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This paper proposes a novel methodology to improve stability in a transmission system under critical conditions of operation when additional loads that take the system to the verge of stability are placed in weak bus bars according to the fast voltage stability index (FVSI). This paper employs the Newton–Raphson method to calculate power flows accurately and, based on that information, correctly calculate the FVSI for every transmission line. First, the weakest transmission line is identified by considering N − 1 contingencies for the disconnection of transmission lines, and then all weak nodes associated with this transmission line are identified. Following this, critical scenarios generated by stochastically placed loads that will take the system to the verge of instability will be placed on the identified weak nodes. Then, the methodology will optimally size and place a single static VAR compensator SVC in the system to take the transmission system to the conditions before the additional loads are connected. Finally, the methodology will be validated by testing the system for critical contingencies when any transmission line associated with the weak nodes is disconnected. As a result, this paper's methodology found a single SVC that will improve the system's stability and voltage profiles to similar values when the additional loads are not connected and even before contingencies occur. The methodology is validated on three transmission systems: IEEE 14, 30, and 118 bus bars. [ABSTRACT FROM AUTHOR]

The paper presents a ground fault location algorithm (GFLA) in double‐circuit transmission lines (DCTL) with a T‐off connection to an industrial microgrid (IMG) containing electric arc furnaces (EAF), renewable distributed generations (RDG), and static VAR compensator (SVC). The design presented utilizes the information on the current and voltage phasors of one side of the transmission lines (TL) during the fault period, and there is no need for the availability of information on the type of faulty phase(s) and even the faulty section. To find the exact location of the fault in this design, the voltage phasor equations governing the fault point in positive, negative, and zero‐sequence (PNZS) domains, the zero‐sequence current (ZSC) equation of the fault point, and the boundary condition equation of the fault point have been used. The simulation system is implemented in Simulink/MATLAB using accurate modelling of all network components. The algorithm has been tested and evaluated in different fault conditions, including various locations, phase types, phase‐to‐ground connection resistance, occurrence time, and microgrid (MG) operation modes. The successful results of various tests of the proposed design as well as the analysis of various sensitivities confirm the satisfying performance of the suggested algorithm. [ABSTRACT FROM AUTHOR]

An electrical power system (EPS) is subject to unexpected events that might cause the outage of elements such as transformers, generators, and transmission lines. For this reason, the EPS should be able to withstand the failure of one of these elements without changing its operational characteristics; this operativity functionality is called N − 1 contingency. This paper proposes a methodology for the optimal location and sizing of a parallel static Var compensator (SVC) in an EPS to reestablish the stability conditions of the system before N − 1 contingencies take place. The system's stability is analyzed using the fast voltage stability index (FVSI) criterion, and the optimal SVC is determined by also considering the lowest possible cost. This research considers N − 1 contingencies involving the disconnection of transmission lines. Then, the methodology analyzes every scenario in which a transmission line is disconnected. For every one of them, the algorithm finds the weakest transmission line by comparing FVSI values (the higher the FVSI, the closer the transmission line is to instability); afterward, when the weakest line is selected, by brute force, an SVC with values of 5 Mvar to 100 Mvars in steps of 5 Mvar is applied to the sending bus bar of this transmission line. Then, the SVC value capable of reestablishing each line's FVSI to its pre-contingency value while also reestablishing each bus-bar's voltage profile and having the lowest cost is selected as the optimal solution. The proposed methodology was tested on IEEE 14, 30, and 118 bus bars as case studies and was capable of reestablishing the FVSI in each contingency to its value prior to the outage, which indicates that the algorithm performs with 100% accuracy. Additionally, voltage profiles were also reestablished to their pre-contingency values, and in some cases, they were even higher than the original values. Finally, these results were achieved with a single solution for a unique SVC located in one bus bar that is capable of reestablishing operational conditions under all possible contingency scenarios. [ABSTRACT FROM AUTHOR]

