一种改进的永磁同步电机直接转矩控制方法

针对传统的永磁同步电机直接转矩控制在低速运行时磁链和转矩脉动大，以及低速时定子电阻的变化导致磁链估算产生较大误差等影响电机稳定运行的问题，提出了一种改进的永磁同步电机直接转矩控制方法。该方法首先利用饱和函数-sat函数代替二阶滑模算法中的符号函数，实现滑模控制切换的连续性，削弱滑模控制中的抖振；然后再利用改进的二阶滑模算法来设计速度和磁链控制器，替代传统的直接转矩中的滞环比较器，抑制转矩和转速的波动；最后通过在磁链估算中建立基于模糊比例积分（proportional integral，PI）控制的定子电阻补偿器，消除定子电阻变化对磁链估算的影响。仿真结果证明了所提方法的有效性与可行性。

An improved direct torque control method for permanent magnet synchronous motor

The traditional permanent magnet synchronous motor direct torque control suffers from the problems of large flux linkage and torque ripple when operating at low speeds. At low speed, the stator resistance changes significantly, resulting in large errors in the flux linkage estimation, which will aggravate this phenomenon. These problems can affect the stability of the motor at low speeds. Therefore, an improved direct torque control method for a permanent magnet synchronous motor is proposed. This method uses the saturation function (sat function) instead of the symbol function in the second-order sliding mode algorithm to achieve the continuity of sliding mode control switching, which decreases the chattering in sliding mode control. Then, the improved second-order sliding mode algorithm is used to design the speed and flux controller-instead of the hysteresis comparator enployed in the traditional direct torque control-in order to suppress the fluctuation of torque and speed. Finally, a fuzzy PI-based stator resistance compensator is in corporated in the flux linkage estimation to eliminate the influence of stator resistance variation on flux linkage estimation. The simulation results demonstrate the effectiveness and feasibility of the proposed method.