This paper represents a comparative study of
switching methods in order to achieve the smallest m... more This paper represents a comparative study of switching methods in order to achieve the smallest magnitude of inrush current. The equations of inrush currents are obtained to reduce transient inrush current of a power system transformer in a typical power system. The best method of inrush current damping is introduced. The simulation results of EMTP software are provided to prove the evaluation of the analytical comparative study.
This paper presents an application of fuzzy
control to determine the control signal of static var... more This paper presents an application of fuzzy control to determine the control signal of static var compensator (SVC) for reactive power compensation and power factor correction. Input signals for the FLC are chosen as load reactive power and initial firing angle of thyristors. The control signal is calculated using fuzzy membership functions. The effectiveness and feasibility of the TSK (Takagi-Sugeno-Kang) and mamdani type fuzzy controllers for thyristors firing control in SVC is compared. Effectiveness of the proposed technique is demonstrated by simulation studies on a single machine infinite bus system. Results obtained show improvement in the overall system characteristics using the proposed adaptive fuzzy logic SVC controller.
Wind power exploitation development to provide Electricity has had more acceleration in recent ye... more Wind power exploitation development to provide Electricity has had more acceleration in recent years in compare with other sources of providing electrical energy in the world. Since, regions with the potential of wind energy are not necessarily close to consumers ,analyzing and modelling of wind farms in order to distribute system load and to study the electrical and mechanical changes of them is important in many aspects and generally ,wind farms which are connected to electricity system by radius and local grids, will face possibility of transferring provided power of wind farms problem when the position of consumers is far from mentioned units where, using FACTS devices are considered in order to keep stability and to create provided Electricity transferring conditions to consumers. In this paper, a wind farm modelling and UPFC using are studied to solve the wind farms power transmission problems.
Wind power exploitation development to provide
Electricity has had more acceleration in recent ye... more Wind power exploitation development to provide Electricity has had more acceleration in recent years in compare with other sources of providing electrical energy in the world. Since, regions with the potential of wind energy are not necessarily close to consumers, analyzing and modeling of wind farms in order to distribute system load and to study the electrical and mechanical changes of them is important in many aspects. Using induction generators in order to generate electricity in wind turbines are improved generally. Above units are connected to radius and local grid and receive a considerable amount of reactive power from the grid. In this case analysis and modelling of them from the point of stability in order to study the system load distribution and electrical and mechanical parameters change affects is very important. Using FACTS devices in wind farm in order to keep stability and create generated power transmission conditions is considered very much. In this paper, a wind farm modeling and STATCOM usage are studied to increase the upper limits of induction generators dynamic stability in various distortion conditions in grid.
Estimation of optimum switching angles for
multilevel converters so as to produce the required fu... more Estimation of optimum switching angles for multilevel converters so as to produce the required fundamental voltage while at the same time eliminate specified lower order harmonics through Artificial Neural Networks (ANNs) is presented. The proposed technique uses the best performance solutions (lowest THD solutions) as the training data set for proposed ANN system. This technique can be applied to multilevel inverters with any number of levels. As an example, in this paper estimation results of optimum switching angles are given for seven levels inverter to eliminate the 5th and 7th harmonics. After training the proposed ANN system, a large and memory-demanding look-up table replaced with trained neural network to generate the optimum switching angles with lowest THD for a given modulation index. The simulation results are presented in PSCAD/EMTDC software package to validate the accuracy of estimation results by proposed ANN system.
This paper presents the novel particle swarm
optimization technique to determine the optimum swit... more This paper presents the novel particle swarm optimization technique to determine the optimum switching angles of multilevel converters so as to produce the required fundamental voltage while at the same time not generate lower order harmonics. This optimization method is applied to transcendental equations characterizing the harmonic content to minimize low order harmonics. All set of solutions are found for seven and eleven levels inverters to show the simplicity and effectiveness of proposed method.
This paper presents a simultaneous active and
reactive power/voltage dispatch methodology using a... more This paper presents a simultaneous active and reactive power/voltage dispatch methodology using a mixture of continuous and discrete control variables. The continuous control variables are active power and reactive power/voltage magnitudes of generator buses, while the discrete ones are transformer-tap settings. The Lambda iteration based economic dispatch is used to minimize the fuel cost and active power dispatch among the generators. During this process, the voltage magnitude of load buses may move away from the desired value. The genetic algorithm is applied for optimal reactive power/voltage dispatch among generators and determination of tap settings of under load tap changers (ULTCs). This results in globally improvement of voltage regulation of load buses. Considering the fact that the reactive power/voltage of generators are continuous variables while the transformer tap settings are discrete variables, a method is proposed to combine these variables into one suitable chromosome. The IEEE 30-bus test system is used to illustrate the effectiveness and feasibility of proposed approach.
In the single phase induction motors, backward
mmf causes torque and speed pulsations. This paper... more In the single phase induction motors, backward mmf causes torque and speed pulsations. This paper presents a new method to eliminate the instantaneous backward mmf to improve the performance of the single phase induction motor. In the proposed method a calculated reference current which is in quadrature with main winding current instantaneously, is injected to the auxiliary winding. The “Hilbert transformation” is used for obtaining the reference current of auxiliary winding by using the current of main winding. The proposed control scheme is simple and it does not need any position or speed encoder sensors. Basic system operation and theoretical analysis are discussed and simulation results in comparison with conventional method which uses sinusoidal voltage supply are presented to validate performance of the proposed method.
In this paper, power quality improvement by using a
new structure of non superconducting fault cu... more In this paper, power quality improvement by using a new structure of non superconducting fault current limiter (NSFCL) is discussed. This structure prevents voltage sags on Point of Common Coupling (PCC) just after fault occurrence, because of its fast operation. On the other hand, previously used structures produce harmonics on load voltage and have ac losses in normal operation. New structure has solved this problem by using dc voltage source. The proposed structure is simulated using PSCAD/EMTDC software and simulation results are presented to validate the effectiveness of this structure.
