Abstract This paper investigates the use of Discrete Linear Quadratic Gaussian (DLQG) Compensator to damp sub synchronous oscillations in a Thyrisor Controlled Series Capacitor (TCSC) compensated power system. The study is conducted on IEEE First Benchmark Model (FBM) in which, TCSC is modelled as a discrete linear time-invariant modular unit in the synchronously rotating DQ reference frame. This modular TCSC is then integrated with the Linear Time Invariant (LTI) model of the rest of the system. The design of DLQG includes the design of a Kalman filter for full state estimation and a full state feedback for control. Since the order of the controller is as large as the order of the system considered here(27 states), the practical implementation of the controller is difficult. Hence by using Hankels norm approximation technique, the order of the controller is reduced from 27 to 15 without losing the significant system dynamics. The eigen analysis of the system shows that the use of DLQG can damp torsional oscillations as well as the swing mode oscillations simultaneously, which is practically difficult for a conventional sub-synchronous damping controller. The performance of the system with DLQG is appreciable for all operating conditions and it shows the robustness of the controller. Index Terms: Sub-Synchronous Resonance (SSR), Torsional Oscillations, Thyristor Controlled Series Capacitor (TCSC), Discrete Linear Quadratic Gaussian(DLQG)Compensator, Model Order Reduction (MOR).
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Power System State Estimation - A ReviewIDES Editor
The aim of this article is to provide a comprehensive
survey on power system state estimation techniques. The
algorithms used for finding the system states under both static
and dynamic state estimations are discussed in brief. The
authors are opinion that the scope of pursuing research in the
area of state estimation with PMU and SCADA measurements
is the state of the art and timely.
DAMPING INTER-AREA OSCILLATIONS IN POWER SYSTEMS USING A CDM-BASED PID CONTRO...Power System Operation
The interconnected energy transport system is the
mechanism that provides the stability of energy, or
the balance, between the centers of production and
consumption throughout the country. The
interconnected system adapts energy production to
changes in consumption. For many years, because of
long transmission lines or high-value power
transmission in weak-connected power systems, one
of the problems encountered is the existence of lowfrequency
oscillations between generator groups [1,
2]. These inter-area oscillations are a significant
issue in power system stability and control areas.
Modern power systems possess three main
properties: (1) the measure of interconnected system
is getting larger; (2) there is a closer operating point
to the power system stability limit because of
environmental and economic conditions; (3) being
composed of new elements and keeping pace with
technological developments unfortunately cause new
uncertainties in the stability of power systems. These
properties increase the risk of formation of lowfrequency
oscillations [3].
The aim of this paper is to prove that fuzzy logic algorithm is a suitable control technique for fast processes such as electrical machines. This theory has been experimented on different kinds of electrical machines such as stepping motors, dc motors and induction machines (with 6 phases) and the experimental results show that the proposed fuzzy logic algorithm is the most suitable control technique for electrical machines since this algorithm is not time consuming and it is also robust between plant parameters variations.
Open switch fault diagnosis in three phase inverter using diagnostic variable...eSAT Journals
The reliability of power electronics system such as three phase inverter is important in various applications. Different types of faults occur in it, which may influence the operation of system. Such faults require unexpected maintenance, which increases the cost of manufacturing. Therefore fault diagnosis of such devices plays vital role in industry. One possible fault that occurs in inverter is an open switch fault. This paper provides a new technique based on diagnostic variable which detects single as well as multiple open switch fault in three phase inverter. In this method, diagnostic variables are used to detect faulty phase. Along with these diagnostic variables, an average current of three phase inverter is used for the detection of single as well as multiple faulty switches. Key Words: Power electronics, open switch fault, diagnostic variables.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Power System State Estimation - A ReviewIDES Editor
The aim of this article is to provide a comprehensive
survey on power system state estimation techniques. The
algorithms used for finding the system states under both static
and dynamic state estimations are discussed in brief. The
authors are opinion that the scope of pursuing research in the
area of state estimation with PMU and SCADA measurements
is the state of the art and timely.
DAMPING INTER-AREA OSCILLATIONS IN POWER SYSTEMS USING A CDM-BASED PID CONTRO...Power System Operation
The interconnected energy transport system is the
mechanism that provides the stability of energy, or
the balance, between the centers of production and
consumption throughout the country. The
interconnected system adapts energy production to
changes in consumption. For many years, because of
long transmission lines or high-value power
transmission in weak-connected power systems, one
of the problems encountered is the existence of lowfrequency
oscillations between generator groups [1,
2]. These inter-area oscillations are a significant
issue in power system stability and control areas.
Modern power systems possess three main
properties: (1) the measure of interconnected system
is getting larger; (2) there is a closer operating point
to the power system stability limit because of
environmental and economic conditions; (3) being
composed of new elements and keeping pace with
technological developments unfortunately cause new
uncertainties in the stability of power systems. These
properties increase the risk of formation of lowfrequency
oscillations [3].
The aim of this paper is to prove that fuzzy logic algorithm is a suitable control technique for fast processes such as electrical machines. This theory has been experimented on different kinds of electrical machines such as stepping motors, dc motors and induction machines (with 6 phases) and the experimental results show that the proposed fuzzy logic algorithm is the most suitable control technique for electrical machines since this algorithm is not time consuming and it is also robust between plant parameters variations.
Open switch fault diagnosis in three phase inverter using diagnostic variable...eSAT Journals
The reliability of power electronics system such as three phase inverter is important in various applications. Different types of faults occur in it, which may influence the operation of system. Such faults require unexpected maintenance, which increases the cost of manufacturing. Therefore fault diagnosis of such devices plays vital role in industry. One possible fault that occurs in inverter is an open switch fault. This paper provides a new technique based on diagnostic variable which detects single as well as multiple open switch fault in three phase inverter. In this method, diagnostic variables are used to detect faulty phase. Along with these diagnostic variables, an average current of three phase inverter is used for the detection of single as well as multiple faulty switches. Key Words: Power electronics, open switch fault, diagnostic variables.
Comparative Analysis of Power System Stabilizer using Artificial Intelligence...ijsrd.com
Power system stabilizers (PSSs) are used to enhance the damping during low frequency oscillations. The paper presents study of power system stabilizer using fuzzy logic and neural network to enhance stability of single machine infinite bus system. In this paper basic problem of conventional power system stabilizer for stability enhancement is defined which is traditionally used. Artificial intelligence techniques provide one alternative for stability enhancement and speed deviation (Δw). The proposed method using Artificial intelligence techniques achieves better improvement than conventional power system stabilizer. Fuzzy logic rules were developed for triangular membership function of input and output variables. Neuro controller is implemented and it is compared with reference model. The system is simulated in SIMULINK environment and the performances of conventional, Fuzzy based and Neural network based power system stabilizers are compared.
Steady state stability analysis and enhancement of three machine nine bus pow...eSAT Journals
Abstract
Power System stability study is the important parameter of economic, reliable and secure system planning and operation. Studies
are important during the planning and conceptual design stages of the project as well as during the operating life of the plant
periodically. This paper presents the power system steady state stability analysis for IEEE- 9 bus test system and examines
influence of TCPS FACTS device based controller on test system. It is assumed that system under study has been perturbed from a
steady state equilibrium that prevailed prior to the application of the disturbance. If system is stable, we would expect that for
temporary or permanent disturbance, system will acquire initial or new operating state after a transient period. The stability
study is accessed using Lyapunov’s first method. The effectiveness of damping controller in enhancing the steady state stability is
investigated by incorporating available constraints. For analysis MATLAB software is employed. The conclusions have been
drawn here, based on theoretical and mathematical analysis so as to provide an insight and better understanding of steady state
stability of considered multi machine power system.
Key Words: Lyapunov’s first method, Steady-state stability, Phase portrait, FACTS device, supplementary modulation
controller, eigen value, synchronizing power coefficient, IEEE-9 Bus Test System, Load Flow Study, Differential
algebraic equation.
State Estimation of Power System with Interline Power Flow ControllerIDES Editor
Now-a-days Flexible A.C. Transmission
System (FACTS) controllers are incorporated into the
power system network to control the power flow and
enhance system stability. Traditional state estimation
methods without integrating FACTS devices will not be
suitable for power systems embedded with FACTS
controller. Based on the conventional power system state
estimation model, a new method is proposed wherein an
IPFC based power injection model is incorporated in the
state estimation algorithm. Interline power flow controller
(IPFC) is one of the versatile FACTS device. The
proposed method is tested on Anderson and Fouad 9-bus
test system and the results are presented.
WAMS-Based SSR Damping Controller Design for FACTS Devices and Investigating ...IJPEDS-IAES
Recent technological progresses in the wide-area measurement systems
(WAMS) are realizing the centralized controls as a breakthrough for
improving the power systems stability. The most challenging deficiency
against WAMS technology is related to communication delays. If this latency
is neglected, it can deteriorate the damping performance of closed loop
control or even degrade the system stability. This paper investigates a
conventional Wide Area Damping Controller (WADC) for a static
synchronous series compensator (SSSC) to damp out the Sub-Synchronous
Resonance (SSR) and also investigation of the destructive effect of time
delay in remote feedback signal. A new optimization algorithm called
teaching-learning-based- optimization (TLBO) algorithm has been
implemented to normalize and optimize the parameters of the global SSR
damping controller. The IEEE Second Benchmark Model is considered as the
system under study and all simulations are carried out in
MATLAB/SIMULINK environment.
Neural network based vector control of induction motorcsandit
Stator current drift compensation of induction motor based on RBF neural network is proposed
here. In vector control of induction motor decoupling of speed and rotor flux equations and
their simultaneous control are used to achieve the highest efficiency and fast dynamic
performance. The highest efficiency is reached when the proper flux is selected and as a result
of dynamic decoupling of speed and rotor flux equations, the rotor flux can be modified to
achieve the highest efficiency and make the speed be at its desired value. The precise control of
these changes can also be done using radial basis function neural network (RBFNN). Once
neural network gets trained then it is able to differentiate between normal and fault conditions
and therefore acts in accordance to the change that could bring back the system to normal
condition. Here, neural network is used to compute the appropriate set of voltage and frequency
to achieve the maximum efficiency for any value of operating torque and motor speed.
