• The KIPS Transactions:PartA
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• v.14A no.2
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• pp.125-132
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• 2007

Recently, in the engineering area, there is an increasing need for researchers at a distance to share the result of the experiment, without having to visit the experiment facilities. Especially in the civil engineering, researchers feel the need for participating in a experiment conducted at a distant location. In addition, it is suggested that high-cost facilities should be used by remote researchers thereby increasing the utilization rate. This paper proposes a remote experiment environment in civil engineering that are being developed in a project called Korea Construction Engineering Development(KOCED), which connects major civil engineering experiment facilities using grid technology, allows researchers to participate in a remote experiment, and has the experiment results shared by remote researchers automatically. Then, based on the suggested environment, we designed a hybrid test facility that involves two physical experiment facility sites and one numerical simulation site that are geographically apart. Then, we implemented its prototype and ran some tests, which showed a possibility of grid-based civil engineering experiment.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.6
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• pp.91-97
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• 2018

This paper presents implementation possibilities of digital IoT doorlock systems via VLC(Visible Light Communication)'s color grid. The color grid-based VLC modulation scheme which are discussed in this paper utilize the straightness of light and abundant frequency resources which are the properties of the light. Performance results in this paper are compared to that of conventional modulations with Bit Error Rate (BER) and Signal to Noise Ratio (SNR) simulations. With respect to a channel model, the proposed modulation schemes select the nearest Line Of Sight (LOS) except Non Line Of Sight (NLOS). Experiments in this paper show error rates of received symbols by changing power dB at a distance of 3m between Tx and Rx in an indoor environment. Through performance results and experiments, this paper demonstrates superiority of the proposed color grid-based modulation schemes.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.2
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• pp.187-192
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• 2019

Hybrid power storage system with emergency power function for demand management and power outage minimizes the investment cost in the building of buildings and factories requiring emergency power generation facilities, We propose a new business model by developing technology that can secure economical efficiency by reducing power cost at all times. Normally, system power is supplied to load through STS (Static Transfer Switch), and PCS is connected to system in parallel to perform demand management. In order to efficiently operate the electric power through demand forecasting, the EMS issues a charge / discharge command to the ESS as a PMS (Power Management System), and the PMS transmits the command to the PCS controller to operate the system. During the power outage, the STS is rapidly disengaged from the system, and the PCS becomes an independent power supply and can supply constant voltage / constant frequency power to the load side. Therefore, it is possible to secure reliability through verification of actual system linkage and independent operation performance of hybrid ESS, By enabling low-carbon green growth technology to operate in conjunction with an efficient grid, it is possible to improve irregular power quality and contribute to peak load by generating renewable energy through ESS linkage. In addition, the ESS is replacing the frequency follow-up reserve, which is currently under the charge of coal-fired power generation, and thus it is anticipated that the operation cost of the LNG generator with high fuel cost can be reduced.

• Journal of Communications and Networks
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• v.14 no.6
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• pp.662-671
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• 2012

Plug-in hybrid electric vehicles (PHEVs) will be widely used in future transportation systems to reduce oil fuel consumption. Therefore, the electrical energy demand will be increased due to the charging of a large number of vehicles. Without intelligent control strategies, the charging process can easily overload the electricity grid at peak hours. In this paper, we consider a smart charging and discharging process for multiple PHEVs in a building's garage to optimize the energy consumption profile of the building. We formulate a centralized optimization problem in which the building controller or planner aims to minimize the square Euclidean distance between the instantaneous energy demand and the average demand of the building by controlling the charging and discharging schedules of PHEVs (or 'users'). The PHEVs' batteries will be charged during low-demand periods and discharged during high-demand periods in order to reduce the peak load of the building. In a decentralized system, we design an energy cost-sharing model and apply a non-cooperative approach to formulate an energy charging and discharging scheduling game, in which the players are the users, their strategies are the battery charging and discharging schedules, and the utility function of each user is defined as the negative total energy payment to the building. Based on the game theory setup, we also propose a distributed algorithm in which each PHEV independently selects its best strategy to maximize the utility function. The PHEVs update the building planner with their energy charging and discharging schedules. We also show that the PHEV owners will have an incentive to participate in the energy charging and discharging game. Simulation results verify that the proposed distributed algorithm will minimize the peak load and the total energy cost simultaneously.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1625-1636
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• 2017

