https://doi.org/10.5370/KIEE.2025.74.11.1757

김준혁(Jun-Hyeok Kim)

This study proposes an unsupervised framework for detecting load-transfer events in distribution systems, which are frequent but hard to identify due to missing external logs and lack of labeled data. Using only load time series data, the method first removes seasonal and trend components via Robust STL decomposition. The residual signal is transformed using a Haar-based Stationary Wavelet Transform, and candidate change points are identified by the Pruned Exact Linear Time (PELT) algorithm. For each point, 15 statistical features are computed, including load variation, residual statistics, slope, ratio, and time location. These features are used as input to an Isolation Forest-based anomaly detector, which probabilistically determines load-transfer events. The method shows that accurate detection is possible using load data alone, without external sensors or prior labels, offering a scalable and practical solution for real-world distribution system monitoring.

https://doi.org/10.5370/KIEE.2025.74.11.1763

임종훈(Jong-Hun Lim) ; 김경화(Kyeong-Hwa Kim)

In modern subway stations, inductive loads such as HVAC systems, lighting, and elevator equipment are concentrated, resulting in large fluctuations in power demand and increased reactive power consumption. These load characteristics can cause various problems such as voltage drop, insufficient facility capacity, and deterioration of power quality. In this study, the distribution system structure and load characteristics of Incheon Metro stations were analyzed, and the application of FACTS (Flexible AC Transmission Systems) was proposed as a reactive power compensation measure to secure voltage stability and operating margin without adding substations. The voltage collapse point was identified through P?V (Nose) curve and V-Q curve analysis, and the compensation effect was quantitatively verified by comparing the system performance with and without reactive power compensation through MATLAB/Simulink simulation.

https://doi.org/10.5370/KIEE.2025.74.11.1775

이민규(Min-Gyu Lee) ; 이상윤(Sangyoon Lee)

This paper investigates the impact of the objective function in optimal power and carbon flow in carbon-aware power distribution system operation. We formulate the different types of objective functions that could minimize the power loss, power costs and carbon emission for the given power distribution system. To numerically investigate the carbon flow and emission generated by power distribution system power operation, we employ concept namely carbon emission flow that could approximate the virtual carbon flow in power system by power flow. Additionally, we employ ZIP load model to the proposed study to estimate the optimal power flow considering the voltage magnitudes in the distribution system. In the simulation investigation part, we compare the total power loss, substation power profile, total carbon emissions, and total power/carbon costs among different objective function employment in the power distribution system.

https://doi.org/10.5370/KIEE.2025.74.11.1784

김영일(Young-Il Kim) ; 노재구(Jae-Koo Noh) ; 이효철(Hyo-Chul Lee) ; 김예리(Ye-Ri Kim) ; 신진호(Jin-Ho Shin)

As the proportion of renewable energy increases, the instability of the power system is growing due to volatility of photovoltaic and wind power caused by weather and environmental conditions. Accordingly, the necessity to monitor renewable energy generation in real-time and manage power supply and demand to secure grid stability is increasing. This paper introduces a renewable energy data integration platform that collects and manages real-time power generation data from renewable energy generators nationwide in 1-minute resolution, and presents research on a technique to generate 1-minute resolution measured data using 1-hour resolution metering data collected during missing periods, based on a regression analysis technique when real-time power generation data is missing due to communication errors, etc.

https://doi.org/10.5370/KIEE.2025.74.11.1791

김태현(Tai Hyun Kim) ; 심상우(Sangwoo Shim) ; 박종배(Jong-Bae Park) ; 이성희(Sung-Hee Lee) ; 정연제(Yeonjei Jung) ; 조성봉(Sung Bong Cho)

This study quantitatively evaluates the impact of increasing direct LNG imports on Korea's electricity market using machine learning, PLEXOS simulation, and statistical analysis. The results consistently showed that direct LNG imports effectively reduce system marginal prices and electricity purchase costs for KEPCO, confirming their positive market influence. Policy recommendations include easing regulatory constraints and enhancing public-private collaboration to ensure energy security, supply stability, and market flexibility.

https://doi.org/10.5370/KIEE.2025.74.11.1801

최원영(Won-Young Choi) ; 김인수(Insu Kim)

