Model Predictive Torque Control with Flying Capacitor Voltage Balancing of 4L-NNPC Inverter Based PMSM Drive

This paper presents a model predictive torque control (MPTC) for a four-level nested neutral point clamped (4L-NNPC) inverter-based permanent magnet synchronous (PMSM) drive. The proposed model predictive control (MPC) method effectively controls the torque of the motor as well as balances the flying capacitor voltages. The discrete model of the 4L-NNPC inverter and IPMSM motor are used to predict the torque and flying capacitor (FC) voltage for the next interval under possible switching states. These two prediction variables are assessed through a cost function to select the optimal switching state that minimizes the cost function, and optimal switching states are applied to the inverter. The performance of the proposed method is verified with the help of MATLAB and Simulink. The results indicate that the proposed MPTC strategy achieves low current THD (below 5.73%), minimum torque ripple (Tr) below 1.52 Nm, and effectively balances the average flying capacitor voltage (Vcr _avg) throughout the entire operating speed range.