https://doi.org/10.5370/KIEE.2024.73.5.757

오재신;조영상

While the best advantage of Energy Efficiency Resource Standard(EERS) is that energy suppliers can choose the most optimal energy saving method, the Korean government is using EERS to achieve energy welfare and economic stimulation policies. To analyze the effect of government policies on EERS, we used energy efficiency potential estimation, integer programming, and California Standard Practice Manual on the 2023 EERS plan, which contains thirty-one energy efficiency measures, target savings of 1,151GWh, and costs of KRW 86.2 billion. The results of the analysis indicate that the current energy efficiency measures can hardly achieve the 2031 savings target. Moreover, we discovered that the addition of new program reflecting government policy leads to an increase of costs. Therefore, developing new energy efficiency measures with significant savings potential and the cost recovery mechanisms for the increased costs is needed. These findings will contribute to the optimal operation of EERS.

https://doi.org/10.5370/KIEE.2024.73.5.766

김경환;조승민;송경빈

Electric power sales forecasting is important from various perspectives, including the nation, power producers, and sellers. At the national level, it serves as foundational information for electricity supply efficiency, energy policy establishment, and integration of renewable energy. Power producers utilize it for optimal operation and planning of power plants, and decisions on power plant expansion and investment. Sellers can use it for monthly energy balance evaluation, operational efficiency improvement, and financial analysis. In this paper, we analyze factors that affect electric power sales to predict medium and long-term electricity sales volume, and based on this, input variables that have a high correlation with monthly electricity sales volume are selected. Then, the LSTM-based deep neural network model and XGBoost model are learned using the selected data. We construct an ensemble model by combining the monthly forecasts of each model using a voting method and present an algorithm to predict electricity sales for the next 24 months. The proposed ensemble model showed improved performance over the prediction model using a single technique.

https://doi.org/10.5370/KIEE.2024.73.5.773

이예빈;김지명;이민행;노성은;김세진;노대석

Recently, fire accidents in ESS installed for various applications have been occurred constantly and particularly those of long time operated ESS have been increased. Accordingly, researches are actively conducted on risk factor evaluations considering safety standards in ESS, and operation environments and applications of ESS are evaluated as major causes of fires and potential battery safety. Therefore, this paper proposes a risk priority number evaluation method composed of severity, occurrence and detection degrees, to estimate the safety level of ESS considering operation environments and applications. Where, the severity degree is quantitatively calculated by fault cases impact of applications, magnitude of fault current and building type of ESS, and the occurrence is determined by accident rates, operation environments and degradation rates, and also the detection is estimated with engineering technology of safety devices and battery capacity. This paper also performs the modeling of the fault analysis in ESS, which is composed of distribution system, customer load, fault devices and ESS in order to evaluate fault cases based on ESS applications. From the simulation results based on the proposed safety evaluation method, it is confirmed that frequency regulation and renewable energy applications in ESS mainly installed in mountain and coast areas is adversely affected by environment factors such as dust and humidity, and detailed measures related with continuous monitoring for operation environments are strongly required to ensure the safety in ESS.

https://doi.org/10.5370/KIEE.2024.73.5.784

김용태;구본관;임종경;김래영

This paper introduces a voltage angle controlled Space Vector Modulation (SVM) strategy for Brushless DC(BLDC) motor operation. The conventional 6-step control method for BLDC motors encounters limitations as it can only utilize half of the inverter DC link voltage(Vdc/2). SVM control is implemented to overcome inverter voltage utilization. The voltage angle controller is mainly used in flux-weaking control and has the advantage of having only one current controller. In this paper, voltage angle control is applied in the constant torque region, and the closed-loop transfer function of voltage-angle controller is analyzed according to the response of gain, speed, and load. Bode plots are used for this analysis, leading to the identification of the gain value that effectively suppresses resonance. Furthermore, the study addresses speed control by adjusting the voltage magnitude, and the proposed method is validated through simulation and experimental results.

