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Cylindrical geometry was used for examining the dynamic levitation force curves between a superconductor disk and a permanent magnet. Findings revealed slight discrepancy in the region with more significant hysteretic effect.

The article studies the design and testing of a flywheel energy storage system (FESS) prototype connected to the grid as real power shunt compensator. Results suggest that the prototype is capable of correctly varying the speed of the flywheel for supply/absorb of power to/from the grid.

Summary: The fault current level in distribution systems has increased in the last years mainly due to the energy consumption is in the limit of the production capacity and also the insertion of distributed generation, since the short circuits happen very closer to the generators now. In addition to this, most of the power substations were designed decades ago, so their equipment is overcome, and they may be damaged in a fault occurrence. To effectively protect the settled equipment or to avoid high investment costs in replacing them, one possible solution is to install a solid‐state fault current limiter (SSFCL), which may reduce the fault current to a value under the supported level. In this context, this work proposes the development of two kinds of SSFCLs: series‐switched reactor and resonant circuit. These devices were designed and compared experimentally in bench prototypes. The measurements showed that both topologies could reduce the fault current from 600 APEAK to 75 APEAK. Both SSFCL‐tested configurations were implemented using silicon controlled rectifier or insulated gate bipolar transistor. The results present the comparison between them, showing the impact in the first semi‐cycle current profile, depending on the type of semiconductor switch adopted. This article also proposes a fault detection algorithm evaluated through digital implementation in a microcontroller. The algorithm detects the fault by the instantaneous current value and its derivative, using a control strategy that avoids false detection due to measurement noises. The theoretical analysis and results are useful contributions to support the SSFCL topology choice regarding its application. [ABSTRACT FROM AUTHOR]

In order to develop a new magnetic bearing set for a flywheel energy storage prototype, it was designed and simulated some configurations of Permanent Magnetic Bearings (PMB) and Superconducting Magnetic Bearings (SMB). The bearings were assembled with Nd-Fe-B permanent magnets and the simulations were carried out with the Finite Element Method (FEM). The PMB was designed to reduce the load on SMB and provide radial positioning of the whole set. SMB were designed with YBCO superconductors and an assembly of permanent magnets. Several configurations of permanent magnets were simulated, trying to maximize the magnetic flux gradient in direction orthogonal to the movement and flux density in the surface of the superconductors. Early experiments have shown an increasing stiffness and levitation force with increasing field gradient and intensity. It was also a goal to reduce the stray field outside the bearing. The levitation force of the SMB using a flux shapers configuration was measured and compared with FEM simulation, showing very good agreement. The simulation of a SMB using Halbach array configuration shows that it increases the levitation force and reduces the stray field. [ABSTRACT FROM AUTHOR]

This paper presents a voltage sag compensator, which uses a flywheel energy storage system with superconducting magnetic axial thrust bearing (SMB) and a permanent magnet radial bearing (PMB). The SMB was built with Nd-Fe-B magnet and YBCO superconducting blocks, refrigerated with liquid Nitrogen. The magnets are assembled with magnetic flux shapers in order to increase the levitation force and the stiffness. The radial PMB is used to positioning the vertically arranged switched reluctance machine (SRM) used as motor/generator. Simulations of the power electronics and SRM show that the system can work up to 30,000 rpm supplying the required energy during disturbances. [ABSTRACT FROM AUTHOR]