Multi-winding phase-shifting transformer for 36-pulse rectifier: Winding turns design and analysis

Multilevel power conversion has been receiving increasing attention in the past few years for high power applications. Extensive use of these switching devices based power converters lead to injection of large amount of harmonics in the grid. This paper proposes design and simulation of six winding transformer for 36-pulse rectifier unit and selection of suitable phase-shifting of these windings to reduce total harmonic distortion (THD). The concept of extended delta winding has also been proposed in this paper which will be used for design of multi-winding transformer to suppress harmonics from input grid current. In addition, the consequences of selection of improper turns ratio of windings due to constructional limitations is also discussed in this paper.