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

재난으로부터의 계통 복구력 개념과 COVID-19 재난에서 7개국의 확진자수 복구력 특성 분석 System Resilience Concept Against the Disaster and Resilience Characteristics of Seven Countries for the COVID-19 Disaster

박주창(Joochang Park) ; 오웅진(Ungjin Oh) ; 이연찬(Yeonchan Lee) ; 정세민(Semin Jeong) ; 최재석(Jaeseok Choi)

In general, resiliency of the power system can be defined as “the ability of the power system to quickly return to its original state from external shocks, such as natural disasters characterized by great influence and low probability of occurrence.” Data is needed to study resiliency of the power system. However, even though the probability of an accident such as the Chernobyl nuclear accident and the Fukushima nuclear accident is extremely low, it is difficult to establish a database of actual accidents that once occurred accidents can bring a crisis to the survival of mankind. System resiliency, therefore, is very hot issue in recent. This paper develops new function and models in order to identify characteristics of the resiliency for COVID-19 confirmer data for seven countries.

RANSAC과 순환최소자승 알고리즘을 이용한 고조파 등가 모델 파라미터 추정 연구 A Study on the Parameter Estimation of Harmonic Equivalent Model Using the RANSAC and Recursive Least Square Algorithms

박종일(Jong-Il Park) ; 박창현(Chang-Hyun Park)

This paper presents a method for estimating the parameters of a harmonic equivalent model based on the RANSAC(random sample consensus) and RLS(recursive least square) algorithms. The harmonic contribution assessment basically requires the equivalent models of harmonic sources. This model consists of an equivalent impedance and an equivalent voltage source. Because the equivalent model parameters can not be measured directly, it is necessary to estimate the parameters of harmonic sources by measuring PCC voltage and current. In previous studies, several RLS-based methods have been proposed to obtain the equivalent parameters. However, if the measured data contains outliers, the methods lead to large errors in parameter estimation. Outlier is a data point that differs significantly from other measured data due to various causes such as measurement errors. In this paper, we propose a RANSAC based method to remove outlier from measured data set to improve parameter estimation performance. To verify the performance of the proposed method, a comparative analysis for the case of including data outlier, with the previous methods was performed

스마트 아크제거기 개발을 위한 개념 설계 및 실험적 입증에 대한 연구 A Study on the Conceptual Design and Verification for Development of Smart Arc Eliminator

김정훈(Jung-Hoon Kim) ; 김정배(Jung-Bae Kim) ; 윤순일(Soon-Il Yoon)

With safety being emphasized around the world, attempts are being made to eliminate arc-induced electrical accidents as they are the most proportion in existing electrical systems. As a result of reviewing the recent problems with arc elimination technology, it is necessary to develop a smart arc eliminator equipped with technology that can be selected depending on the size of over-current, and the reclose of available multiple times of the arc elimination while maintaining the high speed. In this paper, to propose the following conceptual design for smart arc eliminator that needs to be developed newly. The operating equipment part using Thomson coil was a conceptual design with developed in a cylindrical form for small-sized lightweights by the FEM program. The bumps structure in the operating contacts and the fixed contacts adopt the canted coil spring, etc. so that they can be endurance 20 times or more. The judgement part is embodied concept of malfunction prevention and large current sorting, and the subsequent Thompson coil actuator and return part to normal were designed with proper properties. Through this proposed conceptual design, developed to demonstrate the standards and design requirements of IEC, etc. by Official approval of the KOLAS Testing Institute. Also Smart arc eliminator were applied to the field to show effectiveness through case study results.

IEC Electropedia 등재용 IEV 한국어 용어 정의를 위한 작업 시스템에 대한 연구 The Study on Working System for Definitions of IEV Korean Terms for Registration in IEC Electropedia

황유모(Humor Hwang) ; 김정훈(Jung-Hoon Kim) ; 손수국(Su-Goog Shon)

We proposed a definition DB of terms, term standardization procedures work templates and contents for implemantation of Korean Electropedia for registering IEV 21,222 definitions of Korean terms in Electropedia (IEV Online System) and demonstrated their effectiveness through case studies. It aims to be the first in the list of definition services of terms by languages other than English and French, currently available in Electropedia. Implementing the 2018 IEC TC 1 decision is a continuation of the 20,000 Korean terms projects listed in the 2018 IEC Electropedia. Definition development and registration are prepared in each language in major countries such as Korea and Germany. However, there is no standard procedure for registration, and there is no choice but to take different forms according to the circumstances of each country

