Hadi Varahram - Academia.edu (original) (raw)

Papers by Hadi Varahram

Research paper thumbnail of Using a Hybrid PSO-GA Method for Capacitor Placement in Distribution Systems

Research paper thumbnail of Sedimentation and mixing analysis in cattle manure feedstock in a stirred tank of anaerobic digestion

Applied Environmental Research, 2018

Research paper thumbnail of The Influence of Conductor Sag on Spatial Distribution of Transmission Line Magnetic Field

IFAC Proceedings Volumes, 2003

Research paper thumbnail of A Criterion to Evaluate the Accuracy of Reduced Order Models of Induction Generators Based on Neglecting Stator Transients

IFAC Proceedings Volumes, 2003

Various attempts has been made to derive linearized, reduced order models of induction generators... more Various attempts has been made to derive linearized, reduced order models of induction generators. Due to the fact that there is usually numerous number of these machines in wind power plants, these models provide great facilities in calculations, and therefore are used widely in power system transient stability studies.Among various order reduction methods the most applicable ones are those based on neglecting the stator transients of the machine.In this paper, some of these methods are discussed and a criterion has been introduced to evaluate the accuracy of resultant reduced order models.

Research paper thumbnail of A Novel Approach to Modeling the Superconductive Shielded Core Reactor (SSCR)

IFAC Proceedings Volumes, 2003

Electric power system designers often face fault current problems when expanding existing buses. ... more Electric power system designers often face fault current problems when expanding existing buses. "Superconductive Fault current limiter" (SFCL) serves as a promising answer to solve the problem. In this paper a shielded core SFCL-which is called Superconductive Shielded Core Reactor (SSCR)-is modeled and computer simulation shows the effectiveness of this device in reducing the short circuit level without affecting the normal behavior of the system.

Research paper thumbnail of Mitigation of AC Voltage Occurring in Pipeline Located Closed to Electric Transmission Lines with Design of Joint Right of Way

IFAC Proceedings Volumes, 2003

In joint-use corridors where both pipelines and AC electric transmission lines are present, a por... more In joint-use corridors where both pipelines and AC electric transmission lines are present, a portion of the energy contained in the electromagnetic field surrounding the electric transmission lines is captured by each pipeline, resulting in induced AC voltages. In this paper a joint power line/pipeline Right of Way is designed. Suitable single and double circuit configuration of overhead transmission line or suitable distance of buried pipelines from center electric power lines for mitigation of buried pipeline voltage due to AC Inductive Coupling is introduced and discussed.

Research paper thumbnail of A Novel Algorithm for Optimal Location of FACTS Devices in Power System Planning

Journal of Electrical Engineering and Technology, 2008

Research paper thumbnail of A New Approach to Model and Study the Performance of an SSCR Used to Improve the Protection and Control of the Power Grid

Research paper thumbnail of Online Solving Of Economic Dispatch Problem Using Neural Network Approach And Comparing It With Classical Method

2006 International Conference on Emerging Technologies, 2006

In this study, two methods for solving economic dispatch problems, namely Hopfield neural network... more In this study, two methods for solving economic dispatch problems, namely Hopfield neural network and lambda iteration method are compared. Three sample of power system with 3, 6 and 20 units have been considered. The time required for CPU, for solving economic dispatch of these two systems has been calculated. It has been shown that for on-line economic dispatch, Hopfield

Research paper thumbnail of A New Approach to Reduce the Dynamic Order of Induction Generators

International Journal of Power and Energy Systems, 2007

Various attempts have been made to derive linearized, reduced order models of induction generator... more Various attempts have been made to derive linearized, reduced order models of induction generators. Due to the fact that there is usually numerous number of these machines in wind power plants, these models provide great facilities in calculations, and therefore are used widely in power system transient stability studies. In this paper, some of these methods are discussed and compared and then a method known as "balanced realizations" is used to reduce the dynamic order of the machine. Computer simulation shows that the last method markedly improves the accuracy of the resulting reduced order model. The improvement is demonstrated by comparing the response characteristics predicted by each reduced order model with that predicted by the complete or detailed model.

