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• Recursive least squares and generalized regression neural network are used to build a real-time dynamic system model for adaptive control. • A static var compensator additional dual-channel damping controller structure is proposed for the dominant mode of low-frequency oscillation. • Static var compensator additional damping controller parameters tuning problem converted Markov decision process and a soft actor-critic algorithm is also introduced to solve the Markov decision process. As the access rate of wind energy in a power system has significantly increased, stabilizing the power system has become challenging. Among these challenges, low-frequency oscillation is one of the most harmful problems, effectively resolved by adding a damping controller according to the relevant properties of the low-frequency oscillation. However, the controller often fails to adapt to the constantly changing wind energy system owing to the lack of a targeted dynamic change strategy. Thus, to address this issue, an adaptive stabilization strategy that uses a static var compensator with an additional damping controller structure is proposed. Specifically, the entire power system is equivalently represented as a generalized regression neural network, with a deep reinforcement learning algorithm called soft actor-critic introduced to train the agent based on the generalized regression neural network model. After the training process, the agent can provide additional efficient static var compensator damping controller parameters under different operating conditions, vastly improving the system stability. Simulation results verify the improved performance using the proposed strategy compared to other optimization methods, regardless of whether the low-frequency oscillations were suppressed in the time or frequency domains. [ABSTRACT FROM AUTHOR]

Highlights • This paper proposes two controlling methods for SVC in smart grid with connected EV charger. • SMC, ASRFC with a HVC are separately applied in the grid. • This paper presents usage of proposed methods for decreasing size of capacitor and value of apparent power loss. • The proposed scheme is validated through computer simulations of a 22.9-kV grid. Abstract Electric Vehicles (EVs) play a pivotal role in reducing the emissions of greenhouse gases in the world. Currently demand for EVs has abruptly increased for transportation and other applications. Using more EVs causes an increasing load on the power system. Random EV charging yields voltage distortion, which results in an unbalanced grid. In a distributed system, the connection of EVs to the grid may diminish the power factor, which increases the apparent power loss. The Static VAR Compensator (SVC), which is a FACTS device, is applied to the power system to compensate the voltage distortions and apparent power loss. In this paper, two controlling methods are contemplated and tested in a SVC to reduce the apparent power loss and minimize the capacitor size of the SVC in comparison with the conventional control method in a SVC. Proposed methods are also compared with the conventional control method used for SVC. The Slide Mode Controller (SMC) and Asymmetric Synchronous Reference Frame Controller (ASRFC) with a Harmonic Voltage Compensator (HVC) are separately applied in the grid. This paper presents usage of SMC and ASRFC methods for decreasing size of capacitor and value of apparent power loss through computer simulations of a 22.9-kV grid. With application of new controllers, apparent power loss of grid will be reduced as compared with conventional method of SVC controller. Moreover, the size of SVC capacitor can also be reduced. [ABSTRACT FROM AUTHOR]

The use of a static var compensator (SVC) as a component of flexible alternating current transmission system (FACTS) devices to control power systems has been investigated for decades. Its aim is to regulate the system voltage and improve the stability and loadability of power systems. A typical assumption in such a system is that the parameters of the controlled system are known accurately, which is rarely satisfied in practice. This paper explores the development of a simple but effective controller for a single-machine infinite-bus power system with SVC subjected to both matched and mismatched disturbances where the controller derivation is based on the assumption that all parameters used in the system modeling are unknown , but bounded in size. The research in this paper illustrates how an indirect robust control can be incorporated with a modified disturbance observer-based feedforward term to attenuate the influence of parameter variations and disturbances from the outputs of the system. Simulation results are presented to confirm the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

