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This paper investigates an optimal methodology for mitigating low-frequency oscillation concerns in power systems. The study explores the synergistic integration of a power system stabilizer (PSS) and a flexible alternating current transmission system (FACTS) to formulate an intelligent controller. A comprehensive analysis encompasses various PSS design strategies, including lead-lag (LL), proportional-derivative-integral (PID), and fractional-order proportional-integral-derivative (FOPID) controllers. The FACTS device selected for this investigation is a static VAR compensator (SVC), highlighting the exceptional efficacy of FOPID-based PSS over alternative strategies with a power oscillation damper. The study extends its scope to encompass a comparative assessment of two distinct optimization algorithms: the moth flame optimization (MFO) and the antlion optimization (ALO). The research is conducted using a single-machine infinite bus power system (SMIB) as the case study platform. A total of four diverse test scenarios are executed under varying operating conditions. The evaluation of the developed method employs six distinct performance indices to investigate the developed controller thoroughly. The outcomes reveal that the MFO-optimized FOPID-PSS and SVC controller outperforms other control schemes. This optimized configuration demonstrates substantial improvements across all performance indices. These findings underscore the superior capabilities of the proposed approach in enhancing power system stability and performance. [ABSTRACT FROM AUTHOR]

This article presents the comparison of 3D and 2D finite element models of a power transformer designed for reactive power compensation stations. There is a lack of studies in the literature on internal electromagnetic phenomena in the active part of a transformer operated in these conditions. The results of numerical 2D and 3D calculations of no-load current and losses in the transformer core were obtained by using various methods and models. The impact of considering the hysteresis loop phenomenon on the calculation of core losses was investigated by using the Jiles–Atherton core losses model. The results obtained in the paper show that the model of the core must contain the areas representing the influence of overlappings on the no-load current and also on the flux density field in the core. The capacitive load of the transformer increases the flux density in the core limbs by several percent, so the power losses there must also increase accordingly. As a summary of the research, differences in the values of losses in each core element between the capacitive load and no-load conditions are presented. The results presented in this paper indicate that considering nonlinearity related to the magnetic hysteresis loop has a significant impact on the calculation of the core losses of power transformers. [ABSTRACT FROM AUTHOR]

This paper proposes a novel method to find the optimal location of the shunt connected Flexible AC Transmission Systems (FACTS) such as Static Var Compensator (SVC) or Static Synchronous Compensator (STATCOM) to the power system for regulating voltage levels of all buses. Three indices include Voltage Drop Index (VDI), Total Voltage Drop Index (TVDI), and Total Voltage Drop of Network Index (TVDNI) are presented to find the location of the SVC. Also, to minimize the solution space, a ranking list will be established. For the case studies, the IEEE 14-bus test system is selected, and an SVC is located in the system. Simulations are done in two cases: network loads increase with constant coefficient and randomly. According to simulation results in both cases, the proposed method can identify the optimal placement of SVC, and the voltage drop due to increasing the load will be compensated. For the IEEE 14-bus test system, the optimal location of the SVC is bus 9. Variable loads are considered for 24 h, and SVC is installed at bus 9 to validate the introduced method. Results show the voltage level for all buses is compensated so that the voltage levels are higher than the minimum voltage level, i.e. 95%. [ABSTRACT FROM AUTHOR]

Given the concern for maintaining voltage stability in power systems integrated with renewable power systems due to a mismatch in generation and demand, there remains a need to invoke flexible alternating current transmission system (FACTS) devices in the distribution network. The present paper deals with identifying the locations of placement of a static var compensator in an experimental IEEE 14-bus system; the voltage drop in different buses in an IEEE 14-bus system is calculated by the standard formula. The total voltage drop in the network (TVDN) is also calculated as a reference. The ranking of buses in order of decreasing voltage drop is made, and the weak buses are identified as those showing the maximum or near-maximum voltage drop for the installation of a Static Var Compensator (SVC). The optimum usable size is calculated using a Genetic Algorithm approach to optimize the installation cost. After size optimization, installing a 2 MW solar generator is considered for the weak and most potential bus, which suffers from voltage drops or power loss. Based on the generator at the weakest bus, the total power loss in the network is calculated and compared with a similar method to assess the efficiency of the proposed model. Thus, the voltage stability enhancement problem is solved by applying a Genetic algorithm (GA) to optimize SVC size and using the Total Voltage Drop in Network (TVDN) method to identify weak buses in the systems. It is found that the performance of the proposed system is comparable with another existing system. It is further observed that a gain in power loss to 6.56% is achievable by adopting the proposed strategy, and the gain is better than the other system. [ABSTRACT FROM AUTHOR]

Today, Flexible AC Transmission Systems (FACTS) devices provide local reactive power support in load centers and keep bus voltages within safe operating limits. In particular, the single use of parallel FACTS devices may not improve the safe operating conditions of the system depending on the load conditions. Therefore, avoiding parallel FACTS devices' high costs is crucial and determining their optimal places in the system. For this, Static Var Compensator (SVC), one of the parallel FACTS devices, is used. This study investigated the effects of multiple uses of SVC on different load buses on the maximum load parameter of the multi-machine system in a 3-machine 9-bus power system. Moreover, bus-voltage profiles and their changes in active-reactive power are studied in detail. In this study, three analysis methods were used. These are the no SVC, the single use of SVC, and the multiple uses of SVC. The Power Systems Analysis Program (PSAT) was preferred for this simulation study. As a result of the study, using multiple SVCs increases the maximum loading parameter value and improves the bus-voltage profiles and active-reactive power changes compared to others. [ABSTRACT FROM AUTHOR]

