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

배전변압기 2차측 전압/전류/역률 측정치로부터 1차측 전압을 추정하는 신경회로망 연구 A Neural Network to Estimate the Primary Voltage from Secondary Measurements in the Distribution Transformer

안재국(Jae-Guk An) ; 송진욱(Jin-Wook Song) ; 임성일(Seongil Lim)

In order to maintain voltage of distribution line within a regulated range, grid tie inverter of DG controls reactive power. Reactive power control amount is determined by the medium voltage at the primary-side of the distribution transformer, while DG measurements are done from secondary-side low voltage where it is installed. Due to the characteristics of iron core, voltage drops and unknown tap position, middle voltage cannot be calculated accurately from low voltage measurement with applying winding ratio. This paper proposes a new medium voltage estimation method using ANN(Artificial Neural Network) by learning the relationship between primary and secondary side voltages. Both side voltages of the transformer are used for label and input of the ANN respectively. Training inputs are measured by DGs, and labels are calculated by state estimator of DMS(Distribution Management System). Real-time power system simulator and DMS are used to verify the feasibility of the proposed method.

Gradient Boosting Machine과 Laplace Distribution 기반의 확률적 전력수요 예측 알고리즘 연구 Probabilistic Electricity Load Forecasting Algorithm Based on the Gradient Boosting Machine and Laplace Distribution

박세준(Sejun Park) ; 김현진(Hyunjin Kim) ; 이두희(Duehee Lee)

In this paper, we develop three probabilistic electric load forecasting approaches: two parametric approaches and one non-parametric approach. In the parametric approach, we design the probability of load forecasts as the Laplace distribution since the empirical distribution of load forecasts has a shape of Laplace distribution. We also design the probability of load forecasts as the Gaussian distribution, since it has been widely used in other studies. We compare the forecasting accuracy of two distributions. The means of distributions are estimated by using the gradient boosting machine (GBM), and the standard deviations of distributions are estimated by analyzing forecasting errors through the cross validation. In the non-parametric approach, we find the probability of load forecasts by using the quantile regression (QR). Finally, we compare the forecasting accuracy of parametric and non-parametric approaches by measuring the accuracy on the pinball loss function. A parametric approach based on the Laplace distribution and GBM is the most accurate approach.

Kernel Linear를 사용한 Bagged-Boosted STACK 지원 벡터 회귀에 기반한 지능형 태양광 전력 예측 모델 An Intelligent Photovoltaic Power Forecasting Model based on Bagged-Boosted STACK Support Vector Regression with Kernel Linear

제라르도 온도 미하(Gerardo Ondo Micha) ; 김철환(Chul-Hwan Kim)

Due to the intermittent nature of Renewable Energy Sources (RES) and complexed pattern of time series data, increasing the forecasting accuracy by conventional methods and single-learner based Machine Learning (ML) algorithms is becoming increasingly challenging. Therefore, appropriate combination of ML schemes and data processing techniques is very important to increase the prediction accuracy of RES. This paper presents an intelligent Photovoltaic (PV) forecasting model using an ensemble learner approach based on a combination of bagging, boosting, and stacking algorithms and a Support Vector Regression with Kernel Linear (SVRL) meta-learner. The proposed approach pre-processes time series data using Correlation Matrix Analysis (Corr) and Principal Component Analysis (PCA). In level 0 of the STACK model, seven hybrid models are used as base learners and their individual predictions are used as input for the SVRL meta-learner in level 1. To evaluate the performance of our model, data collected from a 350KW 3rd PV power plant in Gyeongnam, South Korea, were used for simulations, and results were compared with bagging, boosting and bagging-boosting algorithms used separately, and results show higher forecasting accuracy of the proposed algorithm.

풍속과 풍력터빈 용량을 고려한 대용량 해상풍력발전단지의 경제성 평가에 관한 연구 Economic Dispatch Between Interconnected Utilities using Consensus ADMM

김규호(Kyu-Ho Kim)

This paper presents an optimization for the economic dispatch between interconnected multi-regional utilities, which does not require any form of central coordination. A distributed algorithm based on the alternating direction method of multipliers (ADMM) is proposed in this paper. The solution of a local or regional optimization is exchanged only between neighboring areas. In the update process, the decision variables for consensus area determine the optimal solution of each area including consensus buses and calculate the average of consensus buses. The performance of the proposed consensus ADMM was compared to that of the Newton-Raphson method.

