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PSCAD/EMTDC에 의한 태양광전원 연계용변압기의 결상사고 특성 분석 A Study on Open Phase Fault Characteristics of Interconnecting Transformer for PV System Based on PSCAD/EMTDC

https://doi.org/10.5370/KIEE.2020.69.2.225

강갑석(Kab-Seok Kang) ; 이후동(Hu-Dong Lee) ; 태동현(Dong-Hyun Tae) ; 노대석(Dae-Seok Rho)

Recently, the installation of renewable energy sources(RES) such as PV system is being rapidly increased according to the Korean government policy of low-carbon green growth. However, when large scale PV systems are installed and operated in distribution system, open phase faults may be occurred at points of common coupling. Specifically, if open phase faults are occurred, the PV system should be stopped by prevention function of islanding of inverter, but it is reported that there are undetected cases for open phase circuit. And also, a phenomenon of open phase circuit may supply reverse power flow in grid-connected transformer. Therefore, this paper proposes modeling of open phase fault using PSCAD/EMTDC S/W and implements test devices to analyze cause of open phase circuit which is occurred at inverter side of PV system. Based on modeling and test devices, it is confirmed that the proposed methods are useful and practical tools for fault analysis of open phase circuit according to wiring connection and iron core structure in grid-connected transformer.

배전계통에서 전압상승 완화를 위한 재생 발전기의 새로운 무효전력제어 전략 A Novel Reactive Power Control Strategy of Renewable Generators for Voltage Rise Mitigation in Distribution Network

https://doi.org/10.5370/KIEE.2020.69.2.235

김수빈(Soo-Bin Kim) ; 송승호(Seung-Ho Song) ; 강용철(Yong-Cheol Kang)

To achieve both network losses reduction and voltage regulation, a reactive power voltage control method is proposed, which is based on the point of common coupling (PCC) voltage and the active power of renewable generators (RGs). The proposed method utilizes the voltage at the PCC and the active power output information, which enables improved voltage regulation capability while reducing network losses. The proposed reactive power control method was simulated using actual solar power output data in a radial feeder model with multiple RGs connected. The simulation results show that the proposed control strategy maintains the grid voltage within the normal operation range and the network losses are less than the conventional control strategies.

커뮤니티급 전력수요 예측 정확도 향상을 위한 와 Scaled RMSE Shewhart Control Chart 기반의 비정상 참고일 감지 방안 Scaled RMSE and Shewhart Control Chart-based Abnormal Reference Day Detection Method to Improve the Forecasting Accuracy of Community-level Power Demand

https://doi.org/10.5370/KIEE.2020.69.2.245

김치연(Chi-Yeon Kim) ; 김채린(Chae-Rin Kim) ; 김동근(Dong-Keun Kim) ; 최형진(Hyeong-Jin Choi) ; 박시삼(Si-Sam Park) ; 조수환(Soo-Hwan Cho)

Accurate short-term power demand forecasting is a key-technique for the optimal generator operation planning and the power market pricing. Especially, the accurate demand forecasting ability in city or community level micro-grids is more essential for local power utilities to obtain the optimal solutions for the economic energy mix and the daily energy supply planning. The forecasting error can increase the cost of purchasing additional power, cause economic losses by wasting energy, and exacerbate the system reliability. In order to minimize the forecasting error in city or community microgrid, the following two factors should be considered. One is how to determine the similar days whose time patterns of daily power demand are similar to each other and the other is how to detect and remove abnormal reference days of the similar days. Since the first issue applying the scaled RMSE method has been dealt in the previous related paper, we will summarize it in chapter 2 and focus at the second issue applying the control chart technique. In this paper, an abnormal reference days detection method based on the quality control charts such as , , and  ? will be proposed and the detection performances will be compared and analyzed by simulations with actual annual demand data.