With increase in the number of photovoltaic system installations, the prospect of voltage deviation from the acceptable range in a distribution system is increasing. Voltage distribution can be controlled using step voltage regulators (SVRs) and static var compensators (SVCs); however, for their coordination, it is necessary to stringently adjust the set value for each distribution line. In this study, a method of applying model predictive control to the coordination between an SVR and an SVC is investigated. In this paper, we first describe the proposed method and subsequently present the results of the performance comparison of the proposed and conventional methods to validate the effectiveness of the proposed method. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The trend of increasing demand creates a gap between generation and load in the field of electrical power systems. This is one of the significant problems for the science, where it require to add new generating units or use of novel automation technology for the better utilization of the existing generating units. The automation technology highly recommends the use of speedy and effective algorithms in optimal parameter adjustment for the system components. So newly developed nature inspired Bat Algorithm (BA) applied to discover the control parameters. In this scenario, this paper considers the minimization of real power generation cost with emission as an objective. Further, to improve the power system performance and reduction in the emission, two of the thermal plants were replaced with wind power plants. In addition, to boost the voltage profile, Static VAR Compensator (SVC) has been integrated. The proposed case study, i.e., considering wind plant and SVC with BA, is applied on the IEEE30 bus system. Due to the incorporation of wind plants into the system, the emission output is reduced, and with the application of SVC voltage profile improved. [ABSTRACT FROM AUTHOR]

This paper presents the application of Flexible Alternating Current Transmission System (FACTS) devices based on heuristic algorithms in power systems. The work proposes the Autonomous Groups Particle Swarm Optimization (AGPSO) approach for the optimal placement and sizing of the Static Var Compensator (SVC) to minimize the total active power losses in transmission lines. A comparative study is conducted with other heuristic optimization algorithms such as Particle Swarm Optimization (PSO), Timevarying Acceleration Coefficients PSO (TACPSO), Improved PSO (IPSO), Modified PSO (MPSO), and Moth-Flam Optimization (MFO) algorithms to confirm the efficacy of the proposed algorithm. Computer simulations have been carried out on MATLAB with the MATPOWER additional package to evaluate the performance of the AGPSO algorithm on the IEEE 14 and 30 bus systems. The simulation results show that the proposed algorithm offers the best performance among all algorithms with the lowest active power losses and the highest convergence rate. [ABSTRACT FROM AUTHOR]

This paper introduces a new partitioned ant lion optimizer (PALO) strategy to improve the solution accuracy and quality of the optimal power flow (OPF) considering multi Static VAR Compensator (SVC) and Thyristor Controlled Series Controller (TCSC)-based FACTS devices. An interactive partitioning structure-based ALO is proposed to improve the solution of OPF by creating an interactive equilibrium between diversification and intensification during the search process. The decision variables such as active power, voltage magnitudes of generating units, tap transformers; reactive power of Static VAR Compensator (SVC), and the reactance of TCSC devices are optimized using a flexible partitioned process. Three objective functions, such as total fuel cost, total power loss, and total voltage deviation have been optimized considering load growth. The robustness of the proposed PALO has been validated on three test systems, the IEEE 30-bus, and two large test systems, the 300-bus and 2736 ps bus of the Polish power system. Results compared to many recent techniques prove the particularity and competitiveness of the proposed optimization strategy-based PALO. [ABSTRACT FROM AUTHOR]

Transient Stability is the capability of a system to be able to return to its normal state after experiencing large disturbances. The static var compensator (SVC) is a shunt device of the flexible AC transmission systems (FACTS) family using power electronics to improve transient stability in power system. For the SVC control, it is usually used a PI controller, although PI controller is simpler and cheaper but not suitable when power system is subjected to transient stability since power system become non-linear system. In order to overcome this problem, the PI controller combined with Fuzzy controller is designed. Two types of faults were considered for this study to examine the effect of the fuzzy-SVC controller on system transient stability, the proposed fault types are single line to ground fault and three lines to ground fault. The performance and behavior of the designed fuzzy controller compared with that of the conventional PI controller in term of terminal voltage, rotor angle, and transmission line active power. [ABSTRACT FROM AUTHOR]

This study investigates the mitigation of transient overvoltages (TOVs) in a microgrid supplied by renewable distributed generation resources, which include photovoltaic (PV) generators, hydro generation unit, and wind power generators. ATP/EMTP is used in this study as electromagnetic transient software. Accurate simulation models are needed to carry out the study. Therefore, a three‐phase PV system model based on the equivalent Newton–Raphson circuit is used, and the efficiency of the PV system components is studied. Then, the use of the PV generation system model for switching studies is investigated using two different electrical systems. The use of different mitigation methods for TOVs at the microgrid is investigated. Three different mitigation methods are considered. First, a device to compensate reactive power such as static var compensator (SVC) is represented as a TOVs mitigation method. Then, adding a supercapacitor as TOVs mitigation method is evaluated. After that, a combination of active and reactive power simultaneously to mitigate TOV, by the addition of SVC to a supercapacitor, is investigated. The grid‐connected mode and isolated mode of the microgrid are considered. The results show that the usage of SVC with supercapacitor has the ability to mitigate the transient overvoltage and the waveforms are more regular. [ABSTRACT FROM AUTHOR]

Flexible AC transmission systems (FACTS) technology is widely adopted and utilized to maintain the performance of power systems. However, the improvements of power system performance achieved by FACTS devices depend on the right sizing and allocation of such devices. For technical and economic considerations, a FACTS device's location and size should be selected very carefully in order to maximize its benefits to the power system. In this paper, the sizing and location of a static VAR compensator (SVC) are optimally determined using a new optimization technique called lightning attachment procedure optimization (LAPO). The optimal allocation of the SVC is determined regarding the improvement of voltage deviation index and the reduction of total active power losses. The system is optimized in two cases: once without SVC installation in order to find out the optimal settings of the system that achieve the objective functions, and another time with SVC installation to determine its optimum sizes and locations by which the required objective functions are achieved. Then the system performance is analyzed after optimization with and without SVC devices to show the impact of the optimum sizing and location of the SVC on the system. The study is validated using the standard IEEE 30-bus system, while the developed LAPO is performed by MATLAB M-Files and the system performance analysis in different cases is performed by NEPLAN software. [ABSTRACT FROM AUTHOR]