• Improving the voltage in a wind farm by a self-corrective static VAR compensator. • Considering the steady-state and transient modes under harsh faults in analysis. • Enhancing the system performance by employing an optimized Battery Energy Storage. • Reporting the results in different cases, with or without the mentioned equipment. Maintaining synchronism and voltage stability, especially in the presence of wind farms, has a crucial role in confirming the reliability requirements of the power grid, as the natural fluctuations of wind speed result in intermittency and uncontrollability of power generation. To this end, an optimized Battery Energy Storage System (BESS) was suggested to make an equilibrium between the generation and consumption in wind farms under harsh conditions. Additionally, the instability of wind farms is very likely after transmission line faults occur. To overcome this problem, in this paper, the impact of a constant capacitor bank, connected in parallel with the wind generators, is investigated. Also, a novel self-corrective Static Volt-ampere reactive Compensator (SVC) is proposed to overcome the variations of voltage and damp the reactive power oscillations after occurring the faults. The proposed SVC compares the network voltage profile as the reference voltage with the voltage deviations in a control block diagram. For this purpose, three similar wind farms of Permanent Magnet Synchronous Generator (PMSG) type are considered in a wind park. The simulation case studies are performed in Matlab/Simulink under different conditions of transient and steady-state voltage stabilities in the presence of proposed BESS including, only capacitor bank (without self-corrective SVC), and with self-corrective SVC. The results authenticate the ability of the proposed SVC strategy to correct the voltage deviations, and voltage stability improvement of the under study system. [ABSTRACT FROM AUTHOR]

Presence of shunt FACTS (Flexible Alternating Current Transmission System) device significantly affect the performance of protection system and may create security and reliability issues. This paper introduces a novel approach for zone identification in transmission line employing shunt FACTS devices such as Static Var Compensator (SVC) and Static Synchronous Compensator (STATCOM). The technique depends on the modified apparent impedance seen by the impedance relay for all possible operating conditions. In this technique the Support Vector Machine (SVM) is used for discriminating faulty zone (zone 1 or zone 2). In addition an optimization technique viz. Genetic Algorithm (GA) is used to optimize SVM parameters. A typical 230 kV system was simulated in PSCAD/EMTP software and the results show that the proposed scheme is secure, accurate and reliable under the wide variation in power system parameters like load angle, fault resistance, fault location, inception angle and compensation level. [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 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]

• A modified minimum switch count magnetic energy recovery switch (MERS) topology has been proposed as a shunt static VAr compensator (SVC-MERS). • The conduction loss of the switch is reduced due to the minimum switch count and thus promises a high-efficiency compensator. • An equivalent harmonic model using mathematical equations has been developed by introducing switching functions for performance analysis of the proposed compensator. • A suitable ratio of resonant angular frequency to line angular frequency has been chosen to select the optimum L and C parameter of MERS unit for low harmonic injection. In this paper, a minimum switch count modified magnetic energy recovery switch (MERS) topology has been proposed as a shunt static VAr compensator (SVC-MERS). Whereas, the existing scheme uses four active switches for the same purpose. Thus, conduction loss of the switch is reduced in the proposed scheme due to the minimum switch count and thus promises a high-efficiency compensator. Moreover, a coupling inductor (L) and a capacitor (C) are used in the proposed scheme for reactive energy storing and exchanging. Improper selection of L and C may instigate harmonic resonance. To examine its impact on modified MERS performance, an equivalent harmonic model using mathematical equations has been developed by introducing switching functions. The characteristics analysis of the proposed modified MERS has been done by using this harmonic model. Based on the above analysis a suitable ratio (S) of resonant angular frequency to line angular frequency and corresponding optimum L , C parameters have been selected for low harmonic injection. The key features of this proposed scheme are low current total harmonic distortion (THD), lesser switching losses, reduced cost, and low voltage rating of the switch as compared to the existing MERS scheme. To verify the proposed concept simulation has been carried out using a 6 kVA rating inductive load in MATLAB Simulink environment. The both analytical and simulation results confirm that the proposed reduced switch count compensator model with optimum L = 30 m H and C = 150 μ F can be used efficiently for power quality improvement in a low voltage grid. \ [ABSTRACT FROM AUTHOR]

Highlights: [•] Different components of TCR–FC type SVC are introduced. [•] Using Markov process, a reliability Markov model for TCR–FC type SVC is obtained. [•] An equivalent three-state model for TCR–FC type SVC is proposed. [•] A sensitivity analysis for the availability of the equivalent model is carried out. [Copyright &y& Elsevier]

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]

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]

