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

마이크로그리드를 고려한 배전계통의 복원력 향상효과 분석에 관한 연구 A Study on the Analysis of Resilience Enhancement for the Distribution System using Microgrids

https://doi.org/10.5370/KIEE.2021.70.6.843

손은태(Eun-Tae Son) ; 배인수(In-Su Bae) ; 김성열(Sung-Yul Kim) ; 김욱원(Wook-Won Kim) ; 김동민(Dong-Min Kim)

In order to elaborate analysis of resilience enhancement for distribution system considering microgrids, this paper reviews quantification methods, and measurement criteria. Through this, it was confirmed that the resilience evaluation of the distribution system needs to be performed using not only capability but also number of serviced customers and critical customers. Therefore, this paper proposes the indices for evaluating the recovery quantity, degree, and velocity of system resilience based on the concept reviewed above, and verifies their usefulness. The calculation results of the proposed indices demonstrated that the effect of the distribution system for different fault situations and the resilience enhancement effect of the distribution system through microgrids could be provided quantitatively. Moreover, the proposed indices can be used to analyze the distribution system having mutually different structures as the results are calculated through a unified evaluation standard

고침투율의 분산전원이 배전계통 보호 시스템에 미치는 영향을 고려한 과전류 계전기 정정값 최적화에 관한 연구 A Study on the Optimization Over-current Relay Setting Value Considering the Effect of a High Penetration Rate of Distributed Generation on Distribution Protection System

https://doi.org/10.5370/KIEE.2021.70.6.852

오형진(Hyung-Jin Oh) ; 김지수(Ji-Soo Kim) ; 강민재(Min-Jae Kang) ; 이 마데 두위 달만타라(I Made Dwi Darmantara) ; 김철환(Chul-Hwan Kim)

Recently, the research on hosting capacity (HC) calculation has become important due to the high interconnection of Renewable Energy Sources (RESs). The existing research on the maximum HC calculation is mainly focused on power quality. However, if the distributed generation is connected based on the HC calculation, there is a risk that the protection system could be affected and create some problems such as Sympathetic Tripping and Protection Blinding (protection device malfunction). Although this problem can be overcome by changing the relay correction value, the problems might still occur due to the limitation of the protection device setting. Therefore to solve this problem, an algorithm that can simultaneously optimize the Time Dial Setting of the overcurrent relay and the HC of the distributed generation without causing a protection system problem is proposed in this paper. The proposed algorithm was optimized through the most widely used genetic algorithm (GA), and the simulation was done using MATLAB and DigSLINET PowerFactory. The simulation was tested in IEE 37 bus system and from the simulation, the optimal overcurrent relay setting and HC value are obtained.

배전계통 토폴로지 변화에 따른 최적 방향성 과전류 계전기 정정방법에 관한 연구 A Study on the Optimal Setting Method for Directional Over-current Relay according to Distribution System Topology Change

https://doi.org/10.5370/KIEE.2021.70.6.860

송진솔(Jin-Sol Song) ; 김지수(Ji-Soo Kim) ; 신광수(Gwang-Su Shin) ; 김호영(Ho-young Kim) ; 김철환(Chul-Hwan Kim)

In modern power systems, there is a possibility that the power system topology may change due to the trip of power lines or distributed generations due to maintenance or fault. Since changes in the topology of the power system affect the magnitude and flow of the fault current, the optimally calculated setting values with the original topology may not provide the correct protection coordination. Therefore, protection method considering the change of topology is required, and in this paper, three protection methods, Protection method with fixed setting values, Adaptive protection method, Protection method with clustering, are introduced. At last, three protection methods are compared with 30 Directional OverCurrent Relays (DOCRs) in IEEE 30 bus test system.

