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Applied Superconductivity, IEEE Transactions on

Popular Articles (November 2014)

Includes the top 50 most frequently downloaded documents for this publication according to the most recent monthly usage statistics.
  • 1. Cooperative Control of SFCL and SMES for Enhancing Fault Ride Through Capability and Smoothing Power Fluctuation of DFIG Wind Farm

    Article#: 5400304
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (832 KB) |  | HTML iconHTML  

    This paper deals with a cooperative control of a resistive type superconducting fault current limiter (SFCL) and a superconducting magnetic energy storage (SMES) for enhancing fault ride through (FRT) capability and smoothing power fluctuation of the doubly fed induction generator (DFIG)-based wind farm. When the system faults occur, the SFCL is used to limit the fault current, alleviate the terminal voltage drop, and transient power fluctuation so that the DFIG can ride through the fault. Subsequently, the remaining power fluctuation is suppressed by the SMES. The resistive value of the SFCL as well as the superconducting coil inductance of the SMES are simultaneously optimized so that a sudden increase in the kinetic energy in the DFIG rotor during faults, an initial stored energy in the SMES coil, an energy loss of the SFCL, and an output power fluctuation of the DFIG are minimum. The superior control effect of the cooperative SFCL and SMES over the individual device is confirmed by simulation study. View full abstract»

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  • 2. Improving Low-Voltage Ride-Through Performance and Alleviating Power Fluctuation of DFIG Wind Turbine in DC Microgrid by Optimal SMES With Fault Current Limiting Function

    Article#: 5700805
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (877 KB) |  | HTML iconHTML  

    The vital problems of doubly fed induction generator (DFIG) wind turbine are power fluctuation and low-voltage ride-through performance. To tackle both problems, the new circuit configuration and optimization technique of the superconducting magnetic energy storage with fault current limiting function (SMES-FCL) in a DC microgrid are presented. The SMES-FCL circuit mainly consists of two DC choppers with common superconducting coil (SC). During normal operation, the SMES-FCL acts as the SMES unit to suppress the power fluctuation of DFIG. When severe faults occur in the system, the SC is automatically connected to the system and used as the fault current limiter. Consequently, the fault current and the terminal voltage drop of DFIG can be alleviated. The energy function method is used to formulate the optimization problem of SC inductance, initial stored energy, and proportional-integral control parameters of choppers. Simulation study confirms the superior control effect of the SMES-FCL over the conventional SMES. View full abstract»

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  • 3. Recent Developments in High-Temperature Superconducting Magnet Technology (Review)

    Article#: 4602412
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2215 KB) |  | HTML iconHTML  

    The use of magnets made of high temperature superconductors (HTS) such as BSCCO and REBCO easily provide higher magnetic fields and higher operating temperatures, enabling dramatic improvements in superconducting magnet technology. The LTS magnet technology is very well summarized in text books written by M. N. Wilson (Superconducting magnets, Clarendon Press Oxford, 1983) and Y. Iwasa (Case studies in superconducting magnets, 2nd edition, Springer, 2009), covering such topics as stability, protection, ac loss and so forth. To the contrary, HTS conductors were commercialized only recently and therefore the magnet technology for HTS conductors remains undeveloped, especially so in the case of REBCO conductors. The technological problems for HTS coils thus far encountered are 1) an enormous effect of a screening current-induced magnetic field, 2) degradation in the coil performance due to excessive mechanical stresses applied along the longitudinal and transverse direction, and 3) the difficulty in protecting the magnet in the case of an abrupt thermal runaway. This paper reviews recent progress in overcoming these technological problems for HTS magnets. Both BSCCO and REBCO conductors have been used for HTS magnets in areas such as high field facilities, NMR, MRI, magnetic levitation trains and so forth. The effect of the screening current is the major problem for NMR, MRI, and accelerators, as it substantially distorts spatial field homogeneity and temporal field stability; on the other hand, degradation due to excessive stresses is substantial for high field magnets. Additionally, coil protection is a common and substantive problem among high current density HTS magnets in general. World-wide activities in developing BSCCO and REBCO magnets are overviewed in this paper. View full abstract»

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  • 4. Feasibility Analysis of the Positioning of Superconducting Fault Current Limiters for the Smart Grid Application Using Simulink and SimPowerSystem

    Page(s): 2165 - 2169
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (644 KB) |  | HTML iconHTML  

    One of the most important topics regarding the application of superconducting fault current limiters (SFCL) for upcoming smart grid is related to its possible effect on the reduction of abnormal fault current and the suitable location in the micro grids. Due to the grid connection of the micro grids with the current power grids, excessive fault current is a serious problem to be solved for successful implementation of micro grids. However, a shortage of research concerning the location of SFCL in micro grid is felt. In this work, a resistive type SFCL model was implemented by integrating Simulink and SimPowerSystem blocks in Matlab. The designed SFCL model could be easily utilized for determining an impedance level of SFCL according to the fault-current-limitation requirements of various kinds of the smart grid system. In addition, typical smart grid model including generation, transmission and distribution network with dispersed energy resource was modeled to determine the location and the performance of the SFCL. As for a dispersed energy resource, 10 MVA wind farm was considered for the simulation. Three phase faults have been simulated at different locations in smart grid and the effect of the SFCL and its location on the wind farm fault current was evaluated. Consequently, the optimum arrangement of the SFCL location in Smart Grid with renewable resources has been proposed and its remarkable performance has been suggested. View full abstract»

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  • 5. Integrated SMES Technology for Modern Power System and Future Smart Grid

    Article#: 3801606
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (613 KB) |  | HTML iconHTML  

    Superconducting magnetic energy storage (SMES) technology has been progressed actively for use in modern power system. Principal application schemes of a sole SMES system, a hybrid energy storage system (HESS) consisting of small-scale SMES and other commercial energy storage systems (ESSs), a distributed SMES (DSMES) system, and a distributed HESS (DHESS) are presented and compared. The concept of the SMES-based HESS provides an economical way to apply medium-scale SMES systems in daily load leveling and to apply small-scale SMES systems in power quality improvement. A dc power distribution network case with superconducting dc cables and SMES devices is conceptually designed to evaluate the performance of the proposed four SMES application schemes. The results show that the novel concept of the SMES-based DHESS can be particularly expected to achieve efficient and economical power management. Finally, the application prospects and possible schemes implanting SMES devices for power generation, transmission, distribution and utilization are explored for use in future smart grid. View full abstract»

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  • 6. Wind and Ocean Power Generators

    Article#: 5200407
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (560 KB) |  | HTML iconHTML  

