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This paper proposes a fault current limiting scheme (FCLS) for full-scale wind power generators based on logic bang-bang funnel control (LBFC). Different from the convention methods such as frequency droop control and sliding control, which design the control strategy according to the specific fault currents, LBFC is able to restrict various fault current within acceptable range in the shortest time, and it is robust to system nonlinearities and external disturbances. The control signal of the LBFC is bang-bang with the upper and lower limits of control variables. In the model of full-scale wind power generators connecting with the power grid, LBFC is designed to control the switches of inverter bridges when over-current is detected, and a vector controller is applied during the normal operation. Time-domain simulations were conducted with PSCAD, and the performance of LBFC was validated. [ABSTRACT FROM AUTHOR]

HTS 2G tapes used in Superconducting Fault Current Limiters (SFCLs) have properties that allow for the effective limitation of short-circuit currents; however, due to the specificity of the device operation, they should be characterized by the high stability of the parameters when repeatedly leaving the superconducting state. During the operation of SFCLs, a situation may occur in which the parameters of the HTS tapes used will change several times as a result of the action of short-circuit currents that exceed the critical current IC of the superconductor of the tape used. This paper presents the results of microstructural tests of 2G HTS tapes intended for SFCLs, subjected to surge currents corresponding to prospective short-circuit currents with values higher than their critical currents IC and for which IC changes were observed. The HTS tapes were examined using a JEOL 7600F field emission scanning electron microscope (SEM), and their chemical composition was analyzed using Energy-Dispersive X-ray Spectroscopy (EDS). The test results indicate the possibility of micro-damage in the form of cracks in the superconductor layer, as well as the interruption of the buffer layers and the oxidation of the silver layers. The analysis of the chemical composition of the HTS tape layers may indicate the occurrence of diffusion processes. [ABSTRACT FROM AUTHOR]

In recent years, as the power grid continues to expand, the issue of asymmetrical short-circuit currents exceeding limits on the 220 kV medium-voltage side has become increasingly severe, and traditional current-limiting methods have certain limitations. Therefore, this paper explores the potential benefits and feasibility of installing a Fast Switching Fault Current Limiter (FSFCL) at the neutral point of a 220 kV transformer to effectively limit asymmetrical short-circuit currents on the medium-voltage side. The paper first analyzes the current-limiting performance of the FSFCL under different installation configurations, transformer operating conditions, and fault conditions through theoretical calculations. Subsequently, through simulation studies, the impact of different limiting reactance values on the overvoltage effect at the neutral point is discussed. The results show that the installation of the FSFCL has a significant effect on suppressing the asymmetrical short-circuit current on the medium-voltage side of the transformer, but this measure has also led to an increase in the voltage at the grounded neutral point. Finally, taking the No. 2 main transformer of a certain 220 kV substation as an example, to achieve the expected current-limiting effect, the limiting reactance value of the FSFCL needs to be at least 4 ohms. At this reactance value, the overvoltage level at the neutral point remains well below the withstand limit of its insulating material. Additionally, given the existing overvoltage protection devices at the neutral point, no further overvoltage protection measures are required. [ABSTRACT FROM AUTHOR]

DC fault current limiters (FCLs) are of great significance to the safe and stable operation of DC distribution systems. Among the various FCLs, inductor-based FCLs play an important role. However, the issue of inductor saturation generally exists, which causes limitations in practical engineering applications. A novel LC-resonance-based FCL is proposed in this paper, which can suppress the inductor-saturation effect and create a natural zero-cross current for enhancing performance. In addition, it can cooperate with the AC circuit breaker (ACCB) to quickly cut off faults. A theoretical analysis and the parameter design of the proposed FCL are presented. Finally, a scaled-down experiment test platform is built, and experiment tests and simulation case studies are carried out to verify the working principle and superiorities of the proposed FCL. [ABSTRACT FROM AUTHOR]

The fault level is increasing day-by-day due to huge expansion of electrical network. To cope with the increasing fault level, Fault Current Limiter (FCL) is a good solution. Presently, use of DC loads as well as DC transmission is increasing a lot. Each DC load contains a rectifier circuit with it which helps it to convert the AC power source to DC source. Faults may occur at different positions of the network. This paper gives a detailed discussion on the working analysis of a PMFCL for faults occurring at different position in the rectifier circuit. [ABSTRACT FROM AUTHOR]

Diagnosing faults is crucial for ensuring the safety and reliability of medium-voltage direct current (MVDC) systems. In this study, we propose a bidirectional long short-term memory (Bi-LSTM)-based fault diagnosis scheme for the accurate classification of faults occurring in MVDC systems. First, to ensure stability in case a fault occurs, we modeled an MVDC system that included a resistor-based fault current limiter (R-FCL) and a direct current circuit breaker (DCCB). A discrete wavelet transform (DWT) extracted the transient voltages and currents measured using DC lines and AC grids in the frequency–time domain. Based on the digital signal normalized by the DWT, using the measurement data, the Bi-LSTM algorithm was used to classify and learn the types and locations of faults, such as DC line (PTP, P-PTG, and N-PTG) and internal inverter faults. The effectiveness of the proposed fault diagnosis scheme was validated through comparative analysis within the four-terminal MVDC system, demonstrating superior accuracy and a faster diagnosis time compared to those of the existing schemes that utilize other AI algorithms, such as the CNN and LSTM. According to the test results, the proposed fault diagnosis scheme detects MVDC faults and shows a high recognition accuracy of 97.7%. Additionally, when applying the Bi-LSTM-based fault diagnosis scheme, it was confirmed that not only the training diagnosis time (TraDT) but also the average diagnosis time (AvgDT) were 0.03 ms and 0.05 ms faster than LSTM and CNN, respectively. The results validate the superior fault clarification and fast diagnosis performance of the proposed scheme over those of the other methods. [ABSTRACT FROM AUTHOR]

Abstract This work deals with designing an advanced integral sliding mode controller (AISMC) for residual current compensation (RCC) inverters connected with arc suppression coils to compensate for power distribution networks where the main idea is to alleviate hazardous circumstances caused by electric faults on powerlines. The key advancement in the proposed AISMC over traditional sliding mode controllers is the utilization of an improved exponential reaching law which ensures the faster convergence of the desired control objective that is the fault current compensation in this particular application. An improved exponential reaching law (IERL) used in this work is a combination of the exponential and constant‐proportional reaching laws (while existing approaches use constant reaching laws) which assists to minimize the current injection error through the RCC inverter in the steady‐state. The integral action in conjunction with the exponential function in the sliding surface, based on which the proposed controller is designed, helps to eliminate the chattering effects in a quickest way that can be evidenced from the settling time and percentage overshoot. The feasibility of the proposed AISMC is theoretically assessed by analyzing the stability using the Lyapunov stability theory. Simulation and processor‐in‐loop results further justify the theoretical foundation by confirming the desired current injection and compensating voltage and current due to the fault. Finally, results are compared with a TIMSC for demonstrating the superiority of the AISMC.