기온민감도 및 BTM의 추정을 반영한 특수일의 전력수요예측 알고리즘 Load Forecasting Algorithm for Special Days by Considering Temperature Sensitivity and BTM Estimation

권보성(Bo-Sung Kwon) ; 배동진(Dong-Jin Bae) ; 문찬호(Chan-Ho Moon) ; 송경빈(Kyung-Bin Song)

The load on the special days are relatively lower compared to load on normal days, the pattern of load is irregular, and the number of load data for the past similar days to the special day is limited. Since the load forecast error on special days is relatively large compared to the load forecast error on normal days, the improvement of load forecasting algorithm for special days is needed. An hourly load forecast algorithm for special days that can reflect the effect of temperature varying over time and the effect of BTM(Behind-the-Meter) solar photovoltaic(PV) generators increasing by year is developed to improve the load forecasting accuracy for special days. The proposed algorithm forecasts hourly load for special days using fuzzy linear regression, and then corrects the forecast load using both the temperature sensitivity and the estimated BTM solar PV generation. The forecast accuracy is improved when using the proposed algorithm to forecast the load on special days in 2019.

원자로 냉각펌프 전동기용 VCB 스위칭 서지 해석과 써지흡수기 고장으로 인한 전동기 트립 방지대책 Switching Surge Simulation of VCB for Reactor Coolant Pump Motor and Coping with Motor Trip by Surge Arrester Failure

토마스 쥬마 칼렌가(Thomas Tsuma Kalenga) ; 장중구(Choong-koo Chang)

Several failures of the surge arresters in nuclear plants during normal power operation caused ground fault relay (GFR) to trip and shut down the reactor coolant pump (RCP). Furthermore, several false trips of the GFR were reported between 2004 and 2018. This was assumed to have been caused by vacuum circuit breaker (VCB) switching surges. This paper sought to establish the expected switching surges in this network, how safe it is to operate the reactor coolant pump motor (RCPM) without a surge arrester (SA), establish the cause of the false operation of the ground fault relay, and ways to mitigate against it. It turns out that the VCB switching surges are within the RCPM insulation rating. The GFR activation was not caused by the residual current I0 created by the VCB switching surges. The SA should be removed from the circuit until a SA monitoring scheme is put in place.

P2G 기반 마이크로그리드의 경제성 분석 및 보급 방안에 관한 연구 A Study on the Economic Analysis and the Diffusion Strategy of P2G-based Microgrid

황성욱(Sung-Wook Hwang) ; 이학주(Hak-Ju Lee) ; 김정훈(Jung-Hoon Kim)

Recently, global interest in the hydrogen economy is increasing, and most advanced countries, as well as Korea, have established and implemented various policies to foster the hydrogen industry. Hydrogen is considered as an energy carrier that is able to integrate and control existing energy such as electricity, gas, and heat in one dimension, and theoretically, its possibility has already been confirmed. As the first step to implement this, advanced countries such as Switzerland and Germany are leading the development of Powr-to-Gas (P2G) technology. In Korea, some energy-related organizations are conducting various researches recently, and KEPCO (Korea Electric Power Corporation) began research to connect the P2G-based microgrid to the distribution grid in 2019. Currently, the design and construction of the demonstration site is in progress. In this paper, the economic feasibility of a P2G-based microgrid is analyzed and an appropriate direction of penetration is proposed considering the increase of hydrogen load. For the economic analysis, HOMER Pro, which is widely used worldwide for evaluating the economics of renewable energy and microgrids, is used and Bass' diffusion model is applied to predict the increase of hydrogen load. In the case study, the economic analysis is carried out to derive the optimal facility configuration for 10% of the total load of the Ulsan techno-industrial complex under construction of the P2G-based microgrid demonstration site. As well as the sensitivity according to the level of hydrogen load is evaluated for the purpose of utilization of unused energy caused by renewable energy.