고조파 및 불평형 성분을 가지는 계통 환경에 따른 3상 펄스폭변조정류기 성능 비교 연구 Comparative Study of Grid Conditions on Three-phase PWM Rectifier Performance

https://doi.org/10.5370/KIEE.2021.70.6.867

김동연(Dongyeon Kim) ; 김재창(Jae-Chang Kim) ; 곽상신(Sangshin Kwak)

In this paper, the input and output performance of a three-phase pulse width modulation (PWM) rectifier operated by each of three different control techniques based on current control and power control in the grid with harmonics and unbalanced components are compared and analyzed. Regardless of the basic and high-efficiency types, the same current-controlled and power-controlled techniques showed similar performance in the harmonics and unbalanced grid conditions. In all grid conditions with harmonics and unbalanced components, the output voltage by the power-controlled rectifier has a lower ripple value than the output voltage by the current-controlled rectifier. Therefore, in terms of output voltage ripple, it is confirmed that the power-controlled rectifier shows more robust characteristics in harmonics and unbalanced grid condition.

직렬 통신 기능을 이용한 대용량 계통연계형 인버터의 순환전류 저감방법 Circulating current suppression method of grid-connected inverters in parallel using serial communication

https://doi.org/10.5370/KIEE.2021.70.6.878

전세봉(Se-Bong Jeon) ; 조성준(Sung-Joon Cho) ; 이교범(Kyo-Beum Lee)

This paper proposes a circulating current suppression method of grid-connected inverters in parallel inverters using serial communication. The grid-connected inverter for large scale photovoltaic generation system consists of multiple modules in parallel based in unit inverter module. The existing method to synchronize PWM signals between inverter modules was implemented by CAN communication with high interrupt priority. However, the high priority of CAN communication can cause deterioration in current control performance due to limited resource of controller. This paper introduces an improved synchronization method of PWM signals with low interrupt priority using time stamp function. The effectiveness of the proposed method is verified by experimental results with 250kW inverter system

고효율 Perovskite/Si 탠덤형 태양전지 적용을 위한 In2O3:ZnO 투명전도박막 The transparent conductive thin films of In2O3:ZnO for application of high efficiency Perovskite/Sitandem solarcell

https://doi.org/10.5370/KIEE.2021.70.6.887

박소민(Somin Park) ; 김홍래(Hongrae Kim) ; 박형기(Hyeonggi Park) ; 김영국(Youngkuk Kim) ; 이준신(Junsin Yi)

Indium-based transparent conductive thin films are used in various opto-electric devices. In particular, the In2O3:ZnO (IZO) thin film exhibits a high electrical conductivity and high transmittance despite deposition at a low temperature of less than 100℃. IZO thin film has the advantage of being free from damage caused by heat even compared to the existing ITO thin film. In this study, we investigated the requirements for use of TCO films in silicon-based solar cells and the best alternative TCO materials to improve their efficiency. Moreover, we discussed the current status of high-efficiency solar cells using low-temperature TCO films

QoS 레벨 3: 사물인터넷에서 MQTT 프로토콜의 동기식 통신 메카니즘 QoS Level 3: A Synchronous Communication Mechanism in MQTT Protocol for IoT

https://doi.org/10.5370/KIEE.2021.70.6.893

임예린(YeRin Im) ; 임민규(Mingyu Lim)

In this paper, we propose a new Quality of Service(QoS) Level 3 mechanism of Message Queuing Telemetry Transport(MQTT). It ensures synchronous communication between a publisher and subscribers. In QoS3, a publisher can check message reception of subscribers, while traditional QoS Levels can only check reception between the publisher and the broker asynchronously. After sending a QoS3 message, the publisher waits until it receives a predetermined number of response messages. We evaluated the performance of QoS3 through delay and packet size measurements in various situations. QoS3 was slower than QoS2 because of synchronous communication. However, if interaction with lots of receivers is required, QoS3 was faster than QoS2. For the packet size, QoS3 was bigger than QoS2 because of the additional fields, but the difference was not significant. QoS3 can be effectively used in cases when the publisher needs to perform the following tasks after verifying message reception of subscribers.

