Improved Graph-Theory Based Modeling of the Smart Transformer for Hybrid Grids

Hybrid grids can improve the flexibility of electric distribution but they need Smart Transformers (STs) to introduce full controllability of the power flow. Describing the topology of the ST based on Graph Theory provides the possibility to use advanced control strategies, such as power routing, optimizing the power distribution inside the ST for multiple objectives. However, the Graph-Theory based flow networks used in previous works considered the flow conservation constraint (FCC), which provides fast execution times but compromises the accuracy. This work reveals significant differences among the total losses of a hybrid grids feeding ST between the modeling with and without FCC, which makes Graph-Theory based flow networks with non-conserved flow approach the preferable choice if the application specific prerequisite for the calculation time can be achieved. The influence of FCC on the losses is validated via measurements on two dual active bridges in the laboratory.