Abstract Transmission expansion planning (TEP) is a vital process of ensuring power systems' reliable and efficient operation. The optimization of TEP is a complex challenge, necessitating the application of mathematical programming techniques and meta-heuristics. However, selecting the right optimization algorithm is crucial, as each algorithm has its strengths and limitations. Therefore, testing new optimization algorithms is essential to enhance the toolbox of methods. This paper presents a comprehensive study on the application of ten recent meta-heuristic algorithms for solving the TEP problem across three distinct power networks varying in scale. The ten meta-heuristic algorithms considered in this study include Sinh Cosh Optimizer, Walrus Optimizer, Snow Geese Algorithm, Triangulation Topology Aggregation Optimizer, Electric Eel Foraging Optimization, Kepler Optimization Algorithm (KOA), Dung Beetle Optimizer, Sea-Horse Optimizer, Special Relativity Search, and White Shark Optimizer (WSO). Three TEP models incorporating fault current limiters and thyristor-controlled series compensation devices are utilized to evaluate the performance of the meta-heuristic algorithms, each representing a different scale and complexity level. Factors such as convergence speed, solution quality, and scalability are considered in evaluating the algorithms’ performance. The results demonstrated that KOA achieved the best performance across all tested systems in terms of solution quality. KOA’s average value was 6.8% lower than the second-best algorithm in some case studies. Additionally, the results indicated that WSO required approximately 2–3 times less time than the other algorithms. However, despite WSO’s rapid convergence, its average solution value was comparatively higher than that of some other algorithms. In TEP, prioritizing solution quality is paramount over algorithm speed.

The Java Madura Bali system is the largest interconnection system in Indonesia, covering about 70% of the national electrical energy market. Electricity sales increased from 125.49 TWh in the first half of 2021 to 133.87 TWh in the first half of 2022. To maintain power balance and support energy consumption growth, additional power plants are integrated according to the RUPTL. This research aims to anticipate the increase in short circuit levels for both single-phase to ground and three-phase faults at the Extra High Voltage Substation due to new power plants, ensuring the short circuit level remains below 40 kA, in line with equipment standards. This prevents the costly replacement of 500 kV transmission system equipment. Using the Digsilent application, the study models the existing system, maps the N-1 contingency, and calculates the short circuit levels after the integration of power plants from 2023 to 2028. The results identify the type and optimal location of fault current limiters. Installing these limiters is expected to reduce the short circuit level by 5%, avoiding the need to replace transmission and substation equipment rated at 40 kA. Consequently, the 500 kV system of Java Madura Bali can operate reliably with the new power plant integrations. [ABSTRACT FROM AUTHOR]

This paper presents the implementation of an improved resonance-type FCL, designed to enhance the transient stability of a photovoltaic farm. This FCL overcomes the well-known drawbacks associated with the conventional resonance-based FCLs. This FCL limits the fault during the fault period, quickly achieves stability during the recovery period, independent of the reactor's charging state, and notably reduces DC-link voltage fluctuations during faults. A power system simulation setup comprising a PV farm, synchronous generator, transformers, circuit breakers, transmission system, and several branches of loads is used for testing the proposed FCL. The simulation results validate that the proposed FCL better improves the system's stability and leads to improved fault current, PCC voltage, active power, reactive power, and DC-link voltage compared to other common types of resonant FCLs. [ABSTRACT FROM AUTHOR]

Over the past two decades, Renewable Energy Sources (RESs) have gained global popularity. Control issues are becoming more difficult as the system inertia decreases due to the absence of typical synchronous generators. Innovative methods like fault current limiters, energy storage devices, and alternative control systems are utilized to deal with these difficulties. This study provides a summary of the challenges associated with incorporating high-level RESs into the existing grid. The increased penetration of the RESs has a negative impact on the system oscillations and harmonics, generating the need for power quality improvement techniques, such as adaptive control, adding energy systems, power stream assessment, or weight stream examination. This paper presents a framework of the power stream issue, its arrangement as well as different game plan methods. The power stream model of a power structure can be built using the significant association, weight, and age data. [ABSTRACT FROM AUTHOR]

For the permanent magnet synchronous generator (PMSG) integrated into the flexible interconnected distribution network (FIDN), its low-voltage ride-through (LVRT) strategy needs to be designed to enhance the transient operation capability of the FIDN. The design of the LVRT strategy also needs to take the fault location of the FIDN into consideration. To deal with faults occurring on the integrated feeder of the PMSG, the PMSG needs to realize successful LVRT using the hardware protection equipment. To deal with faults occurring on the feeder adjacent to the integrated feeder of the PMSG, the PMSG needs to release its stored energy to temporarily increase its active power output, which is then supplied to the loads on the faulted feeder that are isolated from the fault through the soft open point (SOP). In this paper, a novel LVRT strategy designed for the PMSG integrated into the FIDN is proposed, which includes dual operation modes that are separately applied to different fault locations. If PMSG is on the faulted feeder, the DC-link voltage of the PMSG is maintained with the controllable resistive fault current limiter (CRFCL), while the maximized stored kinetic energy is reserved to enhance the generation efficiency during the LVRT. If PMSG is on the feeder adjacent to the faulted feeder, the control strategy of the converters of the PMSG is adjusted in response to the power regulation goal at the SOP. Meanwhile, the maximum releasable kinetic energy of the PMSG is considered when increasing its active power output. The feasibility and effectiveness of the LVRT strategy for the PMSG are verified based on the numerical analysis. [ABSTRACT FROM AUTHOR]