Load shedding during contingency conditions is an
efficient solution to alleviate transmission li... more Load shedding during contingency conditions is an efficient solution to alleviate transmission lines over loadings. Minimization of total load shedding considering loads importance has great significance in these situations. This problem requires simultaneous optimization of two or more conflicting objectives, such as minimization of the total load shedding, minimization of transmission lines over loadings and voltage violations minimization. The objectives are in conflict since the improvement of one of them leads to the eterioration of another. A modified version of Non-Dominated Sorting Genetic Algorithm (NSGA-II) is used as an effective optimization tools for solving the minimum weighted load shedding problem during contingency conditions. Also relation between transmission lines overloading and amount of load shedding is surveyed. IEEE 14 bus test system is used as a study case and results are discussed.
In this paper, enhancement of transient stability of
Single Machine Infinite Bus (SMIB) system wi... more In this paper, enhancement of transient stability of Single Machine Infinite Bus (SMIB) system with a double circuit transmission line using a Non-superconducting Fault Current Limiter (NSFCL) is proposed. Stability analysis for such system is discussed in detail. It is shown that, the stability depends on the resistance of NSFCL in fault condition. To effective improvement of stability, the optimum value of NSFCL resistance is calculated. Simulation results by PSCAD/EMTDC software are presented to confirm the analytic analysis accuracy.
This paper proposes a new parallel LC resonance type
Fault Current Limiter (FCL). This structure ... more This paper proposes a new parallel LC resonance type Fault Current Limiter (FCL). This structure has low cast because of using dry capacitor and non-superconducting inductor and fast operation. The proposed FCL is able to limit fault current in constant value near to pre-fault condition value against series resonance type FCL. In this way, the voltage of point of common coupling (PCC) will not change during fault. Analytical analysis is presented in detail and simulation results are involved to validate the effectiveness of this structure.
Nowadays, environmental issues are greatly
concerned. Conventional solutions that use lead acid
b... more Nowadays, environmental issues are greatly concerned. Conventional solutions that use lead acid batteries and diesel engines as sources of energy for both uninterruptible power supply (UPS) and isolated power generation systems are facing an increasing opposition due to environmental and economical concerns. The aim of the paper is to evaluate the technical feasibility and aspects related to the use of fuel cells instead of traditional electrochemical batteries in the UPS. The proposed system is named FCB-UPS (Fuel Cell Based UPS). However, the quality of UPS output voltage is important when it supports the sensitive loads. So, in this paper a new configuration of UPS based on flying capacitor multicell (FCM) converter is proposed to produce the multilevel output voltage to support the sensitive load with sinusoidal voltage. The main properties of FCM converter, which causes increase in the number of output voltage levels, are transformer-less operation and natural self-balancing of flying capacitors voltages. The proposed configuration is simulated using PSCAD/EMTDC software and simulation results are presented to validate its effectiveness.
In this paper, a novel fault location method for
double fed distribution networks is proposed. In... more In this paper, a novel fault location method for double fed distribution networks is proposed. In the last years, fault location on power distribution networks is receiving especial attention due to the importance of a fast actuation to clear the fault causes and the resulting reduce outage time and significantly improve system reliability. This paper proposes a new fault location algorithm developed by the direct circuit analysis for balanced and unbalanced double fed distribution systems, which has not been investigated due to high complexity. The proposed algorithm overcomes the limit of the conventional algorithm, which requires only the balanced system. Simulation results of our fault location algorithm for the balanced distribution network with three-phase loads and unbalanced network with combination of single-phase and three-phase loads are also presented. Results show that this method has greatly simplified the derivation of complicated fault location equation therefore can superiorly enhance the fault location process is well suited for identifying fault location in balanced and unbalanced distribution networks in different fault resistances.
In this paper a variable and controllable resistor
type fault current limiter (FCL) is introduced... more In this paper a variable and controllable resistor type fault current limiter (FCL) is introduced for enhancement of transient stability of single machine infinite bus (SMIB) system with a double circuit transmission line. The optimal value of resistor during fault to reach the maximum stability of power system is computed. It is shown that, this optimal value depends on the fault location and the pre-fault active power of synchronous generator considering power demand changing. To show the effectiveness of the proposed FCL, analytical analysis including transient stability study and optimum resistor value calculation are presented. In addition, simulation results using PSCAD /EMTDC software are included to confirm the analytical analysis accuracy.
This paper proposes a new topology for fault current
limiter (FCL) that is based on series LC res... more This paper proposes a new topology for fault current limiter (FCL) that is based on series LC resonance circuit. The proposed FCL uses a high speed switch to put an inductor in series with a capacitor and make resonance condition between them. This structure can hold the peak of fault current in the constant value that is not possible in previously introduced series resonance type FCLs. In such conditions, if fault continues, power system will not be experience large short circuit currents. Using non-superconducting inductor instead of superconducting one, leads to low construction and maintenance costs in this structure. In addition, in normal operation, capacitor of this FCL can be used as a series compensator. Analytical analysis for the proposed series resonance type FCL is performed in detail. Simulations are presented using PSCAD/EMTDC software to show the operation of the proposed FCL. Also, comparison between the proposed FCL and previous series resonance type FCLs is included in simulations.
In this paper a new power circuit topology for FACTS
controllers is introduced. This topology is ... more In this paper a new power circuit topology for FACTS controllers is introduced. This topology is neither series nor parallel FACTS controller. This controller injects an additive compensating voltage between each of two phases of a three phase power line by using a voltage source inverter (VSI). So, it is named as line to line compensator (LLC). Analytical analysis and simulation results by MATLAB/SIMULINK are presented and a test setup is built to verify the operation of proposed FACTC controller.
In this paper the practical planning of distribution system
includes the selection of optimal con... more In this paper the practical planning of distribution system includes the selection of optimal conductor size and capacitor placement in radial distribution network considering increasing rate of loads. Technical operational constraints are available conductors and capacitors, voltage limit, maximum permissible carrying current of conductors and maximum reactive power could be injected. The power loss minimization problem is solved using particle swarm optimization (PSO). By applying this method, final cost of network planning, losses and their cost are considerably reduced and voltage profile of the network has improved to a semiflat shape. Simulation results are investigated on a practical radial distribution network in Iran (Miandoab 20 kv distribution network), in addition self supporting cables are used for optimization which avoids illegal use of electricity.
