A new approach to direct torque control strategy with minimization torque pulsations in permanent magnets synchronous machines

In this paper, we present a new approach to direct torque control (DTC) with minimization torque pulsations in permanent magnet synchronous machines (PMSM). The synchronous machine torque control, based on the DTC structure, permits to obtained high dynamic performances. In classical DTC, due to the hysteresis based scheme, the switching frequency is variable, current distortion and torque ripple are more important. Moreover high sampling frequency is needed for digital implementation. In order to obtain a constant switching frequency and hence torque ripple minimization, we introduces a new control technique for PMSM. It consists of controlling directly the electromagnetic torque by using a modulated hysteresis controller. The improvements obtained are principally a constant switching frequency in the inverter and an important reduction of the torque ripple. A digital-signal-processor (DSP) based controller is used to study the application of direct torque control method for PMSM. The implementation in a test bench shows the effectiveness of this control. Results obtained by simulation and experimental tests of this strategy are presented.