• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.12
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• pp.691-700
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• 1999

This paper proposes a novel switching strategy of 1Mvar STATCON using cascade multilevel H-bridge inverter(HBI) for FACTS application. To control the reactive power instantaneously, the d-q dynamic system model is described and analyzed. A single pulse pattern based on the SHEM(Selective Harmonic Elimination Method) technique is determined from the look-up table to reduce the line current harmonics and a rotating fundamental frequency switching scheme is presented to adjust the DC voltage of each inverter capacitor at the same value. So the voltage unbalance problem between separately DC bus voltage is improved by using the proposed switching scheme. As a result, the presented inverter configuration not only reduces the system complexity by eliminating the isolation at the AC input side transformer but also improves the dynamic response to the step change of reactive power.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.2
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• pp.261-266
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• 2015

Power system for renewable energy is composed of module, transform DC power into AC power inverter, control power flow and device for a charge of the grid-connected. Power system for renewable energy produce the most DC power, when this system is much insolation in summer and daytime. But if the certain temperature rises above, the essential grid-connected power inverter is take a nose dive. There, in this paper, we propose an improved reduction of heating system. In addition, selection of the most serious heat region and through analysis of temperature characteristics according to location and distance derive the optimal model.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.3
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• pp.367-372
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• 2008

In this paper we proposed a model of a fault diagnosis expert system with high reliability to compare identical well-functioning motors. The purpose of the survey was to determine if any differences exit among these identical motors and to identify exactly what these differences were, if in fact they were found. Using measured data for many identical brushless dc motors, this study attempted to find out whether normal and fault can be classified by each other. Measured data was analyzed using the State Transition Model (STM). Based on a proposed STM method, the effect of a different normal state is minimized and the detection of fault is improved in identical motor system. Experimental results are presented to prove that STM method could be a useful tool for diagnosing the condition of identical BLDE motors.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.2
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• pp.53-60
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• 2011

The available power generated from the FC power plant may not be sufficient to meet sustained load demand, peak demand or transient events. An supercapacitor bank(SCB) can supply a large burst of power, but it cannot store a significant amount of energy. The combined use of FC and SCB has the potential for the better energy efficiency, reducing the cost of FC technology and improved dynamic response. In this paper, A single PEMFC and PEMFC operated in parallel with a SC bank are presented, A new dynamic model of PEMFC system, the converter and controller has been developed for stand-alone applications. The simulation results are presented using Matlab/Simulink, and SimPowerSystems environments. It is confirmed that the results show a good performance and stable DC-link voltage for proposed dynamic and mathematical models developed for the combined FC/SCB.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.44 no.3
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• pp.8-15
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• 2007

Recently, it is important to process multimedia data efficiently. Especially, in case of retrieval of multimedia information, technique of user interface and retrieval technique are necessary. This paper proposes a new technique which detects cuts effectively in compressed image information by MPEG. A cut is a turning point of scenes. The cut-detection is the basic work and the first-step for video indexing and retrieval. Existing methods have a weak point that they detect wrong cuts according to change of a screen such as fast motion of an object, movement of a camera and a flash. Because they compare between previous frame and present frame. The proposed technique detects shots at first using DC(Direct Current) coefficient of DCT(Discrete Cosine Transform). The database is composed of these detected shots. Features are extracted by HMMD color model and edge histogram descriptor(EHD) among the MPEG-7 visual descriptors. And detections are performed in sequence by the proposed matching technique. Through this experiments, an improved video segmentation system is implemented that it performs more quickly and precisely than existing techniques have.