선형 마그네틱 기어의 추력 리플 저감을 위한 특성 해석 Characteristic Analysis of Force Ripple Reduction in Linear Magnetic Gear

https://doi.org/10.5370/KIEE.2020.69.2.258

우종현(Jong-Hyeon Woo) ; 서성원(Sung-Won Seo) ; 방태경(Tae-Kyoung Bang) ; 최장영(Jang-Young Choi)

Abstract should not exceed 200 words and should concisely state what was done, how it was done, principal results, and their significance and/or contributions. It should be also noted that abstract should not contain any equations, references, or footnotes. This article plays the role of a template as well as the guidelines for prospective authors who will have to prepare the final manuscript accepted for publication by KIEE transactions on systems and control. Hence, it is not required to adhere to these instructions in submission of your works for initial review.

내부 구조물과 외함의 재질에 따른 배전용 변압기의 표류부하손 영향 Impact Stray Load Loss on Distribution Transformer Depending on Material of Clamp and Tank

https://doi.org/10.5370/KIEE.2020.69.2.265

김상현(Sang-Hyun Kim) ; 이향범(Hyang-Beom Lee)

In this paper, the influence of the material of the clamp and the tank is analyzed for reducing the stray load loss for 100kVA transformer. In order to select the appropriate materials for the clamp and the tank of the transformer, analysis was carried out through FEM. SS400, Aluminum, and high manganese steel are used for the comparison and analysis. A total of nine models were analyzed. The use of high manganese steel, which has relatively low conductivity and relative permeability, showed a 31.55% reduction effect compared with SS400.

동축 마그네틱 기어의 자석 재질에 따른 최적효율 설계 및 비교 Optimal Efficiency Design and Comparison according to Magnet Materials of Coaxial Magnetic Gear

https://doi.org/10.5370/KIEE.2020.69.2.271

박의종(Eui-Jong Park) ; 정상용(Sang-Yong Jung) ; 김용재(Yong-Jae Kim)

Various studies have been conducted since magnetic gears can replace mechanical gears and the non-contact power transmission characteristics of magnetic gears have emerged. Recent studies use rare earth permanent magnets to represent the high power density of magnetic gears. However, the conductive properties of the rare earth permanent magnets resulted in a decrease in efficiency. Using the ferrite permanent magnets, which have no conductivity, were difficult to compete in size. This paper presents the basic design of magnetic gears using three permanent magnet (NdFeB, Nd-bonded, Ferrite) materials and shows the results of size, efficiency characteristics.

GaN HEMT 1.5kW LDC 기반 차량용 급 고효율 구현 Implementation of High-efficiency 1.5kW LDC for xEV using GaN HEMT

https://doi.org/10.5370/KIEE.2020.69.2.276

김현빈(Hyun-Bin Kim) ; 김종수(Jong-Soo Kim)

This paper deals with how to maximize the efficiency of LDC for xEV by using GaN HEMT and improving control method. First, the characteristics of GaN HEMT are analyzed in detail and the considerations for applying them instead of conventional silicon MOSFETs to the primary side of LDC are described in detail. Second, the possibility of a phase shedding control scheme is presented to improve the low light-load efficiency due to the high step-down ratio of the LDC. Finally, the analysis results of considerations applying GaN HEMT-based synchronous rectifier instead of conventional fast recovery diodes to the secondary side of LDC are presented. The feasibility of the proposed efficiency maximization strategies is verified through a 1.5kW LDC laboratory prototype. The experimental results show high efficiency of more than 95% from 150W load condition and the maximum efficiency of 96.2%.

카메라 이미지 플리커링 해결을 위한 를 이용한 대 드라이버의 GaN HEMT MHz LED PWM 디밍 특성 PWM Dimming Characteristics of the MHz band LED Driver Using GaN HEMT for the Solution of Camera Image Flickering

https://doi.org/10.5370/KIEE.2020.69.2.283

인치각(Chi-Gak In) ; 김준석(Joohn-Sheok Kim) ; 오용승(Yong-Seung Oh) ; 오원석(Won-Seok Oh) ; 조규민(Kyu-Min Cho)

In this paper, we analyze the cause of flickering for the still image and moving image of the camera to solve the flickering image problem under the LED lighting environment controlled by PWM. Through computer simulation, the exposure dose according to the operating conditions of the camera such as exposure time, moving picture frame rate, and shutter opening instant and dimming control conditions of the LED lighting such as PWM frequency and duty is derived. A high-speed PWM LED driver using GaN HEMT, a high-speed switching element, is proposed as a countermeasure, and its PWM dimming characteristics are evaluated. Experiments with three kinds of LED boards are performed. As a result, it is confirmed that 55.5 V, 40 W LED board and 220 V, 170 W LED board have an excellent linear illuminance control characteristics in PWM dimming of the MHz band. Moreover, it is confirmed that the flickering image problem does not occur even in the high-speed 960 fps shooting video in case of high-speed PWM over 1 MHz.