• Categorization of FACTS devices as HSRF, MSRF, and LSRC devices by response speed. • Mathematical modelling for the coordination of MCR with SVC and FC. • Control strategy to enhance the compensation capacity of high response speed SVC. • Control strategy to enhance the low compensation speed of MCR and FC. • The proposed strategy is suitable for full range of compensation for power system. Traditional devices in flexible AC transmission system (FACTS) like magnetically controllable reactor (MCR), and fixed capacitors (FC) are less expensive and have medium or low response speed that can only provide excessive inductive or capacitive reactive power compensation. However, modern FACTS devices like static var compensators (SVC) are expensive and have high response speed which can provide limited inductive to capacitive reactive power compensation as compared to the MCR and FC. In addition, if there is no proper coordination between these traditional and modern FACTS devices they absorb each other's reactive power and may results in the decrease of compensation margin and wastage of the resources. Therefore, to make an effective use of these categories of FACTS devices in the existing power system, the coordination control that shares high speed and excessive compensation ability without wastage of resources is essential. This paper presents coordinated control of multi-FACTS devices to provide efficient reactive power compensation based voltage regulation. At first, the characteristics of various categorical FACTS devices are presented in relation to response speed by incorporating high speed response FACTS (HSRF), medium speed response FACTS (MSRF) and low speed response compensator (LSRC). Finally, the MCR with SVC and MCR with FC coordination controls have been developed sequentially with minimal efforts of compatibility issues and compensation speed while ensuring an increase in the reactive power reserves for the SVC. The simulation is carried out on PSCAD/EMTDC to test the coordination control efficiency of several three phase multi-FACTS devices with series and parallel configurations and validated on a modified IEEE 30 bus power system. The results show that multi-FACTS coordination control increases the SVC reserves and is promising in providing voltage regulation for the power system under various scenarios. [ABSTRACT FROM AUTHOR]

Abstract: Static VAr Compensators (SVCs) can balance the phase currents of three-wire three-phase loads and compensate their reactive power. Thus, the SVC-load set becomes a balanced load with any desired power factor. This paper proposes a method to use SVCs with four-wire three-phase loads which still perform those functions: load balancing and reactive power compensation. As a result, any load connected to a three-(or-four-)wire three-phase system can be transformed into a balanced load with unity power factor, even if it is a single-phase load. Other properties that appear in particular cases are also analyzed. [Copyright &y& Elsevier]

• Basic flicker effect mitigation techniques description. • SVC control system adjusted for industrial applications, especially for industrial system with EAF. • Study and comparison of different signal processing techniques od input SVC controller signals. • Using of field measured data for testing proposed techniques by laboratory scale SVC system. • Evaluation flicker effect for proposed techniques and comparison with results of previous works. The work focuses on the possibilities of improving the Static Var Compensator (SVC) control system for more effective reduction of the flicker effect. The studied SVC control system consists of an open control loop, which provides a fast response to dynamic changes in Electric Arc Furnace (EAF) power, and a closed control loop, which provides precise control to ensure the required value of the power factor in the Point of Common Coupling (PCC). The improvement consists in the use of alternative techniques for signal processing of input control variables. The first alternative technique is the use of Second Order Generalized Integrator (SOGI), which is also used in other related applications. The second alternative technique is to use the flicker weighting function, which corresponds to the function used to measure the flicker effect using a standardized flicker meter. Experimental laboratory equipment and theoretical model in frequency domain was used to verify the properties of the proposed techniques. To simulate the dynamic behavior of EAF, data measured from real operation were used, which were implemented into an experiment using VSC. Analysis of measured data and data obtained from laboratory apparatus shows high similarity. The experiments were carried out in several variants to reflect the differences in the various stages of the production process in the EAF. For all variants, the resulting flicker effect was evaluated and the individual techniques were compared with each other and with the results of other works. [ABSTRACT FROM AUTHOR]

• A novel single-end protection scheme for the compensated transmission line based on traveling waves. • Impact of SVC on traveling waves passing through a connection point of SVC. • Evaluates the effects of generated transients during faults resulted from SVC switching. • This article employed the game theory to discriminate the detected traveling waves. This paper proposes a novel single-end protection scheme for the compensated transmission line based on traveling waves and Game Theory. Initially, this study investigates the effects of Static VAR Compensator (SVC) on Traveling Waves (TW) passing through SVC location. Subsequently, it evaluates the impacts of SVC switching on conventional protections based on traveling wave theory. Following that, a single-end method to locate faults on compensated transmission lines with SVC is presented in this study. Moreover, Game theory was utilized to discriminate extracted TWs in this paper. In order to investigate the sensitivity of the proposed scheme regarding the extraction techniques of TW, two techniques, namely Mathematical Morphology Filter (MMF) and Discrete Wavelet Transform (DWT) have been used to process the signals in this study. The simulation studies using PSCAD software indicate that the proposed protection scheme is reliable and accurate for all possible types of faults on transmission lines with and without SVC. In addition, the proposed technique presents noise immunity. [ABSTRACT FROM AUTHOR]

