An improved model predictive current control of permanent magnet synchronous motor drives

Model predictive current control (MPCC) is widely recognized as a high performance control strategy of permanent magnet synchronous machine (PMSM) drives due to its quick response and simple principle. However, conventional MPCC relies heavily on the model of system to predict the future behavior of stator currents for each voltage vector. The one minimizing the current error is selected as the best voltage vector. As only one voltage vector is applied during one control period, it fails to give satisfactory performance due to the limited voltage vectors, especially in the case of two-level converters. This paper proposes an improved MPCC strategy for PMSM drives, which firstly estimates the back electromotive force (EMF) based on the past value of stator voltage and currents, and then applies the estimated EMF in the stator current prediction. As a result, the robustness against machine parameter variations is enhanced. Furthermore, to achieve steady state performance improvement, a null vector along with the active vector obtained from conventional MPCC is applied during one control period. Meanwhile, the dynamic response is not affected. Both simulation and experimental results are presented to confirm the effectiveness of the proposed method.