https://doi.org/10.5370/KIEE.2023.72.9.967

이성희(Sung-Hee Lee) ; 이우남(Woo-Nam Lee) ; 심상우(Sang Woo Shim) ; 원종집(Jong Jip Won) ; 양유정(Yu Jeong Yang) ; 박종배(Jong-Bae Park)

In order to respond to climate change, the need for the use of renewable energy is increasing, and as a result, generation companies are obliged to provide part of the generation amount as renewable energy through the RPS system. The mandatory share in RPS system will continue to increase, and it is essential to increase the amount of generation through renewable energy. Purchasing REC is a common way to fulfill obligation because of difficulties for installing power generation facilities to generate renewable energy. However, in order to purchase REC through a long-term contract, information on future REC prices is essential, and future REC prices can only be identified through forecasting. Therefore, this paper presents a method for forecasting REC prices. The feature for forecasting was configured to consider factors such as renewable energy-related policies, and the stability of the predicted value was presented by using forecasting models with various characteristics.

https://doi.org/10.5370/KIEE.2023.72.9.975

이경민(Kyung-Min Lee) ; 박철원(Chul-Won Park)

Recently, technology development for PMU (Phasor Measurement Unit) data analysis system and Korean-style WAMAC (Wide Area Monitoring And Control) construction is being pursued for stable system operation and cost reduction. With high-speed sampling up to 256 times per cycle and the ability to collect time synchronized big data based on GPS signals, PMUs offer advantages over today SCADA/EMS (Supervisory Control and Data Acquisition/Energy Management System) and PQMS (Power Quality Monitoring System), it is possible to build an accurate and real-time condition monitoring system. By processing a vast amount of PMU big data, useful and valuable information can be delivered. In this paper, processing and fault analysis are performed for the utilization of big data collected by 35 PMUs installed in 154kV ○○ S/S (Substation). First, we introduce the PMU installation points of the S/S and collect PMU big data to understand the data structure. After performing the pre-processing in the form of a snapshot, we analyse the voltage, and power comparisons. In addition, the analysis is performed through the IVFR (instantaneous voltage fluctuation rate), which can efficiently monitor system changes acquired from multiple measurement points. The pre-processing and fault analysis are implemented using the language of Python 3.7 version. Finally, an aim of this study is to analyze the impact of power grid faults on ○○ S/S.

https://doi.org/10.5370/KIEE.2023.72.9.982

김도인(Do-In Kim)

This paper proposes the event-based power system situational awareness method by utilizing PMU infrastructure. The proposed algorithm is specifically configured as algorithm that can be utilized in a wide area power system using an optimized set of PMUs and a window frame configuration. The key to utilizing an optimized set of PMUs is imaging each measured time series data with a wavelet transform to efficiently enable the CNN-based classification. The proposed CNN-LSTM based event classification technique is able to classify event categories implemented in the power system. Finally, the proposed algorithm is verified through simulation, and represents the performance evaluation according to the number of PMU measurements

https://doi.org/10.5370/KIEE.2023.72.9.987

황동준(Dong-Jun Hwang) ; 김철환(Chul-Hwan Kim)

The voltage source is distorted or the voltage distorted by the Switching Modulation Power Supply and cable impedance components generates harmonics in the leakage current, which causes erroneous detection of single line-to-ground fault(SLGF). In the past, to prevent erroneous detection of SLGF due to leakage current, Fast Fourier Transform(FFT) was used to determine SLGF only with the fundamental wave component, but FFT can generate errors depending on the sampling frequency. This paper proposed a new type of zero-phase current detection method using CNN in High Resistance Grounding System. The simulation was performed in the proposed High resistance grounding system(HRGS), and a CNN model generated with a distorted voltage source (reflecting harmonics frequently generated in the proposed system) and a harmonics generating load (rectifier) was verified. As a result, it was confirmed that the zero-sequence current fundamental wave was accurately detected and that an accurate SLGF determination was possible.

https://doi.org/10.5370/KIEE.2023.72.9.994

이륜경(Ryungyeong Lee) ; 신훈영(Hunyoung Shin)

