This paper proposes a simple control method for improving direct torque control with a constant switching frequency torque
controller (CSFTC-DTC) in induction machine fed by three-level neutral-point clamped (TL-NPC) inverter. The conventional CSFTC-
DTC was initially introduced to minimize torque ripple and fix the switching frequency in TL-NPC inverter. However, the conventional
CSFTC-DTC algorithm suffers from flux droop when the motor operates at low speed, which leads to undesirable current distortions.
This paper improves the CSFTC to minimize the flux droop by adding carrier for low speed operation and maintaining the simple
single-carrier for high speed operation. Simulation results are provided to validate the effectiveness of proposed methods.