Resistive Type Superconducting Fault Current Limiter Research Articles

A study on application of SFCL in vietnam power distribution system with distributed generators (DGs)

As the power load demand is rapidly increasing nowadays, many new power generation units are continuously connected to the power system such as small hydropower, wind power, solar cell, and so on. However, in a distribution system, the presence of Distributed Generators (DGs) would generally change the distribution system's behavior. This change can affect to the operation and protection of devices in power system and the original parameters will be deviated. Especially, the fault current of power system with DGs is dramatically increasing, and Superconducting Fault Current Limiter (SFCL) has attracted lots of attention as one of the best correctives to solve these issues. This paper proposes a strategy on application of SFCL in distribution system to solve the problems related to excessive short-circuit current and the mitigation of voltage sag due to the introduction of the DGs. Firstly, a Resistive-type SFCL (R_SFCL) is modeled by Matlab/Simulink. Next, a distribution system of Southern Vietnam power system is selected and simulated. Finally, according to the simulation results, the short circuit current and voltage sag improvements can be validated.

A study on application of SFCL in vietnam power distribution system with distributed generators (DGs)

As the power load demand is rapidly increasing nowadays, many new power generation units are continuously connected to the power system such as small hydropower, wind power, solar cell, and so on. However, in a distribution system, the presence of Distributed Generators (DGs) would generally change the distribution system's behavior. This change can affect to the operation and protection of devices in power system and the original parameters will be deviated. Especially, the fault current of power system with DGs is dramatically increasing, and Superconducting Fault Current Limiter (SFCL) has attracted lots of attention as one of the best correctives to solve these issues. This paper proposes a strategy on application of SFCL in distribution system to solve the problems related to excessive short-circuit current and the mitigation of voltage sag due to the introduction of the DGs. Firstly, a Resistive-type SFCL (R_SFCL) is modeled by Matlab/Simulink. Next, a distribution system of Southern Vietnam power system is selected and simulated. Finally, according to the simulation results, the short circuit current and voltage sag improvements can be validated.

Study of Resistive SFCL and UPFC for Transient Behavior Enhancement of Multi-Machine Power System

Based on a resistive-type superconducting fault current limiter (SFCL) as well as a unified power flow controller (UPFC), this paper researches the combined utilization of them to improve a multi-machine power system’s transient stability. The SFCL is firstly to provide a fault current-limitation. Then, the UPFC is to realize an efficient power flow adjustment and a precise stabilizing control. Related modeling and control are presented, and a four-machine two-area test system including a SFCL and a UPFC is simulated in MATLAB. Different simulation conditions are applied, and it can be concluded that: (i) The SFCL-UPFC enables to more directly and powerfully refrain the fault current surge, mitigate the bus voltage sag and alleviate the inter-area oscillation. (ii) As the increase of fault clearance time, the power system’s demand for the SFCL-UPFC’s stabilizing effect would be very critical. (iii) Compared to the asymmetric fault, the SFCL-UPFC owns a better ability to handle the symmetric fault.

Application and Design of a Resistive-Type Superconducting Fault Current Limiter for Efficient Protection of a DC Microgrid

Regarding a dc microgrid integrated with wind, photovoltaic generators, and energy storage, this paper suggests a resistive-type superconducting fault current limiter (SFCL) to protect it from short-circuit fault. The modeling and control of the dc microgrid are first stated, and then, the resistive SFCL's impacts on the dc microgrid's fault current and bus voltage sag are analyzed in brief. Using MATLAB, simulations on different SFCL parameters are done, and the results confirm the SFCL's contributions for the dc microgrid include the following. First, the dc fault current is limited quickly and effectively. Second, the bus voltage drop is compensated enough to ensure that the renewable sources achieve the fault ride-through operation. Third, the power transfer efficiency of the dc microgrid under the fault is appropriately enhanced. Finally, the resistive SFCL's conceptual design is done. Not only is the magnetic field/current density distribution of the HTS tape given, but the Ampere Force and ac loss are also estimated. In summary, the feasibility of the resistive SFCL for the dc microgrid is verified.

