• 전력전자학회논문지
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• 제6권1호
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• pp.34-42
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• 2001

전지는 화학에너지를 기계적인 처리과정 없이 전기에너지로 직접 전환하는 장치이다. 부하전압과 부하전류의 용량에 따라 단위전지를 직.병렬 연결하여 사용하게 되며, 전지의 병렬운전은 단독운전 보다 전압강하를 더 천천히 발생시키므로 전압강하에 민감한 전력변환장치들의 효율에 밀접한 관계를 가지고 있다. 병렬운전의 필요성과 장점 때문에 대부분의 축전지를 사용하는 시스템은 병렬운전을 하고 있고, 반면에 선.구 축전지 사이에서 순환 전류가 흐르고, 자가방전이 일어나는 단점 또한 가지고 있다. 신 축전지에서 충.방전 전류가 과다하게 흐르는 불평형 현상과 이로 인해 축전지의 수명단축을 일으키게된다. 본 논문에서는 마이크로 프로세서를 사용하여 선.구 축전지 사이의 볼평형 전류를 검출하고 외부저항을 첨가시켜 내부저항의 차이에 대한 감소효과를 얻어 불평형 전류를 보상하였다. 이를 실험을 통해 구현하였다.

• Journal of Power Electronics
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• 제11권4호
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• pp.408-417
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• 2011

The plug-in hybrid electric vehicles (PHEVs) are specialized hybrid electric vehicles that have the potential to obtain enough energy for average daily commuting from batteries. The PHEV battery would be recharged from the power grid at home or at work and would thus allow for a reduction in the overall fuel consumption. This paper proposes an integrated power electronics interface for PHEVs, which consists of a novel Eight-Switch Inverter (ESI) and an interleaved DC/DC converter, in order to reduce the cost, the mass and the size of the power electronics unit (PEU) with high performance at any operating mode. In the proposed configuration, a novel Eight-Switch Inverter (ESI) is able to function as a bidirectional single-phase AC/DC battery charger/ vehicle to grid (V2G) and to transfer electrical energy between the DC-link (connected to the battery) and the electric traction system as DC/AC inverter. In addition, a bidirectional-interleaved DC/DC converter with dual-loop controller is proposed for interfacing the ESI to a low-voltage battery pack in order to minimize the ripple of the battery current and to improve the efficiency of the DC system with lower inductor size. To validate the performance of the proposed configuration, the indirect field-oriented control (IFOC) based on particle swarm optimization (PSO) is proposed to optimize the efficiency of the AC drive system in PHEVs. The maximum efficiency of the motor is obtained by the evaluation of optimal rotor flux at any operating point, where the PSO is applied to evaluate the optimal flux. Moreover, an improved AC/DC controller based Proportional-Resonant Control (PRC) is proposed in order to reduce the THD of the input current in charger/V2G modes. The proposed configuration is analyzed and its performance is validated using simulated results obtained in MATLAB/ SIMULINK. Furthermore, it is experimentally validated with results obtained from the prototypes that have been developed and built in the laboratory based on TMS320F2808 DSP.

• 전기학회논문지
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• 제58권3호
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• pp.531-538
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• 2009

The paper deals with an operation scheme to improve the forecasting of output range and to regulate the active power output of the hybrid system consisting of a doubly fed induction generator (DFIG) and a fuel-cell. The power output of the wind turbine fluctuates as the wind speed varies and the slip power between the rotor circuit and power converter varies as the rotor speed change. The power fluctuation of a DFIG makes its operation difficult when a DFIG is connected to grid. A fuel cell system can be individually operated and adjusted output power, hence the wind turbine and fuel cell hybrid system can overcome power fluctuation by using a fuel-cell power control. In this paper, a fuel-cell is performed to regulate the active power output in comparison with the regulated active power output of a DFIG. And it also improves the forecasting of output range. Based on PSCAD/EMTDC tools, a DFIG and a proton exchange membrane fuel cell(PEMFC) is simulated and the dynamics of the output power in hybrid system are investigated.

• 한국전자통신학회논문지
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• 제9권6호
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• pp.641-647
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• 2014

독립형 태양광발전시스템은 배전선로와 계통 연계되지 않고 독립적으로 운영된다는 장점이 있어 시공설비가 간단하고 비용이 적게 드는 장점이 있지만 MPPT를 포함한 컨버터와 생산된 에너지를 배터리에 저장하기 위한 충전회로 및 배터리 매니징 회로가 요구된다. 기존의 대체에너지분야의 이용은 복합발전의 형태보다는 하나의 발전 형태를 주로 채택하고 있으나 태양광/풍력 복합발전시스템을 최적설계하고 배터리능력을 향상시켜 설치가격을 합리화 할 수 있는 통합형 제어시스템이 필요하다.