This article presents a novel nonlinear coordinate damping controller (NCDC) for high‐voltage direct current (HVDC) and static var compensator (SVC) based on synergetic control theory, which can improve the stability of interarea power system and multi‐infeed HVDC system by quickly changing the transmission power of HVDC and reactive power of SVC. The traditional control design of HVDC and SVC can improve the stability, but there may be a negative interaction between the controllers of HVDC and HVDC or HVDC and SVC. Furthermore, the power system is a strong nonlinear system, and the controller designed by a linearized model may reduce its performance. To solve these problems, this article first constructs a unified macro variable and manifold, which contains the model of HVDC and SVC. The manifold sets the deviation value of the center of inertia (COI) frequency of the two systems connected by HVDC to zero. Then, a nonlinear HVDC and SVC coordinated controller is derived based on the synergetic control theory. The global stability of the controller is proven by the Lyapunov theorem. Finally, the simulation results in a two‐area power system and a multi‐infeed system using the power systems computer aided design (PSCAD) show the effectiveness and superiority of the proposed controller. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Power quality is often defined as the electrical network's or the grid's capability to deliver a clean and stable power supply. Flexible AC transmission systems (FACTS) devices consist of power electronics circuits that's depend on the thyristor for controlling active and reactive power flows and to maintain the voltage within the allowable limits in normal and abnormal operating conditions. Static Var Compensation (SVC) is one of the most important FACTS devices, that's combined between shunt capacitor and shunt reactor, that's connect with the system by control setting. The control of reactive power by SVC module is depending on firing angle of thyristors. The shunt capacitor module can be called thyristor switched capacitors (TSC) and thyristor-controlled reactors (TCR), that's provide harmonic filters and/or dynamic shunt compensation. TSC operates with series bi-directional thyristor and a damping reactor to prevent the shunt resonance, the thyristors are used to control the capacitor to operate at the required value. TCR operates with series thyristor switch for control. SVC is easy and more accurate to operate with the medium voltage. SVC can be connected with the extra high voltage system via step-down transformer. This paper discusses the SVC to be uses to improve the power system quality, by adding the reactive power to the system. Also, this paper discusses the SVC control by using the MATLAB/Simulink software to discuss the step operation for the SVC with the power system. [ABSTRACT FROM AUTHOR]

In this research, a complex engineering failure analysis is done for a static VAR compensator (SVC), it was installed in Perú 220 kV system. The research introduce the selected results of the simulations and field tests completed during the fault, mitigation and corrective activities performed at the thyristor valve, which is installed in the thyristor switched capacitor (TSC) and thyristor controlled reactor (TCR) of the SVC. This paper proposes the most feasible solution to overcome the failure of the TSC based on snubber resistor in the SVC. In order to investigate the causes of this failure, various measurements were carried out on the TSC. It was concluded that a snubber resistor design needs two special test for determinate a problem or abnormal condition; a special test should be done in the factory acceptance test (FAT), site acceptance test (SAT) and to execute a maintenance diagnosis, to prevent a failure in the thyristor valve from TSC. This failure has happened in the standby system, the susceptance reference is forced to follow the susceptance reference received from the active system. There is however, a delay in the transfer of data from the active to the standby system. During transient conditions this may cause a difference in thyristor firing angles between the systems. The simulated current in the standby system does not agree with the measured current, which is controlled by the active system, an advanced diagnosis and design review is developed for to avoid a sudden failure. The feasibility of these solutions was verified through the computer simulation with PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

This study investigates three different techniques to mitigate the switching overvoltages (SOVs) in the microgrids. At first, the effectiveness of reactive power compensation devices, such as static var compensator (SVC), is evaluated. After that, the performance of the supercapacitor (SC), as an energy storage device, is studied. Finally, with the addition of the SVC to the SC, the possibility to mitigate SOV by compensating both active and reactive power simultaneously is investigated. SOVs result due to unsymmetrical switching operation during de‐energisation (disconnection) procedures. The μG two operational modes; grid connected mode and isolated mode, are considered. A small hydro generation unit and three variable speed, double‐fed induction generator‐based wind turbines are the main renewable power generation units in the tested microgrid system. Alternative Transient Program is used in this study for simulating the compensation device, the energy storage device and the investigated microgrid. The study shows that through the μG two operational modes, the SC has priority over the other two investigated mitigation methods. Furthermore, using the SC or SC with SVC, the results have more regular voltage waveforms. [ABSTRACT FROM AUTHOR]

Local latency adversely affects the stabilising performance of damping controllers especially in the two‐level control scheme. By considering both wide area and local latencies, this study presents the two‐level coordinated control which consists of wide area centralised and local controls of power oscillation damper (POD) and power system stabiliser (PSS) for robust power oscillation damping. The PODs are equipped with the doubly fed induction generator (DFIG) wind turbine, the solar photovoltaic generator (SPV), and the static VAR compensator (SVC). The centralised PODs of DFIG, SPV, SVC, and the centralised PSSs act as the primary damping controllers. When the communication failure occurs, the local PODs of such devices and the local PSSs are activated and used as the backup damping controllers. To achieve the damping performance and robustness, the parameters of centralised and local controllers are individually optimised based on the worst scenarios determined by the lowest damping ratio of target inter‐area oscillation modes. Study results in New England and New York IEEE 68‐bus system demonstrate that the proposed two‐level coordinated controllers are superior to the conventional two‐level controllers in terms of damping performance and robustness against various operating conditions. [ABSTRACT FROM AUTHOR]

