automation is progressing in order to minimize the outage time caused by faults; and thus the damage suffered by customers is gradually decreasing. The system average interruption duration index (SAIDI) is one of the typical reliability indices. Currently; Korean power system maintains a very high level of reliability in the SAIDI 3.5-minute level. However; KEPCO aims to lower the SAIDI to 2.5 minutes by 2020 for higher reliability. In this paper; five representative models of Korean distribution feeder are derived using the actual feeder property data and the outage data. In order to achieve the reliability goal efficiently; this paper also proposes a method to determine the priority of automatic switch installation according to the characteristics of the feeder and the customer. Finally; the umber of required switches and the cost are estimated using the proposed method and the feeder model.

1기 무한모선 계통의 선로 고장 감지를 위한 PI 관측기 설계 연구 A Study on PI Observer Design for Line Fault Detection of a Single Machine Infinite Bus System

https://doi.org/10.5370/KIEE.2019.68.10.1184

장수영(Su Young Jang) ; 김준우(Jun Woo Kim) ; 손영익(Young Ik Son) ; 남순열(Soon Ryul Nam) ; 강상희(Sang Hee Kang)

If a failure occurs in the power system; the electrical output of the generator changes; which can be regarded as a result of an external disturbance input. This paper presents a fault detection method and its application to the out-of-step protection problem by using a PI observer that estimates the magnitude of the disturbance. The performance of the designed observer is verified by computer simulations of the single-machine infinite bus power system. Simulation results show that the disturbance can be estimated successfully within the critical fault clearing time and the estimated disturbance can be used to predict whether the system maintains synchronization after the operation of the circuit breaker.

IEC 60599와 Duval Triangle Method 기반의 전문가시스템을 활용한 유입변압기의 결함 진단 기법 A Failure Diagnosis Method of Oil-Filled Transformer Using Expert System Based on Duval Triangle Method and IEC 60599

https://doi.org/10.5370/KIEE.2019.68.10.1189

이형진(Hyeong-Jin Lee) ; 윤광훈(Kwang-Hoon Yoon) ; 권동진(Dong-Jin Kweon) ; 김재철(Jae-Chul Kim)

DGA(Dissolved Gas Analysis) is a reliable method for detection of fault in oil-filled transformer. Among all the available techniques; IEC 60599 and DTM(Duval Triangle Method) is widely used. Most DGAs; including IEC 60599 and DTM; diagnose failure in the transformer through gas composition ratio. If the gas composition ratio is not calculated properly; the failure in the transformer can not be accurately diagnosed. Also; conventional techniques are difficult to consider the operating characteristics of the transformer. This paper proposes failure diagnosis technique of a transformer using expert system. The expert system was created from fuzzy logic based on IEC 60599 and DTM. The effectiveness of the expert system was verified by using MATLAB.

적응 퍼지 슬라이딩 모드 제어를 이용한 수차 발전 시스템의 성능 향상 Performance Improvement of a Hydraulic Turbine Generation System Using Adaptive Fuzzy Sliding Mode Control

https://doi.org/10.5370/KIEE.2019.68.10.1195

조대현(Dae-Hyun Cho) ; 박영수(Yeongsu Bak) ; 이교범(Kyo-Beum Lee)

This paper presents a performance improvement of a hydraulic turbine generation system using adaptive fuzzy sliding mode control. A dynamic response of current control on the part of generator should be improved to utilize differential pressure energy efficiently in hydraulic turbine generation system. Current ripple on the part of generator should be reduced in terms of noise and generator's life. Adaptive fuzzy sliding mode control scheme is applied to generator in order to improve the performance of a hydraulic turbine generation system. Sliding mode control is used to make the dynamic response improve and fuzzy logic is used to select a proper gain of sliding mode control to decrease chattering phenomenon in steady state. The effectiveness and performance of the proposed method for hydraulic turbine generation system are verified by simulation and experiment.

3-레벨 Hybrid ANPC 인버터의 양방향 운전 성능 분석 Performance Analysis on a Bidirectional Operation of a Three-Level Hybrid ANPC Inverter

https://doi.org/10.5370/KIEE.2019.68.10.1204

권봉현(Bong Hyun Kwon) ; 김상훈(Sang-Hun Kim) ; 배규철(Kyu-Chul Bae) ; 이교범(Kyo-Beum Lee)

This paper analyzes the performance of a three-level hybrid active neutral-point clamped (ANPC) inverter in a bidirectional operation. In the bidirectional operation where electrical energy flows from dc source to ac grid and vice versa; a weakness of neutral-point-clamped (NPC) inverter is an unequal loss distribution between four silicon (Si) switching devices. A leg of the hybrid ANPC inverter consists of the four Si insulated gate bipolar transistors (IGBTs) and two silicon carbide (SiC) active switches. Only two SiC metal oxide semiconductor field effect transistors (MOSFETs) take all the switching events using redundant switching states but the switching losses are reduced compared to that of NPC inverter. The hybrid ANPC topology has an advantage of almost the same power loss operating as a grid-connected inverter and rectifier. The validity of the power loss analysis in the bidirectional operation is verified by a PSIM simulation model and experiment in the grid-connected three-phase three-level voltage source inverter.