• Journal of Power Electronics
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• 제19권6호
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• pp.1467-1476
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• 2019

Grid unbalanced faults can cause core saturation of power transformer and produce lower-order harmonics. These issues increase the electrical stress of power electronic devices and can cause a tripping of an entire HVDC system. In this paper, based on the positive-sequence and negative-sequence impedance model of a VSC-HVDC system as seen from the point of common connection (PCC), the resonance problem is analyzed and the factors determining the resonant frequency are obtained. Furthermore, to suppress over-voltage and over-current during resonance, a novel method using a virtual harmonic resistor is proposed. The virtual harmonic resistor emulates the role of a resistor connected in series with the commutating inductor without influencing the active and reactive power control. Simulation results in PSCAD/EMTDC show that the proposed control strategy can suppress resonant over-voltage and over-current. In addition, it can be seen that the proposed strategy improves the safety of the VSC-HVDC system under unbalanced faults.

• Journal of Electrical Engineering and Technology
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• 제12권4호
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• pp.1442-1448
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• 2017

Recently, electric power systems have been operating with tight margins and have reached their operational limits. Many researchers consider a microgrid as one of the best solutions to relieve that problem. The microgrid is generally powered by renewable energies that are connected through power converters. In contrast to the rotational machines in the conventional power plants, the converters do not have physical rotors, and therefore they do not have rotational inertia. Consequently, a stand-alone microgrid has no inertia when it is powered by the only converter-based-generators (CBGs). As a result, the relationship between power and frequency is not valid, and the grid frequency cannot represent the power balance between the generator and load. In this paper, a superconducting flywheel energy storage system (SFESS) is applied to an inertia-free stand-alone (IFSA) microgrid. The SFESS accelerates or decelerates its rotational speed by storing or releasing power, respectively, based on its rotational inertia. Then, power in the IFSA microgrid can be balanced by measuring the rotor speed in the SFESS. This method does not have an error accumulation problem, which must be considered for the state of charge (SOC) estimation in the battery energy storage system (BESS). The performance of the proposed method is verified by an electromagnetic transient (EMT) simulation.

• 해양환경안전학회지
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• 제29권2호
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• pp.215-222
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• 2023

세계적 선박 배출가스 저감에 대한 규제로 인해 항만 및 부두에서 육상전원공급장치(AMP, Alternative Marine Power)가 지속적으로 사용되고 있다. 국내 또한 항만 대기질 개선 특별법에 따라 AMP의 사용이 의무화되고 있고, 다양한 친환경선박과 연계하여 활용하도록 지속적인 시도를 하고 있다. 본 논문에서는 AMP를 통해 선내 전력을 공급하는 상황을 모델링 하여 AC Load Flow Analysis를 수행하였다. 이를 통해 선박에 전력이 공급될 때의 전기적 파라미터와 손실 등에 대해서 분석할 수 있다. 아울러 Transient Stability Analysis를 통해 계통의 사고 발생 시 선내 발전기를 통한 무정전전환에 대한 HSGT(High Speed Generation Transfer)의 한계값을 도출하고 이를 적용하였을 경우 결과에 대해 검토하였다.

• 전기학회논문지
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• 제67권1호
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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.

• 한국해양환경ㆍ에너지학회지
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• 제19권2호
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• pp.120-128
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• 2016

파력발전은 파도의 위치에너지와 운동에너지를 이용한 발전방식으로 본 논문에서는 선형동기발전기를 이용한 파력발전시스템에 대하여 연구를 진행하였다. 파력 발전시스템을 분석하기 위해서는 부이의 운동과 부이와 연결과 발전기의 운동을 모델링하는 것이 매우 중요하다. 본 논문에서는 발전시스템의 분석을 위하여 선형발전기와 컨버터 시스템의 모델링을 진행하였다. 선형발전기와 컨버터 시스템의 전압 방정식 및 부이의 운동방정식을 이용하여 2상 회전좌표계에서의 벡터제어기법을 적용하여 댐핑기반의 제어기 구성을 제안한다. 파도 에너지로부터 전기에너지를 추출하기 위해서 파력발전기의 전류제어를 통해 댐핑을 적절히 조절할 수 있는 벡터제어기법 구성에 대해 제안한다. 최종적으로 제안된 제어기의 검증을 위하여 MATLAB/Simulink를 이용한 2상 회전좌표계에서의 벡터제어기의 시뮬레이션을 수행하였으며 선형 발전기 축소모델와 PCS 축소모델을 통한 실험을 수행하였다.