Power transmission using a voltage source converter‐ (VSC‐) based high‐voltage direct current (HVDC) system offers autonomous control of real and reactive power, constant DC voltage polarity, and bidirectional power flow. This helps to realize the multiterminal VSC‐HVDC system and its integration into renewable energy sources to meet the growing power demand. However, there is a risk of higher voltages and currents during a DC line fault. The barrier to the advancements of VSC‐MTDC systems is the nonavailability of commercial, higher‐rated DC circuit breakers. This necessitates research on alternative methods of DC fault‐clearing schemes with available technologies. In this direction, a superconducting fault current limiter (SCFCL) is an alternative option to mitigate the problems encountered in VSC‐MTDC system operation. Because of this, there are not many VSC‐MTDC systems available worldwide. This paper discusses different issues associated with the transient performance of the VSC‐MTDC system. A representative case involving resistive SCFCL for DC line protection is presented. The simulations are carried out in the PSCAD/EMTDC platform. [ABSTRACT FROM AUTHOR]

This work deals with designing an advanced integral sliding mode controller (AISMC) for residual current compensation (RCC) inverters connected with arc suppression coils to compensate for power distribution networks where the main idea is to alleviate hazardous circumstances caused by electric faults on powerlines. The key advancement in the proposed AISMC over traditional sliding mode controllers is the utilization of an improved exponential reaching law which ensures the faster convergence of the desired control objective that is the fault current compensation in this particular application. An improved exponential reaching law (IERL) used in this work is a combination of the exponential and constant‐proportional reaching laws (while existing approaches use constant reaching laws) which assists to minimize the current injection error through the RCC inverter in the steady‐state. The integral action in conjunction with the exponential function in the sliding surface, based on which the proposed controller is designed, helps to eliminate the chattering effects in a quickest way that can be evidenced from the settling time and percentage overshoot. The feasibility of the proposed AISMC is theoretically assessed by analyzing the stability using the Lyapunov stability theory. Simulation and processor‐in‐loop results further justify the theoretical foundation by confirming the desired current injection and compensating voltage and current due to the fault. Finally, results are compared with a TIMSC for demonstrating the superiority of the AISMC. [ABSTRACT FROM AUTHOR]

This paper presents the influence of superconducting tape insulation on the recovery time of superconducting fault current limiters. The analysis is based on the experimental results of short-circuit tests. The reduction in the thermal and dynamic effects of the passage of a fault current can be achieved by limiting the short-circuit time and the value of the surge current. An ideal fault current limiter is required to have almost zero impedance at operating currents and significant impedance at fault conditions. A superconducting fault current limiter (SFCL) meets these requirements under certain conditions. The recovery time—a very important parameter—shows the ability of the limiter to return to the superconducting state to be ready to limit the subsequent short circuit. The experimental results show that the recovery time can be significantly reduced with the application of thin-film insulation and an appropriate design of the conduction cooling of the HTS tape. [ABSTRACT FROM AUTHOR]

This research paper presents a new approach to address power quality concerns in microgrids (MGs) by employing a superconducting fault current limiter (SFCL) and a fuzzy-based inverter. The integration of multiple power electronics converters in a microgrid typically increases total harmonic distortion (THD), which in turn results in power quality issues. Moreover, the intrinsic variability of solar and wind power sources gives rise to fluctuations in power generation, which consequently leads to power oscillations and voltage sag within microgrids that rely on renewable energy. This research paper introduces a technical approach to achieve power balance in renewable-based microgrids (MGs) by utilizing a fuzzy logic-controlled (FLC) pulse width modulation (PWM) inverter. The Microgrid (MG) consists of a hybrid photovoltaic (PV) system and a wind energy conversion system (WECS) that utilizes a permanent magnet synchronous generator (PMSG). The system employs an optimal torque-controlled maximum power point technique (MPPT) algorithm to optimize power output. The battery energy storage system (BESS) is employed to facilitate power provision during critical scenarios or to ensure a stable power output for fluctuating loads. The SFCL is utilized as a device for voltage compensation in cases of voltage sag incidents. The effectiveness of the suggested control strategy is assessed by performing a comparative analysis of total harmonic distortion (THD) in the load voltage, with and without the utilization of a SFCL. The results suggest that the incorporation of an FLC inverter-SFCL-BESS system effectively mitigates THD and voltage sag, according to the requirements set by the IEEE 519 standards. The research study is carried out by using the MATLAB/SIMULINK software environment. [ABSTRACT FROM AUTHOR]

Photovoltaic power plant (PVPP) has increased importance among renewable energy sources due to their ability to be connected more easily to a modern power grid. However, the reliability and stability operation of a grid-connected PVPP system is very important to ensure even during grid faults. In this study, a capacitive bridge fault current limiter (CBFCL) using a machine learning (ML) method is applied to enhance the fault ride-through (FRT) capability of a grid-connected PVPP system. Three different protection methods called DC chopper, CBFCL, and DC chopper + CBFCL are designed to prevent the harmful effects of overcurrent that occurs during grid faults to protect the grid-connected PVPP system. The ML algorithm can be trained on historical data to predict optimum control parameters based on real-time conditions such as normal and fault operations of the grid-connected PVPP system. An ensemble classification algorithm has the best results among the four classification algorithms in machine learning methods. The ensemble classification algorithm is separately implemented into the control systems of three protection strategies. Bagged Trees and Subspace KNN classifiers in ensemble classification methods have obtained an impressive accuracy of 98% in ML classification methods. The simulation results illustrate that the DC chopper + CBFCL based ensemble provides the best protection for the grid-connected PVPP system compared to other protection systems. [ABSTRACT FROM AUTHOR]

