• Journal of Drive and Control
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• v.11 no.3
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• pp.22-30
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• 2014

In this research, the energy stability level method is used for examining the stable state of Field Robot under effects of swing motion, at particular postures of manipulator, and terrain conditions. The energy stability level is calculated by using the dynamic models of Field Robot, subjected to the concept of equilibrium plane and support boundary. The results, simulated by using computing program for estimating the potential overturning of Field Robot, supply useful predictions of stability analysis for designers and operators.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.412-413
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• 2011

This paper presents a new generation rescheduling approach for preventive control of power systems, which can optimally reallocate power generations for unstable contingencies. The transient stability constraints used in the optimal rescheduling model are described by energy margin sensitivity. Especially the energy margin sensitivity is evaluated for change with respect to generation. For a given contingency, the energy margin is computed and the respective sensitivities are also computed.

• Journal of Energy Engineering
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• v.7 no.1
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• pp.65-72
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• 1998

This paper presents a fast calculation method for evaluating of voltage stability margin (MW) using the line flow equation in polar form. Here, Line flow equations $(P_{ij},\;Q_{ij}$ are comprised of state variable, $V_i,\;{\Delta}_i,\;V_j$ and ${Delta}_j$, and line parameter, r and x. using the feature of polar coordinate, these becomes one equation with two variables, $V_j,;V_j$. Moreover, if bus j is slack or generator bus, which is specified voltage magnitude in load flow calculation, it becomes one equation with one variable $V_ i $ that is, may be formulated with the second-order equation for $V^2_i$. Therefore, multiple load flow solutions may be obtained with simple computation. The obtained load flow multiple solutions are used for evaluating of voltage stability through sensitivity analysis or its closeness. Also, the method is proposed to calculate for voltage stability margin considering shunt capacitor, which is important element for evaluating of voltage stability. The proposed method was validated to sample systems.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2001.02a
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• pp.53-56
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• 2001

The stability of PF 6-7 has been studied according to the transient analysis code TOKSCPF and quench analysis code QSAIT. We compare the stability and temperature rise with various Cu/SC ratios of 2.8 and 3.5 under the KSTAR normal operating conditions. It shows that the Cu/SC ratio has an influence on the quench propagation and stability margin. In transient operating condition, the Cu/SC ratio weakly influences on the temperature rise in PF magnet.

• Journal of Electrical Engineering and Technology
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• v.8 no.3
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• pp.478-489
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• 2013

The controllability and stability of power systems can be increased by Flexible AC Transmission Devices (FACTs). One of the FACTs devices is Interline Power-Flow Controller (IPFC) by which the voltage stability, dynamic stability and transient stability of power systems can be improved. In the present paper, the convenient operation and control of IPFC for transient stability improvement are considered. Considering that the system's Lyapunov energy function is a relevant tool to study the stability affair. IPFC energy function optimization has been used in order to access the maximum of transient stability margin. In order to control IPFC, a Brain Emotional Learning Based Intelligent Controller (BELBIC) and PI controller have been used. The utilization of the new controller is based on the emotion-processing mechanism in the brain and is essentially an action selection, which is based on sensory inputs and emotional cues. This intelligent control is based on the limbic system of the mammalian brain. Simulation confirms the ability of BELBIC controller compared with conventional PI controller. The designing results have been studied by the simulation of a single-machine system with infinite bus (SMIB) and another standard 9-buses system (Anderson and Fouad, 1977).

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1566-1577
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• 2018

This paper presents a stability analysis of AC-DC power system feeding a speed controlled DC motor in which this load behaves as a constant power load (CPL). A CPL can significantly degrade power system stability margin. Hence, the stability analysis is very important. The DQ and generalized state-space averaging methods are used to derive the mathematical model suitable for stability issues. The paper analyzes the stability of power systems for both speed control natural frequency and DC-link parameter variations and takes into account controlled speed motor dynamics. However, accurate DC-link filter and DC motor parameters are very important for the stability study of practical systems. According to the measurement errors and a large variation in a DC-link capacitor value, the system identification is needed to provide the accurate parameters. Therefore, the paper also presents the identification of system parameters using the adaptive Tabu search technique. The stability margins can be then predicted via the eigenvalue theorem with the resulting dynamic model. The intensive time-domain simulations and experimental results are used to support the theoretical results.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.7
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• pp.337-344
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• 2005

An energy function is derived on the basis of the EMM(Equivalent Mechanical Model) to take account of the effects of tap changer, and then the VC(Voltage Collapse) criteria is proposed to predict the voltage collapse in Power systems. The VC criterion can be evaluated by using the energy margin given by the energy gap between UEP(Unstable Equilibrium Point) and SEP(Stable Equilibrium Point) of the energy function adopted, in which it is noted that the energy contour should be considered due to energy discontinuity associated with tap changing. This paper shows that the proposed VC criterion improves the accuracy of voltage stability analysis with application to a two-bus sample system.

• Journal of Power Electronics
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• v.15 no.1
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• pp.202-215
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• 2015

This paper investigates the stability and performance of model predictive controlled active-front-end (AFE) rectifiers for energy storage systems, which has been increasingly applied in power distribution sectors and in renewable energy sources to ensure an uninterruptable power supply. The model predictive control (MPC) algorithm utilizes the discrete behavior of power converters to determine appropriate switching states by defining a cost function. The stability of the MPC algorithm is analyzed with the discrete z-domain response and the nonlinear simulation model. The results confirms that the control method of the active-front-end (AFE) rectifier is stable, and that is operates with an infinite gain margin and a very fast dynamic response. Moreover, the performance of the MPC controlled AFE rectifier is verified with a 3.0 kW experimental system. This shows that the MPC controlled AFE rectifier operates with a unity power factor, an acceptable THD (4.0 %) level for the input current and a very low DC voltage ripple. Finally, an efficiency comparison is performed between the MPC and the VOC-based PWM controllers for AFE rectifiers. This comparison demonstrates the effectiveness of the MPC controller.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.136-139
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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 due to more various operating conditions. 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.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.274-276
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• 2005

Stability is an important constraint in powr system operation. A new methodology that reduces the need for repeated simulation to determine a transiently secure operating point is presented. at cntingency, critical generator is limited generation to prevent rotor accelation until system is secured. when energh margin is zero, generation is degermined Implementation issues and simulation results are discussed in th context of a 10-bus system.