Solid State Transformers for Smart Grid Control and Applications- A Review

With the increase in integration of non-conventional energy sources like solar and wind, and fairly large loads like electric vehicle charging stations, the performance of the distribution grid has considerably been affected. This calls for an efficient as well as flexible means for integrating them into the grid. Solid State Transformers (SST) are a good option for reducing various power quality issues like voltage and frequency fluctuations, for reactive power compensation and to improve system stability. This paper reviews the basic structure of SST and its different configurations based on the number of converters employed. It compares the performance of the smart transformer with a conventional transformer. Different topologies of the isolated type DC-DC converter of ST are also explained. An analysis of the stability of smart transformer grid is done, considering different voltage control strategies. The use of SST for interfacing wind energy into the grid and also the performance of converter when controlled with PI, PID and Fuzzy logic controllers are analyzed and compared.