THE Direct Torque Control of PMSM with Dynamic Torque Hysteresis Based on Three-Level Direct Matrix Converter

When direct torque control (DTC) is applied to matrix converter (MC)-fed permanent synchronous motor (PMSM) system, the conventional DTC scheme is hard to satisfy the proper performance because of the flux linkage distortion which occurs around the stator flux linkage circle sector boundary. In this paper, a method of dynamic torque hysteresis comparator based on three-level direct matrix converter (TLDMC)-fed PMSM is proposed to improve the performance of PMSM system. First, the traditional MC-DTC strategy and the mathematical model of PMSM are analyzed. Based on the unbalanced stator flux linkage in low speed condition, a remedial strategy of dynamic torque hysteresis is proposed. Then, in order to reduce the electromagnetic torque ripple and common-mode voltage, the proposed method is applied in the system of the three-level direct matrix converter, and a new switching table is derived. Finally, the proposed method has been compared with the traditional MC-DTC method. The simulation and experimental results verify that the proposed method greatly improves the performance of flux linkage and electromagnetic torque.