• This paper studies the effect of varying wind speed, replacement of Synchronous Generator with DFIG at various locations, and wind penetration with and without PSS, SVC and STATCOM. • The objective function for PSO selected as the real part and damping ratio of eigenvalue. This PSO is used for tuning the control parameter. • The transient and small signal stability carried out by using time domain simulation and eigenvalue analysis. • The effectiveness and robustness of proposed approaches are verified considering IEEE-14 system. In a power system with renewable energy sources, the Low-Frequency Oscillatory (LFO) modes arise due to the intermittent nature of wind power, loading and generating conditions. This is undesirable and results in system instability. If these LFO modes are not controlled, it may lead to a power interruption and results in unstable. The LFO modes are damped by Power System Stabilizers (PSS). However, it causes variation in voltage profile resulting in reduction instability of the system during large disturbances. In such cases, the flexible ac transmission system controllers are required. This paper presents and compares the PSS, Static synchronous Compensator (STATCOM) and Static Var Compensator (SVC) controller by replacing Synchronous Generator (SG) with same rated wind farm and various wind power penetration levels by considering system uncertainties such as wind speed. In this paper, a robust coordinated method is proposed using Particle Swarm Optimization (PSO) for optimizing parameters of controllers of PSS, SVC, and STATCOM. The real part and damping ratio of eigenvalues is the objective function for PSO and is formulated based on the small-signal and transient analysis. Controller locations are determined by the deterministic method, probabilistic method and power flow sensitivity analysis. An eigenvalue analysis approach based on the linearization of a nonlinear system using a state-space model is conducted to analyse the Small Signal Stability performance. Time-domain simulation is carried out for transient stability under large disturbance. The robustness and effectiveness of the proposed approaches for transient and small-signal stability are evaluated on the IEEE-14-bus system. The results reveal that the proposed location and optimized gain parameters for controllers effectively damped the LFOs. It also intensifies the transient capability under extreme disturbances and shows enhancement in system stability. [ABSTRACT FROM AUTHOR]

• This method is only based on the current data in relay location. • The proposed method is completely analytical. • A negative-sequence based approach used to fault location estimation. This paper introduces an accurate fault location algorithm for double-circuit transmission lines compensated by Static Var Compensator (SVC). The proposed algorithm is based on the negative-sequence circuit of the transmission system and it depends only on the current data available from one end of the line. Since only magnitudes of current signals are required, there is no need for data synchronization. The proposed technique uses the COMTRADE fault files available from digital distance relays and it can effectively locate the all types of unbalanced faults, regardless the high fault resistance, effect of mutual coupling and SVC current injection information. As one formula can be used for all types of fault, classification of fault types and phase selection are not required. The shunt capacitances of the line are considered by utilizing the distributed parameters model of the transmission lines. The proposed algorithm is rigorously investigated for various fault scenarios in SVC compensated transmission system. The simulation cases in the MATLAB environment verifies that the proposed scheme has excellent performance. Test results are compared with a conventional fault location technique to illustrate the accuracy of the proposed algorithm. [ABSTRACT FROM AUTHOR]

• A novel expansion planning model for active distribution system with multiple active network managements is proposed. • Optimal load shedding is originally proposed and shows an obvious better stability performance in case study. • A SOCP approach and some linearization means are applied to solve the MINLP model. • A two-stage optimization algorithm is developed and proved to have great ability to solve this problem. • Simulation results based on a modified 37-bus system indicate the technical and economic superiority of the proposed model. In this paper, a new expansion planning model for an active distribution system considering multiple active network management schemes is proposed, where demand management considering the optimal load-shedding direction is innovatively introduced into the planning model. This model optimizes the investment decisions of all the infrastructures as well as the corresponding operational strategies in a coordinated manner. Therefore, the final solution is identified by the optimal type, location and size of the feeders, distributed generators, capacitor banks, static var compensators, voltage regulators, energy storage systems, and transformer substations. To incorporate the optimal load reduction into active network management, the optimal load-shedding direction is first introduced, and an iterative method is developed to compute it. On this basis, the coordination planning model of an active distribution system is established, and the operational strategy of all the active management devices is integrated into the expansion planning problem of an active distribution system. By applying the second-order cone relaxation method, the original mixed-integer nonlinear model is converted into a mixed-integer second-order cone programming model that be efficiently solved. Finally, a two-stage optimization algorithm is proposed to obtain the final solutions. Simulation results based on a 37-bus system and a 122-bus system corroborate the effectiveness of the proposed model. [ABSTRACT FROM AUTHOR]