In this paper, transient stability improvement using bridge
type fault current limiter (FCL) is p... more In this paper, transient stability improvement using bridge type fault current limiter (FCL) is presented in single machine infinite bus (SMIB) system with a double circuit transmission line. Three single-phase sets of the proposed FCL are installed at the beginning of feeder. The proposed FCL inserts an inductance and a resistance in the fault current pass. The insertion inductance and resistance not only limits the fault current level in an acceptable value but also improves transient stability of power system by consuming excessive energy of synchronous generator during fault. To reach maximum transient stability, the optimal resistor value of the proposed FCL is calculated. Analytical analysis and simulation results using PSCAD/EMTDC software are presented to show the current limiting future and transient stability enhancement using the proposed FCL in SMIB.
This paper represents a comparative study of
switching methods in order to achieve the smallest m... more This paper represents a comparative study of switching methods in order to achieve the smallest magnitude of inrush current. The equations of inrush currents are obtained to reduce transient inrush current of a power system transformer in a typical power system. The best method of inrush current damping is introduced. The simulation results of EMTP software are provided to prove the evaluation of the analytical comparative study.
This paper presents an application of fuzzy
control to determine the control signal of static var... more This paper presents an application of fuzzy control to determine the control signal of static var compensator (SVC) for reactive power compensation and power factor correction. Input signals for the FLC are chosen as load reactive power and initial firing angle of thyristors. The control signal is calculated using fuzzy membership functions. The effectiveness and feasibility of the TSK (Takagi-Sugeno-Kang) and mamdani type fuzzy controllers for thyristors firing control in SVC is compared. Effectiveness of the proposed technique is demonstrated by simulation studies on a single machine infinite bus system. Results obtained show improvement in the overall system characteristics using the proposed adaptive fuzzy logic SVC controller.
Wind power exploitation development to provide Electricity has had more acceleration in recent ye... more Wind power exploitation development to provide Electricity has had more acceleration in recent years in compare with other sources of providing electrical energy in the world. Since, regions with the potential of wind energy are not necessarily close to consumers ,analyzing and modelling of wind farms in order to distribute system load and to study the electrical and mechanical changes of them is important in many aspects and generally ,wind farms which are connected to electricity system by radius and local grids, will face possibility of transferring provided power of wind farms problem when the position of consumers is far from mentioned units where, using FACTS devices are considered in order to keep stability and to create provided Electricity transferring conditions to consumers. In this paper, a wind farm modelling and UPFC using are studied to solve the wind farms power transmission problems.
Wind power exploitation development to provide
Electricity has had more acceleration in recent ye... more Wind power exploitation development to provide Electricity has had more acceleration in recent years in compare with other sources of providing electrical energy in the world. Since, regions with the potential of wind energy are not necessarily close to consumers, analyzing and modeling of wind farms in order to distribute system load and to study the electrical and mechanical changes of them is important in many aspects. Using induction generators in order to generate electricity in wind turbines are improved generally. Above units are connected to radius and local grid and receive a considerable amount of reactive power from the grid. In this case analysis and modelling of them from the point of stability in order to study the system load distribution and electrical and mechanical parameters change affects is very important. Using FACTS devices in wind farm in order to keep stability and create generated power transmission conditions is considered very much. In this paper, a wind farm modeling and STATCOM usage are studied to increase the upper limits of induction generators dynamic stability in various distortion conditions in grid.
Estimation of optimum switching angles for
multilevel converters so as to produce the required fu... more Estimation of optimum switching angles for multilevel converters so as to produce the required fundamental voltage while at the same time eliminate specified lower order harmonics through Artificial Neural Networks (ANNs) is presented. The proposed technique uses the best performance solutions (lowest THD solutions) as the training data set for proposed ANN system. This technique can be applied to multilevel inverters with any number of levels. As an example, in this paper estimation results of optimum switching angles are given for seven levels inverter to eliminate the 5th and 7th harmonics. After training the proposed ANN system, a large and memory-demanding look-up table replaced with trained neural network to generate the optimum switching angles with lowest THD for a given modulation index. The simulation results are presented in PSCAD/EMTDC software package to validate the accuracy of estimation results by proposed ANN system.
This paper presents the novel particle swarm
optimization technique to determine the optimum swit... more This paper presents the novel particle swarm optimization technique to determine the optimum switching angles of multilevel converters so as to produce the required fundamental voltage while at the same time not generate lower order harmonics. This optimization method is applied to transcendental equations characterizing the harmonic content to minimize low order harmonics. All set of solutions are found for seven and eleven levels inverters to show the simplicity and effectiveness of proposed method.
This paper presents a simultaneous active and
reactive power/voltage dispatch methodology using a... more This paper presents a simultaneous active and reactive power/voltage dispatch methodology using a mixture of continuous and discrete control variables. The continuous control variables are active power and reactive power/voltage magnitudes of generator buses, while the discrete ones are transformer-tap settings. The Lambda iteration based economic dispatch is used to minimize the fuel cost and active power dispatch among the generators. During this process, the voltage magnitude of load buses may move away from the desired value. The genetic algorithm is applied for optimal reactive power/voltage dispatch among generators and determination of tap settings of under load tap changers (ULTCs). This results in globally improvement of voltage regulation of load buses. Considering the fact that the reactive power/voltage of generators are continuous variables while the transformer tap settings are discrete variables, a method is proposed to combine these variables into one suitable chromosome. The IEEE 30-bus test system is used to illustrate the effectiveness and feasibility of proposed approach.
In the single phase induction motors, backward
mmf causes torque and speed pulsations. This paper... more In the single phase induction motors, backward mmf causes torque and speed pulsations. This paper presents a new method to eliminate the instantaneous backward mmf to improve the performance of the single phase induction motor. In the proposed method a calculated reference current which is in quadrature with main winding current instantaneously, is injected to the auxiliary winding. The “Hilbert transformation” is used for obtaining the reference current of auxiliary winding by using the current of main winding. The proposed control scheme is simple and it does not need any position or speed encoder sensors. Basic system operation and theoretical analysis are discussed and simulation results in comparison with conventional method which uses sinusoidal voltage supply are presented to validate performance of the proposed method.
