Design and fault-operation analysis of a modular cyclic cascade inter-cell transformer (ICT) for parallel multicell converters

Nowadays, parallel multicell converters including inter cell transformers (ICTs) are usually used in many different conversion systems and with various topologies. In this paper, an analysis of a modular cyclic cascade ICT is presented for nominal and fault operation. The first part of the article presents a pre-design methodology for cyclic cascade ICTs in nominal operation. Afterwards, an analysis of magnetic behaviour during failure operation as imbalance current or case of k disconnected phases will be presented. The aim of this article is to design a cyclic-cascade ICT that is more robust in failure operation. Air gaps (AGs) have been inserted in order to limit this saturation. A concept of compact cyclic-cascade ICT with just a single winding by phase is presented. We will show its principle of realization and 2D fine element simulation in order to validate this concept.