A Reduced-Switch 3-Level VSI Based Direct Torque Control of PMSM

This paper presents a new scheme for the Direct Torque Control (DTC) of the Permanent Magnet Synchronous Motor (PMSM). DTC method is very popular due to its fast dynamics, low dependence on the machine parameters, and simplicity of its implementation. But the main disadvantage of this method is its high torque ripple. Using conventional 2-level Voltage Source Inverter (VSI) is common in the motor drive systems. These types of converters have 6 active voltage vectors; hence, there are a limited number of vectors to select. On the other hand, using the conventional 3-level VSIs has problems such as its analysis complexity, and, large number of elements and switches. In this paper, a 3-level VSI with fewer number of switches, compared to other 3-level VSIs, is used which has 12 active voltage vectors. By using a 5-level hysteresis controller for the torque control, and a 2-level hysteresis controller for the flux control, alongside a proposed switching table, the direct flux and torque controls are performed. The proposed method reduces the torque ripple and improves the dynamic performance of the control system. The effectiveness of the proposed method is validated with simulations in MATLAB/Simulink environment.