• International Journal of Control, Automation, and Systems
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• v.6 no.2
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• pp.186-193
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• 2008

The Internet's low cost and ubiquity present an attractive option for real-time distributed control of processes on the factory floor. When integrated with the Internet, the LonWorks open control network can give ubiquitous accessibility with the distributed control nature of information on the factory floor. One of the most important points in real-time distributed control of processes is timely response. There are many processes on the factory floor that require timely response. However, the uncertain time delay inherent in the network makes it difficult to guarantee timely response in many cases. Especially, the transmission characteristics of the LonWorks/IP network show a highly stochastic nature. Therefore, the time delay problem has to be resolved to achieve high performance and quality of the real-time distributed control of the process in the LonWorks/IP Virtual Device Network (VDN). It should be properly predicted and compensated. In this paper, a new distributed control scheme that can compensate for the effects of the time delay in the network is proposed. It is based on the PID controller augmented with the Smith predictor and disturbance observer. Designing methods for output feedback filter and disturbance observer are also proposed. Tracking position control experiment of a geared DC Servo motor is performed using the proposed control method. The performance of the proposed controller is compared with that of the Internal Model Controller (IMC) with the Smith predictor. The result shows that the performance is improved and guaranteed by augmenting a PID controller with both the Smith predictor and disturbance observer under the stochastic time delay in the LonWorks/IP VDN.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.76-79
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• 1988

The sliding mode control in an effective method to eatablish robustness against parameter variation and disturbance. But. In sliding mode strategy, the control function is discontinuous on the hyperplane. However the discontinuous change in control structure caves the controller input to chaffer and gives non-zero steady state error. Consequently, a multiloop feedback control system supplemented by a complelmentary controller is used to improved the drive performence of a DC servo motor and reduce sensitivity to parameter variation, nonlinear effects, and other disturbances.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.775-778
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• 1996

In this research, the robustness of a seam tracking for the automatic welding system is studied. The laser displacement sensor is used as a seam finder. X-Y moving table drived by ac servo motor controls the position and velocity of the torch-and-sensor part. However, dc servo motor is used to control the position and velocity of the torch. The sensor locates ahead of torch to preview the weld line, and brings about the inaccuracy on the torch tracking. To enhance the robustness on this system against the influence of disturbances and model uncertainty, H$\_$.inf./ control is applied to the angular motion of torch. The simulation shows that the tracking accuracy improved significantly. Also, experimental results give a good performance of H$\_$.inf./ control strategy to the automatic seam tracking system for the welding.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04c
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• pp.91-97
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• 2008

Polymers submitted to thermo/electrical stress suffer from ageing that can drastically affect their functional behaviour. Understanding the physico/chemical processes at play during ageing and defining transport regimes in which these mechanisms start to be critical is therefore a prime goal to prevent degradation and to develop new formulation or new materials with improved properties. It is thought that a way to define these critical regimes is to investigate under which conditions (in terms of stress parameters) light is generated in the material by electroluminescence (EL). This can happen through impact excitation/ionization involving hot carriers or upon bi-polar charge recombination (a definition that excludes light from partial discharges, which would sign an advanced stage in the degradation process). After a brief review of the EL phenomenology under DC, we introduce a numerical model of charge transport postulating a recombination controlled electroluminescence. The model output is critically evaluated with special emphasize on the comparison between simulated and experimental light emission. Finally, we comment some open questions and perspectives.

• Journal of Power Electronics
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• v.11 no.1
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• pp.37-44
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• 2011

In this paper, a four-phase 8/6-pole 4-kW SR motor drive model is presented. Based on experimental data, the model allows an accurate simulation of a drive in dynamic operation. Simulations are performed and a laboratory type set-up is built based on a TI TMS320F2812 platform to experimentally verify the theoretical results obtained for a SR motor. To reduce acoustic noise and to correct the power factor of this drive, a two-stage power converter is proposed that uses a current source rectifier (CSR) as the input stage for the asymmetrical converter of the studied SRM. Employing the space-vector modulation (SVM) method in matrix converters, the CSR switching allows the dc link's capacitors to be eliminated and the power factor of the SRM drive to be improved. As the electrical motive force (emf) is directly proportional to the rotor speed, the input voltage to the machine can be programmed to be a function of the speed with the modulation index of the CSR, leading to a reduction in the acoustic noise of the SRM drive. Simulation of the whole SRM drive system is performed using MATLAB-Simulink. The results fully comply with the required conditions such as power factor correction with an improvement in the THD.