Optimal Transition from Conventional to Model Free Predictive Control for Permanent Magnet Synchronous Motors

In voltage-current slope look-up table-based model free predictive control (MFPC) method, the dq-axis current difference resulted from different voltage vectors are needed to be stored in a look-up table. Therefore, this method is incapable of direct startup of the electric machine, such as the permanent magnet synchronous motor (PMSM). One solution is to use the conventional PI controller during PMSM startup, and then the control approach can be switched to MFPC mode. This study is an effort to optimally perform this transition by applying two candidate voltage vectors in two subsequent control periods to ensure a minimal deviation from the reference voltage. It is shown that zero average deviation from the reference voltage is achievable only in limited zones. For the remaining zones, optimal duty cycles resulting in minimal deviations are mathematically developed. Simulation results are provided to confirm the efficacy of the proposed method.