In this paper, power quality improvement by using a
new structure of non superconducting fault cu... more In this paper, power quality improvement by using a new structure of non superconducting fault current limiter (NSFCL) is discussed. This structure prevents voltage sags on Point of Common Coupling (PCC) just after fault occurrence, because of its fast operation. On the other hand, previously used structures produce harmonics on load voltage and have ac losses in normal operation. New structure has solved this problem by using dc voltage source. The proposed structure is simulated using PSCAD/EMTDC software and simulation results are presented to validate the effectiveness of this structure.
Load shedding during contingency conditions is an
efficient solution to alleviate transmission li... more Load shedding during contingency conditions is an efficient solution to alleviate transmission lines over loadings. Minimization of total load shedding considering loads importance has great significance in these situations. This problem requires simultaneous optimization of two or more conflicting objectives, such as minimization of the total load shedding, minimization of transmission lines over loadings and voltage violations minimization. The objectives are in conflict since the improvement of one of them leads to the eterioration of another. A modified version of Non-Dominated Sorting Genetic Algorithm (NSGA-II) is used as an effective optimization tools for solving the minimum weighted load shedding problem during contingency conditions. Also relation between transmission lines overloading and amount of load shedding is surveyed. IEEE 14 bus test system is used as a study case and results are discussed.
In this paper, enhancement of transient stability of
Single Machine Infinite Bus (SMIB) system wi... more In this paper, enhancement of transient stability of Single Machine Infinite Bus (SMIB) system with a double circuit transmission line using a Non-superconducting Fault Current Limiter (NSFCL) is proposed. Stability analysis for such system is discussed in detail. It is shown that, the stability depends on the resistance of NSFCL in fault condition. To effective improvement of stability, the optimum value of NSFCL resistance is calculated. Simulation results by PSCAD/EMTDC software are presented to confirm the analytic analysis accuracy.
This paper proposes a new parallel LC resonance type
Fault Current Limiter (FCL). This structure ... more This paper proposes a new parallel LC resonance type Fault Current Limiter (FCL). This structure has low cast because of using dry capacitor and non-superconducting inductor and fast operation. The proposed FCL is able to limit fault current in constant value near to pre-fault condition value against series resonance type FCL. In this way, the voltage of point of common coupling (PCC) will not change during fault. Analytical analysis is presented in detail and simulation results are involved to validate the effectiveness of this structure.
Nowadays, environmental issues are greatly
concerned. Conventional solutions that use lead acid
b... more Nowadays, environmental issues are greatly concerned. Conventional solutions that use lead acid batteries and diesel engines as sources of energy for both uninterruptible power supply (UPS) and isolated power generation systems are facing an increasing opposition due to environmental and economical concerns. The aim of the paper is to evaluate the technical feasibility and aspects related to the use of fuel cells instead of traditional electrochemical batteries in the UPS. The proposed system is named FCB-UPS (Fuel Cell Based UPS). However, the quality of UPS output voltage is important when it supports the sensitive loads. So, in this paper a new configuration of UPS based on flying capacitor multicell (FCM) converter is proposed to produce the multilevel output voltage to support the sensitive load with sinusoidal voltage. The main properties of FCM converter, which causes increase in the number of output voltage levels, are transformer-less operation and natural self-balancing of flying capacitors voltages. The proposed configuration is simulated using PSCAD/EMTDC software and simulation results are presented to validate its effectiveness.
In this paper, a novel fault location method for
double fed distribution networks is proposed. In... more In this paper, a novel fault location method for double fed distribution networks is proposed. In the last years, fault location on power distribution networks is receiving especial attention due to the importance of a fast actuation to clear the fault causes and the resulting reduce outage time and significantly improve system reliability. This paper proposes a new fault location algorithm developed by the direct circuit analysis for balanced and unbalanced double fed distribution systems, which has not been investigated due to high complexity. The proposed algorithm overcomes the limit of the conventional algorithm, which requires only the balanced system. Simulation results of our fault location algorithm for the balanced distribution network with three-phase loads and unbalanced network with combination of single-phase and three-phase loads are also presented. Results show that this method has greatly simplified the derivation of complicated fault location equation therefore can superiorly enhance the fault location process is well suited for identifying fault location in balanced and unbalanced distribution networks in different fault resistances.
In this paper a variable and controllable resistor
type fault current limiter (FCL) is introduced... more In this paper a variable and controllable resistor type fault current limiter (FCL) is introduced for enhancement of transient stability of single machine infinite bus (SMIB) system with a double circuit transmission line. The optimal value of resistor during fault to reach the maximum stability of power system is computed. It is shown that, this optimal value depends on the fault location and the pre-fault active power of synchronous generator considering power demand changing. To show the effectiveness of the proposed FCL, analytical analysis including transient stability study and optimum resistor value calculation are presented. In addition, simulation results using PSCAD /EMTDC software are included to confirm the analytical analysis accuracy.
This paper proposes a new topology for fault current
limiter (FCL) that is based on series LC res... more This paper proposes a new topology for fault current limiter (FCL) that is based on series LC resonance circuit. The proposed FCL uses a high speed switch to put an inductor in series with a capacitor and make resonance condition between them. This structure can hold the peak of fault current in the constant value that is not possible in previously introduced series resonance type FCLs. In such conditions, if fault continues, power system will not be experience large short circuit currents. Using non-superconducting inductor instead of superconducting one, leads to low construction and maintenance costs in this structure. In addition, in normal operation, capacitor of this FCL can be used as a series compensator. Analytical analysis for the proposed series resonance type FCL is performed in detail. Simulations are presented using PSCAD/EMTDC software to show the operation of the proposed FCL. Also, comparison between the proposed FCL and previous series resonance type FCLs is included in simulations.
