While energy storage technologies do not represent energy sources, they provide valuable added benefits to improve stability power quality, and reliability of supply. Battery technologies have improved significantly in order to meet the challenges of practical electric vehicles and utility applications. Flywheel technologies are now used in advanced nonpolluting uninterruptible power supplies. Advanced capacitors are being considered as energy storage for power quality applications. Superconducting energy storage systems are still in their prototype stages but receiving attention for utility applications. The latest technology developments, some performance analysis, and cost considerations are addressed. This paper concentrates on the performance benefits of adding energy storage to power electronic compensators for utility applications.

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Energy storage systems for advanced power applications

Exploring dynamics in the far-infrared with terahertz spectroscopy.

Superconducting magnetic energy storage (SMES) is known to be a very good energy storage device. This article provides an overview and potential applications of the SMES technology in electrical power and energy systems. SMES is categorized into three main groups depending on its power conditioning system, namely, the thyristor-based SMES, voltage-source- converter-based SMES, and current-source-converter-based SMES. An extensive bibliography is presented on the applications of these three types of SMES. Also, a comparison is made among these three types of SMES. This study provides a basic guideline to investigate further technological development and new applications of SMES, and thus benefits the readers, researchers, engineers, and academicians who deal with the research works in the area of SMES.

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An Overview of SMES Applications in Power and Energy Systems

Utilization of renewable energy are coming up from view points of environmental conservation and depletion of fossil fuel. However, the generated power from renewable energies is always fluctuating due to environmental status. Energy storage system is indispensable to compensate these fluctuating components. Energy capacitor system (ECaSS) connected an electric double-layer capacitor (EDLC) with power-electronics devices is useful for the compensation of fluctuating power since one is capable of controlling both active and reactive power simultaneously. This paper proposes the current-source ECaSS (CS-ECS), which consists of EDLC, bi-directional DC-DC converter, and current-source inverter. We have presented the control system for the active/reactive power control of CS-ECS, and have shown the effectiveness of CS-ECS through computer simulations for case of wind power generation system.

Output levelling of renewable energy by electric double-layer capacitor applied for energy storage system

The THz-radiation power from bulk InAs irradiated with femtosecond optical pulses is significantly enhanced and reaches 650 μW in a 1.7-T magnetic field with 1.5-W excitation power. The THz-radiation power is related almost quadratically both to the magnetic field and excitation laser power. We have also found that the power of the THz-radiation from an InAs sample in a magnetic field is over one order of magnitude higher than that from GaAs. Additionally, a dramatic change of ellipticity is observed, and the spectra of the horizontal and vertical polarization components are found to differ.

High average-power THz radiation from femtosecond laser-irradiated InAs in a magnetic field and its elliptical polarization characteristics

Stabilization of series compensated system by superconducting magnet energy storage system

A High Speed Phase Shifter (HSPS) using PWM inverters is paid much attention in FACTS (Flexible ac Transmission System). The HSPS presented here is composed of three sets of a single phase PWM inverter, transformers and ac filters for suppressing switching ripples of inverters. The proposed system has an energy storage component, therefore the system can control voltage phase freely. Design of the HSPS and experimental results of power system stabilizing control on a 10kVA model power transmission are presented.

Power systemstabilizing control by a high speed phase shifter with an energy storage component

Low-frequency Raman spectra have been measured to clarify the relationship between low frequency modes and the incommensurate modulation in Pb doped Bi2Sr2CaCu2O8. The lines corresponding to the folded acoustic modes arising from the incommensu­rate modulation change in frequency rather abruptly at around nominal Pb composi­tion of 13%. This result is interpreted in terms of the change in the period of the modulation with the Pb doping.

Low-Frequency Raman Spectra of (BiPb)2Sr2CaCu2O8

We have succeeded in obtaining a Bi-system superconducting thick film on a MgO(100) substrate. It consists mainly of the high-Tc phase and exhibits Tc(zero) at 102 K by the melt guenching method with an intermediate process. The process uses precursor powders which already contained high-Tc superconducting phase.

Preparation of Bi-System Superconducting Thick Films by Melt Quenching Method

The bridge-type thyristor power converter is being used most extensively as the interface equipment between three-phase power supply and superconducting magnet (SM). The I-C unit (inductor converter unit) combined with SM is able to charge the stored magnetic energy to or discharge it from SM. For optimal control of I-C unit, it is necessary to learn the dynamic response characteristics of SM. However, it is difficult to learn it directly from the structure of conductor and coil. To overcome the difficulty, the dynamic response characteristics from the input/output relationship of I-C unit is estimated and the constants of the equivalent circuit of SM determined. The input/output relationships of I-C unit and SM as a linear discrete time system are identified. The random signal is suited for estimation of dynamics to small input signals and for on-line estimation. When the step input is applied, the amplitude of input signal and the setting value of SM current have to be adjusted at every test run. The present experiments use the random signal and identify the constants of the control system so as to minimize the mean square of the difference between the estimated and the observed output signals. The transfer function thusmore » identified is used to study the dynamic of I-C unit. It is also shown that a small magnet storing energy of 100 kJ can be represented by a series-connected R-L equivalent circuit. A multiple shunt equivalent circit for the case of high ac loss caused by quick excitation is proposed.« less

Yoshishige Murakami

Papers

Stabilization of series compensated system by superconducting magnet energy storage system

Power systemstabilizing control by a high speed phase shifter with an energy storage component

Low-Frequency Raman Spectra of (BiPb)2Sr2CaCu2O8

Preparation of Bi-System Superconducting Thick Films by Melt Quenching Method

Identification of dynamics of superconducting magnet and its control system