The intensive development of hydrogen technologies has made very promising applications of one of the cheapest and easily produced bulk MgB2-based superconductors. These materials are capable of operating effectively at liquid hydrogen temperatures (around 20 K) and are used as elements in various devices, such as magnets, magnetic bearings, fault current limiters, electrical motors, and generators. These applications require mechanically and chemically stable materials with high superconducting characteristics. This review considers the results of superconducting and structural property studies of MgB2-based bulk materials prepared under different pressure–temperature conditions using different promising methods: hot pressing (30 MPa), spark plasma sintering (16–96 MPa), and high quasi-hydrostatic pressures (2 GPa). Much attention has been paid to the study of the correlation between the manufacturing pressure–temperature conditions and superconducting characteristics. The influence of the amount and distribution of oxygen impurity and an excess of boron on superconducting characteristics is analyzed. The dependence of superconducting characteristics on the various additions and changes in material structure caused by these additions are discussed. It is shown that different production conditions and additions improve the superconducting MgB2 bulk properties for various ranges of temperature and magnetic fields, and the optimal technology may be selected according to the application requirements. We briefly discuss the possible applications of MgB2 superconductors in devices, such as fault current limiters and electric machines. [ABSTRACT FROM AUTHOR]

Despite many advantages of distributed generation (DG), it can have adverse effects on the network protection coordination by raising the short-circuit level of buses. This issue can often be resolved by incorporating fault current limiters (FCLs) that are properly located and sized in the network. We propose an efficient method to simultaneously attain the optimal location and size of DG and FCL units for protection coordination of overcurrent relays and cost reduction in a distribution network. The proposed method involves three stages. First, two separate objective functions are derived, representing the operation times of relays and the network costs associated with the installation of DGs and FCLs and system losses. The Strength Pareto Evolutionary Algorithm 2 (SPEA-2) is then used for finding a Pareto-optimal solution set for the interrelated multiobjective problem at hand. Finally, the k-means clustering method is utilized to group the best solutions. In contrast to the conventional weighted sum (WS) method, the proposed method is more computationally efficient while being capable of treating complex networks with non-convex Pareto front solutions. These features are demonstrated by implementing the proposed approach in the 14-bus IEEE test grid and comparing the results with those obtained using the conventional WS method. [ABSTRACT FROM AUTHOR]

Despite the unique advantages a doubly fed induction generator (DFIG) offers to the grid‐integrated renewable energy systems, they have a limitation of being susceptible to grid fault as their stator windings are directly connected to the grid. The fault current limiters (FCLs) provide a sustainable solution by enhancing the fault ride‐through capability and thus it improve the transient performance of a DFIG. In this work, a multi‐inductor‐based H‐bridge fault current limiter (HBFCL) is proposed to augment the transient performance of a DFIG. The operational efficacy of the HBFCL is evaluated through the administration of both symmetrical and asymmetrical fault scenarios. The effectiveness of the HBFCL is further investigated by comparing the performance of the HBFCL with that of the bridge‐type series dynamic braking resistor (BSDBR). Both the graphical and numerical interpretations of the simulation result assert that the HBFCL improves the transient performance of a DFIG‐based wind farm and outweighs the performance of the BSDBR in all aspects. [ABSTRACT FROM AUTHOR]

An inrush current is a transient current that results from a sudden change in the exciting voltage across a transformer's windings. Reducing the inrush current of transformers is desirable due to mechanical stresses and negligent operation of protective relay systems such as differential relays. This paper investigates the application of a saturated-core transformer as an inrush current limiter (ICL). Analytical methods of inrush current and its electromagnetic forces on transformer windings with and without application of proposed ICL are presented. Also, the core saturation of the ICL and transformer, in addition to the voltage drop on the ICL in transient and steady states, are investigated. A single-phase transformer is modeled in two dimensions (2-D), and the forces due to inrush current are calculated by the finite element method (FEM) in Maxwell software. The radial and axial force distributions of transformer windings with and without the ICL are investigated. The results show the capability of ICL to limit the transformer inrush current and reduction of its electromagnetic forces. Our simulations demonstrate a significant reduction in inrush current (75 %) using the proposed Inrush Current Limiter (ICL). Additionally, the ICL effectively mitigates electromagnetic forces within the transformer. Compared to a scenario without ICL, the ICL reduces radial forces by 80 % and axial forces by a substantial 90 %. These findings suggest that the ICL offers a promising solution for mitigating both inrush current and the associated electromagnetic forces in power transformers.

Abstract The integration of synchronous generators (SG) to the grid will present serious problems in some instances. The increase in fault current level is one of the most crucial issues, which causes miscoordination between directional over current relays (DOCRs), in addition to putting excessive pressure on the circuit breakers. This research uses the Fault Current Limiters (FCL) to restore coordination, without changing the settings of DOCRs, by reducing the level of fault current in the grid. The main goal of this research is to find the optimal size, location, and number of FCLs at the minimum cost and with the least operation time for the relays, using Jellyfish Search Optimisation (JSO) algorithm. This can be achieved through three different approaches. The first one is optimizing the location, number, and impedance size of the FCL by minimising a cost function. The second approach involves optimizing the backup relay operation time. A combination of the two previous approaches is used as the third approach. The outstanding feature of this research is that it considers the optimal location of DG and FCL while optimizing the operation times of DOCRs, which is a new framework.

In this paper, a novel high temperature superconducting (HTS) thin film device as planar levitator and fault current limiter is firstly proposed and tested. Nowadays, planar magnetic levitation (maglev) levitator (PML) employed in planar maglev system is a promising high-precision positioning mechanism for modern high-end industrial fields, due to the attractive features of noncontact, zero friction, high precision, light weigh, simple structure, high reliability, fast response and fewer interfering factors, etc. In contrast to other maglev technologies, HTS maglev technology has the advantages of passive self stabilization levitation, light weight, high vacuum gain, simple structure, energy saving and no electromagnetic pollution, etc. Thus, the PML fabricated by HTS thin film can further simplify the system control strategy and improve operation efficiency. In this paper, we designed and fabricated the double sided YBa2Cu3O7-x thin film based PML and analyzed its levitation force characteristics. Besides, we also tested its fault current limiting performance, which can be employed to limit the fault current in the planar maglev system. It can be found from the experimental results that, the HTS-PML can offer the levitation force more than 400 kN/m3 and 100 N/kg, meanwhile, it can also generate the quench resistance more than 15 Ω to limit the fault current effectively. This work is perspective for the future planar maglev applications, to improve the system compactness, stability, reliability, miniaturization and lightweight with multifunctional integrated design. [ABSTRACT FROM AUTHOR]

