A new direct torque control strategy with improved system performance in the low-speed region

Abstract

Based on the theoretic analysis of performance of the induction motor (IM), the increment of electromagnetic torque of IM is analyzed in detail. this paper explains the reason why the IM performance in the low speed region is poor under conventional direct torque control (DTC). Then one new control strategy of IM is proposed on the basis of classical direct torque control (DTC). The scheme is replacing the single voltage space vector with high frequency voltage pulse when IM runs in the low speed region. By control voltage pulse, a fuzzy neural network direct torque control system based on TMS320F240 is made. The high frequency voltage purls make system's impedance improve obviously. It can effectively reduce the influence of stator resistance in flux linkage. Then, we can avoid facing the tradition stator resistance examining problem. Through duty ratio control technique in high frequency voltage pulse, this scheme can effectively reduce the torque ripple in low speed and static function of the system is improved greatly. The results of the experiment verified the feasibility of the proposed strategy.