This article reports a relay algorithm based protection of static var compensator (SVC) based compensated transmission line utilizing artificial neural networks (ANN). The sequentially involved four artificial neural networks (ANNs) are used. The first ANN detects fault and the second ANN classifies it as either a ground or a phase fault. The faulted phases are then detected using ground fault ANN or phase fault ANN, depending on the situation. A transmission line (100 km, 230 kV, 50Hz) is simulated with SVC at the midpoint using a sampling frequency of 1 kHz in PSCAD/EMTDC. The sequence current ratios are used in fast protection algorithm with 100% accuracy in 4 milliseconds and identify them as phase or ground faults in 8 milliseconds. Finally, the identification of the faulted phase/phases requires just 13 milliseconds. Further, the number of thyristor-switched capacitors (TSC) in SVC depends on several factors such as thyristor valve, reactive power output, and electrical network type. However, the effect of the number of TSCs on the SVC reliability and criticality is not found in the existing literature. The reliability of SVC is increased is reported in this work by varying the number of TSC branches. The observations found increase of 15.47% in the SVC reliability by increasing TSC branches from one to three. In this way, the number of TSC branches in SVC can be optimized to increase the system's reliability with minimum cost. [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 proposes a nonlinear coordinated controller for a single machine infinite bus power system. The later consists of a synchronous generator connected to the infinite bus via transmission lines, which are equipped with a static var compensator. The proposed control strategy aims to control simultaneously the excitation system of the synchronous generator and the static var compensator in order to improve transient stability and voltage regulation. The input output linearization theory and pole-assignment technique are employed to design the nonlinear controller. The controller's performance in single machine infinite bus power system is then examined using simulation studies when the studied power system is subjected to three-phase short circuit with a 100ms duration. The results validate the efficiency of the proposed controller, which is based mainly on the good regulation of the static var compensator voltage with removing the static error after fault elimination. [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]

Flexible AC Transmission Systems (FACTS) present a decision to issue trouble relief for over-extended electric power transmission lines as a result of optimal power flow (OPF) by controlling. To keep away from conventional impacts among a few gadgets placed in a similar grid, an organized control is fundamental. To defeat the issues which happen in optimal power flow to actualize the cross difference progression and coordination inspects strategy, a supervisory controller giving difference progression power flow with numerous destinations is acquired for avoiding congestion, it gives secure transmission and farthest point dynamic power misfortunes. There is no information on gadgets that have been defined in this systematic control of Thyristor controlled series capacitor (TCSC) and Thyristor controlled phase shifting Transformer (TCPST), static VAR compensator (SVC), all of these compensators providing efficient improvements and situations are described. Different optimization techniques are used as a part of the character to deal with the problem of OPF. In some experimental works, the upgrade method is used for finding out all of the fuel costs or the environmental pollution that occurs during the generation of energy. However, in some further research actions, FACTS controlled devices are used to develop the flow of electricity without considering the cost of electricity generation. While a specific end goal of using the FACTS control devices is to help optimize the congestion in the power system, it also aggregates the power loss which enhances the load capacity of the structure. The FACTS and its practical limitations are executed into the IEEE 30-bus test power framework and customized utilizing the Cross Difference Progression and Coordination Examining (CDP&CE) algorithm with MATLAB and the outcomes are given. Here, IoT-based data analytics is defined as the process, which is used to examine varied data from the bus system using Principal Component Analysis (PCA) method, the results of which help to take the necessary decisions. The effect of FACTS gadgets is implemented on standard IEEE-30 transmission framework with supporting numerical outcomes by utilizing MATLAB Software. [ABSTRACT FROM AUTHOR]

This paper presents an application of multiobjective cuckoo search (MOCS) algorithm for reduction in transmission line losses by placing static VAR compensator (SVC) at an optimal location. MOCS algorithm is an extension of the infamous cuckoo search algorithm. The multiobjective optimizations considered in this paper include active power loss and reactive power loss, active power loss and investment cost of SVC. The Pareto-optimal solution which is obtained by using the Pareto-optimal method gives the solution to the multiobjective problem. The fuzzy logic approach is used to obtain best trade-off solutions from the Pareto-optimal solution. A standard IEEE 30 bus test system is considered for testing the efficacy of the proposed methodology. The results show that installation of SVC and application of MOCS algorithm is effective in power loss reduction. [ABSTRACT FROM AUTHOR]

This paper proposes a decentralized control based on static var compensator (SVC) devices to improve the frequency control of high voltage transmission systems. For a realistic structure preserving power system with voltage dependent loads, we propose a sufficient condition based on a strict Lyapunov energy function, which is utilized to design a nonlinear adaptive SVC controller. This controller only requires local bus measures and parameters. Furthermore, we also present an SVC with a conventional frequency droop controller. The performance of the two considered SVC control systems are evaluated on the well known IEEE New England 39-bus 10-machine power system and compared with conventional SVC controllers. [ABSTRACT FROM AUTHOR]

