• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.20-28
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• 2016

This paper presents a generation rescheduling method for the enhancement of transient stability in power systems. The priority and the candidate generators for rescheduling are calculated by using the energy margin sensitivity. The generation rescheduling formulates the Lagrangian function with the fuel cost and emission such as NO_x and SO_x from power plants. The generation rescheduling searches for the solution that minimizes the Lagrangian function by using the Newton’s approach. While the Pareto optimum in the fuel cost and emission minimization has a drawback of finding a number of non-dominated solutions, the proposed approach can explore the non-inferior solutions of the multiobjective optimization problem more efficiently. The method proposed is applied to a 4-machine 6-bus system to demonstrate its effectiveness.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.9
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• pp.441-448
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• 2005

On-line dynamic security assessment is becoming more and more important for the stable operation of power systems as load level increases. The necessity is getting apparent under Electricity Market environments, as operation of power system is exposed to more various operating conditions. For on-line dynamic security assessment, fast transient stability analysis tool is required for contingency selection. The TEF(Transient Energy Function) method is a good candidate for this purpose. The clustering of critical generators is crucial for the precise and fast calculation of energy margin. In this paper, we propose a new method for fast decision of mode of instability by using stability indices. Case study shows very promising results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.7
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• pp.1123-1128
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• 2008

The necessity of online dynamic security assessment is getting apparent under Electricity Market environments, as operation of power system is exposed to more various operating conditions. For on-line dynamic security assessment, fast transient stability analysis tool is required for contingency selection. The TEF(Transient Energy Function) method is a good candidate for this purpose. The clustering of critical generators is crucial for the precise and fast calculation of energy margin. In this paper, we propose a new method for fast decision of mode of instability by using stability indices and energy margin. The method is a new version of our previous paper.[1] Case studies are showing very promising results.

• Progress in Superconductivity
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• v.8 no.2
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• pp.193-201
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• 2007

Since the margins for the minimum quench energy and for the operating current in the superconducting magnet determine the operating regime of the magnet, a thermal stability analysis for the KSTAR superconducting magnet system is performed using 1-D Gandalf code. The result shows that the minimum quench energy is about 500 mJ/cc and the operating current margin is about 70 %. These values are larger than those of the KSTAR design criteria and the KSTAR superconducting magnet system can be operated stably under various experimental environments.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.1
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• pp.1-6
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• 2006

The emergence of competitive power market makes dispatch algorithm with transient stability constraints increasingly important for the transparent power system operation. Heuristic and off-line evaluation for the operation point can produce a discrimination among market players in the deregulated power system. In this paper, a dispatch algorithm with transient stability constraints is proposed. Energy margin under the TEF(Transient Energy Function) structure is adopted as a measure for the stability index. Implementation issues and simulation results are discussed in the context of a 10-bus system

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.9
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• pp.959-966
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• 2009

An essential consideration when analyzing the gait of walking robots is their ability to maintain stability during walking. Therefore, this study proposes a vertical waist-jointed walking robot and gait algorithm to increase the gait stability margin while walking on the slope. First, the energy stability margin is compared according to the posture of the walking motion on slope. Next, a vertical waist-jointed walking robot is modeled to analyze the stability margin in given assumption. We describe new parameters, joint angle and position of a vertical waist-joint to get COG (center of gravity of a body) in walking. Finally, we prove the superiority of the proposed gait algorithm using simulation and conclude the results.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.6
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• pp.274-283
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• 2005

This paper presents a new method to derive energy function based on vector product. Using this method, an energy function to consider transfer conductances and capacitors is derived. Then we recommend a voltage collapse criteria to predict the voltage collapse in power systems by using the energy margin derived by the proposed energy function. This energy function is applied to a 2-bus power system reflecting transfer conductances and capacitors. We show that the energy function derived based on vector product can be applied in order to analyze power system stability and the energy margin can be utilized as a criterion of voltage collapse by simulation for the 2-bus system.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.11
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• pp.1665-1674
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• 2013

In this paper, we propose a genetic algorithm(GA) based locomotion method of a quadruped robot with waist joint, which makes a quadruped robot walk on the slop efficiently. In the proposed method, we first derive the kinematic model of a quadruped robot with waist joint and then set the gene and the fitness function for GA. In addition, we determine the best attitude for a quadruped robot and the landing point of a foot in the walk space, which has the optimal energy stability margin(ESM). Finally, we verify the effectiveness of the proposed method by comparing with the performance of the previous method through the computer simulations.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.9
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• pp.1605-1610
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• 2010

In this paper, the relative stability of magnetic bearing system for the flywheel energy storage is evaluated using both simulation and experimental analysis. We make the simulation model for the magnetic bearing flywheel system using the rigid body shaft model. According to international standard ISO 14839-3, We experimentally analyzed the relative stability of magnetic bearing system. Additionally using both the simulation model and experimental tests, Phase margin and Gain margin is acquired through Nyquist plot.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.77-79
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• 1996

This paper presents an integrated stability analysis by the direct energy function method based on Equivalent Mechanical Model(EMM) which reflects the system behavior related to both angle and voltage stabilities. Actually, angle and voltage stability are intimately related in power system, so complete decoupling of these stability analysis is not possible in general, particularly in stressed power systems. In this paper, it is shown that a identical energy function can be used for angle and voltage stability analysis. The proposed energy function reflects the line resistances and reactive powers under the constraints of the same R/X ratio. The energy margin between UEP and SEP presents a good collapse proximity index in both types of stability analysis.