https://doi.org/10.5370/KIEEP.2023.72.4.231

우필성(Pil-Sung Woo) ; 황민(Min Hwang) ; 모영규(Young-Kyu Mo) ; 김영석(Young-Seok Kim)

As part of environmental regulations and greenhouse reduction measures, electric vehicles and large-capacity ESS are expected to spread, and also the volume of discarded lithium-ion batteries is expected to increase rapidly. The market size of discarded lithium-ion batteries is expected to be 3,364 GWh ($57.4 billion) by 2030. This paper analyzes policies, standards, and R&D trends in major countries (Republic of Korea, the United States, China, Europe, Japan) regarding used Li-batteries, and then propose measures to revitalize the circular economy of Li-batteries while ensuring safety

https://doi.org/10.5370/KIEEP.2023.72.4.237

전병영(Byung-Young Chun) ; 김동일(Dong-Il Kim) ; 전동훈(Dong-Hoon Jeon) ; 문상필(Sang-Pil Mun) ; 우경일(Kyung-Il Woo)

The matrix converter(MxC)is an ac-to-ac conversion device that can generate variable magnitude variable frequency output voltage. Nine bi-directional switches of MxC allow PWM control of output voltages and input currents. PWM switching needs “switch commutations” from one switch to another. During the switch commutations, however, unwanted voltage error occurs like a dead time effect in Voltage Source Inverter(VSI). When PWM pulse width is narrower than the time required for the commutation, voltage error rapidly increases. This voltage distortion is critical in the low speed operation as system becomes sensitive to even a small voltage error. In this paper, a new PWM strategy is proposed for improving voltage control performance in the low voltage region. Based on the input and output voltage information, PWM pulse-widths are controlled to avoid incomplete commutations. The feasibility of the proposed method is proved by simulation and experimental results

https://doi.org/10.5370/KIEEP.2023.72.4.243

남길동(Gil-Dong Nam) ; 김동일(Dong-Il Kim) ; 문상필(Sang-Pil Mun) ; 황정원(Jeong-Won Hwnag) ; 유의정(Yeoi-Joung Ryu) ; 우경일(Kyung-Il Woo)

This paper discusses operation characteristics of a direct power controlled PWM converter. The key of this strategy is a direct selection of switching modes on the basis of instantaneous errors of active and reactive power. In addition, this paper presents a theoretical analysis on relation between the instantaneous power and the switching modes, which is essential to compose a switching mode table. The feature of this method is high speed response owing to direct instantaneous power control with relay elements; hence a DC-bus smoothing capacitor can be minimized. Controllability of the proposed technique was examined through various experimental tests, and it was confirmed that the maximum total input power factor and efficiency were 99.6[%] and 96.6[%] over a load power range from 400 to 1.6[kW], respectively. Moreover this paper discusses operation characteristics of the direct power controlled PWM converter, compared with a conventional subharmonic PWM converter, under unbalanced power source condition. Experimental data prove that the proposed technique achieves more than 95[%] power factor and less than 6[%] DC bus ripples.

https://doi.org/10.5370/KIEEP.2023.72.4.250

김규원(Gyu-Won Kim) ; 지평식(Pyeong-Shik Ji)

This paper studied effective grounding design methods according to the application of distribution line impedance. It has been proven that the construction cost and grounding area can be reduced and economic feasibility improved by calculating and reflecting the ground fault current at the customer's actual receiving point rather than the theoretical maximum value as the fault current standard during grounding design. In addition, when this method was adopted, a Lattice ground plate that satisfied KEC was applied to the mesh ground electrode to compensate for the increase in transient impedance due to the reduced ground electrode area. It has been shown to be effective in improving the transient grounding impedance of the mesh grounding system compared to the increase in construction cost, and is believed to be applicable to the mesh grounding method currently being designed and constructed.

https://doi.org/10.5370/KIEEP.2023.72.4.256

김명현(Myong-Hyon Kim) ; 김진석(Jin-Seok Kim)

Due to the recent increase in the sensitive load of the power system, power quality is becoming important. The voltage drops are part of power quality and the effects of voltage drops have being studied in various sections. This studies are as one of the related studies in the change of the voltage sag by the impedance of superconducting current limiter(SFCL) which compensates the voltage drops when a fault occurs. In this paper, we analyzed the effect of voltage compensation on non-fault lines with various failure locations with multiple impedance cases of SFCL. As a result, the larger impedance of the SFCL shows the greater voltage compensation effect, and it was confirmed that the impedance of the resistor have the greater voltage compensation effect than that of the reactor. In addition, the voltage compensation effect was found across all lines when a fault occurred, and it was checked that the closer fault occurred to the power source, the greater the compensation effect. To analyze the effect of voltage compensation with load distribution, SARFI was calculated according to the case study. The higher effect was found at the concentrated loads at rear compared to the uniform loads, because the large number of customers at the rear of the power line. And this characteristic has contributed positively to SARFI.