하이퍼튜브 추진용 케스케이디드 브리지 멀티레벨 인버터 설계 Design of the Cascaded H-bridge Multi-level Inverter for HyperTube Propulsion

https://doi.org/10.5370/KIEE.2020.69.2.297

조정민(Jeong-Min Jo) ; 이광주(Kwang-Joo Lee) ; 이석영(Seok-Young Lee) ; 최수용(Su-Yong Choi) ; 이창영(Chang-Young Lee) ; 이관섭(Kwan-Sup Lee)

This paper presents the propulsion system based on the cascaded H-bridge multi-level inverter for the HyperTube propulsion. Simulation results show that the proposed system has high efficiency under various modulation index condition of the inverter when compared to a two-level inverter and a three-level inverter. In order to confirm the feasibility of the proposed system as a HyperTube propulsion system, a miniature 5-level cascaded H-Bridge inverter is designed and test results show that such an inverter is expected to be useful for HyperTube based on long-stator linear motors.

고성능 슈퍼 커패시터용 전극재료의 결합재가 없는 배터리 타입 나노시트로 정렬된 CuSe 나노구조의 합성 Facile Synthesis of Binder-free Battery-type Nanosheet Arrays-like CuSe Nanostructures as Advanced Electrode Material for High-performance Supercapacitors

https://doi.org/10.5370/KIEE.2020.69.2.304

김상효(Sang-Hyo Kim)

Hierarchical CuSe interconnected nanosheet arrays (NSAs)-like structures are grown on nickel foam via a facile and low-cost chemical bath deposition technique. These CuSe electrodes are used as an efficient electrode material for supercapacitor without using any binders or conducting polymer additives. The structural, composition and morphological behaviors of the CuSe electrodes are characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy methods. The CuSe NSAs provide the abundant active sites, high conductivity and rapid charge transport, which resulting the low-charge transfer resistance at the interface of electrode-electrolyte. Cyclic voltammetry and galvanostatic charge-discharge plateaus from the CuSe electrode exhibit the Faradic battery-type redox behavior, which is distinct form the profiles of carbon based materials. As a battery-type electrode, the NSAs-like CuSe nanoarchitectures exhibits the outstanding electrochemical performances with a high specific capacity ( 192.93 mA h g-1at2Ag-1) and excellent cycling life( 95.23% at ∼ ∼ 6Ag-1over3000cycles), respectively. Therefore, with the above findings, CuSe material has remarkable application potential in supercapacitors and could be effectively applied in other energy storage technologies.

고전적인 차 룬게 쿠타 방법을 이용한 피킹 스위치 수치 해석 Numerical Analysis of a Peaking Switch using the Classical Fourth-order Runge-Kutta Method

https://doi.org/10.5370/KIEE.2020.69.2.309

노영수(Young-Su Roh)

A peaking switch plays a crucial role reducing the rise time of the high voltage output pulse from the Blumlein pulse forming line. An equivalent circuit in which the peaking switch is modelled as a series combination of inductor and resistor in parallel with a capacitor, is used to generate the output voltage waveform and to numerically analyze how much the rise time of the output voltage pulse changes at various conditions under the assumption that the input voltage is a Gaussian pulse whose rise time is 5 ns. ∼ Simultaneous ordinary differential equations for variables such as arc current, resistance, and output voltage, are derived from the equivalent circuit, and solved by the classical forth-order Runge-Kutta method. Simulation results show that the rise time can be extremely reduced up to 425 ps at a pressure of 17 atm

