• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.367-368
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• 2010

본 논문에서는 삼상 AC-DC 컨버터와 강압컨버터를 이용한 배터리 충전장치를 제안한다. 제안 하는 배터리 충전시스템은 상용전원뿐만 아니라 태양광시스템의 MPPT제어를 통하여 최대전력을 공급받아 급속충전시스템의 CV/CC(정전압/정전류) 모드 제어를 통해 배터리를 빠르게 충전한다.

• Journal of Magnetics
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• v.20 no.1
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• pp.91-96
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• 2015

As many researchers are relentlessly trying to improve the power generation schemes from the power grid, to meet the constantly increasing electricity demand. In this paper, the results of a finite element analysis are carried out to study on a design optimization of an asymmetric air-gap structure in 3-phase Permanent Magnet Brushless DC Motors. To achieve a high efficiency for a 3-phase PM BLDC motor, the asymmetric air-gap structure is proposed considering the rotation direction of a motor. Generally, a single-phase BLDC motor is applied asymmetric air-gap structure for starting. This is because the asymmetric air-gap structure causes reluctance variation so the motor can utilize reluctance torque toward a rotation direction. In this paper, the asymmetric air-gap is applied to 3-phase BLDC SPM motor so it utilizes reluctance torque with alignment torque. A proposed model is designed by 2-D FE analysis and the results are verified by experimental test.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.551-554
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• 2019

국내 전력 계통은 경제의 성장과 더불어 생활 수준의 향상에 따라 지속적인 증설과 발전이 이루어졌다. 전력설비의 밀도 측면에서 비추어보면 미국이나 일본 대비 적게는 2배에서 많게는 4배에 이르는 최고 수준의 설비 밀도를 보이고 있다. 또한 전체 전력 생산량의 40%이상이 수도권에서 소비되고 있지만 발전설비는 최대 전력 수요지인 수도권과 먼 해안에 인접한 지역에 편재되어 있기 때문에 발생하는 수요와 공급지의 불균형, 장거리 선로를 통한 전력 전송에서 야기되는 전력계통 운영 측면에서의 문제가 발생하게 된다. 최근 화두가 되고 있는 원전 축소, 노후 화력 발전소 정지, 송전선로 경과지에서의 건설 고압 송전선로 건설 반대 등의 요인으로 인하여 전력계통을 최대한 효율적이고 안정적으로 운영하여야 하는 대전제를 만족시키기 위한 방안으로 기존 AC 기반의 계통 설비에 전력변환기술을 기반으로 하는 DC 계통 및 FACTS 설비의 확대 적용하는 방안이 제시되고 있다. 본 논문에서는 다가올 MV급 이상의 전력변환설비의 개념 및 개발 현황에 대한 소개를 하고자 한다.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.278-279
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• 2020

최근 전기차 배터리는 일 주행거리 증대를 위해서 50~100 kWh 급으로 대용량화 되고 있다. 그와 동시에 충전시간 단축을 위해서 배터리 전압은 400V에서 800V로 높아지고 급속충전기 용량은 50kW에서 350kW 급으로 대용량화 되고 있다. 본 논문에서는 전기차 증가 추세에 따라 기존 주유소를 대체하는 MW급 전기차 급속충전소를 위한 에너지 저장 장치(Energy Storage System, ESS) 연계 지능형 반도체 변압기(Solid State Transformer, SST) 기술 기반의 전력변환 시스템 모델을 제안하고자 한다. 이 모델은 배전계통에 직접 연계가 가능하기 때문에 대용량 전기차 급속충전소뿐만 아니라 DC Grid 구축에 응용 가능하다.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.395-396
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• 2020

HVDC(High Voltage Direct Current) 시스템은 무효전력의 독립적인 제어가 가능하여 계통의 안정적인 연계가 가능하다. 또한, 멀티 터미널 DC grid 구성이 가능해 다수의 계통을 통합 연계할 수 있는 장점이 있다. HVDC 시스템은 단위 유닛인 서브모듈로 구성된 MMC(Modular Multi-level Converter) 구조를 갖으며 밸브 단위로 시스템이 구성된다. VSC(Voltage Source Converter) 밸브는 IEC 62501 기반의 규격을 바탕으로 하드웨어 설계의 건전성과 성능을 확인할 수 있다. 본 논문에서는 (주)효성이 개발중인 200MW 모듈형 멀티레벨 컨버터 밸브 단위의 성능과 설계의 건전성을 확인하기 위해 밸브단위 운전시험 회로를 구성하였으며, 운전 시험 결과를 분석하였다.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.25-27
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• 2020

본 논문은 단상/3상 겸용 단일단 800V 전기차 탑재형 충전기를 제안한다. 제안하는 단일단 충전기는 넓은 단상/3상의 계통전압(120V-240V)에도 스위치의 ZVS 턴 온을 보장하며 전해 콘덴서 없이 DC충전이 가능하다. 2상 인터리브드 토템폴 구조로 구성되어 입력필터가 작으며 전해콘덴서가 없어서 5.5kW/L의 높은 전력밀도를 달성하였다. 또한 4차 고조파 주입 알고리즘을 통해 고조파 규정인 EN 61000-3-2 규정을 만족한다. 시작품의 타당성 및 성능 검증을 위해 SiC 소자를 적용하여 스위칭 주파수 150kHz의 11kW급 충전기를 제작하였고 제안하는 컨버터의 타당성 및 성능을 검증하였다.

