Orie Sakamoto

Influence of Structural Material and Epoxy Impregnation on Coil Strains in Y123 Pancake Coil

Single-pancake coils having different winding turns are fabricated. The bobbin material used for the coils is a Dyneema fiber-reinforced plastic (DFRP), which has a thermal expansion property during cooling. The influence of the DFRPs expansion on thermal strains of the coil during cooling is experimentally estimated. In the experiment, the thermal strains on the superconducting tape of the outermost turns in the coils are measured. The dependence of epoxy impregnation on the thermal strain of the coil is also experimentally estimated. According to the experimental data, the combination of impregnation and the bobbins expansion effectively decreases thermal contraction of the outermost tape.

High Thermal Conduction Bobbin and Thermal Stability of Conduction Cooled Superconducting Pancake Coils

We have proposed a Dyneema fiber reinforced plastic (DFRP) as a coil bobbin material. The DFRP has some properties such as high thermal conduction, easy mechanical processing, and expansion with cool down. We fabricated superconducting coils having an YBCO tape, cooled the coils with a refrigerator, and supplied a dc current to the conduction cooled coils. Thermal stability of the coils was also estimated. The DFRPs, glass fiber reinforced plastics, and AlN blocks were used as the bobbin materials for the coils. From the experimental results, the thermal stability of the coils increased with increasing of the winding tension of the coils, and the coil having the DFRP bobbin showed better performance than the coils with the glass fiber reinforced plastic and the AlN bobbins. We think that contact force between the superconducting tape and the bobbin became large due to the thermal expansion of the DFRP bobbin. These results showed that DFRP can represent a viable opportunity as bobbin material for conduction cooled high-temperature superconducting coils.

Mechanical Loss and Bobbin Material in Double Pancake AC Superconducting Coils

We fabricated nonimpregnated HTS superconducting coils with a BSCCO tape. Bobbin materials in the coils are a Dyneema(R) fiber reinforced plastic (DFRP) and a glass fiber reinforced plastic (GFRP). We excited those coils with ac currents, and estimated mechanical losses. According to the measured data, the mechanical loss decreased with increase of winding tension of the coils, because strong winding tension fixed the coils tightly. Also, the mechanical loss occurred in the DFRP coil was smaller than that occurred in the GFRP coil. A thermal expansion coefficient of the DFRP is a negative value, that is, the DFRP expands with cooling down from room temperature to cryogenic temperature. The expansion of the DFRP bobbin made the winding of the coil fix tightly, and the mechanical loss decreased. From those experimental results, we think that the DFRP bobbin is useful for decreasing of mechanical losses of the ac coils.

An example of a diesel generator model with fluctuating engine torque for transient analysis using XTAP

In remote site power systems with small diesel generators, weak distribution feeders with diesel generators may suffer from voltage and power fluctuations due to misfiring of the engine cylinder. A...

Development of a New Superconducting Generator Model for Power System Transient Analysis with XTAP

Superconducting generators (SCGs) are considered to bring many advantages to electric power grids such as high generation efficiency, improvement of power quality, capability to enhance power system stability, and so on. In order to investigate these benefits in the conditions similar to those of a real power system, electromagnetic transient (EMT) analysis in three-phase instantaneous values is very useful. In this study, a new SCG model for power system transient analysis has been developed with an EMT software named Expandable Transient Analysis Program. Novelty of the newly developed model is in the calculation procedure using a two-stage diagonally implicit Runge-Kutta method and a second-order Runge-Kutta method (RK2). The proposed method enabled us to interface the SCG model with the outer power system without prediction or delay. The method is considered to enhance the numerical stability of transient analyses including SCGs by explicitly limiting the integral calculation errors through the use of RK2. It was confirmed that the developed model is useful to EMT analysis including SCGs.

Power compensation in the microgrid by SMES using the current source inverters

In this paper, the authors proposed the loop microgrid system composed of loads, Superconducting Magnetic Energy Storage (SMES), and renewable energies such as solar and wind generators. The system adjusts the balance of supply and demand in the microgrid by compensating the power fluctuation of renewable energy sources with SMES. The SMES is connected with two independent Current Source Inverters (CSIs) in order to control power flow in the microgrid as well as at the interconnection with the main power system. The aim of this paper is to control power flow at the point of interconnection with the main system and the microgrid. The system was simulated by using PSIM and MATLAB/Simulink. The authors proved that the system can control the power flow as expected.

Effects of Mechanical Vibration and Thermal Conductivity in Bi-2223 Tapes Using Ionic Liquid Impregnation

We prepared two kinds of ionic liquids (DEME BF4, DEME TFSI), and measured the thermal conductivity of the ionic liquids and the ac loss of the Bi-2223 tape using the ionic liquid impregnation under dc magnetic field in liquid nitrogen. As a result, the thermal conductivity of DEME BF4 is approximately twice that of the epoxy. When the mechanical loss is maximum value, the loss can be reduced about 98.5% by using the ionic liquid compared with no impregnation. We consider that the tape impregnated into the ionic liquid is effective for reducing the ac loss. These results produce fundamental data to reduce the ac loss of conduction-cooled high-temperature superconducting coils.

Power flow control in AC loop microgrid with a SMES connected with two independent converters

In this paper, the authors proposed a new circuit topology of AC loop microgrid with a Superconducting Magnetic Energy Storage (SMES) and solar and wind generators. The SMES is connected with two converters controlled independently to supply power to different parts of the microgrid. The balance of supply and demand in the microgrid is adjusted by controlling the converters. The aim of this study is to control power flow between the main power system and the microgrid so as to reduce reverse power flow. The authors proved that SMES can control the power flow in the proposed microgrid through the numerical simulation by use of PSIM and MATLAB/Simulink.