A Two-Degree-of-Freedom Explicit Model Predictive Noncascaded Direct Speed Control for SPMSM Drives

In the noncascaded direct speed (NCDS) control of surface-mounted permanent magnet synchronous motors (SPMSMs), the model predictive (MP) control has attracted considerable attention due to its adeptness in solving multiobjective control problems and handling system state constraint. However, although the existing NCDS control methods based on explicit MP (EMP) control have advantages of strong current constraint capability, low current harmonic contents, and small online calculation burden, its handling of system disturbances is immature. The existing methods will deteriorate the speed's reference tracking performance while enhancing the speed's disturbance suppression performance. To address this issue, this article proposes a two-degree-of-freedom (2DOF) EMP-NCDS control method. The 2DOF control characteristic is demonstrated by analyzing the transfer functions of the closed-loop system. In addition, the system stability is proved by analyzing the distribution of characteristic roots. Compared with existing methods, the proposed method exhibits a 2DOF control characteristic, where the speed's reference tracking performance regulation is independent and not influenced by the disturbance rejection performance regulation. It greatly reduces the complexity of controller parameter tuning and enables swift adjustment to achieve superior dynamic response and disturbance rejection capabilities in speed servo control. Finally, the effectiveness of the proposed method is validated by experimental results.