• Nuclear Engineering and Technology
• /
• v.14 no.4
• /
• pp.178-185
• /
• 1982

Albedo-type boundary condition is incorporated into the finite element formulation of the cubic Hermite polynomials for the two-dimensional solution of the two-group diffusion problem. Two modifications are introduced with respect to the conventional expression for the weak form of the group diffusion equation with the zero flux or zero current boundary condition and the cubic element functions over the boundary nodes. The finite element formulations obtained from those modifications are tested with the two-dimensional ZION problem. The numerical effectiveness of the modifications are examined.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.21 no.6
• /
• pp.542-545
• /
• 2016

This work proposes a capacitive coupling-based wireless battery charging circuit that is built with vehicle glasses for electric vehicles. A capacitive coupling wireless power transfer offers many advantages, such as low metal impact and low energy transfer efficiency changes in accordance with changes in position. However, a large coupling capacitor is needed for high power transfer. Therefore, a new capacitive coupling-based wireless power transfer LLC resonant converter built with the glasses of an electric vehicle is proposed. The proposed converter is composed of coupling capacitors with glasses of an electric vehicle and two transformers for impedance transformation. The proposed LLC converter can transfer large power and obtain high efficiency with zero voltage switching. The validity and features of the proposed circuit is verified by experimental results with a 1.2 kW prototype.

• Journal of Power Electronics
• /
• v.13 no.1
• /
• pp.51-58
• /
• 2013

This paper proposes the power conversion mechanism of a bailer-charge-transfer zero-current-switching (CT-ZCS) circuit. The operation modes are analyzed and researched using state trajectory equations. The topology of CT-ZCS based on soft-switching inverters offers some merits such as: tracking the input reference signal dynamically, bearing load shock and short circuit, multiplying inverter N+1 redundancy parallel, coordinating power balance for easy control, and soft-switching commutation for high efficiency and large capacity. These advantages are distinctive from conventional inverter topologies and are especially demanded in AC drives: new energy generation and grid, distributed generation systems, switching power amplifier, active power filter, and reactive power compensation and so on. Prototype is manufactured and experiment results show the feasibility and dynamic voltage-tracking characteristics of the topology.

• Proceedings of the KIPE Conference
• /
• 2001.07a
• /
• pp.673-676
• /
• 2001

In this paper, the improved zero-voltage transition(ZVT) PWM boost converter using an inductor feedback technique is proposed. The improved circuit uses a low-voltage zener diode to reduce the turn-off witching loss of the auxiliary witch and EMI noise. Using this technique, soft-witching for the auxiliary switch is guaranted at wide line and load ranges and some of the energy circulating in the auxiliary circuit is fed to the load Since the active switches are turned on and off softly, the witching losses and EMI noise are reduced significantly and the higher efficiency of the system is achieved. In this paper, the modes of converter operation are explained and analyzed, design guidelines are given, and experimental results of 1kW, 100kHz prototype system are presented.

• Proceedings of the KIEE Conference
• /
• 2006.07c
• /
• pp.1691-1692
• /
• 2006

본 논문은 역률개선 효과가 있는 MERS(Magnetic Enery recovery switch)를 사용하여 에너지 효율에서의 결과를 입증하고자 한다. 전원과 유도성부하에 직렬 연결된 MERS는 Full Bridge와 비슷한 구성으로 전력용 MOSFET(or IGBT) SWITCH 4개와 전해 DC콘덴서 1개로 구성되어진다. MERS의 콘덴서는 부하와 콘덴서의 리액턴스, $Xc<X_L$을 만족하는 콘덴서의 용량을 선택하고 콘덴서에 충전된 전압에 의해 부하의 유도계수를 보상하여 역률을 1로 추종하며 개선된다. 이때 스위치는 전원 전압에 대해 zero-voltage switching과 zero-current switching을 하게 된다. 만약 부하가 변하더라도 $Xc<X_L$을 만족한다면 자동적으로 역률은 1에 맞추어지게 된다.