LSTM 모델기반 리튬이온 배터리 SOH 예측알고리즘 구현 Long Short Term Memory-Based State-of-Health Prediction Algorithm of a Rechargeable Lithium-Ion Battery for Electric Vehicle

https://doi.org/10.5370/KIEE.2019.68.10.1214

권상욱(Sanguk Kwon) ; 한동호(Dongho Han) ; 박성윤(Seongyun Park) ; 김종훈(Jonghoon Kim)

The state-of-health(SOH) information of a rechargeable lithium-ion battery is dependent on variable electric vehicle(EV)’s output features caused by frequent discharging/charging current; temperature; and state-of-charge(SOC) operating range. Above all; the most important thing to be checked is this SOH information should be correctly predicted for providing guarantee lithium-ion battery statuses to EV users. For this goal; critical aging factors that results in battery management system(BMS) performance should be obtained by various experiments and be reflected in a sophisticated study. Therefore; this paper introduces two steps for accomplishing an improved SOH prediction of a rechargeable lithium-ion battery. The first step is to perform aging factors extraction and their correlation analyses based on experiments using urban dynamometer driving schedule(UDDS) current profile. From this step; the long short term memory(LSTM) used to predict nonlinear and time-series datasets is newly proposed in the second step. According to the comparison with the recurrent neural network(RNN)-based SOH and clear verification; this paper provides the effectiveness of the SOH prediction.

순환수 펌프용 고압전동기의 절연내력 평가 Estimation of Dielectric Strength in High Voltage Motors for Circulating Water Pump

https://doi.org/10.5370/KIEE.2019.68.10.1222

이진(Jin Lee) ; 김형철(Hyungchul Kim) ; 신승권(Seung-kwon Shin) ; 김희동(Hee-Dong Kim)

To assess the deterioration condition of stator insulation diagnostic and overpotential tests were performed on two high voltage(HV) motors for circulating water pump(CWP). Two HV motors were installed per unit. Following the long term rewinding program; the diagnostic test was performed on two motors during the planning maintenance period. After completing the diagnostic test; overpotential test was done on the stator windings of HV motors. During the overpotential test; the No. 1 and No. 2 of HV motors failed at 8.8 kV and 7.9 kV; respectively. The dielectric strength of two motors was much lower than that expected for good quality coils (14.2 kV). Stator windings of two HV motors had deteriorated significantly. Almost all of failures were located in a line-end coil which exists at the exit of core slot. These motors were then rewound.

디지털 조광 기법을 사용한 LED 가시광통신 시스템 Visible Light Communication System with LEDs using Digital Dimming Scheme

https://doi.org/10.5370/KIEE.2019.68.10.1230

김혜수(Hea-Su Kim) ; 염정덕(Jeongduk Ryeom)

Depending on the conditions of the transmission data; the luminous flux changes in the visible light communication(VLC) system using light emitting diode(LED)s. Therefore; it is difficult to properly implement the lighting environment required by users; because of flicker or difficulty in maintaining the proper level of dimming. In this study; we proposed a new digital dimming technology using white LEDs to compensate for the increasing level of dimming caused by luminous flux of LEDs for data transmission; so that it can maintain the constant level of dimming. And we developed a VLC system using this technology. In the proposed digital dimming technology; the dimming level of dimmable LEDs and the variation in dimming level caused by the LEDs for data transmission are converted into binary values. Hence a new dimming level is created from their differences. The fluctuation of the dimming level due to the transmitted data signals is adjusted real-time in this technology. The dimmable LEDs and data LEDs are operated independently in the developed VLC system. In addition; by using bidirectional communication with LEDs for request signals; the transmitter and the receiver are synchronized easily and the multiple data transmission is possible. In order to verify the validity of this technology; we carried out the experiments to measure temperature by the sensor and transmit the measured temperature data using the developed system. From experimental results; rates of dimming variation of less than 2% have been achieved in every dimming level of over 10% using this technology. and the VLC system enabled telemetry for temperatures from ?55°C to 125°C.

직렬형 컨볼루션 신경망에 의한 SMD 부품의 조립 불량 분류 방법 ssembly Defect Classification of SMD Components by Cascade Convolutional Neural Network

https://doi.org/10.5370/KIEE.2019.68.10.1236

류종현(Jong-Hyun Ryu) ; 김영규(Young-Gyu Kim) ; 박태형(Tae-Hyoung Park)

In this paper; we propose the classification method of assembly defects in the surface mount technology process. We used a cascade convolution neural network which two convolutional neural networks were merged into one network; for assembly defect classification. The first network classifies whether the surface mount device (SMD) is defect or not. The second network classify the result of the first network more detail. We classified the SMD defects as six types using a cascade convolution neural network. Experiment result shows that the proposed method can optimize memory usage and improve classification accuracy compared to previous methods.

