Direct Torque Control of Permanent-Magnet Synchronous Machine Drives With a Simple Duty Ratio Regulator

The conventional switching-table-based direct-torque-controlled (DTC) ac machine drive is usually afflicted by large torque ripple, as well as steady-state error of torque. The existing methods, which optimize the duty ratio of the active vector, are usually complicated and parameter dependent. Based on the analysis of instantaneous variation rates of stator flux and torque of each converter output voltage vector, a simple and effective method considering the effect of machine angular velocity is proposed to obtain the duty ratio. The experimental results carried on a dSPACE platform with a laboratory prototype of the permanent-magnet machine verify that the proposed duty-based DTC method can achieve excellent transient response, less torque ripple, and less steady-state error, without resorting to the complicated control method over a wide range of operating regions.