This paper presents a harmonic analysis methodology based on a three-phase impedance matrix under balanced system conditions, targeting voltage and current distortion caused by inverter-based distributed generation (DG). Unlike conventional single-phase approaches, the proposed algorithm constructs harmonic-specific impedance matrices to analyze individual harmonic orders. Two case studies are conducted: a 5-bus ring system and an 8-bus system with transformer connections. In the 5-bus system, a 40 MVAr DG injects harmonic current, and it is observed that reducing load capacity from 130% to 70% increases the 5th-order harmonic voltage at bus 5 from 0.801% to 0.827%. In the 8-bus system, applying IEEE Std. 519-1 shows that increasing line impedance from 90% to 110% raises voltage THD from 7.695% to 13.024%, with a Pearson correlation coefficient (r) of 0.9507 and p-value (p) of 8.33e-5. Conversely, under IEC 61000-3-6, the current THD decreases from 56.7% to 46.0%, showing a strong negative correlation (r = ?0.9987, p = 2.67e-10) due to reduced allowable harmonic current. The results verify the accuracy of the proposed method via comparison with DIgSILENT simulations and confirm that both load condition and line impedance significantly impact harmonic distortion under different regulatory standards.

https://doi.org/10.5370/KIEE.2025.74.11.1810

신정훈(Jeong-Hoon Shin) ; 조윤성(Yoon-Sung Cho) ; 허견(Kyeon Hur) ; 맹종호(Jong-Ho Maeng) ; 박상호(Sang-Ho Park)

On April 28, 2025, Spain experienced Sub-Synchronous Oscillation (SSO) caused by high penetration of inverter-based renewable energy in a weak grid environment with low Short Circuit Ratio (SCR), along with a blackout. This study simulates a comparable event in the Korean power grid using PSS/E. A three-phase fault in the Anjwa region resulted in voltage oscillations. After the voltage exceeded 1.1 pu, which led to the tripping of 6 GW of renewable generation, the frequency dropped below 59.3 Hz, causing a further 4.5 GW of renewable generation to disconnect. STATCOM and GFM-ESS were implemented to mitigate voltage oscillations through dynamic reactive power support. Further analysis using PSCAD on a simplified grid revealed that the Power Plant Controller (PPC), combining VQ and PF control, effectively resolved the oscillation problem.

https://doi.org/10.5370/KIEE.2025.74.11.1817

김선오(Sunoh Kim) ; 정솔영(Solyoung Jung) ; 이재걸(Jaegul Lee) ; 오승찬(Seungchan Oh) ; 신정훈(Jeonghoon Shin)

Data centers in South Korea are expected to grow rapidly, particularly in the Seoul metropolitan area, raising concerns over declining grid flexibility and power system stability. This study proposes a control strategy to utilize the electrical load supported by data center on-line Uninterruptible Power Supply (UPS) systems as a flexibility resource for grid stabilization. The response speed and short-term energy storage characteristics of on-line UPS were analyzed and compared with those of Energy Storage Systems (ESS). Dynamic simulations were conducted under various Korean power system operating scenarios to evaluate frequency and voltage stabilization effects. The results show that a 1.05 GW UPS load-shedding event achieves frequency nadir and recovery performance comparable to a 1GW ESS deployment, while also contributing to voltage stabilization in metropolitan areas. In addition, the potential to alleviate certain generation constraints in the East Coast region was identified. To assess the power quality impact of UPS transfer, Electromagnetic Transient (EMT) analysis and field tests were performed, confirming no harmful effects on data center IT loads. This study demonstrates that UPS-based load-shedding in data centers can serve as a rapid flexibility resource at a level comparable to conventional ESS solutions.

https://doi.org/10.5370/KIEE.2025.74.11.1824

방형필(Hyeongpil Bang) ; 최장흠(Jang-Heum Choi) ; 문승필(Seungpil Moon) ; 신정훈(Jeonghoon Shin)

As the share of Inverter-based renewable generation increases, the physical(or rotation) inertia formerly supplied by synchronous generators declines, reducing the strength and stability of power systems. In response to decreasing inertia in the Korean power system, inertia-providing technologies are being introduced-namely high-inertia synchronous condensers, which supply rotational inertia, and grid forming inverters (GFMs), which provide synthetic (virtual) inertia to secure system stability. This paper explains the technical mechanisms by which Flywheel Synchronous Condensers( and GFM contribute to frequency stability, focusing on inertia provision and active-power support. Using dynamic models of these technologies, perform RMS time-domain simulations(using PSS/E) to analyze their stabilizing impacts on the power system during network faults and subsequent recovery.

https://doi.org/10.5370/KIEE.2025.74.11.1832

정호령(Horyeong Jeong) ; 문주영(Jooyoung Moon) ; 신정훈(Jeonghoon Shin)

