Thyristor Controlled Series Capacitor Research Articles

Flower Pollination Algorithm Based Optimal Setting of TCSC to Minimize the Transmission Line Losses in the Power System

To avoid the problems of voltage stability, losses and security of power system is needed to monitor frequently and these problems are controlled by using the Flexible AC Transmission System (FACTS) devices. They help to improve the voltage profiles, security of the system and minimize the transmission line losses. Thyristor Controlled Series Capacitor (TCSC) is one of the FACTS devices which is easier to control than other control devices. The device was placed such that it also meets the constraint of having minimum losses. Further for setting of the TCSC Flower Pollination Algorithm is employed, it is a nature inspired algorithm developed from the pollination of flowers. For Placement of TCSC, a Fast Voltage Stability Index (FVSI) is proposed. For the verification of the proposed method, simulations are carried on IEEE 14 bus system and the results are presented and analyzed to ascertain the effectiveness in reduction of the losses in the power system.

Optimal Placement of FACTS Devices to Improve Power Flow Using Bees Algorithm

Flexible AC Transmission System (FACTS) device has gained popularity recently as an essential device in power systems. The introduction of FACTS technology in power systems has seen increased flexibility and control of power flow along the transmission lines. This paper focuses on three FACTS devices namely Static VAR Compensator (SVC), Thyristor Controlled Series Capacitor (TCSC) and Unified Power Flow Controller (UPFC). The devices will be optimally placed to simultaneously minimize system real power loss and maximize the inter-tie flow using Bee Algorithm (BA). BA is a simple and efficient heuristic search method based on the foraging behavior of honey bees searching for the best food source in a recently proposed multi objective optimization algorithm. The performance of presented BA algorithm is tested and verified on the IEEE 30-bus power systems. A Genetic Algorithm (GA) configured for the same purpose is used for evaluation. Results show the difference of performance of the devices used in this situation. The results achieved in this work illustrated that BA can successfully be used to solve the nonlinear problems related to power system optimization. Keywords— Bee algorithm, Static VAR compensator, Thyristor Controlled series compensator,

The Effective Enhancement of Power System Security by Flexible Transmission Line Impedance with Minimal Rescheduling of Generators

After the digital revolution, the power system security becomes an important issue and it urges the power producers to maintain a well secured system in order to supply a quality power to the end users. This paper presents an integrated Corrective Security Constrained Optimal Power Flow (CSCOPF) with Flexible Transmission Line Impedance (FTLI) to enhance the power system security. The corrective approach of SCOPF is chosen, because it allows the corrective equipment to bring back the system to a stable operating point and hence, it offers high flexibility and better economics. The concept of FTLI arises from the ability of FACTS devices such as Thyristor Controlled Series Capacitor (TCSC), which can vary the line reactance to a certain extent. An enhanced security can be achieved by incorporating FTLI into the CSCOPF problem, since the power flow in a system is highly dependent on the line reactance. FTLI based CSCOPF can reduce the amount of rescheduling of generators, but it will result in an increased number of variables and thus, the complexity to the optimization process is increased. This highly complex problem is solved by using nonlinear programming. The AC based OPF model is preferred, since the corrective security actions require highly accurate solutions. IEEE 30 bus system is used to test the proposed scheme and the results are compared with the traditional CSCOPF. It can be seen that the proposed idea provides a notable improvement in the reduction of cost incurred for restoring the system security.

Solution of optimal power flow with FACTS devices using a novel oppositional krill herd algorithm

Abstract Krill herd algorithm (KHA) is a novel meta-heuristic approach that is influenced from the herding behaviour of the krill swarms searching for food or communication with each other. The proposed opposition based KHA (OKHA) is intended here, for solving the optimal power flow (OPF) problem of power system, incorporating flexible AC transmission systems (FACTS) devices, namely, thyristor controlled series capacitor and thyristor controlled phase shifter. In the proposed OKHA, the concept of opposition based population initialization and opposition based generation jumping are employed in the basic KHA to enhance its computational speed and convergence profile. The potential of the proposed OKHA is assessed, successfully, on modified IEEE-30 bus and IEEE-57 bus test power systems. The four different objective functions are formulated here that reflects the minimization of fuel cost, active power transmission loss, emission and combined economic and environmental cost, separately. Simulation results, presented in this paper, indicate that the proposed approach yields superior solution over the other popular methods surfaced in the recent state-of-the-art literature including basic KHA and also show its effectiveness for the solution of OPF problem of power system equipped with FACTS devices.