NEURAL NETWORK BASED VECTOR CONTROL OF INDUCTION MOTORcsandit
Stator current drift compensation of induction motor based on RBF neural network is proposed here. In vector control of induction motor decoupling of speed and rotor flux equations and their simultaneous control are used to achieve the highest efficiency and fast dynamic
performance. The highest efficiency is reached when the proper flux is selected and as a result of dynamic decoupling of speed and rotor flux equations, the rotor flux can be modified to achieve the highest efficiency and make the speed be at its desired value. The precise control of these changes can also be done using radial basis function neural network (RBFNN). Once
neural network gets trained then it is able to differentiate between normal and fault conditions and therefore acts in accordance to the change that could bring back the system to normal condition. Here, neural network is used to compute the appropriate set of voltage and frequency
to achieve the maximum efficiency for any value of operating torque and motor speed.
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
Transient Stability Assessment and Enhancement in Power SystemIJMER
Power system is subjected to sudden changes in load levels. Stability is an important concept
which determines the stable operation of power system. For the improvement of transient stability the
general methods adopted are fast acting exciters, circuit breakers and reduction in system transfer
reactance. The modern trend is to employ FACTS devices in the existing system for effective utilization
of existing transmission resources. The critical clearing time is a measure to assess transient instability.
Using PSAT, the critical clearing time (CCT) corresponding to various faults are calculated. The most
critical faults were identified using this calculation. The CCT for the critical faults were found to change
with change in operating point. The CCT values are predicted using Artificial Neural Network (ANN) to
study the training effects of ANN. TCSC is selected as the FACTS device for transient stability
enhancement. Particle Swarm Optimization method is used to find the optimal position of TCSC using
the objective function real power loss minimization. The result shows that the technique effectively
increases the transient stability of the system
Design and Performance Analysis of Genetic based PID-PSS with SVC in a Multi-...IDES Editor
Damping of power system oscillations with the help
of proposed optimal Proportional Integral Derivative Power
System Stabilizer (PID-PSS) and Static Var Compensator
(SVC)-based controllers are thoroughly investigated in this
paper. This study presents robust tuning of PID-PSS and
SVC-based controllers using Genetic Algorithms (GA) in
multi machine power systems by considering detailed model
of the generators (model 1.1). The effectiveness of FACTSbased
controllers in general and SVC-based controller in
particular depends upon their proper location. Modal
controllability and observability are used to locate SVC–based
controller. The performance of the proposed controllers is
compared with conventional lead-lag power system stabilizer
(CPSS) and demonstrated on 10 machines, 39 bus New England
test system. Simulation studies show that the proposed genetic
based PID-PSS with SVC based controller provides better
performance.
This present paper includes the study Load Frequency Control (LFC) of power systems with several nonlinearities
like Generation Rate Constraint(GRC) and Boiler Dynamics (BD) including Superconducting
Magnetic Energy Storage (SMES) units using Type-2 Fuzzy System (T2FS) controllers . Here, Load
frequency control problem is dealt with a three – area interconnected system of Thermal-Thermal-Hydal
power system by observing the effects and variations of dynamic responses employing conventional
controller, Type-1 fuzzy controller and T2FS controller considering incremental increase of step
pertubations by 10% in the load. The salient advantage of this controller is its high insensitivity to large
load changes and plant parameter variations even in the presence of non-linearities. As the non-linearities
were considered in the system, the conventional and classical Fuzzy controllers does not provide adequate
control performance with the consideration of above nonlinearities. To overcome this drawback T2FS
Controller has been employed in the system. Therefore, the efficacy of the proposed T2FS controller is
found to be better than that of conventional controller and Type-1 Fuzzy controller in cosidreration with
overshoot, settling time and robustness.
Model based PI power system stabilizer design for damping low frequency oscil...ISA Interchange
This paper explores a two-level control strategy by blending a local controller with a centralized controller for the low frequency oscillations in a power system. The proposed control scheme provides stabilization of local modes using a local controller and minimizes the effect of inter-connection of sub-systems performance through a centralized control. For designing the local controllers in the form of proportional-integral power system stabilizer (PI-PSS), a simple and straight forward frequency domain direct synthesis method is considered that works on use of a suitable reference model which is based on the desired requirements. Several examples both on one machine infinite bus and multi-machine systems taken from the literature are illustrated to show the efficacy of the proposed PI-PSS. The effective damping of the systems is found to be increased remarkably which is reflected in the time-responses; even unstable operation has been stabilized with improved damping after applying the proposed controller. The proposed controllers give remarkable improvement in damping the oscillations in all the illustrations considered here and as for example, the value of damping factor has been increased from 0.0217 to 0.666 in Example 1. The simulation results obtained by the proposed control strategy are favorably compared with some controllers prevalent in the literature.
Using Simple PID Controllers to Prevent and Mitigate Faults in Scientific Wor...Rafael Ferreira da Silva
Presentation held at the 11th Workflows in Support of Large-Scale Science, October 14, 2016.
Abstract - Scientific workflows have become mainstream for conducting large-scale scientific research. As a result, many workflow applications and Workflow Management Systems (WMSs) have been developed as part of the cyberinfrastructure to allow scientists to execute their applications seamlessly on a range of distributed platforms. In spite of many success stories, a key challenge for running workflows in distributed systems is failure prediction, detection, and recovery. In this paper, we propose an approach to use control theory developed as part of autonomic computing to predict failures before they happen, and mitigated them when possible. The proposed approach applying the proportional-integral-derivative controller (PID controller) control loop mechanism, which is widely used in industrial control systems, to mitigate faults by adjusting the inputs of the controller. The PID controller aims at detecting the possibility of a fault far enough in advance so that an action can be performed to prevent it from happening. To demonstrate the feasibility of the approach, we tackle two common execution faults of the Big Data era---data storage overload and memory overflow. We define, implement, and evaluate simple PID controllers to autonomously manage data and memory usage of a bioinformatics workflow that consumes/produces over 4.4TB of data, and requires over 24TB of memory to run all tasks concurrently. Experimental results indicate that workflow executions may significantly benefit from PID controllers, in particular under online and unknown conditions. Simulation results show that nearly-optimal executions (slowdown of 1.01) can be attained when using our proposed method, and faults are detected and mitigated far in advance of their occurrence.
Comparative Analysis of Power System Stabilizer using Artificial Intelligence...ijsrd.com
Power system stabilizers (PSSs) are used to enhance the damping during low frequency oscillations. The paper presents study of power system stabilizer using fuzzy logic and neural network to enhance stability of single machine infinite bus system. In this paper basic problem of conventional power system stabilizer for stability enhancement is defined which is traditionally used. Artificial intelligence techniques provide one alternative for stability enhancement and speed deviation (Δw). The proposed method using Artificial intelligence techniques achieves better improvement than conventional power system stabilizer. Fuzzy logic rules were developed for triangular membership function of input and output variables. Neuro controller is implemented and it is compared with reference model. The system is simulated in SIMULINK environment and the performances of conventional, Fuzzy based and Neural network based power system stabilizers are compared.
Steady state stability analysis and enhancement of three machine nine bus pow...eSAT Journals
Abstract
Power System stability study is the important parameter of economic, reliable and secure system planning and operation. Studies
are important during the planning and conceptual design stages of the project as well as during the operating life of the plant
periodically. This paper presents the power system steady state stability analysis for IEEE- 9 bus test system and examines
influence of TCPS FACTS device based controller on test system. It is assumed that system under study has been perturbed from a
steady state equilibrium that prevailed prior to the application of the disturbance. If system is stable, we would expect that for
temporary or permanent disturbance, system will acquire initial or new operating state after a transient period. The stability
study is accessed using Lyapunov’s first method. The effectiveness of damping controller in enhancing the steady state stability is
investigated by incorporating available constraints. For analysis MATLAB software is employed. The conclusions have been
drawn here, based on theoretical and mathematical analysis so as to provide an insight and better understanding of steady state
stability of considered multi machine power system.
Key Words: Lyapunov’s first method, Steady-state stability, Phase portrait, FACTS device, supplementary modulation
controller, eigen value, synchronizing power coefficient, IEEE-9 Bus Test System, Load Flow Study, Differential
algebraic equation.
State Estimation of Power System with Interline Power Flow ControllerIDES Editor
Now-a-days Flexible A.C. Transmission
System (FACTS) controllers are incorporated into the
power system network to control the power flow and
enhance system stability. Traditional state estimation
methods without integrating FACTS devices will not be
suitable for power systems embedded with FACTS
controller. Based on the conventional power system state
estimation model, a new method is proposed wherein an
IPFC based power injection model is incorporated in the
state estimation algorithm. Interline power flow controller
(IPFC) is one of the versatile FACTS device. The
proposed method is tested on Anderson and Fouad 9-bus
test system and the results are presented.
WAMS-Based SSR Damping Controller Design for FACTS Devices and Investigating ...IJPEDS-IAES
Recent technological progresses in the wide-area measurement systems
(WAMS) are realizing the centralized controls as a breakthrough for
improving the power systems stability. The most challenging deficiency
against WAMS technology is related to communication delays. If this latency
is neglected, it can deteriorate the damping performance of closed loop
control or even degrade the system stability. This paper investigates a
conventional Wide Area Damping Controller (WADC) for a static
synchronous series compensator (SSSC) to damp out the Sub-Synchronous
Resonance (SSR) and also investigation of the destructive effect of time
delay in remote feedback signal. A new optimization algorithm called
teaching-learning-based- optimization (TLBO) algorithm has been
implemented to normalize and optimize the parameters of the global SSR
damping controller. The IEEE Second Benchmark Model is considered as the
system under study and all simulations are carried out in
MATLAB/SIMULINK environment.
Neural network based vector control of induction motorcsandit
Stator current drift compensation of induction motor based on RBF neural network is proposed
here. In vector control of induction motor decoupling of speed and rotor flux equations and
their simultaneous control are used to achieve the highest efficiency and fast dynamic
performance. The highest efficiency is reached when the proper flux is selected and as a result
of dynamic decoupling of speed and rotor flux equations, the rotor flux can be modified to
achieve the highest efficiency and make the speed be at its desired value. The precise control of
these changes can also be done using radial basis function neural network (RBFNN). Once
neural network gets trained then it is able to differentiate between normal and fault conditions
and therefore acts in accordance to the change that could bring back the system to normal
condition. Here, neural network is used to compute the appropriate set of voltage and frequency
to achieve the maximum efficiency for any value of operating torque and motor speed.