A Low Voltage Ride Through Scheme for DFIG-Based Wind Farm With SFCL and RSC Control

Taking into consideration the low voltage ride through (LVRT) demand proposed in grid codes, a resistive-type superconducting fault current limiter (R-SFCL) LVRT solution is presented in this paper for doubly fed induction generator (DFIG) based wind turbine generators. The installed position, equivalent modelling of R-SFCL, and technical principle for improving LVRT capability are described. Cooperative control between R-SFCL and two advanced control strategies-reactive power control (RPC) and inductance-emulating control (IEC)-are introduced in this paper to help the DFIG generate reactive power and protect key parameters during grid faults. Simulations and performance evaluation are also conducted compared with the single IEC scheme and single RPC-IEC scheme, which demonstrate the effectiveness and superiority of the proposed scheme in enhancing LVRT capability.

Numerical AC Loss Analysis in HTS Stack Carrying Nonsinusoidal Transport Current

Bifilar coil structure is promising for reducing ac loss in resistive-type superconducting fault current limiters (FCLs). However, the electric power networks could be contaminated with harmonic components due to nonlinear loads and switch converters. We built a numerical model to calculate transport ac loss in a bifilar stack composed of two coated conductors, carrying distorted current, by means of H-formulation. We compared the calculated losses in the bifilar stack exposed to nonsinusoidal current with the third and fifth harmonics plotted as a function of total harmonic distortion (THD), where THD is defined as the ratio of current magnitudes for the harmonic frequency and fundamental frequency, I hf,peak /I ff,peak . AC loss results in the bifilar stack carrying current with the third harmonic in each conductor were compared with those in an inductive stack and single tape carrying the same current as the conductors in the bifilar stack. Results show that harmonic components have substantial influence on ac loss in the bifilar stack. AC loss values in the stack with fifth harmonic increased monotonically with increasing THD, while ac loss value in the stack with the third harmonic had minimum value when THD is approximately 0.2.

Cooperative Operation of R-SFCL and Online Current Limitation Strategy of GCPVS Under Asymmetrical Faults

Grid-connected photovoltaic systems (GCPVS) should remain grid-connected and inject specified reactive current in accordance with fault-ride-through requirements. To minimize voltage ripples on the dc link voltage and restrict the maximum phase currents, a modified online current limitation strategy (OCLS) is presented in this paper. Transient performance of GCPVS is enhanced as resistive-type superconducting fault current limiter (R-SFCL) is applied under severe asymmetrical faults. By introducing proper resistance selection process, the cooperative operation of OCLS and SFCL is proved to be valid in performance improvement.

Cooperative Control of SFCL and SMES for Protecting PMSG-Based WTG<roman>s</roman> Under Grid Faults

To meet the requirement of grid codes about low voltage ride through (LVRT) of wind turbine generators (WTGs), a cooperative control scheme of resistor-type superconducting fault current limiter (SFCL) and superconducting magnetic energy storage (SMES) for improving the LVRT capability and transient stability of permanent magnetic synchronous generator (PMSG) based WTGs is investigated in this paper. In the proposed scheme, the SFCL is utilized to increase the output active power from grid side converter (GSC) to half of the pre-fault value, and the other half is absorbed by SMES so as to reduce its maximum energy storage capacity. In addition, a SFCL's resistance estimation method is introduced by using the grid-side voltage phasor relation that is established based on the grid voltage vector oriented control of GSC. Finally, a PMSG-based WTG integrated with the SMES and SFCL is built in PSCAD/EMTDC. Performance evaluations and comparisons demonstrate the advantages of the proposed scheme in improving the transient stability of PMSG and reducing the capital cost for superconducting devices.

