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Khorrami N.,Islamic Azad University at Borujerd
Research Journal of Applied Sciences, Engineering and Technology | Year: 2012

This study starts from the proof of Low Frequency Oscillation (LFO) and then points out that there are many ways to study the LFO including its rejection measures. Also in this study one control system is planned in order to regulate voltage at common coupling point (PCC) in where STATCOM is installed. This research present a single-machine infinite-bus system with one static synchronous compensator (STATCOM) asymmetrically installed as a current source. Together with a classical generator model, the simplest power equation is obtained to give direct and clear physical concepts on synchronizing and damping torque factors. According to the primary equations, some basic issues, such as the relationship of voltage gain control and damping control, operating conditions, and the installation of STATCOM, are investigated in this research. Then, with assistance of proportional controller for voltage regulation and damp control, the digital simulation indicate the necessity of control of STATCOM in damping power system oscillations and supplying regulated voltage support. © Maxwell Scientific Organization, 2012.

Khorrami N.,Islamic Azad University at Borujerd
Research Journal of Applied Sciences, Engineering and Technology | Year: 2012

The Dynamic Voltage Restorer (DVR) is a series-connected compensator to generate a controllable voltage to against the short-term voltage disturbances. The technique of DVR is an effective and cost competitive approach to improve voltage quality at the load side. This study presents a single-phase and threephase DVR system with reduced switch-count topology to protect the sensitive load against abnormal voltage conditions. Most basic function, the DVR configuration consist of a two level Voltage Source Converter (VSC), a dc energy storage device, a coupling transformer Connected in shunt with the ac system This study presents the application of Dynamic Voltage Restorer (DVR) on power distribution systems for mitigation of voltage sag at critical loads. DVR is one of the compensating types of custom power devices. The DVR, which is based on forced-commutated Voltage Source Converter (VSC) has been proved suitable for the task of compensating voltage sags/swells. Simulation results are presented to illustrate and understand the performances of DVR in supporting load voltages under voltage sags/swells conditions. © Maxwell Scientific Organization, 2012.

Farmanbordar A.,Islamic Azad University at Borujerd | Hoseini S.M.,Malek-Ashtar University of Technology
Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME | Year: 2013

This paper presents an adaptive output-feedback control method based on neural networks for flexible link manipulator which is a nonlinear nonminimum phase system. The proposed controller comprises a linear, a neuro-adaptive, and an adaptive robustifying parts. The neural network is designed to approximate the matched uncertainty of the system. The inputs of the neural network are the tapped delays of the system input-output signals. In addition, an appropriate reference signal is proposed to compensate the unmatched uncertainty inherent in the internal system dynamics. The adaptation laws for the neural network weights and adaptive gains are obtained using the Lyapunov's direct method. These adaptation laws employ a linear observer of system dynamics that is realizable. The ultimate boundedness of the error signals are analytically shown using Lyapunov's method. © VC 2012 by ASME.

Hejazian M.,Islamic Azad University at Borujerd | Moraveji M.K.,Arak University
Numerical Heat Transfer; Part A: Applications | Year: 2013

In this article, turbulent forced convection flow of dilute water/TiO 2 nanofluid with a particle diameter equal to 30 nm in a horizontal circular tube exposed to convection with saturated steam at the wall, is numerically analyzed. Two different approaches are taken into consideration: single and two-phase mixture models. It is comprehended that the convective heat transfer coefficient increases with the particle volume concentration and Reynolds number. On the other hand, the mixture model was in better agreement with experimental data than the single phase approach. © 2013 Copyright Taylor and Francis Group, LLC.

Mohammadi M.,Islamic Azad University at Borujerd
Research Journal of Applied Sciences, Engineering and Technology | Year: 2011

However, in previous study the effect of SVC and PSS on voltage transient in power system with suitable model of these component for various faults such as Single Line to Ground faults (SLG) and Line to line and Line to Line to Ground (LL and LLG) and three phase faults have not been considered and analyzed and investigated. Shunt Flexible AC Transmission System (FACTS) devices, when placed at the mid-point of along transmission line, play an important role in controlling the reactive power flow to the power network and hence both the system voltage fluctuions and transient stability. This study deals with the location of a shunt FACTS device to improve transient stability in along transmission line with pre defined direction of real power flow. The validity of the mid-point location of shunt FACTS devices is verified, with various shunt FACTS devices, namely Static Var Compensator (SVC) in a long transmission line using the actual line model. It has been observed that the FACTS devices, when placed slightly off-centre towards sending-end, give better performance in improving transient stability and the location depends on the amount of local/through load. This study investigates the effects of Static Var Compensator (SVC) on voltage stability of a power system. The functional structure for SVC built with a Thyristor Controlled Reactor (TCR) and its model are described. The model is based on representing the controller as variable impedance that changes with the firing angle of the TCR. A Power System Computer Aided Design /Electromagnetic Transients including DC (PSCAD/EMTDC) is used to carry out simulations of the system under study and detailed results are shown to access the performance of SVC on the voltage stability of the system. © 2011 Maxwell Scientific Organization.

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