    We give an overview of wind and ocean power generation methods. Wind generation is now an established large global business while ocean generation is still in the prototype stage of development. The most important parameter for commercial acceptance of these technologies is the levelized cost of electricity produced by them. We discuss areas necessary for further cost improvement of wind generation. We further discuss the types of electrical generators used in these applications. View full abstract»

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  • 7. Overcurrent Protection Coordination in a Power Distribution Network With the Active Superconductive Fault Current Limiter

    Article#: 5602004
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (837 KB) |  | HTML iconHTML  

    The active saturated iron-core superconducting fault current limiter (SISFCL) is one of the best solutions to coping with high fault current levels and may be helpful in building future smart distribution networks. The application of an SISFCL in a distribution system can reduce the fault current to an acceptable level when a short-circuit fault occurs at different positions. The operational principle and the current-limiting characteristic of an active SISFCL are briefly introduced in this paper. The influence of an active SISFCL on the conventional inverse and definite time-delay overcurrent protective relays is discussed. In order to maintain reliable operation of the distribution system with an SISFCL, the protection coordination and setting solution is proposed. A model of a real 35-kV distribution system with an active SISFCL was built and simulated with the Electro-Magnetic Transients Program including DC software. Simulation tests have demonstrated the correctness and validity of theoretical analyses. View full abstract»

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  • 8. Study on Application Method of Superconducting Fault Current Limiter for Protection Coordination of Protective Devices in a Power Distribution System

    Article#: 5601504
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (724 KB) |  | HTML iconHTML  

    In this paper, the application method of super- conducting fault current limiter (SFCL) for the protection coordination of the protective devices in a power distribution system was analyzed. The SFCL has been announced as better solution among many methods to limit a fault current effectively, which has continuously increased due to more complex network of a power system. However, the application of the SFCL in a power system affects the operation of the protection devices and the protection coordination, which requires the study on the protection coordination of the protective devices considering the application of the SFCL in a power distribution system. In this paper, the methods to maintain the protection operation of the protective devices due to the SFCL's application in a power distribution system were investigated through some case studies considering the time current curve (TCC) of the protection relay. The setting current and the lever among the setting parameters of the protective devices to keep the protection coordination in a power system with a SFCL were selected. Through the analysis on the TCC curves, the higher pick up current and the lower time lever values could be confirmed for protection coordination in case that the SFCL was introduced in the power system with the fixed impedance of the SFCL. View full abstract»

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  • 9. Towards 32-bit Energy-Efficient Superconductor RQL Processors: The Cell-Level Design and Analysis of Key Processing and On-Chip Storage Units

    Article#: 1300408
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (413 KB)  

    New superconductor single flux quantum logics with no static power dissipation in bias resistors, such as Reciprocal Quantum Logic (RQL), offer opportunities to create energy-efficient superconductor processors operating at high frequencies with ultra-low power consumption. This paper discusses the results of our work on the cell-level design and analysis of a benchmark set of 32-/64-bit RQL processor integer and floating-point units such as adders, multipliers, an arithmetic-logic unit, and an array shifter, as well as small 1–4 Kbit RQL on-chip storage components such as register files, on-chip memory, and the top level caches. Our layout-aware design process includes the complete cell-level design and approximate physical layout of the circuits followed by the VHDL simulation, verification, and energy profiling using our RQL VHDL cell library tuned to the future MIT Lincoln Laboratory 10 $hbox{kA/cm}^{2}$ 248 nm process with 10 Nb metal layers and the minimum JJ critical current of 38 $muhbox{A}$. Our designs have the energy efficiency of $sim$1.0 single-precision TFLOPS/W and $sim$0.5 double-precision TFLOPS/W for floating-point units, and $sim$1–24 TOPS/W for 32-bit integer units at room temperature using the cryocooling efficiency of 0.1 $%$ (1000 W/W). The 1–4 Kbit 32-/64-bit multi-ported scratchpad memory, register files, write-through and write-back caches designed with RQL Non-Destructive Read-Out storage cells have the average energy consumption of 3.0–9.5 fJ/bit/operation at room temperature using the c- yocooling efficiency of 0.1 $%$. While these results are very promising, more work is needed to evaluate the contribution of the energy costs of instruction scheduling and off-chip main memory access to the energy efficiency of RQL computing across a whole system. View full abstract»

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  • 10. Design and Analysis of a New Magnetic Gear With Multiple Gear Ratios

    Article#: 0501904
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (513 KB) |  | HTML iconHTML  

    This paper proposes a new magnetic variable gear which offers different speed ratios. In order to provide the gear-ratio-changing ability, a high-remanence low-coercivity permanent magnet (PM), namely the aluminum-nickel-cobalt (Alnico), is utilized. By incorporating the concept of the magnetic gear and the concept of memory machine, a new double-deck structure of the stationary ring is developed to locate the magnetizing winding which can dynamically magnetize or demagnetize the Alnico PM. By using finite element analysis, the electromagnetic performance of the proposed magnetic gear at different gear ratios is analyzed. Hence, the corresponding validity can be verified. View full abstract»

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  • 11. Design of a High-Power Superconducting Filter With Novel DGS Structures

    Article#: 1500905
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (547 KB) |  | HTML iconHTML  

    A novel defected ground structure (DGS) resonator with improved power handling capability is proposed in this paper. The current density distribution of the DGS resonator is simulated and compared with that of the complete ground structure (CGS) resonator. Simulation shows that the maximum current density of the DGS resonator is lower than that of the CGS resonator. Two four-pole bandpass high-temperature superconducting filters centered at 2.9 GHz with a fractional bandwidth of nearly 1.5% are designed and fabricated using the DGS and CGS resonators, respectively. The measured maximum handling power is 37.3 dBm for the DGS filter at 77 K, which is higher than that of 34.1 dBm for the CGS filter. View full abstract»

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  • 12. Design and Evaluation of Flash ADC

    Article#: 1400205
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1548 KB)  