스마트폰 연동 손톱 모세혈관 영상분석 시스템 개발 Development of Image Analysis System for Nailfold Capillaries Using Smartphone

https://doi.org/10.5370/KIEE.2021.70.6.905

배서연(SeoYeon Bae) ; 이언석(Onseok Lee)

The condition of the capillaries is directly affected by inflammatory cells in the disease, resulting in abnormal changes in the occurrence of the disease. Capillary observations can identify not only the current condition of the disease but also the expected diseases, which is of great importance. Existing nail capillary examinations are difficult to obtain optimal images by light reflection by oil and are being conducted by the examiner’s supervision, so there are difficulties in objective diagnosis. Also, it is difficult for busy modern people to visit the hospital because they need expensive equipment. Thus, this study developed an imaging algorithm that produces observational devices that can be simply mounted and used in mobile devices and automatically divides capillaries from the background. This study allows users to obtain images without being constrained by space and to observe capillary conditions quickly through objective and intuitive data.

마이크로그리드 보호에 대한 이슈 및 지능형 보호방법 hallenging Issues and Intelligent Protective Methods for Microgrid Protection

https://doi.org/10.5370/KIEE.2021.70.6.911

김지수(Ji-Soo Kim) ; 송진솔(Jin-Sol Song) ; 신광수(Gwang-Su Shin) ; 김호영(Ho-Young Kim) ; 김철환(Chul-Hwan Kim)

The MicroGrid (MG) is a power system that connects and utilizes renewable energy sources, energy storage systems, and electric vehicles. However, unlike the existing power system, since various power sources are connected to the MG consequently; the MG cannot be protected by the existing protective system. In other words, there exist new protection-related issues in MG. In this paper, we reviewed these issues and also confirmed the effectiveness of existing protective method utilize machine learning; these are is called an intelligent protective methods and have recently been spotlighted. Finally, a comparative analysis was performed between different protective methods using machine learning

스위치드 릴럭턴스 전동기의 Δ결선, Y결선에 따른 구동 특성 Driving Characteristics according to Δ-Connection and Y-Connection of a Switched Reluctance Motor

https://doi.org/10.5370/KIEE.2021.70.6.918

정성인(Sung-In Jeong)

A general SRM driving converter uses an asymmetric bridge converter with a structure in which a winding is placed between the upper and lower switches to excite one by one. The asymmetric bridge converter has a structure having two switches and two freewheeling diodes, so it has high efficiency and can control various types, and the current control of each phase is independent, so it is possible to overlap the current of two phases. In addition, even when a fault occurs in one phase, there is no significant effect on the other phase, and the control performance is excellent, such as a relatively low rated voltage of the device. On the other hand, the number of elements is relatively large, the drive circuit is complicated, and it is impossible to modularize the switching element. Therefore, the size of the heat sink for the switching element and the freewheeling diode increases, and thus the production cost increases. It is possible to simplify the AC motor drive system by using IPM(Intelligent Power Module) modularized with six switching elements as a connection structure between AC motors such as induction motors and synchronous motors and generalpurpose inverters with upper and lower switches. Therefore, there is an advantage of being able to reduce the size and structure of a simplified circuit compared to an SRM driving system using an asymmetric bridge converter. In this paper, considering these contents, to apply the general-purpose inverter used in AC motors instead of the asymmetric bridge converter used in generalpurpose SRM driving converters, we will examine the driving characteristics according to the Δ-connection and Y-connection of the SRM connection structure. In addition, we will study the switching control method to apply the universal inverter of AC motor according to the Δ-connection and Y-connection.

초전도 소자에 의한 DC 차단기의 동작 특성 Operating Characteristics of the DC Circuit Breaker by a Superconducting Element

https://doi.org/10.5370/KIEE.2021.70.6.924

박상용(Sang-Yong Park) ; 최효상(Hyo-Sang Choi)