Research paper thumbnail of Using Neural Network for Solving of On-Line Economic Dispatch Problem

2006 International Conference on Computational Inteligence for Modelling Control and Automation and International Conference on Intelligent Agents Web Technologies and International Commerce (CIMCA'06), 2006

In this study, two methods for solving economic dispatch problems, namely Hopfield neural network... more In this study, two methods for solving economic dispatch problems, namely Hopfield neural network and λ iteration method are compared. Three sample of power system with 3, 6 and 20 units have been considered. The time required for CPU, for solving economic dispatch of these two ...

Research paper thumbnail of Expansion of E-Learning in Iran

2008 3rd International Conference on Information and Communication Technologies: From Theory to Applications, 2008

... http://www.shirazu.ac.ir http://www.elearning-iust.ir/ ... E-learning in Iran, first, develop... more ... http://www.shirazu.ac.ir http://www.elearning-iust.ir/ ... E-learning in Iran, first, developed in the most famous and high-ranking universities like, Shiraz university, Amirkabir University, University of science and technology, KNToosi University, Payam Noor University and etc. ...

Research paper thumbnail of Limiting fault currents in wind power plants using superconductive shielded core reactors

2008 IEEE Power and Energy Society General Meeting - Conversion and Delivery of Electrical Energy in the 21st Century, 2008

Page 1. 1 Limiting Fault Currents in Wind Power Plants Using Superconductive Shielded Core Reacto... more Page 1. 1 Limiting Fault Currents in Wind Power Plants Using Superconductive Shielded Core Reactors Abstract— In this paper we investigate the effects of superconducting shielded core reactor (SSCR) on the operation of induction generators. ...

Research paper thumbnail of Simulating the effect of SFCL on limiting the internal fault of synchronous machine

Journal of Physics: Conference Series, 2008

In this paper, we have modelled a synchronous generator with internal one phase to ground fault a... more In this paper, we have modelled a synchronous generator with internal one phase to ground fault and then the performance of this machine with internal one phase to ground fault have been analyzed. The results show that if the faults occur in vicinity of machine's terminal, then we would have serious damages. To protect the machine from this kind of faults we have suggested integrating a SFCL (superconducting fault current limiter) into the machine's model. The results show that the fault currents in this case will reduce considerably without influencing the normal operation of the machine.

Research paper thumbnail of Simulation of Nonlinear Dynamics Effects for Josephson Junctions

wseas.us

Simulation of Nonlinear Dynamics Effects for Josephson Junctions. MOSTAFA BORHANI, M.HADI VARAHRA... more Simulation of Nonlinear Dynamics Effects for Josephson Junctions. MOSTAFA BORHANI, M.HADI VARAHRAM. Electrical Engineering Department. Sharif University of Technology. ... The fixed point may be a saddle point, stable node, unstable node, center, spiral, or star node. ...

Research paper thumbnail of A new modeling of inductive sensors for current measuring at high voltage

Proceedings of the 4th …, 2005

Inductive sensors are used in electric equipment like current measuring insulators and metal dete... more Inductive sensors are used in electric equipment like current measuring insulators and metal detectors. Modeling of these sensors will raise their accuracy and consequently will lead to developing of high precision current measuring devices. The idea of expressing the voltage induced in the sensor in terms of current passing through the line and geometrical parameters is the goal of this study. Inductive sensors with rectangular cross section have been studied and the results show good conformity with previous works Changes in dimensions like varying the diameter of current carrying cable will cause big error in current sensing if the modeling is not considered.

Research paper thumbnail of Application of Superconductive Equipment In Power Industry

ABSTRACT Application of superconductors in power mainly refers to their attractive feature in tra... more ABSTRACT Application of superconductors in power mainly refers to their attractive feature in transmitting the energy without loss. Based on this fact various field of application are being discovered for super-conductors and newer fields are added continuously. In this paper some of the most important applications of super-conductors in power engineering are discussed. INTRODUCTION Although Superconductivity is not a new phenomenon from theoretical point of view, as far as application most attention is being paid to it in recent years. This is mostly attributed to the advent of high temperature superconductors (HTS) that eliminate the need for liquefying helium and requires the liquid nitrogen that is less costly, more accessible and more easy to use. High Temperature Superconductors (HTS) are widely considered for large power applications used by industrial