    We have designed single-bit comparators and multi-bit flash analog-to-digital converters (ADCs) using three flavors of periodic comparators; one flavor uses a differential “quasi-one-junction” SQUID (DQOS) comparator, the second use a differential SQUID wheel comparator (DSW) and the third uses a symmetric differential SQUID wheel comparator (SDSW) with time-interleaved clocks. We have also developed a new performance analysis scheme that enables full reconstruction of input signal using a single-bit comparator. The signal is reconstructed based on multiple beat frequency measurements that track the position of the comparator thresholds in response to a dc offset to the input signal. In addition, to eliminate the frequency dependent distortions resulting from impedance mismatches over wide bandwidths, the signal and clock distribution network have been optimized using EM simulations. For distributing the clock signal to the multi-bit comparators, a 50 $Omega$ coplanar transmission line has been designed. Test results for a 1-bit DSW comparator demonstrates a performance of 4.5 bits of resolution in Gray code for a beat frequency test using a 20 GHz input signal and 5.3 bits for 10 GHz input. 4 and 8-bit versions of the flash ADC with a DQOS comparator and a 3-bit time-interleaved ADC using the SDSW comparator have also been designed. The DQOS ADC has been tested up to 25 GHz input signal frequency with performance of 4.3 bits of resolution in Gray code for 19.7 GHz input signal. The time-interleaved ADC performance is 4.3 bits for a 15 GHz beat frequency test with an effective sampling rate of 30 GHz. View full abstract»

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  • 13. Characterization of 4 K CMOS devices and circuits for hybrid Josephson-CMOS systems

    Page(s): 267 - 271
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB) |  | HTML iconHTML  

    Characterization and modeling of CMOS devices at 4.2 K are carried out in order to simulate low-temperature operation of CMOS circuits for Josephson-CMOS hybrid systems. CMOS devices examined in this study have been fabricated by using 0.18 μm, 0.25 μm, and 0.35 μm commercial CMOS processes. Their static I-V characteristics and capacitances are measured at 4.2 K to establish the low-temperature device model based on the BSIM3 SPICE model. The propagation delays of CMOS inverters measured by using ring oscillators agree well with the simulation results. The experimental results indicate about 40% speedup from 300 K to 4.2 K. A three-transistor DRAM cell for a Josephson-CMOS hybrid memory is also investigated at low temperature. The temperature dependence of the retention time shows an exponential increase at low temperatures. Based on the low-temperature CMOS device model, we have developed short-delay CMOS amplifiers, which would amplify a 40 mV voltage input to CMOS voltage level with the propagation delay of about 100 ps, assuming the use of a 0.18 μm CMOS process. We have measured the propagation delay of the CMOS amplifier by using a single-flux-quantum (SFQ) delay measurement system. This is a complete demonstration of the signal exchanges between SFQ and CMOS circuits at 4.2 K. View full abstract»

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  • 14. Synergistic Control of SMES and Battery Energy Storage for Enabling Dispatchability of Renewable Energy Sources

    Article#: 5701205
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (696 KB) |  | HTML iconHTML  

    The use of renewable energy source can reduce greenhouse gas emission and fossil fuel pollution. Compared with fossil fuel energy, renewable energy is not stable and cannot supply firm electrical output (i.e., it is nondispatchable). Fluctuating power from renewables may result in grid power oscillation. To reduce grid swing, energy storage is necessary to smooth output from renewable energy. Energy storage with high energy density and fast response time or high power capacity is desired for compensation of fluctuating output. Generally, superconducting magnetic energy storage (SMES) has higher power capacity than battery energy storage, while battery provides higher energy density. Thus, this research proposes a hybrid energy storage system (HESS) composed of an SMES and battery. Novel and practical synergistic control is presented for firming power fluctuation by exploiting the strong power and energy capabilities of the SMES and the battery while within the efficient operating range of (i.e., state of charges of) HESS. Comprehensive case studies demonstrate the efficacy of the proposed HESS topology and control algorithm using PSCAD/EMTDC. View full abstract»

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  • 15. High-Specific-Capacitance Supercapacitor Based on Vanadium Oxide Nanoribbon

    Article#: 7000204
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (517 KB) |  | HTML iconHTML  

    A variety of storage technologies for transmission grid and electric vehicle applications has been gaining importance in the last few years. The supercapacitor is one of the most viable energy storage devices. In this paper, a high-specific-capacitance supercapacitor with vanadium oxide nanoribbon electrode was fabricated. Vanadium oxide nanoribbon was synthesized by a facile and effective hydrothermal treatment with controlling the condensation speeds of precursors in the solution along the 〈010〉, 〈010〉, and 〈010〉 directions. The synthesis involved dissolution of V2O5 into H2O2, and investigation of the precursor weight ratio and the hydrothermal time. The product was characterized by using scanning electron microscopy, transmission electron microscope and X-ray. The electrochemical properties of the material as the electrode of electrochemical capacitor were evaluated by cyclic voltammetry in a three electrode system consisting of a saturated calomel electrode as reference electrode, platinum as a counter electrode and the active material as the working electrode. As far as we know, it is for the first time to report the fabrication of vanadium oxide nanoribbon by using the hydrothermal method. The prepared nanoribbon structure possesses relative short width and significant length. The narrow nanoribbon with ultra-length optimizes the ion diffusion path thereby enhancing the specific capacitance. A high capacitance of 453 F/g was obtained at the scan rate of 2 mV/s in 2 M NaCl electrolyte, and it still maintained a high capacitance of 201 F/g at a higher scan rate of 50 mV/s. And the nanoribbon exhibits faster ion propagation and better conductivity than the nanotube as revealed by the immediate current response to the potentials added on the electrode. The electrochemical performances of the vanadium oxide were found to strongly depend on the nanostructures and electrolytes. View full abstract»

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  • 16. Four-Pole Narrowband Superconducting Tunable Filter at VHF-Band

    Article#: 1501005
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (772 KB) |  | HTML iconHTML  

    This paper presents a narrowband superconducting tunable filter at very high frequency (VHF)-band with a fractional bandwidth of 1.4%. The effect of the resonator structure on the unloaded quality factor and frequency tuning range is analyzed and simulated. A shorted spiral resonator, with the inner end loaded with a gallium arsenide (GaAs) varactor through air bridges, is chosen for compact size, wide tuning range, and high quality factor. The interstage and external couplings of this resonator remain almost unchanged with the varactor capacitance. Thus, the filter keeps a constant fractional bandwidth in the entire tuning range. The four-pole tunable filter at VHF-band is successfully designed with a compact size of 30 mm × 14.6 mm. The measured results match well with the simulated results. The tuning range of the filter is 17%, from 193.9 to 229.8 MHz. The variation of the fractional bandwidth is within (1.40 ± 0.01)%. The insertion loss at 229.8 MHz is 0.32 dB, with a reverse bias voltage of 9 V. The unloaded quality factor of the resonators in the four-pole filter is estimated to be 5600 at 229.8 MHz. View full abstract»

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  • 17. Novel Linear Iteration Maximum Power Point Tracking Algorithm for Photovoltaic Power Generation

    Article#: 0600806
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1447 KB) |  | HTML iconHTML  