With the target of global Net-Zero, the future power system needs to consider planning and operation approaches based on the stochastic properties of renewable energy. In this paper, we present the methods of wind speed scenario generation using conditional forecasting error. The proposed method utilized LSTM model to forecast the wind speed. In addition, it employed a copula function to cope with a dependency of wind speed and its wind forecasting value and estimated the conditional distribution of forecasting error. The effectiveness of the presented method was verified using a real wind speed data. The simulation results demonstrated that the various scenario generation can be obtained from the estimated conditional forecasting error, which is expected to be used for detailed power system analysis.

https://doi.org/10.5370/KIEE.2023.72.9.1002

박소진(SoJin Park) ; 신훈영(Hunyoung Shin)

As renewable energy sources continue to increase, there is a corresponding reduction in the inertia provided by synchronous generators, leading to growing concerns on the maintenance of stable frequency. A net load expected to be in the future system, raises the challenging prospect of sustaining adequate system inertia. In this paper, we introduce an inertia-constrained unit-commitment model for the Korean power system in the year 2030. A future net load scenario is derived using a time series clustering algorithm. Through the examination of these scenarios, we find a pressing need to consider minimum inertia response requirements in power system operation. Consequently, we propose a unit-commitment model that incorporates this inertia requirement. The simulation results demonstrate that a future system needs to implement an inertial monitoring system to evaluate the level of synchronous inertial response (SIR) and enable its integration into the operation of the power grid.

https://doi.org/10.5370/KIEE.2023.72.9.1012

이경민(Kyung-Min Lee) ; 박철원(Chul-Won Park)

If operation is interrupted due to unwanted motor fault by various reasons, it can cause enormous damage, including recovery time, cost, and quality loss. To avoid this problem, an EOCR (Electronic Over Current Relay) that monitors and protects the motor is being widely used. Recently, the concept of fault prediction based on the prognosis according to the state is attracting attention. In this paper, in order to improve the smart EOCR for MCC (Motor Control Center) with fault prediction, we detect and compare fault of pump systems using AI (Artificial Intelligence) technology. First, a pump system for smart EOCR is introduced, and a data set is constructed by collecting normal and abnormal state data of pump system. We design and implement a fault detection technique based on DNN (Deep Neural Network) and SVM (Support Vector Machine). Finally, by comparing the simulation results of the two fault detection techniques using AI, the performance evaluation is carried out.

https://doi.org/10.5370/KIEE.2023.72.9.1018

장지연(Jiyeon Jang) ; 김인수(Insu Kim)

In power systems, faults, such as ground faults and short circuits, and non-fault disturbances, such as large load fluctuations and unbalances, occur frequently. However, the power system responses to power faults and non-fault disturbances are different. Therefore, it is essential to accurately distinguish between faults and non-fault disturbances in power systems. Previous studies have collected large-scale data by monitoring real-time parameters of the power system and detecting the occurrence of power system faults. However, this study does not focus only on diagnosing power system faults but also on accurately distinguishing between faults and non-faults disturbances and uses various classification models to train the data and evaluate and analyze the prediction results. Collecting power system parameters when faults and non-faults disturbances occur is not easy. Therefore, this study used DIgSILENT PowerFactory software to simulate faults and non-faults disturbances in the power system and collected 120 small data sets. The data collected for the 120 cases consists of various metrics such as voltage, current, frequency, rotor speed, and HVDC parameters. This study used seven classification models for training and prediction: decision tree, gradient boosting classifier, k-nearest neighbors, logistic regression, naive Bayes classification, and random forest regression. In addition, this study introduced an importance-based data reorganization method to improve the performance of the best-performing classification model and analyzed its effectiveness.

https://doi.org/10.5370/KIEE.2023.72.9.1029

신창훈(Chang-hoon Shin) ; 차한주(Hanju Cha)

This paper proposes a net-load forecasting method for the PV integrated distribution line using hybrid regression model. The hybrid model is combined such that an ARIMA model is assigned for pure load forecasting and an MLR model using weather forecasting information is established for PV generation forecasting. Therefore, the hybrid model enables to forecast net-load of the distribution line with better accuracy than that of ARIMA only model. The validity of the proposed method is verified through the accuracy analysis based on the forecasting results of a real distribution line with its actual load, PV generation and net-load data. The proposed method can be widely applied to other studies such as overload analysis, load transfer planing and ESS scheduling of a distribution line.

