A high current bidirectional DC-DC converter for concept demonstration of grid-scale SMES systems

This paper presents the development and testing results of the high current bidirectional DC-DC converter system for concept demonstration of the next generation high current superconducting magnetic energy storage (SMES) system under a program funded by ARPA-E. The grid-scale SMES system could be enabled by new superconductor materials and manufacturing technologies and targets MWh level energy storage applications. In the SMES power conversion system, interleaving of three-level NPC DC-DC converters with voltage reversal for bidirectional power flow is proposed to meet the requirements of new SMES coil systems, such as high current and voltage ratings, low current and voltage ripples, wide operation range, and modularity. To demonstrate the concept, a 700A/12V SMES lab coil prototype and a 6-channel interleaved bidirectional DC-DC converter with three-level NPC modules have been developed and tested. The paper focuses on the detail design and implementation of the high current DC-DC converter system including the power stage, passive components and control electronics, and the testing results for the proposed converter solution for SMES applications.