• Proceedings of the KIEE Conference
• /
• 2001.07a
• /
• pp.220-222
• /
• 2001

This paper represents impedance calculation of the distance relay using PSCAD/EMTDC software for transmission line involving the UPFC (Unified Power Flow Controller) device, which is the most vigorous component of FACTS. The presence of the UPFC significantly affects the line parameters of transmission system, which are also influenced by the distance relay setting. Moreover depending on the UPFC location and its parameters, zones of setting the distance relay will be changed. The presence of the UPFC in the fault loop affects both voltage and current seen by relay. Therefore, the distance relay should be taken into account the variable injected voltage of the UPFC.

• Proceedings of the KIEE Conference
• /
• 2001.11b
• /
• pp.296-298
• /
• 2001

This paper represents protective management system for transmission line involving the UPFC(Unified Power Flow Controller) device, which is the most vigorous component of FACTS. The presence of the UPFC significantly affects the line parameters of transmission system, which are also influenced by the distance relay setting. Moreover, depending on the UPFC location and its parameters, zones of setting the distance relay will be changed. Therefore, established protective system should be taken into account the variable injected voltage of the UPFC and constructed data base system.

• Journal of Electrical Engineering and Technology
• /
• v.5 no.2
• /
• pp.197-208
• /
• 2010

Unified power flow controller (UPFC) is the most reliable device in the FACTS concept. It has the ability to adjust all three control parameters effective in power flow and voltage stability. In this paper, a linearized model of a power system installed with a UPFC has been presented. UPFC has four control loops that by adding an extra signal to one of them, increases dynamic stability and load angle oscillations are damped. In this paper, after open loop eigenvalue (electro mechanical mode) calculations, state-space equations have been used to design damping controller and it has been considered to influence active and reactive power flow durations as the input of damping controller, in addition to the common speed duration of synchronous generators as input damper signal. To increase stability, further Lead-Lag and LQR controllers, a novel on-line adaptive controller has been used analytically to identify power system parameters. Closed-loop calculations of the electro mechanical mode verify the improvement of system pole placement after controller designing. Suitable operation of adaptive controller to decrease rotor speed oscillations against input mechanical torque disturbances is confirmed by the simulation results.

• Proceedings of the KIEE Conference
• /
• 2002.07a
• /
• pp.93-95
• /
• 2002

This paper presents the design of a Unified Power Flow Controller(UPFC) for enhancing the small signal voltage stability in the multi-machine power systems. Recently a lot of attention has been paid to the subject of dynamic stability. The paper deals with analysis of eigenvalue sensitivities with respect to parameters of UPFC Controller. The series branch of the UPFC is designed to damp the power oscillation during transients, while the shunt branch aims at maintaining the bus voltage. Comprehensive time-domain simulation studies using Pss/E show that the proposed robost UPFC controller can enhance the small signal stability efficiently in spite of the variations of power system operating conditions.

• Proceedings of the KIEE Conference
• /
• 2001.05a
• /
• pp.162-165
• /
• 2001

본 논문은 EMTDC/PSCAD 프로그램을 이용한 80MVA UPFC(Unified Power Flow Controller)해석모델 개발과 2003년 실계통 적용시 적용효과에 대하여 기술하였다. UPFC는 90년대 이후 개발되고 있는 유연송전 시스템(FACTS : Flexible AC Transmission System)기기중 전압. 임피던스, 위상각등 송전선로에서의 전력조류제어를 위한 모든 파라미터를 동시에 고속으로 제어 할 수 있는 대표적인 FACTS 기기이며, 국내에도 2003년 강진 S/S에 80MVA 용량의 UPFC가 적용될 예정이다. 그러나 실 계통에서의 FACTS기기 적용을 위해서는 다양한 적용 효과분석 및 충분한 신뢰도 테스트가 선행되어야 한다. 따라서 이를 위한 기기 해석모델 개발은 매우 중요하다고 할 수 있다. 본 논문은 국내 전력 계통에 최초 적용되는 80MVA UPFC Pilot Plant에 대한 EMTDC/PSCAD 해석모델 개발결과에 대하여 기술하였다. EMTDC/PSCAD는 EMTP와 더불어 전력시스템의 과도현상 해석을 위한 신뢰성있는 프로그램이다.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.49 no.10
• /
• pp.502-508
• /
• 2000

This paper presents a dynamic simulation algorithm for studying the effect of United Power Flow Controller(UPFC) on the low frequency power system oscillations and transient stability studies. The proposed algorithm is a Newton-type one and uses current injection type UPFC model, which gives a fast convergence characteristics. The algorithm is applied to studying inter-area power oscillation damping enhancement of a sample two-area power system both in time domain and frequency domain. The case study results show that the proposed algorithm is very efficient and UPFC is very effective and robust against operating point change.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.48 no.7
• /
• pp.824-831
• /
• 1999

This paper presents new methods to resolve the important limits in the decoupled UPFC model for power flow, by which conventional power flow program can be performed with addition of two buses per one UPFC. In order to operate UPFC to the desired value, the series voltage and shunt current of UPFC should be computed. So a method of calculating these by simple equations after power flow is derived. However, the calculated magnitude of series voltage and/or shunt current of UPFC may not be allowed because of the UPFC limit \ulcorner to the ratings of inverters. In this case, the active power and the reactive power (or the voltage magnitude) of UPFC buses should be revised to resolve the limit. This paper proposes the Newton Raphson method to resolve these limits. Particularly, when resolving the series voltage magnitude, three strategies are proposed according to the priority of the active power and the reactive power (or the voltage magnitude).

• Proceedings of the KIPE Conference
• /
• 2005.07a
• /
• pp.389-391
• /
• 2005

This paper describes experimental analysis of UPFC, which is composed of cascaded H-bridge modules and single-phase multi-winding transformers for isolation. The operational characteristic was analyzed through experimental works with a scaled model, and simulation results with PSCAD/EMTDC. The UPFC proposed In this paper can be directly connected to the transmission line without series injection transformers. It has flexibility to expand the operation voltage by increasing the number of H-bridge modules. The analysis results can be utilized to design the actual UPFC system applicable for the transmission system.

• Transactions on Electrical and Electronic Materials
• /
• v.18 no.5
• /
• pp.303-309
• /
• 2017

The flexible AC transmission system (FACTS) provides a new advanced technology solution to improve the flexibility, controllability, and stability of a power system. The unified power flow controller (UPFC) is outstanding for regulating power flow in the FACTS; it can control the real power, reactive power, and node voltage of distribution networks. This paper investigates the performance of the UPFC for power flow control with a series of step changes in rapid succession in a power system steady state and the response of the UPFC to distribution network faults and islanding mode. Simulation was carried out using the MATLAB's simulink sim power systems toolbox. The results, which were carried out on a 5-bus test system and a 4-bus multi-machine electric power system, show clearly the effectiveness and viability of UPFC in rapid response and independent control of the real and reactive power flows and oscillation damping [6].

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.51 no.4
• /
• pp.211-218
• /
• 2002

We propose a intelligent controller for FACTS device to stabilize a power system. In order to identify the nonlinear characteristics of the power system and to estimate a control signal, an artificial neural network is utilized. Parameter and location of Unified Power Flow Controller(UPFC) on power system operating conditions are discussed. A UPFC is composed of an excitation transformer, a boosting, two three-phase GTO based voltage source converters, and a dc link capacitor. The proposed controller is applied to UPFC to verified the effectiveness of the proposed control system. The results show that the proposed nonlinear FACTS controller is able to enhance the transient stability of a three machine and nine bus system.