국내외 RE100 운영현황 분석 및 국내 RE100 활성화를 위한 방안 Analysis of Global RE100 Operation Status and Suggestions for Expanding RE100 in South Korea

신훈영(Hunyoung Shin) ; 박종배(Jong-Bae Park)

The RE100 (Renewable Energy 100%) campaign is a voluntary initiative at the private level to procure 100% of a company's electricity consumption with renewable energy. Although multiple companies in South Korea have announced their participation in RE100, the number of participating companies is still very limited compared to other developed countries for both regulatory and economical reasons. In this study, we analyze various renewable energy purchasing methods for participating in RE100 and demonstrate that power purchase agreements (PPAs) are the most efficient method for achieving the national renewable energy target in South Korea. Afterward we suggest the economical and regulatory prerequisites that should be prepared for the activation of PPAs

슬라이딩 윈도우 알고리즘 기반의 배전계통 토폴로지 추정에 관한 연구 A Study on the Estimation of Distribution Network Topology Based on a Sliding Window Algorithm

박종일(Jong-Il Park) ; 오세승(Sea-Seung Oh) ; 박창현(Chang-Hyun Park)

This paper presents a method for estimating distribution network topology based on a sliding window algorithm. As the grid connection of renewable energy sources increases, accurate network topology and line parameters have become very important information for precise system control and management in distribution systems. However, unlike the high-voltage system, the low-voltage distribution system has limited information on system parameters and topology. In this paper, a novel method to estimate network topology and line parameters using measurement data from smart meters such as AMI is proposed. The method determines network topology according to the change rate of the estimated line parameters for sequential data windows. The case study results demonstrate that the proposed topology estimation method outperforms existing methods based on Pearson's correlation coefficient.

P2G 기술 연계형 풍력발전 기반 독립형 마이크로그리드 최적 운영 방안 Optimal Operation of Standalone Microgrid Based on Wind Power Generation Linked to P2G Technology

손영건(Yeong-Geon Son) ; 황성욱(Sung-Wook Hwang) ; 이학주(Hak-Ju Lee) ; 김성열(Sung-Yul Kim) ; 김동섭(Dong-Sub Kim)

The purpose of this study is to optimize the operation of wind power generation-based standalone microgrid linking P2G technology. Renewable energy sources, such as wind turbine, photovoltaic, etc., use natural energy as a power source, so the system operator could not control the power of the renewable energy sources. Failure may occur and damage such as power failure may occur if the facilities of the RES that cannot be controlled output increase and the balance of power supply and demand in the power system is not matched. In this study, insufficient power is supplemented by power supply using diesel generator, and excess power is supplemented by Battery Energy Storage System (BESS) and Power-to-Gas (P2G) technologies. In particular, P2G technology using hydrogen energy is mainly dealt with, and multi-objective optimization programming that satisfies both objective functions is interpreted based on pareto-front optimization by deriving the power limit of wind power generators and system costs incurred when building and operating microgrids

배전계통에 한류기적용을 고려한 임피던스보정 알고리즘을 활용한 과전류계전기 동작 특성 분석 Analysis on Operation Characteristics of OCR Using Impedance Compensation Algorithm Considering Application of SFCL in a Power Distribution System

조유정(Yoo-Jung Cho) ; 박민기(Min-Ki Park) ; 임성훈(Sung-Hun Lim)

Recently, as the interest in renewable energy has increased and the electric power industry has developed, the distributed power generation has increased and the fault current has increased. This situation can cause the over-current which exceeds the capacity of the circuit breaker, it may lead to accidents in a power system, so it needs to replace in a larger capacity circuit breaker or to reduce the fault current. Installing a superconducting fault current limiter (SFCL) is an effective way to limit the fault current, though the trip delay of the over-current relay(OCR) occurs, also affects the protection coordination between OCRs. The correction method using the voltage component of SFCL was carried out as a previous study on this problem. However, this method is complicated because the correction factor should be changed according to the system condition. In this paper, an impedance compensation method is proposed to effectively exclude the effect of SFCL on the OCR. Unlike the correction method using the voltage component previously studied, the bus voltage was reflected, and the relay elements were calculated as impedance using this to reconstruct the characteristic equation of the OCR to decrease the influence of the SFCL. In addition, for precise correction, the impedance is divided into resistance/reactance components and compared with previous method. The results are analyzed through simulation using PSCAD/EMTDC.