송전용 자기 애자의 절연 내력 및 시멘트 열화에 대한 연구 A study on the Insulation Strength and Cement Corrosion of Porcelain Insulators in Power Transmission Line

https://doi.org/10.5370/KIEE.2020.69.2.316

손주암(Ju-Am Son) ; 최인혁(In-Hyuk Choi) ; 구자빈(Ja-Bin Koo) ; 김태용(Taeyong Kim) ; 이준신(Junsin Yi)

Porcelain insulators for transmission play an important role in isolating and supporting power lines and transmission towers. There is a lack of research on porcelain insulators for transmission compared to other power installations. Therefore, in this paper, the measurement and analysis of insulation strength and cement corrosion of porcelain insulators for power transmission were carried out. Domestic pollution level calculation is determined by the equivalent salt deposit density (ESDD). In this paper, insulation strength measurement and cement corrosion analysis were performed by extracting 36,000lbs porcelain insulators from 427.3m, 469.9m and 571m away from the coast. As a result, the average insulation strength of porcelain insulators, 427.3m away from the coast, was measured as 29,400M . The insulation strength of porcelain insulators 571m away from the coast was measured at Ω 2,500M . The measurement results show a 11.8-fold decrease in the insulation strength in porcelain insulators that are relatively far Ω from the coast and closer to the mountainous region than the insulation strength of porcelain insulators near the coast. As a result of cement corrosion measurement of the sample, hydrogen ion concentration(pH) was measured to estimate degradation. Cement corrosion of porcelain insulators that are extracted from the research was measured at pH 13 of porcelain insulators, 427.3m from the coast. The pH of porcelain insulators at 469.9m away was measured at 11, and the pH of porcelain insulators 571m away from the coast and close to the mountainous area was measured at 7. Stress accumulation of cement with humidity is considered to be more important factors for reducing the insulation strength of porcelain insulators to determine cement corrosion than salt in coastal areas.

잡음 최소화를 위한 새로운 알고리즘이 적용된 비접촉식 인간호흡 유무 판별 시스템 Robust Non-contacting Human Respiration Signal Detecting System By Applying a New Algorithm to Minimize Noise

https://doi.org/10.5370/KIEE.2020.69.2.322

배재민(Jae-Min Bae) ; 박순우(Soon-Woo Park) ; 한희제(Hee-Je Han) ; 김찬우(Chan-Woo Kim) ; 김홍준(Hong-Jun Kim)

In this paper, we conducted an experiment regarding a non-contacting respiration detection system by applying a new algorithm to minimize the noise effect. A Doppler radar in the 5.8GHz band with a series algorithm which includes a Savitzky-Golay Filter and a signal integration process to minimize the noise effect was used for the measurement of the human respiration signal at 1.2m distance. This signal processing algorithm, including the removal of DC signals from direct down-conversion and noise suppression, is faster than the previously reported system in the literature, and allows for a robust determination of the presence of the respiratory signals for a variety of situations. The results show the final signal magnitude ratio is at least 3.1 times bigger when the human being is present. compared to when the human being is absent. We have compared signals before and after the proposed signal processing algorithm and verified that the proposed system can be more robust to detect the human respiration signal even in a very noisy environment. We believe the proposed system can be very reliably applied to a detection of human being in many casualty incidents.

결함 검출을 위한 임베디드 딥러닝 시스템 Embedded Deep Learning System for Defects Detection

https://doi.org/10.5370/KIEE.2020.69.2.325

이건영(Keon Young Yi) ; 정선재(Sunjae Jeong) ; 서기성(Kisung Seo)

A machine vision based industrial inspection requires little computation time and localizing defects robustly with high accuracy. Recent mobile and embedded systems require computationally efficient machine intelligence with a deep learning model. In order to improve detection performance and processing time, various network modification methods are proposed. The experiments for defect detection on the metal surfaces data are executed using the various YOLO networks on embedded GPU system Nvidia Tx-1. The results for detection performance and inspection time are compared and analysed. Among them, modified YOLOv2-tiny model shows a better performance in both detection rate and fps