https://doi.org/10.5370/KIEE.2024.73.5.793

김진출;박하민;이 주;박진홍;임태욱;이재범

The introduction of high-voltage battery vehicles and the necessity of 400 kW-capacity EV ultra-fast-charging systems emphasize the requirement for DC-DC converters with wide output voltage ranges and high output capabilities Previously, 10 kW DC-DC converters were parallelly expanded to meet fast charging demands, but for 400 kW chargers, this approach necessitates excessive modules, increasing maintenance and complexity in system configuration and control. This paper analyzed DC-DC converter topologies, to establish an optimized design for DC-connected fast charging specifications. It proposes a topology that addresses the shortcomings of existing ones, designed to operate differently secondary side configuration of the converter for varying battery charging voltages. The proposed 50 kW DC-DC converter, when expanded for fast charging, is expected to offer substantial advantages in maintenance and system configuration

https://doi.org/10.5370/KIEE.2024.73.5.807

이지호;강경수;박지환;박찬진;이수연

In this paper, we analyze the short-term degradation characteristics of low-temperature polycrystalline silicon (LTPS) thin-film transistor (TFT) to analyze the origin of short-term image sticking (STIS) in the mobile display. The STIS effect is highly relevant to the change in electrical characteristics of driving transistor of the pixel circuit. We mainly focus on the subthreshold swing (SS) variation, as the pixel circuits can internally compensate for the variation in threshold voltage. To examine the short-term degradation, each voltage and temperature stress corresponding to white and black grayscales are applied to the LTPS TFT for 10 minutes. We found that these stress conditions induce SS degradation of the LTPS TFT. This degradation can cause current variation of driving transistor, resulting in non-uniform luminance. Thus, the short-term SS degradation is strongly related to the origin of STIS effect.

https://doi.org/10.5370/KIEE.2024.73.5.811

박정호;임종식;한상민;안달;이길영

This paper describes the design of microwave low pass filters (LPF) using a symmetrical T-shaped defected microstrip structure (DMS). The equivalent inductance and capacitance are extracted from the electromagnetic simulation of the unit DMS pattern. After designing a microstrip prototype LPF at a normalized frequency, scaling to LPF is performed. The size of the DMS pattern corresponding to the required inductance and capacitance for the LPF design is determined by the established equations or curve-fitting process. Afterwards, open stubs are connected for shunt capacitance to complete the design. As a design example, a 9-pole DMS LPF with 3 GHz of cutoff frequency is designed and measured. The proposed DMS LPF has better attenuation characteristics, wider rejection band and miniaturized layout by 17% compared to the LPF designed according to conventional design. It is also suggested that the measured performances agree excellently with the prediction without any additional tuning.

https://doi.org/10.5370/KIEE.2024.73.5.819

김예찬;정민경;조우현;(Ragil Handito);구본혁;강형구

Asset management in power industries is crucial for maximizing asset value by considering life-cycle data and ensuring reliability and cost-effectiveness. This paper addresses the paradigm shift in asset management strategies from traditional approaches to Condition-Based Risk Management (CBRM). Unlike international practices, South Korea relies on Risk-Based Replacement (RBR), which assesses risk based on equipment's years of service, leading to premature replacements of Gas-Insulated Switchgear (GIS) without considering equipment condition. Consequently, asset value maximization is hindered. To address this, the paper evaluates the degradation characteristics and health condition of aging GIS O-rings used for approximately 27 years. The collected O-ring samples were in excellent condition. The findings contribute to efficient maintenance cycle determination and the establishment of economical and efficient power facility asset management strategies.

