• International Journal of Fluid Machinery and Systems
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• v.8 no.4
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• pp.304-310
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• 2015

Numerical simulation was applied to investigate the Taylor vortex flow inside the concentric cylinders with a constant radial temperature gradient. The reliability of numerical simulation method was verified by the experimental results of PIV. The radial velocity and temperature distribution in plain and 12-slit model at different axial locations were compared, and the heat flux distributions along the inner cylinder wall at different work conditions were obtained. In the plain model, the average surface heat flux of inner cylinder increased with the inner cylinder rotation speed. In slit model, the slit wall significantly changed the distribution of flow field and temperature in the annulus gap, and the radial flow was strengthen obviously, which promoted the heat transfer process at the same working condition.

• Proceedings of the KIEE Conference
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• summer
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• pp.260-262
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• 2004

In recent years, both utilities and users have expressed their deep concerns about the quality of electric power. The harmonic is the one of power quality disturbance, it can raise a problem on the power system. In this paper, the increasing application of power electronic equipment [especially (ASDs adjustable speed drives)] on distribution systems has led to a growing concern for harmonic distortion and the resulting impacts on system equipment and operations. The purpose of this study is to calculate the quantity of harmonic voltage by varying the RECT side ASD load and to design the optimal harmonic filter for the elimination of harmonics.

• Nuclear Engineering and Technology
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• v.47 no.4
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• pp.461-471
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• 2015

Recently, the estimation of the social cost of energy sources has been emphasized as various novel energy options become feasible in addition to conventional ones. In particular, the social cost of introducing measures to protect power-distribution systems from power-source instability and the cost of accident-risk response for various power sources must be investigated. To account for these risk factors, an integrated societal risk assessment framework, based on power-uncertainty analysis and accident-consequence analysis, is proposed. In this study, we applied the proposed framework to nuclear power plants, solar photovoltaic systems, and wind-turbine generators. The required capacity of gas-turbine power plants to be used as backup power facilities to compensate for fluctuations in the power output from the main power source was estimated based on the performance indicators of each power source. The average individual health risk per terawatt-hours (TWh) of electricity produced by each power source was quantitatively estimated by assessing accident frequency and the consequences of specific accident scenarios based on the probabilistic risk assessment methodology. This study is expected to provide insight into integrated societal risk analysis, and can be used to estimate the social cost of various power sources.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1139-1140
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• 2011

식물성 절연유는 기존에 사용되던 광유와 비교하여 우수한 생분해성 및 뛰어난 난연 특성을 가지고 있다. 반면에 광유 대비 높은 점도로 인하여 냉각 효과가 떨어지기 때문에 효과적인 사용을 위해서는 변압기 내부 온도 상승에 따른 특성 검토가 필요하다. 본 연구에서는 배전급 유입변압기에 대하여 광유와 식물성 절연유의 내부 온도 분포 특성 비교를 위한 시제품을 제작하여 실제 내부 온도를 측정하고 3차원 해석을 통하여 광유와 절연유의 열적 특성을 비교하였다.

• Journal of electromagnetic engineering and science
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• v.16 no.4
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• pp.199-205
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• 2016

We present a novel schematic using a 3-dB coupler to transmit radiofrequency (RF) power to two receivers selectively. Whereas previous multiple receiver supporting schemes used hardware-switched methods, our scheme uses a soft power-allocating method, which has the advantage of variable power allocation in real time to each receiver. Using our scheme, we can split the charging area and focus the RF power on the targeted areas. We present our soft power-allocating method in three main points. First, we propose a new power distribution hardware structure using a FPGA (field-programmable gate array) and a 3-dB coupler. It can reconfigure the transmitting power to two receivers selectively using accurate FPGA-controlled signals with the aid of software. Second, we propose a power control method in our platform. We can variably control the total power of transmitter using the DC bias of the drain input of the amplifier. Third, we provide the possibility of expansion in multiple systems by extending these two wireless power transfer systems. We believe that this method is a new approach to controlling power amplifier output softly to support multiple receivers.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.162-167
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• 1991

The manipulability ellipsoid and the force ellipsoid for a single robot are extended to the case of a multi-robot system. The force ellipsoid is applied to solve the optimal load distribution for the multi-robot system. Two cases are considered in solving the optimal load distribution. In one case, there are no constraints on the joint torques, and the analytic solution ;a given. In the other case, the torque constraints are given in terms of the maximum power consumption, and the algorithm for the solution is proposed.

