Feed-forward control of solid state transformer

Abstract

The solid state transformer (SST) can be viewed as an energy router for electricity in an analogous way to what network routers are for information. The SST impact on the system can be hence paramount, especially in terms of stability since it is essentially an active closed-loop regulated power converter. Within the SST itself however, with its different ac-dc, dc-dc and dc-ac stages, stability is also crucial, as it is well understood that for cascaded converter systems the interaction between stages is the cause of instability from a small-signal perspective. This paper represents an initial quest into the SST stability study, exploring two feed-forward control schemes for the ac-dc and dc-dc converter stages. Simulation and experimental results with a 7.2 kV ac 400 V dc, 20 kW laboratory prototype are presented for validation purposes.