In this study, we developed and validated Grid Forming(GFM) inverters capable of maintaining stable voltage and frequency based on voltage-source characteristics. To this end, major international grid codes were reviewed to derive GFM-related requirements and test standards. The control algorithms were verified through Electromagnetic Transient(EMT) simulations and Hardware in the Loop System(HILS). In particular, this paper focuses on P-HILS test results conducted in conjunction with a grid simulator to assess dynamic performance. The performance validated through P-HILS was further applied to a real-field demonstration in Jeju Island, which has a high share of renewable energy. The results confirmed that the GFM inverters met international standards in terms of P?f response, Q?V control, and Fault Ride Through(FRT). This study proposes GFM performance standards and test procedures tailored to the domestic power system environment, thereby contributing to the future expansion of GFM applications and the establishment of Inverter Based Resource(IBR) integrated grid systems.

https://doi.org/10.5370/KIEE.2025.74.11.1838

신경하(Kyung-ha Shin) ; 김광호(Kwang-ho Kim)

This paper presents a voltage-regulation method for distribution lines using photovoltaic (PV) output control via a supplementary interconnection device. The characteristics of distributed generation (DG) inverters connected to distribution networks have evolved through three generations. First-generation inverters lack output-control functions and cannot regulate voltage during normal operation. To mitigate the adverse voltage impacts of DG on distribution feeders, this study proposes a method to control the PV output current injected into the distribution line through the interconnection device. Active-power control was implemented by adjusting the inverter output via the device, and its effectiveness was validated through simulation studies. The results confirm that the proposed approach can achieve effective voltage regulation of distribution lines and enhance the hosting capacity of distributed generation systems.

https://doi.org/10.5370/KIEE.2025.74.11.1844

김승호(Seung-Ho Kim) ; 김현진(Hyeon-Jin Kim) ; 박상호(Sang-Ho Park) ; 신정훈(Jeong-Hoon Shin)

The increasing integration of renewable energy poses a significant threat to the voltage stability of regional power systems, such as in the Gwangju-Jeonnam province. This paper proposes a dynamic voltage stability assessment methodology applicable within a Local Renewable Management System (LRMS). The proposed methodology periodically calculates the 'maximum renewable energy hosting capacity' by integrating real-time grid data and conducting contingency-based simulations using DSA(Dynamic Security Assessment) Tools. A case study using actual data from the Gwangju-Jeonnam grid successfully identified the potential risk of voltage collapse on a day without renewable energy curtailment and quantified the stable hosting limit. This study demonstrates that the proposed methodology can provide grid operators with a quantitative tool for proactive decision-making, contributing to the stable operation of the power grid while maximizing the utilization of renewable energy.

https://doi.org/10.5370/KIEE.2025.74.11.1850

권구민(Gu-Min Kwon) ; 신정훈(Jeong-Hoon Shin) ; 권혁일(Hyuk-Il Kwon) ; 오승찬(Seung-Chan Oh) ; 구현근(Hyun-Keun Ku)

This paper proposes a comprehensive methodology for assessing the secure operating region of LCC(Line-commutated Converter) HVDC installations that are increasingly being deployed in the Korean power system. We define and specify criteria for four factors that must be considered in both planning and operation: Short Circuit Ratio (SCR), Fundamental-Frequency Temporary Overvoltage (FFTOV), Unit Interaction Factor (UIF), and overall power-system reliability. Using an AC network model interconnected with a 3-GW HVDC link, we evaluate the admissible operating range for each criterion under contingencies, and then synthesize the individual results to derive a common secure operating region. The criterion thresholds are set to SCR > 3, FFTOV < 1.35 pu, UIF < 0.1, and compliance with the national “Criteria for Maintaining Power System Reliability and Power Quality.” The proposed methodology provides practical guidance for both planning by supporting grid reinforcement decisions and operation by enabling the development of effective dispatch and operating strategies under diverse grid conditions.

https://doi.org/10.5370/KIEE.2025.74.11.1857

김현진(Hyeonjin Kim) ; 김승호(Seungho Kim) ; 박상호(Sangho Park) ; 신정훈(Jeonghoon Shin) ; 이종욱(Jong-UK Lee)

In this paper, a renewable energy flexible interconnection operation procedure and system were applied to demonstrate output curtailment in the main transformer distribution network of the substation in Jeju. The proposed system forecasts photovoltaic (PV) and wind generation, as well as load demand, on a day-ahead (D-1) basis at 15-minute intervals, and determines the curtailment requirements for each generator by calculating the hosting capacity of the transformer through net load and voltage stability assessments. On the operating day (D-day), curtailment commands are issued to renewable generators, and real-time monitoring is conducted to verify execution against the planned schedule. The field demonstration, carried out from May 2?3, 2024, during a period of frequent reverse power flow, successfully reduced renewable generation to maintain reverse flow within the hosting capacity limit. The results confirm that the proposed system can effectively implement forecast-based curtailment strategies in actual grid operation, contributing to both enhanced renewable hosting capacity and improved grid stability. This result provides a technical foundation for expanding the flexible interconnection approach to other renewable-concentrated regions in Korea.