Influencing Factors on Quench and Recovery of YBCO Tapes for DC Superconducting Fault Current Limiter

Quench and recovery characteristics are the most important characteristics of dc resistive type superconducting fault current limiters (SFCLs). In the normal state, the superconducting tapes of SFCLs stay in superconducting state without power loss. However, if there is a thermal disturbance energy impact to the superconducting tapes, the tapes may be quenched, and sometimes even break once their temperature is too high. After the thermal disturbance, the tapes may recover to superconducting state again. A numerical analysis method was proposed to analyze quench propagation and recovery characteristics of the YBa 2 Cu 3 O 7-δ tapes based on thermal conduction theory. The objective of this paper is to obtain the influencing factors such as magnitude of thermal disturbance, transport current, material of the stabilized layer and cooling on quench, and recovery properties of dc resistive type SFCL. Numerical analysis results show that the temperature and voltage of the tape increased while the transport current through the tape and the magnitude of thermal disturbance increased. The quench propagation velocity was higher and the recovery time was shorter for copper stabilized layers than stainless steel stabilized layers.

Effects of Short Circuit Currents on Quench and Recovery Properties of YBCO Tapes for DC SFCL

Short circuit currents show an upward trend in multi-terminal high voltage (MTHV) dc systems. DC resistive type superconducting fault current limiters (SFCLs) can limit short circuit currents to a much lower level to improve the stability of MTHV dc systems. Superconducting tapes used for dc SFCL will quench after a short circuit current attack. Then temperature and voltage of the tapes will increase. The objective of this paper is to obtain the effects of short circuit currents on quench and recovery properties of the superconducting tapes of dc resistive type SFCLs. YBa 2 Cu 3 O 7-δ (YBCO) tapes was chosen as investigation samples. This paper concluded that for higher short circuit currents, the temperature and the voltage of the tape was higher. The highest temperature was 379.2 K for YBCO tapes when a short circuit current of 10 kA was applied for 50 ms. Recovery time of a short circuit current of 10 kA was 240 ms longer than the recovery time of the short circuit current of 500 A. Quenched resistance curves gotten by experiments and analysis were similar, which proved the accuracy of the analysis.

Influences of the Resistive SFCL on the Incremental Power Frequency Relay of Transmission Lines

© 2019 IEEE. The superconducting fault-current limiter (SFCL) has been effective in coping with large fault currents and is expected to be largely applicated in the power system to solve the problem of increasing fault-current level in power grid nowadays. However, the coordination between SFCLs and traditional power system devices such as protective relaying has not been researched enough. This paper studies the influences of the resistive-type SFCL on the incremental power frequency relay of the transmission lines. The resistive SFCL is simulated by using thermal-electric analog method. A model of a 220-kV transmission system with the incremental power frequency relay element was built and simulated with the SIMULINK MATLAB software. Three compensation methods to eliminate the negative effects of the integration of SFCL are proposed and compared. Finally, numerical simulation tests have demonstrated the correctness and validity of theoretical analyses.

Study of Resistive-Type Superconducting Fault Current Limiters for a Hybrid High Voltage Direct Current System.

In this paper, a hybrid high voltage direct current transmission system containing a line commutated converter and a voltage source converter is developed. To enhance the robustness of the hybrid transmission system against direct current short-circuit faults, resistive-type superconducting fault current limiters are applied, and the effectiveness of this approach is assessed. Related mathematical models are built, and the theoretical functions of the proposed approach are expounded. According to the transient simulations in MATLAB software, the results demonstrate that: (i) The superconducting fault current limiter at the voltage source converter station enables to very efficiently mitigate the fault transients, and owns an enhanced current-limiting ability for handling the short-line faults. (ii) The superconducting fault current limiter at the line commutated converter station is able to mildly limit the fault current and alleviate the voltage drop, and its working performance has a low sensitivity to the fault location. At the end of the study, a brief scheme design of the resistive-type superconducting fault current limiters is achieved. In conclusion, the application feasibility of the proposed approach is well confirmed.

