When converter in Solid State Transformer (SST) operates in rectifier mode, the AC-side current predictive control is applied to achieve unity power factor operation and smooth DC voltage. Output voltage prediction is adopted to converter operating in inverter mode, improving the ability against load disturbances. In this paper, two nonzero vectors and two zero vectors are adopted in fixed switching frequency model predictive control. According to the relationship between duty cycle and cost function, the optimal duty cycles of each vector are applied and rational switching patterns are chosen. This strategy needs no pulse width modulation controller, which can avoid instability caused by complex parameters settings of proportional integral controller and reduce high sampling frequency of single nonzero vector model predictive control. The simulation results show that the voltage and current of each level have good dynamic response and the SST is robust against load disturbances in different typical operation conditions, meeting the performance requirements of microgrid for SST. This work is supported by National Science and Technology Support Project of China (No. 2015BAG19B02) and Shanghai Committee of Science and Technology (No. 13DZ1200403).