https://doi.org/10.5370/KIEE.2025.74.11.1862

김나현(Na-Hyeon Kim) ; 정해일(Hae-Il Jeong) ; 배인수(In-Su Bae)

Transformers are essential components in power systems, and their reliability must be ensured through timely maintenance. Conventional inspection and maintenance practices often follow fixed schedules regardless of the transformer’s actual condition, which may result in unnecessary costs or delayed detection of potential failures. To address this issue, this study proposes an optimized maintenance strategy based on dissolved gas analysis (DGA) of transformer insulating oil, focusing on carbon monoxide (CO) and carbon dioxide (CO₂) concentrations as key indicators of insulation degradation. By analyzing inspection records and statistical data, four condition-based inspection cases are developed and compared with the existing periodic maintenance standards adopted by utilities such as KEPCO. The analysis evaluates inspection intervals, labor costs, and cost-saving potential while considering the effectiveness of detecting insulation deterioration. Results show that condition-based inspection using CO and CO₂ thresholds can reduce unnecessary inspections and achieve significant cost savings, while also contributing to transformer life extension and improved system reliability. This study demonstrates that incorporating DGA into inspection scheduling provides a more efficient and economical maintenance framework compared to conventional time-based approaches. The findings highlight the importance of adaptive maintenance strategies for enhancing asset management and ensuring stable power supply.

https://doi.org/10.5370/KIEE.2025.74.11.1868

김태환(Tae-Hwan Kim) ; 박중성(Jung-Sung Park) ; 오준석(Joon-Seok Oh) ; 고민식(Min-Sik KO) ; 김정웅(Jeong-Woong Kim) ; 김건호(Geon-Ho Kim) ; 남승우(Seung-Woo Nam) ; 황성욱(Sung-Wook Hwang)

We propose and field-test an ISO?DSO?VPP coordination scheme for distribution-level operation under a Total DSO assumption. The scheme links day-ahead prequalification (1-h resolution, up to three guidance?rebidding iterations) with real-time control (15-min operating interval with 1-min monitoring) so VPP bids and dispatch respect feeder limits (0.95?1.05 p.u., 10 MVA at 22.9 kV). We also position ESS-based non-wires alternatives (NWAs) to relieve overloads and defer upgrades while increasing hosting capacity. Field applications in Korea include (i) three feeders in Gwangju?Jeonnam validating constraint clearance via the prequalification?rebidding loop, and (ii) one feeder in Jeju where ESS-based NWAs over ten days achieved 0.2?1.5 MW peak reduction, indicating credible deferral potential. The results clarify the DSO’s operative role and show how LNBA/GNA evaluation can be aligned with market and distribution operations.

https://doi.org/10.5370/KIEE.2025.74.11.1875

양윤수(Yun-Su Yang) ; 허준혁(Jun-Hyeok Heo) ; 김대현(Dae-Hyeon Kim) ; 허진(Jin Hur)

With the expansion of high-voltage systems and the growing demand for electric motors, shaft voltage-induced bearing electrical erosion has emerged as a critical problem in the electric vehicle (EV) industry. Shaft voltage leads to increased dielectric breakdown of bearing lubricants and elevated vibration, which in turn raises the frequency of electrical discharges within bearings and can result in irreversible motor damage. This study analyzes the effects of changes in stator end winding length and rotor winding arrangement in a wound field synchronous motor (WFSM) on parasitic capacitance and shaft voltage characteristics. Variations in these winding configurations during the manufacturing process alter the parasitic capacitance inside the motor, thereby influencing the magnitude of shaft voltage. The effects of winding design on parasitic capacitance and shaft voltage were analyzed to support reliability improvements in EV motors.

https://doi.org/10.5370/KIEE.2025.74.11.1883

조채원(Chaewon Jo) ; 구희원(Heewon Koo) ; Li Liu(Li Liu) ; Zhaoyi Wang(Zhaoyi Wang) ; 이주(Ju Lee)