ESS 예측 유지보수를 위한 리튬이온 배터리 운용 결과 실증 데이터 분석 Analysis of Empirical Data of Lithium-ion Battery for Predictive Maintenance of ESS

이예림(Ye-Rim Lee) ; 조경희(Kyeong-Hee Cho) ; 변길성(Gil-Sung Byeon) ; 김종율(Jong-Yul Kim)

ESS is expanding with the spread of renewable energy, but fire and explosion accidents may occur due to fault. Therefore, predictive maintenance technology for efficiency and safety is becoming more important. In this paper, for predictive maintenance of lithium-ion batteries, empirical data for battery were analyzed and the time of fault was predicted using the cell voltage deviation.

산간 지역 마이크로 수력 발전설비 구축 Establishment of Micro Hydropower Power Generation Facilities in Mountain Areas

이창만(Chang-Man Lee) ; 김종겸(Jong-Gyeum Kim)

Hydropower energy is well known as clean renewable energy. In particular, hydroelectric energy has a great advantage in that it has high efficiency compared to other energy sources. In addition, it is possible to obtain stable and constant output at all times due to its high operating rate. Compared to other countries, Korea has mountainous terrain and many small rivers. In these sites, it will be possible to build a power generation facility with a micro-level output rather than a high power generation output. The most important factors in determining generator output are flow and head. In order to operate the generator most efficiently, a constant flow rate must be maintained at all times, and the amount of head must be be the same. In general, small rivers in rural areas have large fluctuations in flow rate. Therefore, the selection of the water turbine is very important. In this study, a cross-flow water turbine that can easily respond to changes in flow rate selected, and a squirrel cage induction generator was applied in consideration of economic feasibility and maintenance when selecting a generator. This research team compared and analyzed the difference between design and operation through simulation and measurement of the power and power factor obtained from the induction generator when it is installed and operated in the field after determining the output considering the flow rate and the head.

분산전원용 PCS의 누설전류 등가회로 모델 및 분석 Leakage current Equivalent circuit Model and Analysis of PCS for Distributed power

서정진(Joungjin Seo) ; 차한주(Hanju Cha)

Due to continuous environmental problems around the world and an increase in energy consumption, interest in solar power, wind power, and hydropower is increasing. Among them, photovoltaics is the most used in industries and homes because it is easy to repair and can be used for a long time. In photovoltaic PCS, parasitic capacitance is generated between the photovoltaic module and the ground due to the installation structure of the photovoltaic module. This parasitic capacitance, VCM, which is a common mode voltage generated by switching of PCS, is applied to CP, and leakage current occurs. In this paper, the common mode voltage characteristics at three-phase three-level, and three-phase two-level were compared. Proposed an equivalent circuit that was equalized from unaffected by grid impedance the point of view of the common-mode by dividing it into a transformerless type PCS connected to the grid ground and a transformer type PCS applying a transformer. The validity of the proposed equivalent circuit was verified by constructing a three-phase three-level PCS and comparing the equivalent circuit using the experiment measurements and PSIM. In the transformerless PCS, the leakage current is equivalent to 1.13A in the equivalent circuit and 1.14A in the experiment. In the transformer type PCS, the equivalent circuit is 68mA and the experiment 70mA. In addition, for the validity of the proposed equivalent circuit, FFT analysis of leakage current, which is the switching frequency, was performed.

전계불평등도에 따른 대기압 공기 절연파괴특성 분석 Analysis on Electrical Breakdown Characteristics of Atmospheric Air according to the Electric Field Non-uniformity

김건(Geon Kim) ; 김진태(Jin-Tae Kim) ; 노홍석(Hongsuk Noh) ; 윤경록(Kyungrok Yun) ; 김세현(Sehyun Kim) ; 석복렬(Bok-Yeol Seok)

In this study, electrical breakdown characteristics of atmospheric air under the AC and lightning Impulse(LI) voltage waveforms were investigated to settle the electrical insulation design criteria for air insulated switchgear. To investigate the electrical breakdown characteristics according to the non-uniformity of electric field, needle-plane and 4 kinds of sphere-plane electrodes were used as the tested electrode system. Through the experimental results, it was found that when positive impulse voltage is applied, it can be the weakest in terms of electrical insulation. As for the positive LI breakdown voltage, in the case of electrodes with high non-uniformity such as needle-plane electrode, it was confirmed that electrical breakdown voltage increased almost linearly with the gap length. Based on the experimental and electric field analysis results, it is found that it is desirable to establish the air insulation design/evaluation criteria as a function according to the distance in electrodes with high non-uniform electrode systems, and as a maximum electric field function in the quasi electrode systems. Moreover, maximum electric field for partial discharge (PD) inception decreased as the cross-sectional area of the electrodes facing each other increased.

