Shunt FACTS Devices Research Articles

AC-DC Optimal Power Flow Incorporating Shunt FACTS Devices Using HVDC Model and Particle Swarm Optimization Method

This paper presents an efficient and reliable evolutionary-based approach to solve the AC-DC optimal power flow (OPF) incorporating shunt FACTS devices in electrical power networks. Our main goal is to minimize the objective function necessary for a best balance between the energy production and its consumption which is presented in a nonlinear function, taking into account the constraints of equality and of inequality. The objective is to minimize the total cost of the generations and also the active power losses with incorporating shunt FACTS devices such as the static VAr compensator (SVC). Furthermore, we will consider in detail the study of the AC-DC OPF under the use of the HVDC-link and the SVC. This optimization is based, on the application of the particle swarm optimization (PSO) method. Incorporation of the PSO method as a derivative-free optimization technique in solving AC-DC OPF problem relieves, significantly, the assumptions imposed on the optimized objective functions. The PSO method has been examined and tested on the standard IEEE 14-bus test system with different objectives that reflect active power losses minimization and active power generation cost minimization. The PSO results have been compared to those that reported in the literature recently. The results are promising and show the effectiveness and robustness of PSO method.

SWING, VOLTAGE STABILITY AND POWER TRANSFER CAPABILITY IN TRANSMISSION SYSTEM WITH UPFC: THE ART OF STATUS

In modern era, the increasing size of the power sys tem, to maximize the use of existing systems and to provide adequate voltage support is an emphasis on finding solutions. This f lexibility is needed electricity. Better placed than the Flexible AC Transmission Systems (FACTS) to control the flow of electricity, and to provide voltage support can be effective in turn resulting in less damage. The impact of these tools on line flow and bus volt age profile at random algorithm to determine the op timal number of ratings have been studied by keeping them better . The FACTS devices are expensive cause of that FACTS type, number and location of the FACTS devices is very important, for decide the optimal location and parameters of FACTS device s. FACTS are used in the following purposes: Transm ission pricing issues by maximizing social welfare with or without considera tion of FACTS’ costs; Better utilization of FACT by maximizing FACTS devices total transferred power; Reactive power or voltage control by minimizing transmission losses, or volta ge fluctuation. Increase system’s security under emergency by minimizing tra nsmission lines loadability. Power flow control, a current long transmission lin e, plays an important role within the energy system . The letter swings, longdistance transmission line voltage and power flow c ontrol in unified power flow controller (UPFC) base d compensation associated series or shunt FACTS devices are employed. Device s such as the proposed transmission line, between tof the sending and receiving end to the transmission line is used in p laces as different. Here also deals with determini ng the optimum placement of Flexible AC Transmission Systems (FACTS) damping ou t swings, voltage and improves power transfer devic es for a long transmission line. Here the concept of compensation mid-point o f facts is presented for optimal placement.

Optimal Location of Shunt Facts Devices For Power Flow Control

Power flow control, in an existing long transmission line, plays a vital role in Power System area. This paper employs the shunt connected compensation (STATCOM) based FACTS device for the control of voltage and the power flow in long distance transmission line. The proposed device is used in different locations such as sending end of the transmission line, middle and receiving end of the transmission line. The PWM control strategy is used to generate the firing pulses of the controller circuit. Simulations were carried out using MATLAB Simulink environment. The suitable location and the performance of the proposed model were examined. Based on a voltage-sourced converter, the STATCOM regulates system voltage by absorbing or generating reactive power. Contrary to a thyristor-based Static Var Compensator (SVC), STATCOM output current (inductive or capacitive) can be controlled independent of the AC system voltage. The simulation results reveals that the reactive power generated is better at the middle of the transmission line when compared with the other ends of the transmission line and also the voltage is controlled at the middle of the line. Henceforth the location of STATCOM is optimum when connected at the middle of the line.

OPTIMALLY LOCATED SVC FOR TRANSMISSION OF RENEWABLE ENERGY IN LARGE POWER SYSTEM

Shunt FACTS devices provide the possibility to control voltages and therefore to improve the security of the system. In order to use this possibility, the optimal location and the set values of the FACTS controllers have to be selected correctly. The singular analysis of the power system Jacobian matrix are applied to identify the optimal location of shunt FACTS devices in large power systems. Furthermore the application of Optimal Power Flow control is a possible method for choosing set values. In this paper a sensitivity index for the detection of sensor nodes is defined. Sensitivity analysis is used to determine the area on which the FACTS device has significant influence. And then only this limited area is included in the Optimal Power Flow control, because it is very difficult to include the entire system into the optimization process. Matlab code is written to find the optimal location of Shunt Facts device i.e., SVC. Furthermore the objective function of Optimal Power Flow control is analyzed. This function consists of three components. A certain type of FACTS is not able to influence all these components.