https://doi.org/10.5370/KIEE.2024.73.5.827

박정웅;정상원;이현호;징민준;이기근

This study presents the development of a lead zirconate titanate (PZT)-based Febry-Perrot Interferometer (FPI) tailored for the selective transmission of specific wavelengths. Our FPI integrates two mirrors, 3-channel PZT actuators, and interfacing electronics, enabling dynamic adjustments in PZT actuator lengths through voltage application. The interface electronics facilitate precise voltage control over the multi-channel PZT actuators, regulating the air gap between mirrors. Experimental results demonstrate the effectiveness of the developed interfacing electronics in modulating the transmission peak of light, resulting in a narrowed full width at half maximum (FWHM) and a heightened transmittance rate at targeted wavelengths. Additionally, the interface adeptly manages multi-channel PZT voltages, mitigating potential mirror alignment discrepancies during FPI assembly. By optimizing the air gap between the mirrors, significant enhancements in the center wavelength of the transmitted beam are achieved.

https://doi.org/10.5370/KIEE.2024.73.5.834

박상언;김진호;김도현;박태근

In this paper, we designed a realtime collision detection system using a visual neural network including LGMD2 of insects. The algorithm was designed to be hardware-friendly, and a pipeline structure was applied through critical path analysis. The exponential function was replaced with a linear approximation through error analysis to satisfy complexity and accuracy. By modifying the algorithm in the on/off channel, the space for storing the intermediate values of one frame size was reduced. Through performance analysis, errors were minimized and appropriate bit widths for each signal were determined. The simulation shows that collisions were detected at the correct time when five artificial and real images were applied. The proposed architecture was synthesized using Dongbu HiTek's 110nm standard cell library. As a result, 30.7K gates are required, and the maximum operating frequency is 263MHz, showing real-time processing performance of 125fps when applying 1920×1080 video.

https://doi.org/10.5370/KIEE.2024.73.5.842

이영준;김석은

Four-axis strain gauges, widely employed in military control systems, often experience increased tolerance and potential malfunctions when subjected to harsh temperature and vibration conditions. In response to this challenge, this paper presents a compensation method designed to mitigate the tolerance associated with four-axis strain gauges used in military applications. Firstly, we conduct an evaluation and analysis of the tolerance linked to strain gauges, considering factors such as ambient temperature variations and signal processing circuitry. Subsequently, we introduce a software-based approach that incorporates temperature sensors to counteract the effects of ambient temperature, thereby enhancing performance in both tolerance and offset correction regions of the strain gauges. Experimental results, obtained through the application of this software technique, demonstrate reliable operation during temperature and operational tests.

https://doi.org/10.5370/KIEE.2024.73.5.849

이방욱;권일;이도규

Due to the rapid increase in renewable energy sources and the need to accommodate and utilize them, the construction of MVDC distribution networks is required as a core technology, and related research and development budgets have been established and industry-academia research and development is actively underway. However, since the MVDC distribution network is directly connected to the receiver, research and development of electrical safety management technology is essential for the stable operation of the DC grid and the spread of its use. In this study, as a basic step for establishing a DC grid electrical safety strategy policy, we aimed to comprehensively analyze the electrical safety-related items and implications required for the DC grid to be built in the future through an analysis of the application status, application methods, and core element technologies to be pursued for electrical safety, focusing on the application points where the DC grid is currently commercialized or planned to be commercialized. To this end, we focused our research and analysis on DC electric railways, DC electric propulsion ships, and DC buildings where DC power grids are currently being built or constructed. Based on this, we conducted an in-depth analysis of the main safety factors to be considered from a system perspective in the application of DC grids, explored how the DC grid will be organized in the future, and presented technologies for DC grid electrical safety elements that require research and development.