A power electronic transformer (PET) based on the cascaded H-bridge (CHB) and the isolated bidirectional DC/DC converter (IBDC) is capable of accommodating a large scale battery energy storage system (BESS) in the medium-voltage grid, and is referred to as a power electronic transformer based battery energy storage system (PET-BESS). This paper investigates the PET-BESS and proposes a coordinative control strategy for it. In the proposed method, the CHB controls the power flow and the battery state-of-charge (SOC) balancing, while the IBDC maintains the dc-link voltages with feedforward implementation of the power reference and the switch status of the CHB. State-feedback and linear quadratic Riccati (LQR) methods have been adopted in the CHB to control the grid current, active power and reactive power. A hybrid PWM modulating method is utilized to achieve SOC balancing, where battery SOC sorting is involved. The feedforward path of the power reference and the CHB switch status substantially reduces the dc-link voltage fluctuations under dynamic power variations. The effectiveness of the proposed control has been verified both by simulation and experimental results. The performance of the PET-BESS under bidirectional power flow has been improved, and the battery SOC values have been adjusted to converge.

• Journal of the Korean Solar Energy Society
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• v.24 no.4
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• pp.1-10
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• 2004

In view of global environmental problems and resource exhaustion, we must develop new energy resources that are abundant and provide substitutes for fossil fuels. Renewable energies, such as solar, are ideal because they are clean, inexhaustible, and available everywhere in the world. Photovoltaic(PV) system, in general, are operated as a stand-alone, grid-tied, or hybrid system. Many of the stand-alone PV systems are installed. Although the pre-installation cost of PV system is high, it poorly has been operated due to the absence of optimal management standards. Therefore a study on the performance of PV system is important for the system design and maintenance. In this paper a photovoltaic lighting system was resigned according to load consumption. Then a PV lighting system which used electrodeless lamp as a load was installed. In order to investigate the system operating characteristics we've added a monitoring system to the PV lighting system. The monitoring system using the LabVIEW program regularly checks the operation of the PV lighting system and records the system data. According to the system data, the stability and availability of the PV lighting system were evaluated.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.511-515
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• 2012

At the moment, with an interest in renewable energy sources (RES) that continue to grow its penetration will be expected to considerably increase in the future power system. However, this penetration of RES leads to new challenges to be solved in electric power systems. In this paper, optimal configuration of renewable energy resources and operation strategy is presented. By using this methodology for allocation of the optimal sizes and types, system operational efficiency and stability of the microgrid will be maximized.

• Journal of Ocean Engineering and Technology
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• v.11 no.4
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• pp.141-151
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• 1997

This paper deals with a numerical study of flow-guider applied to controlling current in a bay. Two dimensional numerical model for tidal currents based on the depth averaged equation is developed and standard k-.epsilon. model is adopted to determine the turbulence diffusion. Equations are described in a generalized coordinate system to be implemented by non-staggered grid system and discretized by using finite volume method. Unsteady flow is simulated by fully implicit scheme. Hybrid scheme and central differencing are used to compute the convective terms and source terms, respectively. The tidal current in a rectangular bay is simulated and it gives satisfactory results. The realistic and distinct models of a large structure placed in bay are also exemplified with or without flow-guiders. The simulation results show that the flow-guider gives the residual tidal current in the bay by the different flux with respect to the direction of tidal current.

• 한국전산유체공학회:학술대회논문집
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• 1996.05a
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• pp.27-32
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• 1996

A previously developed pressure based calculation procedure for incompressible flows was modified and applied to transonic and supersonic flows. It uses pressure as a primary variable in preference to density and body fitted coordinate and non-staggered grid system. The discretized momentum equations were rearranged as a system of equations with respect to covariant velocity components. Three different discretization schemes, QUICK hybrid and first order upwind, were used to approximate the convective terms and compared. Present approach was tested far two transonic flow and one supersonic flow problems. Comparison with previous results show that present approach can be used as a solver for compressible flows.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.366-366
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• 2000

In this paper, an adaptive neuro-fuzzy filter using the conditional fuzzy c-means(CFCM) methods is proposed. Usualy, the number of fuzzy rules exponentially increases by applying the grid partitioning of the input space, in conventional adaptive neuro-fuzzy inference system(ANFIS) approaches. In order to solve this problem, CFCM method is adopted to render the clusters which represent the given input and output data. Parameter identification is performed by hybrid learning using back-propagation algorithm and total least square(TLS) method. Finally, we applied the proposed method to the nonlinear channel equalization problem and obtained a better performance than previous works.