In this paper a new power circuit topology for FACTS
controllers is introduced. This topology is ... more In this paper a new power circuit topology for FACTS controllers is introduced. This topology is neither series nor parallel FACTS controller. This controller injects an additive compensating voltage between each of two phases of a three phase power line by using a voltage source inverter (VSI). So, it is named as line to line compensator (LLC). Analytical analysis and simulation results by MATLAB/SIMULINK are presented and a test setup is built to verify the operation of proposed FACTC controller.
In this paper the practical planning of distribution system
includes the selection of optimal con... more In this paper the practical planning of distribution system includes the selection of optimal conductor size and capacitor placement in radial distribution network considering increasing rate of loads. Technical operational constraints are available conductors and capacitors, voltage limit, maximum permissible carrying current of conductors and maximum reactive power could be injected. The power loss minimization problem is solved using particle swarm optimization (PSO). By applying this method, final cost of network planning, losses and their cost are considerably reduced and voltage profile of the network has improved to a semiflat shape. Simulation results are investigated on a practical radial distribution network in Iran (Miandoab 20 kv distribution network), in addition self supporting cables are used for optimization which avoids illegal use of electricity.
In this paper, transient stability improvement using bridge
type fault current limiter (FCL) is p... more In this paper, transient stability improvement using bridge type fault current limiter (FCL) is presented in single machine infinite bus (SMIB) system with a double circuit transmission line. Three single-phase sets of the proposed FCL are installed at the beginning of feeder. The proposed FCL inserts an inductance and a resistance in the fault current pass. The insertion inductance and resistance not only limits the fault current level in an acceptable value but also improves transient stability of power system by consuming excessive energy of synchronous generator during fault. To reach maximum transient stability, the optimal resistor value of the proposed FCL is calculated. Analytical analysis and simulation results using PSCAD/EMTDC software are presented to show the current limiting future and transient stability enhancement using the proposed FCL in SMIB.
Uploads
switching methods in order to achieve the smallest magnitude of
inrush current. The equations of inrush currents are obtained to
reduce transient inrush current of a power system transformer in
a typical power system. The best method of inrush current
damping is introduced. The simulation results of EMTP software
are provided to prove the evaluation of the analytical
comparative study.
control to determine the control signal of static var
compensator (SVC) for reactive power compensation and
power factor correction. Input signals for the FLC are chosen
as load reactive power and initial firing angle of thyristors.
The control signal is calculated using fuzzy membership
functions. The effectiveness and feasibility of the TSK
(Takagi-Sugeno-Kang) and mamdani type fuzzy controllers
for thyristors firing control in SVC is compared.
Effectiveness of the proposed technique is demonstrated by
simulation studies on a single machine infinite bus system.
Results obtained show improvement in the overall system
characteristics using the proposed adaptive fuzzy logic SVC
controller.
Since, regions with the potential of wind energy are not
necessarily close to consumers ,analyzing and modelling of wind farms in order to distribute system load and to study the
electrical and mechanical changes of them is important in many
aspects and generally ,wind farms which are connected to
electricity system by radius and local grids, will face possibility of transferring provided power of wind farms problem when the position of consumers is far from mentioned units where, using FACTS devices are considered in order to keep stability and to create provided Electricity transferring conditions to consumers. In this paper, a wind farm modelling and UPFC using are studied to solve the wind farms power transmission problems.
Electricity has had more acceleration in recent years in compare
with other sources of providing electrical energy in the world.
Since, regions with the potential of wind energy are not
necessarily close to consumers, analyzing and modeling of wind
farms in order to distribute system load and to study the electrical
and mechanical changes of them is important in many aspects.
Using induction generators in order to generate electricity in wind turbines are improved generally. Above units are connected to radius and local grid and receive a considerable amount of reactive power from the grid. In this case analysis and modelling of them from the point of stability in order to study the system load distribution and electrical and mechanical parameters change affects is very important. Using FACTS devices in wind farm in order to keep stability and create generated power transmission conditions is considered very much. In this paper, a wind farm modeling and STATCOM usage are studied to increase the upper limits of induction generators dynamic stability in various distortion conditions in grid.
multilevel converters so as to produce the required fundamental
voltage while at the same time eliminate specified lower order
harmonics through Artificial Neural Networks (ANNs) is
presented. The proposed technique uses the best performance
solutions (lowest THD solutions) as the training data set for
proposed ANN system. This technique can be applied to
multilevel inverters with any number of levels. As an example, in
this paper estimation results of optimum switching angles are
given for seven levels inverter to eliminate the 5th and 7th
harmonics. After training the proposed ANN system, a large and
memory-demanding look-up table replaced with trained neural
network to generate the optimum switching angles with lowest
THD for a given modulation index. The simulation results are
presented in PSCAD/EMTDC software package to validate the
accuracy of estimation results by proposed ANN system.
optimization technique to determine the optimum switching
angles of multilevel converters so as to produce the required
fundamental voltage while at the same time not generate lower
order harmonics. This optimization method is applied to
transcendental equations characterizing the harmonic content to
minimize low order harmonics. All set of solutions are found for
seven and eleven levels inverters to show the simplicity and
effectiveness of proposed method.
reactive power/voltage dispatch methodology using a mixture of
continuous and discrete control variables. The continuous control
variables are active power and reactive power/voltage
magnitudes of generator buses, while the discrete ones are
transformer-tap settings. The Lambda iteration based economic
dispatch is used to minimize the fuel cost and active power
dispatch among the generators. During this process, the voltage
magnitude of load buses may move away from the desired value.
The genetic algorithm is applied for optimal reactive
power/voltage dispatch among generators and determination of
tap settings of under load tap changers (ULTCs). This results in
globally improvement of voltage regulation of load buses.