This paper purposes to demonstrate the effectiveness of fuzzy logic controller (FLC) over proportional integral (PI) controller for reducing the fault current and maintaining the voltage profile at different faults conditions using Static Synchronous Compensator (STATCOM) which is considered an effective FACTS (Flexible Alternating Current Transmission System) device. The study evaluates the performance of a power system equipped with STATCOM which is connected in shunt with bus B1 under various faults conditions, including single-phase and three-phase faults. The performance of the STATCOM is evaluated by using two different controllers: PI controllers and FLCs. A comparative analysis is done between the performances of the two different controllers using Matlab/Simulink software package. The results obtained conclude that the presented system gives better performance with STATCOM as compared to not using it under several faults conditions besides, the STATCOM gives better response with FLC as compared to PI controller. It is demonstrated that STATCOM with FLC can reduce the positive sequence fault current at bus B1 to 96.49% of its value without using STATCOM under line to ground fault and 98.17% under three line to ground fault whereas STATCOM with PI controller can reduce it to (99.57, 99.05%), respectively. Also, the bus voltage B1 is improved to 102.19% by using STATCOM with fuzzy controller under line to ground fault and 101.86% under three line to ground fault whereas STATCOM with PI controller can improve it to (100.21, 100.93%), respectively. [ABSTRACT FROM AUTHOR]

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The integration of synchronous generators (SG) to the grid will present serious problems in some instances. The increase in fault current level is one of the most crucial issues, which causes miscoordination between directional over current relays (DOCRs), in addition to putting excessive pressure on the circuit breakers. This research uses the Fault Current Limiters (FCL) to restore coordination, without changing the settings of DOCRs, by reducing the level of fault current in the grid. The main goal of this research is to find the optimal size, location, and number of FCLs at the minimum cost and with the least operation time for the relays, using Jellyfish Search Optimisation (JSO) algorithm. This can be achieved through three different approaches. The first one is optimizing the location, number, and impedance size of the FCL by minimising a cost function. The second approach involves optimizing the backup relay operation time. A combination of the two previous approaches is used as the third approach. The outstanding feature of this research is that it considers the optimal location of DG and FCL while optimizing the operation times of DOCRs, which is a new framework. [ABSTRACT FROM AUTHOR]

This work proposes two alternative analytical models to evaluate the ac losses of high-temperature superconducting (HTS) tapes during their hysteretic and resistive modes. These models intend to extend the application range of state-of-the-art analytical models for current values higher than the critical one, i.e. for the resistive state, and to correctly predict the ac losses during the transition between the hysteretic and resistive modes. Two analytical models are proposed, one considering an extension of the Norris model for the HTS tape's resistive mode and the other based on a sigmoid function to characterize the hysteretic losses and their smooth transition to the resistive mode. Analytical models capable of estimating ac losses of superconducting (SC) tapes are an important tool for the design of complex SC systems, such as SC fault current limiters, SC electrical machines and SC cables. The proposed models are validated experimentally, for a 1st generation BSCCO tape and a 2nd generation REBCO tape. Finite element simulation is also carried out to verify the accuracy of the proposed models. Results show that the proposed extended-Norris model presents some deviation at the transition between the hysteretic and resistive modes, while the sigmoid model presents very accurate results for the whole spectrum of applied current. Also, the parameters of the sigmoid models are independent of the tape geometry. [ABSTRACT FROM AUTHOR]

In recent years, with the rapid development of high-voltage flexible direct current (DC) transmission systems, more and more multi-port high-voltage DC systems have been successfully put into operation. Therefore, the number of connecting ports on the DC bus is gradually increasing, which necessitates higher requirements for clearing fault current. To better protect the DC power grid, this paper integrates a DC fault current limiter with a multi-port DC circuit breaker. This article proposes a modular cascaded multi-port hybrid DC circuit breaker topology. It also elaborates on the topology structure, working principle, and control program under three different fault conditions. It completes the theoretical derivation and analysis of the circuit breaker fault isolation process, as well as the parameter design of the core components. Finally, a model is established in PSCAD/EMTDC for simulation verification. The application performance of the circuit breaker in four-terminal DC systems is studied and analyzed, and the current-limiting effect of the multi-port DC circuit breaker proposed in this article is demonstrated. In addition, the disconnection performance and energy consumption of the arrester have been improved to a certain extent, which has good feasibility and economy. [ABSTRACT FROM AUTHOR]

Several types of fault current limiters have been studied so far, including superconductor based one or nonsuperconductor based one. However, it is difficult to satisfy all requirements for cost, maintainability, and current limiting performance. This study proposes another type of fault current limiter, variable transformer based one. It is supposed to be less expensive and easier to be maintained since it is based on the conventional transformer, and to be expected better current limiting performance since the magnetic circuit of the transformer is drastically changed. The magnetic circuit of the transformer is switched to be opened and to produce another one by shifting a portion of its iron core mechanically, allowing the primary and secondary electric circuit to be magnetically isolated. In that way, the electromotive force of the secondary winding could be reduced so that the secondary current could be limited. The prototype based on this concept was designed and built up, and its stational performance has been investigated. As a result, it was confirmed that the prototype shows good current limiting performances identical to the results of the previous FE analysis. Furthermore, the prototype was connected to the operating mechanism to investigate the transient performances, and as a result, satisfying current limiting performances are confirmed [ABSTRACT FROM AUTHOR]

This research addresses the challenge of grid stability when integrating renewable energy, especially wind power. It focuses on enhancing transient stability in doubly fed induction generator (DFIG) wind energy systems using advanced strategies like fault current limiters and deep learning. The study includes a thorough analysis of fault scenarios, simulations, and solution evaluations, highlighting the crucial need for maintaining stability in renewable energy grids. As wind energy demand rises, optimizing system performance is vital. Many wind turbines rely on DFIGs, necessitating robust fault ride-through. A passive fault current limiter is introduced to enhance DFIG system transient stability. This limiter, devoid of active controllers, offers intrinsic resilience. The research introduces a novel algorithm to calculate optimal fault current limiter resistance, maintaining voltage within ±10% of the reference level. Transient stability is evaluated through simulations involving symmetric and asymmetric faults, incorporating deep learning. MATLAB/Simulink confirms the efficacy of the proposed limiter and algorithm in boosting transient stability for DFIG-based wind energy systems. The study underscores the role of fault current limiters and deep learning in seamlessly integrating renewable energy into power grids. [ABSTRACT FROM AUTHOR]

