Simplified models to calculate the change of stator flux and torque of permanent magnet synchronous motor (PMSM) on stator flux coordinate system are proposed. In order to solve high torque ripples of PMSM direct torque control (DTC) system, dead-beat (DB) control of stator flux and torque is proposed. The calculation of ideal voltage vector (VV) for the DB control of stator flux and torque using simplified models are given, and a simplified VV selecting method is used to implement the DB control. In order to improve control performances, a novel way to expand VVs based on both angle and amplitude is proposed. The angle and amplitude of ideal VV are used to determine the angle and amplitude of output VV and the look-up table is used to generate output VVs. Simulation results show this novel method can decrease stator flux and torque ripples dramatically, but increase switching frequency.
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