• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.9
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• pp.1483-1492
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• 2001

A robust optimization procedure is applied to determine the design of the laminated composite plates with buckling constraints. In order to investigate the variation effect to the whole performance of a structure, both design variables and system parameters are assumed as random variables about their nominal values. The robust optimization method has advantages that the mean value and the variation of the performance function are controlled simultaneously and the second order sensitivity information is not required. Considering the information of uncertainty, robust optima for the buckling load of the laminated composite plates with cut-out is obtained. The robustness of the structures is compared to that of the deterministic optimization using scaling factors.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.90-94
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• 1998

The parallel inverter is popularly used because of its fault-tolerance capability, high-current outputs at constant voltages and system modularity. The conventional parallel inverter usually employes active and reactive power control or frequency and voltage droop control. However, these approaches have the disadvantages that the response time of parallel inverter control is slow against load and system parameter variation to calculate active, reactive power, frequency and voltage. This paper describes a novel control scheme for power equalization in parallel connected inverter. The proposed scheme has a fast power balance control response, a simplicity of implementation, and inherent peak current limiting capability since it employes a instantaneous current/voltage control with output voltage and current balance and output voltage regulation. A design procedure for the proposed parallel inverter controller is presented. Futhermore, the proposed control scheme is verified through the simulation in various cases such as the system parameter variation, the control parameter variation and the nonlinear load condition.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.176-181
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• 1998

The parallel inverter is popularly used because of its fault-tolerance capability, high-current outputs at constant voltages and system modularity. The conventional parallel inverter usually employs active and reactive power control of frequency and voltage droop control. However, these approaches have the disadvantages that the response time of parallel inverter control is slow against load and system parameter variation to calculate active, reactive power, frequency and voltage. This paper describes a novel control scheme for power equalization in parallel-connected inverter. The proposed scheme has a fast power balance control response, a simplicity of implementation, and inherent peak current limiting capability since it employees an instantaneous current/voltage control with output voltage and current balance and output voltage regulation. A design procedure for the proposed parallel inverter controller is presented. Furthermore, the proposed control scheme is verified through the experiment in various cases such as the system parameter variation, the control parameter variation and the nonlinear load condition.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1056-1058
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• 2000

Deadbeat technique has been proposed as a digital controller for an UPS inverter to achieve the fast response to a load variation and to conserve a very low THD under a nonlinear load condition. This scheme contains a fatal drawback, sensitivity against parameter variation and calculation time delay. This paper proposes a second order deadbeat current controller, which fundamentally solves the calculation time delay problem and certainly guarantees the robustness of the parameter's variation. This is shown theoretically and practically through simulation and experiment.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.184.2-184.2
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• 2010

This study performs modelling and simulation of permanent magnetic synchronous generator wind turbine by using Matlab & Simulink. In simulation, change of wind velocity, change of load, and voltage decrease of infinite bus are performed. Through such simulation, different with wiring system that there is only existing load, this study can confirm problems and voltage changing characteristics, which can occur in distributed electric power that load and electric power is mixed and operated, especially, in interconnecting with wind power generation.

• Tribology and Lubricants
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• v.11 no.2
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• pp.44-55
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• 1995

Frictional characteristics with the change of dynamic parameters, such as stiffness, inertia and damping, in the friction measurement at dry sliding surfaces were experimentally and theoretically investigated throughout the study. Dynamic frictional force and the variation in the normal load were mainly measured at the various conditions of system dynamic parameters with which stiffness in the normal direction, loading mechanisms and test materials were varied. For the normal load, mechanisms using both a dead weight and a pneumatic cylinder were applied, which resulted in change of the inertia and damping of the test rig. Test materials were steel, rosin and PTFE, which have different types of intrinsic frictional characteristics. Test results showed that frictional characteristics under different dynamic parameters could be different even though the operating variables were the same and also they could result in the variation in the normal load, which could consequently affect the wear mechanism.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.4
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• pp.267-273
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• 2017

In recent years, there is an increasing demand for DC microgrid because the digital load due to DC increases and the efficiency of the distribution system increases due to loss of conversion losses and conversion stages due to reactive power compared to AC distribution. Currently, with the support of the KEPRI, the development of an electronic large-capacity circuit breaker for DC distribution protection, which has been underway since 2016, is proceeding. In this paper, as a part of this project, we modeled the DC microgrid connected with PV using PSCAD. The converter station, AC/DC converter control, PV and MPPT controller are designed. In order to evaluate the performance of the modeled DC microgrid, it is examined whether the voltage is adjusted according to the load variation.

• Journal of Energy Engineering
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• v.22 no.2
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• pp.205-210
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• 2013

Cycle-to-cycle variation has long been recognized as limiting the range of operating conditions of spark ignition engines, in particular, under lean and highly diluted operation conditions. At a part load, some of the cycles tend to knock, while others may have incomplete combustion by the time the exhaust valve opens. An experimental study has been performed in order to evaluate the relative contribution of several relevant parameters on the cyclic variability in spark ignition engines. In general, the stability of engine operation is improved with fuel injector according to the optimal injection timing, but the stability of engine operation at idle is not improved compared with a practical gasoline engine. In this study, we investigated the relationship of the effect of operating conditions for the stability at low speed and load.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.87-91
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• 2004

In this paper, the paralleled forward converter, that is generally used as the power supply for the low voltage, high current load, is described. The proposed forward converter for battery charging could be provided the power without failure not only in steady state but also in the transient period by the step load variation or the unexpected faults among the converter modules. Each converter nodule designed is operated alone with the self closed controller for the elevation of stability, performance, reliability, and maintainability. The frequency response of the designed converter module is analyzed, and the stability is confirmed in analytic method. And the experiments of the paralleled battery charger are carried out in steady state, in the step load variation.

• Transactions of Materials Processing
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• v.21 no.2
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• pp.89-95
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• 2012

To examine the deformation characteristics of round aluminum pipe under biaxial compression, a horizontal biaxial compression die was fabricated. The change of material properties, punch load and deformation behavior were monitored in experiments using various compressive deformation rates in the range of 1mm/min.~400mm/min. The tensile and compressive strains were estimated from Vickers microhardness results. The punch load and deformation characteristic of the round aluminum pipes were found to change greatly at a deformation rate of about 200mm/min. The punch load decreased with increasing compressive deformation rate. Results of numerical simulation using Deform-2D were in good agreement with experimental results, and the measured hardness variation with the strain variation was predicted well by the simulation.