• Journal of Electrical Engineering and Technology
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• v.8 no.5
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• pp.991-1001
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• 2013

Instead of building new substations or transmission lines, proper installation of flexible AC transmission systems (FACTS) devices can make the transmission networks accommodate more power transfers with less expansion cost. In this paper, the problem to maximize power system loadability by optimally installing two types of FACTS devices, namely static var compensator (SVC) and thyristor controlled series compensator (TCSC), is formulated as a mixed discrete-continuous nonlinear optimization problem (MDCP). To reduce the complexity of the problem, the locations suitable for SVC and TCSC installations are first investigated with tangent vector technique and real power flow performance index (PI) sensitivity factor and, with the specified locations for SVC and TCSC installations, a set of schemes is formed. For each scheme with the specific locations for SVC and TCSC installations, the MDCP is reduced to a continuous nonlinear optimization problem and the computing efficiency can be largely improved. Finally, to cope with the technical and economic concerns simultaneously, the scheme with the biggest utilization index value is recommended. The IEEE-14 bus system and a practical power system are used to validate the proposed method.

• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1258-1268
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• 2014

Improving grid connection of wind farms is a relevant issue to be addressed, especially for fixed-speed wind turbines. Certain elements, such as FACTS (Flexible AC Transmission Systems), are able to perform voltage and reactive power regulation in order to support voltage stability of wind farms, and compensate reactive power consumption from the grid. Several devices are grouped under the name of FACTS, which embrace different technologies and operating principles. Here, three of them are evaluated and compared, namely STATCOM (Static Synchronous Compensator), SVC (Static Var Compensator) and SSSC (Static Synchronous Series Compensator). They have been modeled in MATLAB/Simulink, and simulated under various scenarios, regarding both normal operation and grid fault conditions. Their response is studied together with the case when no FACTS are implemented. Results show that SSSC improves the voltage stability of the wind farm, whereas STATCOM and SVC provide additional reactive power.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.159-160
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• 2006

This paper discusses sensitivity analysis for determining adequate locations of series-type FACTS devices. The main objective of FACTS reinforcement is to alleviate line over-loadings against violation of thermal limits after disturbances. This paper, to obtain the information concerning series-type FACTS locations, proposes a formulation for the sensitivity of the PI (Performance Index) with respect to the variation of the branch parameters, and applies to 5-bus test system to show the effectiveness of the sensitivity.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.11
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• pp.1429-1433
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• 1999

This paper proposes the FACTS site selection method using subtransmission system reduction. A general method which uses the sensitivity of the variation in voltage and reactive power has been used to determine the location of shunt type FACTS device, but there is a difficulty to finding a proper location due to the overestimation of the effect of sub-transmission systems. Therefore, there is a need to reduce sub-transmission system for finding an effective location of shunt type FACTS devices such as SVC(Static Var Compensator), STATCOM(Static Synchronous Compesator), and so on.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.1
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• pp.13-17
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• 2006

In this paper, the RCF(Resistive Companion Form) analysis method which is used to analyze small signal stability problems of non-continuous systems including switching devices. The RCF analysis method is mathematically rigorous and computes eigenvalue of the system periodic transition matrix based on discrete system analysis method. As an effect of switching operations, the eigenvalues of the systems are changed and newly unstable oscillation modes may be occurred. As an illustrating example, the oscillation modes of the system with different switching time intervals are computed exactly by the RCF analysis method and the results show that ON/OFF time intervals of switching equipments are important factors to make the system stable or unstable. This result shows that the RCF analysis method is very powerful to analyze small signal stability problems of power systems including switching devices such as FACTS equipments.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1302-1304
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• 1999

This Paper Proposes the FACTS site selection method using subtransmission system reduction. A general method which uses the sensitivity of the variation in voltage and reactive Power has been used to determine the location of shunt type FACTS device, but there is a difficulty to find a proper location due to the overestimation of the effect of sub-transmission systems. Therefore, there is a need to reduce sub-transmission system for finding an effective location of shunt type FACTS devices such as SVC(Static Var Compensator), STATCOM(Static Synchronous Compesator), and so on.

• Proceedings of the KIEE Conference
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• 1997.07c
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• pp.835-837
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• 1997

This paper presents a control system design for the STATCON of FACTS devices by LQR, LQG control scheme to enhance small-signal stability in the power system, the feature of this FACTS controller is coordinated with generator exciter controller(AVR, PSS) to improve the total power system stability and performance.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.4
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• pp.394-402
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• 2000

This paper proposes a bifurcation theory method applied for voltage stability analysis and shows the improvement of voltage stability by attaching the FACTS devices in the power system. A power system is generally expressed by a set of equations of highly nonlinear dynamical system which includes system parameters(real or reactive power). Sometimes variation of parameters in the system may result in complication behaviors which give rise to system instability. The addition of FACTS increases the range of voltage stability in the power system. The effect of FACTS which improves voltage stability are illustrated in the case studies by delaying of Unstable Hopf Bifurcation and Saddle Node Bifurcation.

• Journal of Electrical Engineering and Technology
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• v.7 no.4
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• pp.493-500
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• 2012

In this paper the performance of meta-heuristics algorithms such as GA (Genetic Algorithm), DE (Differential Evolution), PSO (Particle Swarm Optimization) and SA (Simulated Annealing) for the problem of TTC enhancement using FACTS devices are compared. In addition to that in the assessment procedure of TTC two novel techniques are proposed. First the optimization algorithm which is used for TTC enhancement is simultaneously used for assessment of TTC. Second the power flow is done using Broyden - Shamanski method with Sherman - Morrison formula (BSS). The proposed approach is tested on WSCC 9 bus, IEEE 118 bus test systems and the results are compared with the conventional Repeated Power Flow (RPF) using Newton Raphson (NR) method which indicates that the proposed method provides better TTC enhancement and computational efficacy than the conventional procedure.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.2
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• pp.67-72
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• 2005

In conventional small signal stability analysis, system is assumed to be invariant and the state space equations are used to calculate the eigenvalues of state matrix. However, when a system contains switching elements such as FACTS devices, it becomes non-continuous system. In this case, a mathematically rigorous approach to system small signal stability analysis is by means of eigenvalue analysis of the system periodic transition matrix based on discrete system analysis method. In this paper, RCF(Resistive Companion Form) method is used to analyse small signal stability of a non-continuous system including switching elements. Applying the RCF method to the differential and integral equations of power system, generator, controllers and FACTS devices including switching elements should be modeled in the form of state transition equations. From this state transition matrix eigenvalues which are mapped to unit circle can be calculated.