DC ice melting is an effective technical method against ice disaster on transmission lines. To satisfy the demand for simultaneous de-icing and reactive power compensation for substations, this paper proposed a large-capacity low-cost DC deicer with reactive power compensation, which is mainly composed of rectifier transformer, Static Var Generator (SVG) and diode rectifier. In the proposed topology, SVG and diode rectifier share the rectifier transformer, but rectifier transformer capacity is not increased compared with a single deicer. This paper firstly presents the proposed topology and analyzes its advantages. Then, the rectifier transformer design is introduced, and the SVG control strategy is presented. Simulation results for the proposed device are presented, and an engineering devices with a capacity of 21.8 MVA developed for the 220 kV Fuchong substation is described. The simulation and application results indicate that the proposed devices work well. [ABSTRACT FROM AUTHOR]

• Computational modeling to evaluate the LOE protection of synchronous generators connected to a transmission line with static var compensator (SVC). • Comparative of traditional LOE protection of with a proposed LOE protection method based on a multilayer perceptron-type artificial neural network (ANN). • Show the effectiveness of the proposed ANN LOE protection to reach faster actuation time than the traditional LOE protection. Flexible Alternating Current Transmission Systems (FACTS) connected to Transmission Lines (TLs) make systems more flexible, and optimize their operational capacity. Despite improvements in TL operational aspects, added FACTS can modify the amplitude, voltage, and current angles of the system wherein they are inserted and consequently the measured impedance, which can affect synchronous machine protections that are based on this feature. Firstly, this paper presents a set of computational simulations to evaluate possible changes in the synchronous machine protection connected to a TL with Static Var Compensator (SVC). Finally, is this context the traditional loss of excitation (LOE) protection is comparing with a proposed approach based on the use of a multilayer perceptron-type Artificial Neural Network (ANN). The simulation results show the effectiveness and robustness of the proposed ANN LOE protection to reach faster actuation time than the traditional LOE protection. [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]

This paper discusses reactive power compensators from the point of stored energy in the capacitor, and proposes a single-phase full-bridge configuration of semiconductor switches to be used with reduced equipped capacitance for reactive power compensation. By applying this concept to shunt-type static var compensator, a static synchronous compensator can be achieved with reduced-sized capacitor. Additionally, the switching loss can be reduced due to its distinctive capacitor voltage waveform, which swings at the double of the line frequency. Modulation technique and capacitor voltage control method based on the reduced capacitance and high-voltage ripple in the capacitor are proposed. The concept and control method were confirmed with small-scale experiments. [ABSTRACT FROM AUTHOR]

• The proposed protection strategy enhances the stability and reliability of power systems by. • Precise discrimination between transient and permanent SLG faults. • Fast and precise diagnosis of the successful reclosing time in a case of the transient SLG fault. • Significant reduction in the dead time in a case of the transient SLG fault. • Being efficient even in noise exposure situations and not dependent on the fault location or threshold values. Opportune detection of transient faults and restoration of the faulty phase in the least possible time plays a key role in improving the stability of high voltage transmission lines (HVTLs). This paper presents a novel four-step strategy for the protection of HVTLs so that the stability and reliability of power systems are enhanced. Firstly, the cumulative sum (CUSUM) algorithm is used to quickly detect the transient and determine the faulty phase. In the second step, the settings of the static var compensator (SVC) are changed to reduce the reclosing dead time as much as possible. Afterward, the transient or permanent type of the fault is identified based on the proposed principal component analysis-support vector machine (PCA-SVM) algorithm. In the fourth step, if a transient fault is recognized, the successful single-phase reclosing time is identified by the PCA-SVM and the reclosing command is issued to high voltage circuit breakers (HVCBs). Simulation results obtained by using EMTP-RV and MATLAB for a sample 400 kV power system illustrate that the proposed protection strategy can increase the reliability of the power system via reduction of the dead time, correct detection of transient faults from permanent ones, and accurate detection of the reclosing time. [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]

• Static var compensator causes a delay in operation of loss of excitation protection. • Delay also depends on the power dispatch and the severity of the loss of excitation. • Static var compensator causes under-reach of commercial loss of excitation relay. • Presence of static var compensator causes a displacement of impedance trajectory. • Positive offset relay adjustment seems to be more adequate than negative adjustment. The static var compensator (SVC) is one of the devices that has been widely used for reactive compensation to improve the capacity and flexibility of power transfer in the electrical power system. However, the SVC changes the voltages and currents of the power network to which it is connected. Consequently, the measured impedance can be changed and affect protection relays operation based on this characteristic. Several papers have been published about the SVC effects on distance protection applied in transmission lines (TL). However, it is not widely known the impact of SVC on the transient behavior of generators, such as protection against loss of excitation (LOE) in synchronous machines connected to TL with SVC. In this sense, based on the modeling of a test electrical power system in the PSCAD/EMTDC simulation environment, the assessment of the effects of SVC on the behavior of the ANSI 40 protection function for the conditions of the total LOE and partial LOE since these events can cause the synchronous machine to operate in conditions above the rated ones. In addition, this paper presents a testbed that allows performing secondary tests in physical relays when simulated signals are applied to perform protection studies in the presence of SVC in power systems. [ABSTRACT FROM AUTHOR]