    A novel maximum power point tracking (MPPT) algorithm is proposed in this paper based on the linear iteration method for photovoltaic (PV) power generation for improving steady-state performance and fast dynamic response simultaneously. In this MPPT algorithm, linear prediction estimates the MPP of PV with a very high accuracy due to the constant-voltage and constant-current characters of PV. Then, further iterations for error correction are executed to get a better approximation to the MPP. Experiments verify theoretical analysis and demonstrate its fast dynamic response and high working efficiency. View full abstract»

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  • 18. High power density superconducting motor for all-electric aircraft propulsion

    Page(s): 2226 - 2229
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB) |  | HTML iconHTML  

    NASA conducts and funds research to advance the state of the art in aeronautics, including improvements in aircraft design leading to enhanced performance in areas such as noise, emissions, and safety. A particular initiative involves development of an all-electric aircraft requiring significant improvements in certain technologies. NASA has started a new project with one of the objectives being the development of enabling technologies for an all-electric aircraft. Electrical aeropropulsion requires the design of more compact and efficient electrical motors. In order to increase the power density, the weight/size must be minimized and the air gap flux density must increase significantly: the use of superconducting materials is an obvious choice. Existing HTS motors are proof-of-principle demonstrators and exhibit power densities lower than 1 HP/lb, which is too low to be considered in mobile systems. This paper deals with a preliminary electromagnetic design of a 200 HP high temperature superconducting motor optimized in terms of power density. The presented configuration is a synchronous motor with a nonconventional topology enhanced by HTS bulk material. The design targets the Cessna 172 propulsion requirements that are 200 HP at 2700 RPM. View full abstract»

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  • 19. Parameters Analysis and Optimization Design for a Concentric Magnetic Gear Based on Sinusoidal Magnetizations

    Article#: 0600905
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1499 KB) |  | HTML iconHTML  

    Concentric magnetic gears hold a promising future in the field of low speed and high torque. To obtain a sinusoidal distribution of air gap magnetic field, in this paper, exact 2-D analytical method is proposed to calculate the magnetic field distribution in a concentric magnetic gear with Halbach permanent-magnet arrays, and analyzes the relationship between the parameters and maximum static torque, the parameters include width of modulating ring core, height of modulating ring and thickness of outer rotor yoke. Compared air-gap magnetic field distributions computed by the analytical method with those obtained from the 2-D finite-element method (FEM), the analytical and the FEM results are in good accordance, which proves the proposed method is correct and effective. According to the results of parameters analysis, the concentric magnetic gear prototype is produced, which the numbers of pole pairs on the inner and outer rotors are 4 and 17, respectively. The test results show reasonable structural parameters can improve the torque density of magnetic gears, and the design of magnetic gear provides a useful reference. View full abstract»

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  • 20. Resistive Superconducting Fault Current Limiters are becoming a Mature Technology

    Page(s): 1
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (713 KB)  

    Resistive superconducting fault current limiters (rSFCL) are reliably reacting devices and excellent means to overcome issues of higher short circuit current levels resulting from added electricity generation and more interconnected networks. Due to the strong impedance increase of the superconductor components initiated by a fault and the very low reactance under all operating conditions the rSFCL technology is ideal for protection of electricity grids. Several rSFCL systems based on different superconductor materials have been designed, built, tested, and commissioned by Nexans SuperConductors at distribution grids of several DNOs and also two times at a power plant. A recently built system is operating together with a HTS cable to supply up to 40 MVA on 10 kV enabling a very compact cable design. First market opportunities for medium voltage SFCLs have been identified and fully commercial projects targeting at permanent installations are now becoming reality. Different development stages leading from first trial devices to real commercial systems are presented including further necessary steps for SFCLs getting close to serial production. View full abstract»

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  • 21. Reducing the Fault Current and Overvoltage in a Distribution System With Distributed Generation Units Through an Active Type SFCL

    Article#: 5600305
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (289 KB) |  | HTML iconHTML  

    For a power distribution system with distributed generation (DG) units, its fault current and induced overvoltage under abnormal conditions should be taken into account seriously. In consideration that applying superconducting fault current limiter (SFCL) may be a feasible solution, in this paper, the effects of a voltage compensation type active SFCL on them are studied through theoretical derivation and simulation. The active SFCL is composed of an air-core superconducting transformer and a PWM converter. The magnetic field in the air-core can be controlled by adjusting the converters output current, and then the active SFCLs equivalent impedance can be regulated for current-limitation and possible overvoltage suppression. During the study process, in view of the changes in the locations of the DG units connected to the system, the DG units injection capacities and the fault positions, the active SFCLs current-limiting and overvoltage-suppressing characteristics are both simulated in MATLAB. The simulation results show that the active SFCL can play an obvious role in restraining the fault current and overvoltage, and it can contribute to avoiding damage on the relevant distribution equipment and improve the systems safety and reliability. View full abstract»

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  • 22. New Hybrid Damping Strategy for Grid-Connected Photovoltaic Inverter With LCL Filter

    Article#: 0601608
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2436 KB) |  | HTML iconHTML  

    This paper investigates the damping performance of a grid-connected photovoltaic (PV) system with inductance-capacitor-inductance (LCL) filter and develops a hybrid damping strategies which is more robust to system parameter variations, processing delay and switching frequencies. Firstly, the comprehensive model including LCL filter, inverter and the grid are developed. Then the performance of passive damping and active damping under different grid impedances, processing delay and controller gains are investigated. Finally, a hybrid damping method combing both active and passive damping conditions is proposed. The new method can reduce the impact of processing delay and is more robust to grid impedance variations. Both simulations and experiments are provided to verify the effectiveness of the proposed method. View full abstract»

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  • 23. A Universal LabVIEW-Based HTS Device Measurement and Control Platform and Verified Through a SMES System

    Article#: 9002705
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1380 KB) |  | HTML iconHTML  

    This paper presents a computer-controlled test platform for superconducting magnetic energy storage (SMES) control and measurement based on the Laboratory Virtual Instrument Engineering Workbench (LabVIEW). The purpose is to achieve the fast control and friendly measurement simultaneously by integrating the LabVIEW and commercial digital control chips. The test platform mainly consists of three modules, i.e., power conditioning system (PCS) module, control module and measurement module. The PCS module imitates the operational conditions and characteristics of a practical SEMS device by using the combination of a programmable power source and an equivalent load network. A LabVIEW-based program is also designed to output various imitated charge-discharge current waveforms to directly supply the SMES magnet so as to avoid the use of the complicated and costly practical PCS. The measurement module has multi-functions of current-voltage (I-V), temperature and magnetic field measurements. In cooperation with the control module, the measured data are applied to adjust the real-time operational state of the PCS module and to protect the SMES magnet when the quench is detected. The test platform has been experimentally verified for the use in a small-scale SMES prototype. View full abstract»

