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

전압 프로파일 향상 및 전력 손실 최소화를 고려한 여러 종류의 분산형 전원 최적 위치 및 용량 선정에 관한 연구 Optimal Placement and Sizing of Multi-Type Distributed Generation Considering Voltage Profile Improvement and Power Loss Minimization

자르제스 핫산(S Jarjees Ul Hassan) ; 와심 하이더(Waseem Haider) ; 아리프 메디(Arif Mehdi) ; 테크 구쉬(Teke Gush) ; 송진솔(Jin-Sol Song) ; 김철환(Chul-Hwan Kim)

In recent years, the demand of electric power generation has increased significantly. Electrical distribution systems are progressively featured with multi types of Distributed Generation (DG) units to meet the sustainable energy requirements, improve voltage profile, and minimize energy losses. The aim of this work was to improve voltage profile and to reduce the power losses by optimal placing and sizing of multiple DGs, grouped in three types according to their capability in generating active and reactive powers, using iterative method. The load-flow method was used to simulate the test system i.e., IEEE-33 bus radial distribution system, using MATLAB programming. A notable improvement in voltage profile and reduction in active and reactive power losses of 69.66% and 64.14%, respectively, were achieved in comparison to the system without DGs.

주파수응답 성능 기반의 신재생발전기 계통관성 기여도 정량화 방법 A Frequency Response Performance based Quantification Method of RES Contribution on the Power System Inertia

조기룡(Gi Ryong Jo) ; 최우영(Woo Yeong Choi) ; 국경수(Kyung Soo Kook)

The high Penetration of RES could have a negative effect on the power system stability by reducing its system inertia. As one of its measures, the requirements for frequency response performance of RES has been strengthened by revising the grid code for RES in the Korean power system. In this paper, it is confirmed that the frequency response of the RES can contribute even in the system inertia, and a method for quantifying its contribution on the system inertia based on its frequency response is proposed. The effectiveness of the proposed method is verified by comparing the system inertia derived with the calculated inertia constant of RES with the system inertia derived from the simulated frequency response of the RES integrated power system. The Power Simulation Simulator for Engineering (PSS/E) which is a large-scale power system analysis program was used to model Korean power system integrated with RES for the case studies.

배전계통의 태양광 수용용량 증대를 위한 지원금 기반 프로슈머 자가소비 최적화 기법 Prosumers’ Self-consumption Optimization Scheme through Subsidy to Increase the Solar Photovoltaic Hosting Capacity in Distribution Systems

손예지(Ye-Ji Son) ; 임세헌(Se-Heon Lim) ; 윤성국(Sung-Guk Yoon)

In the power industry, renewable energy has been adopting into the power system to reduce global warming. However, renewable energy expansion such as solar photovoltaic (PV) raises a voltage stability issue for distribution systems. This work proposes a prosumers’ self-consumption optimization scheme through subsidy to increase the hosting capacity of solar PV in distribution systems. Therefore, it reduces cost and increases the utilization of solar PV. We investigate a case study using the IEEE 15 bus test model. The case study confirms that the overvoltage problem is solved by changing the prosumers’ power consumption pattern due to the subsidy. Therefore, the hosting capacity increases without system reinforcement and curtailment.

하이브리드 측정데이터를 활용한 상태추정에 관한 연구 A Study on State Estimation Using Hybrid Measurement Data

이수원(Su-Won Lee) ; 차효원(Hyo-Won Cha) ; 김병호(Byoung-Ho Kim) ; 김홍래(Hongrae Kim)

As the economy develops and power demand increases, the need for stable power system operation is also increasing. State estimation, one of the important functions of EMS(energy management system), estimates the state of the power system which is essential for reliable power system operation. State estimation has traditionally been performed using measurement data, obtained from SCADA(supervisory control acquisition system). PMU(phasor measurement unit), which appeared in the early 1990s, improved state estimation by providing more accurate synchronized data than SCADA measurement data. However, due to various problems, the PMU cannot be implemented at all buses in the power system, and for this problem, a study on a hybrid state estimation technique using both SCADA and PMU measurement data is required. This paper proposes a new technique for hybrid state estimation using SCADA and PMU measurement data. The proposed technique can improve the conventional state estimator and reduce the influence of bad data. Tests are done in the IEEE test system and the KEPCO power system.

