A new switching algorithm for voltage balancing of a three-level NPC in DTC drive of a three-phase IM

In this paper, a new switching-table-based direct torque control (DTC) drive algorithm is proposed for the three-level neutral point clamped (NPC) inverter. The effect of converter switching states on the neutral point voltage is reviewed and then a new, simple and effective switching algorithm for controlling a three-phase induction motor using DTC is developed. In addition to simple implementation, the proposed algorithm is capable of restricting voltage deviation of the DC link capacitors in an acceptable range resulting in DC link voltage balancing. Simulation and experimental results demonstrating the effectiveness of the proposed method in controlling the neutral point voltage are provided. The proposed algorithm may lead to reduction of the size of the bulky dc link capacitors as well.