THE COMPENSATATION OF UNBALANCED 3-PHASE CURRENTS IN TRANSMISSION SYSTEMS ON UTILIZE DISTRIBUTED POWER FLOW CONTROLLER

It is self-possessed of the Distributed Power Flow Controller is a new device within the family of FACTS. Power Quality is becoming an important issue for both electric utilities and end users. So the paper concentrate on one of the issue of power quality that is voltage sag compensation. My paper deals with the operation principle of a Practical Design and Implementation Procedure of Utilize Distributed Power Flow Controller (DPFC) to Compensate Unbalanced 3-phase Currents in Transmissions Systems. The series converters of the DPFC are single phase, the DPFC can compensate both active and reactive, zero and negative sequence unbalanced currents. To compensate the unbalance, two additional current controllers are supplemented to control the zero and negative sequence current respectively. FACTS devices can be employed to compensate the unbalanced currents and voltages in transmission systems. Unfortunately, it is found that the capability of most of FACTS devices to compensating unbalance is limited. Series and shunt FACTS device can only provide compensation of unbalanced reactive currents and the most powerful device – the UPFC cannot compensate zero-sequence unbalance current, because of the converter topology. My paper will show that the so-called DPFC can compensate both active and reactive, zero and negative sequence unbalanced currents. My paper consists of both active and reactive variations, using MATLAB/SIMULINK is simulated and its effects on the transmission lines observed. The simulated results are analyzed and validated with the real time results for the system considered

Optimal Reactive Power Compensation in Electric Transmission Line using STATCOM

The increased electric power consumption causes transmission lines to be driven close to or even beyond their transfer capacities resulting in overloaded lines and congestions. FACTS devices provide an opportunity to resolve congestions by controlling active and reactive power flows as well as voltages. FACTS devices can be connected to a transmission line in various ways, such as in series, shunt, or a combination of series and shunt. Shunt FACTS devices are used for controlling transmission voltages, power flow, reducing reactive losses, and damping of power system oscillations for high power transfer levels. The SVC and STATCOM are two important shunt FACTS devices. In this paper the optimal location of STATCOM for reactive power compensation in electric transmission line to control power flows is investigated. The reactive power compensation of the STATCOM is studied with three different locations in the transmission line. The STATCOM is located at the receiving end, middle and at 2/3 distance from the sending end of the transmission line. The MATLAB simulation results show the relative performance. Keywords - electric transmission line, FACTS devices, reactive power compensation, static synchronous compensator (STATCOM), shunt FACTS devices.

FACTS for Tapping and Power Flow Control in Half-Wavelength Transmission Lines

This paper presents a solution for transmission of bulk power over long distances. It allows the interconnection between remote power plants and power grids, which is a common situation in countries with continental dimensions, such as China, Russia, Brazil, and Canada, and also special projects like supergrids in Europe and Asia. This paper also presents an analytical analysis of series and shunt FACTS applications for tapping and power flow control in half-wavelength transmission lines. The proposed FACTS devices are able to drain or inject fractional active power in the half-wavelength line and simultaneously to control the main power flow through the line by means of reactive power compensation, without mischaracterizing its particular principle of half-wavelength operation. Simulation results from a frequency-dependent model of transmission line and the complete models of the series and the shunt FACTS devices were obtained in the PSCAD/EMTDC to demonstrate the feasibility of the proposed systems.

Application of Lyapunov Theory and Fuzzy Logic to Control Shunt FACTS Devices for Enhancing Transient Stability in Multimachine System

This paper proposes the control strategy of the shunt Flexible AC Transmission System (FACTS) devices to improve transient stability in multimachine power system. The multimachine power system has high nonlinear response after severe disturbance. The concept of Lyapunov energy function is applied to derive nonlinear control strategy and it was found that the time derivative of line voltage is not only can apply to control the shunt FACTS devices in multimachine system but also is locally measurable signal. The fuzzy logic control is also applied to overcome the uncertainty of various disturbances in multimachine power system. This paper presents the method of investigating the effect of the shunt FACTS devices on transient stability improvement. The proposed control strategy and the method of simulation are tested on the new England power system. It was found that the shunt FACTS devices based on the proposed nonlinear control strategy can improve transient stability of multimachine power system.