• Proceedings of the KSR Conference
• /
• 2009.05b
• /
• pp.623-628
• /
• 2009

There is an increasing demand for efficient high power/weight auxiliary power supplies for use on high speed traction application. Many new conversion techniques have been proposed to reduce the voltage and current stress of switching components, and the switching losses in the traditional pulse width modulation(PWM) converter. Especially, the phase shift full bridge zero voltage switching PWM techniques are thought most desirable for many applications because this topology permits all switching devices to operate under zero voltage switching(ZVS) by using circuit parasitic components such as leakage inductance of high frequency transformer and power device junction capacitance. The proposed topology is found to have higher efficiency than conventional soft-switching converter. Also it is easily applicable to phase shift full bridge converter by applying an energy recovery snubber consisted of fast recovery diodes and capacitors.

• Proceedings of the KSR Conference
• /
• 2008.11b
• /
• pp.321-324
• /
• 2008

Recently, there is an increasing demand for efficient high power/weight auxiliary power supplies for use on high speed traction application. many new conversion techniques have been proposed to reduce the voltage and current stress of switching components, and the switching losses in the traditional pulse width modulation(PWM) converter. Among them, the phase shift full bridge zero voltage switching PWM techniques are thought most desirable for many applications because this topology permits all switching devices to operate under zero voltage switching(ZVS) by using circuit parasitic components such as leakage inductance of high frequency transformer and power device junction capacitance. The proposed topology is found to have higher efficiency than conventional soft-switching converter. Also it is easily applicable to phase shift full bridge converter by applying an energy recovery snubber consisted of fast recovery diodes and capacitors.

• Food Science and Industry
• /
• v.55 no.2
• /
• pp.166-175
• /
• 2022

Current food system has developed with the agricultural innovation to feed the increasing population of the world, but with high costs such as environmental contamination and inequality with low sustainability. Human has developed long history of mutualistic interaction with honey bee. This manuscript describes the multi-functionality of honey bee for food production. Firstly honey bee produces honey, bee pollen, royal jelly and propolis which are rich in functionality. Second honey bee serves as the main pollinator for crop production which is worth for 28% of total crop production values in Korea. Lastly honey bee can be an alternative meat produciton system with lower energy, carbon costs but higher nutritional security. This manuscript described those parts and discussed the multi-functionality of honey bees for eco-friendly food security pursuing lowered environmental cost and carbon-zero strategies in the climate change era.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.2B no.3
• /
• pp.133-139
• /
• 2002

In this paper, a prototype of an active auxiliary quasi-resonant DC link (QRDCL) snubber assisted voltage source bidirectional power converter (AC to DC and DC to AC) operating at zero voltage soft-switching (BVS) PWM nlode is presented for a Battery Energy Storage System (BESS). The operating principle of this QRDCL circuit and multifunctional control-based converter system, including PWM inverter mode in which energy flows from the battery bank to the three-phase utility-grid in addition to an active PWM converter mode in which energy flows from the utility-grid to the battery banks are described respectively by the control implementation on the basis of d-q coordinate plane transformation. The multifunctional operation characteristics of this three-phase ZVS PWM bi-directional converter with QRDCL is demonstrated fer a BESS under the power conditioning and processing schemes of energy supply mode and energy storage mode, and compared with a conventional three-phase hard switching PWM bi-directional converter for a BESS. The effectiveness of the three-phase ZVS PWM hi-directional converter with QRDCL is proven via the simulation analysis.

• Journal of the Korean Solar Energy Society
• /
• v.33 no.2
• /
• pp.64-69
• /
• 2013

According to the Fourth Assessment Report of Intergovernmental Panel on Climate Change(IPCC) Working Group III, climate change is already in progress around the world, and it is necessary to execute mitigation in order to minimize adverse impacts. This paper suggests future climate change needs, employing IPCC Special Report on Emissions Scenarios(SRES) to predict temperature rises over the next 100 years. This information can be used to develop sustainable architecture applications for energy efficient buildings and renewable energy. Such climate changes could also affected the present supplies of renewable energy sources. This paper discusses one recent Fourth Assessment Report of IPCC (Mitigation of Climate Change) and the Hadley Centre climate simulation of relevant data series for South Korea. Result of this research may improve consistency and reliability of simulation weather data or climate change in order to take advantage of SRES and PRECIS QUMP. It is expected that these calculated test reference years will be useful to the designers of solar energy systems, as well as those who need daily solar radiation data for South Korea. Also, those results may contribute zero carbon and design of sustainable architecture establishing future typical weather data that should be gone ahead to energy efficient building design using renewable energy systems.