첨두부하 및 자원의 불확실성을 고려한 마이크로그리드 적정 규모 산정에 관한 연구 A Study on the Appropriate Resource Configuration for Microgrid Considering Peak Curtailment and the Uncertainty of Energy Resources

김정훈(Jung-Hoon Kim) ; 이유석(Yu-Seok Lee) ; 이학주(Hak-Ju Lee) ; 황성욱(Sung-Wook Hwang)

In this paper, a simple relational expression is established through an impact assessment after extracting the uncertainty of new and renewable energy resources and the probabilistic characteristics of the demand-side resource and inputting a random variable using the moment method into the HOMER program to obtain the expected appropriate size and range. In the case where there is not enough supplier resource investment and there is no necessity to supply power to the peak load, the concept of a virtual generator that considers the reduction of the peak load was introduced, and the sensitivity considering the failure outage rate of the generator. Through the analysis, a methodology for obtaining the expected appropriate size for each facility of the microgrid is proposed as a relational formula with good field applicability by introducing a random variable. This was verified by a case study on a real developing country area

중권 및 동심권을 적용한 정수 슬롯 영구자석 동기 전동기의 비교 연구 Comparative Study of Integer-slot PMSM with Lap Winding and Concentric Winding

김형우(Hyung-Woo Kim) ; 강도현(Do Hyun Kang) ; 이승창(SungChang Lee) ; 정상용(Sang-Yong Jung) ; 이철균(Cheol-Gyun Lee)

Winding method differs majorly by number of slots per phase per pole(NSPP). If those of NSPP are integer, Concentrated Winding and Distributed Windings are used. Distributed Windings can be further classified into Lap Winding and Concentric winding according to the pitch distribution of coils. The number of turns and the number of pitch are same between each coil in Lap Winding with Fractional(Short) Pitch. On the other hand, the number of turns in each coil can be different for Concentric Winding maintaining the number of turns per pole. Air-gap Magnetic Motive Force(MMF) distribution appears differently depending on the ratio of turns in each coil. In this paper, the No-load performance of Permanent Magnet Synchronous Motor with Lap Winding and Concentric winding is compared. Winding Factors are calculated to consider the MMF distribution analytically for each winding case. The electromagnetic performance of each winding case is analyzed through 2D Finite Element Analysis(FEA).

출력 전류 평형을 위한 커플드 인덕터를 적용한 다중 출력 LED 조명용 LLC 공진형 컨버터 분석 Analysis of LLC Resonant Converter for Multi-Output LED Driver with Coupled Inductor for Output Current Balancing

박상범(Sang-Beom Park) ; 이우철(Woo-Cheol Lee)

LED(Light Emitting Diode) lighting with a long life span and high efficiency is a light source used in various fields. In order to drive these LED modules, a PFC converter and a DC-DC converter capable of controlling the current constant are required. Conventional single output LED converters can achieve high efficiency and high power density, but there is a problem that high capacity and low utilization make maintenance difficult. In order to output a plurality of LED lighting, constant current characteristics are maintained for each output, and an independent converter of an LED protection circuit is required for each channel. Also, Multi-output LED converters have a problem that other LED lighting does not operate normally when one of the output LED lighting fails. Therefore, in this paper, it is suggested that multiple LED lighting can be driven without problems by applying 4 coupled inductor to one LLC resonance converter, and that other LED lighting can operate normally even if the output LED lighting fails.

10MW급 능동 차폐형 초전도 발전기 계자 전자석의 최적 설계 Optimal design of field coil magnet of 10MW-class actively shielded superconducting generator

방태경(Tae-Kyoung Bang) ; 이정인(Jeong-In Lee) ; 장강현(Gang-Hyeon Jang) ; 오제민(Je-Min Oh) ; 최장영(Jang-Young Choi) ; 조한욱(Han-Wook Cho)

In this paper, an optimal design was performed to improve the power density and specific power of a superconducting generator for 10MW-class actively shielded wind turbine using the response surface method (RSM). The objective functions of optimal design for reducing the weight of the generator were selected as perpendicular magnetic flux density, output power, and terminal voltage. The design variables were selected as three variables: field coil aperture, shield coil aperture and superconducting coil pitch (between shield and field aperture), which have a great influence on the objective function. After that, optimal design points were derived within the optimal region, and verification was performed through finite element analysis(FEM).

