This paper presents an optimal design methodology of a dual-mechanical-port bidirectional flux-modulated machine for electric continuously variable transmission in hybrid electrical vehicles. The machine utilizes bidirectional flux modulation effect to combine two rotors and one stator together, aiming to realize electrical and mechanical power flexible split and combination. Due to the complexity of the machine structure, conventional optimization methods using analytical model are inapplicable. Therefore, an effective and practical method that combines the genetic algorithm and finite-element method (GA-FEM) is proposed to optimize the design of the machine in this paper. Since the computational cost increases exponentially with the increasing of number of design parameters, to reduce the computational cost in the optimization process, the design parameters are divided into two levels basing on a sensitivity analysis. And, then, the sensitive parameters are optimized using the GA-FEM coupled method. Finally, a prototype is fabricated to verify the effectiveness of the optimal design.

A rotor retaining sleeve is usually essential in high-speed permanent magnet (PM) motors to firmly retain the magnets and ensure the rotor integrity. The structure and material of retaining sleeve have a significant effect on rotor losses, especially on the rotor eddy current loss. On the other hand, heat dissipation from the rotor is difficult, therefore, any excessive rotor loss may lead to over temperature and cause irreversible demagnetization of the magnets. In this paper, the influence of retaining sleeve with different structures and materials on the rotor eddy current loss in high-speed PM motors will be comprehensively investigated, with both 3-D finite element method (FEM) simulations and experiments. Particularly, the proposed experiments are carried out with a stationary rotor. The study reveals that the equivalent conductivity of the retaining sleeve has a significant influence on the rotor eddy current loss, and countermeasures can be made accordingly so as to reduce the rotor eddy current loss.

This paper proposes a modified model-free predictive current control (M-MFPCC) integrated with a modified extended state observer (MESO). The goal is to reduce torque ripple and improving current distortion caused by inverter nonlinearity and other system disturbances. The disturbances are precisely observed with unity gain and zero phase delay. Adaptive gain updating of the proposed observer is implemented to track the frequency of the disturbance and sustain the noise suppression performance under various operating conditions. The proposed M-MFPCC can eliminate the high frequency harmonic disturbances without requiring additional information about inverter nonlinearity or necessitating extra parameter tuning. Experimental results confirm the proposed method's efficacy in suppressing current Total Harmonic Distortion (THD) and torque ripple under a variety of load conditions.

Dual permanent magnet (PM) machines have attracted numerous interests due to the high torque density and compact volume . This article investigates a synergistic PM machines with the synergies of flux switching and flux reversal effects. The flux-reversal and flux-switching PM (FSPM) flux paths circulate from two sides of the split teeth separately, which avoid the over-saturation with dual PM excitations. The preferred stator and rotor pole number is derived from a simplified analytical model and the influence of leading parameters is analyzed as design guidelines. Furthermore, the synergistic stator PM machine is optimized and compared with FSPM machines. It is revealed that the synergistic stator PM machine exhibits ∼20%, ∼10%, and ∼17% higher torque density than conventional FSPM machine, C-core FSPM machine, and E-core FSPM machine, respectively. Besides, good flux weakening capability is achieved with a larger inductance than conventional FSPM machine, and higher efficiency is obtained at both low-speed and high-speed operations. Finally, an experimental prototype is fabricated to validate the proposed concepts.

The most common method to suppress electromagnetic vibration is to weaken the electromagnetic force harmonics, which are the vibration sources. Clearly, vibration is related to some other factors, too. Therefore, in this article, a modal analytical model and the transmission function of a permanent magnet synchronous motor are studied, based on which a fast analytical method of predicting the electromagnetic vibration is proposed, so that the vibration can be preliminarily evaluated during the machine electromagnetic design. The time-consuming 3-D finite-element method is not needed when predicting the vibration. Moreover, using the fast prediction method, a 15-D multiobjective optimization problem for vibration, torque, and efficiency performances is solved in stages. After optimization, the vibration is greatly reduced, and the torque performance is improved. The proposed methods are also proved to be applicable for different operating conditions and types of motors with various slot–pole combinations.

A novel bidirectional flux-modulation permanent magnet (BFMPM) machine for stand-alone dc wind power generation is proposed in this paper. The key is to control the inner rotor position with a small servo motor, and with the bidirectional flux-modulation effect, the resultant induced voltages in two sets of stator windings can be adjusted accordingly. Consequently, in a wide wind speed range, the various-speed constant-amplitude-voltage operation is realized. The novel structure has two major merits. First, it has high reliability without the maintenance problems caused by mechanical gearboxes, slip ring assembly, and brushes. Second, the proposed system requires a low-cost uncontrolled diode rectifier, which enhances the reliability and reduces the cost of the system. The analytical model and operation principle of the BFMPM machine are illustrated and the simulation results using a finite-element method is presented. A prototype is optimized and fabricated. The experimental results agree well with the simulation results and verify the correctness of the analytical model and the effectiveness of the proposed structure. Therefore, the novel structure offers a potential solution to provide a stable dc power for the standalone condition, such as remote area and offshore island.