• Journal of Electrical Engineering and Technology
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• v.4 no.3
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• pp.382-388
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• 2009

Recently, hydrogen energy has been anticipated to change the paradigm of conventional power systems because it can expand sustainable energy utilization and conceptually provide remarkable flexibility to power system operation. Since hydrogen energy can be converted to electric energy through fuel cells, fuel cells are expected to play an important role in the future hydrogen economy. In this paper, a Proton Exchange Membrane Fuel Cell (PEMFC) is modeled as an equivalent circuit and its steady-state characteristics investigated using the model. PEMFCs can be connected to power systems through power conditioning systems, which consist of power electronic circuits, and which are operated as distributed generators. This paper analyzes the effects of the characteristics of the PEMFC internal voltages and investigated the dynamic responses of the PEMFC under fault conditions. The results show that the fault current contribution of the PEMFC is different from those of conventional generators and is closely related to its operating point.

• Journal of Power Electronics
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• v.19 no.2
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• pp.549-559
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• 2019

This paper proposes an adaptive sliding mode control (ASMC) strategy with an enhanced optimal reaching law (EORL) for the robust current tracking control of the boost converter based hybrid power source (HPS) in an electric vehicle (EV). A conventional ASMC strategy based on state observers and the hysteresis control method is used to realize the current tracking control for the boost converter based HPS. Then a novel enhanced exponential reaching law is proposed to improve the ASMC. Moreover, an enhanced exponential reaching law is optimized by particle swarm optimization. Finally, the adaptive control factor is redesigned based on the EORL. Simulations and experiments are established to validate the ASMC strategy with the EORL. Results show that the ASMC strategy with the EORL has an excellent current tracking control effect for the boost converter based HPS. When compared with the conventional ASMC strategy, the convergence time of the ASMC strategy with the EORL can be effectively improved. In EV applications, the ASMC strategy with the EORL can achieve robust current tracking control of the boost converter based HPS. It can guarantee the active and stable power distribution for boost converter based HPS.

• Journal of Korea Society of Digital Industry and Information Management
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• v.12 no.2
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• pp.1-6
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• 2016

Several efforts to replace the use of existing fossil energy resources have already been made around the world. As a result, a new industry of renewable energy has been created, and efficient energy distribution and storage has been promoted intensively. Among the newly explored renewable energy sources, the most widely used one is solar energy generation, which has a high market potential. An energy storage system (ESS) is a system as required. In this paper, the design and implementation of an ESS for the efficient use of power in stand-alone street lights is presented. In current ESS applied to stand-alone street lights, either 12V~24V DC (from solar power) or 110V~220V AC (from commercial power) is used to recharge power in systems with lithium batteries. In this study, an ESS that can support both solar power and commercial power was designed and implemented; it can also perform emergency recharge of portable devices from solar powered street lights. This system can maximize the scalability of ESSes using lithium batteries with efficient energy conversion, with the advantage of being an eco-friendly technology. In a ripple effect, it can also be applied to smart grids, electric vehicles, and new, renewable storage markets where energy storage technology is required.

• Journal of Power Electronics
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• v.16 no.1
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• pp.111-120
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• 2016

Generally, a single phase H-bridge converter feeding a single primary track is employed in conventional inductive power transfer systems. However, these systems may not be suitable for some high power applications due to the constraints of the semiconductor switches and the cost. To resolve this problem, a novel dual coupled primary tracks IPT system consisting of two high frequency resonant inverters feeding the tracks is presented in this paper. The primary tracks are wound around an E-shape ferrite core in parallel which enhances the magnetic flux around the tracks. The mutual inductance of the coupled tracks is utilized to achieve adjustable power sharing between the inverters by configuring the additional resonant capacitors. The total transfer power can be continuously regulated by altering the pulse width of the inverters' output voltage with the phase shift control approach. In addition, the system's efficiency and the control strategy are provided to analyze the characteristic of the proposed IPT system. An experimental setup with total power of 1.4kW is employed to verify the proposed system under power ratios of 1:1 and 1:2 with a transfer efficiency up to 88.7%. The results verify the performance of the proposed system.