DTC of three-level inverter fed brushless DC motor drives with torque ripple reduction

Abstract

The paper deals with the synthesis and performance analysis of the direct torque control (DTC) strategy dedicated to three-level NPC inverter (B12) fed brushless DC (BLDC) motor drives. The principle of operation of the BLDC motor fed by the B12-inverter is firstly presented with emphasis on the two-phase conduction mode and the three-phase conduction one. The DTC strategy is treated considering three different schemes, namely: (i) DTCi strategy inspired from the one developed by Takahashi in induction motor drives, (ii) DTC2 strategy that considers a vector selection table simply-reduced to the torque control with a two-phase conduction mode during sectors operation, and (iii) DTC3 strategy that eliminates the torque dips penalizing DTC2 during sector-to-sector commutations by considering the three-phase conduction mode. Simulation results, carried out considering low and high reference motor speeds, proves the high performance exhibited by the proposed DTC3 strategy.