• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.468-469
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• 2018

본 논문에서는 MMC(Modular Multi-level Converter)타입 전압형 HVDC 서브모듈의 커패시터 용량을 추정하는 방법을 기술하였다. 서브모듈 내 별도의 전류센서 및 계측 시스템을 추가하지 않고 커패시터 용량을 추정하여 안정적인 HVDC 시스템의 동작이 가능하도록 하였으며 시뮬레이션을 통하여 타당성을 검증하였다.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.111-112
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• 2015

MMC HVDC(Multi-level Modular Converter High Voltage Direct Current)는 현재 차세대 전력망으로써 각광을 받고 있고 그에 대한 연구가 활발하게 진행 중이다. 본 논문에서는 모듈형 멀티레벨 컨버터를 이용한 전압형 HVDC 시스템의 AC 전류제어기에 대하여 기술하고자 한다. 일반적으로 사용되는 회전변환을 통한 DQ전류제어와 PR제어를 사용하여 응답특성을 PSCAD/EMTDC를 통하여 비교 검증하고자 한다.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.344-345
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• 2019

High Voltage Direct Current (HVDC) 시스템은 고압 직류 송전을 위한 시스템으로서 단위 유닛인 서브모듈로 구성된 모듈형 멀티레벨 컨버터 구조를 갖는다. 서브모듈의 신뢰성 확보 및 설계 검증은 HVDC 시스템의 성능과 효율, 크기를 결정짓는 중요한 요소이다. 본 논문에서는 (주)효성이 개발하는 200MW 모듈형 멀티레벨 컨버터 서브모듈의 성능을 검증하기 위한 특성시험을 나타낸다. 특성시험을 통해서 개발 중인 서브모듈의 성능과 보호동작을 검증한다.

• Journal of Ocean Engineering and Technology
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• v.27 no.1
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• pp.85-92
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• 2013

This paper deals with the resonant type of a WEC (wave energy converter) and the determination method of its geometric parameters which were obtained to construct the robust and optimal structure, respectively. In detail, the optimization problem is formulated with the constraints composed of the response surfaces which stand for the resonance period(heave, pitch) and the meta center height of the buoy. Use of a signal-to-noise ratio calculated from normalized multi-objective results with the weight factor can help to select the robust design level. In order to get the sample data set, the motion responses of the power buoy were analyzed using the BEM (boundary element method)-based commercial code. Also, the optimization result is compared with a robust design for a feasibility study. Finally, the power efficiency of the WEC with the optimum design variables is estimated as the captured wave ratio resulting from absorbed power which mainly related to PTO (power take off) damping. It could be said that the resultant of the WEC design is the economical optimal design which satisfy the given constraints.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.158-159
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• 2011

최근 발표된 제5차 전력수급계획에 의하면 제주도에 3번째 HVDC 연계선 설치가 계획되고 있다. 이전까지 설치된 2개의 HVDC는 LCC(전류형) HVDC로써 안정적이고 우수한 성능으로 제주지역의 전력 수급에 기여를 했지만 전압 불안정 문제를 초래할 가능성을 가지고 있다. 따라서 3번째 HVDC는 VSC(전압형)으로 설치하는 것을 고려해야 한다. VSC HVDC는 유무효 전력이 동시에 제어가 가능하다는 장점이 있으나 비싼 가격과 높은 변환 손실, 그리고 작은 용량으로 제한적인 용도로만 사용되어 왔다. 그러나 최근 Multi-Level Converter 기술이 적용되면서 이전의 많은 문제들이 해결되었다. 이 논문에서는 VSC HVDC의 최신 동향에 대해서 간략히 소개하고 제주 전력망에 VSC HVDC가 설치되었을 때의 효과에 대해서 논의하고자 한다.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.242-243
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• 2010

