Five-level Direct Torque Control with Balancing Strategy of Double Star Induction Machine

Abstract

This work relates to the study of direct torque control of the double star induction machine drive fed by two five-level diode-clamped inverters. The analysis of the three-phase direct torque control shows that this concept can be extended easily to double star induction machine even when it is fed by a multilevel inverter. Diode-clamped inverter, as one of the prominent multilevel inverters, has several advantages like high voltage and low current waveform distortion. However, it suffers from the problem of neutral point potential variation. The variation causes an unbalance in the DC-link voltage levels and increases consequently the current waveform distortion. This problem can be solved in satisfactory way by using multilevel direct torque control equipped by a balancing strategy. The simulation results, illustrating the steady state and dynamic performances, prove the effectiveness of the proposed control approach.