| Research Abstract |
Energy storage devices with high energy density as well as high power density are expected to be developed from the point of view of compensation of fluctuating load and generated power by unstable distributed generations such as wind turbines, photovoltaic cells and so on. SMES (Superconducting Magnetic Energy Storage) has higher power density than other energy storage methods, and secondary batteries have higher energy density than SMES. The hybrid energy storage device using SMES and secondary batteries is proposed as the energy storage method with higher power and energy density, the sharing method of power reference value for each storage device has been studied, and experiments as will as simulations have been carried out. Obtained results are summarized as follows.
1) For the design and evaluation of the system, equivalent circuit models for a secondary battery and power converter have been developed.
2) For sharing power between a superconducting coil and a secondary battery, the method using high pass and low pass filters has been studied. As a result, the first-order high pass and low pass filters are preferred due to smaller phase lag. Higher-order filters showed worse results due to phase lag of the filters.
3) Using the method using fuzzy control with filter mentioned above, saturation and exhaustion of energy of superconducting coil have been avoided and power control of the secondary battery can be carried out
4) Simulations of compensation of fluctuation from high speed railway substation and photo voltaic generation have been carried out by using developed control method and data from measurements. As a result, the effect of hybrid energy storage system has been verified for both cases. But the better result was obtained for the high speed railway substation, because of the higher fluctuating power at the frequency range compensated by SMES.
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