Since both the winding factor and machine period depend on the pole-slot combination, their selection has a significant impact on the electromagnetic characteristic of electrical machine, including cogging torque, torque ripple, and efficiency during machine design. In this paper, the electromagnetic characteristics of the axial flux permanent magnet synchronous motor are analyzed for the pole and slot combination which has the fractional slot concentrated winding. Four different pole-slot combinations are selected to compare the electromagnetic characteristics. The winding factor, which influences torque and torque ripple, and the least common multiple of the poles and slots number, which affects the cogging torque, are compared with four pole and slot combinations. Based on finite element analysis, the no-load and load characteristics are compared, and the favorable pole-slot combination is identified with respect to toruqe characteristics and efficiency.

https://doi.org/10.5370/KIEE.2025.74.11.1890

장준호(Jun-Ho Jang) ; 양준원(Jun-Won Yang) ; 반휘랑(Hwi-Rang Ban) ; 이수진(Soo-Jin Lee) ; 최연태(Yeon-Tae Choi) ; 김성원(Seong-Won Kim) ; 박준범(Jun-Beom Park) ; 김용주(Yong-Joo Kim) ; 신경훈(Kyung-Hun Shin) ; 최장영(Jang-Young Choi)

This paper proposes an improved Quasi-3D analysis method for rapid magnetic field prediction in axial flux permanent magnet motors. The proposed method accounts for the effects of the permanent magnet overhang structure. The conventional Quasi-3D approach simplifies analysis by radially segmenting the motor, evaluating each region with 2D finite element analysis, and integrating the results to predict overall performance. However, conventional Quasi-3D methods have limitations in accurately modeling permanent magnet overhang, which results in discrepancies in performance predictions. To resolve this issue, the proposed Quasi-3D approach employs an equivalent analytical model that adjusts the permanent magnet operating points. This adjustment ensures that the magnetic energy aligns accurately with experimental data in electromagnetic analyses. The validity of the proposed approach is confirmed via comparisons with experimental verification results, thus demonstrating the enhanced accuracy of the method in predicting the performance of axial flux permanent magnet motors with permanent magnet overhang structures.

https://doi.org/10.5370/KIEE.2025.74.11.1899

김수현(Su-Hyeon Kim) ; 구본관(Bon-Gwan Gu)

This paper proposes a Safe Torque Off (STO) technique for fault response in high-speed dynamometer systems. In such systems, the test motor and dynamo motor are mechanically coupled, and STO operation during a fault critically affects safety. When PWM is turned off, the inverter acts as a diode rectifier, and the motor’s back-EMF induces regenerative braking. This can cause overvoltage in the DC-link capacitor, risking damage to power devices. Assuming the absence of a Discharge Unit (DCU), which is a circuit that actively dissipates regenerative energy during emergency stops, we derive an energy-based equation to predict the capacitor voltage considering motor inertia, speed, and load torque. Using this result, a criterion is proposed for determining safe STO regions under emergency stop conditions. Simulation and experimental results verify that the predicted voltage aligns well with measured values, confirming the algorithm’s effectiveness. The proposed method prevents capacitor failure and fault propagation, enhancing system reliability. Although the algorithm depends on motor and system parameters, it provides a mathematically grounded, safe fault response strategy for high-performance drives.

https://doi.org/10.5370/KIEE.2025.74.11.1908

김종겸(Jong-Gyeum Kim)

This paper is a study to analyze the effect of switching timing on motor starting characteristics in the reactor starting method of a high-voltage induction motor and derive the optimal switching point. Reactor starting is a method to reduce the impact on the power system by reducing the starting current of the motor, and if the switching timing is inappropriate, problems such as torque reduction, starting failure, or transient current may occur. In this study, based on the actual starting data of a high-voltage induction motor, the waveforms of current, voltage, speed, torque, etc. before and after reactor switching were analyzed, and the starting process was reproduced and compared through a simulation model using EMTP. Based on the experimental and simulation results, the effect of switching timing on the starting stability and efficiency of the motor was quantitatively analyzed. In conclusion, this study provides a technical basis for simultaneously satisfying the reliability of high-voltage motor starting and system protection by presenting the optimal switching point in the reactor starting method.

https://doi.org/10.5370/KIEE.2025.74.11.1914

남주현(Ju Hyeon Nam) ; 정강률(Gang-Youl Jeong)

This paper proposes a high-efficiency dual-transformer resonant converter with a wide input voltage range. High-efficiency is achieved using an LC or LLC series resonant circuit formed by the equivalent series resonant inductance from the dual-transformer and a resonant capacitor. The dual-transformer consists of two center-tapped transformers with primary windings in series and secondary windings in parallel. This setup increases effective input resistance, reduces secondary winding loss, and eases handling of high-voltage DC input. Secondary windings are wound in opposite orders on each transformer core to ensure coordinated operation and equalize effective resonant inductance in each mode, resulting in equal secondary current magnitudes. The paper presents the operating principles by mode, describes dual-transformer design and effects, and validates performance through experiments using a prototype designed based on these principles and the fundamental harmonic approximation.

