• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.513-520
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• 2018

Since Paris Climate Change Conference in 2015, many policies to reduce the emission of greenhouse gas have been accelerating, which are mainly related to renewable energy resources and micro-grid. Presently, the technology development and demonstration projects are mostly focused on diversifying the power resources by adding wind turbine, photo-voltaic and battery storage system in the island-type small micro-grid. It is expected that the large-scaled micro-grid projects based on the regional district and town/complex city, e.g. the block type micro-grid project in Daegu national industrial complex will proceed in the near future. In this case, the economic cost or the carbon emission can be optimized by the efficient operation of energy mix and the appropriate construction of electric and heat supplying facilities such as cogeneration, renewable energy resources, BESS, thermal storage and the existing heat and electricity supplying networks. However, when planning a large residential town or city, the concrete plan of the energy infrastructure has not been established until the construction plan stage and provided by the individual energy suppliers of water, heat, electricity and gas. So, it is difficult to build the efficient energy portfolio considering the characteristics of town or city. This paper introduces an energy mix optimization(EMO) method to determine the optimal capacity of thermal and electric resources which can be applied in the design stage of the real large-scaled residential town or city, and examines the feasibility of the proposed method by applying the real heat and electricity demand data of large-scale residential towns with thousands of households and by comparing the result of HOMER simulation developed by National Renewable Energy Laboratory(NREL).

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.1
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• pp.35-44
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• 1998

In this paper, input LC filter design of diode rectifiers considering filter V A rating reduction has been propoesd. It consisted of an input LC parallel resonent tank whose inductor and capacitor values are se$.$ lected so that the input filter presents an infinite impedance to harmonic input ac current component. The operation of proposed input filter has been analyzed in detail under steady state conditions. Performance evaluation and related design data have been provided on Per Unit basis for the proper implementation of diode rectification system. Finally, Detailed input and output current analysis has shown that the proposed input filter yield high quality input ac current waveforms, in particular, high input power factor values and more reliabilty which reducing the V A rating of passive components as compared to the standard type LC filter.filter.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.11a
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• pp.387-390
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• 2005

A This paper presents a novel three-phase current-fed Pulse Width Modulation converter with switched- capacitor type resonant DC link commutation circuit operating PWM pattern strategy under a design consideration of low-pass filter, which can operate on the basis of the principle of zero current soft-switching commutation. In the first place, the steady-state operating principle of this converter with a new resonant DC link snubber circuit is described in connection with the equivalent operation circuit, together with the practical design procedure of the switched-capacitor type resonant DC link circuit is discussed from a theoretical viewpoint on the basis of a design example for high-power applications. The actively delayed time correction method to compensate distorted currents due to a relatively long resonant commutation time is newly implemented in the open loop control scheme so as to acquire the new optimum PWM pattern. Finally, the experiment or set-up in laboratory system or this converter is concretely demonstrated herein to confirm a zero current soft-switching commutation of this converter. The comparative evaluations between current-fed hard switching PWM and soft-switching PWM converters are carried out from a viewpoint of their PWM converter characteristics.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.2
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• pp.20-27
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• 2007

[ $SF_6$ ] gas for compacted power facilities has a important role as an insulation gas. It is very blown well that $SF_6$ gas has the superior characteristics as an insulation gas. For reliable operation of SF6-gas-based high and medium voltage equipment it is very important to keep the insulation ability within a safe range. And the experimental and measuring system were implemented. The test chamber designed to endure up to 3 atmospheric pressure. The analysis results of the experimental data shows that positive partial discharge can be detected by discharge current and UHF signal. Additionally it is shown the possibility that $CO_2$ gas sensor of semiconductor type can be detect the variation of $SF_6$ gas condition. The UHF sensor shows good feature to detect the variation of $SF_6$ gas condition for partial discharge and breakdown discharge.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.141-144
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• 2006

The deviations in the injection orbital parameters, resulting from launcher dispersions, need to be estimated and used for autonomous satellite operations. For the proposed small satellite mission of the university there will be two GPS receivers onboard the satellite to provide the instantaneous orbital state to the onboard data handling system. In order to meet the power requirements, the satellite will be sun-tracking whenever there is no imaging operation. For imaging activities, the satellite will be maneuvered to nadir-pointing mode. Due to such different modes of orientation the geometry for the GPS receivers will not be favorable at all times and there will be instances of poor geometry resulting in no output from the GPS receivers. Onboard the satellite, the orbital information should be continuously available for autonomous switching on/off of various subsystems. The paper presents the strategies to make use of small arcs of data from GPS receivers to compute the mean orbital parameters and use the updated orbital parameters to calculate the position and velocity whenever the same is not available from GPS receiver. Thus the navigation message from the GPS receiver, namely the position vector in Earth-Centered-Earth-Fixed (ECEF) frame, is used as measurements. As for estimation, two techniques - (1) batch least squares method, and (2) Kalman Filter method are used for orbit estimation (in real time). The performance of the onboard orbit estimation has been assessed based on hardware based multi-channel GPS Signal simulator. The results indicate good converge even with short arcs of data as the GPS navigation data are generally very accurate and the data rate is also fast (typically 1Hz).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.6
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• pp.1599-1606
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• 2008

