Robust Closed-loop Torque Control for PMSM of Railway Traction Considering Demagnetization

To improve the torque precision of permanent magnet synchronous motor (PMSM) in railway vehicles, a nonsingular terminal sliding mode observer (NTSMO) is designed to detect permanent-magnet (PM) demagnetization, and a precise torque control method is proposed for the railway PMSM vector control system. First-of-all, the PMSM mathematical model of PM demagnetization is presented. Secondly, a NTSMO is constructed to reconstruction PM flux linkage in d-q reference frame. Meanwhile, the observer stability proof is given. The estimated torque could be calculated according to the estimated PM flux linkage. Finally, the overall system is verified by simulation in Matlab/Simulink. Compared with the sliding mode observer method, the torque control precision of the driving system could be improved, and the driving performance of railway vehicles is fulfilled and guaranteed.