• 전력전자학회논문지
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• 제3권4호
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• pp.273-279
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• 1998

본 논문에서는 제안하는 계단충전방식에서는 직렬로 연결된 전지에 있어서 각 전지의 $\Delta$V=0 시점이 서로 다름을 고려하여 각 전지별로 선택적으로 충전단계를 절환시킴으로써 과충전 또는 부족충전을 예방할 수 있도록 하였다. 또한, 각 단계의 초기에 전지간의 잔존용량의 불균등을 해소하기 위해 시분할 균등충전모드를 추가하였다. 기존의 계단충전방식에 비해 선택적 충전단계절환을 위한 간단한 회로가 추가되지만 과충전과 부족충전을 예방하므로 전지수명과 충전효율을 개선시킬 수 있다.

• Journal of Power Electronics
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• 제13권2호
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• pp.186-196
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• 2013

This paper presents a low voltage-stress AC-linked charge equalizing system for balancing the energy in a serially connected, valve-regulated lead acid battery string using a modular converter that consists of multiple transformers coupled together. Each converter was coupled through an AC-linked bus to increase the overall energy transfer efficiency of the system and to eliminate the problem of the unbalanced charging of batteries. Previous solutions are based on centralized and modularized topologies. A centralized topology requires a redesign of the hardware and related components. It also faces a high voltage stress when the number of batteries is expanded. Modularized solutions use low-voltage-stress, double-stage, DC-linked topologies which leads to poor energy transfer efficiency. The proposed solution uses a low-voltage stress, AC-linked, modularized topology that makes adding more batteries easier. It also has a better energy transfer efficiency. To ensure that the charge equalization system operates smoothly and safely charges batteries, a small intelligent microcontroller was used in the control section. The efficiency of this charge equalization system is 85%, which is 21% better than other low-voltage-stress DC-linked charging techniques. The validity of this approach was confirmed by experimental results.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 하계학술대회 논문집
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• pp.37-39
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• 2008

In this paper, a three-port bidirectional modular circuit applied in charging and discharging equalization for lithium-ion battery strings is proposed. This circuit consists of four MOSFETs and one transformer which provide a simple structure to be easily modularized. Compared to conventional individual cell equalization schemes, it utilizes the transformer as the energy transfer element, allowing direct transfer of energy between arbitrary two cells of three-cell battery module, thus improving the equalization efficiency significantly by using much less number of equalizers for long battery strings. Simulation results are presented to validate the circuit operation and confirm its capability to equalize the three-cell battery module.

• Journal of Power Electronics
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• 제7권4호
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• pp.343-352
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• 2007

This paper proposes a modularized charge equalization converter for hybrid electric vehicle (HEV) lithium-ion battery cells, in which the intra-module and the inter-module equalizer are Implemented. Considering the high voltage HEV battery pack, over approximately 300V, the proposed equalization circuit modularizes the entire $M^*N$ cells; in other words, M modules in the string and N cells in each module. With this modularization, low voltage stress on all the electronic devices, below roughly 64V, can be obtained. In the intra-module equalization, a current-fed DC/DC converter with cell selection switches is employed. By conducting these selection switches, concentrated charging of the specific under charged cells can be performed. On the other hand, the inter-module equalizer makes use of a voltage-fed DC/DC converter for bi-directional equalization. In the proposed circuit, these two converters can share the MOSFET switch so that low cost and small size can be achieved. In addition, the absence of any additional reset circuitry in the inter-module equalizer allows for further size reduction, concurrently conducting the multiple cell selection switches allows for shorter equalization time, and employing the optimal power rating design rule allows fur high power density to be obtained. Experimental results of an implemented prototype show that the proposed equalization scheme has the promised cell balancing performance for the 7Ah HEV lithium-ion battery string while maintaining low voltage stress, low cost, small size, and short equalization time.

