• Journal of Electrical Engineering and Technology
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• v.3 no.4
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• pp.499-508
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• 2008

Frequency regulation in off-normal conditions has been an important problem in electric power system design/operation and is becoming much more significant today due to the increasing size, changing structure and complexity of interconnected power systems. Increasing economic pressures for power system efficiency and reliability have led to a requirement for maintaining power system frequency closer to nominal value. This paper presents a decentralized frequency control framework using a modified low-order frequency response model containing a proportional-integral(PI) controller. The proposed framework is suitable for near-normal and emergency operating conditions. An $H_{\infty}$ control technique is applied to achieve optimal PI parameters, and an analytic approach is used to analyse the system frequency response for wide area operating conditions. Time-domain simulations with a multi-area power system example show that the simulated results agree with those predicted analytically.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.1
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• pp.59-67
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• 1997

This paper gives a controller design method by Linear Matrix Inequality(LMI) for internal combustion engine with Continuously Variable Transmission(CVT) which satisfies the given $H_\infty$ control performance and robust stability in the presence of physical parameter perturbations. To the end, the validity and applicability of this approach are illustrated by simulation in the all engine operating regions.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.53 no.4
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• pp.161-165
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• 2004

This thesis proposes a robust controller introducing the $H_{\infty}$ control theory, one of the robust control theories that can obtain desired control performance while ensuring robustness for the uncertainty and disturbance contained in the power system. This thesis also proposes an improved digital exciter control system for a synchronized generator using a digitally designed controller. Simulation to verify the usefulness of the proposed method was carried. Results show that the proposed control system manifests excellent control performance compared to existing control systems.

• Journal of Electrical Engineering and information Science
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• v.3 no.2
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• pp.158-162
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• 1998

We study the decentralized stabilization problem of linear time-invariant large-scale interconnected systems with delays without any system structure. We obtain sufficient stability conditions for interconnected systems which are equivalent to disturbance attenuation of some scaled system. A decentralized output-feedback controller is obtained using standard H$\infty$ control theory. The obtained controller is delay-independent. We also obtain an observer for the interconnected system.

• Proceedings of the KIEE Conference
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• 2000.11d
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• pp.653-656
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• 2000

This paper presents an application of $H_\infty$ control design for a magnetic suspension system which has strongly nonlinearity and parameter variations. The designed controller is tested by numerical simulations and experiments.

• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.103-105
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• 1995

In this paper, though Simith controller is also used, we propose a new system configuration which can be regarded an SISO continuous nth-order plant with time delay of k-times of a sampling period as a linear discrete (n + k)th order plant of which all state variables can be available. Consequently, we can pply linear control system design techniques which do not consider the existence of time delay to the proposed system.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.4
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• pp.349-349
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• 1996

The ship's propulsion efficiency depends upon a combibation of engine and propeller. The propeller has better efficiency as the engine has lower rotational speed. This situation led the engine manufacures to design the engine that has lower speed, longer stroke and a small number of cylinders. With this new trends the conventional mechanical-hydrualic governors for engine speed control have been replaced by digital speed controllers which adopted the PID control or the optimal control algorithm. But these control algorithms have not enough robustness to suppress the variations of the delay-time and the parameter perturbation especially in low speed engine. In this study we consider the perturbations of the engine parameters as the modeling uncetainties and design a robust speed controller for marine medium speed diesel engine by means of $ extit{H}_{infty}$control theory having the central solution. By comparing the results of the robust speed controller with those of mechanical governor and PID controller, the validity of the robust speed controller under parameter variations is confirmed. The speed control of the experimental diesel engine of carried out using actuator which is composed of PWM signal generator and D.C servo motor.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.95.3-95
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• 2001

This paper investigates the simultaneous use of mixed H2/H_inf and mu-synthesis design methodology to design a robust controller for flexible link. We adopt four steps to design control system as follows: Step 1 : Generally, there are differences between the nominal and real model, so we consider the plant as a combination of parametric model uncertainty and unstructured uncertainty represents real structural uncertainties associated with the damping ratios of the flexible modes retained in the nominal model without payload. denotes the uncertainty which is due to the payload added at the tip. Step 2 : We adopt the mixed H2/H_inf theory to design a feedback controller K(s) by using the model uncertainty ...

• Journal of Ocean Engineering and Technology
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• v.17 no.5 s.54
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• pp.57-65
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• 2003

This paper proposes an optimum design method of structural and control systems, using a 2-D truss structure as an example. The structure is subjected to initial static loads and disturbances. For the structure, a FEM model is formed. Using modal transformation, the equation of motion is transformed into modal coordinates, in order to decrease D.O.F. of the FEM model. To suppress the effect of the disturbances, the structure is controlled by an output feedback $H_{\infty}$ controller. The design variables of the combined optimal design of the control-structure systems are the cross sectional areas of truss members. The structural objective function is the structural weight. The control objective function is the $H_{\infty}$ norm, the performance index of control. The second structural objective function is the energy of the response related to the initial state, which is derived from the time integration of the quadratic form of the state in the closed-loop system. In a numerical example, simulations have been perform. Through the consideration of structural weight and $H_{\infty}$ norm, an advantage of the combined optimum design of structural and control systems is shown. Moreover, since the performance index of control is almost nearly optimiz, we can acquire better design of structural strength.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.7
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• pp.559-566
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• 2001

The sway control problem of the pendulum motion of a container hanging on the trolly, which transports containers from a container ship to trucks, is considered in the paper. In the container crane control problem, suppressing the residual swing motion of the container at the end of acceleration, deceleration or the case of that the unexpected disturbance input exists is main issue. For this problem, in general, the trolley motion control strategy is introduced and applied. In this paper, we introduce and synthesize a new type of swing motion control system in which a small auxiliary mass is installed on the spreader. The actuator reacting against the auxiliary mall applies inertial control forces to the container to reduce the swing motion in the desired manner. In this paper, we apply the $H^{\infty}$ based gain-scheduling control technique to the anti-swing motion control system design problem of the controlled plant. In this control system, the controller dynamics are adjusted in real-time according to time-varying plant parameters. And the simulation result shows that the proposed control strategy is shown to be useful for the case of time-varying system and, robust to disturbances such as winds and initial sway motion.