AMI 2.0 기반의 IoT Gateway 연구 The Study on IoT Smart Meter Gateway Based on AMI2.0 System

최강운(Kang-Un Choi) ; 박병석(Byeongseok Park) ; 김동섭(Dongsub Kim)

AMI is a large-scale IoT system that provides various customer services such as demand response and load analysis service by collecting and analyzing customers' electricity consumption in semi-real time using bidirectional communication. Since the existing AMI system used a non-standard private protocol, standardization of the data model and transmission method is required. In this paper, the data model and transmission method based on the LwM2M IoT protocol were designed to be suitable for the AMI system. In addition, a prototype was developed and the performance and stability were tested in the field. As a result of the field test, it was confirmed that the timely data collection rate of more that 99% was achieved, and the collection time of AMI information was greatly reduced by more that 95% compared to the existing one. Therefore, it is considered that it can be used for future distribution system prediction and demand management service.

전단 융합 기반 멀티모달 심층학습을 이용한 손동작 분류 Hand Gesture Classification Using Early Fusion Based Multimodal Deep Learning

김익진(Ik-Jin Kim) ; 김수열(Su-Yeol Kim) ; 이용찬(Yong-Chan Lee) ; 이연정(Yun-Jung Lee)

In this paper, we propose a new hand gesture classification strategy using early fusion based multimodal deep learning. The structure and parameters of the state-of-the-art deep learning models such as ResNet152, DenseNet201, EfficientNetB0 for the source task of image classification are reused in the target task of hand gesture classification using surface electromyograph(EMG) and finger's kinematic data. The time-domain EMG and kinematic signals are normalized and then transformed into combined 2-D images for the early-fusion network. The experimental results support the superiority of the proposed method in terms of classification accuracy. The transfer learning model with the EfficientNetB0 shows the 93.94% accuracy for 40 gestures of 40 participants in the Ninapro DB2.

축소 차수 모델 기반 제어기와 결합한 PI 관측기 기반 제어 시스템의 안정성 해석 Stability Analysis on a PI Observer-Based Control System Combined with a Reduced-Order Model-Based Controller

손영익(Young Ik Son) ; 아마레 네비옐레울 다니엘(Nebiyeleul Daniel Amare)

System model order reduction is a popular technique employed by control systems engineers due to its ability to reduce model complexity. However, control systems designed based on reduced-order model may cause closed-loop system instability when applied to the full-order model. In addition, conventional control system improvement methods such as increasing the controller gains or using robust control techniques in particular disturbance observers can further deteriorate system performance. In order to shade light on this phenomena, this paper presents an analytical study of the effects of high observer gain on the stability of observer compensated control systems whereby both the controller and the observer are designed using the reduced-order system model. The analysis is performed by carrying out stability analysis of the closed-loop system through root locus method and Routh-Hurwitz stability criterion. The paper also presents a comparative analysis between placing all the closed-loop poles of the controller at a single location or multiple locations using LQR technique for the aforementioned class of controller. The results obtained from the analysis have been validated through a DC motor position control system application.

철도차량 속도구간별 가감속 특성의 객체지향 모델링 기법 Object-oriented Modeling Technique of Acceleration/Deceleration Characteristics of Railway Vehicles by Speed Section

박종영(Jong-young Park) ; 이한민(Hanmin Lee) ; 김정태(Jungtai Kim)

Railway vehicles have different traction and braking forces depending on their speed, which can be divided into constant torque areas, constant power areas and characteristic areas. The 4th order Runge-Kuta method was applied as a method for simulating these characteristics, and object model for railway vehicle was constructed using the overloading function of the function. The characteristics of the vehicle were calculated and compared with the actual values by applying the constructed model. We also calculated TPS (Train Performance Simulation) from the actual railway rail data and confirmed that it was similar to the characteristics of the actual railway vehicle.

전류 위상각 차이를 이용한 교류 전기철도 급전계통의 급전선 지락 고장 유형 판별법 A Discrimination Method of Ground Fault on Feeding Line using Current Phase Difference for AC Electrical Railway System

이지혜(Jihye Lee) ; 민명환(Myung) ; 안태풍(Hwan Min) ; 이병곤(Tae)

When a fault generates on AT feeding line of AC electrical railway system, train operation service would be stopped on about 10km feeding line section at both ends of Auto-transformer. When a fault generates on AT feeding line of AC electrical railway system, train operation service would be stopped on about 10km feeding line section at both ends of Auto-transformer. To obtain varied information is important to take a action for a rapid restoration of AT feeding line. In this paper, it presents how to distinct type of ground fault using measured fault current based that angle of TF and AF current are almost in-phase in case of TF-R ground fault and almost antiphase in case of AF-R ground fault. The distinction method is verified on PSCAD/EMTDC simulation and real field of AT feeding line.

