Three-Level Model Predictive Torque Control of Permanent Magnet Synchronous Machine with Switching Frequency Optimization

In order to reduce the switching frequency involved in the traditional three-level model predictive control utilized for permanent magnet synchronous motors(PMSMs), a model predictive torque control scheme associated with the switching frequency optimization is proposed. Firstly, the reason for higher switching frequency in the three-level drive system is analyzed in depth. Then, the vector screening strategy considering switching state restriction is introduced and the switching frequency constraint is constructed in the cost function, which can effectively reduce the switching frequency as well as decrease the number of candidate vectors. Furthermore, the neutral potential is balanced in terms of the opposite effect of positive and negative redundant small vectors on neutral potential. Finally, the validity of the control strategy is verified by the simulation and experiment. The simulated and experimental results prove that the switching frequency of the proposed control strategy is reduced by nearly half of that in traditional strategy;meanwhile, the fluctuation of neutral potential is eliminated.