Scalability Assessment of the Parallel Operation of Direct Current Transformer

Paralleling duty-cycle controlled high-power converters is well understood while achieving the same with un-controlled resonant converters poses certain challenges. In order to predict the current sharing unbalance after paralleling several direct current transformers, this paper proposes a methodology to define the quality of the parallel connection considering system -level parameters. Based on the input impedance of the small signal model, critical parameters are identified, and the impact of the different levels of parameter variation on the current sharing of direct current transformers is evaluated. Then, design constraints based on the model are set to achieve satisfying current sharing considering the resultant input impedance. Further, the impact of the switching frequency, considered the only design degree of freedom, on the input impedance is used to modify the current sharing between the modules. Modeling and predictions are verified by means of simulation and experimental investigations.