• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2012년도 춘계학술발표대회 논문집
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• pp.414-418
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• 2012

In recent years, understanding the dynamics of DC distribution system has become critically important due mainly to the increasing needs for the interconnection of DC distributed generators and the (DC-based) electric vehicle (EV) charging systems. In this paper, the characteristics of the DC grid system connected to the compact proton exchange membrane fuel cell (PEMFC) has been studied. In particular, the voltage and current transient phenomena were measured by varying the load of the DC grid system. Also, the voltage and current ripple were measured at the different load conditions. Our experimental results clearly manifested that the study contributes to the establishment of fundamental method to characterize the small DC grid system including distributed generation.

• Journal of Power Electronics
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• 제16권6호
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• pp.2202-2211
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• 2016

In certain applications, such as IPT-based EV charger (IPTEC), any variation in alignment and distance between pickup and charger primary leads to a change in leakage and magnetic impedance magnitudes. The power transmission capacity is not always at the maximum level because of these variations. This study proposes a new low-cost tracking method that achieves the Maximum Inductive Power Transmission Capacity (MIPTC). Furthermore, in the proposed method, the exchange of information between load and source is not required. For an application such as IPTEC, the load detected by the IPTEC varies continuously with time because of the change in state of the charge. This load variation causes a significant variation in IPT resonant circuit voltage gain. However, the optimized charging output voltage should be kept constant. From the analysis of the behavior of the IPT circuit at different working frequencies and load conditions, a MIPTC operation point that is independent of load condition can be identified. Finally, the experimental results of a developed prototype IPT circuit test show the performance of the proposed method.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.198-200
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• 2018

In this paper a single-stage single-phase differential type isolated AC-DC converter is proposed. This converter eliminates the requirement to use bulky electrolytic capacitor from the system and at the same time provides DC charging by employing the AC Power Decoupling waveform control method. All the switches of the converter achieve ZVS turn on during half line cycle and all diodes achieve ZCS turn off during entire line cycle. A conventional controller is implemented for PFC control and output regulation, whereas a power decoupling controller is added to compensate $2^{nd}$ harmonic ripple power. In addition, an interleaving technique is applied to increase the power range of the converter and reduce the input inductor size. In the end simulation verification is performed and results are obtained for 6.6KW.

• Journal of Power Electronics
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• 제13권3호
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• pp.429-436
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• 2013

Online simulations are utilized to reduce time and cost in the development and performance optimization of plug-in hybrid electric vehicle (PHEV) and electric vehicles (EV) systems. One of the most important factors in an online simulation is the accuracy of the model. In particular, a model of a battery should accurately reflect the properties of an actual battery. However, precise dynamic modeling of high-capacity battery systems, which significantly affects the performance of a PHEV, is difficult because of its nonlinear electrochemical characteristics. In this study, a dynamic model of a high-capacity battery cell for a PHEV is developed through the extraction of the equivalent impedance parameters using electrochemical impedance spectroscopy (EIS). Based on the extracted parameters, a battery cell model is implemented using MATLAB/Simulink, and charging/discharging profiles are executed for comparative verification. Based on the obtained results, the model is optimized for a high-capacity battery cell for a PHEV. The simulation results show good agreement with the experimental results, thereby validating the developed model and verifying its accuracy.

• 전력전자학회논문지
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• 제25권1호
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• pp.21-28
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• 2020

Integrated bidirectional OBC/LDC was developed to reduce the volume for elements, avoid space restriction, and increase efficiency in EV vehicles. In this study, a DC-DC converter in integrated OBC/LDC circuits was composed of an SRC circuit with a stable output voltage relative to an LLC circuit using a theoretical method and simulation. The resonant network of the selected circuit was optimized to minimize the power loss and element volume under constraints for the buck converter and the battery charging range. Moreover, the validity of the optimal model was verified through an analysis using a theoretical method and a numerical analysis based on power loss at the optimized resonant frequency.

• Journal of Power Electronics
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• 제18권1호
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• pp.309-322
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• 2018

The technology of inductive power transfer has been proved to be a promising solution in many applications especially in electric vehicle (EV) charging systems, due to its features of safety and convenience. However, loosely coupled transformers lead to the system efficiency not coming up to the expectation at the present time. Therefore, at first, the magnetic core losses are calculated with a novel magnetic-circuit model instead of the commonly used finite-element-method (FEM) simulations. The parameters in the model can be obtained with a one-time FEM simulation, which makes the calculation process expeditious. When compared with traditional methods, the model proposed in the paper is much less time-consuming and relatively accurate. These merits have been verified by experimental results. Furthermore, with the proposed loss calculation model, the system is optimized by parameter sweeping, such as the operating frequency and winding turns. Specifically, rather than a predesigned switching frequency, a more efficiency-optimized frequency for the series-parallel (SP) compensation topology is detected and a detailed investigation has been presented accordingly. The optimized system is capable of an efficiency that is greater than 93% at a coil separation distance of 200mm and coil dimensions of $600mm{\times}400mm$.

