Analysis for Unstable Problem of PMSM Current Control System in Overmodulation Range

Unstable problem of PMSM current control system in the overmodulation range of an inverter is a well known problem, however, the cause and mechanism of this problem are still not investigated well. Actually, the main reasons which are large amount of harmonic components and voltage saturation of an inverter in this range are already known. However, the effects from current controller such as PI controller gain and control period are still not considered well. In this paper, we focus on the effects from current controller to this unstable problem. Moreover, we also propose the easy calculation method to predict this unstable phenomena too. Compared with the simulation results, the calculation results from our proposed method match very well.