https://doi.org/10.5370/KIEE.2025.74.11.1926

김차니(Chani Kim) ; 설수진(Sujin Seol) ; 김병우(Byeong-Woo Kim)

With the increasing demand for lithium-ion batteries, accurate estimation of battery SOH has become essential for ensuring operational safety and system reliability. However, SOH prediction based on a single type of sensor data often suffers from limited accuracy and insufficient robustness. To address this limitation, it is necessary to incorporate diverse sensor information that reflects the comprehensive state of the battery. In this study, we propose a Multi-modal Fusion (MMF) model that effectively leverages multiple types of sensor data related to battery behavior. The proposed model integrates heterogeneous modalities in a complementary manner, and experimental results demonstrate that this MMF model approach significantly improves prediction accuracy compared to models using individual data types.

https://doi.org/10.5370/KIEE.2025.74.11.1935

이민규(Min-Gyu Lee) ; 문철우(Chulwoo Moon) ; 이상윤(Sangyoon Lee)

This paper proposes an optimal power management system for electric vehicle charging station aim at maximizing profit with the consideration of uncertainties of electricity price, electric vehicle (EV) load, and photovoltaic (PV) generation. To address the limitations of conventional optimization methods such as stochastic or robust optimization, we adopt a data-driven distributionally robust optimization (DRO) framework. In addition, we propose a distributionally robust chance-constrained programming (DRCCP) approach to address the uncertainty-related constraints of EV loads and PV generation. To render the proposed DRO-based model as a finite-dimensional convex problem, we present a tractable reformulation for proposed problem. Simulation investigations show that proposed DRO-based power management system achieves the profit increase compared to conventional approaches, while effectively managing multiple uncertainties.

https://doi.org/10.5370/KIEE.2025.74.11.1944

노재구(Jae-Koo Noh) ; 김영일(Young-Il Kim) ; 신진호(Jin-Ho Shin) ; 이효철(Hyo-Chul Lee) ; 이종욱(Jong-Uk Lee)

As the share of solar photovoltaic (PV) generation increases within the power system, visibility of the grid has declined, leading to distortions in actual electricity demand. This paper proposes a method for estimating solar PV capacity by reconstructing total electricity demand based on its temperature sensitivity. By incrementally adding estimated solar generation to the market load, the method reconstructing gross electricity demand, and identifies the point at which temperature sensitivity is maximized as the basis for estimating total installed PV capacity. The proposed approach was applied to 2021 data to estimate solar PV capacity by transaction type, providing a quantitative basis for assessing the scale of unmetered behind-the-meter (BTM) resources. Additionally, Comparative analysis shows that including more comprehensive PV data significantly improves demand-reconstruction accuracy. This method offers a practical solution for improving the visibility of solar resources in the power grid and enhancing the accuracy of demand forecasting.

https://doi.org/10.5370/KIEE.2025.74.11.1950

부준석(Junseok Boo) ; 홍상기(Sang Gi Hong) ; 전지훈(Ji Hun Jeon) ; 신동범(Dong-Beom Shin) ; 배명남(Myung Nam Bae) ; 김은주(Eun Joo Kim) ; 이강복(Kang Bok Lee)

This paper proposes a disturbance observer-based integral sliding mode control for bidirectional vehicle platooning under uncertain acceleration and both matched and mismatched disturbances. The platoon dynamics explicitly incorporate these disturbances, and a modified constant time-headway policy is adopted to define the spacing error without relying on acceleration measurements, thereby mitigating the effects of initial spacing and velocity errors. Based on this, coupled integral sliding mode dynamics are derived, and a finite-time stable disturbance observer-based bidirectional platoon controller is designed to compensate for lumped uncertainties, enhancing overall system robustness. The proposed controller is mathematically proven to guarantee both stability and string stability, and its performance is further validated through numerical simulations.

https://doi.org/10.5370/KIEE.2025.74.11.1958

박종희(Jong-Hee Park) ; 한석희(Seok-Hui Han) ; 윤성현(Sung-Hyeon Yoon) ; 김정효(Jeong-Hyo Kim) ; 이형철(Hyeong-Cheol Lee)