영상 기반 드론 식별 및 위치 표시 Image Based Identification and Localizing of Drones

https://doi.org/10.5370/KIEE.2020.69.2.331

이건영(Keon Young Yi) ; 서기성(Kisung Seo)

As commercial drones have been widely used, concerns for collision accidents with people and invading secured properties are emerging. The identification and localization drone is a challenging problem. DroneTracker, commercially available SW, for two dones with Inspire2, Phantom4Pro is tested but the performances of identification and localization are very low. We have suggest a image processing based identification and localization method for drones using the relationship between drone image size and real distance. It is tested for same experimental environments. We have obtained not only clear identification of each drone, but much superior performances of identification and localization. Furthermore the exactness of tracking is very close to the original tracking path.

이미지 특징점 가중치 학습을 통한 내비게이션 Local Navigation Using Weight Learning on Image Features

https://doi.org/10.5370/KIEE.2020.69.2.337

최종하(Jong-Ha Choi) ; 김대은(DaeEun Kim)

Visual navigation is a challenging subject in robotics, which is involved estimating the target position and direction at an arbitrary location. In this study, we follow the snapshot model, a bio-inspired model to determine the target direction with the snapshots taken at the current location and the target location. From the snapshots, we collect landmarks with three different features, the corner landmarks with SURF (Speeded Up Robust Features), the vertical edge landmarks with HOG (Histogram of Gradient) and the Haar-like feature landmarks. Those methods can play significant roles in finding appropriate visual features depending on the environment. A linear combination of those landmarks, that is, weighted feature landmarks are more suitable to find homing vector than landmarks found with one method alone. We propose that the gradient-descent method should be applied to the weighted feature landmarks to improve the homing performance. The homing results with ALV (Average Landmark Vector) model are demonstrated to show the effectiveness of the method.

가변 스텝 사이즈를 이용한 인접 투사 알고리즘 Variable Step-Size P-norm-like Affine Projection Algorithm

https://doi.org/10.5370/KIEE.2020.69.2.344

유진우(JinWoo Yoo) ; 박범용(Bum Yong Park) ; 신재욱(JaeWook Shin)

This letter presents a p-norm-like affine projection algorithm (APPA) and its variable step-size algorithm to improve the performance in high probability impulsive noise. The APPA is derived by minimizing the p-norm-like of an error vector that causes reducing error vector, when impulsive noise occurs. Therefore, the proposed algorithm has low steady-state estimation error in impulsive noise environment. In addition, its step-size algorithm is proposed by minimizing the mean-square deviation of the APPA to improve the performance in terms of the convergence speed and steady-state errors. The proposed algorithm is tested in the channel identification scenario including high probability impulsive noise. Simulation results show that the proposed algorithm has faster convergence rate and lower channel estimation errors than the variable step-size affine projection sign algorithm in impulsive noise environment.

딥러닝 기반 토마토 병충해 분류 시스템 연구 A Study of Tomato Disease Classification System Based on Deep Learning

https://doi.org/10.5370/KIEE.2020.69.2.349

함현식(Hyun-sik Ham) ; 김동현(Dong-hyun Kim) ; 채정우(Jung-woo Chae) ; 이신애(Sin-ae Lee) ; 김윤지(Yun-ji Kim) ; 조현욱(Hyun Uk Cho) ; 조현종(Hyun-chong Cho)

The early detection of plant disease is important in that it enhances the quality and productivity of crops. A large amount of research has considered machine learning classifiers to protect tomato plants from diseases, but the reliability of early disease diagnoses in this way remains uncertain due to the use of small datasets. Therefore, to enhance the dependability of them, this study examined a tomato disease classification system based on a deep learning using a dataset containing 17,063 images of tomato leaves infected with eight diseases. The deep learning model used in this classifier consisted of symmetric and asymmetric building blocks including convolutions, average pooling, max pooling, concats, dropouts, and fully connected layers. The obtained result indicated a high degree of accuracy (98.9%) which is high enough to be used as a proper diagnosis tool for farmers who lack professional knowledge of tomato diseases.

