可测量磁场的超导纳米导线

美国Illinois大学UrbanaChampaign校区的研究人员使用DNA分子支架研制出的超导纳米器件证实了一种新的量子干扰.这种器件可用来测量磁场和测定超导区域.一位研究人员说：“利用DNA的自我装配过程可为带有分子线度的电子器件制造出复杂的支架.”     

Optimal control of the magnetic bearings for a flywheel energy storage system

With the advances of high strength/light weight composite material, high performance magnetic bearings, and power electronics technology, flywheel energy storage systems (FESS) with magnetically assisted bearings are becoming an exciting alternative to traditional battery systems. One of the challenging problems for such systems is to stabilize the sensitive rotor due to disturbances and plant uncertainties. In this paper, an optimal control system is proposed by incorporating cross-coupling technology into the control architecture, so that the synchronization performance of the rotor in the radial direction can be improved. The control scheme is based on minimization of a new quadratic performance index in which the synchronization errors in the radial direction are embedded. Stability of the control scheme is investigated through Linear Quadratic Gaussian (LQG) optimal control technique. It has been shown that with adequate control parameters the closed-loop stability can be guaranteed theoretically, and the resulting control system can provide satisfactory synchronization performance. Simulations on a compact and efficient FESS with integrated magnetic bearings demonstrate that the proposed approach is very effective to suppress the gyroscopic effort caused by the outside disturbances and model uncertainties.     

30-MJ superconducting magnetic energy storage system for electric utility transmission stabilization

A superconducting magnetic energy storage (SMES) system has been built to damp power oscillations on the Western U.S. Power System, particularly on the Pacific AC Intertie that is used to transmit power from the Northwest to southern California. The 30-MJ superconducting inductor that stores energy for this purpose is contained in a nonconducting dewar and is supported by a helium refrigerator and a gas-handling system mounted on trailers. Energy flows in and out of the inductor at frequencies from 0.1 to 1.0 Hz with power amplitudes up to 11 MW. The principal oscillation to be damped has a characteristic frequency of 0.35 Hz. The superconducting coil maximum current is 5 kA with terminal voltages up to 2.2 kV. The coil interfaces with the Bonneville Power Administration 13.8-kV bus at the Tacoma Substation through a converter and transformers. The system can be operated with the converter either in parallel-bridge mode or for constant VAR control with the bridges in buck-boost mode. The program for the design, fabrication, installation, and the preliminary experimental operation of the system is reviewed.     

Superconducting receiver coils for sodium magnetic resonanceimaging

Presents the results from sodium magnetic resonance imaging (MRI) experiments using high-temperature superconducting (HTS) receiver coils. Sodium imaging has been shown to have great potential for the assessment of cell integrity but suffers from substantially lower signal-to-noise ratio (SNR) than that of hydrogen imaging. The use of an HTS receiver coil was found to significantly increase the SNR relative to an equivalent copper receiver coil at room temperature. The SNR gains afforded by HTS coils can also be used to decrease the imaging time     

Superconducting cylinder in a static transverse magnetic field

A piecewise continuous distribution of the critical currents is proposed to make compatible the Maxwell equations and constitutive equations of superconducting media. A magnetic moment of the infinite superconducting cylinder is calculated on the base of the proposed shell model. Some generalizations of the calculation method are given for superconductors of more complicated shapes     

Improved controller for power conditioner using high-temperature superconducting magnetic energy storage (HTS-SMES)

One of the most important functions in a superconducting magnetic energy storage (SMES) system when used for power conditioning, is the ability to charge the super-conducting coil as fast as possible to ensure that it is ready when it is next required. This paper describes a novel controller for a high-temperature SMES (HTS-SMES) that can ensure: 1) fast return of energy to the superconducting coil under constant-current mode and 2) a constant and sinusoidal input supply current irrespective of the varying load demand with and without harmonics. In the new HTS-SMES proposed, two hysteresis controllers are used, one to control the magnitude, phase and the waveform of the ac supply current, and the other is to control a dc chopper to regulate the SMES coil current. The first hysteresis controller ensures that as far as the power utility is concerned, the load appears to the utility system as a constant sinusoidal load with unity power factor irrespective whether the load is distorted or varying in nature. The second hysteresis controller has been designed to regulate the energy in and out of the superconducting coil. A special feature of this controller is its ability to smoothly charge the superconducting coil using constant current charging so that it can be ready for the next discharging operation as soon as possible. Analysis of the circuit operation under hysteresis control is presented in details. Simulation and experimental results are presented demonstrating the feasibility of the proposed power conditioning system.     

