• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.704-705
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• 2011

At present, the widely used wind power generators in the whole world are fixed speed induction generator (FSIG) and doubly fed induction generator (DFIG). The models of FSIG and DFIG wind power generation system connected with the grid are built, and their steady-state and transient characteristics are studied. A new coordinated control strategy using both the grid and rotor side converters of DFIG for voltage regultation and reactive power support is put forword to improve the steady-state and transient performance of the FSIG in the case of DFIG in parallel with FSIG.

• Journal of Advanced Marine Engineering and Technology
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• v.15 no.2
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• pp.73-83
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• 1991

A tracking controller which can improve the performance of nonlinear electrohydraulic position control systems is designed and implemented. The method is based on augmenting the system with both compensated integrator and additional integrator, obtaining the feedback control law which stabilizes the linear part of the original nonlinear system, and then readjusting the feedback gains using the describing function method to eliminate the limit cycle in the steady-state. The proposed control law is implemented using OP amplifiers and electronic components, and step and ramp response tests are carried out in the electrohydraulic servomechanism EHS-160. The results show the improvement in both transient and steady-state responses.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1994.04a
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• pp.437-450
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• 1994

The problem of testing for a change in the parameter of a stochastic process is particularly important in simulation studies. In studies of the steady state characteristics of a simulation model, it is important to identify initialization bias and to evaluate efforts to control this problem. A simulation output have the characteristics of chaotic behavior because of sensitive dependence on initial conditions. For that reason, we will apply Lyapunov exponent for diagnosis of chaotic motion to simulation output analysis. This paper proposes two methods for diagnosis of steady state in simulation output. In order to evaluate the performance and effectiveness of these methods using chaos theory, M/M/I(.inf.) queueing model is used for testing point estimator, average bias.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.4
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• pp.21-28
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• 1997

The vehicle handling performances have a close relation with the driver's safety. And the CAT(Computer aided testing) system has been introduced as a powerful tool for improving the handling performances. In this study, a CAT system for effectively measuring and analysing the handling performances is developed based on the windows GUI(Graphic user interface) environment. Especially, in order to derive a lot of significant handling performance parameters from a series of proving ground tests, the CAT system has various functions related to real time measurement, time domain analysis, frequency domain analysis, steady state analysis and so on.

• 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.

• Journal of Power Electronics
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• v.3 no.2
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• pp.90-98
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• 2003

This paper presents a performance analysis in steady-state of a novel type Auxiliary Resonant Commutation Snubber-linked 3-level 3-phase voltage source soft switching inverter suitable and acceptable for high-power applications in comparison with other three types of 3-level 3-phase voltage source soft switching inverters. This soft switching inverter operation which can operate under a condition of Zero Voltage Switching (ZVS). The practical steady -state performances of this inverter are illustrated and evaluated on the basis of the experimental results.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.344-352
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• 2006

Evacuation performance, starting transient, and plume blowback at diffuser breakdown of a straight cylindrical supersonic exhaust diffuser with no externally supplied secondary flow are investigated. Pressure records in the transitional periods are measured by a small-scale cold-gas simulator. Flow-fields evolving in the diffuser-type ejector are solved by preconditioned Favre-averaged Navier-Stokes equations with a low-Reynolds number $k-{\varepsilon}$ turbulence model edited for turbulence compressibility effects. The present RANS method is properly validated with measured static wall pressure distributions and evacuation level at steady operation as well as the pressure records during the transition regime.

• Journal of Industrial Technology
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• v.22 no.B
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• pp.3-12
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• 2002

Monte-Carlo simulation technique has advantages over deterministic simulation in various engineering analysis since Monte-Carlo simulation can take into consideration of scattering of various design variables, which is inherent characteristics of physical world. In this work, Monte-Carlo simulation of steady-state cornering behavior of a truck with design variables like hard points and busing stiffness. The purpose of the simulation is to improve understeer gradient of the truck, which exhibits a small amount of instability when the lateral acceleration is about 0.4g. Through correlation analysis, design variables that have high impacts on the cornering behavior were selected, and significant performance improvement has been achieved by appropriately changing the high impact design variables.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.23-26
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• 2007

Liquid water in flow channel is an important factor that limits the steady and transient performance of PEM fuel cells. A computational fluid dynamics study based on the volume-of-fluid (VOF) multi-phase model is conducted to understand the transport behavior of liquid water in flow channel. The liquid water transport in $180^{\circ}$ bends is investigated and the effect of chamfering is discussed. The effect of wall adhesion is also considered by varying the contact angle of channel surfaces. The result of this study is believed to provide a useful guideline for design optimization of flow patterns or channel configurations of PEM fuel cells.

• Journal of KSNVE
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• v.2 no.3
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• pp.213-222
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• 1992

The effect of cavitation on the synchronous steady state response of a single rotor supported on cavitated squeeze film dampers executing a circular orbit is investigated theoretically. The Swift-Stieber boundary conditions and a long bearing approximation are utillized to evaluate the direct and the cross coupled damping coefficients of a cavitated squeeze film damper. For typical design parameters, frequency response curves are presented here to exhibit the effect of cavitation on the imbalance response and transmissibilities for both a flexible rotor and a rigid rotor. Investigations show that cavitation occured in a squeeze film damper produces bistable jump phenomena and deteriorates the performance of a squeeze film damper. This arises from that the large cavity causes substantial increment of the cross coupled damping which has radial stiffening effect. Furthermore, the large cavity causes the decrement of the direct damping which has pure damping effect. It is also observed that in the absence of cavitation, both rotor excursion amplitude and imbalance transmissibilities are very well damped.