Performance comparison of TCSC with TCPS and SSSC controllers in AGC of realistic interconnected multi-source power system

Abstract The primary goals of employing series flexible ac transmission system (FACTS) in automatic generation control (AGC) studies of interconnected power systems are mitigating area frequency and tie-line power oscillations. This paper compares dynamic performance of thyristor controlled series capacitor (TCSC) as damping controller with thyristor controlled phase shifter (TCPS) and static synchronous series compensator (SSSC) which are series FACTS damping controllers. Commonly used lead-lag controllers are used in structure of damping controllers. The effect of TCSC in tie-line power exchange is modeled mathematically based on the Taylor series expansion for small-signal load disturbance. The performance of the proposed TCSC controller in coordination with integral AGC is compared with cases of TCPS–AGC and SSSC–AGC. An improved particle swarm optimization (IPSO) algorithm and integral of time multiplied squared error (ITSE) performance index are used to design the damping controllers. A two-area power system having generations from reheat thermal, hydro, and gas units in each area is evaluated regarding nonlinearity effects of generation rate constraint (GRC) and governor dead band (GDB). The simulations results in MATLAB/SIMULINK environment show that the proposed TCSC–AGC yields superior performance than others in damping of area frequencies and tie-line oscillations. Furthermore, sensitivity analyses are performed to show greater robustness of TCSC–AGC.

Voltage Stability Improvement By Using FACTS Elements With Economic Consideration

In last two decades due to increasing power demand power systems are operated to their maximum operation conditions. It will cause to any problems that one of these is voltage instability. To overcome this problem Flexible AC Transmission Systems(FACTS) have been used in power systems. The FACTS devices improves system stability, reduce losses and power generation cost. Best location of FACTS devices will help to maintain bus voltages at desired level, reduce cost of these devices and improve voltage stability margins. This paper presents the methods to location and rating of FACTS devices are optimized with using weighted coefficients method and Sterength Paretto Evolutionary Algorithm(SPEA).Thyristor controlled series capacitor(TCSC)and Static Var Compensator(SVC)are also considered in this paper.

Fuzzy harmony search algorithm based optimal power flow for power system security enhancement

Abstract This paper proposes the integration of fuzzy logic system with harmony search algorithm (FHSA) to find the optimal solution for optimal power flow (OPF) problem in a power system. The objective of the method is to minimize the total fuel cost of thermal generating units having quadratic cost characteristics and severity index (SI). The generator active power, generator bus voltage magnitude, transformer taps, VAR of shunts and the reactance of thyristor controlled series capacitor (TCSC) are taken as the control variables. The adjustment of proposed algorithm parameters such as pitch adjustment rate (PAR) and bandwidth (BW) is done through fuzzy logic system (FLS). The effectiveness of the proposed method has been tested on the standard IEEE 30 bus, IEEE 57 bus and IEEE 118 bus systems in MATLAB environment and their results are compared with conventional harmony search algorithm (HSA) and other heuristic methods reported in the literature recently.

Coordinated design of power system stabilizers and TCSC employing improved harmony search algorithm

Power System Stabilizers (PSS) are generally employed to damp electromechanical oscillations by providing auxiliary stabilizing signals to the excitation system of the generators. But it has been found that these Conventional PSS (CPSS) do not provide sufficient damping for inter-area oscillations in multi-machine power systems. Thyristor Controlled Series Capacitor (TCSC) has immense potential in damping of inter-area power swings and in mitigating the sub-synchronous resonance. In this paper Improved Harmony Search Algorithm (IHSA) has been proposed for coordinated design of multiple PSS and TCSC in order to effectively damp the oscillations. The results obtained by using IHSA on WSCC 3-machine, 9-bus system are found to be superior compared to the results obtained using Bacterial Swarm Optimization (BSO) algorithm. The damping performance of conventional PSS and TCSC controllers is also compared with coordinated design of IHSA based PSS and TCSC on New England 10-machine, 39-bus system over wide range of operating conditions and contingencies. To demonstrate the effectiveness of the proposed technique the results obtained on this test system are also compared with the results obtained with Genetic Algorithm (GA), Particle Swarm Optimization (PSO), Harmony Search Algorithm (HSA) and Bacterial Swarm Optimization (BSO).

English

In recent years, a number of Flexible AC Transmission system (FACTS) devices have been proposed for better utilization and enhancing the power transfer capability of existing power transmission network. There are several conventional methods to improve the voltage profile and annual savings, but FACTS devices are shown better results to improve transmission line performance such as power profile and annual savings. The ability to enhance power transfers lead to their applications in a multi machine power system for the purpose of an overall reduction in power generation cost, compared to others. This paper focus on the evolution of economic viability for reducing generation cost using FACTS devices. The most and versatile FACTS devices, such as Static Var Compensator (SVC), Thyristor Controlled Series Capacitor (TCSC) and Unified Power Flow Controller (UPFC) are used to improve transmission capacity of the system. The devices are incorporated in the system by the Optimal Power Flow method and Genetic Algorithm based optimization technique. The proposed methods are tested on IEEE-57 bus system and the corresponding test results are compared with conventional method.