NEURAL NETWORK BASED VECTOR CONTROL OF INDUCTION MOTORcsandit
Stator current drift compensation of induction motor based on RBF neural network is proposed here. In vector control of induction motor decoupling of speed and rotor flux equations and their simultaneous control are used to achieve the highest efficiency and fast dynamic
performance. The highest efficiency is reached when the proper flux is selected and as a result of dynamic decoupling of speed and rotor flux equations, the rotor flux can be modified to achieve the highest efficiency and make the speed be at its desired value. The precise control of these changes can also be done using radial basis function neural network (RBFNN). Once
neural network gets trained then it is able to differentiate between normal and fault conditions and therefore acts in accordance to the change that could bring back the system to normal condition. Here, neural network is used to compute the appropriate set of voltage and frequency
to achieve the maximum efficiency for any value of operating torque and motor speed.
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
Transient Stability Assessment and Enhancement in Power SystemIJMER
Power system is subjected to sudden changes in load levels. Stability is an important concept
which determines the stable operation of power system. For the improvement of transient stability the
general methods adopted are fast acting exciters, circuit breakers and reduction in system transfer
reactance. The modern trend is to employ FACTS devices in the existing system for effective utilization
of existing transmission resources. The critical clearing time is a measure to assess transient instability.
Using PSAT, the critical clearing time (CCT) corresponding to various faults are calculated. The most
critical faults were identified using this calculation. The CCT for the critical faults were found to change
with change in operating point. The CCT values are predicted using Artificial Neural Network (ANN) to
study the training effects of ANN. TCSC is selected as the FACTS device for transient stability
enhancement. Particle Swarm Optimization method is used to find the optimal position of TCSC using
the objective function real power loss minimization. The result shows that the technique effectively
increases the transient stability of the system
Design and Performance Analysis of Genetic based PID-PSS with SVC in a Multi-...IDES Editor
Damping of power system oscillations with the help
of proposed optimal Proportional Integral Derivative Power
System Stabilizer (PID-PSS) and Static Var Compensator
(SVC)-based controllers are thoroughly investigated in this
paper. This study presents robust tuning of PID-PSS and
SVC-based controllers using Genetic Algorithms (GA) in
multi machine power systems by considering detailed model
of the generators (model 1.1). The effectiveness of FACTSbased
controllers in general and SVC-based controller in
particular depends upon their proper location. Modal
controllability and observability are used to locate SVC–based
controller. The performance of the proposed controllers is
compared with conventional lead-lag power system stabilizer
(CPSS) and demonstrated on 10 machines, 39 bus New England
test system. Simulation studies show that the proposed genetic
based PID-PSS with SVC based controller provides better
performance.
This present paper includes the study Load Frequency Control (LFC) of power systems with several nonlinearities
like Generation Rate Constraint(GRC) and Boiler Dynamics (BD) including Superconducting
Magnetic Energy Storage (SMES) units using Type-2 Fuzzy System (T2FS) controllers . Here, Load
frequency control problem is dealt with a three – area interconnected system of Thermal-Thermal-Hydal
power system by observing the effects and variations of dynamic responses employing conventional
controller, Type-1 fuzzy controller and T2FS controller considering incremental increase of step
pertubations by 10% in the load. The salient advantage of this controller is its high insensitivity to large
load changes and plant parameter variations even in the presence of non-linearities. As the non-linearities
were considered in the system, the conventional and classical Fuzzy controllers does not provide adequate
control performance with the consideration of above nonlinearities. To overcome this drawback T2FS
Controller has been employed in the system. Therefore, the efficacy of the proposed T2FS controller is
found to be better than that of conventional controller and Type-1 Fuzzy controller in cosidreration with
overshoot, settling time and robustness.
Model based PI power system stabilizer design for damping low frequency oscil...ISA Interchange
This paper explores a two-level control strategy by blending a local controller with a centralized controller for the low frequency oscillations in a power system. The proposed control scheme provides stabilization of local modes using a local controller and minimizes the effect of inter-connection of sub-systems performance through a centralized control. For designing the local controllers in the form of proportional-integral power system stabilizer (PI-PSS), a simple and straight forward frequency domain direct synthesis method is considered that works on use of a suitable reference model which is based on the desired requirements. Several examples both on one machine infinite bus and multi-machine systems taken from the literature are illustrated to show the efficacy of the proposed PI-PSS. The effective damping of the systems is found to be increased remarkably which is reflected in the time-responses; even unstable operation has been stabilized with improved damping after applying the proposed controller. The proposed controllers give remarkable improvement in damping the oscillations in all the illustrations considered here and as for example, the value of damping factor has been increased from 0.0217 to 0.666 in Example 1. The simulation results obtained by the proposed control strategy are favorably compared with some controllers prevalent in the literature.
Using Simple PID Controllers to Prevent and Mitigate Faults in Scientific Wor...Rafael Ferreira da Silva
Presentation held at the 11th Workflows in Support of Large-Scale Science, October 14, 2016.
Abstract - Scientific workflows have become mainstream for conducting large-scale scientific research. As a result, many workflow applications and Workflow Management Systems (WMSs) have been developed as part of the cyberinfrastructure to allow scientists to execute their applications seamlessly on a range of distributed platforms. In spite of many success stories, a key challenge for running workflows in distributed systems is failure prediction, detection, and recovery. In this paper, we propose an approach to use control theory developed as part of autonomic computing to predict failures before they happen, and mitigated them when possible. The proposed approach applying the proportional-integral-derivative controller (PID controller) control loop mechanism, which is widely used in industrial control systems, to mitigate faults by adjusting the inputs of the controller. The PID controller aims at detecting the possibility of a fault far enough in advance so that an action can be performed to prevent it from happening. To demonstrate the feasibility of the approach, we tackle two common execution faults of the Big Data era---data storage overload and memory overflow. We define, implement, and evaluate simple PID controllers to autonomously manage data and memory usage of a bioinformatics workflow that consumes/produces over 4.4TB of data, and requires over 24TB of memory to run all tasks concurrently. Experimental results indicate that workflow executions may significantly benefit from PID controllers, in particular under online and unknown conditions. Simulation results show that nearly-optimal executions (slowdown of 1.01) can be attained when using our proposed method, and faults are detected and mitigated far in advance of their occurrence.
The objective of this project is to design a wind turbine that is optimized for the constraints that come with residential use. The main tasks of this project are:
> To study the design process and methodology of wind turbine
> Derive the Blade Element Momentum (BEM) theory then use it to conduct a parametric study that will determine if the optimized values of blade pitch and chord length create the most efficient blade geometry
> Analyse different air-foils to determine which one creates the most efficient wind turbine blade.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Power System MIMO Identification for Coordinated Design of PSS and TCSC Contr...Reza Pourramezan
Authors: Reza Pourramezan, Sadegh Vaez-Zadeh, and Hamid Reza Nourzadeh
Published in 2007 IEEE Power Engineering Society General Meeting (PES)
DOI: 10.1109/PES.2007.385692
Comparison of Different Design Methods for Power System Stabilizer Design - A...ijsrd.com
In the past two decades, the utilization of supplementary excitation control signals for improving the dynamic stability of power systems has received much attention. In recent years, several approaches based on intelligent control and optimization techniques have been applied to PSS design problem. This paper introduces a review on the techniques applied on the conventional PSS design only. Power System Stabilizer (PSS) is the most cost effective approach of increase the system positive damping, improve the steady-state stability margin, and suppress the low-frequency oscillation of the power system. A PSS has to perform well under operating point variations. This paper introduces a review on the techniques applied on the conventional PSS design only. The techniques could be mainly classified into linear and nonlinear.
OPTIMAL TORQUE RIPPLE CONTROL OF ASYNCHRONOUS DRIVE USING INTELLIGENT CONTROL...elelijjournal
The dynamic performance of an asynchronous machine when operated with cascaded Voltage Source Inverter using Space Vector Modulation (SVM) technique is presented in this paper. A classical model of Induction Motor Drive based on Direct Torque Control (DTC) method is considered which displays
appreciable run-time operation with very simple hysteresis control scheme. Direct control of the torque and flux variables is achieved by choosing suitable inverter voltage space vector from a lookup table. Under varying torque conditions the performance of the drive system is verified using MATLAB/Simulink software tool. The ripple content in the torque parameter is significant when traditional PI controller and Fuzzy approach are configured in the proposed system. Finally, by replacing the PI-Fuzzy controller with Hybrid Controller the torque ripple minimization can be achieved during no-load and loaded conditions.
Damping of Inter-Area Low Frequency Oscillation Using an Adaptive Wide-Area D...Power System Operation
This paper presents an adaptive wide-area damping controller (WADC) based on
generalized predictive control (GPC) and model identification for damping the inter-area low
frequency oscillations in large-scale inter-connected power system. A recursive least-squares algorithm
(RLSA) with a varying forgetting factor is applied to identify online the reduced-order linearlized
model which contains dominant inter-area low frequency oscillations. Based on this linearlized model,
the generalized predictive control scheme considering control output constraints is employed to obtain
the optimal control signal in each sampling interval. Case studies are undertaken on a two-area fourmachine
power system and the New England 10-machine 39-bus power system, respectively.
Simulation results show that the proposed adaptive WADC not only can damp the inter-area
oscillations effectively under a wide range of operation conditions and different disturbances, but also
has better robustness against to the time delay existing in the remote signals. The comparison studies
with the conventional lead-lag WADC are also provided.
Neural Network-Based Stabilizer for the Improvement of Power System Dynamic P...TELKOMNIKA JOURNAL
This paper develops an adaptive control coordination scheme for power system stabilizers (PSSs)
to improve the oscillation damping and dynamic performance of interconnected multimachine power
system. The scheme was based on the use of a neural network which identifies online the optimal
controller parameters. The inputs to the neural network include the active- and reactive- power of the
synchronous generators which represent the power loading on the system, and elements of the reduced
nodal impedance matrix for representing the power system configuration. The outputs of the neural
network were the parameters of the PSSs which lead to optimal oscillation damping for the prevailing
system configuration and operating condition. For a representative power system, the neural network has
been trained and tested for a wide range of credible operating conditions and contingencies. Both
eigenvalue calculations and time-domain simulations were used in the testing and verification of the
performance of the neural network-based stabilizer.
Future approach to mitigate Inter-Area Oscillations in GCC Combined SystemPower System Operation
Inter-Area power oscillations is one of the major concerns for GCC Combined System Operators, as it is diminishing tie-lines Available Transfer Capacity and threatening System Security. This paper presents outcomes of recent modal analyses study carried out on a Combined System model. It also shows real-time oscillations recorded and analyzed by Wide Area Monitoring System (WAMS) owned by Gulf Cooperation Council Interconnection Authority (GCCIA).