https://doi.org/10.5370/KIEE.2024.73.5.860

양경란;홍민호

The purpose of this study was to evaluate the effect of additional plasma treatment on the degree of osteoblast attachment for sandblasted and acid-etched (SLActive) titanium surfaces. A vacuum plasma equipment was used to ensure a uniform plasma treatment on the implant surface for biological activation. The study compared the microstructure, surface properties, cytotoxicity, cell adhesion, and contact angle of XPEEDActive and SLActive surfaces. In the cytotoxicity evaluation, both XPEEDActive and SLActive showed suitable cell viability compared to the control group. The study found that XPEEDActive surfaces exhibited improved cell attachment compared to SLActive surfaces, with filopodia observed to grow and spread more widely. Additionally, XPEEDActive had better surface wettability than SLActive, as measured by contact angle. In conclusion, the XPEEDActive surface treatment showed improvement compared to the existing SLActive treatment, with favorable surface properties for enhanced cell growth.

https://doi.org/10.5370/KIEE.2024.73.5.865

김종겸;박영진

Induction motors are the most widely used rotating devices to obtain rotational power in industrial and commercial facilities. Induction motors are inductive loads and have a low power factor. Although this induction motor is sometimes used to drive a load with rated output, it is often operated at an output lower than the rated output. The reactive power used to compensate for the power factor of this induction motor is calculated based on the rated output, but in reality, the reactive power is insufficient at loads lower than the rating. Because it is difficult to select reactive power according to load fluctuations, domestic standards recommend the size of the capacitor for reactive power compensation according to the voltage and capacity of the induction motor. In reactive power compensation, there are two methods: installing a capacitor for each load and installing all of them in a bundle. In lump compensation, the size of reactive power is applied differently depending on the capacity of the transformer. In this study, we selected several low-voltage induction motors and analyzed how the power factor changes according to the change in power according to the change in load for individual compensation and lump compensation. As a result of the analysis, it was confirmed that at 1/2 load, the power factor required by the power company was not satisfied even if a power factor correction device was installed.

https://doi.org/10.5370/KIEE.2024.73.5.871

배정현;이재향;김도현;강동석;손용;연시모

Recent advances in additive manufacturing technology have made it possible to produce components with complex geometric structures using the Laser Powder Bed Fusion(L-PBF) process. However, there are still limitations when manufacturing extreme geometric shapes, such as thin wall. The thin walls are vulnerable to thermal deformation due to local heat accumulation in L-PBF. In this study, we applied a pulse mode with low thermal effect to manufacture ultra thin-wall structures using Inconel 718 in L-PBF and manufacturing characteristics were compared with the continuous wave emission mode. Then the process and mechanical properties of the pulse mode were analyzed through unit specimens and tensile specimens.

https://doi.org/10.5370/KIEE.2024.73.5.879

김도현;이재향;배정현;홍석준;연시모;강동석;손용

This study aims to achieve uniformity in heat history by mitigating heat gradients during the production of overhang structures using the metal powder melting process. Specimens with a 30-degree overhang angle were created, and monitoring of thermal radiation intensity during the process confirmed heat accumulation in the specimens. The optimized laser scan path compensation design resulted in a 5.98% reduction in the coefficient of variation of thermal radiation intensity, and X-Ray CT imaging revealed an 80.47% reduction in deformation. With the optimized laser scan path compensation design developed in this study, it is anticipated that the metal powder melting method for manufacturing aerospace components with complex shapes, including overhang structures, will yield a reduction in deformation due to alleviated heat accumulation.

https://doi.org/10.5370/KIEE.2024.73.5.885

유홍국;구욱현;노광철;김재문

Unlike fossil fuels, renewable energy sources must be critical to preserving our eco system, and ensuring a sustainable future for mankind. In Korea, renewable energy sources are continuously expanded and distributed, and according to The statistics of Korea Electric Power Corporation in 2022, renewable energy accounts for 18.35% of all power generation facilities, of which solar power accounts for 80.34%. In this paper, a case analysis focused on PV accounts for 86.1% of the RPA power purchase amount in Korea. When PV generation facilities with ESS were operated, the annual net profit was very high up to 15 years when ESS REC sales revenue was generated, and in 16 to 20 years after the ESS service life period was over, the net profit was the same as when only PV was operated. Therefore, if solar power generation facilities with ESS were operated, the accumulated net profit was converted to surplus in the 14th year, and if only PV was operated, it was converted to surplus in the 23rd year due to additional investment costs.