PdCu가 전기도금된 레이저 유도 그래핀 전극을 이용한 에탄올 효소 센서 개발 Development of Enzymatic Ethanol Sensor Based on PdCu Electrodeposited Laser Induced Graphene Electrode

정해택(Haetaek Jeong) ; 박상현(Sang Hyun Park) ; 강승조(Seung-Jo Kang) ; 박정호(James Jungho Pak)

This paper presents fabrication and characterization of an ethanol sensor whose working electrode (W.E.) is made consists of electrodeposited PdCu on laser induced graphene (LIG) layer and drop-casted alcohol oxidase (AOx) enzyme. AOx reacts with ethanol to generate hydrogen peroxide and the electrodeposited PdCu works as an electrocatalyst of hydrogen peroxide in order to increase amperometric output current. The optimum conditions for the ratio between Pd and Cu, the drop-casted AOx amount, the pH value of PBS have been obtained by varying the fabrication conditions and comparing the output results. Field emission scanning electron microscope (FE-SEM) and Raman spectroscopy were used to confirm LIG electrode formation. Also, Energy-dispersive X-ray spectroscopy (EDS) was performed to verify the ratio of the electrodeposited Pd and Cu. Cyclic voltammetry (CV) analysis of the W.E. showed that the peak reduction current occurs at ?0.045 V. and this voltage was chosen as an applied voltage in amperometric measurement. Electrochemical impedance spectroscopy (EIS) shows that the charge transfer resistance of the PdCu deposited LIG W.E. is lower than the bare LIG W.E., which also shows the output current accordingly. Chronoamperometric response of the fabricated sensor was measured at various ethanol concentrations in range of 0-12 mM, and the linear sensitivity was 17.99 ㎂mM-1cm-2. which is similar or better than those of the recently reported other ethanol sensors.

MOSFET 고주파 노이즈의 물성 기반 인공신경망 모델링 A Physics-Based Neural Modeling for High Frequency Noise of MOSFETs

이종환(Jonghwan Lee)

A new neural model is presented to predict the dynamic characteristics of high frequency noise in nanoscale MOSFETs with ultrathin gate oxide. The model is formulated by combining physical theories with the differential and integration of the radial basis function (RBF) from an original artificial neural network (ANN). The high frequency noise model includes the channel thermal noise, the induced gate noise, their correlation noise as well as the shot noise generated by the gate leakage current through the ultrathin gate oxide. By training a Fano factor of the shot noise and spatial distribution of the channel thermal noise, this approach forms a physics-based neural modeling that naturally encodes underlying physical theories as prior information. The model exhibits a good performance for predicting the noise behavior at high frequencies.

이중 편파 RF 에너지 하베스팅 시스템을 위한 최적 정류 회로 설계 Design of Optimal Rectifier Circuit for Dual-Polarized RF Energy Harvesting System

박정수(Jeong-Su Park) ; 이왕상(Wang-Sang Lee)

In this paper, a optimal rectifier circuit for dual-polarized RF energy harvesting system operating at 2.45 GHz is proposed. RF power incident from a dual-polarized antenna is converted to DC using individual Dickson charge pump rectifier circuits. According to the series or parallel-connected rectifier circuit with multiple stages, the harvesting voltage and its rectifying efficiency are analyzed and measured. From the experimental verification, the number of stages of the dickson charge pump and the output power according to the series and parallel connections of DC output were compared. The parallel two-stage circuit for dual-polarized RF energy harvesting achieved a maximum voltage of 1.35 V and a power of 0.91 mW, and a rectifying efficiency of approximately 20%.

다입출력 불확실 선형 플랜트를 위한 출력 예측 성능을 갖는 슬라이딩 면 변환 적분 슬라이딩 모드 제어 Sliding Surface 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 sliding surface transformation SMCs by using the transformed integral sliding surface without the reaching phase and with the output prediction performance are presented for MIMO uncertain linear plants. Theoretically discontinuous and practically continuous sliding surface transformed VSSs are proposed. The transformed integral sliding surface with the 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 predetermined and predicted. 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 MIMO VSS design for the output prediction performance. Another 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 for the entire trajectory. The discontinuity of the control input as the inherent property of the VSS is much improved in view of the practical aspects. Through a design example and simulation studies, the usefulness of the proposed discontinuous and continuous sliding surface transformed VSS controllers is verified.