The damping characteristic of the inter-area mode is dictated by the tie-line strength, the nature of the loads, and the power flow through the interconnection and the interaction of loads with the dynamics of generators and their associated controls. Therefore, it is a very challenging task to tune power system stabilizers (PSS) to damp sufficiently well both local and inter-area modes of oscillations based on local feedback signals only. The secure operation of the Combined System requires application of robust control strategy that is effective to damp inter-area oscillations over wide operating range.
Referring to the recent development of WAMS, it is worth to consider new methods to mitigate Inter-Area oscillations in the Combined System. Tuning of PSS for damping Inter-Area oscillations based on WAMS, and enhancement of damping performance of generators through wide-area controller, i.e. remote measured signals obtained using synchronized Phasor Measurements Units (PMUs) transmitted in real-time via communication network, are two proposed options for study.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Comparison of backstepping, sliding mode and PID regulators for a voltage inv...IJECEIAES
In the present paper, an efficient and performant nonlinear regulator is designed for the control of the pulse width modulation (PWM) voltage inverter that can be used in a standalone photovoltaic microgrid. The main objective of our control is to produce a sinusoidal voltage output signal with amplitude and frequency that are fixed by the reference signal for different loads including linear or nonlinear types. A comparative performance study of controllers based on linear and non-linear techniques such as backstepping, sliding mode, and proportional integral derivative (PID) is developed to ensure the best choice among these three types of controllers. The performance of the system is investigated and compared under various operating conditions by simulations in the MATLAB/Simulink environment to demonstrate the effectiveness of the control methods. Our investigation shows that the backstepping controller can give better performance than the sliding mode and PID controllers. The accuracy and efficiency of the proposed backstepping controller are verified experimentally in terms of tracking objectives.
International Journal of Engineering Inventions (IJEI) provides a multidisciplinary passage for researchers, managers, professionals, practitioners and students around the globe to publish high quality, peer-reviewed articles on all theoretical and empirical aspects of Engineering and Science.
The peer-reviewed International Journal of Engineering Inventions (IJEI) is started with a mission to encourage contribution to research in Science and Technology. Encourage and motivate researchers in challenging areas of Sciences and Technology.
Enhancement of Power System Dynamics Using a Novel Series Compensation SchemeIJMER
Phase imbalanced capacitive compensation is a “hybrid” series compensation scheme, where the
series capacitive compensation in one phase is created using a single-phase TCSC in series with a fixed capacitor
(Cc), and the other two phases are compensated by fixed series capacitors (C). The TCSC control is initially set
such that its equivalent compensations at the power frequency combined with the fixed capacitor yield a
resultant compensation equal to the other two phases. Thus, the phase balance is maintained at the power
frequency while at any other frequency, a phase imbalance is created. The effectiveness of the scheme in damping
power system oscillations for various network conditions, namely different system faults and tie-line power flows is
evaluated using the MATLAB/SIMULINK Software
Frequency Response Assessment: Parameter Identification of Simplified Governo...Power System Operation
With a growing share of inverter-interfaced generation
in modern power systems, synchronous inertia is
declining. This leads to faster frequency drop after large
generation trip events. During low inertia conditions,
frequency containment reserves might not be sufficient
to arrest frequency before it reaches the threshold for
underfrequency load shedding. It is therefore becoming
increasingly important for system operators to be able to
assess frequency response in near real time. In contrast to
detailed models, simplified models offer short simulation
times and their parameters can be accurately identified
and adapted to changing system conditions in near real
time. In this paper, the parameters of governor response
models are identified by minimizing the error residuals
between the simulation models’ and the actual system’s
measured active power response. This is accomplished
by using historic event data from two system operators:
the Electric Reliability Council Of Texas (ERCOT) and
the Swedish Svenska kraftnät (Svk). Then, the respective
frequency response models are simulated to assess
frequency response. The results show that, despite their
simplicity, the models provide a very good fit compared
to the actual response. The models of ERCOT and
Svk are examined; however, a similar approach can be
employed to represent the frequency response of other
power systems.
Similar to A robust dlqg controller for damping of sub synchronous oscillations in a series compensated power system (20)
Mechanical properties of hybrid fiber reinforced concrete for pavementseSAT Journals
Abstract
The effect of addition of mono fibers and hybrid fibers on the mechanical properties of concrete mixture is studied in the present
investigation. Steel fibers of 1% and polypropylene fibers 0.036% were added individually to the concrete mixture as mono fibers and
then they were added together to form a hybrid fiber reinforced concrete. Mechanical properties such as compressive, split tensile and
flexural strength were determined. The results show that hybrid fibers improve the compressive strength marginally as compared to
mono fibers. Whereas, hybridization improves split tensile strength and flexural strength noticeably.
Keywords:-Hybridization, mono fibers, steel fiber, polypropylene fiber, Improvement in mechanical properties.
Material management in construction – a case studyeSAT Journals
Abstract
The objective of the present study is to understand about all the problems occurring in the company because of improper application
of material management. In construction project operation, often there is a project cost variance in terms of the material, equipments,
manpower, subcontractor, overhead cost, and general condition. Material is the main component in construction projects. Therefore,
if the material management is not properly managed it will create a project cost variance. Project cost can be controlled by taking
corrective actions towards the cost variance. Therefore a methodology is used to diagnose and evaluate the procurement process
involved in material management and launch a continuous improvement was developed and applied. A thorough study was carried
out along with study of cases, surveys and interviews to professionals involved in this area. As a result, a methodology for diagnosis
and improvement was proposed and tested in selected projects. The results obtained show that the main problem of procurement is
related to schedule delays and lack of specified quality for the project. To prevent this situation it is often necessary to dedicate
important resources like money, personnel, time, etc. To monitor and control the process. A great potential for improvement was
detected if state of the art technologies such as, electronic mail, electronic data interchange (EDI), and analysis were applied to the
procurement process. These helped to eliminate the root causes for many types of problems that were detected.
Managing drought short term strategies in semi arid regions a case studyeSAT Journals
Abstract
Drought management needs multidisciplinary action. Interdisciplinary efforts among the experts in various fields of the droughts
prone areas are helpful to achieve tangible and permanent solution for this recurring problem. The Gulbarga district having the total
area around 16, 240 sq.km, and accounts 8.45 per cent of the Karnataka state area. The district has been situated with latitude 17º 19'
60" North and longitude of 76 º 49' 60" east. The district is situated entirely on the Deccan plateau positioned at a height of 300 to
750 m above MSL. Sub-tropical, semi-arid type is one among the drought prone districts of Karnataka State. The drought
management is very important for a district like Gulbarga. In this paper various short term strategies are discussed to mitigate the
drought condition in the district.
Keywords: Drought, South-West monsoon, Semi-Arid, Rainfall, Strategies etc.
Life cycle cost analysis of overlay for an urban road in bangaloreeSAT Journals
Abstract
Pavements are subjected to severe condition of stresses and weathering effects from the day they are constructed and opened to traffic
mainly due to its fatigue behavior and environmental effects. Therefore, pavement rehabilitation is one of the most important
components of entire road systems. This paper highlights the design of concrete pavement with added mono fibers like polypropylene,
steel and hybrid fibres for a widened portion of existing concrete pavement and various overlay alternatives for an existing
bituminous pavement in an urban road in Bangalore. Along with this, Life cycle cost analyses at these sections are done by Net
Present Value (NPV) method to identify the most feasible option. The results show that though the initial cost of construction of
concrete overlay is high, over a period of time it prove to be better than the bituminous overlay considering the whole life cycle cost.
The economic analysis also indicates that, out of the three fibre options, hybrid reinforced concrete would be economical without
compromising the performance of the pavement.
Keywords: - Fatigue, Life cycle cost analysis, Net Present Value method, Overlay, Rehabilitation
Laboratory studies of dense bituminous mixes ii with reclaimed asphalt materialseSAT Journals
Abstract
The issue of growing demand on our nation’s roadways over that past couple of decades, decreasing budgetary funds, and the need to
provide a safe, efficient, and cost effective roadway system has led to a dramatic increase in the need to rehabilitate our existing
pavements and the issue of building sustainable road infrastructure in India. With these emergency of the mentioned needs and this
are today’s burning issue and has become the purpose of the study.
In the present study, the samples of existing bituminous layer materials were collected from NH-48(Devahalli to Hassan) site.The
mixtures were designed by Marshall Method as per Asphalt institute (MS-II) at 20% and 30% Reclaimed Asphalt Pavement (RAP).
RAP material was blended with virgin aggregate such that all specimens tested for the, Dense Bituminous Macadam-II (DBM-II)
gradation as per Ministry of Roads, Transport, and Highways (MoRT&H) and cost analysis were carried out to know the economics.
Laboratory results and analysis showed the use of recycled materials showed significant variability in Marshall Stability, and the
variability increased with the increase in RAP content. The saving can be realized from utilization of recycled materials as per the
methodology, the reduction in the total cost is 19%, 30%, comparing with the virgin mixes.
Keywords: Reclaimed Asphalt Pavement, Marshall Stability, MS-II, Dense Bituminous Macadam-II
Laboratory investigation of expansive soil stabilized with natural inorganic ...eSAT Journals
Abstract
Soil stabilization has proven to be one of the oldest techniques to improve the soil properties. Literature review conducted revealed
that uses of natural inorganic stabilizers are found to be one of the best options for soil stabilization. In this regard an attempt has
been made to evaluate the influence of RBI-81 stabilizer on properties of black cotton soil through laboratory investigations. Black
cotton soil with varying percentages of RBI-81 viz., 0, 0.5, 1, 1.5, 2, and 2.5 percent were studied for moisture density relationships
and strength behaviour of soils. Also the effect of curing period was evaluated as literature review clearly emphasized the strength
gain of soils stabilized with RBI-81 over a period of time. The results obtained shows that the unconfined compressive strength of
specimens treated with RBI-81 increased approximately by 250% for a curing period of 28 days as compared to virgin soil. Further
the CBR value improved approximately by 400%. The studies indicated an increasing trend for soil strength behaviour with
increasing percentage of RBI-81 suggesting its potential applications in soil stabilization.
Influence of reinforcement on the behavior of hollow concrete block masonry p...eSAT Journals
Abstract
Reinforced masonry was developed to exploit the strength potential of masonry and to solve its lack of tensile strength. Experimental
and analytical studies have been carried out to investigate the effect of reinforcement on the behavior of hollow concrete block
masonry prisms under compression and to predict ultimate failure compressive strength. In the numerical program, three dimensional
non-linear finite elements (FE) model based on the micro-modeling approach is developed for both unreinforced and reinforced
masonry prisms using ANSYS (14.5). The proposed FE model uses multi-linear stress-strain relationships to model the non-linear
behavior of hollow concrete block, mortar, and grout. Willam-Warnke’s five parameter failure theory has been adopted to model the
failure of masonry materials. The comparison of the numerical and experimental results indicates that the FE models can successfully
capture the highly nonlinear behavior of the physical specimens and accurately predict their strength and failure mechanisms.