선로정수 추정 결과 기반 상대단 전압/전류 페이저 추정을 활용한 IEC 61850 기반 변전소 간 상대 시각 오차 추정에 관한 연구 A Study on IEC 61850-Based Time Synchronization Error Estimation between Substations using Estimated Voltage / Current Phasor of Adjacent Substation considering Transmission Line Constants

김민수(Min-Soo Kim) ; 강상희(Sang-Hee Kang)

Time synchronization error between adjacent substations may cause the mal-operation on IEDs. To solve this problem, this paper assumes a situation where time synchronization error occurs between substations due to GPS errors, etc., and estimates the changing transmission line constants due to weather, and uses them to estimate the voltage/current phasor of adjacent substations. The estimated voltage/current phasor of adjacent substation are compared with the IEC 61850-based received voltage/current phasor of adjacent substation to estimate the time synchronization error between substations

배전계통의 변동성 신재생전원 수용용량 증대를 위한 BESS 제어 전략 및 실시간 모의해석 A Control Strategy of BESS and its Real-Time Simulation for increasing the Hosting Capacity of Variable Energy Resources in the Distribution System

유한님(Han Nim Yu) ; 최우영(Woo Yeong Choi) ; 국경수(Kyung Soo Kook)

This paper proposes a control strategy of Battery Energy Storage System(BESS) for increasing the hosting capacity of the Variable Energy Resources (VER) in the distribution system by resolving any violation in bus voltages and line loading caused by the connection of VER. The effectiveness of the proposed algorithm was verified by study cases employing the real distribution system based test system in terms not only of the long term time-series simulation but also of the real-time simulation

Sharing용 ESS의 누설전류 발생 메커니즘 및 모델링에 관한 연구 A Study on Mechanisms and Modeling of Leakage Current in Sharing ESS

조성덕(Sung-Duck Cho) ; 이후동(Hu-Dong Lee) ; 신건(Dong-Hyun Tae) ; 노대석(Jian Shen)

Contrary to a stationary ESS, a sharing ESS is movable and ought to be interconnected with distribution systems at many different locations, which means the reliability of safety for personnel and ESS facilities is essentially required. Especially, the leakage-current due to insulation degradation of customer facilities and load-unbalance may adversely influence batteries in sharing ESS depending on the grounding system of customers. Therefore, this paper presents mechanisms of the leakage-current occurrence by load-unbalance, insulation degradation of secondary lines and facilities, and stray-capacitance of IGBT in PCS of sharing ESS. And also, a modeling of the proposed mechanism is performed using PSCAD/EMTDC software to evaluate the characteristics of leakage-current in accordance with the causes of occurrence. As a result of the simulation with parameter analysis based on the above-mentioned modeling, it is found that the magnitude of leakage-current caused by switching operation of PCS is dependent on stray-capacitance of IGBT and is confirmed that inflow of leakage-current to batteries is occurred. Moreover, it is validated that the sharing ESS can be potentially influenced by the leakage-current inflow due to the unbalanced-load and insulation degradation at customer side, depending on the resistance ratio of cases of battery and PCS in sharing ESS.

구동 인버터 및 하프브릿지를 이용한 전기차 배터리 충전기법 Electric vehicle battery charging method using drive inverter and half-bridge

김경일(Gyeong-Il Kim) ; 황대연(Dae-Yeon Hwang) ; 구본관(Bon-Gwan Gu)

In general, on-board chargers (OBCs) are used to charge the battery of electric vehicles(EVs). However, the OBC has disadvantages such as cost and increase in weight of EVs which can make worse the driving efficiency. This paper proposes an integrated battery charging module by utilizing a three-phase inverter for driving, inductance of the motor and additional half-bridge circuit. In addition, the switching pattern of the proposed module are derived according to the output voltage during charging the battery. A current control method is proposed which can perform maximum effective power control and position control simultaneously. Finally, the proposed module and current control method are validated through simulations and experiments.

