Nand K. Singh

Analysis of Transient Stability Enhancement of LV-Connected Induction Microgenerators by Using Resistive-Type Fault Current Limiters

In this paper an analytical method by which the transient stability of an induction machine is maintained regardless of the fault clearance times is introduced. The method can be applied in order to improve the transient stability of a large penetration of low-voltage (LV) connected microgeneration that can be directly interfaced by single-phase induction generators within domestic premises. The analysis investigates the effectiveness of using resistive-type superconducting fault current limiters (RSFCLs) as remedial measures to prevent the microgenerators from reaching their speed limits during remote faults, and hence improving their transient stability. This will prevent unnecessary disconnection of a large penetration of LV-connected microgeneration and thus avoiding the sudden appearance of hidden loads, and unbalanced voltage conditions. The minimum required value of a resistive element of RSFCL for mitigating the transient instability phenomena of LV-connected microgeneration based on the system and connected machine parameters is determined. The analytical method has been validated by conducting informative transient studies by using detailed models of a small microwind turbine with constant mechanical output interfaced directly within residential dwellings by a single-phase induction generator, a transient model of resistive superconducting fault current limiter (RSFCL), and a typical suburban distribution network with residential loads. All the models are developed in the time-domain PSCAD/EMTDC dynamic simulation.

Application programmer interface for the EPRI Distribution Engineering Workstation

The Electric Power Research Institute Distribution Engineering Workstation is a software package which provides an integrated data environment designed to meet the analysis, planning, design, and operation needs of distribution engineering. DEWorkstation features an open architecture design that provides access for anyone wishing to add applications. DEWorkstation concepts are introduced and the application programmer interface is described. >

Analysis of Energy Dissipation in Resistive Superconducting Fault-Current Limiters for Optimal Power System Performance

Fault levels in electrical distribution systems are rising due to the increasing presence of distributed generation, and this rising trend is expected to continue in the future. Superconducting fault-current limiters (SFCLs) are a promising solution to this problem. This paper describes the factors that govern the selection of optimal SFCL resistance. The total energy dissipated in an SFCL during a fault is particularly important for estimating the recovery time of the SFCL; the recovery time affects the design, planning, and operation of electrical systems using SFCLs to manage fault levels. Generic equations for energy dissipation are established in terms of fault duration, SFCL resistance, source impedance, source voltage, and fault inception angles. Furthermore, using an analysis that is independent of superconductor material, it is shown that the minimum required volume of superconductors linearly varies with SFCL resistance but, for a given level of fault-current limitation and power rating, is independent of system voltage and superconductor resistivity. Hence, there is a compromise between a shorter recovery time, which is desirable, and the cost of the volume of superconducting material needed for the resistance required to achieve the shorter recovery time.

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Superconducting fault-current limiters are being considered as a potential technology for restricting fault current to acceptable levels without extensive and costly network asset replacement. Such an issue currently arises primarily from the connection of a distributed generation. This paper first investigates the fault studies of an active medium-voltage distribution network with several superconducting fault-current-limiter deployment strategies and then considers their impact on circuit-breaker transient recovery voltage. These circuit-breaker characteristics at various voltage levels have been studied, and it is demonstrated that the superconducting fault-current limiter is capable of reducing both the magnitude and the rate of rise of the transient recovery voltage.

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The paper investigates the operation of a novel power converter for the switched reluctance generator. The sparse PWM converters reduce switch count and eliminate the front-end current smoothing inductor which leads to a low cost and small converter. The performance of the converter is investigated and simulation results are presented

Superconducting Fault-Current Limiter in an Active Distribution Network

Impact of HVDC converter energization connected to muti-terminal hub on network performance is presented in this paper. Due to capacitors used in HVDC converter, its energization produces a higher inrush current causing a severe voltage dip in both the ac and dc systems potentially exceeding the allowable limits. Similarly dc cable and HVDC transformer energization also causes a higher inrush current that can damage the semiconductor devices used in the converter system. The paper discusses fundamental principles, energization schemes and pre-insertion resistors as a mitigation measure among other. A case study was selected and the results are presented under various grid-conditions.

Evaluation of Sparse PWM Converter for Switched Reluctance Generator

This paper widens the knowledge about the microgeneration transient response under faulted conditions. The paper provides the following significant contributions: Firstly, a range of microgeneration transient models have been developed in PSCAD/EMTDC and tested on a typical distribution network. Two types of technologies are considered: a small diesel engine driving a three-phase synchronous machine connected within commercial premises; and a small microwind turbine interfaced directly within residential dwellings by a single-phase induction generator. Secondly, a valuable insight into the transient behavioral of this range of technologies during and after the clearing of remote faults at a medium voltage (MV) distribution system is provided, and their resilience levels are quantified. Thirdly, for reliable microgeneration operating in parallel with the distribution networks, the paper includes a discussion on some of remedial measures by which the transient stability of a large penetration of microgeneration may be improved. Also in this paper the inclusion of resistive superconducting fault current limiters into medium voltage distribution systems has been proposed as one of the practical solutions that can enhance the transient performance of large numbers of low voltage connected microgeneration. The effectiveness of fault current limiters on the grid-connected microgeneration transient stability enhancement has also been evaluated.