Abstract: To improve the performance of the torque precision for PMSM（Permanent Magnet Synchronous Motor） of railway vehicles, a novel sliding mode observer of active flux and a precise torque control method are proposed for a vector control system of PMSM. The concept of active flux is adopted and the mathematical model of Interior Permanent Magnet Synchronous Motor（IPMSM） has been established. The sliding mode observer of active flux is constructed in [α-β] stator coordinate frame, and it is observed active flux by applying sliding mode equivalent control methodology, then it realizes the real-time estimation of torque. The precise torque closed-loop control system is constituted combining with the torque command. The simulation results verify the feasibility and effectiveness of the method. The torque control precision of the PMSM can be improved, and the driving performance of railway PMSM vehicles is fulfilled and guaranteed. This method is not only applicable to IPMSM but to Surface-mounted Permanent Magnet Synchronous Motors（SPMSM） as well.

Key words: Permanent Magnet Synchronous Motor（PMSM）, sliding mode observer, active flux, torque closed-loop control

摘要： 为了改善轨道交通永磁同步电动机转矩控制的性能，提出了一种改进的有效磁链滑模观测器，实现了永磁同步电动机的精确转矩闭环控制。采用有效磁链的概念，建立了基于有效磁链的内置式永磁同步电机数学模型；在[α-β]静止坐标系建立了有效磁链的滑模观测器，并基于滑模等值控制方法实现了有效磁链的观测，进而进行转矩的实时估算，以此和转矩给定值形成精确转矩闭环控制。通过仿真验证该方法的可行性和有效性。结果表明提高永磁同步电动机的转矩控制精度，改善了轨道永磁同步电动机控制系统的性能。该方法不仅适用于内置式永磁同步电机，而且适用于表贴式永磁同步电机。

关键词: 永磁同步电动机, 滑模观测器, 有效磁链, 转矩闭环控制