http://doi.org/10.5207/JIEIE.2024.38.6.403

Minha Kim ; Sunghwan Bae ; Youngduk Kim

In this paper, we tried the design of an economical system to control various LED lightings using Arduino MKR WiFi 1010 and RS-485 based Modbus protocol. The key features of the lighting system based on a timer were overall lighting ON/OFF, user-adjustable dimming, and sensor-integrated automatic dimming. The master device read data once from sensors, which were installed on each floor of the module composed of multi-layered beds, and uploaded this data to a server via MQTT. It compared the data to the pre-configured target sensor values by user and the master processed the data into dimming control values and wrote the values to the corresponding holding register in slave devices. The lighting system used in the test consisted of LED lightings(1200mm bar-type Quantum-dot lighting) with SMPS supporting 1-10V dimming, a master board, sensor boards, and LED control boards. All components were self-developed. The system was installed for pilot testing in a 2-layer system in a closed green house. Occasional issues were observed, which can be resolved, such as relay control failures and sporadic communication errors. This system configuration was expected to provide precise automatic light control, thereby improving crop productivity and quality.

http://doi.org/10.5207/JIEIE.2024.38.6.412

Jeong-Yeon Han ; An-Seop Choi

The impact of luminaire retrofits on user satisfaction was evaluated in a small fitness center focused on personal training (PT). The average illuminance before the luminaire retrofit was measured at 135lx, which did not meet KS A 3011 standards for fitness center illuminance(150?300lx), resulting in insufficient brightness, shadows, and glare that negatively impacted the exercise environment. To address these issues, LED linear pendant luminaire was installed to provide more uniform light distribution, and color-adjustable LEDs were added to promote recovery and reduce stress during rest periods. Lighting simulations using Relux software predicted an increase in illuminance to 685lx, meeting the European standard for fitness centers (EN 12193). Post-luminaire retrofit measurements taken at 25 locations showed an average illuminance of 846lx, closely matching the simulation’s predictions. A survey of 70 participants aged 20 to 60 revealed improvements in positivity, spatial awareness, safety, and cognitive performance. However, some participants reported increased glare. The contrast between the luminaire and the black ceiling, particularly over lying equipment such as the bench press, was believed to have intensified the lighting effect, making it feel overly harsh. Optimized luminaire has been shown to significantly enhance the exercise experience, helping users feel safer and more motivated.

http://doi.org/10.5207/JIEIE.2024.38.6.419

Sang-Yoo Kim ; Jae-Young Joo ; Sang-Bin Song

This study focuses on optimizing the control system of automotive matrix headlamps to enhance nighttime driver visibility while minimizing glare for other road users, including oncoming drivers and pedestrians. The research emphasizes the importance of precise and responsive high-resolution beam management to improve visibility and road safety. Using a developed simulator, we analyzed the impact of system delays?such as image processing, control processing, and communication delays?on headlamp performance. Strategies for optimizing beam control margins were proposed to maximize visibility and reduce glare, even with system speed constraints. Leveraging advancements in camera technology, the system enables adaptive beam adjustments based on detected objects, enhancing control accuracy. The proposed system’s effectiveness was validated through simulations and will be further tested using Hardware-in-the-Loop Simulation (HILS) for real-world applications.

http://doi.org/10.5207/JIEIE.2024.38.6.427

Dae-Sung Jung

This paper is designed to reduce cogging torque by applying a 3D finite element method. Step skew was applied to the rotor to reduce cogging torque. Cogging torque can be removed in theory, but not in practice. Even though design can reduce cogging torque, cogging torque exists as there are many harmonic components in the manufacturing process and the cogging torque waveform. Additionally, the waveform and magnitude of cogging torque can be altered by iron loss. Therefore, in this paper, the optimum number of step skew and the step angle are proposed to reduce cogging torque by analyzing the harmonic cogging torque waveform. In addition, the analysis result of cogging torque and the measurement result were analyzed. The cautions about the measurement of cogging torque have been studied. Finally, the validity of the paper was verified through evaluation.

