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

Compensation Characteristics and Dynamics of the Active Filter for Superconducting Magnet Energy Storage

Stability of a force-cooled hollow superconductor coil for the AC loss was studied from a point of view of a cooling characteristic of supercritical helium (SHE). The coil was operated in the fluctuating magnetic field (maximum B=3.75 T/s) generated by a bias pulsed superconducting magnet. In this experimental system, the maximum AC loss in the hollow conductor coil during operation reached 1.82 W/m and the normal transition was observed due to the accumulation of the AC loss induced by the repeated operation of the bias pulsed magnet. The results from our analysis are as follows. (1) The required energy for the normal transition was almost decided by the heat capacity of SHE from the initial temperature to the critical temperature of the coil. (2) The operating mode of a force-cooled pulsed magnet is predominantly decided by the transit time and the heat capacity of SHE.

AC Loss and Stability of a Force-Cooled Superconducting Coil with a Bias Pulsed Superconducting Magnet

Design of Power System Stabilizing Control Using Superconducting Magnet Energy Storage by Means of Singular Perturbation Method

The SM (superconducting magnet) current feedback control of I-C unit (inductor-converter unit) has to be designed to maintain stability, considering that the time constant of transfer function from SM current to SM terminal voltage is very large. For accurate control, it is also very important to take into account the current and magnetic field distributions inside the SM, ac loss and stray capacitances between coils. In this paper, direct digital control systems such as PID system, first-order time lag system with dead time element, finite time setting control system (FTSC) and model reference adaptive control system (MRAS) are proposed. Control characteristics of these control systems are analyzed by experiment and simulation.

Yoshishige Murakami

Papers

Compensation Characteristics and Dynamics of the Active Filter for Superconducting Magnet Energy Storage

AC Loss and Stability of a Force-Cooled Superconducting Coil with a Bias Pulsed Superconducting Magnet

Design of Power System Stabilizing Control Using Superconducting Magnet Energy Storage by Means of Singular Perturbation Method

Direct digital control of superconducting magnet

Experiment of power system stabilization by using superconducting magnetic energy storage in artificial power transmission systems