https://doi.org/10.5370/KIEE.2023.72.9.1035

류호선(Hoseon Ryu) ; 이셩구(Kyungkyu Lee) ; 허건(Geon Heo) ; 박용순(Yongsoon Park)

Irregular power generations from renewable energy sources and instantaneous load fluctuations cause frequency stability problems in an island grid. The grid frequency in an island grid generally undergoes lager fluctuations compared to other grids due to its low grid inertia. Recently, virtual synchronous machine (VSM) technologies based on battery energy storage systems (BESSs) are emerging as a solution to enhance the grid inertia. A VSM emulates behaviors of a synchronous machine through an inverter to provide the inertial and damping responses. This paper addresses the development of VSM to stabilize grid frequency of Biyangdo, small island around Jeju island in South Korea. The developed VSM algorithm has been applied to a 250kW-BESS inverter in Biyangdo. The effectiveness of applying VSM in the island grid is assessed through the on-site test results.

https://doi.org/10.5370/KIEE.2023.72.9.1041

최나모(Na-Mo Choi) ; 원요섭(Yo-Seop Won) ; 김성일(Sung-Il Kim)

As interest in factory automation and smart factories expands worldwide, the demand for process equipment used in them is also increasing. in line with this trend, the development of permanent magnet linear synchronous motors (PMLSM) that can be easily combined with multiple is also actively progressing. PMLSM is possible to connect various production facilities and inspection equipment with a single line with minimal space use, and it is easy to respond to changes in related facilities. In addition it is not only enables linear motion without other mechanical parts, but also does not cause any problems caused by abraison because it does not generate mechanical contact. However, since mechanical interference between the mover and the stator may occur in PMLSM depending on the applied load, it is necessary to design the air gap differently. Therefore, the rate of change in thrust according to the air gap length was analyzed through finite element analysis for the various models with different pole pitches.

https://doi.org/10.5370/KIEE.2023.72.9.1047

최형진(Hyung-Jin Choe)

This paper proposes a passive snubber for the quadratic boost converter to reduce the switching turn-on and turn-off losses. The proposed snubber consists of one inductor, two capacitors, and two diodes. The snubber inductor controls the current slope of the switch, and the snubber capacitors reduce the maximum voltage of the switch. Using the LT-Spice simulator, the switching loss of the proposed converter was compared with a conventional quadratic boost converter, and the simulation results show that the switching loss of the proposed converter was improved by 21.3% from that of the conventional quadratic boost converter. A 15 W proto-type was manufactured and compared with a conventional quadratic boost converter at VIN = 4.2 V, VO = 24 V, Pout = 1 ∼ 15 W, and fSW = 290 kHz. The experiment confirmed that the efficiency of the proposed circuit was improved by 6.09% at Pout = 1 W and 1.90% at Pout = 15 W, and the switch driving temperature was lowered by 4.7 ℃ at Pout = 8 W and 3.9 ℃ at Pout = 15 W compared to the conventional quadratic boost converter. This result shows that the proposed circuit is suitable for a structure to reduce the switching losses of conventional quadratic boost converter, and it can be expected that it could be used in various power applications requiring a high input to output voltage conversion ratio.

https://doi.org/10.5370/KIEE.2023.72.9.1057

방정율(Jeong-Yul Bang) ; 최동호(Dongho Choi) ; 박진혁(Jin-Hyuk Park) ; 이준석(June-Seok Lee)

This paper presents the design and verification of DC-DC Converter based on Partial Power Processing (PPP) for Hydrogen fuel cell locomotive. Full Power DC-DC Converter (FPC), which is a traditional DC-DC Converter, performs the power transfer by only using the power converter. It causes the bigger size of the power converter, lower power density, and reduced power conversion efficiency. In contrast, input power in Partial Power Converter (PPC) is distributed between power converter and DC-bus. This can reduce the magnitude of the power that is transferred by the power converter, which can lead to a smaller and more efficient system. In this paper, Input-Parallel-Output-Series-setup (IPOS-setup) architectures and Dual Active Bridge (DAB) converter were selected as the PPC architecture and the power converter topology to design the optimal PPC, and it has a maximum power rating of 200kW. To compare PPC and FPC, the size and the efficiency of the system are used. Efficiency of PPC and FPC are drawn through PSIM Thermal module, and down-sized experiment results. This paper proved that PPC can achive up to 1.8% higher efficiency than FPC.

