Implementation of Flexible Large Power Transformers Using Modular Solid State Transformer Topologies Enabled by SiC Devices

Large power transformers (LPTs) have been a major concern of the electric power sector as a failure of a single unit can lead to temporary service interruption and utility damages. Replacement of such large and heavy transformer units is a challenging job as LPTs are custom-designed and hence entail long lead times due to its intricate manufacturing process and transportation. On the other hand, solid-state-transformer (SST) technology has evolved as an alternate option for the conventional line-frequency transformers, which offers comparatively reduced size and weight with the enhanced power quality features. With the advancement in wide-bandgap devices such as silicon carbide (SiC) and advanced power electronic converters, SSTs are able to deploy in medium voltage applications. Consequently, the utilization of SiC-SSTs for large power applications can mitigate some of the existing concerns of LPTs. In this paper, challenges and concerns associated with the existing LPTs are discussed. Possible SST modules/cells enabled by SiC devices, which can be connected in a modular structure to achieve multi-cell flexible large power SSTs (FLP-SST) are presented. The effectiveness of the discussed SST cells is validated using appropriate simulations and experimental results of the scaled SST prototypes.