Battery energy storage technologies

Battery energy storage systems, comprising lead-acid batteries, power conversion systems, and control systems, are discussed. They are used by power generating utilities power distributing utilities, and major power consumers (such as electric furnace foundries). The principal advantages that battery energy storage systems offer generating utilities are described, including load leveling, frequency control, spinning reserve, modular construction, convenient siting, absence of emissions, and investment deferral for new generation and transmission equipment. Power distributing utilities and major power consumers can avoid costly demand changes by discharging their batteries at peak periods and then recharging with lower cost off-peak power (say, at night). Battery energy storage systems are most cost-effective when designed for discharge periods of less than 5 h; other systems (for example, pumped water storage) are better suited for longer discharges. It is estimated that by the year 2000 there will be a potential need for 4000 MW of battery energy storage     

新技术使电容储能增加一倍新型封装技术开创了使用高介电常数的钛酸钡来制造陶瓷/多聚物电容器

根据美国亚特兰大州佐治亚理工学院有机光电中心(Center for Organic Photonics and Electronics)的研究人员介绍,一种创新的封装技术将使用具有高介电常数特性的钛酸钡(BaTiO3)纳米级微粒子来制造电容器,该技术能使电容器储存的能量提高一倍.     

Residential photovoltaic energy storage system

This paper introduces a residential photovoltaic (PV) energy storage system, in which the PV power is controlled by a DC-DC power converter and transferred to a small battery energy storage system (BESS). For managing the power, a pattern of daily operation considering the load characteristic of the homeowner, the generation characteristic of the PV power, and the power-leveling demand of the electric utility is prescribed. The system looks up the pattern to select the operation mode, so that powers from the PV array, the batteries and the utility are utilized in a cost-effective manner. As for the control of the system, a novel control technique for the maximum power-point tracking (MPPT) of the PV array is proposed, in which the state-averaged model of the DC-DC power converter, including the dynamic model of the PV array, is derived. Accordingly, a high-performance discrete MPPT controller that tracks the maximum power point with zero-slope regulation and current-mode control is presented. With proposed arrangements on the control of the BESS and the current-to-power scaling factor setting, the DC-DC power converter is capable of combining with the BESS for performing the functions of power conditioning and active power filtering. An experimental 600 W system is implemented, and some simulation and experimental results are provided to demonstrate the effectiveness of the proposed system     

Instantaneous control method with a GTO converter for active andreactive powers in superconducting magnetic energy storage

A new type of GPG (gate pulse generator) is presented to give GTO power converters quick response firing angle control and PWM control functions. Using the GPG, an instantaneous control method of active and reactive powers for an SMES (superconducting magnetic energy storage) employing one GTO converter is studied     

Superconducting tunneling-junction detectors of X-ray radiation. Issues concerning the energy resolution

The effect of the recombination-and edge-related losses of nonequilibrium quasiparticles on the energy resolution of superconducting tunneling detectors is studied. The dependence of the signal on the energy of X-ray photons is measured and the shape of instrument-related lines is studied for the Ti/Nb/Al/AlO_x/Al/Nb/NbN detectors with the Ti/Nb passive electrode. Experimental data are analyzed using the diffusion-based model of tunneling detectors.     

Wind energy conversion system associated to a flywheel energy storage system

This paper deals with the study of a variable speed wind induction generator associated to a flywheel energy storage system. Direct torque control strategy is applied to control the induction generator where both rotor flux and DC bus voltage are controlled through the application of the standard switching table for operations in the 4 quadrants. The flywheel energy storage system is used to improve the quality of the electric power delivered by the wind generator. The proposed system, controlled thanks to Direct Torque Control (DTC) strategy, is validated through simulations. The obtained results are presented and discussed.     