모델예측제어기법들로 제어되는 3상 AC/DC 컨버터 동작 특성 및 직류 커패시터 상태 관계 분석 연구 Investigation of Relationship between DC-link Capacitor Condition and Performance of Three-phase AC/DC Converters Controlled by Model Predictive Control Methods

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

In this paper, six model predictive control techniques developed so far to be used to operate a three-phase active rectifier are classified. In addition, their input and output electrical performance are compared and analyzed. The six model predictive control techniques are largely classified into voltage-based (VOC) and direct power control (DPC) methods. In addition, VOC and DPC are classified into a basic control method and a modified control method divided into a vector selection method and an offset voltage injection method, respectively. The electrical characteristics of the input and the output side of the three-phase active rectifier operated by these six types of model prediction control algorithms are compared. In particular, the change of characteristics according to the variation of capacitance and equivalent series resistor (ESR) of the output DC link capacitor is investigated and analyzed. As a result, it is confirmed that the performance change of the three-phase active rectifier is greater due to the increase in the ESR than the decrease in the capacitance of the output DC link capacitor. In addition, it is confirmed that in both the basic and modified algorithms, the DPC-based model predictive control algorithm shows better performance in both the input current total harmonic distortion (THD) and the output voltage fluctuation in terms of increase of ESR and reduction of capacitance of capacitor than the VOC-based model predictive control technique. In the capacitor loss, the DPC-based control techniques show higher efficiency than the VOC-based control algorithm.

기능성 금속 산화물이 코팅된 투명 히터 Functional Metal-oxide coated Silver Nanowires for Transparent Heater

서지흔(Ji-Heun Seo) ; (Malkeshkumar Patel) ; 남상은(SangEun Nam) ; 이기범(NamKibum Lee) ; 김준동(Joondong Kim)

High-performing transparent heater was achieved by using silver nanowires (AgNWs). The AgNWs were networked through spin coating method. In order to protect AgNWs from deformation according to heating operation, a functional metal oxide (ZnO) was coated over the AgNWs. To preserve the optical transparency, FTO-coated glass was adopted as the substrate. The transparent heater has a structure of ZnO/AgNWs/FTO/glass has more than 70% transmittance at the wavelength of 550 nm. The heating temperature of the transparent heater was reached over 300℃. The functional ZnO coated AgNWs transparent heater was stable for the thermal-cyclic operation, meanwhile, the bare AgNWs heater showed unstable and fluctuation in heating temperature. The stable operation of the transparent heater was demonstrated for the excellent water evaporation function, demisting and deicing performances. This high transparent heater has high potential to be applied for windows of transportation vehicles and buildings.

HVDC 케이블 접속재용 실리콘고무/나노 실리콘카바이드 콤포지트의 전기적 특성 Electrical Properties of Silicone Rubber/Nano Silicon Carbide Composites for HVDC Cable Accessories Materials

박재준(Jae-Jun Park)

In order to develop HVDC cable accessory, space charge exists at the interface between XLPE and EPDM composite or at the interface between XLPE and SiR. The larger the difference in ratio between the dielectric constant and the electrical conductivity of the two insulators, the greater the amount of space charge appears at the interface. The more and more space charges are stored at the interface, the higher the electric field distortion occurs. Therefore, in developing HVDC cable connection materials, Silicone rubber/nano silicon carbide (SiC) contents composites related to insulation and electrical conduction were manufactured. Nano SiC, a semiconducting inorganic material, has been modified to reinforce the interface of the composite mixed with silicon rubber.In addition, in order to study electrical ±HVDC dielectric breakdown characteristics and dielectric characteristics, modified nano SiC was filled with 0, 1, 3, 5, 7, 9wt%, dispersed, and nanocomposite was developed.

액상실리콘고무/나노 실리콘카바이드 복합체의 부분방전 저항성 특성 Partial Discharge Resistance Characteristics of LSR/Nano SiC Composite

박재준(Jae-Jun Park)

For the development of HVDC cable connector, Nano SiC was corroded in H2O2 to form Si-OH . On the basis of SiR, Nano SiC was chemically treated with vinylsilazane. Samples were prepared by homogeneously dispersing the modified Nano SiC in silicon according to the doping level content (0, 1, 3, 5, 7, 9 wt%). It is to develop a controllable material with nonlinear conductivity that can homogenize electrical stress in HVDC cable connectors. In addition, in order to develop a material with strong partial discharge resistance and thermal conductivity, high voltage stress was applied for 500 hours in a 5kV/720Hz environment. As a result, the erosion depth of the surface was measured. Heat conduction was measured and evaluated to investigate the effect of high voltage stress on heat conduction.