자속 차폐벽을 갖는 선형 홀센서 BLDC 모터를 이용한 전기식 조종날개 구동장치의 위치 제어 Position Control of Electro-mechanical Fin Actuator using Linear Type Hall-effect Sensor BLDC Motor with Magnetic Flux Shielding Wall

구정회(Jeong-Hoi Gu) ; 배륜준(Ryun-Jun Bae) ; 최장영(Jang-Young Choi)

In general, position sensor and velocity sensor are used to design robust controller of the electro-mechanical fin actuator system. However, the use of such a sensor causes problems such as an increase in cost, an additional space for mounting, and a decrease in system reliability due to a sensor failure. To overcome these problems, rotor position sensor of the BLDC motor was replaced with linear type Hall-effect sensor having a magnetic flux shielding wall from the latch type Hall-effect sensor. The conventional position sensor and velocity sensor were removed through a position and velocity implementation algorithm using the analog output of the linear type Hall-effect sensor. In order to prove the validity of the proposed method, various comparison tests were performed with the existing position/velocity sensors. As a result of the test, the method proposed in this paper can obtain the position response similar to the case of applying the conventional position/velocity sensor.

모델 불확실성이 있는 1기 무한모선 계통의 선로 고장 감지를 위한 PI 관측기의 성능 개선 Performance Improvement of a PI Observer for Line Fault Detection of a Single Machine Infinite Bus System Under Model Uncertainty

김준우(Jun Woo Kim) ; 양선직(Sun Jick Yang) ; 손영익(Young Ik Son)

This paper proposes a method for improving disturbance estimation performance of a PI observer for line fault detection of the single?machine infinite bus (SMIB) power system under the model uncertainty. The SMIB model of the paper is described by an improved swing equation that reflects more realistic dynamic characteristics than the conventional one. The proposed method begins with the conventional swing equation and the PI observer for the exact disturbance estimation. Model uncertainty arising from the model difference is first estimated using the estimated equivalent disturbance by the PI observer during equilibrium operation. Next, the uncertain parameters are estimated by applying the Recursive Least Square algorithm to the modified swing equation by using the estimated term at the first step. The angular velocity and acceleration information for the RLS algorithm can be also estimated by the PI observer based on the modified swing equation. Finally, the estimated parameters are adopted to the proposed PI observer and its disturbance estimation performance can be improved effectively for the line fault detection. The performance of the proposed algorithm is verified by computer simulations of the improved SMIB power system model.

태양광 패널 청소용 로봇의 설계, 구현 및 실험 Design, Development, and Experiment of a Solar Panel Cleaning Robot

권동욱(Dong-Wook Kwon) ; 정슬(Seul Jung)

This paper presents the design and implementation of a solar panel cleaning robot, which is a tracked wheel mobile robot to move on the solar panel. In order for the robot to stick on the solar panel without sliding down, suction mechanism has been designed and implemented. The suction pad is designed to press the panel by controlling air pressure in the vacuum chamber. Since the robot has to move around on the solar panel, not only pressure control but also position control is required. To change the moving direction, body turning mechanism is employed to change the heading direction since tracked wheels have a difficulty of turning. For the heading angle control, sliding mode control is used while position is controlled by PD control. Experimental studies for the robot to move up and down on the solar panel are conducted to demonstrate the functionality of the robot.

GAN 기반 공간 적응적 비 정규화를 통한 단일 영상 초해상도 복원 GAN based Single Image Super-Resolution via Spatially Adaptive De-normalization

윤종수(Jongsu Yoon) ; 김태현(Taehyeon Kim) ; 최윤식(Yoonsik Choe)

Despite recent advances in technologies on single image super-resolution using deep neural networks, the key question still remains how to recover finer textures and edges. To solve this super-resolution problem, many recent researches have been using conditional generative adversarial network. However, restoring high resolution images using conditional generative adversarial network is disadvantageous in expressing fine textures and edges because there occurs the loss of spatial and high frequency informations. In this paper, informations on images in different scales are added hierarchically by using a spatially adaptive de-normalization method. This method can restore fine textures and edges of an image by inserting different scale informations for each layers in pyramid structure. In experimental results, the efficiency of the proposed method is proved by showing better performance to restore textures and edges in high quality, comparing with other state-of-the art techniques.