Fabrication and Tests of a Resistive-Type Superconducting Fault Current Limiter Module Based on Coated Conductors

The resistivetype superconducting fault current limiter (R-SFCL) is simple in structure, near zero impedance at normal state and can be quickly triggered by the fault current. Thus, it is a possible solution to limit the fault current in the power grid. In this paper, we report the fabrication and test for an R-SFCL module The R-SFCL module consists of seven bifilar coils connected in parallel, which were wound with two parallel 2G tapes. A 5mm spacer was co-wound between adjacent turns to act as the highvoltage insulation. In the tests, we test the current distribution among the bifilar coils, and then simulated short-circuit tests were conducted on the module to obtain its performance under fault current surge.

Protection strategy for multi‐terminal high‐voltage direct current grids using SFCLs at converter station output

This study proposes a non-selective protection strategy for multi-terminal high voltage direct current grids based on resistive-type superconducting fault current limiters (SFCLs). Located at the output of AC/DC converters, the SFCL limits the current contribution from the AC grid in case of DC fault. With this approach, the fault clearing time constraint is relieved allowing the use of mechanical DC circuit breakers for fault current interruption. Furthermore, the breaking capability and energy dissipation requirements of the breaker are greatly reduced. To achieve a fast restoration of the DC grid, a redundant SFCL is introduced in parallel to those in operation, bypassing them when the fault is effectively suppressed. In addition, primary and back-up protection schemes are described and tested using a three-terminal bipolar high voltage direct current (HVDC) grid based on half-bridge modular multilevel converters and cable transmission. Simulations are implemented in EMTP-RV® to analyse and discuss performances of the proposed fault clearing strategy.

A novel current-limiting circuit based on resistive-type SFCL for fault in DC power system

Reliability and security are essential concerns in DC power system. However, due to the limited capacity of DC circuit breaker (DCCB), the rapidly growing fault current cannot be reliably interrupted. Thus the reliability of the DC power system cannot be guaranteed. In this paper, a novel current-limiting circuit based on resistive-type superconducting fault current limiter (R-SFCL) is proposed to restrain fault current. The operation procedure of the proposed current-limiting circuit is presented in detail. Then, a detailed mathematical model of opening process is established to analyse parameter design. Finally, the simulation results verify the effectiveness of this circuit. Compared with the traditional current limiting solutions, the proposal can effectively limit the fault current to achieve a more reliable breaking serious fault, and the reliability of DC system can be improved. Furthermore, overvoltage on DCCB is also prevented so that the arrester can be cancelled.

Recovery characteristics of YBCO tapes against DC over current impulse

With the fast development of voltage source converter based high voltage direct current (VSCHVDC) power system, an effective fault current method is in demand. In HVDC systems, the short-circuit current generally exceeds the capacity of the fast circuit breaker. Meanwhile, a superconducting fault current limiter (SFCL) is able to limit the short circuit current level. If installed in an overhead line system, SFCL has to meet the requirement of the reclosing time. The fault current is much larger than the critical current of superconducting tapes, which generates huge heat and the temperature of the tapes in the resistive type SFCL will increase sharply. After removing the fault, the tapes need certain time to recover to the superconducting state. Thus, the recovery characteristics in DC faults are an important feature of the resistive type SFCL, and they are mainly determined by the corresponding features of the superconducting tapes. In this paper, a method is presented to measure the recovery time under transient DC over current impulse. The recovery characteristics of high temperature superconducting (HTS) tapes under transient DC over current impulse are studied. The recovery time under different impulse duration and different impulse amplitude are measured by experiments. The influence factors of the recovery characteristics are discussed, which will be useful for the design of SFCL.