SUMMARY Recent years, installation of photovoltaic (PV) system is active by the environmental problem and feed in tariff system. Due to PV's output fluctuation, the static var compensator (SVC) made by power electronics technology is planning to install in distribution system. The SVC is expected for maintain the voltage. But SVC differs in a theory of operation of the existing voltage controller load ratio control transformer (LRT) and step voltage regulator (SVR). Because the SVC operation makes the system impedance changes, the existing voltage controller may not operate effectively. In this study, the intelligent-control method which used the radial basis function (RBF) network is proposed. This method can reduce the effects of the SVC operation by including the performance characteristics of SVC in the conventional method. An advantage of unnecessary arrangement attention of the SVC setup node and easy cooperation with the existing equipment is obtained by applying this method. [ABSTRACT FROM AUTHOR]

This paper proposes a novel method for layered media transmission in mobile broadcast systems, which is referred to as the layer-mixed forward error correction (FEC). Unlike the existing unequal error protection and layer-aware FEC which decode each layer symbols with a probability, the new approach is capable of decoding each layer data deterministically as long as enough symbols are received corresponding to the specific layer. The lower layer is always decoded prior to upper layers, which facilitates the delivery of scalable media stream, especially in mobile TV services with heterogeneous networks and terminals. In order to evaluate the performance fairly, this paper compares the minimum channel capacity required by several FEC schemes. The experimental results show that the new approach outperforms the existing schemes in severely degraded channel situations. [ABSTRACT FROM PUBLISHER]

Ferroresonance is phenomena, which emerged in case of different circumstances such as short circuit and breaker phase failure. In addition, plant outage is another cause of ferroresonance. Ferroresonance may cause maloperation of some protective devices such as differential protection. In this study, Manitoba hydro network is analysed in power systems computer‐aided design/electro‐magnetic transient design and control to recognise ferroresonant configurations in case of plant outage. Impact of ferroresonance on maloperation of differential protection is analysed. A static var compensator (SVC) is installed at the mid‐point of the network to mitigate ferroresonance. Operation of relay is assessed in the presence of SVC; furthermore, effect of parameters and components of SVC on operation of differential protection is investigated. Then, an adaptive algorithm is designed in differential relay to recognise ferroresonance and prevent maloperation of the relay. [ABSTRACT FROM AUTHOR]

This paper proposes the design of auxiliary-coordinated controller for static VAR compensator (SVC) and thyristor-controlled series capacitor (TCSC) devices by adaptive fuzzy optimized technique for oscillation damping in multimachine power systems. The performance of the coordinated control of SVC and TCSC devices based on feedforward adaptive neuro fuzzy inference system (F-ANFIS) is compared with that of the adaptive neuro fuzzy inference system (ANFIS) structure based on recurrent adaptive neuro fuzzy inference system (R-ANFIS) network architecture. The objective of the coordinated controller design is to tune the parameters of SVC and TCSC fuzzy lead lag compensator simultaneously to minimize the deviation of rotor angle and rotor speed of the generators. The performance of the system is enhanced by optimally tuning the membership functions of fuzzy lead lag controller parameter of the flexible AC transmission system (FACTS) by R-ANFIS controller. The training data for F-ANFIS and R-ANFIS are generated by conventional linear control technique under various operating conditions. The offline trained controller tunes the parameter of lead lag controller in online. The oscillation damping ability of the system is analyzed for three-machine test system by calculating the standard deviation and cost function. The superior performance of R-ANFIS controller is compared with various particle swarm optimization-based feedforward ANFIS controllers available in literature. [ABSTRACT FROM AUTHOR]

Increasing maximum power system loadability while maintaining bus voltages and line loadings constraints by flexible AC transmission system (FACTS) devices is one of the main issues in power system studies. One of the shunt FACTS devices widely used in power system is static var compensator (SVC). Its performance on power system is highly dependent on its number, location and operating point. This study presents a two‐level procedure to find optimal number, locations, and operating points of SVCs in a power system. At the first level, the goal is to maximise loadability of the power system. At this level, by using a method based on iterative process, applying SVCs to the power system, and increasing load factor, the optimisation algorithm seeks to find locations and operating points of SVCs that fulfil bus voltages and line loading constraints. This process continues until the increase in the number of SVCs does not lead to an increase in loadability. At the second level and for a certain number of SVCs, power system losses, total voltage deviations (TVD), and SVC installation cost are minimised at specific loadability. In this study, hybrid imperialist competitive algorithm and genetic algorithm (HICAGA) have been used for optimisation. [ABSTRACT FROM AUTHOR]

Large-scale integration of wind turbine generators (WTGs) may have significant impacts on power system operation with respect to system frequency and bus voltages. This paper studies the effect of Static Var Compensator (SVC) connected to wind energy conversion system (WECS) on voltage profile and the power generated from the induction generator (IG) in wind farm. Also paper presents, a dynamic reactive power compensation using Static Var Compensator (SVC) at the a point of interconnection of wind farm while static compensation (Fixed Capacitor Bank) is unable to prevent voltage collapse. Moreover, this paper shows that using advanced optimization techniques based on artificial intelligence (AI) such as Harmony Search Algorithm (HS) and Self-Adaptive Global Harmony Search Algorithm (SGHS) instead of a Conventional Control Method to tune the parameters of PI controller for SVC and pitch angle. Also paper illustrates that the performance of the system with controllers based on AI is improved under different operating conditions. MATLAB/Simulink based simulation is utilized to demonstrate the application of SVC in wind farm integration. It is also carried out to investigate the enhancement in performance of the WECS achieved with a PI Controller tuned by Harmony Search Algorithm as compared to a Conventional Control Method. [ABSTRACT FROM AUTHOR]