http://doi.org/10.5207/JIEIE.2024.38.6.433

Seung-Ho Song

This paper describes the construction of test facilities for solid-state transformers for distributed power high-speed rail vehicles. The specifications of the solid-state transformer have an input voltage of 25kV AC and a rating of 4.2MW. The transformer operates at high frequencies, enabling designs that are smaller and lighter than existing low-frequency transformers of tens of Hz. The solid-state transformer has 14 modules connected in series, and each module consists of 3 cells. The verification process involves by increasing capacity and voltage, starting from individual cell tests, followed by module tests, series configuration tests, and system-level tests. Test facilities require not only the application of low voltages of hundreds of V to high voltages of up to 29kV, but also loads and power facilities of hundreds of kW to several MW. This paper presents a test plan and facility construction plan for a MW range solid-state transformer.

http://doi.org/10.5207/JIEIE.2024.38.6.438

Munseok Chang ; Sungyu Hwang ; Sungwoo Bae

Electric vehicle (EV) charging infrastructure is crucial for sustainable transportation electrification and achieving carbon neutrality. As the expansion of charging infrastructure accelerates to meet growing EV user demand, a comprehensive evaluation of utilization is required from various perspectives. This study presents an approach to evaluate utilization indicators that reflect the operational status of EV charging infrastructure and establish a classification framework. As a first step, the scope of EV charging infrastructure is defined, and both domestic and international market trends, along with national support policies, are analyzed. The study highlights that the significance of utilization evaluation varies depending on stakeholders’ interests. A classification system is developed based on charging variables, time intervals, and application cases. Utilization indicators are categorized by quantity, charging demand, and charging time, while evaluations are conducted over short, medium, and long-term intervals. Additionally, application cases are classified into pattern analysis, utilization maximization, impact factor exploration, and operational optimization of charging infrastructure.

http://doi.org/10.5207/JIEIE.2024.38.6.445

Tae-Soon Park ; Yeon-Ho Choi ; Kyoung-Min Kwon ; Jae-Jung Yun

Battery aging leads to performance degradation, which affects the safety and lifespan of the battery. Therefore, it is very important to analyze battery aging. This paper performs Incremental Capacity Analysis (ICA) to analyze the degradation mechanisms (DM) of different lithium-ion batteries with varying cathode materials. ICA is utilized to analyze changes in peak height and area under the IC curve, which interprets key degradation modes such as Loss of Lithium Inventory (LLI) and Loss of Active Material (LAM). As a result of the experiment, the LCO battery lost less Lithium Inventory than the NCM batteries. In addition, it was analyzed that NCM battery is more resistant to aging than NCMA battery.

http://doi.org/10.5207/JIEIE.2024.38.6.452

Munseok Chang ; Sungyu Hwang ; Sungwoo Bae

Digital twin technology creates models that reflect reality in a virtual environment, enabling analysis of both the physical and virtual worlds. It is a technology that allows for the understanding of past and present system operations and the prediction of future states. This study presents a method for modeling four types of facilities using both physics-based and data-driven modeling techniques through digital twins. First, for the battery energy storage system, a physics-based equivalent circuit modeling method was applied to simulate the chemical reactions and electrical relationships of the battery cells through internal parameters. This approach was then expanded to the battery pack level to evaluate the accuracy of the digital twin about the terminal voltage. For the electrolyzers, a physics-based equivalent circuit modeling method was initially used to reflect the electrochemical and thermodynamic characteristics of the electrolysis mechanism. This approach was then expanded from the cell level to the system level, and a data-driven deep neural network model was additionally developed to evaluate the accuracy of the digital twin regarding output voltage. The hydrogen fueling facility was modeled using a physics-based gas equation of state that considers the energy and enthalpy of hydrogen gas. Additionally, a data-driven random forest model was employed to determine the accuracy regarding the internal pressure of the hydrogen tank. Lastly, the electric vehicle charging facility was modeled using a physics-based equivalent circuit model to simulate the nonlinear charging profile, and a data-driven support vector machine model was built to estimate charging demand patterns. The performance of the digital twin modeling for the four facilities was evaluated based on the normalized mean absolute error metric, yielding results of 1.26%, 2.50%, 2.93%, and 5.47%, demonstrating highly favorable outcomes.

