The Research On Variable Structure Sliding Mode For Permanent Magnet Synchronous Motor Direct Torque Control

With the development of science and technology, Permanent magnet synchronous motor (PMSM) more and more respected by the scholars. PMSM has the excellence of compact structure, light weight, high power density compared with the induction motor, etc. Therefore PMSM is widely used in machinofacture, aerospace and electric traction. In recent20years, with the advent of high performance permanent magnet as well as the development of power electronics devices, drive system centering on PMSM is much accounted of at home and abroad. Therefore, study on the design of control system for PMSM has important theoretical and practical significance.First of all, this paper introduces the research status and develops future of PMSM drive system. According to vector coordinate conversion principle, the models of PMSM in the two-phase synchronous rotary coordinate (dqO) are deduced and obtained, and thus the basic control method of permanent magnet synchronous motor are analyzed.Secondly, the study of permanent magnet synchronous motor control system of the traditional principle of direct torque control (DTC), determining the voltage vector selection rules of DTC system. Simulation results show that although the conventional direct torque control has fast torque response, but the flux and torque ripple is relatively large. In order to solve the traditional direct torque control of permanent magnet synchronous motor that exists in a larger flux and torque ripple problem, a new variable structure sliding (VSS) mode control strategy was proposed in this paper.Two hysteresis regulators in the conventional DTC system were substituted by the flux and torque VSS controller respedtively, looking forward to solve the problem of torque and stator flux ripple.At last, the paper gives hardware circuits, soft flow and the experimental wave of the PMSM drive system. Experimental results verified that the proposed control scheme significantly reduces flux and torque ripple, preserves quickly dynamic torque response merit, and shows robust to motor parameter uncertainty, disturbance, which effectively improves dynamic and static operation performance.