Static var compensator (SVC) devices have been extensively utilized in modern substations to achieve high flexibility and wide tolerance to load variation. However, due to frequent switching of the thyristors in a static var compensator, large amounts of electromagnetic interference (EMI) are being generated, which may cause malfunction of the SVC or unaccepted response of victim devices positioned nearby. In this paper, an advanced acquisition system was established to implement onsite measurements in order to obtain the EMI data. A digital calibration technique for the antenna was applied to trace back the actual electromagnetic emissions. The radiated and conducted EMI data are comparatively analyzed to present detailed and useful information of the EMI levels. According to the configuration of an SVC and the dynamic performance of the random load, an equivalent model was established to simulate and predict the conducted EMI levels. Based on onsite measurements as well as theoretical analysis, pertinent immunity measures were put forward to reduce coupling impacts on the electronic units of the secondary side. [ABSTRACT FROM PUBLISHER]

Motivated by the development of power semiconductor technologies, flexible ac transmission systems (FACTS) devices and their penetration in the field of electrical power systems, an educational challenge in complementing theoretical knowledge with practical experience is recognized. In this paper, the design and implementation of a lab-scale hardware and software setup is presented. Three small-scale devices, including a static VAr compensator (SVC) unit, a transmission line model, and a substation, are developed. The SVC unit is validated by obtaining its operating characteristic. The lab setup is presented as a platform to carry out different experiments related to the SVC operation. Safety considerations in the design are discussed. Steady-state and dynamic analysis are presented showing the consistency between theory and practice. The potential use of small SVC units on low-voltage distributed generation schemes is discussed. [ABSTRACT FROM AUTHOR]

Due to the growth of electricity demands and transactions in power markets, existing power networks need to be enhanced in order to increase their loadability. The problem of determining the best locations for network reinforcement can be formulated as a mixed discrete-continuous nonlinear optimization problem (MDCP). The complexity of the problem makes extensive simulations necessary and the computational requirement is high. An ordinal optimization (OO) technique is proposed in this paper to solve the MDCP involving two types of flexible ac transmission systems (FACTS) devices, namely static var compensator (SVC) and thyristor controlled series compensator (TCSC), for system loadability enhancement. In this approach, crude models are proposed to cope with the complexity of the problem and speed up the simulations with high alignment confidence. Test results based on a practical power system confirm that the proposed models permit the use of OO-based approach for finding good enough solutions with less computational efforts. [ABSTRACT FROM AUTHOR]

In this research, an alternative methodology is proposed for the location of Static VAR Compensators (SVC) in power systems, considering the reconfiguration of reactive power flows through the optimal switching of the transmission stage, which resembles the contingency restriction N-1 usually considered in transmission expansion planning. Based on this methodology, the contingency index was determined, which made it possible to determine which is the contingency that generates the greatest voltage degradation in the system. For the quantification of reactive flows, optimal AC power flows were used, which minimize the operating costs of the power system subject to transmission line switching restrictions, line charge-ability, voltages and node angles. To determine the node in which the compensation should be placed, the contingency index criterion was used, verifying the voltage profile in the nodes. The proposed methodology was tested in the IEEE test systems of 9, 14 nodes and large-scale systems of 200, 500 and 2000 bus-bars; to verify that the proposed methodology is adequate, the stability of the EPS was verified. Finally, the model allows satisfactorily to determine the node in which the SVC is implemented and its compensation value. [ABSTRACT FROM AUTHOR]

In this paper, an analytical framework for minimizing losses and harmonics is presented for the cascaded-type-based multilevel static synchronous compensator (STATCOM) with "square-wave control." The focus lays on low losses, low-voltage total harmonic distortion (THD), and low dc voltage ripple. All of the system parameters are studied, including buffer reactance, dc capacitance, transformer ratio, and transformer leakage inductance. The equivalent capacitance concept is used to represent the complex structure of the multilevel converter. It enables studies of the internal STATCOM resonances which have a significant influence on triplen harmonics and losses. The interactions between system parameter are investigated and analytical formulae for optimal parameters are derived. Detailed PSCAD digital simulations are used to confirm the analytical formulae. The summarized design steps are offered that are recommended to obtain optimum STATCOM system parameters. [ABSTRACT FROM AUTHOR]