Research paper thumbnail of Using a Hybrid PSO-GA Method for Capacitor Placement in Distribution Systems

Research paper thumbnail of Sedimentation and mixing analysis in cattle manure feedstock in a stirred tank of anaerobic digestion

Applied Environmental Research, 2018

Research paper thumbnail of The Influence of Conductor Sag on Spatial Distribution of Transmission Line Magnetic Field

IFAC Proceedings Volumes, 2003

Research paper thumbnail of A Criterion to Evaluate the Accuracy of Reduced Order Models of Induction Generators Based on Neglecting Stator Transients

IFAC Proceedings Volumes, 2003

Various attempts has been made to derive linearized, reduced order models of induction generators... more Various attempts has been made to derive linearized, reduced order models of induction generators. Due to the fact that there is usually numerous number of these machines in wind power plants, these models provide great facilities in calculations, and therefore are used widely in power system transient stability studies.Among various order reduction methods the most applicable ones are those based on neglecting the stator transients of the machine.In this paper, some of these methods are discussed and a criterion has been introduced to evaluate the accuracy of resultant reduced order models.

Research paper thumbnail of A Novel Approach to Modeling the Superconductive Shielded Core Reactor (SSCR)

IFAC Proceedings Volumes, 2003

Electric power system designers often face fault current problems when expanding existing buses. ... more Electric power system designers often face fault current problems when expanding existing buses. "Superconductive Fault current limiter" (SFCL) serves as a promising answer to solve the problem. In this paper a shielded core SFCL-which is called Superconductive Shielded Core Reactor (SSCR)-is modeled and computer simulation shows the effectiveness of this device in reducing the short circuit level without affecting the normal behavior of the system.

Research paper thumbnail of Mitigation of AC Voltage Occurring in Pipeline Located Closed to Electric Transmission Lines with Design of Joint Right of Way

IFAC Proceedings Volumes, 2003

In joint-use corridors where both pipelines and AC electric transmission lines are present, a por... more In joint-use corridors where both pipelines and AC electric transmission lines are present, a portion of the energy contained in the electromagnetic field surrounding the electric transmission lines is captured by each pipeline, resulting in induced AC voltages. In this paper a joint power line/pipeline Right of Way is designed. Suitable single and double circuit configuration of overhead transmission line or suitable distance of buried pipelines from center electric power lines for mitigation of buried pipeline voltage due to AC Inductive Coupling is introduced and discussed.

Research paper thumbnail of A Novel Algorithm for Optimal Location of FACTS Devices in Power System Planning

Journal of Electrical Engineering and Technology, 2008

Research paper thumbnail of A New Approach to Model and Study the Performance of an SSCR Used to Improve the Protection and Control of the Power Grid

Research paper thumbnail of Online Solving Of Economic Dispatch Problem Using Neural Network Approach And Comparing It With Classical Method

2006 International Conference on Emerging Technologies, 2006

In this study, two methods for solving economic dispatch problems, namely Hopfield neural network... more In this study, two methods for solving economic dispatch problems, namely Hopfield neural network and lambda iteration method are compared. Three sample of power system with 3, 6 and 20 units have been considered. The time required for CPU, for solving economic dispatch of these two systems has been calculated. It has been shown that for on-line economic dispatch, Hopfield

Research paper thumbnail of A New Approach to Reduce the Dynamic Order of Induction Generators

International Journal of Power and Energy Systems, 2007

Various attempts have been made to derive linearized, reduced order models of induction generator... more Various attempts have been made to derive linearized, reduced order models of induction generators. Due to the fact that there is usually numerous number of these machines in wind power plants, these models provide great facilities in calculations, and therefore are used widely in power system transient stability studies. In this paper, some of these methods are discussed and compared and then a method known as "balanced realizations" is used to reduce the dynamic order of the machine. Computer simulation shows that the last method markedly improves the accuracy of the resulting reduced order model. The improvement is demonstrated by comparing the response characteristics predicted by each reduced order model with that predicted by the complete or detailed model.

