A Neutral-Point Potential Balanced Deadbeat Direct Torque Control Strategy of Post-Fault Three-Level NPC Inverter-Fed Induction Motor Drives

This paper proposes a deadbeat direct torque control strategy that can suppress the fluctuation of the neutralpoint potential (NPP) of the DC bus for the induction motor (IM) system driven by the eight switch three phase inverter (ESTPI). The proposed strategy calculates the torque angle based on the deadbeat control of torque and stator flux, and reference voltage vector is calculated by the discrete stator voltage equation. According to the load current and the NPP, different pairs of small vectors are selected to synthesize a virtual zero vector, thereby implementing NPP control. The proposed control strategy not only achieves the accuracy of torque and stator flux control, but also suppresses the NPP fluctuation. Effectiveness of this method has been validated by simulation results.