Spinning reserve [energy storage system]

Combining a flywheel, a motor and a generator results in a novel energy storage system with some remarkable attributes. In this paper, the author describes how the application of modern materials and power electronics has given new life to one of humankind's oldest inventions     

Active power filter with hybrid energy storage

An active power filter that uses an impressed current converter and an inductive-capacitive energy storage circuit is presented. This storage includes a switching section to interface the inductive and capacitive element. This solution allows independent choice of the converter configuration and of the type of storage system which, in this particular case, is mainly capacitive. The theory of operation is analyzed, together with control strategy and design criteria. Experimental results are reported     

Flexible energy storage devices for wearable bioelectronics

With the growing market of wearable devices for smart sensing and personalized healthcare applications,energy stor-age devices that ensure stable power supply and can be constructed in flexible platforms have attracted tremendous research in-terests.A variety of active materials and fabrication strategies of flexible energy storage devices have been intensively studied in recent years,especially for integrated self-powered systems and biosensing.A series of materials and applications for flex-ible energy storage devices have been studied in recent years.In this review,the commonly adopted fabrication methods of flex-ible energy storage devices are introduced.Besides,recent advances in integrating these energy devices into flexible self-powered systems are presented.Furthermore,the applications of flexible energy storage devices for biosensing are summar-ized.Finally,the prospects and challenges of the self-powered sensing system for wearable electronics are discussed.     

Gain and energy storage in holmium YLF

It is demonstrated that Q-switched holmium lasers are capable of high-gain and high-energy operation at 300 K. Small-signal gain coefficients of 0.50 and 0.12 cm/sup -1/ have been measured in YLF and YAG, respectively. Small-signal gains of 0.50 cm/sup -1/ are comparable to those achievable in Nd-YAG and are not typical of low-gain materials. This large gain in the Ho:YLF material is made possible by operating the amplifier in the ground state depletion mode. The amplifier performance data and associated analysis presented demonstrate that efficient energy storage is possible with very high excited state ion densities of the Ho /sup 5/I/sub 7/ upper laser level. This is an important result since upconversion can limit the /sup 5/I/sub 7/ population. Although upconversion was still present in this experiment, it was possible to achieve efficient energy storage, demonstrating that the problem is manageable even at high excitation densities in YLF.<>     

Economic optimization of energy conversion with storage

An experimental system being developed at Oklahoma State University represents the first phase of a research effort to formulate a model for optimizing an energy conversion and storage system. Some of the problems in providing energy storage as an alternative to added conversion capacity to meet peak demand are treated here. It is assumed that the conversion system is a steam or hydro plant with a controlled input as opposed to a solar or wind plant with a random input, although extension to the latter is possible.     

超导计算机及超导武器装备

超导技术的发展前景广阔,在国外军事领域受到极大重视。超导计算机具有很高的运算速度和巨大的运算能力,是21世纪超级计算机的发展方向。超导技术将使武器装备发生重大变革。军事C3I系统由于有了超导计算机,能快速、有效地把各种武器系统、各军兵种和各战场连结成一个有机整体。概略介绍超导磁性水雷、超导发动机和超导飞机、超导装甲车和超导导弹、超导电磁推进系统和超导舰艇、超导太空发射器等武器装备的发展前景。     

Progress in magnetic fusion energy research

The remarkable scientific progress that has been made in the Magnetic Fusion Energy Program since its inception 40 years ago is reviewed. This formalized international collaborative effort of design and development for a 1000-MW experimental reactor (ITER) has been entered into by the United States, Russia, Japan, and the European Community. In the United States, a national project to build a superconducting steady-state advanced tokamak (SSAT) to improve the reactor prospects of fusion is underway. Beginning with a quick summary of fundamentals, progress in research is traced through major steps in the program. This study concludes with a view of the future and of the problems remaining to be overcome before a demonstration (demo) power plant can be built by the 2025 date given in the US National Energy Strategy     

Energy storage in photovoltaic stand-alone energy supply systems

Energy storage is a key element in solar energy supply. Thirty per cent of the lifetime costs of solar off-grid systems or even more may be attributed to the storage. Although a variety of storage technologies is under development, the lead–acid battery still is, and will be for some years to come, the working horse for electricity supplies in remote areas. This paper discusses the operating conditions of batteries in photovoltaic systems. The ageing effects that limit battery lifetimes are treated in detail. Electronic equipment, which is used to support the operation of batteries, is presented. Optimized control strategies will in future allow a considerable reduction of the overall system costs mainly through an extension of battery service lifetimes. © 1998 John Wiley & Sons, Ltd.