다입출력 불확실 선형 플랜트를 위한 출력 예측 성능을 갖는 제어 입력 변환 적분 슬라이딩 모드 제어 Control Input Transformed Integral SMCs with Output Prediction Performance for MIMO Uncertain Linear Plants

이정훈(Jung-Hoon Lee) ; 최명수(Myeong-Soo Choi)

In this note, the discontinuous and continuous control input transformation integral sliding mode control(SMC)s by using the integral sliding surface without the reaching phase and with the output prediction performance as the another approaches of [34] are presented for multi input multi output(MIMO) uncertain linear plants. Theoretically discontinuous and practically continuous control input transformed variable structure system(VSS)s are proposed. The integral sliding surface with no reaching phase is suggested and its ideal sliding dynamics from a given initial condition to the origin is obtained. By using the solution of the ideal sliding dynamics, the real robust output can be pre-designed, predetermined, and predicted. The transformed control input is suggested for generating the sliding mode for the entire trajectory from any given initial condition to the origin. The closed loop exponential stability together with the MIMO existence condition of the sliding mode on the predetermined sliding surface is investigated theoretically for the complete formulation of the VSS design for the output prediction performance. Another concept of the ideal sliding dynamics is given. For practical applications, a continuous approximation of the discontinuous VSS is made by means of the modified boundary layer function. In addition, the closed loop bounded stability together with the MIMO existence condition of the sliding mode by the continuous VSS is analyzed. The discontinuity of the control input as the inherent property of the VSS is much improved. Through a design example and simulation studies, the usefulness of the proposed discontinuous and continuous control input transformed VSS controller is verified. The projected ideal sliding trajectory is given

GAN을 사용한 재구성 오차 기반의 이상감지 Reconstruction Error based Anomaly Detection Defects Using GAN

최효민(Hyomin Choi) ; 서기성(Kisung Seo)

Anomaly detection is a technique used to identify unusual patterns that do not conform to expected behavior such as defects or unusual situations. Various generative adversarial network (GAN) and autoencoder based methods have been suggested and shown much progress in this field. ABC[5], an existing representative supervised anomalies detection method, generates blur images for normal data, and the distribution of reconstruction errors for normal and abnormal overlaps considerably. In order to solve these problems, we proposed an improved anomaly detection method using autoencoder and GAN. The proposed method combine various loss functions of both supervised and unsupervised anomaly detection utilizing both normal and abnormal training data. We demonstrate the proposed GAN based anomaly detection by performing experiments on Fashion-MNIST, and real-world industrial dataset ? metal surface defects. Compared to ABC[5], our model is superior to the previous approach in terms of average area under the ROC curve (AUROC) and distribution of the reconstruction errors for normal and anomaly data.

드론의 로봇팔(RAD)을 이용한 청소 로봇의 기울어진 태양광 패널위의 랜딩 실험연구 Landing Experiment of a Cleaning Robot on a Slanted Solar Panel by Using a Robot Arm for a Drone (RAD)

권동욱(Dong-Wook Kwon) ; 정슬(Seul Jung)

In this paper, the landing experiment of the Solar Panel Cleaning Robot(Dr.SPC) by a drone is presented. The robot arm for a drone (RAD) is designed to have two degrees-of-freedom to carry the cleaning mobile robot. The end-effector of the arm is equipped with an electromagnet to hold and release the robot electrically. The end-effector of the robot arm also has two ultrasonic sensors to measure the slanted angle of the panel and a camera to see the panel closely. Measuring the slanted angle of a solar panel is used for the arm to tilt the cleaning robot in parallel with the panel to minimize the contact force measured by a force sensor mounted on the first link. A drone is replaced with an x-y table for the planar motion of the arm. Actual landing experiments of Dr. SPC on the panel are conducted to test the feasibility.

