The Stability Analysis and Enhancement Method of the Cascaded Solid State Transformer

Solid state transformers (SST) are widely used in the fields of renewable energy generation, large capacity energy storage, and transportation electrification. However, with the increase of voltage and power levels of the solid-state transformer, cascaded solid state transformers are facing severe stability risks. This paper first constructs an input impedance model of a cascaded solid-state transformer, and then reveals the mechanism of its interaction instability with medium-voltage grid. Based on the relevant analysis, this paper proposes corresponding stabilization methods to help stabilizing the SST. The accuracy of the relevant analysis and the effectiveness of the proposed stabilization method have been verified on a hardware in the loop (HIL) experimental platform.