• A new reintegration-driven ICI framework, called R-ICI, is proposed. • The proposed R-ICI model improves frequency stability of islands using ESSs. • Transient voltage stability of islands is improved using ESSs and SVCs. • The interaction between frequency and voltage is considered by a linear IFR model. • An active/reactive charging and discharging scheme is introduced for ESSs. In this paper, a reintegration-based multi-objective intentional controlled islanding (ICI) model is proposed to enhance resiliency of electrical power systems under catastrophic events. This remedial measure plan relies on a mixed-integer linear programming model with two objective functions including reintegration risk and total load shedding value. While ensuring that each island includes only coherent generators, the proposed multi-objective model solves the controlled islanding problem using lexicographic optimization approach. To ease the islands' reintegration, charging reactive power, reliability, capacity, and power flow disruption of transmission lines are considered in the model. After implementation of controlled islanding, each resulted island may face temporary active/reactive load-generation imbalance, which may put the islands at the risk of frequency instability, transient voltage instability or a combination of both. The proposed model reduces these risks by modeling energy storage systems (ESSs) and static VAR compensators (SVCs) as fast corrective control actions. In addition to modeling voltage dependent loads in the controlled islanding problem, a linear island frequency response (IFR) model is proposed for frequency stability assessment. The test results of the proposed ICI model on the IEEE 39-bus and IEEE 118-bus test systems demonstrate its performance. [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 presents a secure tri-level planner-disaster-risk-averse-replanner model for resilience-oriented investment planning in integrated electric power and natural gas networks, where generation units, static VAr compensators, wind farms, transmission lines, and gas pipelines are considered as investment candidates. Additionally, emergency demand response is utilized to enhance the resilience of the integrated energy system. The proposed model is capable of controlling the resilience of the integrated energy system through a specific parameter designated as the resilience indicator and solved by a sequential three-level algorithm. The first-level problem finds the optimal investment plan before any disruptive event. Given the optimal investment plan obtained by solving the first-level problem, the second-level problem finds worst-case disruptive events affecting different components in the integrated energy system, where the vulnerability of these components is evaluated, aiming at considering a multi-disaster and multi-zone resilience model. Given a specific resilience budget, which limits replanning costs, the third-level problem maximizes the resilience of the integrated network by replanning investment decisions of the first-level problem, aiming at compensating for the unserved demand caused by the second-level problem. Case studies justify the suitability of the proposed model to enhance the resilience of the integrated system under different disastrous events. • A secure tri-level risk-averse expansion co-planning model is introduced. • The investment/disaster decisions are made for all energy system components. • A new resilience indicator, called resilience budget, is presented. • Several here-and-now and wait-to-see investment/operation decisions are considered. • Various techno-economic constraints are modeled to ensure the security of the integrated energy system. [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]

The central Tibet AC interconnection project (CTAIP), which connects the Tibet power grid and the Sichuan power grid through a long distance transmission line of more than 1400 km, has a significant problem of voltage regulation. In order to improve the voltage regulation performance, six sets of ±60 Mvar static VAR compensators (SVC) were installed in the CTAIP. However, the SVCs may lead to electromagnetic oscillation below 50 Hz while improving voltage regulation capability. In this paper, the electromagnetic oscillation modes and the sensitivity of control parameters of SVC are analyzed. Then, the characteristics and influencing factors of the oscillation are discussed. It was found that there is an inherent electromagnetic oscillation mode below 50 Hz in the ultra-long distance transmission system. The employ of SVCs weaken the damping of this mode. Large proportional gain and integral gain (PI) parameters of SVCs can improve the voltage regulation performance, but weaken the electromagnetic oscillation mode damping. Therefore, a suppression method based on SVC PI parameters optimization is proposed to damp the oscillation. The essential of this method is to use the rising time of voltage response and setting time of SVCs as performance indicators of voltage regulation, and take the damping level of the electromagnetic oscillation mode as the performance index of SVC electromagnetic oscillation suppression ability. Combining the two indicators to form a comprehensive optimization index function, an intelligent optimization algorithm is applied. The process of SVC parameter optimization and the steps of multi-SVC parameter optimization in large power grids is proposed. Finally, PSCAD and real-time digital simulation (RTDS) simulation results verified the correctness of the proposed method. The optimization strategy was applied to CTAIP. The artificial grounding short circuit experimental results proved the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]