Keywords: Structural masonry, Hollow concrete block prism, grout, Compression failure, Finite element method,
Numerical modeling.
Influence of compaction energy on soil stabilized with chemical stabilizereSAT Journals
Abstract
Increase in traffic along with heavier magnitude of wheel loads cause rapid deterioration in pavements. There is a need to improve
density, strength of soil subgrade and other pavement layers. In this study an attempt is made to improve the properties of locally
available loamy soil using twin approaches viz., i) increasing the compaction of soil and ii) treating the soil with chemical stabilizer.
Laboratory studies are carried out on both untreated and treated soil samples compacted by different compaction efforts. Studies
show that increase in compaction effort results in increase in density of soil. However in soil treated with chemical stabilizer, rate of
increase in density is not significant. The soil treated with chemical stabilizer exhibits improvement in both strength and performance
properties.
Keywords: compaction, density, subgradestabilization, resilient modulus
Geographical information system (gis) for water resources managementeSAT Journals
Abstract
Water resources projects are inherited with overlapping and at times conflicting objectives. These projects are often of varied sizes
ranging from major projects with command areas of millions of hectares to very small projects implemented at the local level. Thus,
in all these projects there is seldom proper coordination which is essential for ensuring collective sustainability.
Integrated watershed development and management is the accepted answer but in turn requires a comprehensive framework that can
enable planning process involving all the stakeholders at different levels and scales is compulsory. Such a unified hydrological
framework is essential to evaluate the cause and effect of all the proposed actions within the drainage basins.
The present paper describes a hydrological framework developed in the form of a Hydrologic Information System (HIS) which is
intended to meet the specific information needs of the various line departments of a typical State connected with water related aspects.
The HIS consist of a hydrologic information database coupled with tools for collating primary and secondary data and tools for
analyzing and visualizing the data and information. The HIS also incorporates hydrological model base for indirect assessment of
various entities of water balance in space and time. The framework would be maintained and updated to reflect fully the most
accurate ground truth data and the infrastructure requirements for planning and management.
Keywords: Hydrological Information System (HIS); WebGIS; Data Model; Web Mapping Services
Forest type mapping of bidar forest division, karnataka using geoinformatics ...eSAT Journals
Abstract
The study demonstrate the potentiality of satellite remote sensing technique for the generation of baseline information on forest types
including tree plantation details in Bidar forest division, Karnataka covering an area of 5814.60Sq.Kms. The Total Area of Bidar
forest division is 5814Sq.Kms analysis of the satellite data in the study area reveals that about 84% of the total area is Covered by
crop land, 1.778% of the area is covered by dry deciduous forest, 1.38 % of mixed plantation, which is very threatening to the
environmental stability of the forest, future plantation site has been mapped. With the use of latest Geo-informatics technology proper
and exact condition of the trees can be observed and necessary precautions can be taken for future plantation works in an appropriate
manner
Keywords:-RS, GIS, GPS, Forest Type, Tree Plantation
Factors influencing compressive strength of geopolymer concreteeSAT Journals
Abstract
To study effects of several factors on the properties of fly ash based geopolymer concrete on the compressive strength and also the
cost comparison with the normal concrete. The test variables were molarities of sodium hydroxide(NaOH) 8M,14M and 16M, ratio of
NaOH to sodium silicate (Na2SiO3) 1, 1.5, 2 and 2.5, alkaline liquid to fly ash ratio 0.35 and 0.40 and replacement of water in
Na2SiO3 solution by 10%, 20% and 30% were used in the present study. The test results indicated that the highest compressive
strength 54 MPa was observed for 16M of NaOH, ratio of NaOH to Na2SiO3 2.5 and alkaline liquid to fly ash ratio of 0.35. Lowest
compressive strength of 27 MPa was observed for 8M of NaOH, ratio of NaOH to Na2SiO3 is 1 and alkaline liquid to fly ash ratio of
0.40. Alkaline liquid to fly ash ratio of 0.35, water replacement of 10% and 30% for 8 and 16 molarity of NaOH and has resulted in
compressive strength of 36 MPa and 20 MPa respectively. Superplasticiser dosage of 2 % by weight of fly ash has given higher
strength in all cases.
Keywords: compressive strength, alkaline liquid, fly ash
Experimental investigation on circular hollow steel columns in filled with li...eSAT Journals
Abstract
Composite Circular hollow Steel tubes with and without GFRP infill for three different grades of Light weight concrete are tested for
ultimate load capacity and axial shortening , under Cyclic loading. Steel tubes are compared for different lengths, cross sections and
thickness. Specimens were tested separately after adopting Taguchi’s L9 (Latin Squares) Orthogonal array in order to save the initial
experimental cost on number of specimens and experimental duration. Analysis was carried out using ANN (Artificial Neural
Network) technique with the assistance of Mini Tab- a statistical soft tool. Comparison for predicted, experimental & ANN output is
obtained from linear regression plots. From this research study, it can be concluded that *Cross sectional area of steel tube has most
significant effect on ultimate load carrying capacity, *as length of steel tube increased- load carrying capacity decreased & *ANN
modeling predicted acceptable results. Thus ANN tool can be utilized for predicting ultimate load carrying capacity for composite
columns.
Keywords: Light weight concrete, GFRP, Artificial Neural Network, Linear Regression, Back propagation, orthogonal
Array, Latin Squares
Experimental behavior of circular hsscfrc filled steel tubular columns under ...eSAT Journals
Abstract
This paper presents an outlook on experimental behavior and a comparison with predicted formula on the behaviour of circular
concentrically loaded self-consolidating fibre reinforced concrete filled steel tube columns (HSSCFRC). Forty-five specimens were
tested. The main parameters varied in the tests are: (1) percentage of fiber (2) tube diameter or width to wall thickness ratio (D/t
from 15 to 25) (3) L/d ratio from 2.97 to 7.04 the results from these predictions were compared with the experimental data. The
experimental results) were also validated in this study.
Keywords: Self-compacting concrete; Concrete-filled steel tube; axial load behavior; Ultimate capacity.
Evaluation of punching shear in flat slabseSAT Journals
Abstract
Flat-slab construction has been widely used in construction today because of many advantages that it offers. The basic philosophy in
the design of flat slab is to consider only gravity forces; this method ignores the effect of punching shear due to unbalanced moments
at the slab column junction which is critical. An attempt has been made to generate generalized design sheets which accounts both
punching shear due to gravity loads and unbalanced moments for cases (a) interior column; (b) edge column (bending perpendicular
to shorter edge); (c) edge column (bending parallel to shorter edge); (d) corner column. These design sheets are prepared as per
codal provisions of IS 456-2000. These design sheets will be helpful in calculating the shear reinforcement to be provided at the
critical section which is ignored in many design offices. Apart from its usefulness in evaluating punching shear and the necessary
shear reinforcement, the design sheets developed will enable the designer to fix the depth of flat slab during the initial phase of the
design.
Keywords: Flat slabs, punching shear, unbalanced moment.
Evaluation of performance of intake tower dam for recent earthquake in indiaeSAT Journals
Abstract
Intake towers are typically tall, hollow, reinforced concrete structures and form entrance to reservoir outlet works. A parametric
study on dynamic behavior of circular cylindrical towers can be carried out to study the effect of depth of submergence, wall thickness
and slenderness ratio, and also effect on tower considering dynamic analysis for time history function of different soil condition and
by Goyal and Chopra accounting interaction effects of added hydrodynamic mass of surrounding and inside water in intake tower of
dam
Key words: Hydrodynamic mass, Depth of submergence, Reservoir, Time history analysis,
Evaluation of operational efficiency of urban road network using travel time ...eSAT Journals
Abstract
Efficiency of the road network system is analyzed by travel time reliability measures. The study overlooks on an important measure of
travel time reliability and prioritizing Tiruchirappalli road network. Traffic volume and travel time were collected using license plate
matching method. Travel time measures were estimated from average travel time and 95th travel time. Effect of non-motorized vehicle
on efficiency of road system was evaluated. Relation between buffer time index and traffic volume was created. Travel time model has
been developed and travel time measure was validated. Then service quality of road sections in network were graded based on
travel time reliability measures.
Keywords: Buffer Time Index (BTI); Average Travel Time (ATT); Travel Time Reliability (TTR); Buffer Time (BT).
Estimation of surface runoff in nallur amanikere watershed using scs cn methodeSAT Journals
Abstract
The development of watershed aims at productive utilization of all the available natural resources in the entire area extending from
ridge line to stream outlet. The per capita availability of land for cultivation has been decreasing over the years. Therefore, water and
the related land resources must be developed, utilized and managed in an integrated and comprehensive manner. Remote sensing and
GIS techniques are being increasingly used for planning, management and development of natural resources. The study area, Nallur
Amanikere watershed geographically lies between 110 38’ and 110 52’ N latitude and 760 30’ and 760 50’ E longitude with an area of
415.68 Sq. km. The thematic layers such as land use/land cover and soil maps were derived from remotely sensed data and overlayed
through ArcGIS software to assign the curve number on polygon wise. The daily rainfall data of six rain gauge stations in and around
the watershed (2001-2011) was used to estimate the daily runoff from the watershed using Soil Conservation Service - Curve Number
(SCS-CN) method. The runoff estimated from the SCS-CN model was then used to know the variation of runoff potential with different
land use/land cover and with different soil conditions.
Keywords: Watershed, Nallur watershed, Surface runoff, Rainfall-Runoff, SCS-CN, Remote Sensing, GIS.
Estimation of morphometric parameters and runoff using rs & gis techniqueseSAT Journals
Abstract
Land and water are the two vital natural resources, the optimal management of these resources with minimum adverse environmental
impact are essential not only for sustainable development but also for human survival. Satellite remote sensing with geographic
information system has a pragmatic approach to map and generate spatial input layers of predicting response behavior and yield of
watershed. Hence, in the present study an attempt has been made to understand the hydrological process of the catchment at the
watershed level by drawing the inferences from moprhometric analysis and runoff. The study area chosen for the present study is
Yagachi catchment situated in Chickamaglur and Hassan district lies geographically at a longitude 75⁰52’08.77”E and
13⁰10’50.77”N latitude. It covers an area of 559.493 Sq.km. Morphometric analysis is carried out to estimate morphometric
parameters at Micro-watershed to understand the hydrological response of the catchment at the Micro-watershed level. Daily runoff
is estimated using USDA SCS curve number model for a period of 10 years from 2001 to 2010. The rainfall runoff relationship of the
study shows there is a positive correlation.