Multi-hop relaying combined with scarcity of wireless resources in ad-hoc networks can deteriorate the quality of service. As a result, one of the major challenges in video streaming over ad-hoc networks is enhancing users' experience and network utilization. The emergence of scalable video coding standard enables smooth adaptation of video quality to network conditions. In this paper, we study two optimization problems: (1) maximize the global quality of experience of all users and (2) maximize the number of qualified streams. We formulate the both problems as mixed integer linear programming problems. These optimization problems are shown to be NP-hard. Consequently, we propose heuristic algorithms to solve them. Simulation results show that the proposed algorithms can provide the near-optimal video quality while the calculation times are much shorter than the one of optimal solution. [ABSTRACT FROM AUTHOR]

The increase in the scale and complexity of interconnected power systems leads to multiple electromechanical oscillations. Therefore, the electric network needs to be made more stable. One type of Flexible alternating current transmission systems (FACTS) devices, namely the static VAr compensator (SVC), can be installed at buses to increase the stability margins and dampen the power system oscillations by exchanging capacitive and/or inductive load to maintain and/or control specific parameters of electrical power systems. The efficiency and performance of the SVC depend on its optimal location. Consequently, seeking the optimal placement for SVC has become a key issue. In this paper, we propose a novel method to find the optimal location for the SVC based on a two-step approach. First, an energetic approach based on the combination of the controllability Gramian critical energy analysis with the balanced realization reduction technique is used to search for several feasible locations; then the transient stability is analyzed to compare and determine an optimal location through various test cases. The effectiveness of the proposed method has been demonstrated on the IEEE 39-bus England power system and compared with the modal controllability index. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

In this study, power system stabiliser (PSS), static VAR compensator (SVC), and thyristor controlled series capacitor (TCSC) controllers are simultaneously used to increase the stability and damping of the oscillations of a multi‐machine power system. By SVC, the transferrable power in the steady state can be increased and the voltage profile can be controlled along the line. TCSC can regulate line impedance and therefore, increase the transferred power of the system. PSS is added to excitation system to enhance the damping of electric power system during low frequency oscillations. SVC, TCSC, and PSS can combine with each other for further damping and stability; therefore, their coordination is very important. Then, adaptive velocity update relaxation particle swarm optimisation algorithm is used to optimise the parameters of PSS, SVC, and TCSC simultaneous controllers. The robustness of the proposed algorithm has been tested on 16‐machine 68‐bus power system. [ABSTRACT FROM AUTHOR]

In this study main reactive power calculation methods are evaluated and compared. Furthermore, a novel simple method that can be used for calculation of reactive power in electric arc furnace (EAF) plants is proposed. The focus here is on their application in the control system of static VAr compensators (SVCs). SVC can compensate only the fundamental harmonic component. So the reactive power signal used in the control system should be sensitive only to the main harmonic component. In addition, the reactive power calculation should be fast enough that SVC can follow the quick changes of the load to mitigate the flicker efficiently. To compare various reactive power calculation methods and to evaluate the proposed method, the simulated known loads are used beside huge amount of practical data recorded in Mobarakeh Steel Company in Isfahan/Iran. Results show the proposed method has the best performance for SVC control system. [ABSTRACT FROM AUTHOR]

This paper provides an overview of Scalable High efficiency Video Coding (SHVC), the scalable extensions of the High Efficiency Video Coding (HEVC) standard, published in the second version of HEVC. In addition to the temporal scalability already provided by the first version of HEVC, SHVC further provides spatial, signal-to-noise ratio, bit depth, and color gamut scalability functionalities, as well as combinations of any of these. The SHVC architecture design enables SHVC implementations to be built using multiple repurposed single-layer HEVC codec cores, with the addition of interlayer reference picture processing modules. The general multilayer high-level syntax design common to all multilayer HEVC extensions, including SHVC, MV-HEVC, and 3D HEVC, is described. The interlayer reference picture processing modules, including texture and motion resampling and color mapping, are also described. Performance comparisons are provided for SHVC versus simulcast HEVC and versus the scalable video coding extension to H.264/advanced video coding. [ABSTRACT FROM PUBLISHER]

In this paper a simple and efficient heuristic search method based on the artificial bee colony (ABC) algorithm is presented and used for the optimal power ow (OPF) problem in power systems with static VAR compensator (SVC) devices. The total generation cost of a power system with SVC devices (which improve the voltage stability at load buses) is optimally minimized with the use of ABC. The ABC, which is based on the foraging behavior of honey bees searching for the best food source, is a recently proposed optimization algorithm. The performance of the presented ABC algorithm was tested and verified on the IEEE 11-bus and IEEE 30-bus power systems by comparing it with several other optimization methods. Furthermore, ABC is used not only for optimizing the total generation cost and active power loss, but also for improving the voltage stability of the 22-bus power system in Turkey. Our results illustrate that ABC can successfully be used to solve nonlinear problems related to power systems. [ABSTRACT FROM AUTHOR]

This paper proposed an approach to determine optimal location of SVC (Static Var Compensator) to improve the voltage profile and maximize system loadability in power networks connected to a doubly-fed induction generator (DFIG)-based wind farm. A variable reactance model for SVC is presented in steady state studies and implemented in the load flow program with embedded Flexible AC Transmission Systems (FACTS) devices. The continuation power flow method is used to determine optimal location of SVC and steady state stability margin, based on closing to point of voltage collapse. As an important result in this paper, we obtained an optimal location of SVC devices on wind farm by calculating the new indices such as maximum loading point (MLP) and mega watt margin (MWM). A case study and simulation are done on modified IEEE14 bus test system. [ABSTRACT FROM AUTHOR]