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  • 24. Novel Decoupling Model-Based Predictive Current Control Strategy for Flux-Switching Permanent-Magnet Synchronous Machines With Low Torque Ripple and Switching Loss

    Article#: 0600705
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1505 KB) |  | HTML iconHTML  

    A flux-switching permanent-magnet synchronous machine (FSPMSM) has demonstrated merits of high torque density, strong mechanical robustness, good fault redundancy ability, etc., and begun to find great potential applications in electrical vehicle, airplane, ship, wind generation, and so on. However, by the inherited influence of double salient structure and high number of pole pairs, it suffers with comparatively large torque ripple and converter switching loss, which deteriorates the drive performance a little. Existing research mostly focuses on electromagnetic optimal design to reduce these defects, but little attention has been paid to advanced control strategies. In this paper, a novel model-based predictive current control algorithm with decoupling implementation is proposed to strengthen the drive performance of FSPMSM. One improved cost function has been used to find the best switching vector for the converter during each instant. Comprehensive theoretical analyses and simulations are carried out to validate the innovation feasibility. View full abstract»

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  • 25. Application Studies on the Active SISFCL in Electric Transmission System and Its Impact on Line Distance Protection

    Page(s): 1
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1151 KB)  

    The application of superconducting fault current limiters in transmission systems is very attractive because the devices offer superior technical performance in comparison to conventional methods to limit fault currents. The superconducting fault current limiters show high impedance during fault period and negligible impedance in the circuit during normal operating conditions. The paper illustrates the operation performance of the active saturated iron-core superconductive fault current limiter (SISFCL) and its current-limiting effect on a transmission system. Besides, investigations are carried out to explore the impact of the active SISFCL on the distance protection of the transmission line. Novel principle and application solutions are first proposed to eliminate the adverse effects that the active SISFCL has on the distance relay protection. A 500kV double-circuit transmission system with active SISFCLs is simulated by using Electro-Magnetic Transients Program including DC (EMTDC) software package. Results from simulation tests have demonstrated the correctness and validity of theoretical analyses. View full abstract»

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  • 26. New Concept for Flywheel Energy Storage System Using SMB and PMB

    Page(s): 1485 - 1488
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (595 KB) |  | HTML iconHTML  

    Since a few years ago, electrical energy storage has been attractive as an effective use of electricity and coping with the momentary voltage drop. Above all, flywheel energy storage systems using superconductor have advantages of long life, high energy density, and high efficiency. Our experimental machine uses a superconducting magnetic bearing (SMB) together with a permanent magnet bearing (PMB) and plans to reduce the overall cost and cooling cost. Flywheel energy storage systems operate by storing energy mechanically in a rotating flywheel. The generating motor is used to rotate the flywheel and to generate electricity from flywheel rotation. The generating motor consists of a 2-phase 4-pole brushless DC motor and a Hall sensor. A purpose of this study is the development of a compact flywheel energy storage system using SMB and PMB with new concept. This paper shows the new model of flywheel by using the concept of yajirobei (balancing toy) that the center of gravity of mass is lower than supporting point. By using this concept, the flywheel has higher storage energy compared with conventional ones. Furthermore, we also purpose to improve and evaluate motor drive (DC motor) to increase the rotational speed, and estimate the system at momentary voltage drop. View full abstract»

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  • 27. Validity Analysis on the Positioning of Superconducting Fault Current Limiter in Neighboring AC and DC Microgrid

    Article#: 5600204
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (700 KB) |  | HTML iconHTML  

    In a smart grid, various kinds of distributed generation (DG) sources could be connected into the main power grid in order to enhance the reliability of the power system. The combination of ac and dc distribution grid are also considered for the efficient connection of renewable power resources. In this case, one of the critical problems due to these integrations is the excessive increase in the fault current because of the presence of DG within the smart grid. In order to protect the smart grid from increasing fault current, a superconducting fault current limiter (SFCL) could be applied, which has negligible power loss and capability to limit initial fault currents effectively. This paper presents feasibility analysis results of the positioning of the SFCL and its effects on reducing fault current in a smart grid having ac and dc microgrid. The detailed power system was implemented with a microgrid having wind farm and low voltage dc grid connected with a photovoltaic farm. Transient analyses were performed for the worst case faults with the different SFCL arrangements. The strategic location of SFCL in the power grid, which could limit fault currents and has no negative effect on the DG sources, was found to be the connection point of integration of the each DG sources in the ac and dc microgrid. View full abstract»

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  • 28. Improving Fault Ride-Through Capability of DFIG-Based Wind Turbine Using Superconducting Fault Current Limiter

    Article#: 5601204
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (814 KB) |  | HTML iconHTML  

    With increased penetration of wind energy as a renewable energy source, there is a need to keep wind turbines connected to the grid during different disturbances such as grid faults. In this paper, the use of superconducting fault current limiter (SFCL) is proposed to reduce fault current level at the stator side and improve the fault ride-through (FRT) capability of the system. To highlight the proposed technique, a doubly fed induction generator (DFIG) is considered as a wind-turbine generator, where the whole system is simulated using PSCAD/EMTDC software. Detailed simulation results are obtained with and without SFCL considering stator and rotor currents. In addition, the voltage profile at the generator terminals is analyzed. The effect of limiting resistance value is also investigated. The obtained results ensure that the SFCL is effective in decreasing the fault current. Moreover, both the voltage dip at the generator terminals and the reactive power consumption from the grid are decreased during the fault. The voltage dip characteristics are discussed in accordance with international grid codes for wind turbines. View full abstract»

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  • 29. A Single-Phase AC Power Supply Based on Modified Quasi-Z-Source Inverter

    Article#: 0600205
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (997 KB) |  | HTML iconHTML  

    This paper presents a single-phase ac power supply circuit that based on modified voltage-fed quasi-Z-source inverter topology; it suits to the light or the heavy load and is fit for the resistive, inductive, or capacitive load. The topology, operating principle, voltage gain, control method, and its realization by DSP are described in this paper. The feasibility and rationality of the system is verified by the simulation and experimental results. View full abstract»

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  • 30. Study on Switching Overvoltage in Off-Shore Wind Farms

    Article#: 0601005
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (926 KB) |  | HTML iconHTML  