Research paper thumbnail of Using Neural Network for Solving of On-Line Economic Dispatch Problem

2006 International Conference on Computational Inteligence for Modelling Control and Automation and International Conference on Intelligent Agents Web Technologies and International Commerce (CIMCA'06), 2006

In this study, two methods for solving economic dispatch problems, namely Hopfield neural network... more In this study, two methods for solving economic dispatch problems, namely Hopfield neural network and λ iteration method are compared. Three sample of power system with 3, 6 and 20 units have been considered. The time required for CPU, for solving economic dispatch of these two ...

Research paper thumbnail of Expansion of E-Learning in Iran

2008 3rd International Conference on Information and Communication Technologies: From Theory to Applications, 2008

... http://www.shirazu.ac.ir http://www.elearning-iust.ir/ ... E-learning in Iran, first, develop... more ... http://www.shirazu.ac.ir http://www.elearning-iust.ir/ ... E-learning in Iran, first, developed in the most famous and high-ranking universities like, Shiraz university, Amirkabir University, University of science and technology, KNToosi University, Payam Noor University and etc. ...

Research paper thumbnail of Limiting fault currents in wind power plants using superconductive shielded core reactors

2008 IEEE Power and Energy Society General Meeting - Conversion and Delivery of Electrical Energy in the 21st Century, 2008

Page 1. 1 Limiting Fault Currents in Wind Power Plants Using Superconductive Shielded Core Reacto... more Page 1. 1 Limiting Fault Currents in Wind Power Plants Using Superconductive Shielded Core Reactors Abstract— In this paper we investigate the effects of superconducting shielded core reactor (SSCR) on the operation of induction generators. ...

Research paper thumbnail of Simulating the effect of SFCL on limiting the internal fault of synchronous machine

Journal of Physics: Conference Series, 2008

In this paper, we have modelled a synchronous generator with internal one phase to ground fault a... more In this paper, we have modelled a synchronous generator with internal one phase to ground fault and then the performance of this machine with internal one phase to ground fault have been analyzed. The results show that if the faults occur in vicinity of machine's terminal, then we would have serious damages. To protect the machine from this kind of faults we have suggested integrating a SFCL (superconducting fault current limiter) into the machine's model. The results show that the fault currents in this case will reduce considerably without influencing the normal operation of the machine.

Research paper thumbnail of Simulation of Nonlinear Dynamics Effects for Josephson Junctions

wseas.us

Simulation of Nonlinear Dynamics Effects for Josephson Junctions. MOSTAFA BORHANI, M.HADI VARAHRA... more Simulation of Nonlinear Dynamics Effects for Josephson Junctions. MOSTAFA BORHANI, M.HADI VARAHRAM. Electrical Engineering Department. Sharif University of Technology. ... The fixed point may be a saddle point, stable node, unstable node, center, spiral, or star node. ...

Research paper thumbnail of A new modeling of inductive sensors for current measuring at high voltage

Proceedings of the 4th …, 2005

Inductive sensors are used in electric equipment like current measuring insulators and metal dete... more Inductive sensors are used in electric equipment like current measuring insulators and metal detectors. Modeling of these sensors will raise their accuracy and consequently will lead to developing of high precision current measuring devices. The idea of expressing the voltage induced in the sensor in terms of current passing through the line and geometrical parameters is the goal of this study. Inductive sensors with rectangular cross section have been studied and the results show good conformity with previous works Changes in dimensions like varying the diameter of current carrying cable will cause big error in current sensing if the modeling is not considered.

Research paper thumbnail of Application of Superconductive Equipment In Power Industry

ABSTRACT Application of superconductors in power mainly refers to their attractive feature in tra... more ABSTRACT Application of superconductors in power mainly refers to their attractive feature in transmitting the energy without loss. Based on this fact various field of application are being discovered for super-conductors and newer fields are added continuously. In this paper some of the most important applications of super-conductors in power engineering are discussed. INTRODUCTION Although Superconductivity is not a new phenomenon from theoretical point of view, as far as application most attention is being paid to it in recent years. This is mostly attributed to the advent of high temperature superconductors (HTS) that eliminate the need for liquefying helium and requires the liquid nitrogen that is less costly, more accessible and more easy to use. High Temperature Superconductors (HTS) are widely considered for large power applications used by industrial