An Enhanced Discrete Virtual Vector-Based Direct Torque Control of PMSM Drives

An enhanced discrete virtual vector- based direct torque control (DTC) strategy is proposed in this article to improve the steady state performance of permanent magnet synchronous motor (PMSM). Discrete virtual vectors are synthesized to extend the candidate voltage vector set, and a universal method is put forward to take advantage of the extended voltage vector set. Three groups of parallel lines, each group perpendicular to one of the A, B, C axes, are carefully designed to divide the internal region of the vector hexagon into several regular subregions, and each subregion has exactly one voltage vector in the center. Conveniently, if the reference voltage vector is located within a certain subregion, the voltage vector located in the corresponding subregion is selected, and the vector selection table is accordingly established. The proposed strategy maintains the simple control structure and good dynamic performance of DTC, and improves the steady state performance by reducing torque ripple and current distortion compared with the existing DTC methods with discrete space vector modulation. Experiments verified the effectiveness of the proposed DTC strategy.