https://doi.org/10.5370/KIEE.2023.72.9.1066

응웬 민 호앙(Minh Hoang Nguyen) ; 곽상신(Sangshin Kwak)

This paper presents an in-depth investigation of different types of 3-phase 4-wire converters commonly used in power electronics applications. The paper begins by providing an overview of the significance of 3-phase 4-wire converters in modern power systems and their relevance in addressing per-phase active thermal control for prolonging the lifetime of specific phase leg or asymmetrical operation for unbalanced conditions. Subsequently, a detailed examination of various converter topologies, such as 2-level 4-leg converter and 3-level 4-wire converter, is presented. Each topology is explained, highlighting their operational mechanisms, control and applications. Additionally, the output performance comparison between different types of 3-phase 4-wire converters is evaluated in terms of output current total harmonic distortion (THD) value, leakage current root-mean square (RMS) value, and power losses. The performance comparison results are obtained by implementing in simulation environment of PSIM program.

https://doi.org/10.5370/KIEE.2023.72.9.1076

최광식(Kwang-Sik Choi) ; 조재철(Jae-Cheol Cho)

The IEC60270 standard requires a highly reliable measurement system without errors caused by noise pulses and background noise levels in DC partial discharge diagnosis. Since the partial discharge signal is an impulse signal, and the air corona and the plasma discharge noise pulse are also impulse signals, the two signals are similar, which hinders partial discharge diagnosis. Therefore, in order to measure DC partial discharge with high reliability without interference, there is a need for a device that completely removes impulse noise pulses having similar characteristics to partial discharge and is not affected by the background noise level. To this end, in this paper, an impulse noise pulse canceling device equipped with two types of high-speed analog-digital hybrid circuits were developed, and through three types of tests, it was verified that it was accurate in the partial discharge measurement process and highly reliable due to its high signal-to-noise ratio.

https://doi.org/10.5370/KIEE.2023.72.9.1083

황예지(Ye-Ji Hwang) ; 이창열(Chang-Yeol Lee) ; 최원석(Won-Seok Choi) ; 권혁훈(Hyuck-Hoon Kwon)

In this study, we propose an algorithm that considers the seeker look angle constraint, which has a significant effect on the intercept rate in missile terminal homing guidance. The algorithm was configured by integrating missile guidance and control, and MPC(Model Predicted Control). In the proposed method constructs an optimization problem based on the ADMM(Alternating Direction Method of Multipliers) method to derive a trajectory that minimizes the use of Energy and satisfies the constraints. Missile's flight control is mainly performed in an embedded computing environment, so a parallel computing technique was applied to improve the algorithm's real-time performance. The designed parallel computation technique was loaded into embedded computer with a GPU, and computation time analysis was performed for the feasibility and real-time performance of the trajectory design algorithm.

https://doi.org/10.5370/KIEE.2023.72.9.1091

김진훈(Jin-Hoon Kim)

So far, most stability results of the time delay systems have been obtained using one LKF(Lyapunov-Krasovskii functional). In this paper, to get a less conservative result, we divide the time delay into two sections, and derive a stability condition using two LKFs that are different in the divided section but identical at the boundary. The stability condition is that the time derivative of LKF in each region is negative. By using several inequalities, a stability condition in the form of LMI was derived. Finally, the usefulness of the derived result was shown through two well-known examples.

https://doi.org/10.5370/KIEE.2023.72.9.1097

장광선(Gwangseon Jang) ; 김윤정(Yunjeong Kim) ; 황명하(Myeong-Ha Hwang)