Abstract The escalating levels of fault currents resulting from short circuits, particularly in the context of distribution generators, have presented a critical need for the widespread implementation of fault current limiters (FCLs) in power systems. Despite their evident advantages, the extensive adoption of FCLs has been hindered by the high production costs associated with these devices. To address this challenge, a comprehensive study was conducted to develop a cost-effective FCL tailored specifically for three-phase power systems. This paper proposes a novel approach based on a single commutation circuit for the FCL and offers detailed insights into the construction of the FCL circuit, with a particular focus on efficient current interruption. Additionally, the study comprehensively discusses the logic controller and measurement system employed in conjunction with the proposed FCL, ensuring precise fault detection and rapid response to disturbances within the power grid. The integration of an artificial zero-crossing circuit within the FCL design further enhances its capability to limit short-circuit currents proactively, even before the occurrence of the first peak, thereby bolstering overall system reliability and stability. The study's significant contribution lies in achieving cost-effectiveness through the simplicity of the FCL's design, eliminating the need for extensive upgrades to various network components.

Abstract This paper proposes a new adaptive nonlinear extended state observer‐based model predictive controller (ANLESO‐MPC) for residual current compensation (RCC) inverters to compensate fault characteristics in resonant grounded power systems (RGPSs). In the proposed scheme, the adaptation feature is used to adapt the adjustable inductor appearing in the dynamical model of RGPSs by satisfying the desired fault current compensation requirement which in turn will ensure the resonance condition. Since the adapted parameter is used in the control signal, the ANLESO‐MPC offers robustness against parameter sensitivity. The neutral voltage is considered as a disturbance and the change in this voltage as an extended state to estimate this disturbance while incorporating the adapted parameter so that the adaptive nonlinear extended state observer (ANLESO) provides robustness against disturbances. Finally, the model predictive controller (MPC) is designed for the RCC inverter utilizing estimated disturbances and adapted parameters to fully achieve the fault current compensation. The performance of the controller is evaluated using simulations in MATLAB/Simulink and OPAL‐RT real‐time platforms under varying fault impedances as the fault characteristics change with variations in the fault impedance. Results are also compared with a conventional MPC where the proposed ANLESO‐MPC seems more effective to compensate fault characteristics.

With the ongoing expansion and interconnection of electrical power systems, alongside the rapid proliferation of renewable distributed generations (DGs), the short-circuit extent in the power grid is experiencing a significant rise. Fault current limiters (FCLs) have been introduced in an effort to address this issue, ensuring the robustness and sustainability of expensive power system components when confronted with short-circuit faults. Among the various types of FCLs, bridge-type DC reactor fault current limiters (BDCR-FCLs) have emerged as one of the most promising options. While BDCR-FCLs have shown excellent properties in limiting harmful short-circuit currents, they are also advantageous in other respects. This paper investigates the supplementary functionalities of BDCR-FCLs as a multifaceted device towards the enhancement of the quality of supplied energy in terms of total harmonic distortion (THD) reduction, power factor (PF) correction, peak current reduction for nonlinear loads, and soft load variation effects, as well as their capability to limit fault current. To this aim, the capabilities of BDCR-FCLs have been studied through various simulated case studies in PSCAD/EMTDC software V5.0.1, in addition to experimental tests considering an AC microgrid connected to a DC system. The experimental and simulation investigations verify the superior multifaceted functionalities BDCR-FCLs introduce in addition to their excellent fault current-limiting capabilities. The results show that PF improved by 6.7% and 7%, respectively, in simulation and experimental tests. Furthermore, the current THD decreased by 20% and 18% in the simulation and experiment, respectively. [ABSTRACT FROM AUTHOR]

Various methods are used to reduce fault currents in fault situations occurring in power systems. In this study, a developed single-phase power electronics-based solid-state fault current limiter is presented. The proposed single-phase solid-state fault current limiter is designed as preliminary prototype of the three-phase low voltage solid-state fault current limiter. The maximum current and voltage capability of the fault current limiter is 16 A and 480 V. This limiter works according to the principle of series and parallel resonance. In normal operation, the current passes through the inductance and capacitor, which are in series resonance. Thus, extra voltage drops and power loss in the system are prevented. In the event of a fault, the limiter switches to parallel resonance, and its impedance increases. Therefore, the fault current is decreased. The developed circuit and control algorithm reduces the first peak of fault current with a rather high percentage by comparison with the fault current without fault current limiter. In addition, the amplitude of current oscillation is decreased, and the current is recovered in a short time because the control algorithm determines the fault start and end time fast. The effect of the limiter is demonstrated with the simulation results in Matlab/Simulink. The simulation results are verified with the application study carried out in the laboratory environment. The fault current reaches up to 58.5 A in case of fault current limiter is not used, whereas the developed fault current limiter suppresses the current to around 9 A. The value of maximum fault current decreases to 15% according to the non-fault current limiter used situation. In the study, detailed application notes of the limiter circuit are shared. [ABSTRACT FROM AUTHOR]

Installing a three-phase saturated core fault current limiter (TSFCL) is an effective method to limit the increasing short-circuit current in high-voltage alternating current (HVAC) systems. However, the traditional TSFCL uses silicon steels as its working material for the iron core, resulting in poor current-limiting effects, requiring a large DC excitation current, and having a slow response speed. Nanocrystalline alloys have advantages such as a lower saturation point, higher permeability in the unsaturated zone, and a steep B–H curve, making them highly suitable for TSFCL's applications. However, their poor capability which withstands fault hindered their large-scale commercialization. Therefore, this paper proposes a novel hybrid magnetic material based on TSFCL (HMTFCL), where the materials of the working limbs are replaced by nanocrystalline alloys. Compared to TSFCL, the DC excitation current of HMTFCL decreases by 60.5%. And, the HMTFCL reduces the peak short-circuit current by 23%. Last, the magnetic flux intensity inside the working limb of HMTFCL is reduced to zero more quickly. [ABSTRACT FROM AUTHOR]