Considering the fact that the reactive power/voltage of generators
are continuous variables while the transformer tap settings are
discrete variables, a method is proposed to combine these
variables into one suitable chromosome. The IEEE 30-bus test
system is used to illustrate the effectiveness and feasibility of
proposed approach.
mmf causes torque and speed pulsations. This paper presents a
new method to eliminate the instantaneous backward mmf to
improve the performance of the single phase induction motor. In
the proposed method a calculated reference current which is in
quadrature with main winding current instantaneously, is
injected to the auxiliary winding. The “Hilbert transformation”
is used for obtaining the reference current of auxiliary winding
by using the current of main winding. The proposed control
scheme is simple and it does not need any position or speed
encoder sensors. Basic system operation and theoretical analysis are discussed and simulation results in comparison with conventional method which uses sinusoidal voltage supply are presented to validate performance of the proposed method.
new structure of non superconducting fault current limiter
(NSFCL) is discussed. This structure prevents voltage sags on
Point of Common Coupling (PCC) just after fault occurrence,
because of its fast operation. On the other hand, previously used
structures produce harmonics on load voltage and have ac losses
in normal operation. New structure has solved this problem by
using dc voltage source. The proposed structure is simulated
using PSCAD/EMTDC software and simulation results are
presented to validate the effectiveness of this structure.
efficient solution to alleviate transmission lines over loadings.
Minimization of total load shedding considering loads importance has great significance in these situations. This problem requires simultaneous optimization of two or more conflicting objectives, such as minimization of the total load shedding, minimization of transmission lines over loadings and voltage violations minimization. The objectives are in conflict since the improvement of one of them leads to the eterioration of another.
A modified version of Non-Dominated Sorting Genetic Algorithm (NSGA-II) is used as an effective optimization tools for solving the minimum weighted load shedding problem during contingency conditions. Also relation between transmission lines overloading and amount of load shedding is surveyed. IEEE 14 bus test system is used as a study case and results are discussed.
Single Machine Infinite Bus (SMIB) system with a double circuit
transmission line using a Non-superconducting Fault Current
Limiter (NSFCL) is proposed. Stability analysis for such system
is discussed in detail. It is shown that, the stability depends on the
resistance of NSFCL in fault condition. To effective improvement
of stability, the optimum value of NSFCL resistance is calculated.
Simulation results by PSCAD/EMTDC software are presented to
confirm the analytic analysis accuracy.
Fault Current Limiter (FCL). This structure has low cast because
of using dry capacitor and non-superconducting inductor and
fast operation. The proposed FCL is able to limit fault current in
constant value near to pre-fault condition value against series
resonance type FCL. In this way, the voltage of point of common
coupling (PCC) will not change during fault. Analytical analysis
is presented in detail and simulation results are involved to
validate the effectiveness of this structure.
concerned. Conventional solutions that use lead acid
batteries and diesel engines as sources of energy for both
uninterruptible power supply (UPS) and isolated power
generation systems are facing an increasing opposition due
to environmental and economical concerns. The aim of the
paper is to evaluate the technical feasibility and aspects
related to the use of fuel cells instead of traditional
electrochemical batteries in the UPS. The proposed system
is named FCB-UPS (Fuel Cell Based UPS). However, the
quality of UPS output voltage is important when it supports
the sensitive loads. So, in this paper a new configuration of
UPS based on flying capacitor multicell (FCM) converter is
proposed to produce the multilevel output voltage to
support the sensitive load with sinusoidal voltage. The main
properties of FCM converter, which causes increase in the
number of output voltage levels, are transformer-less
operation and natural self-balancing of flying capacitors
voltages. The proposed configuration is simulated using
PSCAD/EMTDC software and simulation results are
presented to validate its effectiveness.
double fed distribution networks is proposed. In the last
years, fault location on power distribution networks is
receiving especial attention due to the importance of a fast
actuation to clear the fault causes and the resulting reduce
outage time and significantly improve system reliability.
This paper proposes a new fault location algorithm
developed by the direct circuit analysis for balanced and
unbalanced double fed distribution systems, which has not
been investigated due to high complexity. The proposed
algorithm overcomes the limit of the conventional algorithm,
which requires only the balanced system. Simulation results
of our fault location algorithm for the balanced distribution
network with three-phase loads and unbalanced network
with combination of single-phase and three-phase loads are
also presented. Results show that this method has greatly
simplified the derivation of complicated fault location
equation therefore can superiorly enhance the fault location
process is well suited for identifying fault location in
balanced and unbalanced distribution networks in different
fault resistances.
type fault current limiter (FCL) is introduced for enhancement of
transient stability of single machine infinite bus (SMIB) system
with a double circuit transmission line. The optimal value of
resistor during fault to reach the maximum stability of power
system is computed. It is shown that, this optimal value depends
on the fault location and the pre-fault active power of
synchronous generator considering power demand changing. To
show the effectiveness of the proposed FCL, analytical analysis
including transient stability study and optimum resistor value
calculation are presented. In addition, simulation results using
PSCAD /EMTDC software are included to confirm the analytical
analysis accuracy.
limiter (FCL) that is based on series LC resonance circuit. The
proposed FCL uses a high speed switch to put an inductor in
series with a capacitor and make resonance condition between
them. This structure can hold the peak of fault current in the
constant value that is not possible in previously introduced series
resonance type FCLs. In such conditions, if fault continues, power
system will not be experience large short circuit currents. Using
non-superconducting inductor instead of superconducting one,
leads to low construction and maintenance costs in this structure.
In addition, in normal operation, capacitor of this FCL can be
used as a series compensator. Analytical analysis for the proposed
series resonance type FCL is performed in detail. Simulations are
presented using PSCAD/EMTDC software to show the operation
of the proposed FCL. Also, comparison between the proposed
FCL and previous series resonance type FCLs is included in
simulations.
controllers is introduced. This topology is neither series nor
parallel FACTS controller. This controller injects an
additive compensating voltage between each of two phases
of a three phase power line by using a voltage source
inverter (VSI). So, it is named as line to line compensator
(LLC). Analytical analysis and simulation results by
MATLAB/SIMULINK are presented and a test setup is
built to verify the operation of proposed FACTC controller.
includes the selection of optimal conductor size and
capacitor placement in radial distribution network
considering increasing rate of loads. Technical operational
constraints are available conductors and capacitors, voltage
limit, maximum permissible carrying current of conductors
and maximum reactive power could be injected. The power
loss minimization problem is solved using particle swarm
optimization (PSO). By applying this method, final cost of
network planning, losses and their cost are considerably
reduced and voltage profile of the network has improved to
a semiflat shape. Simulation results are investigated on a
practical radial distribution network in Iran (Miandoab
20 kv distribution network), in addition self supporting
cables are used for optimization which avoids illegal use of
electricity.
type fault current limiter (FCL) is presented in single
machine infinite bus (SMIB) system with a double circuit
transmission line. Three single-phase sets of the proposed
FCL are installed at the beginning of feeder. The proposed
FCL inserts an inductance and a resistance in the fault
current pass. The insertion inductance and resistance not
only limits the fault current level in an acceptable value but
also improves transient stability of power system by
consuming excessive energy of synchronous generator
during fault. To reach maximum transient stability, the
optimal resistor value of the proposed FCL is calculated.