Keywords: morphometric analysis, runoff, remote sensing and GIS, SCS - method
-
Effect of variation of plastic hinge length on the results of non linear anal...eSAT Journals
Abstract The nonlinear Static procedure also well known as pushover analysis is method where in monotonically increasing loads are applied to the structure till the structure is unable to resist any further load. It is a popular tool for seismic performance evaluation of existing and new structures. In literature lot of research has been carried out on conventional pushover analysis and after knowing deficiency efforts have been made to improve it. But actual test results to verify the analytically obtained pushover results are rarely available. It has been found that some amount of variation is always expected to exist in seismic demand prediction of pushover analysis. Initial study is carried out by considering user defined hinge properties and default hinge length. Attempt is being made to assess the variation of pushover analysis results by considering user defined hinge properties and various hinge length formulations available in literature and results compared with experimentally obtained results based on test carried out on a G+2 storied RCC framed structure. For the present study two geometric models viz bare frame and rigid frame model is considered and it is found that the results of pushover analysis are very sensitive to geometric model and hinge length adopted. Keywords: Pushover analysis, Base shear, Displacement, hinge length, moment curvature analysis
Effect of use of recycled materials on indirect tensile strength of asphalt c...eSAT Journals
Abstract
Depletion of natural resources and aggregate quarries for the road construction is a serious problem to procure materials. Hence
recycling or reuse of material is beneficial. On emphasizing development in sustainable construction in the present era, recycling of
asphalt pavements is one of the effective and proven rehabilitation processes. For the laboratory investigations reclaimed asphalt
pavement (RAP) from NH-4 and crumb rubber modified binder (CRMB-55) was used. Foundry waste was used as a replacement to
conventional filler. Laboratory tests were conducted on asphalt concrete mixes with 30, 40, 50, and 60 percent replacement with RAP.
These test results were compared with conventional mixes and asphalt concrete mixes with complete binder extracted RAP
aggregates. Mix design was carried out by Marshall Method. The Marshall Tests indicated highest stability values for asphalt
concrete (AC) mixes with 60% RAP. The optimum binder content (OBC) decreased with increased in RAP in AC mixes. The Indirect
Tensile Strength (ITS) for AC mixes with RAP also was found to be higher when compared to conventional AC mixes at 300C.
Keywords: Reclaimed asphalt pavement, Foundry waste, Recycling, Marshall Stability, Indirect tensile strength.
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Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
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About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
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Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
A robust dlqg controller for damping of sub synchronous oscillations in a series compensated power system
1. IJRET: International Journal of Research in Engineering and Technology ISSN: 2319-1163
__________________________________________________________________________________________
Volume: 02 Issue: 04 | Apr-2013, Available @ http://www.ijret.org 724
A ROBUST DLQG CONTROLLER FOR DAMPING OF SUB -
SYNCHRONOUS OSCILLATIONS IN A SERIES COMPENSATED
POWER SYSTEM
K.C. Sindhu Thampatty1
, P. C. Reghu Raj2
1
Associate Professor, Dept. of Electrical and Electronics Engg, Amrita Viswa Vidyapeetham, Coimbatore,
Tamilnadu,
2
Prof & Head, Department of Computer Science and Engineering, Govt. Engineering College,
Sreekrishnapuram, Palakkad, Kerala, kc_sindhu@yahoo.com pcreghu@gmail.com
Abstract
This paper investigates the use of Discrete Linear Quadratic Gaussian (DLQG) Compensator to damp sub synchronous oscillations in
a Thyrisor Controlled Series Capacitor (TCSC) compensated power system. The study is conducted on IEEE First Benchmark Model
(FBM) in which, TCSC is modelled as a discrete linear time-invariant modular unit in the synchronously rotating DQ reference
frame. This modular TCSC is then integrated with the Linear Time Invariant (LTI) model of the rest of the system. The design of
DLQG includes the design of a Kalman filter for full state estimation and a full state feedback for control. Since the order of the
controller is as large as the order of the system considered here(27 states), the practical implementation of the controller is difficult.
Hence by using Hankels norm approximation technique, the order of the controller is reduced from 27 to 15 without losing the
significant system dynamics. The eigen analysis of the system shows that the use of DLQG can damp torsional oscillations as well as
the swing mode oscillations simultaneously, which is practically difficult for a conventional sub-synchronous damping controller. The
performance of the system with DLQG is appreciable for all operating conditions and it shows the robustness of the controller.
Index Terms: Sub-Synchronous Resonance (SSR), Torsional Oscillations, Thyristor Controlled Series Capacitor (TCSC), Discrete
Linear Quadratic Gaussian(DLQG)Compensator, Model Order Reduction (MOR).
-----------------------------------------------------------------------***-----------------------------------------------------------------------
1. INTRODUCTION
Series capacitors have been used extensively as an economical
means to increase load carrying capability, control load sharing
among parallel lines and enhance transient stability. However,
capacitors in series with transmission lines may cause sub-
synchronous resonance that can lead to turbine- generator shaft
failure and electrical instability at oscillation frequencies lower
than the normal system frequency [1]- [3].
Sub-synchronous resonance (SSR) has gained its name from
the fact that the frequencies of interest happened to lie in a
region below the synchronous frequency of the network. The
phenomenon of SSR was brought to general attention in
connection with the two damages that occurred to the turbine -
generator shafts at the Mohave Generating station in southern
Nevada in the United States of America in December of 1970
and October of 1971. These two failures were analyzed and
found that the failures occurred in the shaft section between the
generator and the exciter of the main generator collector was
due to torsional fatigue [4]- [6].
Torsional problems are most frequently encountered in rotor
systems with long shafts and large inertias constituting a
weakly damped mechanical system. The normal
subsynchronous frequency range is between 10 to 50 Hz where
as the swing mode oscillations are between 0.7 Hz to 2 Hz.
Therefore the simultaneous dampings of these oscillations are
difficult with a conventional controller. Numerous papers are
published on different approaches in sub-synchronous analysis
and also the use of Flexible AC Transmission System
(FACTS) devices to damp electromechanical oscillations [7].
Many methods [8]- [10] are proposed using series and shunt
FACTS devices to improve the power system dynamic
stability. To do the stability analysis, a perfect modelling of the
power system is required. Various efforts have been made in
the past few years to obtain a linearised state space models of
TCSC [11], [12]. A modular model of TCSC is derived by
Othman and Angquist [13], in which the TCSC model is
derived independently and then interfaced with the rest of the
system.
Kabiri et al. [14] developed a discrete model with higher
sampling rate (six samples per cycle), which is a sample-
variant model. In this work, the IEEE First Benchmark model
with the series compensation partly done by TCSC and partly
by fixed capacitor is considered. A discrete linear time
invariant state space model of TCSC is presented based on
Poincare mapping technique [15]. The model is based on six
2. IJRET: International Journal of Research in Engineering and Technology ISSN: 2319-1163
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Volume: 02 Issue: 04 | Apr-2013, Available @ http://www.ijret.org 725
samples per cycle. The sample invariance of the model is
achieved by a transformation of the zero sequence variables of
different voltages and currents. The developed model is then
integrated with the rest of the system.
In pole placement technique, all states must be controllable and
measurable, otherwise the controller input generated by the
controller doesnot affect all the state variables of the system. In
multi input, multi output (MIMO) systems, pole placement is
extremely difficult. Yu et.al, pole assignment method is
employed to control all the SSR modes, by using state
feedback [16]. But it was found that the approach is difficult to
implement since most of the state variables were not
measurable. The major drawback of pole placement method is
that, if the design parameters or controller gain elements are
not having enough parameters, the best possible pole allocation
is not possible. Moreover the control is based on measured
state variables, some state variables measurement are so noisy
which can result in unsuccessful pole placement. In output
feedback control scheme, some signals required for the control
were difficult to measure The system we considered in this
study is a multi output system having 27 states. These states
are not fully controllable and observable and hence the pole
placement method is not possible. Discrete time designs are
important because most controllers are implemented using
digital controllers. With most of the conventional controllers
simultaneous damping of swing mode and torsional mode
frequencies are difficult. The system we considered in this
study is a discrete model of IEEE FBM which has five
torsional modes. Hence our keen interest was to design a
discrete controller for our discrete system. The discrete LQG
approach is based on the optimal estimation and optimal
control of the discrete states. The DLQG technique nearly
eliminates all the trial and error method of a conventional pole
placement design. This discrete design can handle low
sampling rate(6 samples per cycle) associated with the system.
Hence our interest in this work is to design a controller to
damp all these frequencies simultaneously. A Discrete Linear
Quadratic Gaussian (DLQG) compensator is such an optimal
controller with the objective of reducing a quadratic cost
function of the system states and control signal. In the design
of DLQG, the process noise and measurement noises are
considered as white Gaussian noise signals with zero mean
value. Since all the system states in this model are not
observable, a Kalman filter is designed to estimate all the
system states. By using these estimated states an optimal
regulator is designed to control the TCSC [17] - [20].
Since the order of the DLQG controller is as large as the order
of the system, practical implementation is difficult. Hence by
using standard model order reduction techniques [21], [22], the
order of the controller is reduced. Four different techniques are
tried in this work to reduce the order of the controller namely,
balanced realisation technique, optimal Hankel norm
approximation technique, truncated balanced realisation and
truncated residualisation technique [23]. By comparing the
performance of these four methods, it has been observed that
the Hankel norm approximation method of reduction gives
better result. Hence in this study, the original system of 27
states is reduced to 15 states by Hankel norm approximation
method and it is found that the reduced model retains the
important characteristics of the original system and
approximates its response as closely as possible with the
original system for the same inputs. The paper is organised as
follows. Section II briefly explains the sub-synchronous
phenomenon. Section III explains the mathematical modelling
of the TCSC and section IV explains the interconnection of this
modular discrete TCSC with the rest of the power system in
IEEE FBM. Section V explains the DLQG design and the
model order reduction of the controller. Section VI explains the
simulation results followed by the conclusion in section VII.
