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Increasing the penetration level of distributed generation (DG) units in radial power distribution systems can increase the short-circuit level in these networks, which can, in turn, have destructive effects such as exceeding the tolerable current of the equipment and disrupting the protective coordination in the network. The active superconducting fault current limiter (ASFCL) is a new device that can limit fault current using voltage series compensation. This paper discusses the modeling of ASFCL and control strategies including fault detection and converter performance in normal and fault modes. Initially, its performance in limiting the fault current is investigated by simulating a sample three-phase system with ASFCL. In the next step, three operating modes including normal mode, upstream fault mode, and downstream fault mode are proposed to achieve an adaptive FCL that solves these problems in gridconnected microgrids. The simulation results confirm the proper performance of the ASFCL modes in both fault current limiting and protective coordination of overcurrent relays in the network. [ABSTRACT FROM AUTHOR]

Active superconducting fault current limiter (ASFCL) is a new type of FCLs which can limit the fault current at different levels. It also has a particular ability to compensate for voltage series in the electrical power systems. In this paper, an optimal coordination method is proposed to calculate both optimal setting parameters of overcurrent relays (OCRs) and limiting the impedance of ASFCL. The optimal parameters of OCRs are obtained using the maximum pickup current and minimum trip time method. In the next step, by applying a new DG unit to the microgrid, the optimal limiting impedance of ASFCL is obtained so that all OCRs could be coordinated without changing the relay setting parameters. Using MATLAB software, a typical distribution system connected to a microgrid with ASFCL is simulated and the simulation results are evaluated in terms of the fault current limitation and OCRs coordination. Simulation results confirm the appropriate performance of the proposed ASFCL for the above-mentioned purposes. [ABSTRACT FROM AUTHOR]

In this paper, an active superconducting current controller is used for fault current limiting, protective coordination, and voltage compensating in a typical power system. In the grid-connected micro-grid, the performance of a conventional fault current limiter can disrupt the protective coordination of the micro-grid overcurrent relays as well as the relays between the main grid and micro-grid. The control strategy is designed for implementing normal limiting impedance in the upstream fault mode and a zero limiting impedance in the downstream fault mode so that the protective coordination between all relays is maintained. Also, to investigate the effect of the controller on voltage compensating, by obtaining the line transmission matrix, the controller setting parameters for compensating the voltage at any point of the line are obtained. In this case, the controller is adjusted such that the magnitude of the receiving end and the sending end voltages of the line become equal. Simulation results using MATLAB software confirm the proper performance of the proposed active controller for the above-mentioned purposes. [ABSTRACT FROM AUTHOR]

In this paper, the effects of STATCOM on improving the static voltage stability and reduction of the losses in a power system are investigated. In the first step, to analyze the static voltage stability, STATCOM is modeled for inserting in Newton-Raphson Power flow equations. Then the static voltage stability study is performed by modal analysis. By using this method critical areas and the best location for STATCOM are determined. Case studies are carried out on a EHV practical 24-bus system .To confirm the effects of STATCOM on voltage stability improvement and reduction of the active and reactive losses, three cases (with STATCOM and without STATCOM) consist of: 1) base case, 2) case of increasing load at critical buses and 3) case of line outage are carried out. [ABSTRACT FROM AUTHOR]

This paper provides an algorithm of fault resistance compensation for digital ground distance relay considering the voltage and current transformer effects. Performance of the conventional ground distance relaying manner is adversely affected by different ground faults and also typical type, called a simultaneous open conductor and ground fault. The proposed scheme by using local-end data only, has shown satisfactory performances under wide variations in fault location, with different values of fault resistance and having positive and negative of power transfer angle. The presented method which has been carried out on the IEEE 14 bus benchmark is executed in PSCAD/EMTDC and MATLAB software, and the results show the accurate performance of mentioned configuration. [ABSTRACT FROM AUTHOR]

This paper provides an algorithm of fault resistance compensation for digital ground distance relay considering the voltage and current transformer effects. Performance of the conventional ground distance relaying manner is adversely affected by different ground faults and also typical type, called a simultaneous open conductor and ground fault. The proposed scheme by using local-end data only, has shown satisfactory performances under wide variations in fault location, with different values of fault resistance and having positive and negative of power transfer angle. The presented method which has been carried out on the IEEE 14 bus benchmark is executed in PSCAD/EMTDC and MATLAB software, and the results show the accurate performance of mentioned configuration. [ABSTRACT FROM AUTHOR]