Direct Torque Control of Permanent Magnet Synchronous Motors

Direct Torque Control (DTC) for Permanent Magnet Synchronous Motors (PMSM) is a widely adopted control strategy in high-performance drive applications, particularly suitable for scenarios requiring fast dynamic response. Unlike traditional Field-Oriented Control (FOC), DTC directly regulates motor torque and flux linkage, eliminating complex coordinate transformations and modulation processes, thereby simplifying system architecture.

The fundamental principle of DTC involves detecting the stator flux linkage and torque of the motor, comparing them with reference values, and utilizing hysteresis controllers and switching tables to directly select the inverter's switching states. This control approach enables rapid torque response but may introduce significant torque ripples due to its reliance on hysteresis control, affecting low-speed performance.

During the initial learning phase, understanding DTC's core concepts is crucial: Flux and Torque Estimation: Calculate flux linkage using voltage and current models, and estimate torque based on the interaction between flux and current. Hysteresis Control: Employ flux and torque hysteresis comparators to determine whether switching states need adjustment to maintain target values. Switching Table Selection: Based on flux position and hysteresis outputs, select optimal voltage vectors from predefined switching tables.

While DTC offers advantages such as simple structure and fast response, it also has limitations including torque ripple and parameter dependency. Further study can integrate modern control methods like Model Predictive Control (MPC) or Sliding Mode Control (SMC) to optimize performance and reduce pulsations.