Coreless fault current limiter with variable series reactor is an emerging technology for limiting the amplitude and shortening the fault duration in the power network with simple and reversible operation. The device includes two coaxial, coreless reactors with axial mobility to vary and increase the effective inductance of the network during the short circuit fault. The reactors are automatically returned back to their initial position after the fault is cleared, with minimal net inductance. This paper aims to analytically describe the electromagnetic theory and validate the functionality of the device. For this purpose, the resistance and inductance of the device are first computed at normal condition via the basic theory of engineering electromagnetics. Next, the respective electromechanical performance characteristics such as force, positional displacement of the reactors, and the effective inductance are calculated at the faulty condition. For verification purposes, analytical results are compared against the finite element model. [ABSTRACT FROM AUTHOR]

This research paper represents the estimation and reduction of eddy current loss in a Magnetic Fault Current Limiter (MFCL). The nonlinear model of the device is established using electromagnetic coupled circuit supported by Finite Element Model. The current limiting performance of the MFCL is investigated by simulation study as well as laboratory testing. It is further observed that a significant amount of eddy current loss takes place inside the core and permanent magnet of the device. Different methods (shorting ring, lamination of permanent magnet and variation of magnet length) are proposed to reduce the eddy current. The advantages and disadvantages of these methods are discussed. Some design modifications are also proposed to minimize the temperature rise caused by the eddy current. [ABSTRACT FROM AUTHOR]

A fault self-driven current limiter is proposed in the paper, which uses a special fault current direct-driven electromagnetic repulsion mechanism to realize the first half-wave of the fault current over the zero point into the current-limiting reactance. The paper analyzes the working principle of the self-driven electromagnetic repulsion mechanism, establishes the equivalent model of the mechanism, and simulates the dynamic characteristics of the electromagnetic repulsion mechanism through the calculation of the double- layer iterative algorithm in time and space. The LC oscillation loop test platform is built, and the stroke-time curve of the prototype is measured. In the test, the prototype is driven by a 3 kA current, and the first half-wave stroke (FHWS) is 3.55 mm past the zero point, which is consistent with the simulation and test results. The effects of structural parameters such as the radius, thickness, and number of turns of the self-driven electromagnetic repulsion mechanism on the dynamic characteristics of the electromagnetic repulsion mechanism are investigated, and it is found that the first half-wave stroke can be significantly improved by increasing the number of turns and outer diameter of the coil. The optimum height of the dynamic repulsion coil is approximately 3 mm. [ABSTRACT FROM AUTHOR]

The escalating levels of fault currents resulting from short circuits, particularly in the context of distribution generators, have presented a critical need for the widespread implementation of fault current limiters (FCLs) in power systems. Despite their evident advantages, the extensive adoption of FCLs has been hindered by the high production costs associated with these devices. To address this challenge, a comprehensive study was conducted to develop a cost-effective FCL tailored specifically for three-phase power systems. This paper proposes a novel approach based on a single commutation circuit for the FCL and offers detailed insights into the construction of the FCL circuit, with a particular focus on efficient current interruption. Additionally, the study comprehensively discusses the logic controller and measurement system employed in conjunction with the proposed FCL, ensuring precise fault detection and rapid response to disturbances within the power grid. The integration of an artificial zero-crossing circuit within the FCL design further enhances its capability to limit short-circuit currents proactively, even before the occurrence of the first peak, thereby bolstering overall system reliability and stability. The study's significant contribution lies in achieving cost-effectiveness through the simplicity of the FCL's design, eliminating the need for extensive upgrades to various network components. [ABSTRACT FROM AUTHOR]

This paper proposes a new adaptive nonlinear extended state observer‐based model predictive controller (ANLESO‐MPC) for residual current compensation (RCC) inverters to compensate fault characteristics in resonant grounded power systems (RGPSs). In the proposed scheme, the adaptation feature is used to adapt the adjustable inductor appearing in the dynamical model of RGPSs by satisfying the desired fault current compensation requirement which in turn will ensure the resonance condition. Since the adapted parameter is used in the control signal, the ANLESO‐MPC offers robustness against parameter sensitivity. The neutral voltage is considered as a disturbance and the change in this voltage as an extended state to estimate this disturbance while incorporating the adapted parameter so that the adaptive nonlinear extended state observer (ANLESO) provides robustness against disturbances. Finally, the model predictive controller (MPC) is designed for the RCC inverter utilizing estimated disturbances and adapted parameters to fully achieve the fault current compensation. The performance of the controller is evaluated using simulations in MATLAB/Simulink and OPAL‐RT real‐time platforms under varying fault impedances as the fault characteristics change with variations in the fault impedance. Results are also compared with a conventional MPC where the proposed ANLESO‐MPC seems more effective to compensate fault characteristics. [ABSTRACT FROM AUTHOR]

Abstract The algorithms of the present generation of practical differential relays are based on two methods. The first method is based on the ratio of the harmonic content of the differential current, and the second one is based on the length of the time interval between the zero‐crossing points of the differential current, called the gap‐detection method. However, these methods suffer from the installation of the fault current limiters (FCLs) in the power system and current transformer (CT) saturation phenomenon. This paper deals with a simple practical method for differential relays to secure their performance. In the suggested method, a classifying algorithm is used to categorize the input signal of the relay and then the best method of the present generation of differential relays is employed. By this simple decision, the method takes the advantage of harmonic‐based and gap‐detection methods, while avoiding their drawbacks. To prove the robustness of the suggested method, a test bench with a resistive solid‐state fault current limiter (SSFCL) is implemented and examined in different situations. The results validate the consistency and the accuracy of the modified technique not only in the absence and the presence of the FCL but in the case of CT saturation.

Abstract Multi‐input converters play an important role in integrating the independent energy sources utilized in the grid‐connected system and electric vehicle (EV) applications. In this scenario, several types of multi‐input converters are presented in the literature. Most of the MICs are operated using a time‐sharing scheme. This leads to a restricted duty cycle which limits the energy sources utilization and output voltage. To overcome the aforementioned limitations, a multi‐input single‐output (MISO) boost converter is proposed. It can improve the utilization of energy sources and output voltage with a reduction in the part count. To verify the feasibility of the proposed scheme, a 200 W prototype circuit is developed; simulation and experimental results are validated.