A Modified Cuckoo Search Algorithm for Improving Voltage Profile and to Diminish Power Losses by Locating Multi-type FACTS Devices

This paper proposes a cuckoo search (CS) algorithm, a stochastic heuristic algorithm, combined with the most familiar genetic algorithm (GA) to seek optimal location(s) of FACTS devices in a multi-machine power system. The intention of hybridizing GA with CS algorithm is to improve the quality of solution through expanding the search space and speed of convergence. The run time and the required function evaluation number(generations) for acquiring optimum by the modified algorithm are generally smaller than the basic algorithm. Identification of the best location for FACTS is a vital task as they are expensive to use. Here, three emerging and dissimilar kinds of FACTS devices, namely Unified Power Flow Controller, Thyristor Controlled Series Capacitor and Interline Power Flow Controller, are chosen for optimum locations and are modeled for steady-state studies. The optimal location and size of these FACTS devices, including installation costs, are computed utilizing the real power losses of the system as the objective function to be minimized. The feasibility of the proposed method is demonstrated for IEEE 30 bus power system network using MATLAB working platform. The results show that the proposed approach, with good stability, has better convergence and the simultaneous use of several kinds of FACTS controllers is the most efficient solution to improve the voltage profile with minimum power loss of the system.

Improved fault location algorithm for multi‐location faults, transforming faults and shunt faults in thyristor controlled series capacitor compensated transmission line

Fault location estimation in series compensated transmission lines is quite difficult because a non-linear current dependent circuit appears between the substation and fault point. In particular, the faults which occur at different locations at the same time in different phases known as multi-location faults has not been addressed by researchers. Other types of fault that may occur in transmission lines are transforming faults where one type of fault transforms to another type fault after some time. In this study, a fault location estimation scheme using artificial neural network (ANN) is presented for multi-location faults, transforming faults as well as for commonly occurring shunt faults in thyristor controlled series capacitor (TCSC) compensated transmission line. DB-4 wavelet is used for pre-processing of the three-phase current and voltage signals. The shunt capacitance of the line is considered based on distributed parameter line model. Feasibility of the ANN-based fault location algorithm is tested under a wide variation of parameters, such as fault type, location, fault resistance and fault inception angle. Fault location errors are within 0.001–1% range.

Comparison of Series and Shunt FACTS Controllers for Voltage Stability in Wind Power Network

Voltage instability has been given much attention by power system researchers and planners in recent years. One of the main reasons for voltage instability is reactive power imbalance in the power system. This paper proposes the use of wind power network for rectifying the problem of voltage instability. The aim of this paper is to identify the optimal location of FACTS controllers in an interconnected power network under N-1 contingency. Here, to improve the Voltage Magnitude Profile and Loadability limit Thyristor Controlled Series Capacitor and Static Synchronous Compensator are used. Cat Swarm Optimization is used to determine the optimal location and size of the FACTS controllers. In this paper IEEE 14-bus system is used for testing the proposed algorithm. Simulations are performed in MATLAB using Power System Analysis Toolbox.

Applications of FACTS devices for improving power system transient stability

As the power demand has been increasing rapidly, today’s modern power system becomes to be more complex and faces many challenges. It is envisaged that transient stability will play the important role in ensuring the steady state operation of power systems in the event of three phases fault or switching of lines. This paper investigates models of Flexible AC Transmission Systems (FACTS) and applications of FACTS devices for improving the rotor angle stability. FACTS devices are applicable in shunt connection Static Var Compensator (SVC), in series connection Thyristor-Controlled Series Capacitor (TCSC), or in the combination of both. Mathematical models of power systems having FACTS devices are set of Differential - Algebraic Equations (DAEs). Trapezoidal rule and Newton - Raphson method are applied to solve DAEs. The simulation results of rotor angles demonstrate the effectiveness and robustness of proposed the SVC and TCSC on transient stability enhancement of power systems.

Perturbation estimation based coordinated adaptive passive control for multimachine power systems

This paper proposes a perturbation estimation based coordinated adaptive passive control (PECAPC) of generators excitation system and thyristor-controlled series capacitor (TCSC) devices for complex, uncertain and interconnected multimachine power systems. Discussion begins with the PECAPC design, in which the combinatorial effect of system uncertainties, unmodelled dynamics and external disturbances is aggregated into a perturbation term, and estimated online by a perturbation observer (PO). PECAPC aims to achieve a coordinated adaptive control between the excitation controller (EC) and TCSC controller based on the nonlinearly functional estimate of the perturbation. In this control scheme an explicit control Lyapunov function (CLF) and the strict assumption of linearly parametric uncertainties made on system structures can be avoided. A decentralized stabilizing EC for each generator is firstly designed. Then a coordinated TCSC controller is developed to passivize the whole system, which improves system damping through reshaping the distributed energies in power systems. Case studies are carried out on a single machine infinite bus (SMIB) and a three-machine system, respectively. Simulation results show that the PECAPC-based EC and TCSC controller can coordinate each other to improve the power system stability, finally a hardware-in-the-loop (HIL) test is carried out to verify its implementation feasibility.