    The transformers often suffer the insulation breakdown accident caused by overvoltage in some wind farms and the problem has become particularly prominent. The switching overvoltage is considered to be an important cause to insulation accident. This paper will establish a wind farm model and research on the relationship between the switching overvoltage and the length of feeder cable and the number of feeders that have been energized. First, this paper establishes two dynamic simulation systems to analyze overvoltage of step-up transformers on feeder in PSCAD. Finally, making simulation and analyzing the overvoltage of step-up transformers on feeder. The simulation results show that switching overvoltage amplitude of electrical equipment in wind farm will increase with the increasing of the feeder length both in star and radial topology; moreover, the number of energized feeders will have influence on the amplitude and steepness of switching overvoltage. The results can provide some references for the insulation design of cable system and the step-up transformer in offshore wind farm. View full abstract»

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  • 31. Novel Concept of Dish Stirling Solar Power Generation Designed With a HTS Linear Generator

    Article#: 5203005
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (997 KB) |  | HTML iconHTML  

    A novel dish Stirling solar power generation (DSSPG) system has been designed incorporated with a high temperature superconducting (HTS) linear synchronous generator (LSG). The high efficient HTSLSG is a compact energy converter for a Stirling engine in the DSSPG system, where a duplex of Stirling cycles is applied, in which a Stirling engine replaces the conventional linear compressor forming a Stirling pulse tube refrigerator (SPTR). This paper presents the DSSPG system designed with the HTSLSG cooled by the duplex Stirling system, and analyzes the thermal load and power distribution in the system to provide bases for consideration of practical application. Analysis results show that the DSSPG system with the HTSLSG refrigerated by the SPTR powered by the DSSPG system itself can be realized, and has higher efficiency than that with the conventional LSG and has larger system capacity. View full abstract»

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  • 32. Modular Stator High Temperature Superconducting Flux-Switching Machines

    Article#: 0601405
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (990 KB) |  | HTML iconHTML  

    Flux-switching permanent magnet (FSPM) machines have advantages of robust rotor, strong permanent magnet (PM) dissipation ability, etc, but its flux-weakening capability is poor for its constant PM flux linkage. High temperature superconducting (HTS) excitation windings can produce higher flux density than PM excitation and modify the airgap flux density easily. But if the HTS coils are placed adjacent to the armature winding in the same slot, the heat produced by the armature winding is difficult to cool down. In this paper, a modular stator HTS flux-switching (HTS-FS) machine is first proposed, and the operation principle is described in details. Second, mathematical equations are proposed and detailed electromagnetic design has been done. Then, the optimization of width of flux barrier, rotor pole arc and split ratio have been made to get higher back-EMF, higher output torque capability, and lower torque ripple. Moreover, the comparisons of key performance indexes between HTS-FS machine and conventional FSPM machines have been made. The results show that the HTS-FS machine can produce higher back-EMF than FSPM machine, and at small armature current, it can produce higher torque with little electromagnetic saturation. View full abstract»

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  • 33. Computation of Losses in HTS Under the Action of Varying Magnetic Fields and Currents

    Article#: 8200433
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1703 KB) |  | HTML iconHTML  

    Numerical modeling of superconductors is widely recognized as a powerful tool for interpreting experimental results, understanding physical mechanisms, and predicting the performance of high-temperature-superconductor (HTS) tapes, wires, and devices. This is particularly true for ac loss calculation since a sufficiently low ac loss value is imperative to make these materials attractive for commercialization. In recent years, a large variety of numerical models, which are based on different techniques and implementations, has been proposed by researchers around the world, with the purpose of being able to estimate ac losses in HTSs quickly and accurately. This paper presents a literature review of the methods for computing ac losses in HTS tapes, wires, and devices. Technical superconductors have a relatively complex geometry (filaments, which might be twisted or transposed, or layers) and consist of different materials. As a result, different loss contributions exist. In this paper, we describe the ways of computing such loss contributions, which include hysteresis losses, eddy-current losses, coupling losses, and losses in ferromagnetic materials. We also provide an estimation of the losses occurring in a variety of power applications. View full abstract»

    Open Access
  • 34. Fault-Tolerant Routing Algorithm Simulation and Hardware Verification of NoC

    Article#: 9002805
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1016 KB) |  | HTML iconHTML  

    Various software and hardware faults can destroy data transmission on the network, so it is essential to study fault-tolerant methods of Network-on-Chip (NoC). In this paper, a modified fault-tolerant routing algorithm is proposed based on the XY algorithm, which can achieve an efficient route way by resetting the route rule when error occurred on the path of chain or between the nodes. This performance shows that the fault tolerant bypassed the fault path of chain or the error nodes. A hardware design of the modified fault-tolerant routing algorithm is also introduced, aimed at the elaborating of hardware structure principle and simulating of fault tolerant routing algorithm of NoC based on FPGA. The proposed algorithm was simulated and verified on the platform of ISE Design Suite 13.3. The simulation results showed that the proposed modified algorithm is feasible. Because of the algorithm, the overall performance has improved obviously without using virtual channel, especially for the area and power consumption. At last, the proposed algorithm was verified on the FPGA platform of Nexys2 multiple sets of validate data proved that the proposed modified algorithm was reliable and feasible, and the quality of this NoC performed very well. View full abstract»

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  • 35. The Inductrack: a simpler approach to magnetic levitation

    Page(s): 901 - 904
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    Arising out of research at the Lawrence Livermore National Laboratory on passive magnetic bearings, a new magnetic levitation system, the Inductrack, has been developed and tested at model scale. The system employs special arrays of permanent magnets (Halbach arrays) on the moving car. The magnetic field from the arrays induces repelling currents in a close-packed array of shorted circuits in the track. Above a low transition speed (a few kilometers per hour), levitation forces approach a constant value, while drag forces decrease inversely with speed, with L/D reaching 200:1 or more at operating speeds. The high magnetic efficiency of the Halbach arrays, plus the use of close-packed track circuits, results in levitating forces approaching 40 metric tonnes per square meter (using NdFeB permanent magnet arrays, whose weight in typical cases is a few percent of the levitated weight). The system is passively stable: only motion is required for levitation. Failure of the drive system only results in the train slowing down and settling onto auxiliary wheels at a low speed. A detailed theoretical analysis of the Inductrack was made, on the basis of which a small-scale model was constructed and operated. The Laboratory is building a new small-scale model system (under NASA sponsorship) to demonstrate the acceleration rates and speeds (10-g and Mach 0.4 in the model) needed to magnetically launch rockets. View full abstract»

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  • 36. Coordination of Superconductive Fault Current Limiters With Zero-Sequence Current Protection of Transmission Lines

    Article#: 5602105
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (880 KB) |  | HTML iconHTML  