• KEPCO Journal on Electric Power and Energy
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• v.8 no.2
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• pp.159-179
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• 2022

Often a network becomes complex, and multiple entities would get in charge of managing part of the whole network. An example is a utility grid. While the entire grid would go under a single utility company's responsibility, the network is often split into multiple subsections. Subsequently, each subsection would be given as the responsibility area to the corresponding sub-organization in the utility company. The issue of how to make subsystems of adequate size and minimum number of interconnections between subsystems becomes more critical, especially in real-time simulations. Because the computation capability limit of a single computation unit, regardless of whether it is a high-speed conventional CPU core or an FPGA computational engine, it comes with a maximum limit that can be completed within a given amount of execution time. The issue becomes worsened in real time simulation, in which the computation needs to be in precise synchronization with the real-world clock. When the subject of the computation allows for a longer execution time, i.e., a larger time step size, a larger portion of the network can be put on a computation unit. This translates into a larger margin of the difference between the worst and the best. In other words, even though the worst (or the largest) computational burden is orders of magnitude larger than the best (or the smallest) computational burden, all the necessary computation can still be completed within the given amount of time. However, the requirement of real-time makes the margin much smaller. In other words, the difference between the worst and the best should be as small as possible in order to ensure the even distribution of the computational load. Besides, data exchange/communication is essential in parallel computation, affecting the overall performance. However, the exchange of data takes time. Therefore, the corresponding consideration needs to be with the computational load distribution among multiple calculation units. If it turns out in a satisfactory way, such distribution will raise the possibility of completing the necessary computation in a given amount of time, which might come down in the level of microsecond order. This paper presents an effective way to split a given electrical network, according to multiple criteria, for the purpose of distributing the entire computational load into a set of even (or close to even) sized computational loads. Based on the proposed system splitting method, heavy computation burdens of large-scale electrical networks can be distributed to multiple calculation units, such as an RTDS real time simulator, achieving either more efficient usage of the calculation units, a reduction of the necessary size of the simulation time step, or both.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.1
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• pp.8-15
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• 2018

New methodology for probabilistic reliability based grid expansion planning of HVDC in power system including Wind Turbine Generators(WTG) is developed in this paper. This problem is focused on scenario based optimal selection technique to decide best connection bus of new transmission lines of HVDC in view point of adequacy reliability in power system including WTG. This requires two kinds of modeling and simulation for reliability evaluation. One is how is reliability evaluation model and simulation of WTG. Another is to develop a failure model of HVDC. First, reliability evaluation of power system including WTG needs multi-state simulation methodology because of intermittent characteristics of wind speed and nonlinear generation curve of WTG. Reliability methodology of power system including WTG has already been developed with considering multi-state simulation over the years in the world. The multi-state model already developed by authors is used for WTG reliability simulation in this study. Second, the power system including HVDC includes AC/DC converter and DC/AC inverter substation. The substation is composed of a lot of thyristor devices, in which devices have possibility of failure occurrence in potential. Failure model of AC/DC converter and DC/AC inverter substation in order to simulate HVDC reliability is newly proposed in this paper. Furthermore, this problem should be formulated in hierarchical level II(HLII) reliability evaluation because of best bus choice problem for connecting new HVDC and transmission lines consideration. HLII reliability simulation technique is not simple but difficult and complex. CmRel program, which is adequacy reliability evaluation program developed by authors, is extended and developed for this study. Using proposed method, new HVDC connected bus point is able to be decided at best reliability level successfully. Methodology proposed in this paper is applied to small sized model power system.

• Journal of the Korean Society for Railway
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• v.19 no.5
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• pp.617-628
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• 2016

This paper proposes the structure of a smart transformer to improve the performance of the 60Hz main power transformer for rolling stock. The proposed smart transformer is a kind of solid state transformer that consists of semiconductor switching devices and high frequency transformers. This smart transformer would have smaller size than the conventional 60Hz main transformer for rolling stock, making it possible to operate AC electrified track efficiently by power factor control. The proposed structure employs a cascade H-Bridge converter to interface with the high voltage AC single phase grid as the rectifier part. Each H-Bridge converter in the rectifier part is connected by a Dual-Active-Bridge (DAB) converter to generate an isolated low voltage DC output source of the system. Because the AC voltage in the train system is a kind of medium voltage, the number of the modules would be several tens. To control the entire smart transformer, the inner DC voltage of the modules, the AC input current, and the output DC voltage must be controlled instantaneously. In this paper, a control algorithm to operate the proposed structure is suggested and confirmed through computer simulation.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.1124-1128
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• 2021

As regulations of emissions from ships become more stringent, electric propulsion systems have been increasingly used to solve this problem in vessels ranging from large merchant ships to small and medium-sized ships. Methods for improving the efficiency of the electric propulsion system include the improvement of power sources; the use of a system linked to environmentally friendly power sources, such as batteries, fuel cells, and solar power; and the development of hardware and control methodology for rectifiers, power conversion devices, and propulsion motors. The method using a phase-shifting transformer with diodes has been widely used for rectification. Power semiconductor devices with grid connection to an environmentally friendly power source using DC distribution, a variable speed power source, and the application of small and medium-sized electric propulsion systems have been developed. Accordingly, the demand for active front-end (AFE) rectifiers is increasing. In this study, a method using a neural network rather than a conventional proportional-integral controller was proposed to control the AFE rectifier. Tested controller data were used to design a neural network controller trained through MATLAB/Simulink. The neural network controller was applied to a rectification system designed using PSIM software. The results indicated the effectiveness of improving the waveform and power factor DC output stage according to the load variation. The proposed system can be applied as a rectification system for small and medium-sized environmentally friendly ships.