Analytical analysis and simulation results using
PSCAD/EMTDC software are presented to show the
current limiting future and transient stability enhancement
using the proposed FCL in SMIB.
switching methods in order to achieve the smallest magnitude of
inrush current. The equations of inrush currents are obtained to
reduce transient inrush current of a power system transformer in
a typical power system. The best method of inrush current
damping is introduced. The simulation results of EMTP software
are provided to prove the evaluation of the analytical
comparative study.
control to determine the control signal of static var
compensator (SVC) for reactive power compensation and
power factor correction. Input signals for the FLC are chosen
as load reactive power and initial firing angle of thyristors.
The control signal is calculated using fuzzy membership
functions. The effectiveness and feasibility of the TSK
(Takagi-Sugeno-Kang) and mamdani type fuzzy controllers
for thyristors firing control in SVC is compared.
Effectiveness of the proposed technique is demonstrated by
simulation studies on a single machine infinite bus system.
Results obtained show improvement in the overall system
characteristics using the proposed adaptive fuzzy logic SVC
controller.
Since, regions with the potential of wind energy are not
necessarily close to consumers ,analyzing and modelling of wind farms in order to distribute system load and to study the
electrical and mechanical changes of them is important in many
aspects and generally ,wind farms which are connected to
electricity system by radius and local grids, will face possibility of transferring provided power of wind farms problem when the position of consumers is far from mentioned units where, using FACTS devices are considered in order to keep stability and to create provided Electricity transferring conditions to consumers. In this paper, a wind farm modelling and UPFC using are studied to solve the wind farms power transmission problems.
Electricity has had more acceleration in recent years in compare
with other sources of providing electrical energy in the world.
Since, regions with the potential of wind energy are not
necessarily close to consumers, analyzing and modeling of wind
farms in order to distribute system load and to study the electrical
and mechanical changes of them is important in many aspects.
Using induction generators in order to generate electricity in wind turbines are improved generally. Above units are connected to radius and local grid and receive a considerable amount of reactive power from the grid. In this case analysis and modelling of them from the point of stability in order to study the system load distribution and electrical and mechanical parameters change affects is very important. Using FACTS devices in wind farm in order to keep stability and create generated power transmission conditions is considered very much. In this paper, a wind farm modeling and STATCOM usage are studied to increase the upper limits of induction generators dynamic stability in various distortion conditions in grid.
multilevel converters so as to produce the required fundamental
voltage while at the same time eliminate specified lower order
harmonics through Artificial Neural Networks (ANNs) is
presented. The proposed technique uses the best performance
solutions (lowest THD solutions) as the training data set for
proposed ANN system. This technique can be applied to
multilevel inverters with any number of levels. As an example, in
this paper estimation results of optimum switching angles are
given for seven levels inverter to eliminate the 5th and 7th
harmonics. After training the proposed ANN system, a large and
memory-demanding look-up table replaced with trained neural
network to generate the optimum switching angles with lowest
THD for a given modulation index. The simulation results are
presented in PSCAD/EMTDC software package to validate the
accuracy of estimation results by proposed ANN system.
optimization technique to determine the optimum switching
angles of multilevel converters so as to produce the required
fundamental voltage while at the same time not generate lower
order harmonics. This optimization method is applied to
transcendental equations characterizing the harmonic content to
minimize low order harmonics. All set of solutions are found for
seven and eleven levels inverters to show the simplicity and
effectiveness of proposed method.
reactive power/voltage dispatch methodology using a mixture of
continuous and discrete control variables. The continuous control
variables are active power and reactive power/voltage
magnitudes of generator buses, while the discrete ones are
transformer-tap settings. The Lambda iteration based economic
dispatch is used to minimize the fuel cost and active power
dispatch among the generators. During this process, the voltage
magnitude of load buses may move away from the desired value.
The genetic algorithm is applied for optimal reactive
power/voltage dispatch among generators and determination of
tap settings of under load tap changers (ULTCs). This results in
globally improvement of voltage regulation of load buses.
Considering the fact that the reactive power/voltage of generators
are continuous variables while the transformer tap settings are
discrete variables, a method is proposed to combine these
variables into one suitable chromosome. The IEEE 30-bus test
system is used to illustrate the effectiveness and feasibility of
proposed approach.
mmf causes torque and speed pulsations. This paper presents a
new method to eliminate the instantaneous backward mmf to
improve the performance of the single phase induction motor. In
the proposed method a calculated reference current which is in
quadrature with main winding current instantaneously, is
injected to the auxiliary winding. The “Hilbert transformation”
is used for obtaining the reference current of auxiliary winding
by using the current of main winding. The proposed control
scheme is simple and it does not need any position or speed
encoder sensors. Basic system operation and theoretical analysis are discussed and simulation results in comparison with conventional method which uses sinusoidal voltage supply are presented to validate performance of the proposed method.
new structure of non superconducting fault current limiter
(NSFCL) is discussed. This structure prevents voltage sags on
Point of Common Coupling (PCC) just after fault occurrence,
because of its fast operation. On the other hand, previously used
structures produce harmonics on load voltage and have ac losses
in normal operation. New structure has solved this problem by
using dc voltage source. The proposed structure is simulated
using PSCAD/EMTDC software and simulation results are
presented to validate the effectiveness of this structure.
efficient solution to alleviate transmission lines over loadings.
