A Variable Duty Cycle-Based Predictive Control for PMSM Fed by Cascaded H-Bridge Inverter

In the permanent magnet synchronous motor (PMSM) drive system fed by a cascaded H-bridge (CHB) inverter, the dc voltage unbalance of CHB inverter will severely deteriorate the performance of PMSM. Aiming at this problem, a variable duty-cycle-based predictive control strategy suitable for any level CHB inverter is proposed in this article. Under the condition of unbalanced voltage, the duty cycles obtained by the predictive control are revised according to the feedback of dc-link voltage of each cell. Besides, the duty-cycle failure caused by the excessive dc voltage unbalance is solved by the duty-cycle transition. Thereby, the dc source of each cell can be fully utilized, and the steady-state performance of PMSM is improved under unbalanced conditions. In addition, the H-bridge cells in each phase are selected and arranged according to the power deviation coefficient of each cell, so as to realize the effective power control under unbalanced conditions. Finally, the practicability and validity of the proposed method are verified by simulation and experiment.