With recent advancements in electric vehicle technology, the utilization of Steer-By-Wire (SBW) systems is increasing. However, SBW systems pose a critical issue: the complete loss of steering function in the event of a motor system failure due to the absence of mechanical linkages. This study proposes a Model Predictive Control (MPC)-based differential braking control system for safe roadside entry and stopping of a vehicle during an SBW steering motor failure. The proposed system consists of a path planner utilizing a 5th-order Bezier curve and a vehicle model-based MPC controller, where the upper-level controller calculates the required yaw moment and the lower-level controller distributes brake torque to each wheel. The effectiveness of the proposed algorithm was validated through CarSim simulations, confirming that stable vehicle control is possible even in steering system failure situations. This research is expected to enhance the fault tolerance of SBW systems and contribute to ensuring the safety of electric vehicles.

https://doi.org/10.5370/KIEE.2025.74.11.1965

김진훈(Jin-Hoon Kimark)

The Lyapunov-Krasovsky function(LKF) approach has been widely used to obtain delay-dependent stability results for linear systems with time-varying delays. This approach consists in selecting an LKF and deriving linear matrix inequality (LMI) conditions that guarantee the negativity of its time derivative. It is reasonable to expect that using different LKFs for different delay intervals can lead to improved results. Recently, a few stability results utilizing this idea have been reported. This paper proposes a new method for selecting an LKF based on this approach and presents an LMI condition that guarantees system stability. Finally, the effectiveness of the proposed results is demonstrated through two well-known examples.

https://doi.org/10.5370/KIEE.2025.74.11.1972

조항준(Hangjun Jo) ; 김서영(Seoyeong Kim) ; 정대원(Daewon Jeong) ; 오희빈(Heebin Oh) ; 정경용(Kyungyong Chungark)

In this paper, we propose the multilingual Chatbot-based OTC drugs information summary model using retrieval-augumented generation. In this paper, we propose the multilingual Chatbot-based OTC drugs information summary model using retrieval-augumented generation. In this paper, we propose the multilingual Chatbot-based OTC drugs information summary model using retrieval-augumented generation. In this paper, we propose the multilingual Chatbot-based OTC drugs information summary model using retrieval-augumented generation. The proposed method use to provide accurate answers to OTC Drugs questions to users using OpenAI's GPT 3.5 model. The GPT 3.5 model, which was tuned prompts to provide answers based on official data, was used. In addition, the model was trained to answer with a consistent tone through fine tuning. And the research was conducted to provide real-time document-based answers through RAG-type research. This paper explains the design process of the chatbot system based on OpenAI's GPT 3.5 model and proposes a method of providing over-the-counter information more accurately and effectively in various languages. This study is expected to increase the reliability and accessibility of providing over-the-counter information to multinational users staying in Korea. In addition, it is expected to be able to provide answers based on various real-time information.

https://doi.org/10.5370/KIEE.2025.74.11.1979

강경훈(Kyung-Hoon Kang) ; 박지선(JI-Sun Park) ; 최호림(Ho-Lim Choiark)

In this paper, a PID controller is designed for improved altitude control of a quadrotor system by utilizing two gain scaling factors and a switching technique. First, the effects of the gain-scaling factors on overshoot and steady-state error are analyzed. Then, a switching technique is applied to select one of the two gain scaling factors depending on the altitude. Of the two gain scaling factors, one is tuned to achieve low overshoot mainly for transient response, while the other is tuned for robustness against disturbances and to minimize steady-state error. The performance of our proposed method is experimentally highlighted via the comparison with the conventional PID controller by using an AR.Drone platform. The results demonstrate that the proposed method achieves improved performance over the conventional PID, -PID controller.

https://doi.org/10.5370/KIEE.2025.74.11.1989

황익호(Ick-Ho Whang) ; 강지훈(Jihoon Kang) ; 안지훈(Ji-Hoon An) ; 조형준(Hyeong-Jun Cho) ; 박상규(Sang-Gyu Park) ; 나원상(Won-Sang Ra)

Modern anti-ship missiles often employ low-altitude sea-skimming tactics to improve their survivability against naval defense systems. However, radar returns from such low-flying missiles are notorious for exhibiting severe fluctuations due to the multipath effect. This phenomenon significantly impairs radar systems' ability to accurately measure angles - especially in the elevation channel - resulting in critically poor performance. These degraded pitch measurements pose a substantial challenge for ship defense systems attempting to counter sea-skimming threats. In this paper, we investigate the multipath effect and propose a simplified model for characterizing its impact on radar measurements. Furthermore, by constraining the positive height condition to pitch radar measurements, we introduce novel design methodologies for height-tracking filters tailored to sea-skimming missile scenarios. Simulation studies in various conditions demonstrate that the proposed filters can reliably track targets, even under conditions where pitch measurements are heavily degraded by multipath interference.