Based on differential algebraic (DA) subsystem models of power system components including the nonlinear controllers, which are called component structural complex models, this paper presents a model reduction method (MRM). For the dynamic differential equations, based on the property that the nonlinearity of the controller compensates that of the component completely (or partially), the presented method uses the linear dynamic equations to describe the compensated dynamics. For the algebraic connection equations, the new defined state variables are used to substitute the original state variables for keeping the connection relation invariable. By selecting generators and static var compensators (SVC) as examples, the paper presents the basic procedure of the proposed reduction method for power system component complex models in detail. The numerical simulation indicates that the derived simplified models matches the original one very well in both dynamic response behaviors and the connection relation with the external system. [ABSTRACT FROM AUTHOR]

This paper presents the coordinated design of multiple FACTS supplementary damping controllers to improve system small-signal stability. A BMI-based multi-objective multi-model system approach is formulated to solve the robust damping control problem. Two-step method is proposed to determine controller variables. Regional pole placement and control effort optimization are set as the control objectives. An SVC and a TCSC damping controller are designed sequentially with minimized decoupling effort. Selection of the feedback signals for the FACTS damping controllers is realized by evaluating the modal residues of each feedback signal to the system input. To cover multiple inter-area oscillation modes, wide-area decentralized control methodology is proposed and remote feedback signals are selected. Real-time simulation is carried out on real-time digital simulator (RTDS) to test the performance of the proposed controller. The results show that the FACTS damping controllers are feasible and able to increase system damping to a satisfactory level under different system operating points. [ABSTRACT FROM PUBLISHER]

In this paper, a new sensitivity-based methodology has been proposed for optimal placement of a static VAr compensator (SVC)/static synchronous compensator (STATCOM) to minimize load curtailment that is required to ensure system security, integrity and reliability after undesirable changes occur in the system. SVC/STATCOM has a significant impact on control of reactive power and thereby system bus voltages. This motivated to develop an appropriate approach to find their optimal location in order to accomplish the above said objective. The suggested sensitivity factors have been defined as the rate of change in load curtailment with respect to the change in SVC/STATCOM control settings. To investigate the effectiveness of the proposed methodology an optimal power flow problem has been formulated with an objective to minimize the load curtailment and is tested on IEEE 14-bus and practical 75-bus Indian systems. It is observed from the obtained results that the required load curtailment drastically reduced with the placement of SVC/STATCOM, along with improvement in system voltage profile at various operating conditions. This methodology can be used to limit the amount of load curtailment, thereby reducing lost revenue, outage cost, customer's service interruption and possibly civil unrest in some areas. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Variable speed wind turbine generators (WTGs) are replacing traditional fossil fuel based synchronous generators in the generation fleet as wind penetration increases. These variable speed WTGs are decoupled from the grid by power electronics inverters and usually generate less fault current compared to synchronous generators. As a result, system strength (indicates the fault recovery capability) at the point of common coupling (PCC) of wind power plants may reduce. A minimum value level of system strength is essential for wind power plants to properly identify and overcome a fault. To enhance system strength at wind PCC buses, supplementary devices such as synchronous condenser and Static VAR Compensator (SVC) can be deployed to have additional fault current. Since these devices are expensive, their optimal allocation considering economic feasibility is a major concern. In the existing literature, locations and ratings of the optimally allocated synchronous condenser are reported. However, this approach may cause oversizing of synchronous condensers. In addition, a SVC can be utilised instead of a synchronous condenser to enhance system strength. However, no detailed study is carried out yet to find the optimal size of SVCs. Evidently, both synchronous condenser and SVC can be installed to improve system strength. However, no comprehensive techno-economic assessment is performed for selecting an appropriate choice between them. To address these research gaps, this paper develops a framework to find the optimal sizes of synchronous condensers and SVCs by taking into account the long-term financial viability. Also, to ensure the maximum possible fault contribution, synchronous condensers/SVCs are connected directly to those wind PCC buses where system strength is below the acceptable limit. Afterwards, a detailed techno-economic assessment using synchronous condenser and SVC is performed in a wind dominated grid. In addition, post-fault voltage recovery characteristics with optimally sized synchronous condenser and SVC are explored. The developed methodology is applied to the IEEE 39 bus test system considering 45% wind power penetration scenario. Also, the performance of the proposed approach is compared to that of an existing technique. Finally, based on the technical and economic aspects, a better choice between synchronous condenser and SVC is recommended to improve system strength under high wind penetration. • System strength is improved in a wind dominated grid. • Optimal sizes of synchronous condenser and SVC are found. • Long-term techno-economic assessment is performed. • Technical and economic aspect of synchronous condenser and SVC are compared. • Synchronous condenser is found to be a better choice than SVC. [ABSTRACT FROM AUTHOR]

In electrical arc furnaces (EAFs), an unstable arc leads to unfavorable operation of the EAF, which can be rectified by using series reactors. Installation of the series inductor affects some electrical parameters of the EAF, such as arc stability, power factor, arc length, and the EAF efficiency. Furthermore, it reduces the effective transferred power to the EAF. To achieve desired transferred power after installation of the series reactors, the secondary voltage of the EAF transformer should be increased. However, after any tap changing of the EAF transformer, arc stability and other relevant parameters are affected. So the impact on the EAF electrical magnitudes caused by changes in the series reactor and in the EAF transformer tap should be simultaneously studied. This research deals with a new method for optimal setting of the series reactor and EAF transformer tap to achieve the EAF best performance. Using a nonlinear model for the EAF, its electrical characteristics, at nominal transformer current and for all of the possible transformer and reactor taps, are calculated and the results are tabulated. Using these tables, the optimal setpoint for transformer and series reactor taps is determined in different conditions. Finally, the method is investigated from an economic point of view. [ABSTRACT FROM AUTHOR]