https://doi.org/10.5370/KIEEP.2023.72.4.262

조주희(Juhee Cho) ; 김수용(Suyong Kim) ; 이승재(Seungjae Lee) ; 김병택(Byungtaek Kim)

Research on Medium voltage DC converter station is actively developed to construct a DC power grid. In addition, for stable operation of the converter station, sensor technology is essential to precisely measure and analyze the voltage and current of the electrical devices in the converter station. This paper is about a fluxgate-type current sensor to measure DC current in an MVDC power grid. Three-dimensional finite element analysis was applied to analyze the linearity of a fluxgate type current sensor according to the number of excitation winding turns. The number of excitation winding turns must be sufficient so that the ring core can operate with high permeability even with small changes in primary current.

https://doi.org/10.5370/KIEEP.2023.72.4.267

이기영(Gi-Young Lee) ; 김청훈(Chunghun Kim) ; 김상일(Sang-Il Kim)

To ensure a high efficiency of a power factor correction (PFC) converter, the totem-pole bridge-less PFC (TBPFC) topology is proposed, replacing the diode rectifier stage with a power semiconductor switch. However, a current spike of an AC side may occur during rectification timing, so an appropriate control algorithm is required. This paper proposes a control algorithm for TBPFC, including DC-link voltage and inductor current control. The proposed algorithm has a simple control structure using a general proportional-integrator (PI) control structure and controls the power factor and output DC voltage simultaneously. The sensed input voltage value is used to define the low-speed switch leg operation and calculate the AC inductor current reference. The feed-forward duty is calculated to ensure the stable operation of the high-speed switch leg. The control algorithm is implemented through a control board based on TI's digital signal processor (DSP), and the hardware in the loop simulation (HILS) device is used for hardware simulation. The validity of the proposed algorithm is verified using PSIM simulation and HILS environment.

https://doi.org/10.5370/KIEEP.2023.72.4.275

손은태(Eun-Tae Son) ; 배인수(In-Su Bae) ; 김성열(Sung-Yul Kim) ; 김욱원(Wook-Won Kim) ; 김동민(Dong-Min Kim)

Recently, various studies have been conducted on enhancing the resilience of the power grid in order to effectively respond to low-probability, high-impact events such as natural disasters or catastrophes. This paper proposes a feasibility study model that focuses on assessing the resilience of the next-generation power grid. The resilience enhancement of the power grid is considered with constraints in the proposed model, and it is estimated by the expected value of resilience enhancement (EoRE) considering the uncertainty of fault situations. In the case study, the feasibility study incorporates not only the capacity of distributed generators (DG) but also analyzes the optimal locations for DG to improve the resilience of the power grid. The analysis results of EoRE demonstrate that the location of DG for enhancing power grid resilience is closely related to the grid configuration.

https://doi.org/10.5370/KIEEP.2023.72.4.283

백찬수(Chan-Soo Baek)

In this paper, a UV LED-based light source device for wafer edge exposure was developed. In the light source device for edge exposure, a UV LED light source and a heat dissipation design for lens and heat dissipation are essential to improve light output concentration. As a result of the simulation according to the lens material and type, the use of three types of silicone lenses showed superior results than the use of glass lenses. In addition, an aluminum light source module was developed through experiments on various heat dissipation models. As a result of measuring the gray zone to evaluate the usefulness of the developed edge exposure light source module, it can be seen that it shows sufficient performance as an exposure light source. We intend to continuously evaluate reliability by installing a light source module for edge exposure developed in the future at the site.

https://doi.org/10.5370/KIEEP.2023.72.4.289

김동일(Dong-Il Kim) ; 전병영(Byung-Young Chun) ; 전동훈(Dong-Hoon Jeon) ; 문상필(Sang-Pil Mun) ; 우경일(Kyung-Il Woo)

Therefore, in order to realize high-speed H/L pulse operation, a DC-DC converter that realizes high-speed response speed is required. Methods for controlling these DC-DC converters include PI control, hysteresis control, and model prediction control, but output dead beat control is used to realize fast and precise voltage transitions. At this time, control considering three-phase interleaving of the step-down DC-DC converter, higher switching frequency, and delay time is possible. At this time, a batch control that operates by phase shifting the duty cycle of the reference phase in a three-phase interleaved circuit and an individual control that controls the duty cycle of each phase were proposed. In addition, high-speed H/L pulse operation was realized using capacitor current feedback capable of high-speed detection. In the experiment, the switching frequency was 800 [kHz], the pulse frequency was 10[kHz], and H/L pulse operation of 280[V] / 70[V] was realized, and the voltage transition time from L to H achieved 6.7[μs].