PILS 시뮬레이터를 이용한 GPS 및 통신불가 미지 실내 환경에서 자율비행 탐색임무를 위한 통합성능 분석 PILS-based Performance Analysis of Drone Autonomous Flight for Exploration Mission under Unstructured Indoor Environment

김동균(Dong-gyun Kim) ; 이병진(Byoung-jin Lee) ; 성상경(Sang-Kyoung Sung)

This study presents a PILS simulator design and its performance analysis results of autonomous exploration algorithms under infrastructure outage environments such as battle field. For this, an unstructured indoor environment is considered where drone autonomously explores and returns to the starting point without GPS and other communication linkage. At the end of the mission, the map and the location of the target are transmitted to its operator. Component algorithms necessary for this include path planning, SLAM, image processing with target recognition and its realtime integration for drone’s flight control. The simulator studied in this paper primarily constitutes the flight control system of drone that participates “Autonomous Flight Competition in Battlefield” supported by the Agency for Defense Development(ADD).

광용적맥파 입사파와 반사파 지표 기반 혈관 노화 추정 모델 개발 Development of Vascular Aging Assessment Model Based on Photoplethysmogram Incident and Reflected Wave Characteristics

박준영(Junyung Park) ; 신항식(Hangsik Shin)

This study aims to develop a regression model for assessment of vascular aging based on characteristics of photoplethysmogram incident and reflected wave decomposed by Gaussian mixture model. We obtained photoplethysmogram from 757 participants and defined 16 primary and 20 combined features that were created from the morphological characteristics of incident and reflected wave in temporal and spatial domain. In correlation analysis, the features from amplitude of reflected wave and skewness of PPG had the highest correlation coefficient with subject’s real age. The vascular aging assessment models were developed by linear and non-linear regression. As a result, the 2nd order polynomial model developed with 5 features based on skewness of PPG, kurtosis of incident wave, time of incident wave’s peak, area of incident wave and amplitude of reflected wave’s peak showed 9.6 years of root mean square error, outperforming the linear model.

선형 스플라인 보간법을 활용한 교류철도 고장점표정 보정기법에 대한 고찰 A Study on the Correction Technique of Fault Location of AC Railway using Linear Spline Interpolation Method

신동혁(Dong-hyuk Shin) ; 김성철(Seong-Cheol Kim)

In this paper, we compare and analyze the characteristics of the boosting current ratio, which occurs differently depending on the ground configuration of the traction line, to derive the main causes of the fault location error. To this end, the Power system analysis program (PSCAD/EMTDC) is utilized to derive the characteristics of the boosting current ratio due to the other-line absorption phenomenon through modeling and simulation. Furthermore, to derive problems from existing calibration methods, we analyze facial expression errors by classifying single linear interpolation calibrations into multiple cases. We present a correction technique using linear spline interpolation to improve the accuracy of the fault point representation even under the nonlinear boost current ratio characteristic conditions due to integrated ground and other line absorption phenomena.

600Watt 급 LED 조명등의 열 해석 및 방열 설계 Thermal Analysis and Thermal Dissipation Design of a 600Watt Type LED Lighting

구경완(Kyoung-Wan Koo) ; 한재섭(Jae-Sup Han) ; 신부현(Buhyun Shin) ; 김영식(Youngshik Kim) ; 유봉조(Bong-Jo Ryu)

This paper deals with thermal flow analysis of LED lighting that is widely used in athletic facilities, underpass, household luminaries, etc. Recently, LED lighting is in the process of replacing the existing light sources based on the advantages of eco-friendliness, energy efficiency, high lifespan, etc. However, the heat generated from LED may lower the reliability of LED lighting by raising the temperature of chips. In this paper, it is verified that changing the form of the existing flat heatsink to a mechanically twisted structure without using a heat pipe for a 600-watt LED lighting is more effective for convectivity. Thermal analysis has been performed using a software, Solidworks-Flow Simulation 2017 version. The temperature analysis also has been performed according to the change of thickness of a heat sink at the room temperature. Through the analysis, average temperatures of the heatsink with 1.5 thickness are lower than that of the heatsink with 1.0 or 1.2 thickness.