For three-phase voltage-based PWM converters, finite set control model predictive current control (FCS-MPC) is a kind of novel and high-performance control strategy. However, there exist the disadvantages of large amount of calculations and unfixed switching frequency for NPC three-level converters. Thus, in order to overcome the disadvantages, a simplified fixed switching frequency PWM strategy based on MPC is proposed in this paper. The algorithm does not need to perform rolling calculations on 27 three-level vectors, and directly obtains the optimal target voltage vector by calculating the cost function containing the current deviation and the midpoint potential deviation, which greatly reduces the amount of calculation. Experimental results show that the proposed simplified modulation strategy can achieve fixed-frequency control and mid-point potential adjustment of the NPC three-level converters, and has good dynamic and static performance.