2. SUB-SYNCHRONOUS RESONANCE
PHENOMENON
Sub-Synchronous Resonance (SSR) is a dynamic phenomenon
in power system. The IEEE definition for SSR is ” It is an
electric power system condition where the electric network
exchanges energy with a turbine generator at one or more of
the natural frequencies of the combined system below the
synchronous frequency” [3]. In a series compensated network
shown in Fig.1, currents at resonance frequency fer will flow
for a small electrical disturbance, where fer is given by :
Where Xc is the effective series capacitive reactance and Xl is
the effective inductive reactance of the system
Fig.1. IEEE First Benchmark model for SSR studies
These currents appearing at the generator armature will
produce a rotating magnetic field at an angular electrical speed
of !er . The armature magnetic field rotating at sub-
synchronous speed interacts with the rotor normal dc magnetic
3. IJRET: International Journal of Research in Engineering and Technology ISSN: 2319-1163
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Volume: 02 Issue: 04 | Apr-2013, Available @ http://www.ijret.org 726
field rotating at synchronous speed and develops an
electromagnetic torque. The in phase component (in phase with
speed ) of this torque is responsible for the sustained
oscillations in the system. Torsional interaction occurs in the
system, when the subsynchronous torque frequency f0 - fer is
close to one of the torsional mode frequencies fn. If the
damping torque component of the sub-synchronous torque
equals or exceeds the inherent damping torque of the rotating
system, the corresponding torsional modes will be unstable. If
the generator torsional mode frequencies are different from the
subsynchronous frequency, then the torsional interaction taking
place in the system is very less. Since the rotor circuits are
faster, the rotor resistance viewed from the armature terminal is
negative. When this negative resistance exceeds the sum of the
armature and network resistances, the electrical system is
selfexcited [17], [18]. This effect is called Induction generator
(IG) effect. This self-excitation can produce excessive voltages
and currents.
When the electrical resonant frequency is near to the
complement of a torsional resonant frequency of the
turbinegenerator shaft system, the torsional interaction takes
place. Under this condition, a small voltage induced in the
armature by rotor oscillation can result in a large sub-
synchronous current. When the torque produced by this current
is larger than that resulting from the mechanical damping
torque of the system, the coupled electromechanical system
will experience growing oscillations, which is called the
Torsional Interaction (TI). Problem of TI is more severe than
that due to IG effect.
3. LINEAR TIME INVARIANT DISCRETE
MODEL OF TCSC
In this section a sample invariant discrete model of TCSC [15]
is presented. The main circuit of TCSC includes a capacitor,
inductor and antiparallel switching thyristors. The operation of
TCSC is periodic, where one of the thyristor conducts during a
portion of the half cycle. The duration and timing of the
conduction is based on triggering logic and is controlled by the
current synchronised signals generated by PLL. Certain
assumptions are made in the development of discrete model.
The assumptions are:
1) The thyristors are assumed to be ideal.
2) TCSC is operated in capacitive mode only and the
conduction angle of thyristors are limited to 60 electrical
degrees which is the common operating range of TCSC.
3) The six sampling instants in a cycle are fixed in time and are
chosen such that the conduction period of intervals are as
shown in Fig 2.
4) The line current in DQO reference frame varies
linearlyduring the sampling interval. i.e,
Fig.2. Timing diagram of thyristor triggering of TCSC
The thyristor turn on instant is ɸa and turn off instant is Ta in
phase a as shown in Fig.2. Similarly the turn on and turn off
instants in phase b and c can be written as ɸb, Tb and ɸc, Tc
respectively. The conversion used to transfer three phase abc
variables to DQO is given by:
The conduction period of the thyristor in any one phase is
shown in Fig.2. During the conduction interval of the thyristor,
the TCSC is modeled as a parallel LC circuit and the
corresponding differential equation in dq0 reference frame for
phase a can be written as Eqn.6 and 7:
4. IJRET: International Journal of Research in Engineering and Technology ISSN: 2319-1163
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Volume: 02 Issue: 04 | Apr-2013, Available @ http://www.ijret.org 727
When the thyristors are turned off, the inductor currents are
zero and hence TCSC is modeled as a simple series capacitor
circuit. Then the corresponding voltage equation for phase a
can be written as:
The state space representation of phase a can be represented as:
Where
Where P=[1 0] and ya = Va. Similar equations can be written
for phases b and c with 1200 and 2400 phase shift.
To derive TCSC model in state space form, the voltage
equations in phases a, b and c in (k + 1)th instant can be
represented as functions of phases voltages and phase currents
in kth instant and phase currents in (k+1)th instants as shown in
Eqn. 13.
are the change in thyristor turn on and turn
off instants respectively in b phase. From the derivation of F,
H, J and G matrices [15], it is found that the variation in
capacitor voltage in any phase is independent of the turn off
time of the respective thyristor. In this model formulation, we
have considered that the change in current during a sampling
interval is a function of time and it is linearly varying during
any sampling interval. This change in current can be written as:
5. IJRET: International Journal of Research in Engineering and Technology ISSN: 2319-1163
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Volume: 02 Issue: 04 | Apr-2013, Available @ http://www.ijret.org 728
The matrix equation of discrete LTI TCSC model in DQ0
reference frame after the transformation is given by:
Where
The time varying transformation matrix T is evaluated (5) at
instants t0 as T(t0)and t1 as T(t1) . Similar equations can be
written for other phases also. It is observed that the state space
equations are not sample invariant. i.e., for any sample, the
matrix at kth interval and (k + 2)thinterval are same. It is also
observed that the sign of all coupling terms between zero
sequence variables and DQ variables in the F, G matrices and
the last row of H matrix alternates at consecutive sampling
instants. In this discrete model of TCSC, to make the model
sample invariant, a transformation is applied to the zero
sequence variables as given in equation:
Where k indicates any sample. After the above transformation,
the sample invariant TCSC equations can be obtained as :
It is found that the sample invariant transformation is
consistent and the transformed zero sequence components
retain their coupling to D and Q components of currents and
voltages. When the developed TCSC model is interfaced with
the rest of the power system, the discredited zero sequence
variables of the system is also to be transformed (Eqn. 21 and
22) to obtain the time invariance.
4. MODEL OF THE REST OF THE SYSTEM
The rest of the system consists of turbine-generator system,
transmission line, PLL and TCSC controller. The schematic
diagram of the full system with TCSC is shown in Fig.3. TCSC
voltage VDQ0 is the input for the rest of the system.
Fig.3. Block diagram representation of a controller connected
to TCSC
A. Turbine -Generator model
The system considered here is the IEEE First Benchmark
model which has totally six masses including the generator and
exciter. Synchronous machine considered in this study is 2.2
models where the first digit refers to the number of windings in
the q-axis [IEEE (1986)]. In 2.2 model, three phase armature
windings (a, b and c) on the stator and four windings on the
rotor including the field winding ’f’ are placed . The amortisser
(or damper) circuits in the salient pole machine or the eddy
current effects in the rotor are represented by a set of coils with
constant parameters. Three damper windings, ’h’ in the d axis
and g, k in the q axis are placed. Following assumptions are
made in the derivation of the basic electrical equations of the
machine:
• The mmf in the air gap is distributed sinusoidally and the
harmonics are neglected.
• Saliency is restricted to the rotor. Effect of slots in the stator
is neglected.
• Magnetic saturation and hysteresis are ignored.
The mechanical system consisting of rotors of generator
exciter, turbines and shafts can be viewed as a mass –
springdamper system. Assumptions made in the modeling of
mechanical system are:
• The system masses are considered as lumped masses.
• Slip at the operating point is zero.
6. IJRET: International Journal of Research in Engineering and Technology ISSN: 2319-1163
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Volume: 02 Issue: 04 | Apr-2013, Available @ http://www.ijret.org 729
Assuming the fluxes linking with different rotor coils are free
of harmonics, the time invariant linearised model about an
equilibrium point can be written as :
B. Electrical network model
Electrical AC network consists of transformers, transmission
lines with fixed series compensation. Transformers are
modeled by representing its equivalent leakage reactance Xt
and the transmission lines are represented by its equivalent
impedance as shown in Fig. 1. The state space representation
of the electrical network is represented as:
C. Current synchronised PLL
A current synchronised PLL is designed for the setting of firing
scheme for TCSC. The set time for firing of the thyristor starts
from the previous zero crossing of the line current. The timing
signal generated by PLL in steady state ɵt is shown in Fig.4.
Fig.4. Operation of PLL
The state space equation of PLL can be expressed as :
D. The conventional TCSC controller model
The conventional TCSC controller controls the firing angle α
of the thyristor to meet the required objective. The
conventional controller consists of a gain block, a signal
washout block and a phase compensation block as shown in
Fig.5. The phase compensation block provides the appropriate
phase lead characteristics to compensate for the phase lag
between input and output signals. The signal washout block
serves as a high pass filter which allows signals associated with
oscillations in input signal to pass unchanged.
Fig. 5. Structure of a conventional controller
The general form of controller equation is given by:
7. IJRET: International Journal of Research in Engineering and Technology ISSN: 2319-1163
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Volume: 02 Issue: 04 | Apr-2013, Available @ http://www.ijret.org 730
E. The interfaced discrete-time model of the system
Combining the discretised equations of generator-turbine,
transmission network and the PLL with the discrete model of
TCSC, the overall system equation can be written as:
Where h is the sampling time. Eigen values of the system with
the conventional controller is shown in Table 1 in which, K
represent the gain of the conventional controller. As shown in
Table 1, increased gain can stabilize the swing mode, but
torsional mode 4 gets destabilised. Hence it is observed that,
the simultaneous damping of all modes using the conventional
controller is difficult. It may be desirable to have a separate
Power Swing Damping Controller (PSDC) and sub-
synchronous Damping Controller (SSDC). In the next section
the design of DLQG compensator is discussed for the above
system which gives simultaneous damping of torsional mode
as well as the swing mode oscillations. The conventional
PSDC along with SSDC for damping SSR as well as swing
mode oscillations can be replaced by a single robust DLQG,
which also guarantees the system stabilisation also.
5. ROBUST CONTROL DESIGN USING
DISCRETE LINEAR QUADRATIC GAUSSIAN
(DLQG) COMPENSATOR
DLQG design is an optimal control design which produces the
best possible control system for a given set of performance
objectives. Usually a quadratic cost function known as
performance index of the system states and control signal must
be minimised by feeding back the optimal states. In most of the
practical systems, all the system state variables are not
available for the measurement. Hence it is necessary to use an
optimal estimator for state estimation. In this work the design
of DLQG involves the design of Kalman filter as an optimal
estimator, and the estimated states are fed back to the system as
state feedback control law.