This paper investigates a power supply of medium voltage with enhanced ignition characteristics for plasma torch. Series resonant half-bridge topology is presented to be a suitable ignition circuitry. The ignition circuitry is integrated into the main power conversion system of a multi-phase staggered three-level dc-dc converter with a diode front-end rectifier. The plasma torch rated for 3MW, 2kA and having the physical size of 1m long is selected to be a high enthalpy source in waste disposal system. The steady-state and transient operations of plasma torch are simulated. The parameters of Cassie-Mary arc model are calculated based on 3D magneto-hydrodynamic simulations. Circuit simulation waveform shows that the ripple of arc current can be maintained within ${\pm}10%$ of its rated value under the existence of load disturbance. This power conversion configuration provides high enough ignition voltage around 5KA during ignition phase and high arc stability under the existence of arc disturbance noise resulting in a high-performance plasma torch system.

• Journal of Power Electronics
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• v.15 no.5
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• pp.1380-1391
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• 2015

This paper provides a loss analysis and comparison of high power semiconductor devices in 5MW Permanent Magnet Synchronous Generator (PMSG) Medium Voltage (MV) Wind Turbine Systems (WTSs). High power semiconductor devices of the press-pack type IGCT, module type IGBT, press-pack type IGBT, and press-pack type IEGT of both 4.5kV and 6.5kV are considered in this paper. Benchmarking is performed based on the back-to-back type 3-level Neutral Point Clamped Voltage Source Converters (3L-NPC VSCs) supplied from a grid voltage of 4160V. The feasible number of semiconductor devices in parallel is designed through a loss analysis considering both the conduction and switching losses under the operating conditions of 5MW PMSG wind turbines, particularly for application in offshore wind farms. This paper investigates the loss analysis and thermal performance of 5MW 3L-NPC wind power inverters under the operating conditions of various power factors. The loss analysis and thermal analysis are confirmed through PLECS Blockset simulations with Matlab Simulink. The comparison results show that the press-pack type IGCT has the highest efficiency including the snubber loss factor.

• 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.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.429-430
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• 2011

This paper presents a simple and cost-effective stand-alone rapid battery charging system of 30kW for electric vehicles. The proposed system mainly consists of active front-end rectifier of neutral point clamped 3-level type and non-isolated bi-directional dc-dc converter of multi-phase interleaved half-bridge topology with coupled inductors. The charging system is designed to operate for both lithium-polymer and lithium-ion batteries. The complete charging sequence is made up of three sub-interval operating modes; pre-charging mode, constant-current mode, and constant-voltage mode. The pre-charging mode employs the staircase shaped current profile to accomplish shorter charging time while maintaining the reliable operation of the battery. The proposed system is able to reach the full-charge state within less than 16min for the battery capacity of 8kWh by supplying the charging current of 67A. The optimal discharging algorithm for Vehicle to the Grid (V2G) operation has been adopted to maintain the discharging current of 1C. Owing to the simple and compact power conversion scheme, the proposed solution has superior module-friendly mechanical structure which is absolutely required to realize flexible power expansion capability in a very high-current rapid charging system.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.540-541
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• 2013

본 논문에서는 PSCAD/EMTDC를 이용하여 MMC(Modular Multi-level Converter)를 기반으로 한 HVDC 시스템 시뮬레이션 모델을 개발하였다. 스위칭 레벨의 동작을 분석하기 위해 각 ARM당 10개의 SM(Sub-Module)과 2개의 RM(Redundancy-Module)을 구성하여 11-level의 MMC 출력 전압을 형성하였다. SM 동작시 발생하는 전압 불균등 문제를 해결하기 위하여 밸런싱 알고리즘을 적용하였으며, SM의 출력 전압에 발생하는 Ripple을 고려하여 Capacitor의 용량을 설계하고 이를 검증하였다. 또한 시뮬레이션을 이용하여 HVDC 성능 분석과 MMC의 성능개선을 위한 순환전류 알고리즘 및 Redundancy 투입 알고리즘을 구현하고 그 결과를 확인하였다.