국가R&D(Research & Development) 과제를 수행하는 기관이 증가함에 따라 과제 수행기관별로 R&D정보를 제공하는 분석 서비스에 대한 수요가 증가하고 있다. R&D과제 중심으로 구축된 데이터를 수행기관 중심으로 변경하여 정보를 제공하기 위해서는 수행기관의 식별작업이 필수적이다. 기존에는 사업자등록번호, 법인번호, 시스템별 관리용 기업 코드와 같은 식별 코드를 활용하거나 사용자가 입력한 기관명의 문자열 매칭을 기반으로 식별작업을 수행하였다. 그러나 기존 방법은 사용자의 오기 및 이형명을 고려하지 못하는 문제점으로 인하여 오식별 하는 문제가 발생하였다. 본 연구는 BERT를 활용한 의미론적 유사도와 최장 공통 부분 문자열(Longest Common Substring, LCS) 알고리즘 기반의 문자열 유사도를 적용한 하이브리드 시스템인 SMART-ID를 구축하여 문제점을 개선하고자 한다. SMART-ID는 R&D 수행기관 식별정보 갱신 자동화 및 R&D 연구과제데이터의 기관명 검증, R&D 연구과제 데이터의 수행기관 식별 코드 자동할당, 텍스트 기반 수행기관 검색 작업을 수행할 수있다. 국가과학기술지식정보서비스(NTIS)의 실제 데이터를 기반으로 위 3가지의 작업에서 SMART-ID의 우수한 성능을 입증하였다. SMART-ID은 향후 국가과학기술지식정보서비스의 챗봇 내 기관명 인식 모듈로 활용하여 더욱 정확한 기관별 통계및 검색 정보를 제공하는데 활용될 것이다.

https://doi.org/10.5370/KIEE.2023.72.9.1107

윤치명(Chi-Myeong Yun) ; 김형철(Hyungchul Kim) ; 김한수(Hansoo Kim) ; 김말수(Malsoo Kim) ; 정호성(Hosung Jung)

In this paper, the matters to be considered by the regenerative inverter according to the low or high-voltage connection plan of the railway were analyzed to utilize the regenerative energy generated by the urban railway DC traction system. Criteria for various considerations such as energy flow, voltage fluctuations, and power quality of regenerative energy were presented when connecting the railway traction system. Power analysis simulations were used to analyze whether criteria were satisfied. The power analysis program PSCAD/EMTDC confirmed that the criteria were satisfied below the international standard IEEE-519 according to the low-voltage and high-voltage connection method.

https://doi.org/10.5370/KIEE.2023.72.9.1113

홍석진(Sukjin HONG) ; 이종우(Jongwoo LEE)

Railway interlocking systems are safety-critical systems, which are required to show its safety. There are several methods to demonstrate the interlocking systems safety, which are process based proving, proven design methods, model based method and so on... One of most use methods is model based methods for safety proving method. The modelling of the interlocking systems is realized through mathematical modelling by using set theory. The interlocking systems are composed of tracks, point machines, signals and controllers which become route parts. The each physical components of the interlocking systems are modeled in a set and developed set models for routes and routes controls. By using set theory, we provided set model of the interlocking systems and compared the model with relay based logic circuits how to apply set model to real systems.

https://doi.org/10.5370/KIEE.2023.72.9.1124

최상열(SangYule Choi)

Direct Load Control(DLC) program is an advanced agreement between a power utility and customers to control some customers’ appliances (e.g., air conditioners and water heaters). It is an incentive-based demand response system in which the utility provides the affected customer with financial incentives. Under the existing DLC program, the utility turn on/off customers’ appliances without considering the customer's inconvenience. that causes a lot of customers are reluctant to participate in the DLC program. In this paper, To solve this problem, the author present weather based intelligent demand controller to analyze correlation between weather condition and customers energy consumption and to predict customers energy consumption. To demonstrate the validity of the proposed demand controller, porto type demand controller are developed and applied to real customer load.

https://doi.org/10.5370/KIEE.2023.72.9.1129

조동일(Dong-Il Cho) ; 문원식(Won-Sik Moon) ; 김재철(Jae-Chul-Kim) ; 남태양(Tae-Yang Nam)

The Medium Voltage Direct Current (MVDC) system is gaining attention as a solution to the power supply instability issues arising from the growth of renewable energy sources. MVDC networks are directly connected to the load, leading to a significant cascading effect in the event of a power outage. Therefore, ensuring safety through asset management is required. In this paper, a maintenance strategy is selected using sensitivity analysis at the component level. The structure of components and systems is understood through Functional Block Diagram. And reliability indicators are calculated based on their relationships. Based on repair time, the importance is ranked through the sensitivity analysis of the failure rate and availability. A maintenance strategy is established based on the top rank. The proposed sensitivity analysis method is compared through cost analysis with Time-Based Maintenance and Reliability Centered Maintenance application cases.