• 한국산업융합학회 논문집
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• 제23권2_1호
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• pp.115-124
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• 2020

In wireless power transfer (WPT) system, the conventional compensation topologies only can provide a constant current (CC) or constant voltage (CV) output under their resonant conditions. It is difficult to meet the CC and CV hybrid charging requirements without any other schemes. In this study, a switching hybrid topology (SHT) is proposed for CC and CV electric vehicle (EV) battery charging. By utilizing an additional capacitor and two AC switches (ACSs), a double-side LCC (DS-LCC) and an inductor and double capacitors-series (LCC-S) topologies are combined. According to the specified CC and CV charging profile, the CC and CV charging modes can be flexibly converted by the two additional ACSs. In addition, zero phase angle (ZPA) also can be achieved in both charging modes. In this method, because the operating frequency is fixed, without using PWM control, and only a small number of devices are added, it has the benefits of low-cost, easy-controllability and high efficiency. A 3.3-kW experimental prototype is configured to verify the proposed switching hybrid charger. The maximum DC efficiencies (at 3.3-kW) of the proposed SHT is 92.58%.

• 전력전자학회논문지
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• 제26권6호
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• pp.421-428
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• 2021

Lithium-ion secondary batteries exhibit advantageous characteristics such as high voltage, high energy density, and long life, allowing them to be widely used in both military and daily life. However, the lithium-ion secondary battery does have its limitation; for example, the output power and capacity are readily decreased due to the increased internal impedance during discharging at a lower temperature (-32℃, military requirement). Also, during charging at a lower temperature, lithium dendrite growth is accelerated at the anode, thereby decreasing the battery capacity and life as well. This paper describes a study that involves increasing the internal temperature of lithium-ion secondary battery by energy circulation operation in a low-temperature environment. The energy circulation operation allows the lithium-ion secondary battery to alternately charge and discharge, while the internal resistance of lithium-ion battery acts as a heating element to raise its own temperature. Therefore, the energy circulation operation method and device were newly designed based on the electrochemical impedance spectroscopy of the lithium-ion secondary battery to mediate the battery performance at a lower temperature. Through the energy circulation operation of lithium ion secondary battery, as a result of the heat generated from internal resistance in an extremely low-temperature environment, the temperature of the lithium-ion secondary battery increased by more than 20℃ within 10 minutes and showed a 75% discharging capacity compared with that at room temperature.

• 한국인터넷방송통신학회논문지
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• 제24권4호
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• pp.141-146
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• 2024

기존의 화석연료와 발전기를 통하여 에너지를 생산하고 즉시 소모하던 방식에서 에너지를 저장하고 효율적으로 생산하고 이용하기 위한 에너지저장장치(ESS, Energy Storage System)가 개발되었다[1]. 이러한 에너지저장장치에 현재까지 2차전지 리튬이온(Li-ion) 배터리를 가장 많이 사용하고 있다. 따라서 리튬이온 배터리의 성능, 수명, 안전성을 향상시키기 위하여 셀(Cell) 단위로 관리하는 BMS(Battery Management System)의 역할이 매우 중요하다[2]. 특히 BMS의 기능 중 셀 간의 불균형 전압을 균형적으로 맞추는 셀 밸런싱(Cell Balancing) 기법은 에너지저장장치에서 배터리의 최적화를 도모할 수 있다. 이러한 최적화를 통해 모든 셀이 동일한 전압과 용량을 유지하여 성능향상, 출력 안정성을 유지할 수 있다[3]. 따라서 본 논문에서는 셀 간의 불균형이 발생한 리튬이온 배터리를 충전할 때 BMS의 기능 중 하나인 셀 밸런싱 기법의 동작 특성에 대하여 살펴보고자 한다.

• KEPCO Journal on Electric Power and Energy
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• 제5권3호
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• pp.157-163
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• 2019

현재까지 피크완화 및 에너지 절감을 위해 한국전력공사 120여개 사옥에 K-BEMS (KEPCO Building Energy Management System)가 운영 중이다. 이 시스템은 PV, PCS, BESS, EMS 등으로 구성되어 있으며 건물에너지 수요예측을 기반으로 BESS, PV 등을 활용하여 에너지 관리를 도모하고 있다. 이 시스템은 단기 과거데이터에 신경망기법을 단순 적용하여 수요를 예측함에 따라 예측 정확도가 높지 않고 운영자 수작업을 통한 BESS 충방전으로 피크 저감이 곤란하며 운영 경제성 제고가 어려운 실정이다. 이러한 문제를 해결하기 위해 전력연구원에서는 2016년부터 3년간 연구과제를 수행하였는데 이를 통해 에러를 최소화하며 높은 신뢰도를 가지는 실시간 수요예측기법과 이에 기반한 BESS충방전 최적화 자동화 기술 개발, 성능을 검증하였기에 이를 본 논문에서 소개하고자 한다.

• 한국산업융합학회 논문집
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• 제25권6_2호
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• pp.1071-1081
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• 2022

As the demand for high-rise buildings increases, the demand for high-speed elevators is also increasing. In order to make a high-speed elevator, a method is needed to reduce the weight of the elevator's components, which is a constraint on the increase in speed. As a measure to reduce the weight, it is possible to remove the traveling cable for power and signal supply. Since the weight of the traveling cable varies depending on the position of the carriage, it is difficult to compensate the weight using the counter weight. The power supply is a structure in which a brush-rail type power input terminal is installed in the elevator hoistway to receive power in a contact-type manner while the carriage is moving. If a small-capacity ESS is installed in a passenger car, power can be supplied uninterruptedly inside the passenger car. A small-capacity ESS charging system to be applied to such an elevator system is required to perform several functions. First, the passenger Car must be able to charge as much as possible even during high-speed operation. A control algorithm with high responsiveness is required because charging starts and ends repeatedly by the partially installed input power stage. In addition, if the input-side line impedance is large due to the structure of the system and the response characteristic is increased, the stability of the system may be lowered. Accordingly, in this paper, we propose a control algorithm that has a stable steady-state output while having a fast response in a transient state. To verify the proposed control algorithm, simulation was conducted using PSIM, and the performance of the controller was verified by manufacturing a prototype buck conveter charger.

