Virtual Transformer Operation of Solid State Transformer (SST)

Abstract

This paper proposes a virtual transformer operation of a three-stage solid state transformer (SST) used in the distribution network. By tracking the AC voltage at medium voltage AC (MVAC) input side as the reference of low voltage AC (LVAC) output stage, voltage relationship between AC buses can be established, and the mutual voltage support can be formed through the SST. The employed control method can make the SST operate as an ideal AC transformer which has a constant transformation ratio. Circuit parameters design and control parameters calculation are given in this work. Simulation results based on this SST topology and control method prove that this virtual transformer operation based on a three-stage SST is feasible through the software Matlab/Simulink.