A three level NPC inverter with neutral point voltage balancing for induction motors Direct Torque Control

In this paper, we present a new Direct Torque Control (DTC) scheme for induction motors using a three-level neutral point clamped (NPC) voltage source inverter (VSI). In order to develop high dynamic performances, we propose a new approach, in which we enhance the responses of the torque and the flux with optimal switching strategies. Serious problems caused by significant fluctuations in the middle point of the three-level inverter. As consequence to these problems, we obtain an asymmetric inverter output voltage with a non-zero average value. Our proposed solution uses a hysteresis comparator to regulate the input voltages of the three-level NPC inverter. An enhanced direct torque control “EDTC” scheme is simulated with DC voltage source balancing for an induction motor. Our obtained results demonstrate high dynamic and stability performances.