Research On DSP-based Direct Torque Control Strategy For Permanent Magnet Synchronous Motor Drives

The direct torque control (DTC) is a high qualified control strategy for AC motor besides vector control. It was proposed in 1980s aimed at controlling the asynchronous motor. With the development of DTC control theory and the establishment of its fundamental theory in permanent magnet synchronous motor (PMSM), DTC strategy of PMSM has drawn considerable attention. This paper is also concerned with the DTC control theory, and some improvement has been made.Based on the PMSM mathematical model, the discussion of fundamental theory in DTC of PMSM is addressed. After that the classical DTC switch state lookup table is derived. On the basis of theoretic analysis, the improvement of classical DTC switch state lookup table has been made, in which the zero vector is introduced into the control strategy. Though the zero vector can't decrease the electromagnetic torque, it can keep the torque remain and reduce the switching frequency, which will improve the system performance.In this paper, the fuzzy rules are derived into the control strategy. According to the feature of hysteresis of DTC that the hysteresis width is fuzzy itself, it can be fuzzified and the repository can be organized classically to complete the choice of space voltage vector.