In recent years the complexity of the grid systems has grown due to the increased penetration of renewable energy and distributed generation sources. The increased complexity requires new methods to quickly manage the changing sources and loads. This research focuses on one of such technologies, called the Solid State Transformer (SST). A SST uses power electronic devices and a high-frequency transformer to achieve isolation and voltage conversion from one level to another. Several SST topologies have been proposed by different research groups, without a clear consensus on which is most suited for grid applications. To ensure a proper choice of topology, a separate literature review is presented in this thesis. The final choice of topology is extremely modular and can be expanded to any voltage and power level. A first order design is made based on this topology for quantitative research. In order to reduce computation times during simulations, the SST circuit is reduced to an averaged model. After development of the averaged model, the controller for the different parts of the SST is designed. The averaged model of the SST along with its controller is then placed in several grid scenarios to investigate its behavior. These simulations show satisfactory behavior of the SST under both normal operation and disturbances.