Direct torque control for synchronous reluctance motor
based on space vector modulation

XIE Liang, LIU Si-bei, YAO Wen-xi, LV Zheng-yu

                                                   (School of Electric Engineering, Zhejiang University, Hangzhou 310027, China)

Abstract: Aiming at the problems of large flux and torque ripples and variable switching frequency in conventional direct torque control (DTC) with a pair of hysteresis comparators to control motor stator flux and electromagnetic torque, the direct torque control of synchronous reluctance motor (SynRM) was studied. After the analysis of basic principle of DTC, a kind of direct torque control scheme of a double closed-loop flux and torque PI control under the stator field was presented according to the mathematical model of SynRM. The space vector modulation (SVM) was applied to the DTC. Matlab/Simulink simulation of two direct torque control schemes was established, and the low speed performance of SVM-DTC method was studied based on dSPACE experimental platform. The results indicate that the SVM-DTC method can dramatically decrease the flux and torque ripples with fixed switching frequency compared with the conventional DTC. In addition, the SVM-DTC method can make the motor have good dynamic performance in the low speed range and make the motor run smoothly in the low speed range, which proves the feasibility and effectiveness of the method.
Key words: synchronous reluctance motor (SynRM); direct torque control; space vector modulation; flux and torque ripples; stator flux oriented