http://doi.org/10.5207/JIEIE.2024.38.6.458

Ju-Hyeon Jeon ; Do-Yun Kim

The LDC plasma power supply for cleaning applications experiences significant losses depending on the characteristics of the plasma load. The output is categorized into reactive and active power based on the capacitance component of the multi-jet load, which results in fluctuations in plasma density according to the load state. This issue can greatly affect the cleaning efficiency of LCDs, necessitating a high-voltage plasma power supply that can vary its output characteristics based on load conditions. This paper describes the design methodology of a power supply suitable for multi-jet plasma loads, capable of supplying a constant power while varying the output frequency and duty cycle according to the load state. Additionally, a multi-jet plasma system is constructed, and its validity is verified through authentication experiments and multi-jet plasma load coupling experiments.

http://doi.org/10.5207/JIEIE.2024.38.6.465

Yechan Kim ; Minkyung Jeong ; Bonhyuk Ku ; Hyoungku Kang

The purpose of this paper is to propose a strategy for assigning condition codes in the health indexing of GIS (Gas-Insulated Switchgear), a critical component in ensuring the reliable operation of power systems. Traditional asset management strategies, which rely on estimated lifespans, often lead to inefficiencies, especially in determining the optimal timing for maintenance or replacement. To overcome these challenges, CBRM (Condition-Based Risk Management) has gained prominence as a solution, using health and criticality indices to optimize decisions based on the actual condition of assets. This study aims to develop a health indexing framework for GIS that accurately reflects the condition of its components and subsystems. The proposed framework introduces a structured methodology for assigning condition codes by combining a logarithmic scale with ‘summation’ and ‘worst case’ computation, computation. This effectively reduces the masking effect that is often encountered in approaches that combine a linear scale with weighted summation. Additionally, a combination of worst case and summation approaches is used in calculating condition codes to ensure that the condition of each component is appropriately represented in the overall health index of the GIS. By addressing the probability of failure based on actual conditions, this framework allows for timely interventions and enhances the operational efficiency of assets. Ultimately, the proposed strategy contributes to the long-term reliability of power infrastructure and offers valuable insights for improving risk management practices.

http://doi.org/10.5207/JIEIE.2024.38.6.474

Hyeongjun Kim ; Young-Seob Moon ; Se-Hee Lee

High energy arcing faults (HEAF) are becoming more common in aged electrical equipment as nuclear power plants age. The fire and potential damage caused by HEAF are often not considered in existing nuclear safety regulations, so further research is needed. The international joint study from the Nuclear Energy Agency (NEA) in the Organization for Economic Co-operation and Development (OECD) has been conducting the HEAF experiments to investigate HEAF phenomena for electrical systems in nuclear power plants. To support effective nuclear safety regulation, a comprehensive database is essential for systematically categorizing and organizing the complex and invaluable HEAF experimental data. Therefore, we analyzed the HEAF experimental reports to identify key attributes and proposed an effective framework for HEAF database. The HEAF Project Phase-2 report suggests that HEAF experimental data have unique characteristics that differ from typical data, highlighting the need for a specialized database. The proposed HEAF experimental database, implemented with Obsidian software, features a four-layer structure for independent data management and provides intuitive linkages among experimental data, enabling users to analyze and query HEAF results without deep database knowledge.

http://doi.org/10.5207/JIEIE.2024.38.6.482

Jeong-Heum Park

In this study, various modeling techniques for lithium-ion batteries were reviewed, and a combined model method was selected as a technique suitable for mobility applications. After performing the simulation using this, the effectiveness of the modeling was examined by comparing the actual measured value with the calculated value. First, a pulse-controlled charging and discharging system was implemented to obtain a measured value, and through this, the actual value of the cell voltage according to the charging state was obtained and compared with the simulation value. As a result, the experimental and calculated values matched well in the entire battery cell usage section except for the cell voltage of 3.4V or less, which is turned off when the device is used. In addition, as a result of calculating the battery efficiency, the experimental value is 89.84% and the calculated value is 89.99%, which are very similar, so it can be said that the results of the combined model reflect the actual value well.

