Improved Direct Torque Control of PMSM Drive Strategy Based on Discrete Virtual Vectors

This article proposes an improved direct torque control (DTC) strategy based on discrete virtual vectors to improve the steady-state performance of permanent magnet synchronous motors (PMSM). The effective area of action of the voltage vector is segmented into an average of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$6N^{2}$</tex> subregions by three sets of parallel lines corresponding to the A, B, and C axes, then extend the set of vectors by adding a virtual vector to each sub-region, the newly added voltage vectors are positioned at the midpoint of each subregion. When the reference voltage vector falls within a specific subregion, the corresponding voltage vector within that area is selected, and a vector selection table is subsequently established. This proposed control strategy, in contrast to conventional DTC methods, improves the steady-state performance by expanding the vectors to mitigate torque ripple and current distortion, while retaining the advantages of traditional DTC in terms of structure and dynamic performance.