Small-Signal Modeling and Control of three-phase Hybrid Transformer Considering Practical Impedances

This paper presents the small-signal models of a three-phase transformer. The derived small-signal models reflect the circuit’s practical impedances caused by the distribution and the low frequency magnetic transformers which are parts of the hybrid transformer. To simplify the model derivations, the impedances are incorporated in the LC filters which are attached to the input and the output of the back-to-back power converter. The state equations of the hybrid transformer are established, and the small-signal models are derived. Furthermore, the simplified models are suggested and compared with the originally derived small-signal models. Using the derived simplified models, the secondary constant voltage controller of the power stage is designed. The simulation and experimental results verify the effectiveness of the derived small-signal models and the controller design method.