A novel symbiotic organisms search algorithm for optimal power flow of power system with FACTS devices

In this paper, symbiotic organisms search (SOS) algorithm is proposed for the solution of optimal power flow (OPF) problem of power system equipped with flexible ac transmission systems (FACTS) devices. Inspired by interaction between organisms in ecosystem, SOS algorithm is a recent population based algorithm which does not require any algorithm specific control parameters unlike other algorithms. The performance of the proposed SOS algorithm is tested on the modified IEEE-30 bus and IEEE-57 bus test systems incorporating two types of FACTS devices, namely, thyristor controlled series capacitor and thyristor controlled phase shifter at fixed locations. The OPF problem of the present work is formulated with four different objective functions viz. (a) fuel cost minimization, (b) transmission active power loss minimization, (c) emission reduction and (d) minimization of combined economic and environmental cost. The simulation results exhibit the potential of the proposed SOS algorithm and demonstrate its effectiveness for solving the OPF problem of power system incorporating FACTS devices over the other evolutionary optimization techniques that surfaced in the recent state-of-the-art literature.

Power System Stability Improvement in Presence of Renewable Energies and TCSC

ABSTRACTReduction in fossil fuels and environmental aspect of them has led to the increasing need to the renewable energies such as wind power systems and other distributed generators (DGs) all over the world. With growing usage of wind energy in power systems, impact of wind generators on power system stability becomes more important than before. Since flexible alternating current transmission system (FACTS) devices have significant influence on system performance, especially series one to increase the stability of the system, in this work, thyristor-controlled series capacitor (TCSC) has been used. In this paper, also wind and other DGs as a hybrid energy production system are used and stabilization of power system using TCSC is investigated. Finally, it has been shown that, in addition to TCSC, other DGs are also used in maintaining the quality of supply, power system security and stability.

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English

Study on protection scheme using SFCL for transmission system with Thyristor Controlled Series Capacitor

In this paper, we propose a protection scheme using a superconducting fault current limiter (SFCL) for the power transmission system with Thyristor Controlled Series Capacitor (TCSC). TCSC can lead effectiveness such as power flow control, increase in transmission capacity, and improvement for system transient phenomena. But, because this has same effect to the reducing series impedances in transmission system, there are serious problem such as increase in fault current, transient stability deterioration and series voltage stress of TCSC in the transmission line. The proposed protection scheme using the SFCL into TCSC configuration can mitigate these problems. In addition, SFCL can be expected to protect the TCSC from a large transient current generated by lightning or switching surge in power transmission system. To verify the effect of the proposed protection scheme, PSCAD/EMTDC is used. From simulation result, we had good results for fault current limitation and insulating protection of TCSC.

A Novel Method for Seeking Optimal Placement of TCSC to Damp Oscillations in Power Systems

Thyristor controlled series capacitors (TCSC) damping controller is considered as a useful device to improve the stability of transmission power systems. Seeking the optimal placement of TCSC controller has become a critical issue for the power system stability. From the working point of view, the TCSC controller is used to improve the voltage magnitude, reactive power and oscillation damping of power systems. The effectiveness of the location of TCSC controller, particularly in the damping of power oscillations depends on its location and input signals in the power system during time of grid fault. In this paper, an energetic method based on controllability and observability Gramians in continuous-time is proposed to determine the optimal location of TCSC. The effectiveness of the proposed method has been verified on the 39-bus New England power system.

English

For the efficient transmission of power from power plants to consumer loads, the power losses are reduced in modern power system. In order to reduce such losses, a recently evolved FACTS technology is used. In this paper, Thyristor Controlled Series Capacitor (TCSC) is selected to enhance the loadability in the transmission line. To improve the maximum power transfer capability by this device an improved gravitational search algorithm (IGSA) is suggested. Velocity of each agent is improved by this proposed algorithm. If the velocity is high then agents move to a better solution or else the optimum solution might not be achieved. Through the mass determination of each agent, all the solutions are contributing to the optimum solution. Here the maximum power loss of the system is considered as a fitness function. The proposed algorithm is validated on IEEE-57 test system using MATLAB platform. Thus with the help of IGSA the maximum power transfer capability is achieved and that with the economic cost of the device.