Haar-like Feature의 학습을 이용한 시각 홈 내비게이션 Local Visual Homing Navigation Using Gradient-Descent Learning of Haar-like Features

https://doi.org/10.5370/KIEE.2019.68.10.1244

김만동(Man-Dong Kim) ; 김대은(DaeEun Kim)

The autonomous mobile technology of mobile robots has been developed. Visual navigation is one of non-trivial problems and it has been tackled with biologically inspired models. Especially; ant navigation system inspires robot navigation. The visual cell structure of ants was modeled with Haar-like features. Those features can be obtained with computationally efficient process. In this paper; we handle visual homing navigation where an agent is supposed to return home after exploration in the environment. We apply a learning process based on gradient-descent algorithm to estimate the homing vector at an arbitrary position of a mobile agent. Our approach is simple but very effective to find the homing vector and its performance is better than the conventional algorithm. From our results; the Haar-like features in the snapshot images are sufficient to estimate the homing vector.

전완의 등척성 수축시 상대적인 중력토크를 고려한 근지구력시간 추정의 회귀모델 Regression Model to Estimate Endurance Time Using Relative Gravitational Torques During Forearm Isometric Contractions

https://doi.org/10.5370/KIEE.2019.68.10.1252

이기영(Kiyoung Lee) ; 장지훈(Jihoon Jang) ; 원종칠(Jongchil Won) ; 이근용(Keunyong Lee) ; 엄혁주(Hyokju Eum) ; 이상식(Sangsik Lee)

Despite of muscle group and posture variability; regression model to estimate endurance time have mainly developed by using the percentage of maximum voluntary contraction (%MVC). This paper presented two regression models by using the relative load intensity %MVC and the relative gravitational torque ratio %GTR (gravitational torque ratio) as a prediction variable for the biceps brachii muscle; and compared these models with the existing models. Sixty volunteers (30 females; 30 males) participated in this study; and performed isometric contraction exercises at 6 relative load intensities from 30% to 80% of MVC increasing by 10%; respectively; until their exhaustion to determine endurance times. Two regression models were induced from two relations between the measured endurance times and %MVC and between those and %GTR; and compared with the existing models by their correlation; determinant coefficients (r2) and mean square errors (MSE). The results demonstrated that the presented models were valid to estimate muscle endurance time by using %GTR of the biceps brachii muscle.

광용적맥파 미분 기반 수술 후 통증 평가 지표 Postoperative Pain Assessment Features Based on Derivative Photoplethysmogram

https://doi.org/10.5370/KIEE.2019.68.10.1258

석현석(Hyeon Seok Seok) ; 신항식(Hangsik Shin)

The purpose of this study was to develop pain assessment indices based on derivative photoplethysmogram for objective postoperative pain assessment. We obtained photoplethysmogram and surgical pleth index from 78 surgical patients in preoperative and postoperative conditions. Then; we extracted a total of 48 time and amplitude related candidate features from derivative photoplethysmogram. As a statistical result; 35 of the 48 basic features were significantly different (p<0.05) preoperation and postoperation. After normalization; the coefficient of variation of all candidate features decreased by 5.7%; time related features increased by 3%; amplitude related features decreased by 12.7%. In postoperative pain classification using logistic regression model; top 20 classification accuracy of 48 features including had an average of 64.9 ± 1.6% accuracy of pain assessment and the accuracy showed 0.9% higher than surgical pleth index.

배전계통 공급전압 기준 현황과 국제표준화 영향 연구 Status of Supply Voltage Standard and International Standardization Impact Study

https://doi.org/10.5370/KIEE.2019.68.10.1267

강현구(Hyun-Koo Kang)

In power distribution system; the magnitude of supply voltage has to be maintained within a certain range for ensuring the safety and performance of supply facilities and electrical devices. Accordingly; each countries have their own standards related to the maintenance range for supply voltages that electric service providers must comply with. In this paper; standards related to supply voltage are investigated; and in particular; Korean Industrial Standards which regulated in 220/380V±10% and; Electric utility act of Korea which regulated in 220±6% and 380V±10% are reviewed. Next; the background and constraints of these two regulations in Korea are discussed and changing the permissible range of supply voltage is proposed; similar to international standards is proposed. Lastly; in accordance with the international standardization; the effects on electrical devices and the hosting capacity of distributed energy resources are discussed.

IoT 표준 플랫폼 연동을 위한 자가용 전기설비 식별체계와 식별자 관리기술 연구 A Study on the Identification Scheme and Management Method of High Voltage Electric Installation Based on IoT Platform

https://doi.org/10.5370/KIEE.2019.68.10.1275

강현주(Hyunjoo Kang) ; 김성혜(Sung-Hei Kim) ; 심태형(Taehyoung Shim) ; 정상진(Sangjin Jeong) ; 안윤영(Yoon-Young An)

This paper presents the identification scheme and management method for high voltage electric installation on the customer side with the IoT platform. We introduced the combination of customer number; sensing name; sensing object name and the name of location categorization as the identification scheme. This paper also includes the procedure of adding; updating and deleting identifiers to deploy the identification scheme; and example tables of identifiers. We defined both the identifier of sensors and electric equipment respectively. We can increase the readability of the identifier associating functionality and location through the proposed identification scheme. Our goal is to know where the sensor device is installed; what it detects. We have also improved to handle DB table named as the same identifier assigned by the identification server.