https://doi.org/10.5370/KIEE.2025.74.11.1998

이상훈(Sang-Hun Lee) ; 김경호(Kyung-Ho Kimark)

This study tackles the data scarcity and motion artifact problems of wearable APG signals by pairing wavelet?based quality screening with generative augmentation. Clean 66?sample APG cycles were extracted, Time?GAN, GAN, and VAE. A db4, 4?level Wavelet Packet Transform filtered out low?quality samples using LF ratio?≥?0.60, HF diff?≤?0.05, phase shift?≤?10°. Four training sets (Real?Only plus three augmented variants) were tested on 1D?CNN, LSTM, and LightGBM with 5?fold cross?validation. Time?GAN data pushed LightGBM Accuracy/F1/AUC to?1.00 and showed near?perfect overlap with real signals in PCA space, whereas VAE was slightly lower and GAN lagged due to mode collapse. Results confirm that wavelet?screened Time?GAN augmentation markedly improves APG?based cardiovascular classification.

https://doi.org/10.5370/KIEE.2025.74.11.2004

정성수(Seong-Soo Jeong) ; 김철환(Chul-Hwan Kim)

This paper presents an operational strategy for a Photovoltaic(PV)-integrated hybrid system combining a Battery Energy Storage System(BESS) and an Uninterruptible Power Supply(UPS). The proposed Hybrid UPS?ESS(HUE) enables UPS to supply backup power during grid outages, while ESS improves efficiency and flexibility under normal conditions. PV generation reduces grid dependency and supplies charging power to the ESS. To manage PV and load forecast uncertainty, a Long Short-Term Memory(LSTM) network is used for short-term prediction and integrated into a heuristic control that adjusts the ESS’s lower State-of-Charge(SOC) bound, traditionally reserved for UPS use. This integration enhances ESS utilization while ensuring UPS reliability. Simulation results demonstrate that the proposed strategy enhances UPS usage rate, ESS availability, SOC stability, and grid power smoothing compared to rule-based methods.

https://doi.org/10.5370/KIEE.2025.74.11.2012

서형빈(Hyoungbin Seo) ; 김우용(Wooyong Kim)

This paper presents a cost-effective operation strategy for integrating photovoltaic (PV) generation with an energy storage system (ESS). The approach interprets future solar Irradiance forecasts using fuzzy logic to dynamically set the target state of charge (SOC) of the battery. By adjusting the SOC target according to predicted sunlight, the ESS can be proactively managed to prevent overcharging and over-discharging. Unlike artificial intelligence methods, the fuzzy membership functions provide a clear, rule-based connection between irradiance predictions and SOC targets, ensuring both transparency and ease of implementation. A constrained optimization problem is further formulated with battery current as the decision variable to minimize electricity costs and power losses, yielding an optimal current profile. Simulation results show that the proposed method lowers electricity expenses compared with conventional peak-shaving strategies and reduces deep cycling, thereby extending battery life.

https://doi.org/10.5370/KIEE.2025.74.11.2019

남준혁(Jun-Hyuk Nam) ; 조동일(Dong-Il Cho) ; 조윤진(Yun-Jin Cho) ; 박성준(Seong-Jun Park) ; 문원식(Won-Sik Moon)

This study investigates the impact of electric vehicle(EV) charging on voltage margin in distribution systems with high photovoltaic(PV) penetration in tourist regions. Using Jeju Island as a case study, the Voltage Margin Evaluation Index(VMEI) is applied to assess voltage stability under different charging scenarios. Results show that daytime EV charging in tourist areas naturally coincides with PV generation, mitigating overvoltage by absorbing surplus output, with greater improvements observed in feeders with higher PV penetration. These findings highlight the potential of EV charging as a passive voltage stabilization resource, offering practical insights for charging infrastructure planning and grid operation in high PV penetration tourist regions.

https://doi.org/10.5370/KIEE.2025.74.11.2027

송국호(Kukho Song) ; 황성연(Seongyean Hwang) ; 윤종천(Jongcheon Yoon) ; 윤석철(Seok-chul Yun) ; 김정한(Jeoung Han Kim) ; 최균석(Kyunsuk choi)

In this study, for the production of an integrated head part measuring 500 mm for a 35-ton engine combustor, we analyzed cases of failures between manufacturing processes. These failures included secondary design issues such as support design, as well as problems caused by heat accumulation in areas with a large surface area, which is characteristic of large parts. Through this analysis, we identified the causes of issues arising between processes when applying large-area technology to the production of large components such as combustors. Additionally, we conducted research to optimize the manufacturing process of large parts and enhance process reliability by analyzing the causes of output failures that occur during the production of 500 mm-class large metal components.