• 한국항행학회논문지
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• 제24권6호
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• pp.566-572
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• 2020

무선 전력전송기에서 두 유도 코일 사이의 무선 전력전송 특성과 영향에 대해서 알아보고, 무선 전력전송 기술을 이용한 전력변환기 회로와 배터리 충·방전기 회로를 제안한다. 무선 전력전송기 및 무선 충전기의 장점은 기존의 플러그인 탑재형 유선 충전기(OBC; on-board charger) 대신 무선으로 전력을 전송하여 배터리에 전력 충전 시 사용자가 외부에서 전원을 연결 시키지 않고 무선으로 충전할 수 있는 점이다. 또한 무선충전의 이점은 2차 측 정류기의 회로와 수신 코일을 사용하여 에너지 효율 향상 효과를 가져올 수 있으나, 대용량의 원거리 무선충전 방식은 전송거리에 대한 한계가 있어 현재 많은 연구가 진행되고 있다. 비 접촉 방식의 전력 전송기의 전력을 전송 할 수 있는 송신부 인 1차측 코일과 수신부인 2차측 코일 및 하프브리지(half bridge) 직렬공진 컨버터를 적용한 무선 전력전송장치의 송신부 회로와 수신부 회로의 연구를 목적으로 무선충전시스템의 전력전송거리 향상을 위한 새로운 토폴로지를 적용하고, 각각의 거리에 따른 실험을 통해 8 cm 전송거리에서 출력 3 kW 일 때, 최대 효율(95.8%)을 확인 할 수 있었다.

• 한국정보통신학회논문지
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• 제16권2호
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• pp.279-287
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• 2012

전기 자동차의 배터리는 휘발유 경유로 연료를 공급하는 자동차에 비해 배터리 충전에 오랜 시간이 소요된다. 이는 전기 자동차의 상용화를 위해 산업계에서 해결해야 할 문제이다. 따라서 관련 업계에서는 배터리 교환소에서 충전되어 있는 배터리를 교체해 주는 방안이 제시되고 있다. 하지만, 아직 배터리 교체 방법에 대한 보안 위협과 요구 사항 등에 대한 연구가 미비한 실정이다. 본 논문에서는 배터리 교체 충전 방식에서 보안을 위협하는 요소들을 살펴보고, 이를 해결하기 위해 보안 요구사항을 적용한 배터리 교체식 시스템을 정의한다. 본 논문의 연구 결과는 추후 배터리 충전 방식의 상용화 및 해당 분야의 보안 분석에 있어 참고자료의 역할을 할 것으로 기대된다.

• 한국태양에너지학회 논문집
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• 제33권5호
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• pp.69-75
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• 2013

To increase the efficiency of the photovoltaic, almost photovoltaic appliances are controlled by Maximum Power Point Tracking(MPPT). Existing most of the PV MPPT techniques have used power which multiplies sensed output current and voltage of the solar cell. However, these algorithms are unnecessarily complicated and too expensive for small and compact system. The other hand, the proposed MPPT technique is only one sensing of the MPPT converter's output current, so there is no need to insert another sensors of battery side. Therefore, this algorithm is simpler compared to the traditional approach and is suitable for low power solar system. Further, the novel proper charge/discharge algorithm for the battery with PV MPPT is developed. In this algorithm, there is CC battery charge mode and load discharge mode of the PV cell & battery dual. Also we design current control to regulate allowable current during the battery charging. The proposed algorithm will be applicable to battery included solar cell applications like solar lantern and solar remote control car. Finally, the proposed method has been verified with computer simulation.

• 전력전자학회논문지
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• 제19권2호
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• pp.106-115
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• 2014

This paper proposes ESS DC-DC Converter using Redox Flow Battery (RFB) for stand-alone microgrid. Price, safety, expandability and dynamics are crucial in ESS. Reports show that Zinc-bromine (ZnBr) RFB is the best choice in ESS. Simple electrical ZnBr RFB model is obtained from charging test. DC-DC converter Inductor current-DClink Voltage model is proposed for the DC microgrid. For the controller design in z-domain, the K-factor method is by considering nature of the digital controller. The control performance has been verified with simulation and hardware experiments. Lastly 10kW DC microgrid using RFB test result is shown.

• Journal of Power Electronics
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• 제15권4호
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• pp.1006-1017
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• 2015

This paper presents a finite control set model predictive control (FCS-MPC) strategy for the AC/DC matrix converter used in grid-connected battery energy storage system (BESS). First, to control the grid current properly, the DC current is also included in the cost function because of input and output direct coupling. The DC current reference is generated based on the dynamic relationship of the two currents, so the grid current gains improved transient state performance. Furthermore, the steady state error is reduced by adding a closed-loop. Second, a Luenberger observer is adopted to detect the AC input voltage instead of sensors, so the cost is reduced and the reliability can be enhanced. Third, a switching state pre-selection method that only needs to evaluate half of the active switching states is presented, with the advantages of shorter calculation time, no high dv/dt at the DC terminal, and less switching loss. The robustness under grid voltage distortion and parameter sensibility are discussed as well. Simulation and experimental results confirm the good performance of the proposed scheme for battery charging and discharging control.