http://doi.org/10.5207/JIEIE.2024.38.6.488

Ki-Du Kim ; Ji-Su Ryu ; Young-Soo Kim

Recently, due to industrial development and economic growth, the use of power conversion devices has increased rapidly, and while this has led to the development of the power electronics industry as semiconductor devices have become smaller and more high-performance, it has also caused the problem of deteriorating power quality. In order to establish and manage effective measures for power quality problems, it is necessary to identify trends in the occurrence of voltage quality problems within the system. If it can predict the tendency of voltage quality problems at the sensitive load stage, it can also evaluate the damage and impact on the sensitive load, and based on this, it is possible to establish load-customized measures. In this paper, we developed a PQMS (Power Quality Management System) for application to a 1,500kVA unit modular offline uninterruptible power supply and verified its performance.

http://doi.org/10.5207/JIEIE.2024.38.6.495

Junyoung Park ; Jaesang Kim ; Hyoungku Kang

In high-temperature superconducting (HTS) coils, maximizing current density and achieving high magnetic fields often relies on no-insulation (NI) winding techniques. While this approach is beneficial for compact coil design and magnetic field stability, it can lead to magnetic field charging delays due to the absence of insulation between turns, which allows unwanted currents to form and interfere with magnetic field performance. This study aims to mitigate such delays by investigating the turn-to-turn contact resistance characteristics when using metal insulators between coil turns, focusing specifically on mesh structures as controllable insulating layers. Experiments were conducted under liquid nitrogen conditions, simulating the superconducting environment, where we measured contact resistance across different mesg and pressures to understand the relationship between these variables and their effect on current distribution between coil turns. The results show that the contact resistance increases with the mesh count, reaching a peak at 300 mesh STS 304, after which the mesh density becomes too fine and the contact resistance decreases. Similarly, increasing applied pressure significantly reduced contact resistance, with the effect becoming pronounced at pressures above 15 MPa due to increased a-spot connections between surfaces. These findings offer insights into optimizing HTS coil performance for applications requiring high-speed charging and discharging.

http://doi.org/10.5207/JIEIE.2024.38.6.501

Chang-Hwan Ahn

This paper proposes a detachable surge counter designed for surge protective devices (SPDs) used in communication and signaling networks. Typically, lightning generates high currents ranging from several kA to hundreds of kA, which can induce excessive overvoltage in communication and signaling networks due to electromagnetic coupling or an increase in ground potential. Surge protective devices are used to prevent such occurrences. The proposed surge counter is designed based on international standards, with the counting threshold current carefully set, and it adopts a non-powered design for ease of application in real environments. Additionally, I combined the surge protection device with the proposed surge counter and applied induced lightning currents of 1-5 kA to verify the counting capability. The surge counter proposed in this paper is expected to be useful for the maintenance of SPDs in communication and signaling networks.

http://doi.org/10.5207/JIEIE.2024.38.6.506

Du-San An ; Sang-Taek Lee

The regulations to reduce air pollutants from shipping industry have been strengthened by international organization such as IMO(International maritime organization). In response to these regulations, various efforts are being made to realize eco-friendly fuel and electric propulsion system. In this study, electric propulsion system based on liquid hydrogen fuel cell and battery was focused on and P-HILS was applied to analyze performance of propulsion system. P-HILS in this study used power devices supplying scaled-down power instead of power amplifier and simulation was conducted based on time series data of real tug boat. From the simulation result, the performance of propulsion system based on liquid hydrogen fuel cell and conformity between simulation model and power device are confirmed.

http://doi.org/10.5207/JIEIE.2024.38.6.512

Eun-Hyeok Choi

Despite extensive research and practical applications in fault prevention diagnostics for power facilities, issues arising from environmental factors and subjective judgment errors persist. Particularly, the diagnosis of distribution-level facilities employs multiple methods, revealing limitations in terms of cost-effectiveness and reliability. Power facilities, operating under high-voltage and high-current conditions, are prone to degradation. To address these challenges, this study proposes a diagnostic sensor that measures electromagnetic waves emitted during partial discharge (PD). This paper presents the design of a high-sensitivity, reliable sensor. to minimize environmental influences and accurately detect PD signals for early diagnosis of insulation defects. The proposed cone-shaped sensor adopts a triangular short-circuit plate structure, achieving compactness and cost-efficiency while maintaining stable performance under various environmental conditions. Simulation analysis of reflection loss characteristics confirms that this sensor can serve as a diagnostic tool that meets the reliability and cost-efficiency requirements for power facilities.