Abstract The authors deal with design and analysis of an air‐core electromagnetic fault current limiter (FCL) with rotary motion. The proposed device is characterised by a simple structure, fast operating speed and reversible operation. It consists of two movable concentric air core spherical reactor rings (i.e. inner and outer rings) with variable mutual angular displacement. At normal condition, reactors are approximately aligned, and subsequently, the effective inductance/impedance of the equipment and the respective voltage drop are low. At faulty conditions, the short circuit current exerts a repulsive rotary electromagnetic torque on the reactors, which results in a fast and steady increase of the reactors angular displacement. During this process, the effective inductance of the equipment rapidly rises up to a level that effectively limits the short circuit current. To determine the effectiveness of the proposed topology in limiting the network's fault current, the inductance profile of the proposed rotary FCL and the respective fault current characteristic are compared with similar case studies (a) with linear FCL and (b) without FCL. The analysis is carried out via a finite element (FE) and supported via analytical and theoretical discussion. Finally, a down‐scale prototype of the proposed FCL was built and tested to verify the functionality of the device in the lab environment.

A saturated iron-core type superconducting fault current limiter (SI-SFCL) can effectively restrict the magnitude of the fault current and alleviate the strain on circuit breakers in DC power systems. Design of a superconducting coil (SC), which is one of the key tasks in the SI-SFCL design, requires guaranteeing a sufficient magnetic field, ensuring optimization of the shape and size, minimizing the wire cost, and satisfying the safety and stability of operation. Generally, finite element method (FEM) is used to calculate and evaluate the operating characteristics of SCs, from which it is possible to determine their optimal design parameters. When the coil is complex and large, the simulation time may range from hours to days, and if input parameters change even slightly, the simulations have to be redone from scratch. Recent advances in deep learning represent the ability to be effective for modeling and optimizing complex problems from training data or in real-time. In this paper, we presented a combination of the FEM simulation and deep Q-network (DQN) algorithm to optimize the SC design of a lab-scale SI-SFCL for a DC power system. The detailed design process and options for the SC of SI-SFCL were proposed. In order to analyze the characteristics related to the electromagnetic properties and operational features of the SC, a 3D FEM model was developed. Then, a DQN model was constructed and integrated with the FEM simulation for training and optimizing the design parameters of the SC in real-time. The obtained results of this study have the potential to effectively optimize the design parameters of large-scale SI-SFCL development for high-voltage DC power systems. [ABSTRACT FROM AUTHOR]

Resistive-type superconducting fault current limiters (r-SFCLs) have generated great interest for research and technical applications. This is attributed to their superior features, which include self-action, fast response, and simple operation. In low line impedance systems, r-SFCLs are seen as a viable protective mechanism for limiting high-magnitude fault currents. However, overcurrent caused by faults results in an increased temperature of the r-SFCL, possibly damaging the coils. Thus, the r-SFCL must be appropriately engineered to protect it while still allowing for effective fault current limitation. To achieve this goal, an appropriately sized shunt resistor must be used. Adding a shunt resistor benefits the r-SFCL in several ways, from lowering its maximum temperature to speeding up its recovery. Additionally, the shunt resistor protects the r-SFCL from excessive surges in temperature by giving the current an alternative path to flow down, thus saving it from further damage. A multilayer thermoelectric model was developed to examine the thermoelectrical behavior of the r-SFCL coil throughout a fault occurrence and the subsequent recovery period using three shunt resistors ranging from 4 to 16 Ω. MATLAB®/Simulink was used as the simulation platform in this study. The dependence of the current limitation capability and the voltage profile on the shunt resistor value was studied compared to the basic case without an r-SFCL. Increasing the shunt resistor value led to an enhanced ability to limit fault currents, although at the cost of higher temperatures and a longer recovery time. This study also presents guidance for optimizing the design parameters of r-SFCLs. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to clarify voltage sourced converter's (VSC's) influence rules on the alternating current (AC) short-circuit current and identify the key factors, so as to propose the short-circuit current suppression strategy. Design/methodology/approach: This paper investigates the key factors which impact the short-circuit current supplied by the VSC based on the equivalent current source model. This study shows that the phase of the VSC equivalent current source is mainly affected by the type of fault, whereas the amplitude is mainly decided by the control mode, the amplitude limiter and the electrical distance. Based on the above influence mechanism, the dynamic limiter with short-circuit current limiting function is designed. The theoretical analysis is verified by simulations on PSCAD. Findings: The short-circuit current feeding from VSC is closely related to the control mode and control parameters of the VSC, fault type at AC side and the electrical distance of the fault point. The proposed dynamic limiter can make VSC absorb more reactive power to suppress the short-circuit current. Research limitations/implications: The dynamic limiter proposed in this paper is limited to suppress three-phase short-circuit fault current. The future work will focus more on improving and extending the dynamic limiter to the fault current suppression application in other fault scenarios. Practical implications: The research results provide a reference for the design of protection system. Originality/value: The key influence factors are conducive to put forward the measures to suppress the fault current, eliminate the risk of short-circuit current exceeding the standard and reduce the difficulty of protection design. [ABSTRACT FROM AUTHOR]

High level of fault currents has become one of the most challenging issues, along with increased electrical energy consumption and power grid expansion. However, some of the previous work was limited to installing limiters on designs and installing them on small plans. Here, the optimal placement of a resistive‐type superconducting fault current limiter (RSFCL) to achieve good power system transient stability is proposed. The proposed method has several advantages. First, procedure fault analysis is applied to consider the magnitude of the short‐circuit currents and the line located close to the generator for the placement of the device. Compared with other methods, it can directly find the exact line to be installed RSFCL. Second, the stability assessment is validated using the time domain simulation by installing limiters with varying capacities in any location. Third, parameters were analysed to evaluate the proposed method's effectiveness, including angular speed, rotor angular velocity, and generator rotor angle in a multi‐machine system. The result reveals that the placement of the limiter on the line with the most significant short‐circuits value on the line closest to the generator increases the power system stability more than the placement in other locations. [ABSTRACT FROM AUTHOR]