A. The design of state feedback controller
The discrete system to be controlled is represented in the state
space form as:
Where Q is a symmetric positive semi definite state weighting
matrix and R is a symmetric positive definite control weighting
matrix. The optimisation function represents the weighted sum
of energy of the states and control. The gain K of the optimal
controller is derived from the algebraic discrete time Riccati
equation given by:
Where P is the solution of the Riccati equation the optimal
control can be expressed as:
In stochastic systems, this control law guarantees to bring the
system states close to zero. This is an advantage of the linear
quadratic method that a stabilising controller is obtained where
as in classical controls, the stabilising controller is designed
separately.
B. The design of Kalman filter as an optimal
estimator
The Kalman filter is an optimal state estimator for linear
dynamical systems, which minimises the estimation error given
as:
And this linear minimum mean square problem can be solved
recursively. A noisy plant with the presence of modelling
uncertainties called process noise and measurement noise can
be modeled by passing white gaussian noise through an
appropriate linear system. Such a plant can be represented in
state space form as:
8. IJRET: International Journal of Research in Engineering and Technology ISSN: 2319-1163
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Volume: 02 Issue: 04 | Apr-2013, Available @ http://www.ijret.org 731
Where v(k) is the process noise vector produced due to
modeling errors and z(k) is the measurement noise vector.
These noises can be assumed as uncorrelated white Gaussian
zero mean stationary noises.
The optimal Kalman filter gain can be represented as:
Where R(k) is the optimal covariance matrix satisfying the
matrix Riccati equation. The dynamics of the controller can be
expressed as:
The system stability robustness depends on the weighting
matrices Q and R. By analysing the dominant parameters that
effect SSR like mechanical parameters, the weighting matrices
are properly tuned assuring system stability robustness. The
order of the DLQG compensator designed for a system is same
as the order of the system. Hence the implementation of such a
large controller is practically difficult and it is advisable to
reduce the controller order. The order reduction can be done in
two ways. Either the system order will be reduced and then the
controller is designed for the reduced system or the controller
is designed for large systems and then reduces the order of the
controller.
C. Model order reduction of DLQG
Standard methods are available for the model order reduction
of the large system like Pade’s approximation , model
approximation or continued fraction expansion etc. In this
study, model order reduction by four different methods are
tried namely, balanced realisation technique, optimal Hankel
norm approximation technique, truncated balanced realisation
and truncated residualisation technique. Figure 8 shows the
frequency response plotted by using different techniques.
By comparing the results obtained in different methods,
theresponse obtained by Hankel norm approximation technique
closely matches with the original system. Hence in this work,
the Hankel norm approximation technique is chosen for
orderreduction and the controller order is reduced from 27 to
11. This order reduction assures the desirable performance and
stability robustness of the controller. After reducing the order
of the controller, the reduced controller is connected to the
original system. In this work, the model order reduction is done
using μ control toolbox in MATLAB.
Fig.6. Comparison of different model order reduction
techniques
6. SIMULATION RESULTS
Simulation studies are conducted on the IEEE FBM for SSR
studies which is enhanced with TCSC. The system consists of
892.4 MVA synchronous generators connected to an infinite
bus through a series compensated 500kV transmission line.
Mechanical damping of the system is assumed to be zero in the
analysis in order to present the worst case damping conditions.
In order to reduce the complexity, all calculations are made in
p.u, taking 500kV as the base value. The simulation scenario is
as follows. The system is operating in its steady state condition
for a given operating condition. Then an impulse increase in
torque for 10% is injected to the shaft section connecting the
masses LPA and LPB and the simulations are carried out for
different operating conditions.
The torsional mode stability has been analyzed using the eigen
value technique. Results of this analysis with different firing
angles of the thyristor are consolidated in Table II through
Table V. It has been observed from Tables III and IV that the
unstable torsional mode 4 gets stabilised by DLQG and that the
damping of all other torsional modes are increased with
DLQG. Damping of all the torsional modes are drastically
improved with DLQG as shown in Table V for the firing angle
α = 1700
.
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The pole-zero mapping of the system with and without DLQG
for three different firing angles of TCSC are shown in Figures
7 through 12. From these figures, it has been observed that
most of the poles on the surface of the unit circle are pushed
towards the center of the circle with DLQG compensator. It
has been observed that, in the case of the system with and
without DLQG, zeros of the system is the same, but the
locations of the poles are quite different. It can be seen that the
system in open loop is unstable with poles outside the unit
circle, whereas this mode becomes very well damped with
DLQG. The stability of most of the torsional modes is
improved with DLQG.
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7. ROBUSTNESS EVALUATION
Extensive simulations have been carried out to assess the
robustness of the proposed DLQG compensator for TCSC in
different operating conditions. The real power is varied from
0.2 p.u to 1.2 p.u and the terminal voltage is varied between
0.5 p.u to 1p.u. As the stability of the torsional modes varies
with the mehanical parameters of the system like inertia and
spring constant as shown in Fig. 13 and Fig. 14, in order to
reflect the parameter uncertainties, the random errors with the
variation of 10% to 70% are added to these parameters of each
mechanical mass. Similarly the level of series compensation is
varied from 10% to 70% by changing the firing angle. In all
these cases, the DLQG is designed such that the maximum
overshoot in each state variable doesnot exceed more than 3%
and settling time must be less than 2 seconds after the
occurence of the disturbance. The system performance has
been analyzed using a reduced order controller also and it has
been observed that the performance of the system with the
reduced controller is matching with that of the full order
controller.
The results of the eigen analysis conducted on the system with
the conventional controller is shown in Table VI. As seen in
this table, when the gain of the conventional controller
increases, torsional mode 4 gets undamped even though the
damping of the other modes increases. The simultaneous
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damping of all the torsional modes using the conventional
controller is difficult. Hence, it is desirable to have a separate
Power Swing Damping Controller (PSDC) to damp swing
mode oscillation and a Subsynchronous Damping Controller
(SSDC) to damp SSR oscillations. The simultaneous damping
of torsional as well as the swing mode oscillations is possible
with the DLQG compensator and damping of all the torsional
modes are improved with DLQG compensator.
Optimal solution of the cost function and hence the
simultaneous damping of the swing mode and torsional modes
can be achieved by properly tuning the Q and R
matrices(weighing matrices of system states and the control
inputs) in the cost function.
A comparison of the stability of torsional modes, swing mode
and the network mode are made with a conventional controller,
DLQG compensator and without any controller as shown in
Table VII and Table VIII for different thyristor triggering
angles.
It has been observed that the damping of all modes is highly
improved with DLQG compensator compared to a
conventional controller. In order to prove the controller
robustness, the system performance with the proposed
controller is evaluated for various operating conditions. When
a small change in the torque is applied to the shaft section
between masses LPA and LPB, it produces changes in other
shaft sections. Figures 15 through 17 shows the deviation of
torque in different shaft section for real power P=1pu, terminal
voltage V=1pu and thyristor firing angle of 1650. The torque in
the shaft sections connecting the generator and the exciter is
very small compared to other shaft sections as shown in Fig. 16
and its maximum value is nearly 0.03 p.u. But the oscillations
persist for longer duration. The variation of torque in shaft
section connecting between masses HP and IP is having
minimum deviation. All these oscillations are having
maximum deviations only for few cycles and after that its
magnitude decreases drastically.
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The maximum deviation of torque is 0.22 p.u and it occurs in
the shaft section between masses LPA and LPB, as shown in
Fig. 17. Within 2 to 3 secs., this deviation reduces to zero. The
response of the system for other operating conditions is as
shown in Figures?? through??. Figure?? Through 20
corresponds to the operating conditions the real power
P=0.7pu, terminal voltage V=0.9pu, thyristor firing angle α=
1650 and inertia of the mass LPB is reduced to 70% of its
normal value. In the operating conditions real power P=.9pu,
V=1pu, the thyristor firing angle α = 1700 and if the inertia
constant of the mass LPB is increased by 30% of its normal
value, the performance of the system with the proposed
controller varies as shown in Figures 21 through 23. When the
real power P=0.8pu, voltage=0.8pu and the thyristor firing
angle α = 1700, the performance of the system varies as shown
in Fig 24 through 25
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Similarly, by changing the stiffness of the shaft, the
performance of the sysstem with the controller is evaluated for
different operating conditions as shown in Fig. 26 through Fig.
31. Figures 26 through 28 corresponds to the operating
condition of real power generation of 0.9 pu, terminal voltage
V=1pu and thyristor firing angle α = 1650. The stiffness of the
shaft section connection between masses IP and LPA is
reduced to 80% of its normal value.
Similarly, for the same operating conditions, when the stiffness
of the same shaft section is increased by 20%, the oscillations
prolong for more time at the same time, the controller provides
damping also as shown in Figs. 29 through 31. It has been
observed that the proposd controller give desirable damping of
the torsional as well as the swing mode oscillations for all
these operating conditions which proves its robustness.
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The responses of the system with the reduced DLQG
compensator are as shown in Fig. 32. Initially, the DLQG
compensator is designed for the system with 27 states, which
results in a compensator of order 27. Then, by using Hankel’s
norm approximation technique, the order of the controller is
reduced to 11 [?]. The performance of the system with reduced
order DLQG compensator is then compared with the
performance of the system obtained with the full order DLQG.
It has been observed that the performance of the reduced
controller is exactly matching with the full order compensator.
In short, the model order reduction techniques can be
effectively used to reduce the complexity of implementing the
DLQG compensator in large systems without affecting the
major system dynamics.
Figures 33 to 35 show the variation of system response with
and without the DLQG controller. From these figures, it can be
observed that the damping of the torsional modes is improved
with the use of DLQG controller.
From these observations, it can be concluded that an effective
control of TCSC is possible with DLQG controller. Figures 11,
14 and 15 show the variation of slips in different masses of the
mechanical system. Figure 12 and 13 shows the variation of
torque in different shaft section. The maximum torque
deviation occurs in the shaft section between masses LPA and
LPB as shown in Fig.12, but it exists only for a small duration.
The simulation results verifies the eigen analysis result. As
given in Table 2, even after the major disturbance, the torsional
mode 4 is well damped as shown in simulation graphs.
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CONCLUSIONS
In this paper, the use of a discrete model of TCSC interfaced
with the rest of the system in IEEE FBM for SSR analysis and
the DLQG compensator design for damping SSR oscillations
has been discussed. The design of DLQG involves the design
of Kalman estimator for state estimation and state feedback for
control law. By conducting eigen analysis on the study system.
it is observed that unlike in a conventional controller, the
simultaneous damping of swing mode as well as the torsional
oscillations are possible with DLQG. Performance of the
proposed controller is tested for various operating conditions
and proved the robustness of the controller.
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