Step-by-step design of a single phase 3.3 kV/200 a resistive type superconducting fault current limiter (R-SFCL) and cryostat

In our first attempt to design a single phase R-SFCL in India, we have chosen the typical rating of a medium voltage level (3.3 kVrms, 200 Arms, 1Φ) R-SFCL. The step-by-step design procedure for the R-SFCL involves conductor selection, time dependent electro-thermal simulations and recovery time optimization after fault removal. In the numerical analysis, effective fault limitation for a fault current of 5 kA for the medium voltage level R-SFCL are simulated. Maximum normal state resistance and maximum temperature rise in the SFCL coil during current limitation are estimated using one-dimensional energy balance equation. Further, a cryogenic system is conceptually designed for aforesaid MV level R-SFCL by considering inner and outer vessel materials, wall-thickness and thermal insulation which can be used for R-SFCL system. Finally, the total thermal load is calculated for the designed R-SFCL cryostat to select a suitable cryo-refrigerator for LN2 re-condensation.

Active Quenching Technique for YBCO Tapes: Quench Acceleration and Protection

The application of resistive-type superconducting fault current limiters (RSFCLs) in electrical networks is very attractive due to their relative compactness, light weight, and good performance. However, this technology still has drawbacks: asymmetrical quench, uncertain limiting velocity, passive action and incapability of enlarging capacity. Here, we present an active quenching technique which can potentially solve these problems. The quenching process is triggered using high-frequency (HF) AC fields, which are generated by two coupled copper coils attached on both sides of the YBCO sample. Our experiments show that this approach is effective in guaranteeing uniform quench and therefore is expected to be able to significantly extend the service life of the device. Moreover, the quench speed can be considerably increased by the HF field. We find that the performance of acceleration is positively correlated to the transport current, intensity and frequency of the AC field. In addition, a DC magnetic field is added around the sample holder simultaneously with the AC field, to study the field-angular-frequency dependence of the quench time t(BACfACBDC\U0001d703DC). Experimental results prove that the DC magnetic field can cooperate with the HF AC field to accelerate quench, which means better performance can be produced with lower costs with the two fields acting together. In all, this technique showed outstanding performance regarding quench acceleration and tape protection. We believe the HF-assisted quenching technology has a promising future in current-limiting devices and hope our findings could be helpful for its potential applications.

Direct-Current Vacuum Circuit Breaker With Superconducting Fault-Current Limiter

The objective of this paper is to propose a dc current interruption technology for railway dc traction systems, consisting of a dc vacuum circuit breaker with a superconducting fault-current limiter (SFCL). To this end, a 1.5-kV dc circuit breaker prototype is designed, involving a dc vacuum circuit breaker and a resistive-type SFCL serially connected. The dc vacuum circuit breaker is developed with a commutation circuit to generate a reverse injection current, and the resistive-type SFCL is composed of yttrium barium copper oxide superconducting tape. An LC current source tested the 1.5-kV prototype, showing that, when the precharged capacitor voltage is 1.5 kV, the prospective current is 47 kA increasing at a rate of 9.4 A/μs. The SFCL limits this current to ~3 kA (peak value), and then, decreases the current to 2 kA after 6 ms, followed by successful clearance via the dc vacuum circuit breaker. The proposed 1.5-kV circuit breaker will successfully clear short-circuit faults up to 47 kA by first limiting the prospective current and then interrupting it.

Technical and Economic Analysis of the R-Type SFCL for HVDC Grids Protection

Mainly used in ac grids, resistive-type superconducting fault current limiters may be still more interesting for dc systems due to their capability to reduce high short circuit currents appearing in case of dc cable fault. This limiter reduces the breaking capability, speed, and energy requirements of the required dc circuit breaker allowing the implementation of electromechanical breakers for fault current interruption. These breakers have lower breaking capability, on-load losses, and investment costs in comparison with hybrid circuit breakers based on power electronics. This paper presents a technical and economic analysis of a superconducting fault current limiter used in a radial three-terminal high voltage dc grid to protect a cable link. Based on simulation studies using an electromagnetic transient program, an effective system protection will be demonstrated with special attention to the continuity of power flow through healthy parts of the grid.