Effects of Shunt FACTS Devices on MHO Distance Protection Setting in 400 kV Transmission Line

This paper presents a study on the performances of distance relays setting in 400 kV in Eastern Algerian transmission networks at Sonelgaz Group (Algerian Company of Electricity) compensated by shunt Flexible AC Transmission System (FACTS). The facts are used for controlling transmission voltage, power flow, reactive power, and damping of power system oscillations in high power transfer levels. The direct impacts of SVC devices i.e. Thyristor Controlled Reactor (TCR) and the Thyristor Switched Capacitors (TSC) insertion, on the total impedance of a transmission line (<i>Z</i><SUB><i>AB</i></SUB>) protected by MHO distance relay are investigated. The modified setting zones protections (<i>Z</i><SUB><i>1</i></SUB>, <i>Z</i><SUB><i>2</i></SUB> and <i>Z</i><SUB><i>3</i></SUB>) have been calculated in order to improve the performances of distance relay protection and prevent circuit breaker nuisance tripping. The simulation results are performed in MATLAB software and show the direct impact of the thyristors firing angle (<i>α</i>) on the total impedance of the protected line.

Wide-Area Robust Coordination Approach of HVDC and FACTS Controllers for Damping Multiple Interarea Oscillations

A robust coordination approach for the controller design of multiple high-voltage direct-current (HVDC) and flexible ac transmission systems (FACTS) wide-area controls (WACs) is presented in this paper and has the aim of stabilizing multiple interarea oscillation modes in large-scale power systems. The suitable wide-area control signals, which are given to HVDC and FACTS wide-area controllers, respectively, are chosen from a large number of candidate items. Then, a sequential robust design approach is planned for the wide-area controller coordination of HVDC and FACTS devices. This approach is based on the robust control theory and is formulated as a standard problem of multiobjective mixed H2/H∞ output-feedback control with regional pole placement constraints. The linear matrix inequality (LMI) theory is applied to solve such a robust control problem. A case study on the 16-machine 5-area system, which is modified with one HVDC interconnected transmission, one shunt-FACTS device (SVC), and one series-FACTS device (TCSC), is performed to validate the robust performance in terms of multiple oscillations damping under various operating conditions.

A new multi-objective fuzzy-GA formulation for optimal placement and sizing of shunt FACTS controller

The location and sizing of FACTS controllers for voltage stability enhancement is an important consideration for practical power systems. In this paper, a strategy for placement and sizing of shunt FACTS controller using Fuzzy logic and Real Coded Genetic Algorithm is proposed. A fuzzy performance index based on distance to saddle node bifurcation, voltage profile and capacity of shunt FACTS controller is proposed. The proposed technique can be used to find the most effective location and optimal size of the shunt FACTS devices. The proposed approach has been applied on IEEE 14-bus and IEEE 57-bus test systems. The application results are promising.

Improvement of transient stability of power systems with STATCOM-controller using trajectory sensitivity

This paper discusses the use of trajectory sensitivity analysis (TSA) in determining the transient stability margin of a power system compensated by a shunt FACTS device. The shunt device used is static synchronous compensator (STATCOM). It is shown that TSA can be used for the design of controller for the STATCOM. The preferable locations for the placement of the STATCOM for different fault conditions are also identified. The effects of STATCOM in maintaining different bus voltages in the post-fault condition are studied. The STATCOM is modeled by a voltage source connected to the system through a transformer. The systems used for the study are the WSCC 3-machine 9-bus system and the IEEE 16-machine 68-bus system.

Investigating the Performance of Shunt FACTS for the Operation of Induction Motors under Different Voltage Sag Conditions

Shunt FACTS devices are prevalent in industrial application of induction motors. These equipments are effective to compensate disturbances and increase motor speeding up. In this study an assessment study between two different shunt FACTS (SVC and STATCOM) installed on terminals of motor is done. A conventional PI controller is used to control the thyristor firing angle of SVC or phase angle of STATCOM. A pole placement method is applied to specify the perfect gain settings of the controllers. The results of simulations display that STATCOM has better response over SVC for improving dynamic behavior of induction motor under ideal supply conditions. Power quality problem that influence the dynamic behavior of induction motor, include non ideal conditions such as harmonics, interruptions, voltage unbalance and voltage sags. Whereas voltage sags is one of the main cause of disturbances in distribution systems, the performances of the induction motor under symmetrical and unsymmetrical voltage sags are investigated in this study. The results prove that STATCOM is more effectual than SVC for reduction of transients and refinement the voltage profile.

Optimal Location of Shunt FACTS Devices in Long Transmission Lines to Improve Transient Stability

This paper deals with determination of the optimal location of shunt flexible a.c. transmission system (FACTS) devices for a long transmission line with pre-defined direction of real power flow. The validity of the mid-point location of shunt FACTS devices is verified with different such devices, using the actual line model. A two-area test system is used to show the effectiveness of off-centre location of the devices in improving transient stability. The results also show that optimal location depends upon the line loading and system initial operating conditions. It is expected that the work will be of use to students as well as researchers studying power system stability and FACTS devices.