    A 500 kV saturated iron-core superconductive fault current limiter (SISFCL) has been designed to be installed in an extra high voltage (EHV) transmission system in southern China. We carried out studies on compatibility and coordination problems in the application of this kind of device in an EHV network. In this paper, the operational principle of an SISFCL and the protection configuration of transmission lines are briefly introduced. The influence of an SISFCL on the zero-sequence current protection of the grid, taking into consideration both the fault of SISFCL itself and fault of the power lines, is discussed. In order to coordinate the SISFCL and the grid protection scheme, requirements and recommendations are proposed. A model of a 500 kV double-circuit transmission system with SISFCLs is built using Electromagnetic Transient Program including DC (EMTDC) software package. The simulation results are in good agreement with the theoretical analyses. View full abstract»

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  • 37. RSFQ logic/memory family: a new Josephson-junction technology for sub-terahertz-clock-frequency digital systems

    Page(s): 3 - 28
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2331 KB)  

    Recent developments concerning the rapid single-flux-quantum (RSFQ) circuit family are reviewed. Elementary cells in this circuit family can generate, pass, memorize, and reproduce picosecond voltage pulses with a nominally quantized area corresponding to transfer of a single magnetic flux quantum across a Josephson junction. Functionally, each cell can be viewed as a combination of a logic gate and an output latch (register) controlled by clock pulses, which are physically similar to the signal pulses. Hand-shaking style of local exchange by the clock pulses enables one to increase complexity of the LSI RSFQ systems without loss of operating speed. The simplest components of the RSFQ circuitry have been experimentally tested at clock frequencies exceeding 100 GHz, and an increase of the speed beyond 300 GHz is expected as a result of using an up-to-date fabrication technology. This review includes a discussion of possible future developments and applications of this novel, ultrafast digital technology.<> View full abstract»

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  • 38. Enabling High-Temperature Superconducting Technologies Toward Practical Applications

    Article#: 5400712
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1453 KB) |  | HTML iconHTML  

    This work covers the high-temperature superconducting (HTS) technologies based on the highlights in recent achievements in the applied HTS field in China. Its comprehensive coverage includes practical HTS material manufacturing and characterization, large-scale applications, and electronic applications. The applied HTS technologies have been well enabled to build applicable devices, and their characteristics have been well verified in the HTS devices developed to be industrialized for practical applications. The highlighted HTS devices and their performance details reveal the trend and the necessary improvement required to reach the goal of industrial applications of HTS technologies. View full abstract»

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  • 39. Thermal Analysis of 10-MW-Class Wind Turbine HTS Synchronous Generator

    Article#: 5202209
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (807 KB) |  | HTML iconHTML  

    In this paper, the thermal performance of a 10-MW-class wind turbine-based high-temperature superconducting (HTS) synchronous generator is studied. The proposed generator is designed and modeled through a finite-element method (FEM), and the generator losses, including iron losses and electrical losses, are obtained. As the output power substantially depends on thermal rising of the generator, heat transfer analysis of the proposed HTS generator is carried out using both lumped parameters network (LPN) and FEM analysis. Then, temperature distribution of the components of the machine is evaluated and discussed for different generator speeds. The proper temperature distribution guarantees the desirable operation of the generator. This paper shows that it is feasible to design a 10-MW-class HTS synchronous generator from thermal analysis point of view. View full abstract»

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  • 40. SMES Based Dynamic Voltage Restorer for Voltage Fluctuations Compensation

    Page(s): 1360 - 1364
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (287 KB) |  | HTML iconHTML  

    This paper presents a superconducting magnetic energy storage (SMES) based dynamic voltage restorer (DVR) to protect consumers from the grid voltage fluctuations. Due to the characteristic of high energy density and quick response, a superconducting magnet is selected as the energy storage unit to improve the compensation capability of DVR. This paper analyses the operation principle of the SMES based DVR, and designs the DVR output voltage control method. The control system mainly consists of two parts, the PWM converter controller and the DC/DC chopper controller. The PWM converter controller adopts double-loop control strategy, with an inner current regulator and an outer voltage controller. Combining the coordinated control of DC/DC chopper, the DVR can regulate output voltage accurately and quickly to compensate the system voltage fluctuations. Using MATLAB SIMULINK, the models of the SMES based DVR is established, and the simulation tests are performed to evaluate the system performance. View full abstract»

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  • 41. Sensor Fault Diagnosis of Superconducting Fault Current Limiter With Saturated Iron Core Based on SVM

    Article#: 5602805
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (867 KB) |  | HTML iconHTML  

    To improve reliability, a sensor fault diagnosis method of Support Vector Machine (SVM) is presented based on the control system model of superconducting fault current limiter (SFCL) with saturated iron core. It is used for the state estimation of the bias current of the excitation system. In this paper, the SVM is used to approximate the nonlinear function between ac voltage, ac current of SFCL, ac impedance of SFCL, and dc bias current. It is equivalent to an inverse model to estimate the dc bias current from the ac voltage, ac current, and ac impedance. If the error between estimated value of dc bias current and the sample value of current sensor is beyond some threshold value, it shows a fault occurs on the current sensor. Through simulations, this kind of sensor fault diagnosis method based on SVM is proved to be effective. View full abstract»

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  • 42. A New Internal Detection Method for Fluid Transportation Pipeline Leak Based on Active Electrolocation

    Article#: 0601705
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (519 KB) |  | HTML iconHTML  

    Pipeline leak internal inspection method is a key technology of safety assessment for industrial pipeline. Weakly electric fish can sense its surrounding environment by generating electric fields and detecting distortions through their active electrolocation system. In this paper, a new internal inspection leak method for fluid transportation pipeline, the active electrolocation internal inspection method, is proposed to pipe detection which is inspired by active electrolocation system of weakly electric fish. An experimental system for fluid transportation pipe leak detection based on active electrolocation has been constructed. To test the feasibility of this method and this experimental system's performance, the detecting property of this method with different working conditions for different material pipe, metallic and non-metallic pipes, were studied in this paper. And then, FFT (fast Fourier transformation) and joint time-frequency analysis was applied to analyze and process experimental data. FFT provides an available method to analyze the experimental results in the frequency domain at different point. Meanwhile, the joint time-frequency analysis method can achieve the observation any frequency component in the whole time domain. Finally, the positioning error and relative error of this method has been discussed and analyzed in this paper. In our study, experimental results show that leak spot in seamless steel pipe and PVC (polyvinyl chloride polymer) pipe with different working conditions can be effectively detected by the method. The internal inspection method for fluid transportation pipeline leak based on active electrolocation was validated by our study, which lays a foundation of a new online detection in pipe engineering field. A new internal inspection method for fluid transportation pipeline based on active electrolocation has been developed. View full abstract»

