Influence of magnetic linkage between coils of a modular SMES.

To scale up the capacity of an SMES for a practical application, it is necessary to adopt a high-voltage system, a large current system or a modular system. The first system is difficult because of the very low withstanding voltage of a superconducting coil and the second also involves difficulties such as multiple connections of many convertors on the dc side and large current conductors in the superconducting coil. The third system, composed of several modules with small-scale convertor units and element coils, might be a solution of the above difficulties. In this modular system, the module coils have magnetic linkage with one another. In this paper, the influence of magnetic linkage between coils of a modular SMES is investigated by computer simulation. The magnetic linkage varies with the number of modules and the type of connection of the coils. By the effect of this magnetic linkage, each module's coil current is different at the same power. The current and energy transfer characteristics are determined for discharge from one or more of 6 modules, consisting of 18 coils. The discussion deals with the case in which there is an unused module when quenching occurs. The transfer with the same current in all modules is shown by control of convertor power of the current feedback. © 1997 Scripta Technica, Inc. Electr Eng Jpn. 118 (4): 1–9, 1997 [ABSTRACT FROM AUTHOR]