함정 근접방어체계의 요격성능 향상을 위한 고기동 표적의 장시간 궤적 예측기법 Long-term Trajectory Prediction of Highly Maneuvering Target for Advanced Naval Close-In-Weapon Systems

함다혜(Dahye Ham) ; 조형찬(Hyung-Chan Cho) ; 나원상(Won-Sang Ra) ; 안지훈(Ji-Hoon An) ; 김상현(Sang-Hyun Kim) ; 박준현(June-Hyune Prak)

This paper proposes a precise long-term trajectory prediction algorithm for the interception of highly maneuvering targets by a naval close-in-weapon system (CIWS). Ensuring satisfactory kill-probability, a target’s flight dynamics is described as the nonlinear differential equation with two slowly varying parameters. Our system model also contains the unknown control gains representing the general form of guidance laws, which can be modeled as random walk processes to cope with the versatile target maneuver in the terminal guidance phase. As a result, the long-term trajectory predictor is easily designed by applying the unscented Kalman filter for the probabilistic nonlinear state-space model. Through the simulations for typical ASM target engagement scenarios, it is demonstrated that the proposed filter is beneficial to improve the accuracy of the impact point calculation, which is necessary for the fire control algorithm of a CIWS.

부하의 전압 내성 특성을 고려한 순간전압강하 평가 연구 A Study on the Assessment of Voltage Sags Considering the Voltage Tolerance Characteristics of Loads

채하경(Hakyung Chae) ; 박창현(Chang-Hyun Park)

This paper presents a novel method to assess voltage sags by taking into account the voltage tolerance characteristic of loads. In general, the tolerance characteristic is expressed in the form of a two-dimensional curve of voltage magnitude and duration. Also, the shape of characteristic curves depend on the type of loads. In order to estimate the expected sag frequency affecting sensitive loads, it is necessary to perform a voltage sag assessment considering the voltage tolerance curves of loads. However, because most existing methods of voltage sag assessment only focus on voltage sag magnitudes, these methods have limitations in reflecting various types of tolerance curves. In this paper, an effective method for reflecting various thresholds of sag magnitude and duration is proposed. The proposed method performs voltage sag assessment based on the area of vulnerability for given voltage thresholds and sag durations are estimated using a probability model on the historical operation data of protection system. In addition, we propose an effective assessment scheme based on the concept of measuration by division for a slope-shape tolerance curve.

보조전원장치용 단상 컨버터 직류단 커패시터 정전용량 예측 Capacitance Prediction of Electrolytic Capacitor for Single Phase Converter of Static Inverter

김민섭(Min-Seop Kim) ; 최용은(Yong-Eun Choi) ; 오효석(Hyo-Seok Oh) ; 김재문(Jae-Moon Kim)

In this paper, to solve the difficulty of attaching current transducer on the electrolytic capacitor, a technique that can indirectly estimate the current flow of the capacitor during electric multiple unit’s operation is presented. Moreover, life prediction study is conducted to estimate the amount of change in impedance and capacitance for predicting an appropriate replacement timing of the capacitor. Accordingly, the experimental circuit was constructed and then verification is performed with a LCR meter to validate the impedance and capacitance estimation techniques. The results from the verification showed an error rate of 5%, therefore, validating the proposed method for the application of electric multiple units.

IT접지 저압직류배전 수용가에서의 인체감전 영향 및 접지 임피던스 선정에 관한 연구 Selection of the Earthing Impedance at the Source and Electrical Human Effect in IT Ground LVDC System for the End User’s

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

All over the world, renewable energy had been gotten attention because of the clean energy, low-cost. and so on. The solar generation and energy storage system(ESS) which are based on the DC power system have different characteristics from the general AC system and are close to the end-user of the electric. For these reasons and other positive aspects, the low voltage direct current(LVDC) system, had been studied. The LVDC system has a more complex configuration since the power sources and ground types in IEC 60364. One of them, IT system has the earthing impedance at source and it is more safe than other ground types in aspect fault current passing the human body. So, it has been expected to be used in end-user system. Until now, most of the studies about the LVDC system was related to the power distribution system like load unbalance, fault analysis, efficiency, and so on. However, the standards about the earthing impedance at the power source for electrical safety did not exist. So, in this paper, the selection of the earthing impedance in IT LVDC system has been studied in an aspect of human electrical safety. For the research, the simulation was performed based on IEC 60364 and IEC 60479 through the Matlab/Simulink and test experiments were conducted. Through the research, it was confirmed the electrical safety according to the source types, voltage level and earthing impedances. Also, it was analyzed the selection of earthing impedance value for the less human effect when the electrical shock occurred.