With the advancement of semiconductor technology, solid state transformer (SST) with high voltage fast switching SiC power devices is becoming a valid option to replace the conventional transformers in power substation. In this paper, a 270 kVA solid state transformer based on 10 kV SiC power MOSFET has been proposed. The two stages of SST, five-level Vienna rectifier and five-level DC/DC converter are specifically designed and simulated in closed loop. The analysis of device losses is performed based on the device characteristics. A design of high frequency transformer is presented as well. The simulation results together with the loss analysis verify the functionality and feasibility of SST.