https://doi.org/10.5370/KIEE.2024.73.5.893

양승원;윤종천;어두림;이협

DED(Directed energy deposition) is one of the additive manufacturing process that uses high intensity laser beam to make a melt pool onto a substrate while supplying metal material to the beam focusing area to fabricate components. This offers the advantage of enabling the 3D shape addition on the existing part and even deposit different materials from the existing ones. Thanks to these process characteristics, many attempts are being made to enhance functionality by depositing new materials that can compensate for the shortcomings of existing parts. This study investigates the possibility of depositing a Ni-based alloy, specifically Inconel 625, onto a pure copper substrate through the DED process with the goal of enabling operation in high-temperature and high-pressure environments, such as gas turbines or turbojet engines, by simultaneously achieving high thermal conductivity and high-temperature strength. A parametric study was conducted on process variables such as the Inconel 625 powder feed rate, laser output, and travel speed. Furthermore, experimental results were analyzed through observations using an optical microscope and EDS analysis of the deposition interface.

https://doi.org/10.5370/KIEE.2024.73.5.900

정창모;이종우

Life cycle cost (LCC) analysis is crucial for estimating total cost of system constructions across various industries, especially defense, aerospace, railways where products are complex and long-lasting. A significant challenge in LCC modeling lies in the limited availability of reliable life-cycle data, leading to uncertainties in system specifications, estimation methods, and scenario analysis. Despite the existence of historical construction data, inherent uncertainties often restrict their direct use. In projects like catenary system construction for railways, LCC is heavily influenced by project length, with material costs being one of the most deterministic elements compared to other cost factors. This paper proposes a novel cost element coefficients method to facilitate the estimation of total construction costs. Our method leverages historical data and addresses uncertainties, providing a practical tool for LCC analysis in railway projects.

https://doi.org/10.5370/KIEE.2024.73.5.906

이강호;이종우

This paper presents a comprehensive methodology for applying FMECA(Failure Modes, Effects, and Criticality Analysis) to railway vehicle braking systems, guided by international and national standards. In this paper, through the analysis of related regulations and requirements, the primary failure modes were identified, and an FMECA method was developed based on these results. By comparing and analyzing the proposed FMECA methodology with actual field data and confirming its effectiveness, it was possible to confirm the utility of the proposed analysis method as a means of verification for RAMS related conformity assessment.

https://doi.org/10.5370/KIEE.2024.73.5.912

박보현;김지훈

The installation of new facilities, such as ESS, HVDC, TCSC, and IBR, is causing the power system to become more complicated. This complexity is leading to the emergence of new patterns that have not been encountered previously. This changes in the power system increase the probability of system instability, therefore emphasizing the importance of responding with an long-term planning. This paper examines the factors that impact the current stability area due to the growth in IBR, as well as the categories that are classified as new stability areas. This paper examines the factors that impact the current stability area due to the growth in IBR, as well as the categories that are classified as new stability areas. We also examined recent instances of domestic and international system instability caused by the proliferation of converter-based facilities. Finally, to address evolving power system stability concerns, we examine essential response factors using international case studies.

https://doi.org/10.5370/KIEE.2024.73.5.923

한대철;정준화;문학룡

The door lock system of large lodging facilities such as hotels and resorts adopts an electronic battery-type method. Existing door lock systems have problems such as cost and work efficiency degradation due to difficulty in replacement considering battery conditions and difficulty in maintenance through remote state monitoring. In this study, it was proposed to predict battery conditions or replacement timing by implementing a capacitor-lithium combination battery system. In addition, a system that can remotely monitor and manage battery conditions was implemented by incorporating Wi-Fi technology. Through this, it is possible to reduce budget and increase maintenance efficiency by predicting battery replacement timing of the combination battery system in the door lock system.