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  • 43. Novel Flux-Regulatable Dual-Magnet Vernier Memory Machines for Electric Vehicle Propulsion

    Article#: 0601205
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1390 KB) |  | HTML iconHTML  

    In this paper, two novel flux-regulatable dual-magnet vernier memory machines (DM-VMMs), which incorporate the flux-memorizable concept and vernier structure, are proposed and implemented as in-wheel motor drives for electric vehicle (EV) applications. The proposed dual-magnet configurations employ flux-modulated poles to perform large torque production in low-speed region, namely the “magnetic gearing” effect. Moreover, the flexible flux-controllability can be readily achieved to expand high-speed constant-power region by temporarily applying current pulse to magnetize/demagnetize aluminum-nickel-cobalt (AlNiCo) magnets. The configurations and operating principle of the two DM-VMMs with similar dimensions are discussed. The electromagnetic characteristics of the machines are comprehensively analyzed and quantitatively compared by time-stepping finite element method (TS-FEM) coupled with nonlinear parallelogram hysteresis model (NPHM), which verifies the feasibility of the proposed machine topologies. View full abstract»

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  • 44. Analysis of Unsymmetrical Faults in High Voltage Power Systems With Superconducting Fault Current Limiters

    Page(s): 2347 - 2350
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (498 KB) |  | HTML iconHTML  

    An analysis of unsymmetrical faults for a 110 kV sub-grid coupling with a superconducting fault current limiter is conducted in this contribution. For the design of the super-conducting fault current limiters it is essential to identify the highest possible voltage during the limitation process. As reference the symmetric three phase fault which generally leads to the highest short-circuit currents is used. Unsymmetrical faults like single line-to-ground fault, line-to-line fault and double line-to-ground fault are investigated in dependence of the superconducting fault current limiter impedance. The analysis shows that the double line-to-ground fault leads to the highest voltage drop during the limitation in the relevant range of impedance. Consequently, this fault is a crucial factor for the design of the superconducting fault current limiter. View full abstract»

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  • 45. Development and Application of the Maglev Transportation System

    Page(s): 92 - 99
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1156 KB) |  | HTML iconHTML  

    The development of the Maglev train is a very important achievement in passenger transportation for the 20th century. Based on the recent information this paper describes the development of different Maglev systems, the application of Maglev for passenger transportation, and the experience of promoting the Maglev transportation in China. View full abstract»

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  • 46. Next Generation More-Electric Aircraft: A Potential Application for HTS Superconductors

    Page(s): 1055 - 1068
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3411 KB) |  | HTML iconHTML  

    Sustainability in the aviation industry calls for aircraft that are significantly quieter and more fuel efficient than today's fleet. Achieving this will require revolutionary new concepts, in particular, electric propulsion. Superconducting machines offer the only viable path to achieve the power densities needed in airborne applications. This paper outlines the main issues involved in using superconductors for aeropropulsion. We review our investigation of the feasibility of superconducting electric propulsion, which integrate for the first time, the multiple disciplines and areas of expertise needed to design electric aircraft. It is shown that superconductivity is clearly the enabling technology for the more efficient turbo-electric aircraft of the future. View full abstract»

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  • 47. Practical Application Issues of Superconducting Fault Current Limiters for Electric Power Systems

    Page(s): 620 - 623
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (194 KB) |  | HTML iconHTML  

    The discovery of high-temperature superconductors were the great opportunity for developing fault current limiters using quenching phenomena. Superconducting fault current limiters is highly effective solutions to reduce and control excessive fault current which is inevitable to electric power systems. So, many companies and national research institutes were trying to develop this novel electric equipment under the assistance of national government. Due to their efforts, various types of superconducting fault current limiters were designed and tested. But, unfortunately, the practical applications and commercialization of superconducting fault current limiters are pending due to many unsolved problems. This paper discusses the current issues and commercialization problems of superconducting fault current limiters considering various aspects such as coordination with conventional relay, high voltage and high current issues, performance, cost, size, and life and maintenance issues. Then, emerging solutions for fault current limiters using hybrid method were introduced and analyzed. Finally, the viable method and our newly developed hybrid superconducting fault current limiters in order to solve the practical problems of conventional superconducting fault current limiters was briefly introduced. View full abstract»

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  • 48. Design and Analysis of a Fuzzy Logic Controlled SMES System

    Article#: 5701205
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1306 KB) |  | HTML iconHTML  

    Superconducting magnetic energy storage (SMES) becomes enabling technology and emerging to power systems. Its dynamic and steady-state characteristics in various power systems are largely related to the control strategies employed. This work investigates the feasibility to implant a fuzzy logic control method to a bridge-type chopper controlled SMES system, and theoretically validates the control method for SMES application. View full abstract»

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  • 49. Current-Fed Quasi-Z-Source Inverter-Based Adjustable Speed Drive System With Bidirectional Power Flow

    Article#: 0600306
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (771 KB) |  | HTML iconHTML  

    Current-fed quasi-Z-source inverters (qZSIs) have many advantages over traditional current source inverters and current-fed Z-source inverters. This paper presents and analyzes novel adjustable speed drive systems based on the current-fed qZSI that could provide bidirectional power flow, including their topologies, operating principle, and voltage gain. The simulation results are given to verify the rationality and feasibility of the proposed topologies. View full abstract»

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  • 50. Optimal Placement of Superconducting Fault Current Limiters (SFCLs) for Protection of an Electric Power System with Distributed Generations (DGs)

    Article#: 5600304
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (207 KB) |  | HTML iconHTML  

    Power flow patterns and fault current levels are influenced by the introduction of distributed generations (DGs) in an electric power system. In particular, the change in the fault current levels caused by DG installation may require a change in the coordination of relays to prevent their misoperation. When DGs are installed in an electric power system, superconducting fault current limiters (SFCLs) can be used to help reduce the fault currents within the breaking capacity of the protective devices. In this paper, multiple criteria such as the number of SFCLs, fault current reduction, and the total operating time of the relays are considered in order to determine the optimal placement of SFCLs for protection of an electric power system with DGs, and a scenario optimization based approach is used to solve the multi-criteria SFCL placement problem. Numerical simulations are also carried out to demonstrate the effectiveness of the proposed approach. View full abstract»

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Aims & Scope

IEEE Transactions on Applied Superconductivity contains articles on the applications of superconductivity and other relevant technology.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Britton L. T. Plourde
Syracuse University
bplourde@syr.edu
http://www.phy.syr.edu/~bplourde