永磁同步电机直接转矩控制中零矢量的作用研究

Study on Null Vector in a Direct Torque Controlled Permanent Magnet Synchronous Motor

通过对永磁同步电机直接转矩控制机理的分析,指出了永磁同步电机与异步电机在实施直接转矩控制上的某些差异,其中零电压矢量的作用有所不同。由于永磁同步电机控制变量中没有转差的概念,电磁转矩变化受控于功角与功角的增量,而零电压矢量对功角增量的作用很弱,因此一般从转矩的动态控制效果认为,零矢量不适合在永磁同步电机直接转矩控制中应用。对此作出了修正,从理论和实验角度证明,零矢量可以参与永磁同步电机转矩的直接控制,在有效抑制转矩和磁链脉动及提高系统性能上有独特的作用。

A deep analysis of the control mechanism for the direct torque control （DTC） of a permanent magnet synchronous motor （PMSM） is carried out in this paper, which pointes out some differences in the implementation of DTC for PMSM and induction motor （IM）, especially the function of null-voltage-vector. Due to the absence of the slip between rotor speed and stator flux speed in a PMSM, the electromagnetic torque is controlled only by the torque angle, which is the angle between stator and rotor flux vectors, and its increment. However the effect of null vector on torque angle increment is very weakly, therefore there is a point of view that the null vector is useless for PMSM DTC. This paper modifies this viewpoint and verifies both from theory and experiment that the null vector possesses unique function in the effectively smoothing torque and flux ripples and improving static performances of the DTC system.