This paper proposes a novel hybrid-magnetic-circuit variable flux memory machine (HMC-VFMM) by combining series and parallel hybrid magnet structures. Thus, the synergies of wide flux regulation range in parallel type and excellent on-load demagnetization withstand capability in series type can be simultaneously obtained with the proposed HMC design. Meanwhile, two sets of the permanent magnets (PMs) with high coercive force (HCF) and low coercive force (LCF), i.e. NdFeB and AlNiCo PMs, are employed to achieve high torque density and energy-efficient magnetization state (MS) adjustment. The topologies and tradeoffs of traditional parallel and series VFMMs are addressed first. In addition, the structure evolution, features and operating principle of the proposed HMC-VFMM are described, respectively. A simplified equivalent magnetic circuit is modelled to reveal the performance improvement of the machine. Then, the design improvements with q-axis barriers are presented to elevate the LCF PM working point for preventing the on-load demagnetizing effect, while maintaining the torque capability. The electromagnetic characteristics of the HMC design are investigated and compared with the parallel/series counterparts. Finally, the experiments have been carried out to validate the finite element (FE) analyses.

Model predictive control (MPC) has attracted a lot of attention for power converters and motor drives in the last decade, owing to its merits such as explicit concept, excellent dynamic performance, and decent applicability in digital implementation. However, as a model-based method, classical MPC is heavily dependent on the system parameters of the plant under control. In this article, a novel finite-set sliding-mode model-free predictive current control (FS-SM-MFPCC) is proposed for permanent magnet synchronous machine (PMSM) drives, which combines the theory of sliding-mode control with MPC. The proposed strategy is thoroughly model-free, irrelevant for the dc-link voltage, and computationally light. The original version of the suggested strategy suffers from two flaws: 1) poor steady-state performance and 2) existent tracking errors, which are solved by using a simple correction algorithm and an extended control set coordinating with an improved cost function, respectively. The comparatively experimental results based on a 500-W PMSM drive are given to confirm the benefits of the proposed strategy.

This paper proposes a finite control set model predictive torque control (FCS-MPTC) with reduced computation burden for permanent magnet synchronous motor (PMSM). Based on discrete space vector modulation (DSVM), the proposed DSVM-MPTC extends the control set. Therefore, compared to the traditional FCS-MPTC, it greatly reduces the torque ripples and current harmonics while maintaining a constant switching frequency. Furthermore, a new voltage vector optimization strategy is employed to decrease the number of candidate voltage vectors from 38 to 13, the proposed DSVM-MPTC significantly reduces the computation burden without compromising the control performance. The validity of the proposed DSVM-MPTC is verified by comparative experiments.