Performance Comparison of Distance Protection Schemes for Shunt-FACTS Compensated Transmission Lines

This paper presents a comparative study of the performance of distance relays for transmission lines compensated by shunt connected flexible ac transmission system (FACTS) controllers/devices. The objective of this study is to evaluate the performance of various distance protection schemes on transmission lines with shunt-FACTS devices applied for midpoint voltage control. The impact of two types of shunt FACTS devices, static var compensator (SVC) and static synchronous compensator (STATCOM) on the transmission line distance protection schemes is studied for different fault types, fault locations and system conditions. The power system elements and the shunt-FACTS devices with their associated controllers are modeled using RSCAD/RTDS software. The results are based on the performance of commercial distance relays using a real time digital simulator (RTDS).

State-variable control of shunt FACTS devices using phasor measurements

This paper addresses the problem of state-variable stabilizing control of power system using shunt FACTS devices. This stabilizing control is activated in the transient state of a power system and is supplementary with respect to the main steady-state control of a FACTS device. Stabilizing control laws have been derived for a non-linear multi-machine system model using direct Lyapunov method with the aim to maximize the rate of energy dissipation during power swings and therefore maximization of damping. The proposed control strategy is executed by a non-linear multi-loop controller with rotor angles and speed deviations of synchronous generators used as the input signals. The input signals, obtained from a phasor measurement system, are necessary only from a small area around the controlled shunt FACTS device. Validity of the proposed state-variable control has been confirmed by computer simulation for a small multi-machine test system.

Analysis of Radial Distribution Systems With Embedded Series FACTS Devices Using a Fast Line Flow-Based Algorithm

Analysis of radial distribution systems with embedded series Flexible AC Transmission System (FACTS) devices is facilitated by a formulation of power flow equations with bus voltage magnitudes and line flows as independent variables. Since control variables such as the line and bus reactive powers figure directly in the formulation, handling the control action of FACTS devices in distribution systems is direct and easily implemented. Using the Breadth-First-Search (BFS), the bus incidence matrix of a radial distribution system is first rendered strictly upper diagonal, leading to reduced computational effort. All the common FACTS device models under steady-state conditions are easily incorporated in the new framework by a simple process of "variable swapping." Using IEEE standard systems, the line flow-based (LFB) formulation is shown to provide easy implementation with multiple series and shunt FACTS devices in the system and enable direct evaluation of the FACTS device ratings.

Performance of Distance Relays on Shunt—FACTS Compensated Transmission Lines

This paper presents a study of the performance of distance protection relays when applied to protect shunt Flexible AC Transmission System (FACTS) compensated transmission lines. The objective of this study is to evaluate the performance of distance relays on transmission lines with FACTS devices applied for mid point voltage control. Effect of two types of shunt FACTS devices, Static Var Compensators (SVC) and Static Synchronous Compensators (STATCOM) are studied. The study is conducted in three stages. First the situation is studied analytically, where the errors introduced in the impedance measurement due to the presence of shunt FACTS devices on the line are analyzed. In the second stage, the situation is simulated using transient simulation software, EMTDC. In this method, the response of FACTS devices for different fault conditions and system conditions is also modeled. This method brings out some unique problems that would be experienced by the distance relays due to some specific characteristics of the FACTS devices. Finally, the findings are confirmed by testing a commercial distance relay using a Real Time Digital Simulator (RTDS). The results obtained by testing the commercial relay validate the analytical and simulation studies.

Effects of Exact Line Model and Shunt Facts Devices on First Swing Stability Limit

Shunt FACTS devices are very commonly used in a modern power system to improve the voltage profile, damping, and stability of the system. However, most of the previous work on stability improvement used the simplified line model obtained by considering only the line inductance and ignoring the line resistance and capacitance. This article investigates the effects of various line parameters and shunt FACTS devices on first-swing stability limit of a simple power system. Four different ways of incorporating the line parameters into the line model are considered, and the concept of the equal area criterion is used in determining the first-swing stability limit of the system. The results obtained for various line models and shunt FACTS devices are also compared.

Improvement of First Swing Stability Limit by Utilizing Full Benefit of Shunt FACTS Devices

This paper proposes a new control strategy of shunt flexible ac transmission system (FACTS) devices to improve the first swing stability limit of a simple power system. It is shown that the speed based bang-bang control (BBC) is unable to use the entire decelerating area in maintaining stability. The proposed control strategy improves the stability limit first by maximizing the decelerating area and then fully utilizing it in counterbalancing the accelerating area. This requires to continue the operation of shunt FACTS devices at full capacitive rating until the machine speed reaches a reasonable negative value during the first return journey. Afterwards, the control can be switched to continuous type to improve system damping in subsequent swings. The proposed control strategy is then applied to both static var compensator and static synchronous compensators placed in a single machine infinite bus system. The same control strategy is also used for some faults in a multimachine system. In both the systems, it is found that the proposed control can provide significantly higher stability limit than that of the BBC. The mechanism of improving the stability limit is also described.