https://doi.org/10.5370/KIEEP.2023.72.4.298

이종훈(JongHoon Lee) ; 손다빈(Dabin Son) ; 정영민(Yungmin Jeong) ; 김한영(HanYeong Kim) ; 한상욱(Sangwook Han) ; 이동호(Dongho Lee)

This paper analyzes the inertial impact on dynamic simulations of power systems with changes in load models. The growing significance of inertial assessments in power systems is attributed to the increasing penetration of renewable energy. Inertial considerations encompass not only generator inertia but also load inertia. Typically, the load model employed in power system analysis is the ZIP (ZIPload) model. We hypothesized that introducing parameter variations in the load model would affect system inertia in the course of conducting power system analyses. Consequently, depending on the inertia estimation method, the inertia of the entire system was found to vary from a minimum of 1.6% to a maximum of 18% due to load model parameter changes. This underscores the crucial role of load modeling in estimating the inertia of power systems.

https://doi.org/10.5370/KIEEP.2023.72.4.306

김광호(Kwang-Ho Kim) ; 이진욱(Jin-Wook Lee) ; 손성용(Sung-Yong Son)

The coefficient of performance (COP) of an air source heat pump represents its energy efficiency, and it is common to use a constant value for convenience. However, using an average COP for comparing energy consumption does not consider the actual operating environments, leading to limitations in accuracy. In this study, we applied both a linear first-order function model and a quadratic second-order function linearization model to the annual average and variable COPs of air source heat pumps in residential buildings. Through a simulation-based case study, we analyzed the impact of the COP of air source heat pumps on the annual energy consumption and energy costs in residential buildings.

https://doi.org/10.5370/KIEEP.2023.72.4.315

김태완(Tae-Wan Kim) ; 곽근창(Keun-Chang Kawk)

In recent years, research has been conducted into technologies that acquire biological signals in various situations such as healthcare and smart cars, and analyze the acquired signals to perform user recognition, emotion classification, and health status monitoring. Among them, heartbeat is a direct element that represents a person's physical and mental state. Conventional photoplethysmography (PPG) and electrocardiogram (ECG) methods require separate hardware for acquisition, making it difficult to acquire heartbeats in everyday situations. In this paper, we pre-processing videos to emphasize parts related to blood flow and reduce computing resource and times. and we design a model that utilizes 3D-CNN (3Dimension-Convolutional Neural Networks) to predict blood flow signals in a non-contact method through one second facial videos, while reducing the number of input channels. The blood flow signal predicted from the learned model extracted frequency regions related to heartbeat in various frequency regions through CWT (Continuous Wavelet Transform) analysis, and predicts heart rate through the frequency with the highest energy signal among them. Finally, we compared the predicted heart rate from one second facial videos with heart rates obtained though sensors, verified the proposed pre-processing methods and model’s performance

https://doi.org/10.5370/KIEEP.2023.72.4.320

원성홍(Sung-Hong Won)

This paper presents a development process of slotless motors using block-coil stator. The slotless motors have many advantages such as no cogging, high controllability. However, the manufacturing process of slotless motors is known to be very difficult and thus the manufacturing cost is very high. This is an obstacle to the proliferation of slotless motors despite many advantages. However, the block coil stator type slotless motor is emerging as a new alternative to overcome the weakness of the slotless motor, which is difficult to manufacture. So, in this paper, the author present novel manufacturing process of a slotless motor known as block-coil stator and the verification through design and prototyping of block-coil stator slotless motors.

https://doi.org/10.5370/KIEEP.2023.72.4.326

이환익(Hwanol Lee) ; 현두수(Doosoo Hyun) ; 김지훈(Jihun Kim)

The metropolitan area system in Korea is experiencing various system stability problems due to large concentration of loads and non-expansion of transmission facilities. In particular, in the northern Gyeonggi area, there are operational difficulties such as bus separation operation due to an increase in fault current. Yangju 200MW BTB VSC HVDC is the first BTB VSC HVDC scheduled for commercial operation in Korea, and can play a role in reducing fault current in the northern Gyeonggi system through the grid separation effect of BTB VSC HVDC. In addition, excellent control capabilities of HVDC can improve various system stability. In this paper, we reviewed a method of selecting the optimal operating point of HVDC that can eliminate facility overload that may occur in the event of contingencies in the northern Gyeonggi area in addition to fault current and minimize system loss.