Intermittent power generation of wind turbines and photovoltaic plants creates voltage disturbances in power distribution networks which may not be acceptable to the consumers. To control the deviations of the nodal voltages, it is necessary to use fast dynamic control of the reactive power in the distribution network. Implementation of the power electronic devices, such as Static Var Compensator (SVC), enables effective dynamic state as well as a static state of the nodal voltage control in the distribution network. This paper analyzed optimal sizing and location of SVC devices by using genetic algorithm, to improve nodal voltages profile in a distribution network with dispersed photovoltaic and wind power plants. Practical application of the developed methodology was tested on an example of a real distribution network. [ABSTRACT FROM AUTHOR]

In this paper voltage stability is analysed based not only on the voltage deviations from the nominal values but also on the number of limit violating buses and severity of voltage limit violations. The expression of the actual state of the system as a numerical index like severity, aids the system operator in taking better security related decisions at control centres both during a period of contingency and also at a highly stressed operating condition. In contrary to conventional N - 1 contingency analysis, Northern Electric Reliability Council (NERC) recommends N - 2 line contingency analysis. The decision of the system operator to overcome the present contingency state of the system must blend harmoniously with the stability of the system. Hence the work presents a novel N - 2 contingency analysis based on the continuous severity function of the system. The study is performed on 4005 possible combinations of N - 2 contingency states for the practical Indian Utility 62 bus system. Static VAr Compensator is used to improve voltage profile during line contingencies. A multi- objective optimization with the objective of minimizing the voltage deviation and also the number of limit violating bus with optimal location and optimal sizing of SVC is achieved by Particle Swarm Optimization algorithm. [ABSTRACT FROM AUTHOR]

This paper presents a novel Flexible AC Transmission Systems (FACTS) placement method based on mixed integer quadratically constrained programming (MIQCP). The method is capable of allocating both Static VAR Compensator (SVC) and Thyristor-Controlled Series Capacitor (TCSC) either separately or simultaneously, to determine concurrently their numbers, locations as well as sizes. The optimization objective is to maximize loadability and minimize compensation. The proposed MIQCP formulation partially incorporates key quadratic constraints, which were absent in mixed integer linear programming (MILP) placement methods reported in the past. The authors demonstrate significant improvements in accuracy over past MILP methods, with case studies presented on the simplified Southeast Australian network, and on a large scale real-world power system, Powerlink Queensland's HV transmission network, with 886 buses and 1087 branches. In addition, results and observations for simultaneous allocation of multiple TCSCs and SVCs in these networks are demonstrated in this paper. [ABSTRACT FROM AUTHOR]

Microgrids are small scale energy grids that can provide adequate energy supply to cover regional demand by integrating renewable energy generation and storage technologies. This paper develops a high performance dynamic model of a microgrid system comprising a wind turbine, a PV, a fuel cell, a micro gas turbine generator, an energy storage, electric loads with variable load profile and flexible AC transmission system (FACTS) devices. The FACTS devices based on static VAR compensators have been employed as a supervisory controller. Key performance indicators such as microgrid power losses, buses voltage deviations, buses power factor, buses voltage total harmonic distortion and voltage-frequency deviation are used to evaluate the performance of this microgrid in grid-connected and islanding modes. The results obtained from the Matlab/Simulink environment show that the proposed microgrid design with SVC has the ability to meet its special requirements such as bus voltages stabilization, reduction of feeder losses, power factor enhancement and mitigation of total harmonic distortion using SVC in grid-connected and islanding modes. [ABSTRACT FROM AUTHOR]

The time varying nature of electric arc furnace (EAF) gives rise to voltage fluctuations, which produces the effect known as flicker. Employing reactive power compensation devices such as static VAr compensator (SVC) is one of the main approaches to mitigate this phenomenon. By utilising prediction methods to forecast EAFs reactive power consumption for a half‐cycle ahead, performance of SVC can be enhanced substantially. This study proposes a rolling Grey model and a Grey–Markov method to predict the actual reactive power of Mobarakeh Steel Company, Isfahan/Iran. To investigate the efficiency of the proposed methods the results are compared with the results of EAFs reactive power compensation when no prediction method is employed. Furthermore, autoregressive moving average (ARMA) models with updating coefficients, which are studied in the literature are used to predict EAF reactive power. Various methods for updating ARMA coefficients including normalised least mean square, recursive least square method and an online genetic algorithm are used. By comparing the indices which are defined using the concept of flicker frequency and power spectral density, the superiority of Grey–Markov and rolling Grey model over the aforementioned prediction methods is investigated. [ABSTRACT FROM AUTHOR]

Electric train system is a very large load for the power network. This load consumes a large amount of reactive power. In addition, it causes a massive unbalance to the network, which results in many problems such as voltage drops, high transmission losses, reduction in the transformer output ability, negative sequence current, mal-operation of protective relays, etc. In this paper, a novel real-time optimization approach is presented to adjust the static VAR compensator (SVC) for the traction system to realize two objectives; current unbalance reduction and reactive power compensation. A multi-objective optimization technique entitled non-dominated sorting genetic algorithm (NSGA-II) is used to fulfill the regarded objectives simultaneously. A comprehensive simulator has been designed for electric train network modeling that is able to adjust the parameters of SVC in an optimum manner at any time and under any circumstances. The results illustrate that the provided method can efficiently reduce the unbalancing in current as well as supply the demanded reactive power with acceptable precision. [ABSTRACT FROM AUTHOR]

In this paper a method for the development of a static VAR compensator (SVC) control algorithm is presented. The proposed algorithm has been designed with the objective of eliminating the negative impact of electric arc furnaces on the power system. First, a mathematical model of the proposed SVC controller in the d-q synchronous rotating coordinate system is developed. An analysis under dynamic and steady state conditions is also carried out. The efficiency of the presented controller is demonstrated by means of computer simulations of an actual steel-factory network model. The major advantages of the proposed controller are better flicker compensation, increased ability to regulate voltage and the need for only one-point network measurements. [ABSTRACT FROM AUTHOR]