Recently, new dispersed generation systems such as photovoltaic, wind power, fuel cell etc. are energetically interconnected and operated in the distribution systems, as one of the national projects for alternative energy with the provision against oil crisis. The technical guidelines on the interconnection of dispersed generation systems have been established and conducted positively. However, protection devices (Re-closer) in primary feeder of distribution system interconnected with photovoltaic generation may cause problems with mis-operation, and then many customers could have problems like an interruption. So, this paper presents the optimal method to minimize the impact of interruption, using both the symmetric method and MATLAB/SIMULINK. And, also this paper shows the effectiveness of proposed method by simulating at the real distribution systems.

• Journal of the Korean Institute of Gas
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• v.19 no.6
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• pp.22-27
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• 2015

Hydrogen features highest energy density per mass and is expected to be desirable as a fuel of HALE(High altitude long endurance) UAV(Unmanned aerial vehicle). A reciprocating internal combustion engine is known to be a reliable and economic power source for this kind of UAV. Therefore, the combination of hydrogen and engine is worth of doing research. Test bench with 2.4L Spark-Ignited engine was prepared for the experiment in which start and combustion characteristics at idle condition were examined in this study. Stable hydrogen supply system and a universal ECU(Engine control unit) were also utilized for the test engine. Equivalence ratio and spark timings at idle operation were investigated and compared to the data of gasoline engine. The results will be a starting point for full-scale research of hydrogen engine for HALE UAV.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.5
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• pp.79-86
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• 2014

A turbopump real-propellant test facility(TPTF) is to verify the performance of a turbopump unit(TPU) based on liquid oxygen and kerosene. One of the most important sub-facilities is a hot-gas generation system which makes the driving force of the TPU with an alcohol burner. The alcohol burner generates the required flow rates and temperature at the facility using high pressure air and ethanol. In the study, the verification tests of the alcohol burner which was manufactured entirely with domestic technology were performed and fabrication technique and operation skill for the burner could be obtained ahead of the construction of the facility. Two burners will be operated simultaneously for the real-propellant test of 75tf class turbopump and satisfy the power requirement from the turbine of the TPU.

• Korean Journal of Hazardous Materials
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• v.6 no.2
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• pp.77-86
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• 2018

Interest in renewable energy is increasing for eco-friendly use of energy, and fuel cells are being used in various ways such as houses and buildings as power generation methods that have low emissions such as $NO_X$ and $CO_2$. As the supply of fuel cells expands, more and more boilers are installed in the existing buildings, but safety management is not being performed properly. Therefore, in this study, a prior study was conducted on the status of fuel cell-boiler complex installation and related criteria, and the risk factors were analyzed according to the installation environment and structure. Based on these standards, the safety performance of the fuel cell-boiler combined installation is assessed by conducting a demonstration using the starting product of the simulated operation to derive the installation criteria (proposal) for the fuel cell-boiler combined installation. The installation criteria (proposal) include the construction and connection method of the piping according to the fuel cell-boiler complex installation.

• Journal of Engineering Education Research
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• v.24 no.5
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• pp.38-45
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• 2021

The CanSat was designed as an educational satellite simulation program that implements the overall system of the satellite such as the command processing unit, the communication unit, and the power unit in a structure of the size of a can. In particular, the training effect is very excellent because the trainee can learn a process similar to the actual satellite development process by designing, manufacturing, testing, and launching. Republic of Korea Air Force Academy has been using the CanSat production kit used by the domestic can satellite contest experience department for education, but since it was produced based on PCB, it was impossible to show creativity and operation was restricted even with small mistakes. In this paper, we analyze the existing CanSat kit and propose a new educational CanSat kit that can be used in creative engineering design and practice subjects that will be reorganized into a regular course from 2021, and a lesson plan. In conclusion, by using the proposed CanSat kit for lectures, it is possible to achieve educational purposes and effects, improve lecture satisfaction, and provide stable instruction.