• 인터넷정보학회논문지
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• 제24권1호
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• pp.87-97
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• 2023

충전기 인프라 시설은 일정한 전력 공급량을 기반으로 설계 및 설치되어 있다. 초기 설계된 충전 시설은 급속히 성장하는 전기 차량의 충전을 한정된 공급 전력량 기반으로 지원한다. 또한, 현재 상용차량은 완전 충전만 가능하며, 급속 균등 충전 방식으로 지원된다. 하지만 상용차량은 정해진 스케줄에 따라 운영되기에 탄력적인 충전이 필수적이다. 본 논문에서는 전기 차량의 급속한 성장 및 증가에 따라 동일 전력량을 기반으로 상용 버스의 고정 스케줄 기반 충전 스케쥴링 및 전력 분배 기법을 활용하여 20%이상 효율 향상된 전력 운영방안을 제시한다.

• Journal of Power Electronics
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• 제18권4호
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• pp.1211-1222
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• 2018

This study presents a power distribution control scheme for a three-phase interleaved parallel DC/DC converter in a battery energy storage system. To extend battery life and increase the power equalization rate, a control method based on the nth order of the state of charge (SoC) is proposed for the charging and discharging processes. In the discharging process, the battery sets with high SoC deliver more power, whereas those with low SoC deliver less power. Therefore, the SoC between each battery set gradually decreases. However, in the two-stage charging process, the battery sets with high SoC absorb less power, and thus, a power correction algorithm is proposed to prevent the power of each particular battery set from exceeding its rated power. In the simulation performed with MATLAB/Simulink, results show that the proposed scheme can rapidly and effectively control the power distribution of the battery sets in the charging and discharging processes.

• 전력전자학회논문지
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• 제20권2호
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• pp.160-166
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• 2015

This study proposes an improved cell balancing circuit for fast equalization among lithium-ion (Li-ion) batteries. A simple voltage sensorless charge balancing circuit has been proposed in the past. This cell balancing circuit automatically transfers energy from high-to low-voltage battery cells. However, the circuit requires a switch with low on-resistance because the balancing speed is limited by the on-resistance of the switch. Balancing speed decreases as the voltage difference among the battery cells decrease. In this study, the balancing speed of the cell balancing circuit is enhanced by using the auxiliary circuit, which boosts the balancing current. The charging current is determined by the nominal battery cell voltage and thus, the balancing speed is almost constant despite the very small voltage differences among the batteries. Simulation results are provided to verify the validity of the proposed cell balancing circuit.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.554-559
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• 1998

Equalizing the state of charge of cell that affects the charge/discharge quality and efficiency of the battery through the charge/discharge characteristic experiments of battery source, we develope the high efficiency charge/discharge system which would be used in serial HEV with the constant engine-generator output. For this, establishes the electrical model of Ni-MH battery appropriate to the high efficiency charge/discharge conditions. There is no model of Ni-MH cell, so we used Ni-Cd model and obtain the Ni-MH model through the experiment. A reason that each cell has the same charge/discharge property for applying the cell model to serial/parallel connected battery source extensively is needed. Therefore, in this paper, propose the Ni-MH charger/discharger has the equalization charging function and selectable cut-off function.

• 한국조명전기설비학회지:조명전기설비
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• 제11권2호
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• pp.94-101
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• 1997

본 논문에서는 일정 주기마다 전지의 단자전압을 검출하여 단자전압에 따라 균등충전 시간을 시분할로 제어하여 전지간의 불균등을 해소시키는 균등 충전방식을 제안하였다. 기존의 균등 충전방식과 달리 구조가 간단하고 소형, 경량으로 전지자동차용 탑재형 균등 충전시스템으로 이용이 가능하다. 또한, 원칩 마이크로프로세서를 이용하여 일정 주기마다 단자전압을 검출하여 제어하므로 전지의 과충전을 예방할 수 있고, 따라서 전지 수명 연장에도 효과적이라 할 수 있다.

• 동력기계공학회지
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• 제18권6호
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• pp.193-199
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• 2014

The series connected battery cells are mainly used in high voltage battery pack application. However parameter inequality of each battery cell makes battery voltage imbalance problem. In this paper, a new balancing circuit utilizing converter scheme for the series connected battery cells is proposed. Proposed circuit offers easy control and fast equalization time. Moreover the circuit can be used in a practical application because it has high modularity and can operate during the charging/discharging cycle. To show its superiorness and effectiveness, the principle of proposed circuit is explained with computer simulation and experiment is carried out using lithium-ion battery.