Superconducting current limiting impedance selection method according to the DC circuit breaker operation characteristics for economic gain with the HVDC hybrid type superconducting DC circuit breaker is attracting attention globally. Due to the development and expansion of renewable energy sources and the development of power semiconductors, HVDC has the advantages of high system transmission efficiency and asynchronous connection. HVDC is currently being developed and commercialized as a pole-to-pole system. As the development of MVDC, LVDC and HVDC progresses, DC grid systems capable of exchanging DC power with each other will be built. A circuit breaker that can increase the reliability of the DC system operation should therefore be developed. HVDC, hybrid, semiconductor and reverse-current-type circuit breakers have been studied as potential circuit breaker options, with many papers being published to demonstrate their respective performances. In this paper, a hybrid superconducting DC circuit breaker was proposed. It consists of a superconducting fault current limiter, a mechanical cut-off contact, an LC circuit and a SA(SA). The rapid rise of the fault current was limited by using the impedance of the superconductor, while the fault current was interrupted by the cut-off operation of the mechanical DC circuit breaker. If the superconducting element shows higher fault current than the breaking capacity level of the DC circuit breaker and the burden on the superconductor will increase. Therefore, efforts were made to confirm the appropriate cut-off capacity level of the DC circuit breaker and the current limiting impedance of the superconductor through experiments. As a result, we proved that the current limiting impedance of the superconductor could be analyzed based on the tripping operation of the DC circuit breaker.

DC 차단기의 차단 시간 단축을 위한 초전도 선재 유형에 따른 차단 특성 분석 Analysis of blocking characteristics for each type of superconducting wire to reduce the breaking time of DC circuit breakers

https://doi.org/10.5370/KIEE.2021.70.6.930

구희석(Hui-Seok Gu) ; 박상용(Sang-Yong Park) ; 최혜원(Hye-Won Choi) ; 최효상(Hyo-Sang Choi)

DC cutoff must be completed within a few ms. Therefore, this paper derives the optimal superconducting wire winding method for efficient current limiting and fast execution of the blocking operation. First, the electromagnetic field characteristics of the superconducting wire according to the winding type were analyzed using the Maxwell program. After that, the EMTDC/PSCAD program was used to analyze the DC blocking performance according to the winding type. Based on the simulation results, as a result of the DC cut-off experiment for each winding type, the spiral type superconductor has a higher resistance rise curve than the helical type, so it is possible to limit the current efficiently by up to 4.01%. In addition, as the magnetic field characteristics are high, the quench of the superconductor operates quickly and the operation time of the circuit breaker is shortened by 0.19 ms, so it can be confirmed that the blocking completion time is also reduced by 0.25 ms.

LVDC 2선식 전원계통의 고저항 중간점 접지방식 특성 분석 An Analysis on Characteristics of High Resistance Impedance Mid-Point Grounding Method for the 2-Wire LVDC Power System

https://doi.org/10.5370/KIEE.2021.70.6.936

임대식(Dae-Sik Lim) ; 이기연(Ki-Yeon Lee) ; 김동우(Dong-Woo Kim) ; 채동주(Dong-Ju Chae) ; 임승택(Seung-Taek Lim) ; 문재현(Jae-Hyeon Mun)

It is very important to prevent electrical accident, especially the electric shock when it comes to LVDC system as it is widely used in public. Commonly, the mid-point grounding is used in voltage above 200 V (Line-to-Ground) in some countries like USA and Japan. In IEC regulation 60364, there are many theories of grounding in AC and DC system with their own special use. Also, grounding in DC system can be varied as there can be many combination of grounding points including positive/negative electrodes, mid-point wire and mid-point grounding. The purpose of this study is to analyze characteristics of advanced grounding in residence DC system in view of grounding and protection through reviewing the standard IT grounding system, body-current-paths of high-resistance mid-point grounding and impact from electrolytic corrosion of earth electrodes.

타일 격자무늬 추적 자율주행 로봇을 위한 위치 인식과 주행 제어 Position recognition and driving control for an autonomous mobile robot that tracks tile grid pattern

https://doi.org/10.5370/KIEE.2021.70.6.945

김정주(Jung-Ju Kim) ; 김동진(Dong-Jin Kim) ; 구경완(Kyung-Wan Koo)

Human visual intelligence refers to the ability to use the visual environment to suit one's own survival. Humans can use visual intelligence to find a target location using only visual perception information in an unknown indoor space. In this paper, we propose a method for the robot to recognize the location and determine the driving direction using the grid pattern information of tiles installed on the floor of an indoor space by imitating human visual intelligence