Minimization of total load shedding considering loads importance has great significance in these situations. This problem requires simultaneous optimization of two or more conflicting objectives, such as minimization of the total load shedding, minimization of transmission lines over loadings and voltage violations minimization. The objectives are in conflict since the improvement of one of them leads to the eterioration of another.
A modified version of Non-Dominated Sorting Genetic Algorithm (NSGA-II) is used as an effective optimization tools for solving the minimum weighted load shedding problem during contingency conditions. Also relation between transmission lines overloading and amount of load shedding is surveyed. IEEE 14 bus test system is used as a study case and results are discussed.
Single Machine Infinite Bus (SMIB) system with a double circuit
transmission line using a Non-superconducting Fault Current
Limiter (NSFCL) is proposed. Stability analysis for such system
is discussed in detail. It is shown that, the stability depends on the
resistance of NSFCL in fault condition. To effective improvement
of stability, the optimum value of NSFCL resistance is calculated.
Simulation results by PSCAD/EMTDC software are presented to
confirm the analytic analysis accuracy.
Fault Current Limiter (FCL). This structure has low cast because
of using dry capacitor and non-superconducting inductor and
fast operation. The proposed FCL is able to limit fault current in
constant value near to pre-fault condition value against series
resonance type FCL. In this way, the voltage of point of common
coupling (PCC) will not change during fault. Analytical analysis
is presented in detail and simulation results are involved to
validate the effectiveness of this structure.
concerned. Conventional solutions that use lead acid
batteries and diesel engines as sources of energy for both
uninterruptible power supply (UPS) and isolated power
generation systems are facing an increasing opposition due
to environmental and economical concerns. The aim of the
paper is to evaluate the technical feasibility and aspects
related to the use of fuel cells instead of traditional
electrochemical batteries in the UPS. The proposed system
is named FCB-UPS (Fuel Cell Based UPS). However, the
quality of UPS output voltage is important when it supports
the sensitive loads. So, in this paper a new configuration of
UPS based on flying capacitor multicell (FCM) converter is
proposed to produce the multilevel output voltage to
support the sensitive load with sinusoidal voltage. The main
properties of FCM converter, which causes increase in the
number of output voltage levels, are transformer-less
operation and natural self-balancing of flying capacitors
voltages. The proposed configuration is simulated using
PSCAD/EMTDC software and simulation results are
presented to validate its effectiveness.
double fed distribution networks is proposed. In the last
years, fault location on power distribution networks is
receiving especial attention due to the importance of a fast
actuation to clear the fault causes and the resulting reduce
outage time and significantly improve system reliability.
This paper proposes a new fault location algorithm
developed by the direct circuit analysis for balanced and
unbalanced double fed distribution systems, which has not
been investigated due to high complexity. The proposed
algorithm overcomes the limit of the conventional algorithm,
which requires only the balanced system. Simulation results
of our fault location algorithm for the balanced distribution
network with three-phase loads and unbalanced network
with combination of single-phase and three-phase loads are
also presented. Results show that this method has greatly
simplified the derivation of complicated fault location
equation therefore can superiorly enhance the fault location
process is well suited for identifying fault location in
balanced and unbalanced distribution networks in different
fault resistances.
type fault current limiter (FCL) is introduced for enhancement of
transient stability of single machine infinite bus (SMIB) system
with a double circuit transmission line. The optimal value of
resistor during fault to reach the maximum stability of power
system is computed. It is shown that, this optimal value depends
on the fault location and the pre-fault active power of
synchronous generator considering power demand changing. To
show the effectiveness of the proposed FCL, analytical analysis
including transient stability study and optimum resistor value
calculation are presented. In addition, simulation results using
PSCAD /EMTDC software are included to confirm the analytical
analysis accuracy.
limiter (FCL) that is based on series LC resonance circuit. The
proposed FCL uses a high speed switch to put an inductor in
series with a capacitor and make resonance condition between
them. This structure can hold the peak of fault current in the
constant value that is not possible in previously introduced series
resonance type FCLs. In such conditions, if fault continues, power
system will not be experience large short circuit currents. Using
non-superconducting inductor instead of superconducting one,
leads to low construction and maintenance costs in this structure.
In addition, in normal operation, capacitor of this FCL can be
used as a series compensator. Analytical analysis for the proposed
series resonance type FCL is performed in detail. Simulations are
presented using PSCAD/EMTDC software to show the operation
of the proposed FCL. Also, comparison between the proposed
FCL and previous series resonance type FCLs is included in
simulations.
controllers is introduced. This topology is neither series nor
parallel FACTS controller. This controller injects an
additive compensating voltage between each of two phases
of a three phase power line by using a voltage source
inverter (VSI). So, it is named as line to line compensator
(LLC). Analytical analysis and simulation results by
MATLAB/SIMULINK are presented and a test setup is
built to verify the operation of proposed FACTC controller.
includes the selection of optimal conductor size and
capacitor placement in radial distribution network
considering increasing rate of loads. Technical operational
constraints are available conductors and capacitors, voltage
limit, maximum permissible carrying current of conductors
and maximum reactive power could be injected. The power
loss minimization problem is solved using particle swarm
optimization (PSO). By applying this method, final cost of
network planning, losses and their cost are considerably
reduced and voltage profile of the network has improved to
a semiflat shape. Simulation results are investigated on a
practical radial distribution network in Iran (Miandoab
20 kv distribution network), in addition self supporting
cables are used for optimization which avoids illegal use of
electricity.
type fault current limiter (FCL) is presented in single
machine infinite bus (SMIB) system with a double circuit
transmission line. Three single-phase sets of the proposed
FCL are installed at the beginning of feeder. The proposed
FCL inserts an inductance and a resistance in the fault
current pass. The insertion inductance and resistance not
only limits the fault current level in an acceptable value but
also improves transient stability of power system by
consuming excessive energy of synchronous generator
during fault. To reach maximum transient stability, the
optimal resistor value of the proposed FCL is calculated.
Analytical analysis and simulation results using
PSCAD/EMTDC software are presented to show the
current limiting future and transient stability enhancement
using the proposed FCL in SMIB.