永磁同步电机的改进模型预测直接转矩控制

针对永磁同步电机直接转矩控制(DTC)中存在的转矩脉动和磁链纹波大的问题,提出一种改进的模型预测直接转矩控制方法。在两相静止坐标系下,依据无差拍控制理论计算出使电磁转矩和定子磁链在下一周期达到给定值的期望电压矢量。通过引入虚拟电压矢量将电压矢量空间划分成13个扇区,根据期望电压矢量所在扇区位置选取相应的实际电压矢量,可选取的实际电压矢量由传统的8个电压矢量扩展为14个电压矢量。该方法具有虚拟电压矢量占空比固定、调制简单以及运算次数少的优点。对直接转矩控制、传统的模型预测直接转矩控制以及改进的模型预测直接转矩控制进行仿真对比,结果表明,改进的模型预测控制方法能有效地抑制转矩脉动和磁链纹波,减小定子电流畸变率,提高系统的鲁棒性。

Improved model of predictive direct torque control for permanent magnet synchronous motor

In view of the shortcomings of torque ripple and flux ripple in direct torque control(DTC)of permanent magnet synchronous motor,an improved model predictive DTC was proposed.In the two-phase stationary coordinate system,the expected voltage vector which made the electromagnetic torque and stator flux linkage which reach their given value in the next cycle was calculated based on deadbeat control.By introducing virtual voltage vectors,voltage vector space was divided into 13 sections,and the corresponding actual voltage vector was selected according to the position of the sector where the desired voltage vector was located.The selectable voltage vectors were expanded from the conventional 8 voltage vectors to 14 voltage vectors.The proposed method possesses the fixed duty ratio of virtual voltage vector,simple modulation and less operation.Simulation comparisons were carried out for original DTC,traditional model predictive DTC and improved model predictive DTC.The simulation results show that the improved model predictive DTC can effectively suppress torque ripple and flux ripple,significantly reduce stator current distortion rate and improve system robustness.