인화성 분위기에서 인체대전으로 인한 정전 스파크방전 위험성 Static Spark Discharge Risk Caused of Human Body Voltage in Flammable Atmosphere

김해술(Hae-Sul Kim) ; 송형준(Hyoung-Jun Song)

The fire and explosion caused by electrostatic discharge have been repeatedly reported at the working sites with flammable materials. Despite the risk of electrostatic discharge, the relationship between human body voltage and surrounding conditions has not been intensively studied in the actual manufacturing sites. Here, we systematically studied the human body voltage and energy from electrostatic discharge under the various human body resistance to ground and relative humidity. The results show that anti-static systems, conductive shoes, mat, and wrist strip, effectively decrease human body voltage below possible explosive zone (< 300 V), while the worker without any anti-static system might cause fire and explosion. Moreover, it is required to control the humidity level at working sites to reduce the risk. Finally, we suggest an entrance control system connected with the human body resistance measurement system to avoid electrostatic discharge accidents. We believe that the result shown here will contribute to realizing safe working sites.

전기화재 원인분석을 위한 실험실 데이터를 활용한 1차, 2차 단락흔 및 열흔 판별용 CNN 알고리즘 설계 A CNN Algorithm suitable for the Classification of Primary and Secondary Arc-bead and Molten mark using Laboratory Data for Cause Analysis of Electric Fires

조장훈(Jang-Hoon Jo) ; 방준호(Junho Bang) ; 유정훈(Jung-Hoon Yoo) ; 선로빈(Robin Sun) ; 홍성준(Seong-Jun Hong) ; 방선배(Sun-Bea Bang)

In this paper, a new CNN algorithm is proposed to determine the direct cause of electric fires. We create 10,000-15,000 three types of data that can occur at a fire scene in our laboratory, and then train and verify it through the proposed CNN algorithm. As a result of the experiment and analysis, the classification accuracy of the primary and secondary arc beads was 86.2%, the accuracy of arc beads and molten marks was 93.6%. And also, the classification accuracy of the primary and secondary arc beads and molten marks was 92.4%. The results of this study are meaningful in that fire forensics can provide accurate identification results in a shorter time through artificial intelligence algorithms compared to the existing methods of identification through visual classification and physicochemical material analysis methods. In particular, the classification between primary and secondary arc beads is known to be a very difficult problem. However, the results of this study provided more than 86% classification ability

22.9kV 유입변압기 절연지 열화생성물 분석을 통한 사용연수 상관관계 분석 The Correlation Evaluation through Furan Analysis of Life-time for 22.9kV Oil-immersed Transformer

김영석(Young-Seok Kim) ; 황민(Min Hwang) ; 조기룡(Gi-Ryong Jo)

To prevent accidents through maintenance and appropriate replacement of oil-immersed transformer, the correlation between the life-time of the transformer was estimated by comparing the furan analysis of the insulation paper according to the accelerated deterioration and the insulating oil. According to accelerated deterioration, the furan value of DDP was reduced to about 1/1000 compared to that of Kraft paper, and it was shown that the thermal properties were excellent by the epoxy coating. As a result of the analysis of the degree of polymerization of the insulating paper, when the furan value was about 200 ppb, it was determined that the paper performance was lowered. Although the number of transformers collected is small, the life-time of the oil-immersed transformer is about 37 years.

ESS용 Tubular 배터리 적용을 위한 고성능 폴리에스테르 분리막의 개발 Development of High-performance Polyester Separator for Application of Tubular Batteries for ESS

서훈(Hoon Seo) ; 서인석(IN-Seok Seo) ; 구경완(Kyung-Wan Koo)

Among the different energy storage systems, the following properties are made lead-acid battery as a promising and viable ESS. Low cost energy storage system, maintenance free battery system, available in all shapes and sizes, long cycle life, larger environmental advantages, higher recycling (~99% of lead can be reused). A conventional separator for lead-acid battery enabling the LAB to reliably have a predetermined capacity after the initial charging and a prolonged service life by limiting the quantity of reducing substance liberated or produced from the separator. Overcome the issues of conventional separator by modifying the surface properties through low cost and highly efficient materials specifically inexpensive biocellulose. This research and the results confirmed that the combined BC and PE separator will be a promising candidate for LAB systems.