• 전기학회논문지
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• 제64권11호
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• pp.1535-1542
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• 2015

An increasing number of electric vehicles (EVs) in power system affects its reliability in various aspects. Especially under high EV penetration level, new generating units are required to satisfy system's adequacy criterion. Wind power generation is expected to take the major portion of the new units due to environmental and economic issues. In this paper, the system reliability is analyzed using Loss of Load Expectation (LOLE) and Expected Energy Not Served (EENS) under each and both cases of increasing wind power generation and EVs. A probabilistic multi-state modeling method of wind turbine generator under various power output for adequate reliability evaluation is presented as well. EVs are modeled as loads under charging algorithm with Time-Of-Use (TOU) rates in order to incorporate EVs into hour-to-hour yearly load curve. With the expected load curve, the impact of EVs on the system adequacy is analyzed. Simulations show the reliability evaluation of increasing wind power capacity and number of EVs. With this method, system operator becomes capable of measuring appropriate wind power capacity to meet system reliability standard.

• 문화기술의 융합
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• 제5권2호
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• pp.367-373
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• 2019

급격한 전기자동차의 증가에 따라 전기자동차의 배터리를 주행 목적이 아닌 다른 용도로 사용하려는 Vehicle-to-Grid (V2G) 기술 또한 산업계와 학계부터 큰 관심을 끌고 있다. V2G 기술의 도움으로 전기자동차의 배터리는 스마트 그리드 환경에서 에너지 저장장치, 전력공급원등의 여러 중요한 역할로의 사용이 가능해 진다. 본고 에서는 거주용 주택환경을 위한 기술인 Vehicle-to-Home(V2H), 상업용 건물을 위한 기술인 Vehicle-to-Building(V2B) 그리고 전체 전력망을 위한 기술인 Vehicle-to-Grid(V2G) 기술에 대해 자세히 알아보고 각 기술의 특성과 영향에 대해 검토한다. 또한 이 기술들의 경제적 영향에 대해서도 분석한다.

• KEPCO Journal on Electric Power and Energy
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• 제7권2호
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• pp.249-254
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• 2021

As the spreading speed of electric vehicles increases rapidly, those are expected to be able to use them as flexible resources in the power system beyond the concern for the supply of its charging power. Especially when the Renewable Energy sources (RES) which have no intrinsic control capability have replaced the synchronous generators more and more, the power system needs to secure the additional frequency control resources to ensure its stability. However, the feasibility of using electric vehicles as the frequency control resources should be analyzed from the perspective of the power system operation and it requires the existing simulation frameworks for the power system. Therefore, this paper proposes the grid connected modeling of the primary frequency control provided by electric vehicles which can be integrated into the existing power system model. In addition, the proposed model is implemented considering technical performances constrained by the characteristics of the Vehicle-Grid Integration (VGI) system so that the simulation results can be accepted by the power utilities operating the power system conservatively.

• 한국ITS학회 논문지
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• 제12권1호
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• pp.121-135
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• 2013

전 세계적으로 지구온난화로 인한 환경문제가 심각한 위기로 인식되어지면서 세계 각국에서는 전 산업분야에 걸쳐 이산화탄소 배출을 줄이고자 노력하고 있다. 국내 에너지 부문 CO2 배출량의 약 20%를 차지하는 수송 분야의 이산화탄소 배출을 감소시키기 위해서는 전기자동차 보급 확산이 필수적이다. 최근 정부에서 전기자동차 보급 활성화를 위해 많은 노력을 기울이고 있으나 긴 충전시간과 배터리의 가격에 의한 비싼 차량가격, 짧고 불규칙한 운행거리와 부족한 충전 인프라 등으로 인하여 향후 전기자동차의 보급 확대는 매우 불투명한 상태이다. 이러한 단점을 해결하고 효과적으로 전기자동차를 보급할 수 있는 방법 중 하나가 바로 배터리 공용제 기반의 배터리 자동교환형 전기자동차 시스템이다. 이를 위해서는 배터리를 자동으로 교환해주는 시설인 배터리 교환소 (BSS: Battery Swapping Stations)가 필요하게 되는데, BSS는 배터리 교환을 통해 전기자동차가 긴 충전시간을 소모할 필요 없이 짧은 시간 내에 배터리를 충전하고 이동할 수 있도록 하는 시스템이다. 이러한 시스템을 대중교통, 특히 공공버스에 적용함으로써 보다 빠른 시간 안에 전기자동차를 보급, 확산시키는 것이 가능하다. 일반버스를 전기버스로 전환하여 버스 노선을 운영할 경우 전기버스가 중간에 멈추지 않도록 적절한 위치에 충전시설을 구축할 필요가 있다. 전기버스에 대한 충전시설은 버스 노선의 기 종점 및 기존 버스정류장에 추가로 설치하여 버스가 승객의 승 하차를 위해 정차할 때 신속하게 배터리를 교환할 수 있게 구축해야 한다. 본 연구에서는 전기버스를 위한 배터리 자동교환충전시설의 위치선정 문제를 Set Covering Problem에 적용하여 해결하였다. 배터리 충전 시 최대 주행거리를 영향권으로 설정하였으며 메타 휴리스틱 기법인 그리디 알고리즘을 활용하여 배터리 교환형 충전인프라 배치 최적화 모델을 개발하였고 현재 운영 중인 서울시의 버스노선을 대상으로 실제 충전시설의 위치를 선정하였다.