• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.299-300
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• 2015

This paper proposes current-fed bi-directional DC-DC converter using a resonance (CF-BCR) with wide output voltage range. The steady state analysis and operation principles of CF-BCR are introduced. To increase the output voltage range with satisfying soft switching condition, switching frequency, duty and number of times of the resonance are controlled. The proposed converter and its control method are verified by theoretical analysis and PSIM simulation.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 전력전자학술대회
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• pp.367-368
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• 2017

본 논문에서는 영전류 모드로 진입한 zero voltage transition(ZVT) interleaved bi-direction low voltage DC-DC converter(IB-LDC)의 도통 손실을 최소화하기 위한 위상 제어가 제안된다. IB-LDC의 출력단 배터리가 완충되어 영전류 모드로 진입하면 IB-LDC의 입 출력 평균 전류는 0[A]로 감소하지만 보조 회로 전류는 기존의 설계 값에 의해 감소하지 않아 지속적인 도통 손실을 일으킨다. 따라서 본 논문에서는 영전류 모드로 진입한 IB-LDC의 보조 회로에 ZVT 조건을 만족시키는 공진 전류만 흐르도록 하여 도통 손실을 최소화하는 위상 제어를 제안하였다. 또한 PSIM simulation 및 실험을 통해 증명하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 전력전자학술대회
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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.

• Advances in nano research
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• 제10권2호
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• pp.175-189
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• 2021

In this article, frequency characteristics, and sensitivity analysis of a size-dependent laminated composite cylindrical nanoshell under bi-directional thermal loading using Nonlocal Strain-stress Gradient Theory (NSGT) are presented. The governing equations of the laminated composite cylindrical nanoshell in thermal environment are developed using Hamilton's principle. The thermodynamic equations of the laminated cylindrical nanoshell are obtained using First-order Shear Deformation Theory (FSDT) and Fourier-expansion based Generalized Differential Quadrature element Method (FGDQM) is implemented to solve these equations and obtain natural frequency and critical temperature of the presented model. The novelty of the current study is to consider the effects of bi-directional temperature loading and sensitivity parameter on the critical temperature and frequency characteristics of the laminated composite nanostructure. Apart from semi-numerical solution, a finite element model was presented using the finite element package to simulate the response of the laminated cylindrical shell. The results created from finite element simulation illustrates a close agreement with the semi-numerical method results. Finally, the influences of temperature difference, ply angle, length scale and nonlocal parameters on the critical temperature, sensitivity, and frequency of the laminated composite nanostructure are investigated, in details.

• 전력전자학회논문지
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• 제18권1호
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• pp.26-36
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• 2013

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. 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-charge mode, constant-current mode, and constant-voltage mode. The pre-charge mode employs the stair-case shaped current profile to accomplish shorter charging time while maintaining the reliable operation of the battery. The proposed system is specified to reach the full-charge state within less than 16min for the battery capacity of 8kWh by supplying the charging current of 78A. 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.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 전력전자학술대회 논문집
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• pp.323-324
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• 2013

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. 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-charge mode, constant-current mode, and constant-voltage mode. The pre-charge mode employs the stair-case shaped current profile to accomplish shorter charging time while maintaining the reliable operation of the battery. The proposed system is specified to reach the full-charge state within less than 16min for the battery capacity of 8kWh by supplying the charging current of 78A. 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.

• 한국융합학회논문지
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• 제2권2호
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• pp.35-45
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• 2011

최근 정부의 녹색성장 정책에 의해 배전계통에 태양광, 풍력발전 등과 같은 분산전원의 보급률이 지속적으로 증가되고 있는 실정이다. 이러한 분산전원의 설치가 급증함에 따라 기존 배전계통의 조류흐름은 단방향(One-direction)에서 양방향(Bi-direction)으로 변화되고 고장전류의 증 감이 발생하는 등, 다양한 변화가 생겨 배전계통의 운용상에 여러 가지 문제점들이 발생할 가능성이 커지고 있다. 따라서 본 논문에서는 분산전원의 배전계통 연계에 따른 보호기기의 정정 및 양방향 보호협조검토가 가능한 보호협조 평가알고리즘을 제안하고, 그 알고리즘을 바탕으로 양방향 보호협조 평가시스템을 제작하였다. 또한 평가시스템을 이용하여 배전계통을 모델링하고 분산전원 연계 시 보호기기들 사이의 보호협조를 검토하여, 분산전원이 연계된 경우 배전계통에 발생할 수 있는 기술적인 문제점들을 분석하여 그 방안을 제시하였다.

• 한국산학기술학회논문지
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• 제14권6호
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• pp.2971-2978
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• 2013

최근 배전계통은 정부의 녹색성장 정책으로 태양광, 풍력발전 등과 같은 분산전원의 보급률이 지속적으로 증가되고 있는 실정이다. 이러한 분산전원의 연계로 기존 배전계통의 조류흐름은 단방향(One-direction)에서 양방향(Bi-direction)으로 변화되고, 고장전류의 증 감이 발생하는 등, 다양한 변화가 생겨 배전계통의 운용상에 여러 가지 문제점들이 발생할 가능성이 커지고 있다. 따라서 본 논문에서는 분산전원의 배전계통 연계에 따른 보호기기의 정정 및 양방향 보호협조 검토가 가능한 보호협조 평가알고리즘과 실제의 사고전류 값을 이용한 개선된 T-C곡선 알고리즘을 제안하고, 이 알고리즘을 바탕으로 양방향 보호협조 평가시스템을 개선하였다. 또한 평가시스템을 이용하여 배전계통을 모델링하고, 분산전원 연계 시 보호기기들 간의 보호협조를 검토하여, 분산전원이 연계된 경우 배전계통에 발생할 수 있는 기술적인 문제점들을 분석하여 그 방안을 제시하였다.

• 전기학회논문지
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• 제66권4호
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• pp.733-739
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• 2017

Research on fuel cell systems attracting attention as an environmentally friendly energy source has been actively conducted. And research is being conducted on railway vehicles that use direct current power generated by a fuel cell as an energy source. In this paper, a two-phase interleaved bidirectional DC-DC converter has been proposed which can supply electric energy of a battery to a traction motor during powering and charge the battery with regenerative energy during braking. Therefore, the topology of the energy storage system applied to the railway vehicle was analyzed, and the simulation was performed by constructing the power conversion system by this topology. Experiments were also conducted through hardware design and fabrication based on the simulation analysis results, and the validity of the hardware implementation was verified.

• 전력전자학회논문지
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• 제21권2호
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• pp.95-101
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• 2016

This paper proposed a high-power density bidirectional converter for hybrid electric vehicle high-voltage DC-DC converter(HDC). The conventional HDC has two disadvantages. First, large inductance is required to satisfy the ripple current of inductor by low switching frequency (<20 kHz). Second, large core size is required to prevent the saturation of inductor by high current. Compared with the conventional HDC, the proposed HDC can reduce inductance with SiC-FET for high frequency driving. High-power density of I/O capacitors can be achieved through two-phase interleaved method. The high-power density of inductors can be achieved because the offset current of magnetizing inductance is theoretically terminated by using the differential mode coupled inductor instead of using two single inductors. The validity of the proposed converter is proved through the 50 kW prototype.