• Three-phase four-wire loads can be balanced by a Balancing Capacitive Compensator. • Variable load can be balanced by an Adaptive Balancing Capacitive Compensator-ABCC. • A Static Var Compensator type ABCC is a high efficiency solution. • This article presents and validates a new method of sizing an ABCC. Nowadays, there is an increasing development of equipment type Custom Power Devices (CPDs) designed to ensure a high level of electrical power quality at the Point of Common Coupling (PCC). Most of these devices are built as advanced power electronics applications, such as the Switching Power Converters (SPCs) category. However, for a wide range of applications in consumer installations and electricity distribution operators, such as power factor correction, load balancing, voltage regulation, or flicker mitigation, the reactive power compensators based on passive circuit elements, Reactive Power Compensators (RPCs) are successfully used. The most efficient RPCs are those built so that they may adapt to variable regimes, known as Static Var Compensators (SVCs). Two of the usual functions of a SVC, namely power factor improvement and load balancing in a three-phase distribution network, can be achieved simultaneously by using an unbalanced SVC built in the version of Adaptive Balancing Reactive Compensator (ABRC). The paper briefly–outlines the mathematical model and operation of a Balancing Reactive Compensator (BRC) for a three-phase four-wire network. Then, moves on to develop a direct method of sizing based on equations that directly link the susceptances' values of the compensator with the real and imaginary components of load sequence currents. The problem is to determine the weight of these components, meaning their degree of compensation, by requiring only capacitive or null susceptances and avoiding capacitive over-compensation of positive sequence currents. Thus, a particular case of BRC, i.e. a Balancing Capacitive Compensator (BCC) is obtained, which keeps the same functions, but has the advantage of reducing costs by eliminating high-power single-phase coils and by simplifying the compensation control system. The paper also presents the numerical results and the conclusions of a case study on the application of the method, performed using two computational and modeling software tools. Experimental laboratory determinations and modeling under nonsinusoidal conditions complete the analysis. The results demonstrate the correctness of the new method of solving the sizing problem and once again validate the unbalanced capacitive compensation as an efficient method of power factor improvement and load balancing at a PCC belonging to a three-phase four-wire distribution network. [ABSTRACT FROM AUTHOR]

• Reactive power injected by the shunt-FACTS devices prevents the terminal voltage of the alternator. • To detect a loss of excitation, appropriate relay settings has to be set keeping in view the generator parameters and the system loading conditions. • There should be a separate relay in place to deal with the generator's loss of synchronism because the LOE relay might not detect this condition under all operating conditions. Among the different Loss of Excitation (LOE) relaying schemes in practice today, the most famous is the mho relay. During the loss of excitation, the impedance as seen by the relay enters the zones of protection that are set up according to the generator and system specifications. It then generates a trip signal to separate the affected alternator from the system in case the fault persists. Modern-day Power Systems incorporate FACTS devices to deal with certain tasks like voltage regulation, improvement of transient stability, prevention of voltage instability and damping Power oscillation. It has been shown that the reactive power injected by the shunt-FACTS devices prevents the terminal voltage of the alternator from dropping during LOE, which causes a delay in the operation of the LOE relay. Under certain conditions such as the event of partial LOE or during condenser mode of operation of an alternator, the presence of shunt-FACTS devices may lead to under-reach of the relay. This paper analyses the effects that shunt FACTS devices, such as Static VAR Compensators (SVCs) have on the loss of excitation (LOE) protection of an alternator. Simulations were carried out in the MATLAB/Simulink environment to simulate various LOE relay schemes during excitation system failures. The results give us an insight into the advantages and disadvantages of various LOE protection schemes and serve as a reference for selecting a particular scheme for any system. [ABSTRACT FROM AUTHOR]