In the double-vector-based model predictive torque control (MPTC), two voltage vectors are applied in one control period. Due to a large number of possible combinations among voltage vectors, the determination of optimal voltage vector pair is often complicated. This article proposes a new approach to reduce the number of candidate active voltage vectors. The concept is to preselect the active voltage vectors according to the stator flux vector error. The proposed MPTC is implemented in a stationary frame and avoids the complicated coordinate transformation as well as the tangent inverse calculations. Furthermore, a promising approach is conceived for calculating the duty cycle of active voltage vector, which can contribute to the less dependence on the system model, thus alleviating the sensitivity to motor parameter variations. To further improve the steady-state performance, a modified three-vector-based MPTC is newly put forward. Meanwhile, the proposed duty cycle calculation method is used to achieve the deadbeat control of torque and stator flux. Theoretical analyses and experimental results are given to verify the effectiveness of the proposed MPTC methods.

In conventional model predictive torque control (MPTC), only one voltage vector (VV) is applied during a whole control period, thus causing a large torque ripple. To improve the steady-state performance, some two-vector-based control schemes have been proposed. However, the selection of the optimal VV pair is complex as well as has a large computational burden, and the improvement of performance is still limited by the direction and amplitude of the output VV. This article proposes a low-complexity three-vector-based MPTC for SPMSM drives, which can precisely determine the appropriate active voltage vectors (AVVs) with the predicted torque error. Then, a modified switching table is developed to directly select the AVVs, thus greatly reducing the complexity and computational burden of the algorithm. To obtain a better steady-state performance, a duty cycle calculation method based on torque and stator flux difference parameters is newly proposed to achieve the deadbeat control of torque and stator flux. And then, the experimental comparisons with the double-vector-based MPTC are conducted. The results show that the proposed MPTC can effectively reduce the steady-state torque ripple while maintaining a good dynamic performance as well as almost a fixed switching frequency for all speed ranges.

This paper proposes a novel hybrid-excitation flux-switching (HEFS) machine with axial partitioned stator (APS) arrangement, which can achieve the independent accommodation of armature winding and field-excitation winding, thus enhancing the field-excitation capability and improving the winding heat dissipation. More importantly, a particular parallel-magnetic-circuit (PMC) hybrid-excitation pattern consisting of the axial and radial magnetic paths is innovatively developed in the HEFS machine, which is an effective solution for improving the flux-regulation ability. Consequently, the PMC-based flux-regulation principle is comprehensively illustrated. Moreover, by investigating the flux-regulation characteristics of three structural feasible APS-HEFS topologies, the bilateral complementary structure is finally determined as the preferred option. By using the multi-objective optimization method and the three-dimensional finite element analysis (3D-FEA), the dimensional parameter optimization design of the proposed machine is conducted, and the performance comparison with a conventional HEFS counterparts is also carried out to prove the flux-regulation superiority of the proposed design. Finally, a prototype is fabricated for experimental testing, and the measured results are in good agreement with the FEA, which verifies the validity of the proposed APS-HEFS topology and its theoretical flux-regulation principle analysis.

This article presents a novel magnetic-geared direct-drive machine (MGDM) with V-shaped permanent magnets (PMs) installed on its rotor. By extending the inner rotor shaft and connecting it to a prime motor, the torque and power density of the proposed MGDM are boosted. In addition, compared with the conventional MGDM with surface-mounted PMs (SPMs), the proposed MGDM with V-shaped PMs has a more robust rotor structure to cope with extreme operating conditions. The operating principle and structure requirement of this MGDM are first derived. Then, the geometrical parameters are optimized via a three-stage multiobjective optimization method to maximize output torque and efficiency and minimize torque ripple via the genetic algorithm (GA) and finite element analysis (FEA) combined optimization strategy. Furthermore, the proposed MGDM is artfully integrated into hybrid electric ships (HESs) to construct an onboard integrated power system (OB-IPS). Since the proposed system possesses various operating modes to cope with practical operating conditions, it enjoys a high systematic efficiency and good dynamic performance. Finally, a prototype is fabricated and tested with various operating modes by referring to the practical navigation cycle of an HES. The experimental results validate the feasibility of the proposed MGDM for being applied in HESs.

Along with the establishment of general air-gap field modulation theory, a new type of field-modulation machine has attracted increasing attention. However, the low power factor always plagued its popularization. This article is to focus on the simplest structure surface-mounted permanent-magnet field-modulation (SMPMFM) machine, aiming at exploring the implementation of the high-power-factor design. The key is that the power factor calculation formula is derived parametrically; hence, the originally vague causal relationship between the structural parameters and power factor becomes clear, guided by which the initial structure design for high-power-factor achievement is determined. Meanwhile, the power factor adjustment evaluation and the electromagnetic performance comparison, with the help of finite-element analysis (FEA), are conducted to verify the validity of the proposed power factor calculation formula. Finally, a feasible high-power-factor SMPMFM prototype is fabricated, and the experimental testing is performed, which shows good agreement with the formula calculation and FEA results. Hence, the validity of the proposed analysis for achieving a high-power-factor design of field-modulation machines is verified.

According to air-gap field-modulation theory, multiple field harmonics are responsible for high torque density of field modulation (FM) motors. However, abundant field harmonics will undoubtedly increase motor losses, especially iron loss and PM eddy-current loss. Therefore, a harmonic-analysis-based loss minimization (HLM) method incorporated into model predictive torque control (MPTC) for efficiency improvement of FM motors is proposed in this article. First, by analyzing the loss generation mechanism, a harmonic-based online loss calculation model is built to serve for loss minimization control. Then, the reference flux for MPTC can be derived from the proposed HLM method, which avoids complexity of equivalent resistance tuning and improves accuracy of loss calculation compared to the conventional model-based loss minimization method which lacks attention on the harmonic-based loss analysis. Consequently, the HLM-MPTC strategy is finally determined and then applied in a flux-concentrating field-modulation permanent-magnet prototype to verify its validity. The experimental results evidence that the proposed HLM-MPTC can effectively achieve loss reduction and efficiency improvement.