딥 러닝 기반 을 이용한 주행 환경 인지 및 격자 지도 생성 시스템 Driving Environment Perception and Grid Map Generation System Using Deep Learning Based Mono Vision

https://doi.org/10.5370/KIEE.2020.69.2.356

조은기(Eungi Cho) ; 김현석(Hyeonseok Kim) ; 박성근(Seongkeun Park)

In this paper, we propose a driving environment recognition and grid map generation system based on deep learning network using only data acquired with Mono vision. YOLO(You Only Look Once)v3 and FCN are used to recognize the driving environment, and object detection and driving area detection are performed respectively. In addition, the occupancy grid map is generated using the respective network results and vehicle movement information. The data used in this study is based on the KITTI dataset. According to the results, the proposed method uses mono vision, but can obtain distance information and has higher performance than the result of generating a grid map using a single sensor.

멀티콥터의 동역학적 기동특성 및 복합 비용함수를 고려한 경로 계획 및 분석 기법 연구 Path Planning Study Considering Multicopter Dynamics and Weighted Cost Function

https://doi.org/10.5370/KIEE.2020.69.2.362

배재휴(Jaehyu Bae) ; 이영재(Young Jae Lee) ; 성상경(Sangkyung Sung)

This paper proposes path planning of multicopter. Path planning algorithms include turning radius limitations considering the maneuver of the multicopter and collision determination with obstacles. The turning radius of the multicopter was limited by using a simulator that reflects the dynamics of the multicopter, and the collision decision was determined by the occupancy of the cluster considering the size of the aircraft. In addition, this paper proposes a cost calculation method considering energy consumption and travel distance of multicopter. The algorithm was verified by performing path planning algorithms on virtual maps and maps obtained from actual experiments.

일본 시험규격 을 이용한 태양광인버터 기술기준 성능평가 Performance Evaluation of Photovoltaic Inverter Technical Standard Using Japanese Test Standard (JET)

https://doi.org/10.5370/KIEE.2020.69.2.369

윤용호(Yong-Ho Yoon)

Since 1994, Japan has been actively promoting solar power generation as an introduction policy to secure domestic energy for measures of global warming and energy security. Japan is planning to increase the amount of photovoltaic power generation to 40 times by 30 years and accelerate the development of renewable energy by fundamentally reviewing the existing energy policy centered on nuclear power generation due to the Great East Japan Earthquake and Fukushima nuclear power plant accident. Since Fukushima, Japan has become more interested in solar energy. The PV system market has long been dominated by multinational companies such as Mitsubishi, Sanyo, and Kyocera. In order to enter Japan's photovoltaic market and supply photovoltaic inverters, it is necessary to obtain certification from the Japan Institute of Electrical Safety and Environment Research Institute (JET). JET certification is a difficult quality regulation for the protection of Japan's solar market and related companies. In this paper, through the technical analysis and test of “Grid-connected protection device test method rule for small distributed power generation system (JETGR0002)”, the purpose is that the accurate analysis of JET technical standards in the design of Japanese solar inverters by domestic companies was conducted.

다구찌기법 기반 가스밀폐형 직류릴레이 최적설계 연구 Study on the Optimal Parameter Design of Gas-insulated DC Relay Systems Based on Taguchi Method

https://doi.org/10.5370/KIEE.2020.69.2.375

이호준(Ho Jun Lee) ; 김영국(Young Kook Kim) ; 조우진(Woo Jin Jo) ; 고창섭(Chang-Seop Koh) ; 안길영(Kilyoung Ahn) ; 김영근(Young Geun Kim)

As LVDC distribution is widely applied to the industry in 21st century, DC components are used in the many applications. Among various devices, A gas-insulated DC relay is frequently used in ESS and Electric Vehicle systems. In order to develop this device for the better temperature rise and actuating performance, this paper deals with optimal design process in two core components, main contact and linear actuator, respectively. By applying Taguchi method to this system, it is capable of acquiring a set of orthogonal tables with S/N(Signal to Noise) ratio values in the electro-magnetic and heat transfer simulation environments. With respect to data from the orthogonal tables, we get the optimal sets in terms of contribution degree. Based on this methodology, we are able to select an optimized combinations for the best performance.