Memory bandwidth and on-chip memory requirements are critical issues in motion estimation (ME) implementations for video compression. The H.264/AVC scalable extension (SVC) provides variable frame rate and resolution video in a compressed digital sequence with interlayer prediction, which complicates the problems of limited memory bandwidth and on-chip memory size. In this paper, an ME algorithm is proposed for the hardware encoder design of SVC that meets memory bandwidth and on-chip memory requirements. Clustered motion estimation and coding sequence reordering at macroblock and frame level processing are proposed. Compared with existing algorithms, the proposed algorithm has a 49.20% lower external memory bandwidth and reduces the on-chip memory requirement by 80.45% with video quality enhancements of up to 0.087, 0.090, 0.078, and 0.070dB for four-layer (FullHD-HD-D1-CIF) spatial scalability, respectively. [ABSTRACT FROM PUBLISHER]

Voltage stability is a common issue in developing power system. It is mainly affected by reactive power balance in the system. If reactive power is not well planned and managed, there is possibility of occurrence of voltage instability in the system. One solution to prevent voltage instability in the system is by VAR compensation. In this work, new technique to determine the placement of different types of shunt VAR compensators based on sensitivity method is presented. Simultaneous planning of SVC and STATCOM placement is also conducted. Improvement in system stability is achieved using the method. [ABSTRACT FROM AUTHOR]

This paper aims to select the optimal location, size, and setting parameters of SVC (Static Var Compensator) controller using MOPSO (multi-objective particle swarm optimization) to improve the power system stability in a multi-machine power system. Though power system stabilizers are mandatory requirements for damping of oscillations, its performance still gets affected by changes in network configurations, load variations, etc. Hence, installations of SVC have been suggested in this paper to achieve appreciable damping of system oscillations. However, the performance of SVC highly depends upon its parameters, suitable location, and sizes in the power network. In order to find the solution, this problem is formulated as a multi-objective function. Then, MOPSO is used to find the best answers. In this paper, two objectives are considered to improve both the transient stability of the system and the SVC investment cost. The proposed method was tested on the 10-machine 39-busbar New England test system. The results of the nonlinear simulation show that the optimum sizing, siting, and parameter setting of SVC can improve greatly the transient stability of the multi-machine power system. [ABSTRACT FROM PUBLISHER]

Highlights: [•] A new method called the CE approach is used for location and setting of FACTS. [•] To enhance the convergence speed a modification of the CE approach is proposed. [•] The Bernoulli distribution is used because the locations are discrete variables. [•] The performance of the CE algorithm is compared with GA and sensitivity analysis. [ABSTRACT FROM AUTHOR]

There are relatively few literatures about Flexible AC Transmission Systems (FACTS) in reliability aspects, particularly in composite system reliability evaluation. Reliability of the power system could be studied by some indices that help to compare power system under different conditions from reliability point of view. The actual benefits of the FACTS can be quantitatively estimated using suitable models and techniques. Corrective control as an alternative for the system reinforcement is proposed in this paper as a suitable way to ease the challenges related to building new transmission lines or reconstruction of power grid. Static Var Compensator (SVC) as a member of FACTS family has been used as corrective control. A test case with three scenarios is considered for comparing the effect of SVC on the reliability of the power system. It will be seen that the correct SVC replacement has a great influence on the reliability indices of power grid and losses could be diminished. [ABSTRACT FROM AUTHOR]

Highlights: [•] The effect of Static Var Compensator (SVC) connected in transmission line on adaptive distance protection is studied. [•] The SVC is connected at three locations in transmission line. [•] Measured impedances by the relay with and without SVC is determined. [•] SVC connected at mid-point affects seriously on the characteristics of relay. [•] Discrete Fourier Transform (DFT) is used to estimate the phasors of the voltage and current at the relaying bus during fault. [ABSTRACT FROM AUTHOR]

In this paper, the multi-machine power system is simulated and in addition, VURPSO optimization algorithm is used to optimize the parameters of the simultaneous controllers of the Static Var Compensator (SVC) and power system stabilizer (PSS) to increase the power system stability. By SVC, the transmittable power in the steady state can be increased and the voltage profile can be controlled along the line. The main role of the PSS is to damp the generator oscillations controlling its stimulation by the use of auxiliary supplementary signals. If it is assumed that a three phase short circuit fault with the ground has occurred in a four-machine power system, SVC and PSS simultaneous controllers are used to damp the oscillations and stabilize the system. [ABSTRACT FROM AUTHOR]

This paper presents an improved Teaching-Learning-Based Optimization (TLBO) for optimal tuning of power system stabilizers (PSSs) and static VAR compensator (SVC)-based controllers. The original TLBO is characterized by easy implementation and is mainly free of control parameters. Unfortunately, TLBO may suffer from population diversity losses in some cases, leading to local optimum and premature convergence. In this study, three approaches are considered for improving the original TLBO (i) randomness improvement, (ii) three new mutation strategies (iii) hyperchaotic perturbation strategy. In the first approach, all random numbers in the original TLBO are substituted by the hyperchaotic map sequence to boost exploration capability. In the second approach, three mutations are carried out to explore a new promising search space. The obtained solution is further improved in the third strategy by implementing a new perturbation equation. The proposed HTLBO was evaluated with 26 test functions. The obtained results show that HTLBO outperforms the TBLO algorithm and some state-of-the-art algorithms in robustness and accuracy in almost all experiments. Moreover, the efficacy of the proposed HTLBO is justified by involving it in the power system stability problem. The results consist of the Integral of Absolute Error (ITAE) and eigenvalue analysis of electromechanical modes demonstrate the superiority and the potential of the proposed HTLBO based PSSs and SVC controllers over a wide range of operating conditions. Besides, the advantage of the proposed coordination design controllers was confirmed by comparing them to PSSs and SVC tuned individually. [ABSTRACT FROM AUTHOR]